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Grand-canonical (GC) constant-potential methods within an implicit solvent environment provide a general approach to compute the potential-dependent energetics at electrified solid–liquid interfaces with first-principles density-functional theory. Here, we use a mindfully chosen set of 27 isostructural 2D metal halides MX2 to analyze the variation of this energetics when the electronic structure changes from metallic to semiconducting and insulating state. Apart from expectable changes due to the opening up of the electronic bandgap, the calculations also show an increasing sensitivity to the numerical Brillouin zone integration and electronic smearing, which imposes computational burdens in practice. We rationalize these findings within the picture of the total interfacial capacitance arising from a series connection of the electrochemical double-layer capacitance and the so-called quantum capacitance resulting from the filling of electronic states inside the electrode. For metals, the electrochemical double-layer capacitance dominates at all potentials, and the entire potential drop takes place in the electrolyte. For semiconductors, the potential drop occurs instead fully or partially inside the electrode at potentials within or just outside the bandgap. For 2D semiconductors, the increased sensitivity to numerical parameters then results from the concomitantly increased contribution of the quantum capacitance that is harder to converge. Fortunately, this understanding motivates a simple extension of the CHE + DL approximation for metals, which provides the approximate GC energetics of 2D semiconductors using only quantities that can be obtained from computationally undemanding calculations at the point of zero charge and a generic double-layer capacitance. [ABSTRACT FROM AUTHOR]

A new adsorbent, starch grafted polyacrylic acid copolymer with polyacrylamide (SG@AA-co-AM), was synthesized using free radical polymerization techniques. Proton nuclear magnetic resonance (1H NMR), Fourier-transform infrared spectrophotometry (FTIR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), particle size distribution (PSD), and fluorescent electron microscopy (FEM) were employed to elucidate the structure, crystalline nature, thermal stability, and surface morphology of SG@AA-co-AM. SG@AA-co-AM was utilized as an adsorbent for the removal of Victoria green B (VGB) dye from wastewater. SG@AA-co-AM exhibited a removal percentage (% R) of 97.6% towards VGB under optimized conditions: a contact time of 30 min, temperature of 25 °C, adsorbent dose of 20 mg, pH of 8, concentration of dye solution of 20 ppm, and volume of dye solution of 30 mL. The point of zero charge (PZC) for SG@AA-co-AM was determined to be 5.2. Nonlinear pseudo-second-order (PSO) and Langmuir adsorption isotherm models best fitted to the experimental data, with regression coefficients (R2) of 0.95 and 0.99, respectively. The results confirmed the chemi-sorption and monolayer adsorption of VGB onto SG@AA-co-AM. Thermodynamic studies revealed that the adsorption of VGB onto SG@AA-co-AM is endothermic and spontaneous. Furthermore, the regeneration experiment showed a decline of 3.9% after five cycles, confirming the economical and reusable nature of SG@AA-co-AM. [ABSTRACT FROM AUTHOR]

In the present study, a quaternary composite consisting of α-ketoglutaric acid, chitosan, polyaniline, and graphene oxide (α-CTS-PANI-GO) was synthesized and characterized by Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy, and Raman spectroscopy. The adsorption of dye on the film was proved by the X-ray diffraction analysis method. According to the increase in the intensity of the peak before and after adsorption, it showed the presence of Methylene Blue (MB) and Acid Orange 7 (AO7). Also, the appearance of peaks related to sulfur in Energy dispersive X-ray (EDX) and EDX elemental mapping, and X-ray photoelectron spectroscopy data after the adsorption process proved the presence of dyes compounds and their adsorption by the synthetic film. The simultaneous removal properties of α-CTS-PANI-GO were evaluated in the removal of cationic and anionic dyes, MB and AO7. Using the Central Composite Decomposition, the effect of different variables such as pH, temperature, adsorbent dose, and time on AO7 and MB removal was studied. The regeneration of α-CTS-PANI-GO film was studied and the zero point charge of the synthesized film was also determined. Various isotherm models, such as Langmuir and Freundlich, were investigated, and the processing of experimental equilibrium data confirmed the suitability and application of the Langmuir model. Analysis of experimental adsorption data using various kinetic models, such as pseudo-first and second-order models, shows the applicability of the first-order equation. The results showed that in the optimal conditions, the removal percentage was about 95% for AO7 and 80% for MB, which indicates the successful performance of the synthetic film compared to the method. [ABSTRACT FROM AUTHOR]

Potentially toxic metals in water threaten humans, animals, and the environment. The potential of Indian willow (Salix tetrasperma) leaves to biosorb copper and lead from water was examined. Utilising scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and Fourier transform infrared spectroscopy (FTIR) spectrum analysis, the properties of Salix tetrasperma biomass (STB) was investigated. The maximum removal percentage (92.8% for copper and 89.9% for lead) was achieved at pH 5.0, a biosorbent dosage of 3.0 g/L at 25°C, and a 10 mg/L initial concentration of copper and lead. The determination of the point zero charge (pHzpc = 5.0) indicated the prevalence of a negative charge on the surface of the biosorbents. The kinetic equation utilised in the pseudo-second-order model effectively. Langmuir isotherm better described experimented data than the Freundlich model. The Dubinin-Radushkevich isotherm provided a good fit for the study's equilibrium data. STB recorded an adsorption capacity, Qmax, of 43.99 mg/g for copper (II) and 39.66 mg/g for lead (II) ions at an optimum pH of 5. Thermodynamically, the biosorption of both ions on STB was spontaneous, endothermic, and feasible. The selected modified STB was found to be suitable for adsorbing copper (II) and lead (II) metal ions. [ABSTRACT FROM AUTHOR]

Abstract\nNOVELTY STATEMENTThe peel of Hylocereus undatus was employed in the preparation of biochar and firstly applied for tetracycline removal from aqueous solution. Based on different characterization techniques, the material was found to possess a variety of surface functional groups on a porous structure and a pH point of zero charge (pHpzc) of 9.3. Adsorption of tetracycline (TC) was conducted under varying conditions, revealing significant effects of carbonization temperature, solution pH, adsorbent dose, ionic strength, contact time and initial concentration of TC on the biochar adsorption capacity. Kinetic data on TC adsorption were best described using the Elovich kinetic model, with an initial adsorption rate of 167.3 mg g−1 min−1. Isotherm data on adsorption of the desired biochar showed the best fit with the Temkin isotherm model, followed by the Langmuir model, displaying maximum adsorption capacity at 12.4 mg g−1. The electrostatic interactions between the charged biochar surfaces and certain fractions of TC were proposed as the major mechanism, together with H-bonding, pore-filling effect and π–π interaction. This study demonstrates great potential of H. undatus peel as a starting material to prepare an effective and reusable adsorbent in the removal of TC.Literature is available on a large number of plant-based biochar adsorbents for the removal of antibiotics. However, to the best of our knowledge, no report has been published on applying biochar derived from Hylocereus undatus peel for antibiotics removal. This type of fruit peel is available in massive amounts in Vietnam and is considered as an agricultural solid waste. Therefore, to fill the gap in the literature and to converse this leftover waste into a value-added byproduct, we chose this study to prepare H. undatus peel-derived biochar for the elimination of TC in an aqueous solution. [ABSTRACT FROM AUTHOR]

Water pollution is a major environmental concern worldwide, particularly due to industrial paint waste. Therefore, treating wastewater from various industrial sources is crucial to restoring environmental quality. In this study, a batch biosorption system was used to investigate the biosorption of Rhodamine B (RhB), a highly toxic dye, on Teucrium polium seeds (TPS). The study examined the effects of different parameters such as initial dye concentration, contact time, initial pH, temperature, and biosorbent amount on RhB removal. To determine the physicochemical properties of TPS, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and zero charge point (PZC) characterization analyses were performed. The maximum biosorption capacity of TPS at pH = 5.5 and 25 °C was found to be 4.18 mg g−1. The study found that the removal rate of RhB was 93.3% at an initial RhB dye concentration of 200 mg L−1. The experimental data showed that the Langmuir isotherm model (R2 = 0.940) was the most compatible model for biosorption, while the biosorption kinetic mechanism proceeded through the pseudo-second-order (PSO) kinetic model (R2 = 0.925). Additionally, the study found that intraparticle diffusion, pore diffusion, and film diffusion were effective in the RhB biosorption rate mechanism. Thermodynamic studies revealed that the biosorption was endothermic (ΔH0>0), spontaneous (ΔS0>0), and entropy-increasing (ΔG0 <0). As a result, TPS, which has suitable adsorbent properties for RhB, can be recommended as a new, cost-effective, abundant potential biosorbent. [ABSTRACT FROM AUTHOR]

Silica is a frequently used material for removing organic contaminants, dyes, and metal ions from wastewater due to its large specific surface area and ease of preparation at various porosities. In a wide range of pH values, a negative charge is created on its surface as a result of the deprotonation of silanols, which causes its strong adsorption properties in alkaline media. It is found that a composite material consisting of mesoporous silica with iron oxide nanoparticles, which have a point of zero charge (PZC) much larger than silica, can exhibit strong adsorption properties in acidic media as well. This is confirmed by the analysis of the Zeta potential and a significant increase in the adsorption of methylene blue by modified silica at pH values of 4 and above. It is also showed that the microscopic mechanism underlying this behavior relies on the coexistence of two length scales: the Debye shielding range for Coulombic interactions and the average pore size where the iron oxide nanoparticles are synthesized. [ABSTRACT FROM AUTHOR]

This study presents an innovative double‐walled borosilicate glass reactor system for the efficient treatment of liquid and gaseous wastewater. This reactor system allows precise temperature control, continuous pH monitoring, and controlled dosing of reagents to optimize reaction conditions. Detailed characterization was carried out by X‐ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), BET (specific surface area) analysis, point of zero charge (PZC), and scanning electron microscopy (SEM) for the SCR, SCRT, and 5%Fe@SCRT materials. For Malachite Green adsorption, SRCT demonstrated a maximum adsorption capacity of 39.78 ± 0.5 mg/g using the Langmuir isotherm model and followed pseudo‐second‐order kinetics. Optimum conditions for adsorption were found to be: an initial concentration of 50 ppm, an adsorbent dosage of 1 g/l, a pH of 8.5, and a temperature of 50°C. For the catalytic oxidation of phenol, 5%Fe@SRCT achieved a remarkable removal rate of 99.9 ± 0.1% under optimum conditions (50 ppm phenol, 1 g/l catalyst dosage, pH 3.5, H2O2 concentration 8.7 mM, and temperature 70°C). Intermediates identified during the reaction included hydroquinone, benzoquinone, catechol, and resorcinol, with degradation occurring over a 60‐minute reaction period. The 5%Fe@SCRT material showed excellent reusability in the removal of phenol by catalytic oxidation, with no significant loss of efficiency over three cycles, while the SRCT underwent three cycles of regeneration for the adsorption of Malachite Green. Scavenger tests confirmed the involvement of hydroxyl radicals in the catalytic oxidation process. In addition, fish survival tests after catalytic oxidation of phenol by 5%Fe@SRCT showed no impact on fish, underlining the environmental safety of this process. In addition, germination tests after decolorization of MG by SRCT demonstrated a good effect with no negative impact, reinforcing the ecological value of this innovative technology. These results highlight the innovative use of SCRT and 5%Fe@SCRT as versatile materials for environmental remediation, exploiting their effective adsorption capacities and efficient catalytic oxidation performance within the proposed double‐walled borosilicate glass reactor system. Practitioner Points: The study demonstrates the effectiveness of an innovative reactor system employing SRCT adsorbent and Fe@SRCT catalyst for efficient removal of malachite green and phenol from wastewater.Environmental impact assessment, including seed germination and fish survival evaluation, validates the method's eco‐friendly potential.Implementation of this approach could significantly contribute to sustainable water treatment practices. [ABSTRACT FROM AUTHOR]

The behavior of praseodymium in a forest soil with different quantities of organic matter was investigated. The forest soil (FS) was treated with acid and alkali solutions to separate the soluble organic matter (fulvic and humic acids) (IM-FS), and then IM-FS was treated with hydrogen peroxide (IM-FS(b)). The materials (FS, IM-FS, and IM-FS(b)) were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM)-EDS, and Fourier-transformed infrared spectroscopy (FT-IR). The points of the zero charge (PZC) and the organic carbon percentages were also determined. The effect of the organic matter, contact time, praseodymium concentration, temperature, and praseodymium desorption were evaluated. The minerals found in the materials were quartz, albite, and kaolinite; the PZC were 6.12, 7.28, and 6.11 for FS, IM-FS, and IM-FS(b), respectively, and their organic carbon percentages were 9.1 ± 0.1, 7.2 ± 0.6, and < 0.1, respectively. The adsorption kinetic data for FS and IM-FS were best adjusted to the pseudo second-order model, and the isotherms data to the Langmuir–Freundlich model indicating a chemical adsorption mechanism on heterogeneous materials, the maximum adsorption capacities were 18.53, 12.98 mg/g and virtually negligible for FS, IM-FS, and IM-FS(b) respectively. The adsorption processes were exothermic; the desorption processes showed that praseodymium is more stable in FS than IM-FS, and Na2H2EDTA was the best desorbent agent. The adsorption capacities and praseodymium stability depend on the organic matter content. The adsorption capacities followed the order: FS > IM-FS > IM-FS(b). [ABSTRACT FROM AUTHOR]

In the present study, based on continuous acid–base potentiometric titration experiments of argillaceous limestone-derived yellow soil obtained at different depths in Pingba, Guizhou, a 1-site/2-pKa generalized composite surface complexation model (SCM) was established to obtain relevant parameters and explore soil surface acid–base properties. The model was employed to simulate cadmium (Cd) adsorption behavior. Combining the physicochemical properties of yellow soil and acid–base titration curves, the SCM-derived concentrations (Hs) and densities (Ds) of the surface-active sites for three soil layers showed decreasing trends with an increase in depth, whereas the calculated soil charge zero point (pHpzc) values matched the experimental values, indicating the applicability of SCM in studying the surface acid–base properties of yellow soil. Furthermore, as the pH increased, Cd shifted gradually from the dissolved to the adsorbed state, achieving complete adsorption at a pH of ~ 7. The model-simulated Cd adsorption curve matched well with the experimental curve; the Cd adsorption behavior corresponded with the simulated distribution of surface sites at different pH levels, with ≡SOH2+ and ≡SO− being the main forms at pH < pHpzc and pH > pHpzc, respectively. Correlation analysis indicated that organic matter and goethite played a major role in Hs, whereas the charge zero points of soils at different depths were determined mainly by clay minerals, such as illite and iron-aluminum oxides. Our study established a scientific and reasonable relationship between the soil physicochemical properties and model parameters, providing a basis for preventing heavy metal pollution behavior via the effective application of model predictions. [ABSTRACT FROM AUTHOR]

In this investigation, the purifying power of a biodegradable coagulant extracted from banana peel waste was studied and compared with that of a synthesized coagulant, hydroxyapatite. The biocoagulant of banana peel powder was prepared and characterized using different techniques, such as Fourier-transform infrared spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray microanalysis, X-ray diffraction, and X-ray fluorescence spectrometry. The coagulation-flocculation process was adopted to treat water loaded with copper, zinc, and suspended matter. The experimental design methodology was employed for the optimization of the experimental conditions. The Box Behnken design with three factors (dose, granulation, and initial pH) defined in 15 experiments was chosen. Within the pH range of 6 to 8, there was a noticeable increase in the rate of elimination, and this noteworthy trend was confirmed by the observable changes in the point of zero charge. The biocoagulant shows a very good coagulation capacity comparable to that of hydroxyapatite in Zn removal. The obtained values for the removal of Zn, Cu, and turbidity using banana peel powder and hydroxyapatite were 86 %, 96 %, and 97 %, and 68 %, 99 %, and 97 %, respectively. Banana peel powder has the potential to serve as a cost-effective and eco-friendly option for wastewater treatment in the context of waste valorization and environmental protection. [ABSTRACT FROM AUTHOR]

A novel biochar (BC) from Acaciatortilis trees pruning waste was synthesized and tested for the removal of phosphate from aqueous solutions. The BC was prepared by calcination at 600 °C and doped with Fe3O4 and MgO by hydrothermal process. The presence of iron and magnesium ions in the modified BC was confirmed by EDS analysis and X-ray diffraction (XRD) methods. Both unmodified and doped BCs were tested for phosphate removal from synthetic 1–500 ppm aqueous solutions. While the unmodified BC did not show any significant removal of phosphate from aqueous solutions, the modified BC almost completely removed phosphate from water. The enhancement in removal efficiency is due to an increase in the overall surface charge and surface area of BC as a result of doping with Fe3O4 and MgO salts. The average porosity and BET surface area corresponding to the plain BC increased by more than 20% from 322 to 394 m2/g after modification by impregnation with iron oxide and magnesium oxide. The modificaiton of BC with Fe3O4 and MgO nanoparticles was observed to increase the point of zero electric charge (PZC) from pH 3.4 (corresponding to plain BC) to pH 5.3 (corresponding to modified BC). The adsorption process was very fast and a phosphate removal value of 82.5% was reached only after 30 min of adsorption, while the removal efficiency after 4 h of adsorption was 97.5%. The rapid removal efficiency in short contact time is attributed to the high surface area of BC and strong bonding between the modified BC surface and PO43− ions. The highest adsorption capacity was observed to correspond to 98.5 mg/g which was achieved at PO43− concentration of 500 ppm and pH 8.5. Moreover, after fitting the adsorption data onto four of the most widely used adsorption isotherm models, the adsorption of PO43− onto BC can be better described by the Langmuir isotherm model. [ABSTRACT FROM AUTHOR]

ABSTARCTDyes released through various industrial operations are a major threat to the environment. The recent study introduced an eco-friendly adsorbent based on the grafting of phenolic acids (caffeic and/or gallic acids) on chitosan to reduce the hazardous impact of color effluent pollution. The morphology and structure of synthesized adsorbents were confirmed by physical and chemical tools such as TGA, FTIR, SEM, EDX, point of zero charge, water regain, and resistance of adsorbents to dissociation in acidic media. The synthesized adsorbents’ removal efficiency toward MB dye, a model cationic organic pollutant, from aqueous medium was evaluated. The factors impacting dye adsorption were investigated, including pH, dye initial concentration, and temperature. The response surface methodology (RSM) was used to confirm the interaction effects of the process variables and optimize the ideal conditions of adsorption. The maximum adsorption capacity was 257.0 and 391.8 mg/g for AI and AII, respectively, at initial MB concentration of 550 ± 1 mg/L, pH 8, and 21 ± 1 °C. MB adsorption is an exothermic chemosorption process that takes place via electrostatic attraction in an alkaline medium. Both AI and AII demonstrated significant reuse ability when eluted with a 0.5 M HCl solution. [ABSTRACT FROM AUTHOR]

In this work, zinc oxide (ZnO)/granular activated carbon (GAC) composites at different ZnO concentrations (0.25M-ZnO@GAC, 0.5M-ZnO@GAC, and 0.75M-ZnO@GAC) were prepared by an in-situ hydrothermal method and demonstrated synergistic photocatalytic degradation and adsorption of rhodamine B (RhB). The thermal stability, morphological structure, elemental composition, crystallographic structure, and textural properties of developed catalysts were characterized by thermal gravimetric analysis (TGA/DTG), scanning electron microscopy equipped with energy dispersive-x-ray (SEM-EDS), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) analysis. The successful loading of ZnO onto GAC was confirmed by SEM-EDS and XRD analysis. The BET surface areas of GAC, 0.25M-ZnO@GAC, 0.5M-ZnO@GAC, and 0.75M-ZnO@GAC were 474 m2/g, 450 m2/g, 453 m2/g, and 421 m2/g, respectively. The decrease in GAC could be attributed to the successful loading of ZnO on the GAC surface. Notably, 0.5M-ZnO@GAC exhibited the best photocatalytic degradation efficiency of 82% and 97% under UV-A and UV-C light over 120 min, attributed to improved crystallinity and visible light absorption. The photocatalytic degradation parameters revealed that lowering the RhB concentration and raising the catalyst dosage and pH beyond the point of zero charge (PZC) would favor the RhB degradation. Photocatalytic reusability was demonstrated over five cycles. Scavenger tests revealed that the hydroxyl radicals (•OH), superoxide radicals (O2−•), and photoinduced hole (h+) radicals play a major role during the RhB degradation process. Based on the TOC results, the RhB mineralization efficiency of 79.1% was achieved by 0.5M-ZnO@GAC. Additionally, GAC exhibited a strong adsorptive performance towards RhB, with adsorption capacity and the RhB removal of 487.1 mg/g and 99.5% achieved within 90 min of equilibrium time. The adsorption characteristics were best described by pseudo-second-order kinetics, suggesting chemical adsorption. This research offers a new strategy for the development of effective photocatalyst materials with potential for wider wastewater treatment applications. [ABSTRACT FROM AUTHOR]

Owing to the demand for chemical analysis of low concentrations of the Brilliant Green (BG) dye released into the environment, molecularly imprinted polymer (MIP) materials have been investigated for their use in SPME preconcentration devices. Thin coatings of MIP on solid supports allow fast adsorption of the analyte and higher selectivity of adsorption. Biosourced fibers of Posidonia oceanica (Pos) were taken as a the solid support to which a thin film of MIP was chemically attached. The material synthesis involved two steps: chemical grafting of methacrylate groups onto Pos by a silane coupling, and copolymerization with the free functional monomer and cross-linker in the presence of BG. Polymerization of the functional monomers methacrylic acid and acrylamide yielded the materials PosMAA@MIP and PosAA@MIP respectively. The strength of their interaction with BG and the stoichiometry of the pre-polymerization complex were assessed by 1H NMR experiments in DMSO-d6 solution. Characterization by IR spectroscopy and thermogravimetric analysis validated the successful syntheses. The points of zero charge were at pH 3.31 and 4.50 for PosMAA@MIP and PosAA@MIP, respectively, influencing the optimal adsorption of BG at pH 4. Kinetic studies revealed the rapid adsorption of more than 90% of the BG within 20 min. All MIPs exhibited higher adsorption capacity for BG compared to non-imprinted materials. PosAA@MIP showed the highest adsorption efficiency and selectivity, with an imprinting factor of 1.9. The thermodynamics of adsorption was studied by fitting the Langmuir–Volmer and Volmer models to the experimental data, from which the selective adsorption capacities of BG on PosMAA@MIP and PosAA@MIP were 289 and 313 µmol·g−1, respectively. Additionally, PosAA@MIP exhibited higher extraction efficiency for BG than for its metabolites eosin and methylene blue, underscoring its superior ability to selectively capture target molecules. [ABSTRACT FROM AUTHOR]

This paper presents the results of the application of hazardous waste slag generated by lignite combustion for the adsorption of ethyl xanthate anions (EX) from aqueous solutions. The starting material (RWS) was washed (WWS) and modified (MWS) and then characterized in detail by using different chemical and physical–chemical techniques (determination of chemical composition and content of heavy metals, X-ray diffraction (XRD), infrared spectroscopy (FTIR), determination of textural properties and point of zero charge). Besides the chemical stability of EX, the influence of the initial pH, mass of the adsorbent, initial concentration, and time on the EX anion removal was tested. The characterization results showed that applied waste slag is a hazardous material with complex mineral and structural properties but with good buffer properties and pH stability, which is also characteristic of the MWS sample. The adsorption experiments showed that modification with Cu(NO3)2 and Fe(NO3)3 significantly increases the adsorption capacity of the starting slag. Under applied experimental conditions, the maximal adsorbed amount of EX anions on the MWS was 210 mg/g, while equilibrium was obtained after 700 min. The Freundlich model and pseudo-second-order model best fit the results, suggesting the complex mechanism of EX removal by the MWS sample. [ABSTRACT FROM AUTHOR]

AbstractOur study focused on the removal of metformin in aqueous solution. Metformin, an antidiabetic drug, is increasingly detected in wastewater. This study explored the feasibility of using bentonite encapsulated in sodium alginate as a sustainable and efficient sorbent for metformin removal. The adsorbent was characterized by RAMAN, Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), electron-dispersive spectrometer (EDS), and point of zero charge (pHzc). The adsorbent contains various functional groups including hydroxyl (-OH) groups from both bentonite and sodium alginate, carboxyl (-COOH) groups from sodium alginate, and silanol (-Si-OH) groups from bentonite. Batch kinetic studies were carried out as a function of pH, metformin concentration, sorbent amount, and solution temperature. The Freundlich and Langmuir models were used to describe the isotherm data. The maximum monolayer adsorption capacity of the sorbent material was 19,19 mgg−1. The pseudo-second order kinetic model adequately describes the kinetic data. The negative ΔH (−35,253 kJmol−1) confirms an exothermic process, which is further supported by the negative Gibbs energy values (−0,489 to −3,668 kJmol−1), indicating spontaneity and reversibility. Moreover, ΔS° = −0.105 kJ/mol−1.K−1. Response surface methodology was employed to identify the optimal parameters for metformin removal. These parameters were found to be: pH of 6.34, metformin concentration of 5.4 mgL−1, and adsorbent dosage of 3 g L−1 resulted in a remarkable efficiency of 94%. Additionally, bentonite beads (BBs) maintained a significant adsorption capacity for up to three cycles, demonstrating promising reusability. This study highlights that the encapsulation of clay in sodium alginate is a sustainable and effective approach for removing metformin during water treatment. [ABSTRACT FROM AUTHOR]

Dyes in wastewater are highly toxic pollutants that have negative physical, chemical, and ecological effects on aquatic ecosystems even at low concentrations. In this study, the efficiency of chemically synthesized graphene oxide (CG) for the removal of the organic dye Isolan Bordeaux 2S-B and the principles of adsorption were investigated. Scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses were performed to characterize the CG, and the point of zero charge value was determined. The optimal conditions were found to be a pH of 2, an adsorbent dosage of 0.2 g, and a reaction time and temperature of 30 min and 25 °C, respectively. The adsorption equilibrium data fitted well with the Langmuir isotherm (R2 =0.98, RMSE = 0.38). The adsorption kinetics data followed a pseudo-second-order kinetic model (R2 = 0.99). Thermodynamic studies have shown that adsorption is exothermic and spontaneous. Desorption-regeneration studies demonstrated that CG is a highly stable adsorbent, and experiments in the presence of foreign ions show that it has a high selective affinity for anionic dyes. CG is effective not only in removing IB 2S-B but also shows promise in selectively removing anionic dyes from wastewater as a long-lasting adsorbent. [ABSTRACT FROM AUTHOR]

The paper assesses batch system microcrystalline cellulose (MCC) adsorptive ability for copper and iron uptake from aquatic environment. Field emission scanning electron microscope (FESEM), point zero charge and Fourier transform infrared (FTIR) spectroscopy were used to examine the physicochemical and morphological features of MCC. The batch system of the sequestration progression for the elimination of Cu(II) and Fe(II) was used by varying the solution pH, MCC doses, initial copper and iron concentration, and resident time. The maximum removal percentage for Cu(II) and Fe(II) were 99.5% and 96.4%, respectively, at pH 7. The influence of MCC dosage showed the 1.0 g/L of adsorbents results the highest percentage of Cu(II) (99.8%) and Fe(II) (88.63%) correspondingly. Equilibrium data for both metals were well fitted with both Langmuir and Freundlich isotherms, representing monolayer and multilayer adsorption systems. The maximum sorption capacity of MCC was 534.61 mg/g and 845.75 mg/g, respectively, for Cu(II) and Fe(II) ions at room temperature. Pseudo-second-order model best describes the copper and iron kinetic data, signifying the dominance of chemisorption adsorption relation between the negatively charged MCC and adsorbates. After four successive regeneration cycles, the MCC polymer maintained its maximal adsorption capacity, demonstrating effective copper and iron ion separation from aqueous solution. According to the study's findings, poisonous heavy metals can be successfully removed from aquatic environments using eco-friendly microcrystalline cellulose. [ABSTRACT FROM AUTHOR]

The disposal of industrial effluents containing cadmium and copper ions is a significant environmental concern. This study aims to address this issue by evaluating the adsorption capacity of adsorbents derived from residual biomass from second-generation ethanol production. The objective is to effectively remove cadmium and copper ions from aqueous solutions. The biochar utilized in the study was characterized as microporous and exhibited characteristic bands associated with carboxyls and hydroxyls. The pHPZC (point of zero charge) was determined to be 8.0. The kinetic study revealed that the PSO (pseudo-second-order) model provided the best fit, indicating that the adsorption rate depends on the amount of solute adsorbed onto the adsorbent's surface. In the equilibrium study, it was observed that adsorption occurred in a monolayer, as evidenced by the superior fit of the Langmuir model. Furthermore, the equilibrium experimental data for the bicomponent system was more accurately represented by the empirical models of Extended Freundlich and Modified Redlich-Peterson. These findings demonstrate the potential of biochar derived from the residue of second-generation ethanol production, a novel application, in effectively removing cadmium and copper ions from aqueous solutions. [ABSTRACT FROM AUTHOR]

Hydrotalcite-type compounds (HTs) are crystalline ion-exchange materials formed by positively charged sheets of metal hydroxides stabilized with interlayer anions. The synthesis methods significantly influence their crystallographic and morphological properties. Alternative methods, such as microwave or ultrasound irradiation, can reduce the synthesis time and obtain materials with specific characteristics. HT with the interlayer anion of NO3− was synthesized via conventional aging (hydrothermal), microwave, ultrasound, and combined (microwave/ultrasound) methods. The obtained compounds were characterized via X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDS), N2 adsorption-desorption, Fourier-transform infrared spectroscopy (FTIR), and point of zero charge. A larger crystal size ( t = 5.9 nm) and a higher surface area ( S = 6.70 m2 g−1) were obtained when HT was irradiated by microwaves/ultrasound compared to the synthesized compound via hydrothermal aging ( t = 5.5 nm, S = 1.83 m2 g−1). Although the removal capacity of the combined-mode irradiated compound was slightly lower ( q max = 41.7 ± 4.8 mg g−1) than the conventionally aged sample ( q max = 44.4 ± 6.8 mg g−1), the synthesis time was drastically decreased from 24 h to 5 min, and the combined-mode irradiated compound could remove fluoride as efficiently as the compounds obtained conventionally. [ABSTRACT FROM AUTHOR]

Water pollution has become a great challenge today. To address this problem regarding wastewater treatment by removing toxic synthetic dyes from wastewater, this research focused on the synthesis of a novel starch-modified NiCrMn-layered double hydroxide composite through the coprecipitation method and applied it as a photocatalyst for the degradation of reactive orange 13 dye. The synthesized photocatalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), point of zero charges (PZC), dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Zeta potential techniques. These techniques revealed different characteristics of photocatalysts, like surface and structural properties. According to BET analysis, the final composite had 2.5 × 102 m2/g BET-specific surface area with a 45.56 nm pore radius value, and the overall composite found as mesoporous. Similarly, in DLS analysis, bare NiCrMn-LDH had 404 nm hydrodynamic size, which increased for the final starch composite up to 667 nm. Zeta potential value changed from −14.56 mV to 0.95 mV after the incorporation of starch with NiCrMn-LDH. They confirmed the incorporation of starch with trimetallic NiCrMn-layered double hydroxide (2:1:2). Starch association improved the properties of the photocatalyst like surface area. Different parameters like pH value, initial dye concentration, photocatalyst dose, hydrogen peroxide concentration, effect of sacrificial reagent, and effect of inorganic anions were studied for degradation of RO13. Overall, the photocatalysis process for RO13 followed pseudo-first-order kinetics. Photocatalytic degradation reactions for reactive orange 13 were conducted with an initial dye concentration of 10 mg/L, photocatalyst dosage of 20 mg/50 mL, and pH value at 3 in the presence of sunlight, resulting in an impressive degradation removal rate of 86.68%. This remarkable degradation ability of the photocatalyst for reactive orange 13 proves this composite was highly efficient. [ABSTRACT FROM AUTHOR]

Context and results: A nanocomposite photocatalyst consisting of polyaniline (PANI) and copper oxide (CuO) was successfully synthesized through an in-situ polymerization approach using aniline as the precursor. The synthesized nanocomposite was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–Vis), determination of the point of zero charge (pHPZC), and scanning electron microscopy (SEM). The photocatalytic efficiency of the PANI–CuO nanocomposite was evaluated in the context of photodegrading Malachite Green (MG) dye under visible light. Malachite Green, a synthetic dye commonly used in the textile and aquaculture industries, is a significant contaminant due to its toxic, mutagenic, and carcinogenic properties, making its removal from water resources crucial for environmental and human health. Distilled water artificially contaminated with MG dye was used as the medium for testing. The parameters influencing the photodegradation efficiency were comprehensively investigated. These parameters included catalyst dosage, reaction time, initial dye concentration, and pH. The results of this study indicate that the degradation efficiency of MG dye displayed an upward trend with time, catalyst dosage, and pH while exhibiting a converse relationship with the initial dye concentration. A degradation rate of 97% was achieved with an initial concentration of 20 mg L−1, employing a catalyst dose of 1.6 g L−1 at pH 6 for a reaction time of 180 min. Furthermore, the reusability of the catalyst was assessed, revealing consistent performance over five consecutive cycles. Computational and theoretical techniques: Density functional theory (DFT) was employed to optimize the structures of PANI, PANI–CuO, and their respective complexes formed through dye interaction, employing Gaussian software. These calculations employed the B3LYP/6–311G + + (d,p) basis set in an aqueous environment with water serving as the solvent. The kinetics of Malachite Green degradation were analyzed using both first and second-order kinetic models. [ABSTRACT FROM AUTHOR]

The industrial processes with the greatest negative impact on the environment are caused by textile industries due to discharge of large volumes of colored wastewater contaminated with dyes and other chemical additives. These pollutants cause damages to the ecosystems. In this study, magnesium oxide nanoparticles (MgO NPs) were used for the removal of pollutants emerging from textile industries. The MgO NPs were synthesized by an eco-friendly approach using stabilizer, Saccharum officinarum. The MgO nanoparticles underwent characterization through UV-Vis spectroscopy, XRD, FTIR, and SEM. The surface neutrality of them was determined by PH at point of zero charge PH(pzc). Furthermore, MgO NPs have been used to remove pollutants from textile waste water by photocatalytic degradation and adsorption process simultaneously. A statistical approach employing the Response Surface Method (RSM) and Central Composite Design (CCD) was utilized to develop an experimental model for the efficient removal of pollutant through the adsorption process. The adsorption isotherm models, namely Freundlich and Langmuir, were applied to determine feasibility of adsorption process. A pseudo second order kinetic model was used to determine adsorption kinetics of dye removal by MgO NPs. The adsorption isotherms were used for the adsorption equilibrium studies. According to thermodynamic studies, adsorption of dye on MgO NPs is an exothermic spontaneous process. The experimental findings indicated the higher favorability of the photodegradation process over the adsorption method for the removal of Basic violet 1 (BV1) dye. The MgO nanoparticles show favourable efficacy at optimal values of [pH about 7.5], [BV1 dye concentration was 20 mg/L], [amount of nanoparticles was 0.01 g], [ultrasonication time was 8 min] and [photo irradiation time was 240 min]. The removal was observed to be 90.00 % by adsorption process and 99.05 % via photocatalytic method for the removal of BV1 dye. [ABSTRACT FROM AUTHOR]

In this study, zero-valent nickel NPs immobilized on biowaste-based activated carbon (ZVNi@AC) were prepared using a single-step pyrolytic reduction/activation method. ZVNi@AC was characterized using various techniques, including BET, SEM, TEM, EDS, FTIR, XRD and point of zero charge (pHpzc) analysis. The nanocomposite is composed of highly porous activated carbon and decorated with ZVNi NPs, with a surface area of 975 m2 g−1. The modified activated carbon (ZVNi@AC) demonstrated a superior adsorption performance (367.59 mg g−1) for cephalexin antibiotic removal compared to the unmodified activated carbon (287.91 mg g−1). Cephalexin adsorption onto ZVNi@AC was most effective at pH 4.5 and 40 °C, where more than 95% of cephalexin was removed within 36 min. Thermodynamic analysis revealed the adsorption process to be spontaneous (negative ΔG°) and endothermic (positive ΔH°). The excellent removal efficiency, reaching up to 92%, of ZVNi@AC for five cycles demonstrated the potential application of this adsorbent for antibiotic removal from wastewater. [ABSTRACT FROM AUTHOR]

A novel mesoporous magnetic biochar (MBC) was prepared, using a randomly growing plant, i.e., common reed, as an exporter of carbon, and applied for removal of methylene blue (MB) from aqueous solutions. The prepared sorbent was characterized by nitrogen adsorption/desorption isotherm, saturation magnetization, pH of point of zero charges (pHPZC), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The obtained MBC has a specific surface area of 94.2 m2 g−1 and a pore radius of 4.1 nm, a pore volume of 0.252 cm3 g−1, a saturation magnetization of 0.786 emu g−1, and a pHPZC of 6.2. Batch adsorption experiments were used to study the impact of the physicochemical factors involved in the adsorption process. The findings revealed that MB removal by MBC was achieved optimally at pH 8.0, sorbent dosage of 1.0 g L−1, and contact time of 30 min. At these conditions, the maximum adsorption was 353.4 mg g−1. Furthermore, the adsorption isotherm indicated that the Langmuir pattern matched well with the experimental data, compared to the Freindlich model. The ∆G was − 6.7, − 7.1, and − 7.5 kJ mol−1, at 298, 308, and 318 K, respectively, indicating a spontaneous process. The values of ∆H and ∆S were 5.71 kJ mol−1 and 41.6 J mol−1 K−1, respectively, suggesting endothermic and the interaction between MB and MBC is van der Waals type. The absorbent was regenerated and reused for four cycles after elution with 0.1 mol L−1 of HCl. This study concluded that the magnetic biochar generated from common reed has tremendous promise in the practical use of removing MB from wastewater. [ABSTRACT FROM AUTHOR]

In the present work, Zinc ferrite composites with Mango starch (MS) and carboxymethyl mango starch (CMMS) were synthesized for the removal of Ni (II) ions from aqueous solutions. Composites prepared were characterized by Fourier Transform Infrared (FTIR) Spectroscopy, X-Ray Diffraction (XRD) analysis, pH of point zero charge (pHzpc), Scanning Electron Microscopy (SEM), and BET. Batch adsorption technique was used to study effect of various parameters such as pH, adsorbent dose, contact time, concentration, and temperature for removal of Ni (II) ions from aqueous solutions. The optimum time, pH, adsorbent dose and temperature required for ZFN@ MS and ZFN@ CMMS in this study was 110 min., 7 & 8, 0.1 g and 308 K, respectively. Out of various adsorption isotherms, Freundlich isotherm model fitted best with adsorption data. Maximum adsorption capacity for removal of Ni (II) were found to be 65.3 and 208.3 mg/g, respectively by using Zinc ferrite@ MS and Zinc ferrite@ CMMS adsorbents. Lagergren Pseudo second order model best fitted with results which indicated that the process of adsorption was chemical in nature. The value of adsorption energy for ZFN@ MS was 50 kJ/mol and for ZFN@ CMMS, it was 31.62 kJ/mol. Thermodynamic study revealed that process was endothermic and non-spontaneous in nature. Regeneration studies were conducted for five cycles where Zinc ferrite@ MS showed 71% regeneration efficiency and Zinc ferrite@ CMMS showed 78% regeneration efficiency for nickel ion removal from aqueous solution. [ABSTRACT FROM AUTHOR]

In this study, an effective and inexpensive PAA-CG composite was synthesized using polyacrylamide (PAA) and coffee ground (CG) with the help of the in situ polymerization method. The adsorption efficiency of this new composite was investigated in the removal of Pb(II) ions from an aqueous solution. Characterization was done by Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy and zero charge point analysis. The maximum adsorption capacity of the PAA-CG composite was calculated as 0.622 mol/kg according to the Langmuir isotherm model. From the obtained data, it was determined that the adsorption mechanism is compatible with pseudo-second-order kinetics and intra-particle diffusion model. The calculated thermodynamic data showed that adsorption is endothermic, spontaneous and entropy increasing. [ABSTRACT FROM AUTHOR]

The objective of the present work is to develop a simple route for synthesis of visible light active ZnO/g-C3N4 type-II heterojunction photocatalysts with improved photodegradation performance. The g-C3N4 is synthesized by single step thermolysis method, whereas, ZnO and ZnO/g-C3N4 type-II heterojunction photocatalysts with different (10, 15, and 20 wt%) loading of ZnO are synthesized by a simple hydrothermal method. The structural, morphological and optical properties are analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, diffuse reflectance spectroscopy, and photoluminescence characterizations. The synthesized photocatalysts are used to degrade the rhodamine B (RhB) dye under 35 W Xe light lamp. The photocatalytic activity is investigated in detail via different experiments like effect of pH, trapping of reactive oxygen species (ROS), cyclic stability test, etc. The ZnO/g-C3N4 type-II heterojunction photocatalysts with 15 wt% loading of ZnO (15ZG) shows the best photodegradation performance with 0.52 min−1 degradation rate constant and superoxide radicals (·O2−) as major ROS. Further, it exhibits highest degradation rate in acidic medium (pH = 3) with its point of zero charge value 2.54 and possesses good cyclic stability with high activity (91% after 5 cycles). In addition, the photocurrent measurement study is conducted to explore the concept of capability of charge separation and transportation processes across the heterojunction. A photodegradation mechanism involved in the said activity is presented. The 15ZG heterojunction photocatalyst is very much capable for water purification applications. [ABSTRACT FROM AUTHOR]

In the present research, the presence of water hyacinth (Eichhornia crassipes) on the surface of the San Jose Dam located in the city of San Luis Potosi, S.L.P, Mexico, was monitored and mapped. The monitoring was conducted for 2 years (2018–2020) with remote sensing data from OLI Landsat 8 sensors, based on the normalized difference vegetation index (NDVI). The results demonstrated the capability and accuracy of this method, where it was observed that the aboveground cover area, proliferation, and distribution of water hyacinth are influenced by climatic and anthropogenic factors during the four seasons of the year. As part of a sustainable environmental control of this invasive species, the use of water hyacinth (WH) root (RO), stem (ST), and leaf (LE) components as adsorbent material for Pb(II) present in aqueous solution was proposed. The maximum adsorption capacity was observed at pH 5 and 25 °C and was 107.3, 136.8, and 120.8 mg g−1 for RO, ST, and LE, respectively. The physicochemical characterization of WH consisted of scanning electron microscopy (SEM), N2 physisorption, infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), charge distribution, and zero charge point (pHPZC). Due to the chemical nature of WH, several Pb(II) adsorption mechanisms were proposed such as electrostatic attractions, ion exchange, microprecipitation, and π-cation. [ABSTRACT FROM AUTHOR]

The global scientific community is deeply concerned about the deterioration of water quality resulting from the release of industrial effluents. This issue is of utmost importance as it serves to safeguard the environment and combat water pollution. The objective of this work is to elaborate a biomaterial of vegetable origin, based on the twigs of Aleppo pine, and to use it as an abundant and less expensive material for the treatment of wastewater. For this reason, the twigs were treated physically to get the powder called biomaterial FPA (Aleppo pine fiber), which was characterized by physicochemical, and spectroscopic analyses namely scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The crystallinity index of FPA was evaluated by the peak height method. The findings indicate that the FPA powder has an acidic nature, exhibiting a porous structure that promotes the adsorption and binding of molecules. Additionally, it has a zero charge point of 5.8 and a specific surface area of 384 m2.g−1. It is primarily composed of hydroxyl, carboxyl, and amine functional groups, along with mineral compounds and organic compounds, including cellulose and other mineral elements such as Ca, Mg, Fe, Na, P, Al, K, Ni, and Mo. Combining these characteristics, FPA biomaterial has considerable potential for use as an effective adsorbent biomaterial for various wastewater pollutants. Its abundance and relatively low cost make it an attractive solution to the growing challenges of water pollution worldwide. [ABSTRACT FROM AUTHOR]

The current study aims to use a facile and novel method to remove Congo red (CR) and Methyl Orange (MO) dyes from contaminated water with Maize offal biomass (MOB) and its nanocomposite with magnetic nanoparticles (MOB/MNPs). The MOB and MOB/MNPs were characterized with Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), BET, XRD and point of zero charge (pHPZC). The influence of initial CR and MO levels (20–320 mg/L), adsorbent dosage (1-3 g/L), pH (3-9), co-exiting ions, temperature (25–45 °C) and time (15–180 min) was estimated. The findings demonstrated that MOB/MNPs exhibited excellent adsorption of 114.75 and 29.0 mg/g for CR and MO dyes, respectively while MOB exhibited 81.35 and 23.02 mg/g adsorption for CR and MO dyes, respectively at optimum pH-5, and dose 2 g/L. Initially, there was rapid dye removal which slowed down until equilibrium was reached. The interfering/competing ions in contaminated water and elevated temperature favored the dyes sequestration. The MOB/MNPs exhibited tremendous reusability and stability. The dyes adsorption was spontaneous, and exothermic with enhanced randomness. The adsorption effects were well explained with Freundlich model, pseudo second order and Elovich models. It is concluded that MOB/MNPs showed excellent, eco-friendly, and cost-effective potential to decontaminate the water. Nanocomposite of Maize offal biomass demonstrated higher dyes removal. FTIR, SEM, BET, XRD and pHPZC provided vital evidence for dyes adsorption. MOB/MNPs displayed excellent stability and reusability for dyes adsorption. Groundwater samples exposed a higher dyes removal. Results were validated with equilibrium and kinetic adsorption models. [ABSTRACT FROM AUTHOR]

The aim of the present study was to compare the effectiveness of raw chicken feathers (RCFs), NaOH and ethylenediamine-modified chicken feathers (MCFs), and xanthate-modified chicken feathers (XMCFs), treated with both NaOH, ethylenediamine, and carbon disulfide. The physicochemical characteristics of the biosorbents were analyzed using attenuated total reflection Fourier transform infrared spectrophotometry (ATR-FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), adsorption of N2 at −196°C and point of zero charge determination (pHpzc). The biosorption of Cr(VI) using MCFs and XMCFs was evaluated through various parameters, namely, pH, biosorbent amount, and contact time in batch experiments. The results showed a significant increase in the biosorption capacities of MCFs (90.90 mg/g) and XMCFs (100 mg/g) compared to RCFs (52.63 mg/g). The batch adsorption experiments indicated that the optimal conditions for biosorption were pH 2.0, with an equilibrium contact time of 90 min for RCFs, and 60 min for both MCFs and XMCFs. The optimal biosorbent concentrations were 16 g L−1 for RCFs and 12 g L−1 for both MCFs and XMCFs. The biosorption behavior was well described by the Langmuir isotherm and pseudo-second-order kinetic models. The thermodynamic parameters indicated that the biosorption of Cr(VI) onto the biosorbents was a spontaneous and endothermic process. Desorption analysis was carried out using a 0.1 M NaOH solution. [ABSTRACT FROM AUTHOR]

Pesticide contamination to water bodies is considered as a global concern. This study involves the use of activated carbon synthesized from the shells of Thevetia peruviana shell (TPS) for the removal of the potential pollutant, Methoxychlor (MXC) from water. The TPS was activated using potassium hydroxide and was characterized by pH point zero charge (pHpzc), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET). The activated material shows a high BET of 394.97 m2/g with a pHpzc of 2. Batch experiments were conducted to investigate the influence of operating conditions such as pH, temperature, adsorbent dosage, initial concentration, and contact time. Under optimum conditions, adsorption of MXC onto TPS had a removal efficiency of 94.90%. The sorption experiment data best fits the pseudo-second-order (PSO) kinetic model (R2 = 0.999) and also correlated with Langmuir isotherm model (maximum sorption capacity of 197.2 mg/g). The results reveal that TPS can be considered as an excellent adsorbent material for the removal of pesticides and applicable for real waste water treatment. [ABSTRACT FROM AUTHOR]

Biochar and carbon adsorbents from citrus waste have been prepared by thermal and chemical treatments; they have been used in the aqueous phase adsorption of acetaminophen (ACE) as a model emerging pollutant. These materials were fully characterized by elemental analysis, X-ray fluorescence (TXRF), adsorption/desorption of nitrogen, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), point of zero charge (pHpzc), scanning electron microscopy (SEM), and thermogravimetric analyses (TGA/DTG/DTA). A magnetic carbon adsorbent was obtained by FeCl3 activation under an inert atmosphere, giving rise to the best results in ACE adsorption. Adsorption equilibrium data were obtained at 298, 318, and 338 K and fitted to different models, corresponding to the best fitting to the Redlich–Peterson model. The maximum adsorption capacity at equilibrium resulted in 45 mg ACE·g−1 carbon at 338 K. The free energy values were calculated, and values between −21.03 and −23.00 kJ·mol−1 were obtained; the negative values confirmed the spontaneity of the process. The enthalpy and entropy of the adsorption process were obtained, giving rise to −6.4 kJ·mol−1 and 49 J·mol−1·K−1, respectively, indicating a slightly exothermic process and an increase in the randomness at the solid–liquid interface upon adsorption, respectively. The adsorption kinetics were also studied, with the Elovich model being the one that gave rise to the best-fitting results. [ABSTRACT FROM AUTHOR]

Chromium contamination in water bodies poses severe risks to both the environment and human health. This research introduces an innovative solution to this challenge by creating a vapor-activated carbosorbent from biodegradable household waste. The efficacy of this adsorbent in removing total chromium through batch methods from aqueous solutions was investigated. Surface analysis using scanning electron microscopy (SEM) exhibited a porous structure, while Fourier-transform infrared spectroscopy (FTIR) identified distinct functional groups on the surface. The point of zero charge (PZC), determined at 6.95, revealed the adsorbent's surface chemistry. Impressively, the synthesized carbosorbent exhibited significant adsorption capacities of 23.08 mg.g-1 for Cr(III) and 24.84 mg.g-1 for Cr(VI) under optimal conditions. The Langmuir isotherm model illustrated a monolayer adsorption mechanism aligned with the pseudo-second-order kinetic model, confirming chemisorption. Thermodynamic analysis disclosed favorable and spontaneous chromium adsorption. Negative ΔG° values affirmed the spontaneity, while the exothermic nature of the process was signified by the positive ΔH° value, indicating heat release. Increased randomness at the solid-liquid interface, indicated by the positive ΔS° value, underscored the enhanced affinity between the adsorbent and adsorbate. This study exemplifies the potential of the vaporactivated carbosorbent as an efficient and sustainable remedy for chromium-contaminated water bodies. [ABSTRACT FROM AUTHOR]

Arsenic (As) contamination of surface water has become a global concern, especially for the third world countries, and it is imperative to develop advanced materials and an effective treatment method to address the issue. In this paper, iron doped ZIF-8@MXene (Fe-ZIF-8@MXene) was prepared as a potential adsorbent to effectively and simultaneously remove As(III/V) from wastewater. To investigate this, Fe-ZIF-8@MXene was characterized before and after the removal of mixed As(III/V). The results of Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), specific surface area (BET) and point of zero charge (pHpzc) showed that Fe-ZIF-8@MXene was prepared successfully and kept a stable structure after As(III) and As(V) adsorption. The particle size of Fe-ZIF-8@MXene was in the range of 0.5 μm to 2.5 μm, where its BET was 531.7 m2/g. For both contaminants, adsorption was found to follow pseudo-second-order kinetics and was best-fitted by the Langmuir adsorption model with correlation coefficients (R2) of 0.998 and 0.997, for As(III) and As(V), respectively. The adsorbent was then applied to remove As from two actual water samples, giving maximum removal rates of 91.07% and 98.96% for As(III) and As(V), respectively. Finally, removal mechanisms for As(III/V) by Fe-ZIF-8@MXene were also explored. During the adsorption, multiple complexes were formed under the effect of its abundant surface functional groups involving multiple mechanisms, which included Van der Waals force, surface adsorption, chemical complexation and electrostatic interactions. In conclusion, this study demonstrated that Fe-ZIF-8@MXene was an advanced and reusable material for simultaneous removal of As(III/V) in wastewater. [ABSTRACT FROM AUTHOR]

BACKGROUND: This study aimed to produce activated carbon (AC) from spent coffee (Coffea arabica) grounds by chemical activation using zinc chloride (ZnCl2) and nitric acid to remove bentazone from aqueous solutions. RESULTS: The fresh spent coffee grounds were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and the AC by X‐ray diffraction (XRD), infrared spectroscopy (FTIR), Brunauer–Emmett– Teller (BET), point of zero charge, scanning electron microscopy (SEM) and the Boehman method. Adsorption experiments were carried out in a batch system. The results showed a 70% efficiency in bentazone removal using ZnCl2 carbon. Kinetic studies indicate that the adsorption rate increased slowly up to 720 min; the first‐ and second‐order models fitted the experimental data at a concentration of 50 mg L−1. The adsorption equilibrium is represented by the Langmuir model with a high adsorption capacity of 279.33 ± 6.29 mg mg−1. The adsorption efficiency was also confirmed by toxicity analysis of the effluent with bentazone at 50 mg L−1, using the Allium cepa bioassay, a high‐sensitivity test for pollutants in water. CONCLUSION: Before adsorption, the effluent caused significant cytogenotoxicity to onion root meristems. After adsorption, the generated effluent no longer caused toxicity to the test system, and the results obtained were similar to the control with distilled water. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

In this study, the chemical composition of Mytilus galloprovincialis shells was examined. As known, the main component of shell composition in bivalves is calcium carbonate, which constitutes approximately 94% of the shell. The zero charge points (PZC) of the shells were determined in the study. The PZC value indicates the surface charge state of the shells. The PZC value of the shells was determined to be 8.39. The PZC value of the shells provides important information for the characterization and potential applications of the shells. SEM images and EDS analyzes of the shells were made. According to the EDS results, calcium, carbon, and oxygen atoms belonging to the main structure of calcium carbonate (CaCO3) appeared in the highest proportions. FT-IR analysis was supported to the calcium carbonate (CaCO3) structure. XRD analyses were performed within the scope of the study, and it was determined that the shell structures mainly consist of a mixture of calcium carbonate and aragonite. In conclusion, this study on the chemical composition of M. galloprovincialis shells provides a detailed analysis of shell composition. The analyses conducted provide important information about the chemical composition, structural properties, and potential applications of the shells. This study contributes to research on the biological and chemical properties of marine organisms and is considered to form the basis for future studies. [ABSTRACT FROM AUTHOR]

In this study, the reuse of Citrus fortunella (CF) plant waste, an agricultural product, was evaluated within the scope of sustainability. In this context, selenium nanoparticles (CF‐Se NPs) were synthesized from CF waste extracts and crystal violet (CV) dye was removed. The characteristic structure of the synthesized CF‐Se NPs was determined by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy, and point of zero charge (pHpzc). Batch adsorption tests were applied to determine the effect of the synthesized CF‐Se NPs on CV removal. Four different kinetic and isotherm models were examined using error analysis functions. While the particle size of CF‐Se NPs was determined as 27.58 nm, the pHpzc value was calculated as 9.40, the average surface charge distribution was −24.1 mV, and mass losses were 9.03% and 13.42% at 334.99 and 739.21°C, respectively. The most suitable kinetic and isotherm model for CV removal with CF‐Se NPs was determined to be pseudo‐second‐order with a R2‐value of 0.999 and Freundlich with R2‐value of 0.993, and the qmax was calculated as 23.55 mgCV/gCF‐SeNPs. The effectiveness of CF‐Se NPs synthesized from waste in CV removal is a remarkable issue in terms of sustainable production. [ABSTRACT FROM AUTHOR]

Micron-scale zero-valent iron (ZVI)-based material has been applied for hexavalent chromium (Cr(VI)) decontamination in wastewater treatment and groundwater remediation, but the passivation problem has limited its field application. In this study, we combined aluminum chloride solution with ZVI (pcZVI-AlCl3) to enhance Cr(VI) removal behavior under aerobic conditions. The optimal pre-corrosion conditions were found to be 2.5 g/L ZVI, 0.5 mM AlCl3, and a 4 h preconditioning period. Different kinds of techniques were applied to detect the properties of preconditioned ZVI and corrosion products. The 57Fe Mössbauer spectra showed that proportions of ZVI, Fe3O4, and FeOOH in pcZVI-AlCl3 were 49.22%, 34.03%, and 16.76%, respectively. The formation of Al(OH)3 in the corrosion products improved its pHpzc (point of zero charge) for Cr(VI) adsorption. Continuous-flow experiments showed its great potential for Cr(VI) removal in field applications. The ZVI and corrosion products showed a synergistic effect in enhancing electron transfer for Cr(VI) removal. The mechanisms underlying Cr(VI) removal by pcZVI-AlCl3 included adsorption, reduction, and precipitation, and the contribution of adsorption was less. This work provides a new strategy for ZVI pre-corrosion to improve its longevity and enhance Cr(VI) removal. [ABSTRACT FROM AUTHOR]

Dye effluents cause diverse environmental problems. Methylene blue (MB) dye stands out since it is widely used in the textile industry. To reduce the pollution caused by the MB, we developed biosorbents from tucumã seeds, where the in natura seeds were treated with NaOH (BT) and H3PO4 (AT) solutions and characterized by Boehm titration, point of zero charges, FTIR, TGA, BET, and SEM. It was observed that the acid groups predominate on the surface of the three biosorbents. The process was optimized for all biosorbents at pH = 8, 7.5 g/L, 240 min, C0 = 250 mg/L, and 45 ℃. BT was more efficient in removing MB (96.20%; QMax = 35.71 mg/g), while IT and AT removed around 60% in similar conditions. The adsorption process best fits Langmuir and Redlich-Peterson isotherms, indicating a hybrid adsorption process (monolayer and multilayer) and pseudo-second-order kinetics. Thermodynamic data confirmed an endothermic and spontaneous adsorption process, mainly for BT. MB was also recovered through a desorption process with ethanol, allowing the BT recycling and reapplication of the dye. Thus, an efficient and sustainable biosorbent was developed, contributing to reducing environmental impacts. [ABSTRACT FROM AUTHOR]

Excessive fluoride presence in water poses significant environmental and public health risks, necessitating the development of effective remediation techniques. Conventional aluminum–based adsorbents face inherent limitations such as limited pH range and low adsorption capacity. To overcome these challenges, we present a facile solvent-thermal method for synthesizing a carbon-doped aluminum-based adsorbent (CDAA). Extensive characterization of CDAA reveals remarkable features including substantial carbon-containing groups, unsaturated aluminum sites, and a high pH at point of zero charge (pHpzc). CDAA demonstrates superior efficiency and selectivity in removing fluoride contaminants, surpassing other adsorbents. It exhibits exceptional adaptability across a broad pH spectrum from 3 to 12, with a maximum adsorption capacity of 637.4 mg/g, more than 110 times higher than alumina. The applicability of the Langmuir isotherm and pseudo-second-order models effectively supports these findings. Notably, CDAA exhibits rapid kinetics, achieving near-equilibrium within just 5 min. Comprehensive analyses utilizing Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) offer detailed insights into the mechanisms involving electrostatic attraction, ion exchange, and ligand exchange. Carbon-based groups play a role in ligand exchange processes, synergistically interacting with the unsaturated aluminum structure to provide a multitude of adsorption sites. The exceptional attributes of CDAA establish its immense potential as a transformative solution for the pressing challenge of fluoride removal from water sources. [ABSTRACT FROM AUTHOR]

• With an increase in Si/Fe ratio, the Cr(VI) adsorption on Si-Fh decreases. • The electrostatic repulsion has a greater increase than complexation with Si-Fh. • DFT and surface characterization reveals the mechanism of Cr(VI) retention by Si-Fh. Hexavalent chromium [Cr(VI)] causes serious harm to the environment due to its high toxicity, solubility, and mobility. Ferrihydrites (Fh) are the main adsorbent and trapping agent of Cr(VI) in soils and aquifers, and they usually coexist with silicate (Si), forming Si-containing ferrihydrite (Si-Fh) mixtures. However, the mechanism of Cr(VI) retention by Si-Fh mixtures is poorly understood. In this study, the behaviors and mechanisms of Cr(VI) adsorption onto Si-Fh with different Si/Fe molar ratios was investigated. Transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and other techniques were used to characterize Si-Fh and Cr(VI)-loading of Si-Fh. The results show that specific surface area of Si-Fh increases gradually with increasing Si/Fe ratios, but Cr(VI) adsorption on Si-Fh decreases with increasing Si/Fe ratios. This is because with an increase in Si/Fe molar ratio, the point of zero charge of Si-Fh gradually decreases and electrostatic repulsion between Si-Fh and Cr(VI) increases. However, the complexation of Cr(VI) is enhanced due to the increase in adsorbed hydroxyl (A-OH-) on Si-Fh with increasing Si/Fe molar ratio, which partly counteracts the effect of the electrostatic repulsion. Overall, the increase in the electrostatic repulsion has a greater impact on adsorption than the additional complexation with Si-Fh. Density functional theory calculation further supports this observation, showing the increases in electron variation of bonding atoms and reaction energies of inner spherical complexes with the increase in Si/Fe ratio. [Display omitted] [ABSTRACT FROM AUTHOR]

The current study comprehensively investigates the adsorption behavior of chromium (Cr(III)) in wastewater using Algerian kaolinite clay. The structural and textural properties of the kaolinite clay are extensively characterized through a range of analytical methods, including XRD, FTIR, SEM-EDS, XPS, laser granulometry, N2 adsorption isotherm, and TGA–DTA. The point of zero charge and zeta potential are also assessed. Chromium adsorption reached equilibrium within five minutes, achieving a maximum removal rate of 99% at pH 5. Adsorption equilibrium is modeled using the Langmuir, Freundlich, Temkin, Elovich, and Dubinin–Radushkevitch equations, with the Langmuir isotherm accurately describing the adsorption process and yielding a maximum adsorption capacity of 8.422 mg/g for Cr(III). Thermodynamic parameters suggest the spontaneous and endothermic nature of Cr(III) sorption, with an activation energy of 26.665 kJ/mol, indicating the importance of diffusion in the sorption process. Furthermore, advanced DFT computations, including COSMO-RS, molecular orbitals, IGM, RDG, and QTAIM analyses, are conducted to elucidate the nature of adsorption, revealing strong binding interactions between Cr(III) ions and the kaolinite surface. The integration of theoretical and experimental data not only enhances the understanding of Cr(III) removal using kaolinite but also demonstrates the effectiveness of this clay adsorbent for wastewater treatment. Furthermore, this study highlights the synergistic application of empirical research and computational modeling in elucidating complex adsorption processes. [ABSTRACT FROM AUTHOR]

A sulfonated polystyrene-iron composite magnetic material (PSSFe), which is nonpolluting, was synthesized using high-temperature reflux in a simple system. It was applied for the first time to the adsorption and removal of two dyes (methylene blue (MB) and congo red (CR)) from wastewater. The cost of synthesis is lower and simpler and then that of the large sites active in PSSFe, making it efficient cost effective for a large variety of dyes. Scanning electron microscopy (SEM), x-ray diffraction (XRD), thermogravimetric analysis (TGA-DTGA), infrared spectroscopy (FTIR), and the pH of the point of zero charge (pHPZC) were used to characterize the morphology and microstructure of the magnetic sample. The adsorption of methylene blue and congo red as a function of various factors, such as the effect of pH, time and temperature, was investigated. The results demonstrated that the Langmuir model well represented the isotherms, supporting monolayer and homogeneous adsorption, and the pseudo-second-order model could also capture the kinetic process of adsorption. The PSSFe exhibited adsorption capabilities (qe) of 99.7 and 76.9 (mg/g) for MB and CR, respectively. The adsorption of MB on PSSFe was endothermic, whereas the adsorption of CR on PSSFe was exothermic. During the first cycle, both MB and CR were successfully desorbed from PSSFe, with 99.7% and 92.5% removal percentages, respectively. [ABSTRACT FROM AUTHOR]

Unmodified and iron-modified hydrogels were synthesized from polyvinyl alcohol and polyvinylpyrrolidone; these materials were used for the adsorption of fluoride ions from an aqueous solution. The structural and morphological characteristics of the unmodified (HG) and modified (HG-Fe) hydrogels were determined by means of hydration percentage, point of zero charge (PZC), infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and dispersive energy spectroscopy (EDS). The parameters considered in the adsorption processes were contact time, pH, fluoride concentration and dosage. The kinetic data were obtained at an initial pH of 6.7 and were best fitted to the Elovich model (R2 = 0.994); the adsorption capacity was higher for HG-Fe than HG. The data obtained at pH 5 were adjusted to the Lagergren equation indicating physical adsorption. The capacities of both materials (HG and HG-Fe) were similar, and the equilibrium time was shorter for HG than HG-Fe. The isotherms were best fitted to the Langmuir model, indicating homogeneous materials. The maximum adsorption capacities were similar for both adsorbents (HG-Fe and HG), and the thermodynamic parameters showed that the processes are exothermic. [ABSTRACT FROM AUTHOR]

The biosorption of Pb(II) from an aqueous environment was studied using a mixed biofilm of microalgal biomass (Chlorella vulgaris) and natural pectin. A gas sorption analyzer, Fourier transform infrared spectrometer, field emission scanning electron microscope, point of zero charge determination, and texture analyzer were used for the adsorbent's characterization. Various sorption parameters such as contact time, initial pH, initial metal concentration and temperature were studied. The results were also used to conduct isotherm and kinetic studies. Subsequently, the second-order polynomial model following the response surface methodology was obtained with an R2 of 0.9941 indicating acceptable accuracy. Under the following condition: an initial pH of 4.27, an initial metal concentration of 300 mg/L, and a temperature of 55.2 °C, a maximum Pb(II) uptake of 121.89 mg/g was observed. The results show that the developed composite biofilm can effectively remove Pb(II) ions from contaminated water. [ABSTRACT FROM AUTHOR]

A chitosan-co-GLU/eucalyptus residue composite membrane was synthesized, characterized and applied in the stabilization of β-d-galactosidase in aqueous solution. From results of the point of zero charge, it was inferred that protonated glucosamine and carboxyl groups would be found on the surface of the membrane and in the structure of the enzyme at pH lower than 4.82 and 4.37, whereas deprotonated amine and carboxyl groups would be found on the surface of the membrane and in the structure of the enzyme at pH higher than 4.82 and 4.37. Fourier-transformed infrared spectra, thermal analysis results and scanning electron microscopy images confirmed the chemical structure, thermal stability and morphology of the membrane, respectively. The enzymatic stability of β-d-galactosidase under the influence of the composite membrane in the medium was evaluated at different temperatures and pH values. The following experimental conditions assisted in avoiding enzymatic degradation: (i) enzyme/buffer solution ratio of 0.0057, (ii) pH 5.6, (iii) membrane mass greater than 50 mg and (iv) temperature from 10 to 45 °C. In conclusion, certain solid supports are not only important for enzyme immobilization, but can also serve as matrices for stabilization of soluble free enzymes in reaction media. Thus, chitosan-co-GLU/eucalyptus residue composite membranes may be important to industrial processes that use soluble free enzymes. The lining of the sides of food industrial reactors covered with chitosan-co-GLU/eucalyptus residue composite membrane or film could be a strategy for the use of free β-d-galactosidase in the processing of dairy products to achieve the hydrolysis of lactose with greater efficiency. [ABSTRACT FROM AUTHOR]