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This study presents the synthesis and characterization of a copper-based layered double hydroxide (Cu-LDH) composite via the coprecipitation method. The composite material aimed to effectively remove the anionic dye "Coomassie Brilliant Blue" (CBB) and exhibit antibacterial properties against both gram-positive and gram-negative bacteria. The synthesized nanocomposites were characterized using various techniques. The adsorption of CBB dye was investigated by studying various physicochemical variables, including contact time, pH of the dye solution, and initial dye concentration. The optimal dosage and contact time for efficient CBB dye removal were determined as 0.07 g and 10 min, respectively. The results showed that Cu-LDHs exhibited a high adsorption capacity for CBB dye, with a maximum removal efficiency of 85% which could be achieved within 10 min, and the Cu-LDHs improved an experimental adsorption capacity at equilibrium qmax = 80 mg/g. The adsorption process followed a pseudo-second-order kinetic model. The Langmuir isotherm model provided a good fit to the equilibrium data, indicating monolayer adsorption. Furthermore, the antibacterial activity of Cu-LDHs was assessed against various bacterial strains using a diffusion method. The results demonstrated the inhibitory effects of Cu-LDHs and CBB-Cu-LDHs on bacterial growth at a dosage of 10 mg, indicating the potential of Cu-LDHs as antibacterial agents. The underlying mechanisms responsible for dye adsorption and antibacterial activity were discussed. [ABSTRACT FROM AUTHOR]

One of the major environmental problems we have today is dye pollution, primarily caused by the textile industry. This pollution has detrimental effects on aquatic life, soil fertility, and human health. Many microbial biosorbents have been documented in the literature for the removal of a wide range of azo dyes commonly employed in the textile industry. However, Yarrowia lipolytica NBRC1658 is firstly used as both free and immobilized sorbents for the removal of Reactive yellow 18 (RY18), acid red 18 (AR18) and basic blue 41 (BB41) in this study. The effect of experimental conditions such as pH, biosorbent quantity, dye concentration, contact time, and temperature on dye removal capacity are examined. The research findings demonstrate that the adsorption capacity is higher in biomass compared to immobilized cells. The highest adsorption capacities are observed at pH 2 for RY18 and AR18, while pH 9 is optimal for BB41. Increasing the adsorbent dosage and initial concentration significantly improves the adsorption capacity. The Langmuir model best describes the adsorption process, indicating that the dye attaches to the biosorbent in a single layer, with a uniform biosorbent surface. The removal of the dye occurs through a chemical process on the biosorbent surface, as evidenced by the pseudo-second-order kinetic model. According to thermodynamic analysis, higher temperatures promote greater adsorption of dyes. Our study shows the effectiveness of Yarrowia lipolyica NBRC1658 as a biosorbent in the removal of a wide range of industrial dyes. [ABSTRACT FROM AUTHOR]

This paper presents the preparation and characterization of bentonite coated with hydroxide double lamellar Mg/Al-bentonite and Zn/Al-bentonite as a potential adsorbent material. The coating process involved co-precipitation of mixed metal nitrate solution (Mg-Al) or (Zn-Al), followed by immersion of bentonite (B-Na+) dispersion. The structures and morphologies of the coated bentonites were characterized using XRD, FTIR, BET, and SEM analysis. The results of the BET analysis indicate that Mg/Al-bentonite and Zn/Al-bentonite have larger surface areas and pore volumes compared to bentonite alone. Specifically, the surface area of Mg/Al-bentonite is 209.25 m2/g with a pore volume of 0.423 cm3/g, while Zn/Al-bentonite has a surface area of 175.95 m2/g and a pore volume of 0.313 cm3/g. In contrast, the surface area and pore volume of bentonite alone are 110.43 m2/g and 0.132 cm3/g, respectively. The Mg/Al-bentonite reaches 85% uptake within 3 h (equivalent to 724.20 mg/g at 25 °C and pH 7), achieving rapid equilibrium. In contrast, the Zn/Al-bentonite achieves a maximum adsorption of 74% within 5 h under identical pH and temperature conditions, corresponding to 650.34 mg/g. The error function values, including the correlation coefficient R2, chi-square test χ2, and residual sum of squares RSS, were calculated to evaluate both kinetic and isotherm models. The kinetic adsorption data agreed well with a pseudo-second-order model. The adsorption process followed the Sips isotherm model, and the monolayer adsorption capacity of Mg/Al-bent and Zn/Al-bent composites was 872.41 (R2 = 0.974) and 678.45 mg/g (R2 = 0.983), respectively. The thermodynamic analysis of the adsorption process revealed that it occurred spontaneously with an endothermic characteristic. The parameters ΔS, ΔH, and ΔG were used to determine this. [ABSTRACT FROM AUTHOR]

In this study, a cross-linked chitosan-epichlorohydrin/nanosilica (CS-EPH/NSi) bionanocomposite was prepared using a simple two-step process. First, functionalization of chitosan with nanosilica followed by crosslinking process with epichlorohydrin. The CS-EPH/NSi bionanocomposite's adsorption property toward the removal of reactive orange 16 (RO16) dye was evaluated. The adsorption process of RO16 by CS-EPH/NSi was optimized using Box-Behnken design (BBD). The desirability function results revealed that the highest removal of RO16 (96.32%) is achieved at the following experimental conditions: solution pH of 4.26, dosage of CS-EPH/NSi = 0.089 g/100 mL, and contact time of 9.69 min. The Langmuir isotherm model was found to describe the equilibrium behavior of the monolayer adsorption process at 25 °C. The kinetics data of RO16 adsorption by CS-EPH/NSi were appropriately described by a pseudo-second order model, which suggests that the adsorption process occurs via chemisorption. The high adsorption capacity of CS-EPH/NSi for RO16 (110.2 mg/g) can be attributed to the electrostatic forces between the positively charged CS-EPH/NSi and the negatively charged RO16 anions, as well as n-π and H-bond interactions. Overall, this study demonstrates the potential of CS-EPH/NSi as an adsorbent for the efficient removal of textile RO16 dye. [ABSTRACT FROM AUTHOR]

This study presented a facile synthesis route via the precipitation method for the production of magnetic biochar from oil palm frond (OPF). The physicochemical characteristics including surface, functional, and magnetic properties of the synthesized magnetic biochar revealed that the surface morphology, porosity, and magnetic properties enhanced its adsorption capacity for the removal of crystal violet (CV) and sunset yellow (SY) from aqueous solution. The saturation magnetization of OPF biochar was found to be 8.41 emu/g, coercivity (Hc) of 83.106 G, and retentivity (Mr) of 1.475 emu/g which implies that OPF magnetic biochar can be facilely separated from aqueous solution. The result also demonstrated superparamagnetic properties which provided suitable magnetic responsive characteristics to an external magnetic field. The interactive effect of the operational conditions of pH, adsorbent dosage, initial concentration, and temperature was investigated in a batch adsorption study using the central composite design (CCD) of the response surface methodology (RSM). It was indicated that an increase in adsorbent dosage to 1.0 g/L at a lower initial concentration (50 ppm) conducted at 20 °C favoured optimum removal of CV and SY at pH 11 and 4, respectively. The Langmuir isotherm model with maximum adsorption capacity ( q max ) of 149.03 and 342.47 mg/g was achieved for CV and SY dyes, respectively. The kinetic data proved to be best fitted to the pseudo-second-order kinetic model. Thermodynamic parameters revealed spontaneous and endothermic reactions. The suitability and sustainability of the magnetic biochar were enhanced by its regeneration potential for effective adsorption of CV and SY after 5 cycles which indicates its outstanding reusability. Hence, OPF magnetic biochar exhibited prospective application for the removal of dyes from wastewater. [ABSTRACT FROM AUTHOR]

Magnetic core–shell Fe3O4@SiO2 nanoparticles were synthesized by sol–gel method. Based on the characterization and experimental results, the adsorbent was found to have an average particle size of approximately 120 nm, a pore size range of 2–5 nm and superparamagnetic properties. It exhibited electrostatic and hydrogen bonding interactions during adsorption of methyl orange (MO). The adsorption of MO on the magnetic Fe3O4@SiO2 nanoparticles exhibited pseudo-second-order kinetics, the adsorption process is a spontaneous endothermic adsorption process, which conforms to the Langmuir adsorption isotherm model. he maximum amount of MO was adsorbed at pH = 2, T = 45 °C and t = 30 min, and the highest adsorption capacity was 182.503 mg/g; The unit adsorption capacity of the Fe3O4@SiO2 nanoparticles still reached 83% of the original capacity after 5 cycles, so the material was reusable and met the requirements of environmental protection. This study reveals the great potential of magnetic mesoporous nanoparticles for removal of dyes from wastewater. [ABSTRACT FROM AUTHOR]

Yttria‐stabilized zirconia (YSZ), although well known for a lot of excellent engineering applications, has limited footprints in the field of adsorption/dye removal. Through this work, we demonstrate the remarkable efficacy (adsorption capacity ∼550 mg/g) of 8 mol.% YSZ nano‐adsorbents for toxic azo‐dye (e.g., Congo red) removal. The consistency of our adsorption experiments was validated with the help of a series of tests, such as regeneration (via thermal and chemical routes), in real‐life river water, with mixed ion solution, and under varied pH (3–11). Noteworthy is also that the commercial trademark composition (with the same dopant concentration) showed little/no adsorption. Our success of the adsorption experiments is credited to the multitude of factors, namely, size refinement ∼6 nm, retainment of phase‐pure cubicity, and enhanced surface area (155 m2/g), which eventually led to the generation of massive oxygen vacancies on our synthesized doped‐zirconia surfaces. [ABSTRACT FROM AUTHOR]

A comprehensive study combining experimental, computational, and field experiments was conducted to find out the most suitable catalysis method to assist industries using Congo red dye to get rid of this waste from industrial wastewater in Beni-Suef area. The adsorption potential of kaolinite, Liagora farinose (Egyptian marine macroalgae) and kaolinite modified by Liagora farinose macroalgae assessed for the removal of Congo red dye from aqueous solutions. The kaolinite/alga nano-composite with a crystal size of 40 nm was fabricated using a wet impregnation technique. Our results indicate that surface modification of kaolin with Liagora farinose results in an obvious increase in adsorption of toxic dye for nano-composite than individuals. Batch experiments were applied and both kinetics and isotherms of Congo red dye adsorption were also explored in order to find out the influence of different experimental factors. Congo red removal percentage is highly affected by adsorbent dose, working temperature, and pH value. The best temperature for Congo red adsorption onto kaolinite/alga nano-composite is 40°C at pH > 7. The maximum adsorption capacities were found to be 5.0, 7.0 and 10 mg/g for kaolinite, alga and kaolinite/alga nano-composite, respectively. Computational simulations studies have shown that the adsorption of the Congo red molecule on Kaolinite surfaces is exothermic, energetically favourable and spontaneous. Congo red adsorption on kaolinite/alga nano-composite is well handled with the first-order diffusion model, while kaolin and Liagora farinose follow two different kinetic adsorption models depending on the Congo red dye concentration. Finally, the field tests showed optimistic results with nearly 94% efficiency for kaolinite/alga nano-composite in removing mixed dyes from industrial wastewater, which in turn verified the foundation of new eco-friendly nano-adsorbents to help reuse industrial wastewater. [ABSTRACT FROM AUTHOR]

This present study investigated the adsorption characteristics of rock melon skin (RMS) as a promising adsorbent for the removal of toxic brilliant green (BG) dye. The functional group and surface morphology analyses were carried out to characterise the adsorbent. The RMS-BG equilibrated within 30 minutes of contact time and showed stability under the pH range (4–10) studied. Adsorption of BG was not only unaffected but was enhanced in the presence of NaCl. Adsorption isotherm data analysed using six isotherm models, namely Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Redlich-Peterson and Sips, pointed to the Freundlich being the best model. The maximum adsorption capacity (qmax) of 118.0 mg g−1, based on the Langmuir model, was higher when compared to some reported natural and chemically modified adsorbents. Adsorption of BG onto RMS obeyed the pseudo second order kinetics (R2 = 0.9976). Thermodynamics studies indicated the adsorption process was endothermic in nature. The spent RMS was able to be regenerated and reused whilst maintaining high adsorption of >95% BG even at the 5th cycle when base treatment was used. Comparison of linear and non-linear analyses indicated that the kinetics data fitted better with non-linear regression method whilst adsorption isotherm was better suited using linear regression method. The above findings demonstrate the potential application of RMS as a low-cost effective adsorbent for the removal of BG dye in wastewater treatment. [ABSTRACT FROM AUTHOR]

The present study is focussed on the adsorptive removal of Crystal violet dye from laboratory polluted water using Alysicarpus vaginalis plant material based hybrid multifunctional nanocomposite which was prepared by following co‐precipitation method. The prepared composite MnFe2O4/AV has been characterised using FT‐IR, SEM‐EDX, TEM, XRD, BET, TGA techniques. The nanocomposite has been investigated for its antioxidant activity. The MnFe2O4/AV has been found possessing numerous functional groups on its porous surface and the sorption efficiency was evaluated in terms of parameters, such as sorbent dosage, concentration of the dye, contact time and pH of solution. The maximum adsorption capacity has been obtained as 34.211 mg g−1 and the process was found to be feasible and endothermic in nature. The data fitting showed that the sorption followed pseudo‐second order kinetics. From the sorption data fitting it was found that the sorption followed the Freundlich isotherm. Thus, the MnFe2O4/AV composite proved to be economical to synthesise which is eco‐friendly and has antioxidant ability, thus multifunctional in nature. [ABSTRACT FROM AUTHOR]

Herein, for the first time, a simple, green, direct immersion immobilisation method is reported for graphene oxide (GO) nanosheets using pomelo peel (PL) as a substrate. A GO/PL porous sponge was successfully prepared and used to remove methylene blue (MB) from dye wastewater. Considering the porosity, hydrophilicity and elasticity of the PL, the PL was placed in a GO aqueous suspension through direct immersion immobilisation. The carboxyl and hydroxyl groups in the peel could effectively capture and immobilise the GO nanosheets. GO was adsorbed into the PL pores and dispersed throughout the PL. Finally, the prepared super-hydrophilic and elastic GO/PL exhibited excellent adsorption performance towards MB in dye wastewater. The adsorption results revealed that the adsorption behaviour was consistent with the Langmuir isotherm and quasi-secondary kinetic models. The maximum equilibrium adsorption capacity of GO/PL towards MB was 124.2 mg/g, exceeding the values obtained for most of the previously reported adsorbents. Moreover, after five consecutive adsorption–desorption cycles, GO/PL retained 75% of its initial adsorption capacity. Mechanistic analysis revealed that pore filling, electrostatic attraction, ion exchange and hydrogen bonding interactions are the primary driving forces facilitating MB adsorption. [ABSTRACT FROM AUTHOR]

It is critical to remove dyes from wastewater as they cause harm to human and aquatic life due to their carcinogenic, toxic, and mutagenic effects. Here, low-cost activated carbons (CPs) were produced from the date (Phoenix dactylifera L.) pits. The prepared CPs were chemically activated utilizing zinc chloride to obtain activated carbons from date pits (ZCPs). The physicochemical properties, chemical composition, and morphology of ZCPs material and the active surface functional groups involved in adsorption were identified using N2 adsorption–desorption isotherm, scanning electron microscopy, point of zero charges (pHPZC), and Fourier transforms spectroscopy. The ZCPs biocomposite was applied for the Brilliant green (BG) removal from aqueous solutions, where the efficiency was assessed as functions of pH value, foreign ions, the initial dye concentration, dose of adsorbent, adsorption time, and temperature. The outcomes showed that the prepared ZCPs biocomposite exhibited high uptake of BG with a qe of 247.752 mg/g. The isotherm and kinetic studies show that the adsorption process of BG dye onto ZCPs biocomposite followed Langmuir, and pseudo-second-order models, respectively. From the estimated thermodynamic functions, it was found that the nature of the BG dye adsorption process onto the prepared ZCPs adsorbent was endothermic and spontaneous. With a relative standard deviation of less than 3%, the prepared ZCPs were successfully applied for the removal of BG from real water samples with a recovery of more than 90%. The plausible mechanism of BG adsorption onto the prepared ZCPs can be assigned to various interactions, such as pore–filling, electrostatic attraction, H-bonding, and π–π stacking. [ABSTRACT FROM AUTHOR]

Pistachio nutshells-derived biochar (PNS-BC) was utilized as a cost-effective adsorbent for competently removing a model dye, methyl orange (MO) from wastewater. Three concentrations of TiO2; 1%, 2%, and 3% were used to decorate the biochar. Analysis of morphology, stability, and structure of the three adsorbents (PNS, PNS-BC, and the TiO2 functionalized biochar; TiO2@PNS-BC) was extensively explored using various characterization techniques. The synergistic photocatalytic-adsorptive efficiency of the three adsorbents was compared. In this regard, a Box-Behnken (BB) design-based multivariate scheme was inaugurated with the target of maximizing MO removal (%R) while using the minimum possible of chemicals and resources. The impact of five variables; %TiO2, dose of TiO2-PNS, reaction time, dye concentration, and pH on the magnitude of %R was investigated. Results show that 97.69% removal of MO could be recognized over 120 min using adsorption compared to 99.47% removal over 30 min using 3% TiO2@PNS-BC as a photocatalyst. A 3% TiO2@PNS-BC was the best catalyst (compared to 1% and 2%) with a decolorization rate constant of 0.12741 min−1, ~ 1.5 × faster compared to the decolorization of MO using adsorption alone. Adsorption of MO conformed well to Langmuir isotherm. A maximum adsorption capacity (qmax) of 142.38 mg/g was achieved. Adsorption kinetics fitted well with the pseudo-second order (PSO) model. Results obtained indicated that biochar of PNS is a promising, cost-effective, and economical adsorbent. [ABSTRACT FROM AUTHOR]

In order to develop a novel and cost-effective adsorbent with outstanding adsorption capacity and excellent recyclability for anionic pollutants, the chitosan-modified cetyltrimethylammonium bromide sorbent (CS@CTAB) was fabricated. Fourier-transform infrared spectroscopy, N2 adsorption–desorption isotherm, elemental analysis, Thermogravimetric analysis, X-ray diffraction, and Scanning electron microscopy have been applied to evaluate both raw and surfactant modified chitosan (CS@CTAB). Azorubine, Sunset Yellow, and hexavalent chromium were used to study the adsorption behavior of CS@CTAB under various parameters such as adsorbent dose, initial dye and metal ion concentration, contact time, and temperature. Adsorption equilibrium, kinetics models and thermodynamic parameters were investigated. The adsorption isotherm fitted well with the Langmuir isotherm model, with a maximum adsorption capacity of 492.6 mg/g, 492.6 mg/g, and 490.196 mg/g for Azorubine, Sunset Yellow, and Hexavalent Chromium, respectively. The kinetic studies showed that the pseudo-second-order model provided a better correlation between experimental data. Furthermore, the calculated thermodynamic parameters confirmed that the adsorption of Cr(VI), E110, and E122 by CS@CTAB material is a spontaneous and exothermic process. The fabricated CS@CTAB adsorbent was employed for the efficient elimination of Azorubine, Sunset Yellow, and hexavalent chromium from real water samples, synthetic mixtures, and colored soft drinks, with a percentage of recovery of ~ 96%. The plausible adsorption mechanisms of Azorubine, Sunset Yellow, and hexavalent chromium on the surface of CS@CTAB are elucidated. The adsorption anticipated to be due to electrostatic interaction and hydrogen bond formation for hexavalent chromium; while the adsorption of Azorubine and Sunset Yellow, was assumed to be due to electrostatic interaction, hydrogen bonding, and n-π interaction. Finally, the study demonstrates the efficiency of CS@CTAB for the removal of anionic species from several samples, including natural water and colored beverages. [ABSTRACT FROM AUTHOR]

Discharging untreated dye-containing wastewater gives rise to environmental pollution. The present study investigated the removal efficiency and adsorption mechanism of Acid Red 18 (AR18) utilizing hexadecyl-trimethyl ammonium chloride (HDTMA.Cl) modified Nano-pumice (HMNP), which is a novel adsorbent for AR18 removal. The HDTMA.Cl is characterized by XRD, XRF, FESEM, TEM, BET and FTIR analysis. pH, contact time, initial concentration of dye and adsorbent dose were the four different parameters for investigating their effects on the adsorption process. Response surface methodology-central composite design was used to model and improve the study to reduce expenses and the number of experiments. According to the findings, at the ideal conditions (pH = 4.5, sorbent dosage = 2.375 g/l, AR18 concentration = 25 mg/l, and contact time = 70 min), the maximum removal effectiveness was 99%. The Langmuir (R2 = 0.996) and pseudo-second-order (R2 = 0.999) models were obeyed by the adsorption isotherm and kinetic, respectively. The nature of HMNP was discovered to be spontaneous, and thermodynamic investigations revealed that the AR18 adsorption process is endothermic. By tracking the adsorption capacity of the adsorbent for five cycles under ideal conditions, the reusability of HMNP was examined, which showed a reduction in HMNP's adsorption effectiveness from 99 to 85% after five consecutive recycles. [ABSTRACT FROM AUTHOR]

This work emphasizes the efficiency of the response surface design to optimize the parameters affecting the removal of a textile dye—Direct Red 81 (DR-81)—by biosorption on seafood waste, namely, cockleshells (CS). The adsorbent was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis of surface and pH points of zero charge (pHpzc). A Box–Behnken design (BBD) with three factors was used to optimize the experimental conditions. After the experiment and data analysis, the optimal conditions found were 1 g of adsorbents, 10 mg/L of initial dye concentration, and a pH of 2 in the adsorbate solution, with the highest removal efficiency of 99.98%. The experimental results were analyzed by the ANOVA test, and they demonstrated the acceptability of the quadratic regression model. The adjusted determination coefficient R2 (adj) was equal to 98.82%, indicating an excellent relationship between the predicted and experimental responses. Langmuir isotherms were determined to be the best-fitting model, and the maximum adsorption capacity was 4.65 mg/g. The adsorption process was endothermic and fit the pseudo-second-order model. The negative values of ∆H and ∆S in the thermodynamic research showed that the bio-adsorption technique for the removal of Direct Red 81 is exothermic, spontaneous, and feasible. In addition, the negative value of ∆G indicates that the adsorption mechanism occurs at solid–liquid interfaces with an increasing number of species. [ABSTRACT FROM AUTHOR]

Water pollution remains a global problem that urges researchers to develop new technologies aimed at environmental restoration. Here, this study aimed at obtaining an activated biochar from pequi almonds for dye removal. Before and after adsorption, the materials underwent characterization using techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TG). The biochar from the pequi almond was called BA, and the activated biochar from the pequi almond was called ABA. The influence of the pH, contact time, and adsorbate concentration on adsorption was investigated using the dye methylene blue. The morphological assessment revealed higher cracks and pores in the ABA than in the BA. The TG showed that the BA lost approximately 19% more mass than the ABA, indicating that activation occurred. The activation contributed to the decrease in the degree of disorder in the BA because of the increased number of graphitic carbon atoms (ordered) in the ABA, as observed via Raman. The adsorption kinetics followed a pseudo-second-order model, while the adsorption isotherms followed the Langmuir model. The BA adsorption capacity was 500.00 mg g−1, constituting a robust solution for dye removal from aqueous environments. Therefore, this implies the success of the process. [ABSTRACT FROM AUTHOR]

Methylene blue (MB) and basic red 9 (BR9) are cationic dyes that are commonly used in the dye industry and negatively affect humans and other living organisms. This study compares the performance of Indonesian rice husk (IRH) and Hungarian rice husk (HRH) as bio-adsorbents for removing MB and BR9 from aqueous solutions. Chemical content, zeta potential, and Fourier-transform infrared spectroscopy analyses were used to characterize the rice husks (RHs). Adsorption studies were performed through batch experiments involving several parameters, namely, pH, adsorbent dose, initial dye concentration, contact time, and temperature to observe the self-association (aggregation) of MB and BR9. Adsorption kinetic studies showed that maximum dye removal was achieved at a contact time of 120 min. MB and BR9 adsorption followed a pseudo-second order kinetic model, and the BET multilayer isotherm model provided a better fit to the experimental data of MB and BR9 adsorption. The IRH adsorption capacities were 15.0 mg/g for MB and 7.2 mg/g for BR9, whereas those of HRH were 24.4 mg/g for MB and 8.3 mg/g for BR9. Therefore, these RHs are potential bio-adsorbents for removing MB and BR9 from aqueous solutions. [ABSTRACT FROM AUTHOR]

Developing porous organic polymers (POPs) as efficient adsorbents for wastewater treatment began a new era in environmental remediation. In the current paper, an amine-rich triazine-based POP with excellent flexibility, denoted as MDA-POP, was synthesized using a facile method from accessible building blocks. The prepared MDA-POP was thoroughly characterized using various analytical techniques and its application in removing Congo red and Scarlet 4BS, two widely used textile colors, was investigated. The optimal conditions for the adsorption process were determined by studying different effective parameters, including pH, temperature, adsorbent dosage, and contact time. By optimizing the adsorption conditions, the dye removal efficiency reached up to 99%, with maximum adsorption capacities of 71.43 mg g−1 for Congo red and 136.97 mg g−1 for Scarlet 4BS. The adsorption isotherms of both the dyes were best fitted to the Langmuir model, which indicates monolayer adsorption. Moreover, the study on the kinetic aspects of adsorption shows that the pseudo-second-order model is the best model for describing the adsorption process; thus, the chemical interactions play a vital role in the rate-determining step of the adsorption. The thermodynamic studies show that the standard enthalpies of adsorption (ΔH°) are −178.8 kJ mol−1 for Congo red and −75.4 kJ mol−1 for Scarlet 4BS, indicating that the nature of adsorption is chemisorption. Also, the negative standard free Gibb's energy (ΔG°) values reveal a spontaneous adsorption process. This paper provides a facile and efficient method for synthesizing POPs as adsorbents for water treatment applications. [ABSTRACT FROM AUTHOR]

Adsorption studies of decolorization of Acid blue dye by using novel adsorbents of preformed flocs of Aluminum Sulphate, Ferric Chloride, and Ferrous Sulphate were carried out through non‐flow batch sorption studies. The influence of pH, equilibrium contact time, and floc dose on color removal was studied. Kinetic and equilibrium studies were carried out to know the efficacy of adsorbents in the decolorization of an aqueous solution of C.I. Acid blue 113 dye. In order to probe into the mechanism involved in the decolorization of dye solution, FTIR and SEM studies were conducted. The Langmuir isotherm was well fitted to the equilibrium data implying that there is monolayer formation in the process of sorption. Kinetic data fitted well to pseudo second order which states that chemisorption is the rate limiting step in the adsorption process. The adsorption capacity of preformed flocs of aluminum sulphate, ferric chloride, and ferrous sulphate were found to be 450 mg/g, 500 mg/g, and 125 mg/g. FTIR and SEM studies shows that there is adsorbent‐dye complex formation in the adsorption process of decolorization of Acid dye with preformed flocs. [ABSTRACT FROM AUTHOR]

In this study, chitosan-nanoclay composite beads (CS/NC composite beads) were used to remove Ponceau S from aqueous solutions. CS/NC composites characterization was performed with FTIR, SEM-EDX, TGA, BET and XRD analyzes. The adsorption procedure was optimized by changing various parameters in batch experiments such as pH, dye concentration, contact time and temperature. Ponceau S adsorption took place at a higher rate in the acidic region, and the highest adsorption was observed at pH 2.0. The amount of adsorbed dye increased as the temperature increased at low dye concentrations and the time required to reach equilibrium was shorter than at higher dye concentrations. Linear and non-linear forms of Langmuir, Freundlich and Temkin adsorption models were applied. The adsorption behavior of Ponceau S is compatible with the linear Langmuir model, and the maximum adsorption capacity was found to be 140.85 mg g-1. Linear and nonlinear forms of adsorption kinetics and thermodynamic parameters were investigated for dye concentrations of 150-400 mg/L. The adsorption kinetics fit the linear pseudo-second-order kinetic model and the Ponceau S adsorption on CS/NC composites was spontaneous and endothermic. The results show that the CS/NC composites can be used as an effective adsorbent in industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

In this study, the synthesis process of TiZnPbO nanocomposite and its use for the removal of Basic Fuchsin (BF) dye from wastewater was studied. The influence of contact duration (90 min), concentration (200 mg/L), solution pH (3.0), and adsorbent dosage (0.2 g) on adsorption studies were thoroughly examined. The kinetic models (pseudo‐first‐order and pseudo‐second‐order) and isotherm models (Langmuir and Freundlich) are used to understand the adsorption mechanism and behavior of BF over adsorbents. According to the kinetic data, the models fit a pseudo‐second‐order equation which is an indication of a heterogeneous chemisorption process. The Langmuir isotherm is best fitted with R2 of 0.999 and a maximum adsorption capacity of 208.33 mg/g. It was determined that the values of n for the adsorption of BF on TiZnPbO at 298 K were less than unity (n=0.516, 0.504, and 0.501). This finding showed that the BF dyes should be adsorbed on this adsorbent in a non‐parallel orientation. As for BF adsorption on TiZnPbO, the isotherm data indicated that it behaved more like a multilayer than a monolayer. The TiZnPbO adsorbent showed high recyclability at least 5 times. [ABSTRACT FROM AUTHOR]

To address the challenges associated with the weak affinity and difficult separation of biochar, we developed chitosan–biochar hydrogel beads (CBHBs) as an efficient solution for removing reactive brilliant blue (RBB KN-R) from wastewater. The adsorption behavior and mechanism of RBB KN-R onto CBHBs were extensively studied. Notably, the adsorption capacity of RBB KN-R showed pH-dependence, and the highest adsorption capacity was observed at pH 2. The adsorption process was well fitted with the pseudo-second-order kinetic model and the intraparticle diffusion model. Film diffusion and intraparticle diffusion were both responsible for the adsorption of RBB KN-R onto CBHBs. At 298.15 K, the maximum adsorption capacity qm was determined to be 140.74 mg/g, with higher temperatures favoring the adsorption process. A complex mechanism involving π–π interactions, electrostatic attraction, hydrophobic interaction, and hydrogen bonding was found to contribute to the overall adsorption process. The experimental data discovered the coexisting substances and elevated ionic strength hindered the adsorption capacity. Significantly, after three cycles of adsorption–desorption, the CBHBs maintained an adsorption capacity above 95% for RBB KN-R. These promising results imply that CBHBs are a durable and cost-effective adsorbent for efficient removal of dyes from wastewater. [ABSTRACT FROM AUTHOR]

Al doped ZnO multifunctional thin films (AZO) were successfully prepared by sol-gel method on small porous ceramic substrates. The effects of Al doping on the microstructural, morphological, optical and photocatalytic properties of the films were investigated. The XRD analysis detected the polycrystalline structure with wurtzite-type for all synthesized samples. The grain size was found to vary between 20 nm and 30.8 nm. UV-Visible absorbance data indicated that all AZO films absorb visible light at around 485 nm. In addition, a blue shift toward shorter wavelengths side was noted with increasing Al content up to 5%, while the band gap showed an increasing trend achieving 3.28 eV. SEM analysis showed that Al dopants greatly affected the morphology of ZnO samples. Moreover, Al doping was found to enhance the adsorption capacity of ZnO for OII dye up to 37%, which accelerated the photodegradation process of the samples. The highest value of the color removal efficiency of residual dye molecules, 78.5%, was observed for AZO (5% Al). The highlighted results indicated that the sol-gel dip coated AZO films are attractive and suitable for water treatment through both photocatalytic and adsorption activities. [ABSTRACT FROM AUTHOR]

O‐Carboxymethyl chitosan (O‐CM‐chitosan) hydrogel, prepared in our previous study, was investigated in this work for the first time as adsorbent for Basic Red 12 (BR 12) dye. With rising temperature (from 25°C to 55°C) and decreasing solution pH (from 9 to 4), a lowering in both adsorption capacity (from 703.47 to 400.79 mg/g) and removal efficiency (from 70.34% to 40.08%) was observed. A significant increase in adsorption capacity (from 342.75 to 621.39 mg/g) was observed with increasing initial dye concentration (from 400 to 1000 mg/L), while a decrease in removal efficiency (from 85.69% to 62.14%) was noted. Pseudo‐second‐order model fitted well the adsorption. Isotherms of adsorption conform to Langmuir model with a maximum monolayer adsorption capacity of 625 mg/g. The value of ∆H° (−23.99 kJ/mol) implied exothermic nature of adsorption process. Values of ΔG° indicated that the adsorption was spontaneous at low temperature and nonspontaneous at high temperature. The value of activation energy is equal to 13.071 kJ/mol. The dye removal percentage from the hydrogel was 88% at the first cycle. Thus, O‐CM‐chitosan hydrogel has promising and effective properties for removing BR 12 and similar dyes from aqueous media. [ABSTRACT FROM AUTHOR]

The present study focuses on investigating the adsorption characteristics of anionic Congo Red (CR) and Indigo Carmine (IC) dyes using hexadecyltrimethyl ammonium bromide‐modified Bentonite (HDTMA‐Bentonite) with varying loading amounts. The removal effectiveness of anionic dyes was examined as a function of the HDTMA+ loaded amount, contact time, initial concentration, and adsorbent dosage. The XRD data revealed that the interlayer spacing of Bentonite increased from 1.42 to 1.98 nm. The FTIR approach was used to analyze the surface modification of hybrid Bentonite; however, the hydrophobic nature of hybrid Bentonite was confirmed by ATG measurements. A kinetic investigation of sorption was done. The results demonstrated that the pseudo‐second‐order model fitted the adsorption kinetic data better than the pseudo‐first‐order rate equation, and that the amount of HDTMA+ loaded affects the adsorption capacity. According to the Weber‐Morris intra‐particle diffusion equation, the CR and IC dyes diffused faster as the amount of added cationic surfactant rose from 0 % to 100 % of the CEC value. Temkin and Langmuir equation is found to best represent the equilibrium data for two dye‐HDTMA‐B systems. Hybrid Bentonite was regenerated by NaOH, and reused without a significant decrease in its sorption efficiency, supporting the prosperity of its utilization as an effective adsorbent against toxic dyes from wastewater. [ABSTRACT FROM AUTHOR]

To improve the adsorption capacity of SBP, an idea of adding the functional carboxylic groups using multivariant organic acids was raised and tried. Quaternary phosphonium bromide and maleic anhydride modified sugar beet pulp (PMSBP) was prepared by quaternary phosphonium modification on the basis of maleic anhydride-modified sugar beet pulp (MSBP). Characterization results showed that the thermal stability of PMSBP was improved compared to MSBP, and the surface of PMSBP showed uniform layered structure with large pores. The effects of temperature, reaction time, pH, and adsorbent dosage on the adsorption of two dyes by PMSBP were investigated. The adsorption of PMSBP on methyl orange (MO) fitted well with the Langmuir isotherm model and the pseudo-second-order kinetic model, and the Freundlich isotherm model could better describe the adsorption process of PMSBP on methylene blue (MB). The adsorption of MB and MO by PMSBP was exothermic and spontaneous. PMSBP was demonstrated to satisfy the essential requirement for application in wastewater treatment. Electrostatic attraction and ion exchange were speculated as the main adsorption mechanisms. So, the broom modification theory of bio-sorbents was practical and offered a way to improve bio-sorbents adsorption capacity. [Display omitted] • We managed reusage of sugar beet pulp and improved its added value. • We improved adsorption performance of sugar beet pulp by multifunctional modification. • Modified sugar beet pulp could remove about 85 % of dyes in 2.5 h. • Modified sugar beet pulp had a decent regeneration performance. [ABSTRACT FROM AUTHOR]

Chitin-based activated carbon (CAC) was prepared by a two-step process of carbonization and potassium carbonate chemical activation. The CAC was characterized using scanning electron microscopy (SEM), N2 adsorption/ desorption, Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The adsorption performance of CAC for Orange II (O II) was evaluated in terms of contact time, adsorption temperature, initial concentration, adsorption kinetics, adsorption isotherms, and thermodynamics. The CAC had a surface area of 1320 m² g -1 and a total pore volume of 1.10 cm³ g -1 . The maximum monolayer adsorption capacity was 1010 mg g-1 at 318.2 K for O II, respectively. Equilibrium isotherms showed that the Langmuir model had a higher coefficient of determination than the Freundlich model. The thermodynamic results indicated that the adsorption process of O II onto CAC 800 was spontaneous and endothermic. Given the results of this work, CAC can be used as an efficient adsorbent for the removal of dyes from wastewater. [ABSTRACT FROM AUTHOR]

In this study, the removal of diazo and tetra-azo dyes using calcined kaolin were compared. Direct red-28 (DR-28) and Direct black-22 (DB-22) was chosen as diazo and tetra-azo dyes, respectively. The kaolin obtained from Turkiye and calcined at 200 °C was found to be the most efficient adsorbent. Natural and calcined kaolins were characterized using SEM-EDS, FTIR, TGA, and XRD. The parameters such as, calcination temperature of the kaolin, adsorbent amount, temperature, initial pH, contact time, and initial concentration were studied. It was found that the removal rate of DR-28 was higher than that of DB-22 at the studied conditions. The removal of DR-28 and DB-22 were found to be 90.1% and 46.2% under the following conditions: adsorbent amount: 1.2 g/200 mL, initial concentration: 20 mg/L, original pH, temperature: 20 °C and contact time 120 min. The adsorption of the dyes was fitted to Langmuir isotherm model. The maximum adsorption capacity of calcined kaolin at 200 °C was determined as 5.39 and 3.5 mg/g for DR-28 and DB-22, respectively. The adsorption of DR-28 and DB-22 followed a pseudo-second order model. The thermodynamic study showed that the adsorption of DB-22 onto calcined kaolin was endothermic while that of DR-28 was exothermic. [ABSTRACT FROM AUTHOR]

The study's aim was to develop a novel sorbent for removing the color Congo red (CR) from water by precipitating (Mg/Al)-layered double hydroxide (LDH) at the nanoscale onto the waterworks sludge surface as a byproduct. To achieve an effective sorbent with the removal of over 91.19%, The utilization of nanoparticles, the addition of 1 g of sludge to 50 mL of water, and a molar ratio of 2 (Mg/Al) were the optimal production conditions for sorbent. In batch experiments, the optimal operating parameters were found to be 0.5 g of adsorbent in 50 mL of CR, pH of CR solution equal to 3, and a contact time of 3 hours at 200 rpm with 25 mg/L dyes. According to the study, the adsorption capacity was 23.576 mg/g. Additionally, the pseudo-second-order and Langmuir models provided accurate descriptions of the sorption data. [ABSTRACT FROM AUTHOR]

In this study, neodymium/alginate (Nd/Alg) beads were prepared to removal of Congo Red (CR) and Brilliant Blue G (BBG) dyes from aqueous solution and the adsorption potentials of these dyes were investigated. For this, Nd/Alg beads prepared using crosslinking were characterized by FTIR, SEM–EDS and TGA. For the adsorption of CR and BBG dyes, the effects of various parameters including the amount of Nd in adsorbent (bead), pH, contact time, adsorbent amount, initial dye concentration and temperature were investigated. The optimum conditions for the effective removal of CR and BBG dyes were determined as Nd amount in bead: 3%, pH: 7, contact time: 60 min, bead amount: 15 mg, initial dye concentration: 25 mg/L and temperature 298 K. Adsorption isotherm studies (Langmuir and Freundlich isotherms) and kinetic studies (pseudo-first-order and pseudo-second-order) were carried out under optimum conditions. The adsorption data were found to completely follow Langmuir model for CR and BBG dyes. The maximum adsorption capacities were found to be 46.03 mg/g for CR and 25.25 mg/g for BBG under optimum conditions. The adsorption kinetic data of both dyes were found to be compatible with pseudo-first-order and adsorption processes were explained by intraparticle diffusion. According to thermodynamic studies, nature of adsorption reaction was spontaneous, exothermic and increasing randomness for both dyes. As a result, it can be concluded that Nd/Alg beads obtained with a natural polymer have low cost and high efficiency and even small amounts of these beads have high potential for treatment of high concentration dye wastewater. [ABSTRACT FROM AUTHOR]

Dye effluent discharged into the environment can cause serious pollution and damage to the environment. It is crucial to develop adsorbents with excellent adsorption capacity and stable regeneration to meet practical application requirements for the treatment of dye-bearing wastewater. Herein, MoS2 nanoparticles were confined inside a cellulose aerogel to prepare a larger nanocomposite adsorbent (denoted as CAM) for efficient Congo Red (CR) removal from water. Chemical and morphological features of the CAM were examined using XPS, FTIR, XRD, SEM, and HRTEM, while CR adsorption on the nanocomposite was systematically investigated through batch experiments. The CR adsorption process was well described using the Langmuir model, with the maximum adsorption capacity calculated as 334.92 mg/g. The kinetic study illustrated that CR adsorption onto the CAM followed the pseudo-first-order model, and the dye diffusion process into the aerogel was the rate-limiting factor. The hybrid material exhibited excellent CR adsorption selectivity and maintained stable adsorption capacity even in the presence of a high concentration of competitive ions. Importantly, the hybrid aerogel was efficiently regenerated with ethanol and reused for dye adsorption in subsequent batches. Based on all of these results, CAM shows promise for the treatment of dye pollutants. [ABSTRACT FROM AUTHOR]

Humic acid is one of the green materials for wastewater treatment including for removal dyes as an adsorbent. Humic acid was isolated from peat soil, Gambut Regency, South Kalimantan following International Humic Substances Society method, and used to adsorb Congo red. The adsorption process was carried out in a batch system and the effect of pH, contact time, and adsorption capacity of Congo red on humic acid were studied. The adsorbent characterization by using FTIR. The results showed that the adsorption of Congo red on humic acid occurred at the optimum pH of pH 6, the optimum contact time was 120 minutes. The adsorption capacity of Congo red onto humic acid of 33.33 mg/g and follows the Langmuir model with R² = 0.9926. The characterization of humic acid functional groups before and after adsorption of Congo red showed that the signal at 1,712.79 cm-1 were shifted to 1,705.07 cm-1 and 1,273.02 cm-1 were shifted to 1,265.30 cm-1. These suggested that the mechanism interaction was the electrostatic interaction between -NH3+ functional group of Congo red group and -COO- functional group of humic acid. It means that humic acid isolated from peat soil could be used as an adsorbent for the removal Congo red. [ABSTRACT FROM AUTHOR]

In order to remove and reuse the ecotoxic dye Eriochrome black T (EBT) from dyeing wastewater, we used a process called cetyltrimethylammonium bromide (CTAB)-assisted foam fractionation. By optimizing this process with response surface methodology, we achieved an enrichment ratio of 110.3 ± 3.8 and a recovery rate of 99.1 ± 0.3%. Next, we prepared composite particles by adding β-cyclodextrin (β-CD) to the foamate obtained through foam fractionation. These particles had an average diameter of 80.9 μm, an irregular shape, and a specific surface area of 0.15 m2/g. Using these β-CD-CTAB-EBT particles, we were able to effectively remove trace amounts of Cu2+ ions (4 mg/L) from the wastewater. The adsorption of these ions followed pseudo-second-order kinetics and Langmuir isotherm models, and the maximal adsorption capacities at different temperatures were 141.4 mg/g at 298.15 K, 143.1 mg/g at 308.15 K, and 144.5 mg/g at 318.15 K. Thermodynamic analysis showed that the mechanism of Cu2+ removal via β-CD-CTAB-EBT was spontaneous and endothermic physisorption. Under the optimized conditions, we achieved a removal ratio of 95.3 ± 3.0% for Cu2+ ions, and the adsorption capacity remained at 78.3% after four reuse cycles. Overall, these results demonstrate the potential of β-CD-CTAB-EBT particles for the recovery and reuse of EBT in dyeing wastewater. [ABSTRACT FROM AUTHOR]

The Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (MNPs) were synthesised using Plantago major seed extract through an environment-friendly, economic, and easy procedure. The nanoparticles were characterised by FTIR, XRD, SEM, TEM, EDX, BET surface area analysis, and VSM. The Ni0.5Zn0.5Fe2O4 MNPs were investigated as a nanoadsorbent for removal of reactive blue 21 (RB 21) and the results showed that the nanoparticles were effective for adsorption of RB 21. More than 93% of RB 21 was removed by the nanoadsorbent after a short time of 10 min (60 mg of nanoadsorbent dosage at concentration of 20 ppm for RB 21). The effect of initial concentration of RB 21 and nanoparticle dosage on dye adsorption were investigated. The Langmuir and Freundlich isotherm models used for adsorption equilibrium of RB 21 on Ni0.5Zn0.5Fe2O4 MNPs. The isotherm studies showed that the Langmuir model (KL = 2.76 L/mg, qmax = 18.08 mg/g) provides more compatible than the Freundlich model and thus RB 21 adsorb on the surface of Ni0.5Zn0.5Fe2O4 MNPs by a mono layer adsorption. The adsorption kinetics studies for the adsorption of RB 21 on Ni0.5Zn0.5Fe2O4 MNPs were conducted using the pseudo first-order, the pseudo second-order, and the intraparticle diffusion models and the results indicated that the pseudo second-order model (qe = 15.19 mg/g) provides more compatible than the other models for the adsorption of RB 21 on Ni0.5Zn0.5Fe2O4 MNPs. The maximum adsorption capacity was determined as 16.65 mg/g. [ABSTRACT FROM AUTHOR]

Dyes are hazardous to public health and the environment. Herein, we synthesized Ti-doped porous SiO2 microspheres utilizing a one-step sol-gel method as an effective adsorbent for the removal of cationic dyes from wastewater. The study of the varying individual parameters such as titanium-silica ratio, pH, adsorbent dose, and dye concentration indicated that the adsorption of methylene blue (MB) by Si3TiO10 microspheres exhibited excellent performance, including a wide range of applications (pH = 4–11), fast adsorption rate (15 min removed 90.8% of MB), high adsorption capacity (215.29 mg/g), excellent selectivity (adsorption capacity toward cationic dyes (98%) and < 5% toward anionic dyes), easy desorption steps, steady performance and multiple cycles (10 times). In addition, the adsorption process of MB by microspheres is consistent with the proposed second-order kinetic model (R2 = 0.999) and Langmuir isothermal model (RL2 = 0.997). With the assistance of FT-IR, XRD, XPS, BET, SEM, and TG-DTG techniques, it was demonstrated that the great pore size (8.15 nm) and large specific surface area (267.97 m2/g) of the microspheres could promote the contact between the active site and MB, thus achieving efficient removal of MB by using hydrogen bonding and electrostatic attraction. Furthermore, the unique spherical mesoporous structure, and the Si-O-Ti bond formed by the Ti doping rather than via simple wrapping and adhesion modification, which also ensured the stability of the microspheres during multiple cycles and the desorption process. [ABSTRACT FROM AUTHOR]

In the present study, an inexpensive bioadsorbent was developed using fish scales treated by a novel alkaline heat treatment process to extract hydroxyapatite. The synthesized glutaraldehyde crosslinked Chitosan@Hydroxyapatite biocomposite was characterized by FT-IR spectroscopy, X-ray diffraction, and SEM-EDS analyses and applied as tunable biosorbent for Orange G dye. To evaluate the efficiency of adsorption, the influence of the initial pH, contact time, and initial dye concentration on the process was investigated. The highest adsorption capacity was 217.466 mg g−1, and the adsorption experimental results for OG dye molecules matched well with the pseudo-second-order and Langmuir isotherm models. Concerning the thermodynamic parameters, the ∆G and ∆H values confirm the spontaneous and exothermic character of the adsorption process. Additionally, FT-IR spectroscopy revealed that the OG adsorption occurs through hydrogen bonding and electrostatic interaction between the free hydroxyl and amino groups present on the biocomposite surface and the sulfonate groups in the OG molecules. Response surface methodology based on Box–Behnken design (RSM-BBD) was applied to optimize the effects of the main input factors to remove OG dye. An optimum OG dye removal efficiency of 92% was obtained at 12.5 mg adsorbent dose, 50 mg L−1 dye concentration, and 120 min contact time. CT-GA@HAp hybrid was successfully regenerated up to the fifth cycle, indicating that it can be used as a promising, feasible and environmentally friendly biosorbent composite. [ABSTRACT FROM AUTHOR]

In this study, a carbonate material (CM) and its form heated to 900°C (CM900) were used to remove Congo red (CR) from aqueous solutions. The objective was to combine the results of the characterization of the modified material, CR adsorption and spectroscopic study to propose a coherent mechanism of the CR-CM900 interaction. A bibliographical study on the adsorption of dyes by carbonates and their interactions revealed the scarcity of published works. This study will compensate somewhat for the lack of results in this field. Carbonate materials are abundant, low-cost and available in different countries around the world. The materials were characterized by X-ray diffraction and scanning electron microscopy. A solid/solution concentration of 1 g·L-1, pH of 6.9, equilibrium time of 2 h and temperature of 40°C, were found to be the optimum conditions for a maximum amount of CR adsorbed by CM900 of 288.2 against 32.7 mg·g-1 for CM. A full decarbonation of CM900 results in MgO and CaO, releases CO2 from the structure, and leads to a more porous structure. The pseudofirst-order model adequately described the kinetic data. The experimental isotherms were suitably fitted by the Redlich-Peterson model with determination coefficient and average relative error values =0.97% and <10.0%, respectively. Thermodynamic parameters suggested a spontaneous and endothermic process. Methanol easily desorbed the CR adsorbed by CM900 which maintained its adsorption capacity during three adsorption-desorption cycles. Fourier-transform infrared spectroscopy investigation before and after the dye adsorption showed that the CR-CM900 interaction involves a mechanism of outer-sphere complexation between the amine groups and the hydroxylated magnesium oxides. Understanding the interactions between dyes and carbonate materials is an important approach to develop the use of these materials in wastewater treatment. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) has shown remarkable performance in the multiple-equilibrium-route adsorption (MER) process, which is characterized by further activation of GO through an in-situ reduction process based on single-equilibrium-route adsorption (SER), generating new adsorption sites and achieving an adsorption capacity increase. However, the effect of GO on MER adsorption in lateral size and thickness is still unclear. Here, GO sheets were sonicated for different lengths of time, and the adsorption of MER and SER was investigated at three temperatures to remove the typical cationic dye, acridine orange (AO). After sonication, we found that freshly prepared GO was greatly reduced in lateral size and thickness. In about 30 min, the thickness of GO decreased dramatically from several atomic layers to fewer atomic layers to a single atomic layer, which was completely stripped off; after that, the monolayer lateral size reduction dominated until it remained constant. Surface functional sites, such as hydroxyl groups, showed little change in the experiments. However, GO mainly reduces the C=O and C-O bonds in MER, except for the conjugated carbon backbone (C-C). The SER adsorption kinetics of all temperatures fitted the pseudo-first-order and pseudo-second-order models, yet room temperature preferred the latter. An overall adsorption enhancement appeared as sonication time, but the equilibrium capacity of SER GO generally increased with thickness and decreased with the single-layer lateral size, while MER GO conversed concerning the thickness. The escalated temperature facilitated the exfoliation of GO regarding the adsorption mechanism. Thus, the isotherm behaviors of the SER GO changed from the Freundlich model to Langmuir as size and temperature changed, while the MER GO were all of the Freundlich. A record capacity of ~4.3 g of AO per gram of GO was obtained from the MER adsorption with a sixty-minute ultrasonicated GO at 313.15 K. This work promises a cornerstone for MER adsorption with GO as an adsorbent. [ABSTRACT FROM AUTHOR]

Herein, fabrication of a novel eco-friendly and effective biosorbent (SCB-GO-PAA) nanocomposite were investigated by modification of sugarcane bagasse (SCB) as lignocellulosic biomass with graphene oxide (GO) and polyacrylic acid (PAA) using homogenizer as a new technique to prepare (SCB-GO-PAA) nanocomposite. The fabricated materials were characterized using SEM, FTIR, TGA, and XRD, and were tested to adsorb methylene blue (MB) dye from aqueous solution. Adsorption parameters were studied to investigate the optimum conditions that achieve the higher adsorption capacity. The adsorption processes were carried out according to Langmuir isothermal model and pseudo-second-order kinetic model with maximum sorption capacity of MB-dye by SCB, SCB-GO, and SCB-GO-PAA nanocomposite of 143.56, 265.85, and 543.28 mgg−1, respectively. The results revealed that the fabricated biosorbents are promising materials with considerable adsorption capacity comparing to other novel adsorbents. Also, this eco-friendly and effective bioadsorbent can be utilized on large scale to remove MB-dye from various types of wastewater. [ABSTRACT FROM AUTHOR]

Azo dye wastewater is a common type of organic wastewater that often presents a significant challenge due to its gloomy color, high toxicity, and resistance to degradation. The discharge of such wastewater directly into natural water bodies can pose a severe threat to both ecological security and human health. Traditional biological treatment methods are often ineffective in treating industrial pollutants, but advanced oxidation technologies, such as persulfate (PS), offer unique advantages due to their strong oxidation ability and short reaction times. This study investigates the use of modified biochar (BC) material and catalyzed persulfate advanced oxidation technology to adsorb and separate acid orange 7 (AO7), a common industrial pollutant, from water and further oxidize and degrade it. Wood chips were used as biological templates to create an efficient, eco-friendly, and reusable adsorbent and catalytic material. In this paper, the adsorption effect of Fe3O4@BC on AO7 in water was compared, the adsorption kinetics and isotherm of Fe3O4@BC on different pollutants were studied, and the possible adsorption mechanism was proposed based on the relevant characterization. Adsorption kinetics describes the rate and quality of adsorption by studying the adsorption capacity in the adsorption process. Furthermore, the activated PS system was used to explore the degradation of AO7 at room temperature. First, the catalytic performance of Fe3O4@BC was evaluated by examining the amounts of PS and Fe3O4@BC, the initial pH, the ionic strength, and the reusability of Fe3O4@BC. Then, a possible degradation mechanism was proposed through electron paramagnetic resonance (EPR), free radical quenching experiment, and density functional theory (DFT) analysis. The results of this study suggest that modified biochar material and catalyzed persulfate advanced oxidation technology offer an effective and eco-friendly method for treating AO7 in wastewater. [ABSTRACT FROM AUTHOR]

This work aimed to use Algerian Zean oak (AZO) sawdust in its raw state, without undergoing any physico-chemical treatment, to estimate its efficiency for removing methylene blue (MB), a cationic dye widely used in the textile industry. The physico-chemical properties of the biomaterial were characterized by scanning electron microscopy, Fourier-transform infrared, X-ray diffraction, and Brunauer–Emmet–Teller for measuring its specific surface area. The chemical characteristics of the AZO sawdust surface were further examined by the zero-charge point (pHPZC), iodine, MB numbers, and Boehm titration tests. The batch study was performed by varying parameters such as contact time, particle size, pH, temperature, adsorbent dose, and initial dye concentration. By optimizing these parameters, an adsorption capacity of 52.376 mg/g was attained, at pH = 7 and room temperature, using a dose of 1 g/L AZO at C0 = 20 mg/L for an equilibrium time of 45 min. The adsorption capacity of the MB is enhanced by increasing the initial dye concentration and the biosorbent dose. The kinetic data were modeled using the pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. The results reveal that the pseudo-second-order model better describes the experimental data. Furthermore, the adsorption isotherms well follow the Sips and Langmuir models. The thermodynamic study revealed that the adsorption process of MB on AZO sawdust is a spontaneous, exothermic, and favorable phenomenon. Therefore, AZO sawdust could be considered an efficient biosorbent and a preferred alternative to activated carbon to remove MB. [ABSTRACT FROM AUTHOR]

The presented discovery provides a long-term strategy for successfully utilizing quartz sand (QS) as a low-cost, efficient, and environmentally friendly adsorbent. To improve the adsorption capacity and efficiency, a new chemical strategy was used to coat the QS particles with polyaniline (PANI), creating a hybrid material composite (QS@PANI). The prepared composite's ability to effectively remove Orange G dye (OG) from aqueous solutions was investigated through a series of batch adsorption experiments. The highest removal efficiency was due to the synergistic effect of the QS and the PANI, which favors electrostatic interaction, π-π interaction, and hydrogen bonding due to the nitrogen atoms in their conjugated chains. Adsorption kinetics were described by the pseudo-second-order, and Elovich models, while equilibrium capacity was described by the Langmuir adsorption model. Interestingly, after six repeated cycles, the composites unveiled a high removal proficiency >82% at different pH (2–8) of the solution and possessed an excellent adsorptive property, providing a cost-effective material for decolorization applications. Density functional theory (DFT) calculations and molecular dynamics simulations were utilized to elucidate the adsorption mechanism. The results showed that Orange G adsorption on QS@PANI occurs via a physisorption process. This research not only provided a structure-function relationship for PANI-QS organic-inorganic composite material assemblies, but it also provided an encouraging framework for the long-term advancement of water purification technology. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, the possibility of using un-treated pine (Pinus radiata) sawdust as biosorbent for the removal of three wood dyes (blue, red and black) from aqueous solutions was investigated. The BET surface area of the material was 1.55 ± 0.81 m2 g−1 using N2 at − 196 °C and 17.83 ± 0.032 m2 g−1 using CO2 at 0 °C. The point of zero charge was 4.8. In addition, the material was characterized before and after adsorption by surface analytical techniques. Assays were performed to analize the stability of wood dyes with time and pH and also to estimate the pKa values. Batch adsorption experiments were performed and the influence of experimental parameters such as contact time (up to equilibrium), stirring rate (100 and 210 rpm), adsorbent dose (2–10 g L−1), pH (2–9) and initial dye concentration (5 and 300 mg L−1) were studied. The optimum conditions were pH 2 and adsorbent dose of 6 g L−1 and the highest adsorption percentages achieved at 5 mg L−1 were: 100.0% for the blue, 99.7% for the black and 92.4% for the red. For 300 mg L−1 adsorption efficiency decreased to 85.6, 57.0 and 63.8% for the blue, black and red ones, respectively. Kinetic data were best fitted to the pseudo-second order model, suggesting a chemisorption process. Freundlich and Dubidin-Radushkevich were the best isotherm models. Regeneration study showed that un-treated pine sawdust could be reused efficiently for red dye removal at least in up to four repeated adsorption–desorption cycles using NaOH as desorption agent. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNC) were obtained by series of chemical treatments on dried and grounded sugarcane bagasse. Particle size analysis and X-ray diffraction (XRD) studies were done which confirmed the crystalline behavior of prepared nanocellulose. Nanocomposite adsorbent was prepared by using CNC as filler, chitosan as a binder, and N, N-methylenebisacrylamide (MBA) as cross-linker in different ratios. Field emission scanning electron microscope (FESEM) showed the porous structure of the composite. Fourier transform infrared spectroscopy (FTIR) confirmed crosslinking between CNC and chitosan, contact angle results showed hydrophilic behavior of nanocomposite, and tensile strength testing confirmed good strength of prepared nanocomposite. Malachite green (MG) dye adsorption capacity of nanocomposite adsorbent for different initial dye concentrations was studied and results depicted a maximum removal rate in the first 30 min which reached equilibrium in 90 m. The highest removal rate was observed with 5.0% CNCs content in the nanocomposite. The experimental data showed the best-fitted correlation with Freundlich isotherm (R2 = 0.99) and follow a pseudo 2nd order reaction (R2 = 0.93) by enabling the chemisorption adsorption phenomenon. The regeneration capacity of the nanocomposite was also analyzed, and it was observed that about 90% of the dye was removed from the pre-adsorbed nanocomposite material. [ABSTRACT FROM AUTHOR]

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To effectively remove methylene blue (MB) from dye wastewater, a novel activated carbon (BAC) was manufactured through co-pyrolysis of bamboo shoot shell and K2FeO4. The activation process was optimized to a temperature of 750 °C and an activation time of 90 min based on its excellent adsorption capacity of 560.94 mg/g with a yield of 10.03%. The physicochemical and adsorption properties of BACs were investigated. The BAC had an ultrahigh specific surface area of 2327.7 cm2/g and abundant active functional groups. The adsorption mechanisms included chemisorption and physisorption. The Freundlich model could be used to describe the isothermal adsorption of MB. The kinetics confirmed that the adsorption of MB belonged to the pseudo-second-order model. Intra-particle diffusion was the main rate-limiting step. The thermodynamic study showed that the adsorption process was endothermic and temperature was beneficial for the improvement of adsorption property. Furthermore, the removal rate of MB was 63.5% after three cycles. The BAC will have great potential for commercial development for purifying dye wastewater. [ABSTRACT FROM AUTHOR]

A porous CeO2 was synthesized following the addition of guanidine carbonate to a Ce3+ aqueous solution, the subsequent addition of hydrogen peroxide and a final hydrothermal treatment. The optimal experimental parameters for the synthesis of porous CeO2, including the amounts of guanidine carbonate and hydrogen peroxide and the hydrothermal conditions, were determined by taking the adsorption efficiency of acid orange 7 (AO7) dye as the evaluation. A template−free hydrothermal strategy could avoid the use of soft or hard templates and the subsequent tedious procedures of eliminating templates, which aligned with the goals of energy conservation and emission reduction. Moreover, both the guanidine carbonate and hydrogen peroxide used in this work were accessible and eco−friendly raw materials. The porous CeO2 possessed rapid adsorption capacities for AO7 dye. When the initial concentration of AO7 was less than 130 mg/L, removal efficiencies greater than 90.0% were obtained, achieving a maximum value of 97.5% at [AO7] = 100 mg/L and [CeO2] = 2.0 g/L in the first 10 min of contact. Moreover, the adsorption–desorption equilibrium between the porous CeO2 adsorbent and the AO7 molecule was basically established within the first 30 min. The saturated adsorption amount of AO7 dye was 90.3 mg/g based on a Langmuir linear fitting of the experimental data. Moreover, the porous CeO2 could be recycled using a NaOH aqueous solution, and the adsorption efficiency of AO7 dye still remained above 92.5% after five cycles. This study provided an alternative porous adsorbent for the purification of dye wastewater, and a template−free hydrothermal strategy was developed to enable the design of CeO2−based catalysts or catalyst carriers. [ABSTRACT FROM AUTHOR]

This study evaluated the adsorption and enzymatic degradation of azo dyes when using SMS. The laccase present in the SMS was characterised, and the maximum activity was obtained at pH 2, a temperature of 45°C, a Michaelis–Menten constant (Km) of 0.264 mM, and a maximum reaction rate (Vmax) of 117.95 µmol L−1 min−1. The presence of NaCl at 5 mM inhibited enzyme activity while no inhibition was observed by Na2SO4, typically found in textile wastewater. The maximum dye adsorption (57.22%) was achieved at pH 8.0, 25°C, and 100 g L−1 of SMS while the maximum enzymatic degradation (14.18%) was obtained under the same conditions, except at pH 4.0. The enzymes laccase, lignin peroxidase, and manganese peroxidase trapped in the SMS resulted in higher dye discolouration when compared to that extracted with aqueous solution, meaning that SMS has strong adsorption capacity and is a natural immobilisation matrix, which improves the enzymatic degradation of the dyes. Thus, SMS can be used in the treatment of textile effluents for dye removal by simultaneous mechanisms of adsorption and enzymatic degradation, with reduction of environmental impacts for SMS disposal and reduction of the costs associated with commercial enzymes and adsorbents. [ABSTRACT FROM AUTHOR]