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Several low-cost adsorbents, including orange mesocarp (OMS), Bengal gram husk (BGH), and Khangar, were investigated for their capability to absorb chromium hexavalent ions from synthetic solutions. Process parameters like pH, dose of the adsorbent, concentration of metal ions, and the time they remain in contact were used to calculate the equilibrium adsorption levels. The most crucial factor for removing Cr(VI) ions was observed to be pH. The highest removal for Cr(VI) was determined to be 87%, 90%, and 92%, for OMS, BGH, and Khangar adsorbents respectively. Langmuir adsorption isotherm was observed to be the best fitted, with regression values (R2) of 0.988, 0.974, and 0.989 for OMS, BGH, and Khangar, separately. The kinetic study of Cr(VI) was best expressed with pseudo-second-order. Adsorption process was found to be endothermic and spontaneous in nature with enthalpy (ΔH0) of 48.74, 52.54, and 53.68 KJ mol−1 and entropy of 48.95, 52.78, and 53.93 KJ K−1mol−1 for OMS, BGH, and Khangar respectively. Also, the possible use of OMS, BGH, and Khangar for Cr(VI) ion removal is indicated by the possibility of reusing adsorbents successfully up to three times. According to the study out of the three adsorbents, Khangar was observed to be the most efficient adsorbent for extracting Cr(VI) ions from an aqueous medium. [ABSTRACT FROM AUTHOR]

In this research, composite materials were prepared by combining polypyrrole (PPY) and polyaniline (PAN) with Oryza sativa (OS). These biocomposites were utilized for the adsorption of Nitenpyram (insecticide), from aqueous solutions. The study involved the optimization of various process variables including contact time, pH, adsorbent dose and initial Nitenpyram concentration. The maximum sorption efficiency of OS for Nitenpyram was observed at pH 2, biosorbent dose of 0.05 g, an initial Nitenpyram concentration of 125 mg/L and contact time of 30 min. To analyze the Nitenpyram adsorption process, the adsorption data for OS and its composites (OS-PPY and OS-PAN) were subjected to equilibrium isotherms and kinetics models (pseudo-first and pseudo-second-orders). The Langmuir isotherm and pseudo-second-order explained the Nitenpyram adsorption data. Furthermore, the feasibility of the adsorption was evaluated by employing thermodynamic studies. The outcomes of the study demonstrated the promising efficiency of the synthesized biocomposites for Nitenpyram removal, which was 37.03, 43.0 and 35.71 (mg/g) in the case of OS, OS-PPY and OS-PAN composites. These findings suggest that the composites have promising potential for the removal of pesticides from wastewater, contributing to the development of effective strategies for environmental remediation. [ABSTRACT FROM AUTHOR]

AbstractBentonite-gelatin (BT-Ge) and bentonite-sucrose (BT-Su) composites were fabricated using a simple solution mixing method and employed as adsorbents for extracting dyes from aqueous solutions. The structural characteristics of the fabricated composite materials were elucidated using x-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The adjustable adsorption capabilities of the developed adsorbents toward methyl red (MR) and methylene blue (MB), representing anionic and cationic dyes, respectively, were examined by varying the mass ratio of bentonite to gelatin and sucrose. The impact of contact time, adsorbent dosage, and pH on the adsorption process of MR and MB onto BT-Ge and BT-Su was investigated. Kinetic data fitting indicated a good agreement with the pseudo-second-order model, with equilibrium typically achieved within 30 min, resulting in 99.69 ± 0.550, 99.56 ± 0.344, 99.90 ± 0.488% removal of MB with BT, BT-Su, and BT-Ge, respectively and 99.50 ± 0.854, 99.50 ± 0.658, and 99.57%±0.501% of MR with BT, BT-Su, and BT-Ge, respectively from the aqueous solutions. Equilibrium data were analyzed using Langmuir and Freundlich isotherm models, with the Langmuir model showing the best fit and indicating a maximum adsorption capacity of 666.66 mg g−1 of MR and 285.71 mg g−1 of MB at 25 °C. These findings underscore the remarkable efficacy of BT-Ge and BT-Su composites in eliminating dyes from wastewater, particularly colored effluents. [ABSTRACT FROM AUTHOR]

Currently, adsorption stands as a viable technique for the effective removal of pollutants such as heavy metals from water. Within this research endeavor, adapted green algae (Coelastrella sp.) have been harnessed as a sustainable and environmentally conscious adsorbent, employed in the removal of Hg(II) ions from a simulated aqueous solution via employment of an Airlift bioreactor. The analysis of the attributes of adsorbent was conducted through the utilization of Fourier transform infrared (FTIR) spectroscopy. The examination of residual concentrations of Hg(II) ions in the treated solution was accomplished through the utilization of atomic absorption spectroscopy (AAS). The impact of various experimental factors, including the duration of contact (ranging from 10 to 90 minutes), initial concentrations of Hg(II) ions (ranging from 500 to 2000 μg/l), quantity of adsorbent introduced (ranging from 0.1 to 0.7 g per 250 ml), temperature variations (ranging from 20 to 40 °C), and airflow velocity (ranging from 200 to 300 ml/min), was systematically examined. For the optimization of adsorption efficiency, MINITAB 18 software was employed. The equilibrium data was subjected to analysis using the Langmuir, Freundlich, and Temkin isotherm models. Employing the framework recommended by MINITAB 18, the optimal parameters for adsorption were identified as 2000 μg/l for initial concentration, 90 minutes for contact time, 40 °C for temperature, and 300 ml/min for airflow rate. The Langmuir equation yielded the highest adsorption capacity, measuring 750 μg/g at a temperature of 40 °C.

[Gd(HP‐DO3A)] (gadoteridol) as an active compound of ProHance® is a widely employed contrast agent in clinical MRI scans in the last 30 years. Recent concerns about the long‐term retention of gadolinium‐based contrast agents (GBCAs) led to a deeper investigation of the structural features underlying the integrity of the paramagnetic metal complex. Several human and nonclinical studies have noted marked differences among the macrocyclic GBCAs, with the least retention of Gd traces and most rapid elimination consistently being reported for [Gd(HP‐DO3A)]. It was deemed of interest to assess how minor structural/electronic changes associated to the ligand structure may affect basic properties of the metal complex with several [Gd(HP‐DO3A)] analogues synthesized and characterized in the last years. We recently reported that the closest homolog of [Gd(HP‐DO3A)], i. e.: [Gd(HB‐DO3A)], in which a (±)‐2‐hydroxy‐1‐propyl pendant arm is replaced by a (±)‐2‐hydroxy‐1‐butyl moiety, showed a significantly different retention behaviour in the model interaction with collagen, despite the apparently very minor structural difference. In this paper we report a comprehensive study of the structural, thermodynamic, kinetic and relaxation properties of [Gd(HB‐DO3A)], compared to the parent [Gd(HP‐DO3A)] and to other closely related macrocyclic GBCAs to assess whether very minor structural changes can modulate the physico‐chemical properties of Gd3+ complexes. [ABSTRACT FROM AUTHOR]

[Gd(HP‐DO3A)] (gadoteridol) as an active compound of ProHance® is a widely employed contrast agent in clinical MRI scans in the last 30 years. Recent concerns about the long‐term retention of gadolinium‐based contrast agents (GBCAs) led to a deeper investigation of the structural features underlying the integrity of the paramagnetic metal complex. Several human and nonclinical studies have noted marked differences among the macrocyclic GBCAs, with the least retention of Gd traces and most rapid elimination consistently being reported for [Gd(HP‐DO3A)]. It was deemed of interest to assess how minor structural/electronic changes associated to the ligand structure may affect basic properties of the metal complex with several [Gd(HP‐DO3A)] analogues synthesized and characterized in the last years. We recently reported that the closest homolog of [Gd(HP‐DO3A)], i. e.: [Gd(HB‐DO3A)], in which a (±)‐2‐hydroxy‐1‐propyl pendant arm is replaced by a (±)‐2‐hydroxy‐1‐butyl moiety, showed a significantly different retention behaviour in the model interaction with collagen, despite the apparently very minor structural difference. In this paper we report a comprehensive study of the structural, thermodynamic, kinetic and relaxation properties of [Gd(HB‐DO3A)], compared to the parent [Gd(HP‐DO3A)] and to other closely related macrocyclic GBCAs to assess whether very minor structural changes can modulate the physico‐chemical properties of Gd3+ complexes. [ABSTRACT FROM AUTHOR]

AbstractThe rise in cyanide concentration in groundwater in many developing countries is linked to the indiscriminate discharge of cyanide-bearing wastewater from cassava processing industries. This research synthesized a super-active activated carbon (AC) from a novel biomass precursor, Raphia hookeri kernel, functionalized with phosphoric acid via in-situ and ex-situ methods. Morphological and functional characterizations were performed, and the influence of some key process variables on cyanide adsorption was also investigated for the two derived ACs to study the impact of the activation method used. The optimal conditions for cyanide adsorption for the in-situ and ex-situ–derived ACs were identified as pH 8, AC dose of 0.15 g, temperature of 40 °C, and initial cyanide concentration of 100 mgL−1 at different equilibrium times of 100 min and 120 min, respectively. The kinetic studies revealed that the pseudo-second-order kinetic model fitted the adsorption data better for the two ACs based on the high correlation coefficients (r2), suggesting that the adsorption process is chemisorption. The equilibrium studies showed that the in-situ-derived AC followed the Langmuir isotherm with a maximum adsorption capacity (qm) of 93.821 mgg−1 indicating monolayer adsorption for the in-situ-derived AC. The ex-situ-derived AC, however, followed the Sips isotherm with a maximum adsorption capacity (qm) of 79.381 mgg−1 indicating a heterogeneous surface for the ex-situ-derived AC. The ACs showed decreasing cyanide adsorption after five cycles but maintained significant adsorption capacity after desorption-adsorption cycles. [ABSTRACT FROM AUTHOR]

Pharmaceutical contamination poses a significant threat to global health. Due to their high solubility in water, antibiotics are difficult to remove. This study produced and used sulfonated graphene oxide (SGO) to adsorb sparfloxacin from aquatic environments. UV–Visible, Fourier transform infrared (FTIR), X-ray diffraction (XRD), XPS, SEM, TEM, EDX, particle size, Thermogravimetric analysis (TGA), and acid-base titration were used to characterize synthesized SGO particles. The BET technique determined SGO's surface area (32.25 m2/g). The calculated pHPZC of SGO was 2.5. Sparfloxacin adsorption onto SGO was analyzed using adsorption duration, medium pH, adsorbent dosages, antibiotic concentration, cations, and solution temperature. The pseudo-second-order kinetic model better described experimental kinetic data than the pseudo-first-order and Elovich models. Equilibrium isotherm data supported the Langmuir model, revealing a peak absorption capacity of 1428.57 μmol/g at 25 °C. The kinetic and isotherm models' applicability was assessed using error analysis. A thermodynamic analysis revealed an endothermic, spontaneous adsorption process with a change in entropy (ΔS) of 114.15 J/mol K and enthalpy (ΔH) of 8.44 kJ/mol. A regeneration analysis showed that SGO adsorption efficiency topped 86.4 % after five cycles.

The present work focuses on examining the batch removal of Fe (III) from water using powdered Peganum Harmala seeds, characterized as FT-IR. In this work, several parameters are measured, including contact time, pH, Fe (III) concentration, reaction temperature effect, and adsorbent dose effect. Fe (III) adsorption was assessed using a UV-vis spectrophotometer at a wavelength of 620 nm. The findings demonstrated a positive correlation between the dosage of adsorbent and Fe (III) ions removal, with an increase in the adsorbent dose corresponding to higher elimination of Fe (III) ions. Therefore, the Langmuir isotherm model yielded more accurate equilibrium data compared to the Frendulich model. The kinetic data were mostly analyzed using a pseudo-second-order model rather than a pseudo-first-order model. Thermodynamic parameters, including enthalpy (ΔH◦), entropy (ΔS◦), and free energy (ΔG◦), were calculated. The adsorption process was found to be exothermic. Overall, Peganum Harmala was a favorable adsorbent for removing Fe (III) from aqueous solutions.

In this study, we prepared and used manganese oxide-modified vermiculite (Mn–MV) as an adsorbent to sequester Rhodamine B (RhB) dye from aqueous solution. Mn–MV was characterized using a Fourier transform infrared (FT-IR) spectrometer, XRF spectrometry and scanning electron microscope (SEM) to identify the functional groups, components and morphology of the sorbent. Analysis of the adsorbent's functional groups revealed the presence of O–H, C–H, C=C, C–O, and C–O–H groups. The experiments were conducted using a batch adsorption procedure. The optimal removal of Rhodamine B (RhB) was achieved with a dosage of 1.75 g of Mn–MV, a pH of 10, and a duration of 45 min. The study on the effect of temperature demonstrated that an increase in temperature favoured the removal of RhB using Mn–MV. The data from the kinetic and isotherm models were best described by the pseudo-second-order and Langmuir models. The thermodynamic parameters, ∆H = 6.32 kJ/mol and ∆S = 82.12 J/mol/K, indicate that the adsorption process is endothermic and spontaneous. These results indicate that vermiculite clay has the potential to be a cost-effective adsorbent for the removal of RhB dye.

The CO2-capturing performance of a sterically hindered amine, 2-amino-2-hydroxymethyl1,3-propanediol (AHPD), was systematically studied in this work. First, absorption kinetics was investigated using the stirred-cell technique. At T = 308 K, CO2 reacted with AHPD according to a second-order reaction (rate constant = 264 m³ /kmol-s), whose activation energy was 33 kJ/mol. Second, the solubility of CO2 in AHPD at 308 K was measured up to 100 kPa CO2 partial pressure. For instance, it was shown that the loading capacity of AHPD (2.5 M) was 0.56 mol/mol, while the equilibrium CO2 partial pressure was 79 kPa. Third, a closed-loop absorber-desorber setup was used to test solvent performance for capturing CO2 from CO2/air mixture (12:88 v/v). The two columns were continuously operated at 313 (absorber) and 383 K (desorber) at 0.1 MPa pressure. Around 75% CO2 was absorbed using 12 wt. % AHPD (or 0.9 M). The value of QReg (regeneration energy) was 6.28 MJ/kg CO2. It was thus evident that AHPD is a credible hindered amine-based solvent. A comparison of its equilibrium, kinetic and regeneration features with 2-amino-2-methyl-1-propanol (AMP) was provided. Finally, three rate promoters–hexamethylene diamine (HMDA), monoethanolamine (MEA) and AMP–were added to AHPD. The performance of HMDA was most promising. In a batch desorption setup, it was shown that alumina catalyst improved desorption of CO2 from loaded AHPD/HMDA mixtures. This work will stimulate further interest in the use of AHPD solutions for CO2 removal. [ABSTRACT FROM AUTHOR]

Aqueous solutions containing alkaline salts of natural amino acids, such as those from protein in plant seeds or high protein animal‐based waste, are green CO2‐separation solvents. In the present work, potassium salts of nine such amino acids were chosen for an in‐depth study: alanine, arginine, aspartic acid, glutamic acid, glycine, leucine, proline, serine, and valine. The kinetics of CO2 absorption in aqueous solutions of these salts was studied using a stirred cell. From the measurements of the absorption rate at different salt concentrations (molarity 0.1 and higher), CO2 partial pressures (5–25 kPa), and temperatures (298–308 K), values of the reaction order, rate constant, and activation energy were determined. Additionally, the liquid‐side mass transfer coefficient (0.005 cm/s) was also found. Potassium salts of proline, glycine, and arginine were most reactive and, hence, were chosen for equilibrium study. The loading capacity of these salts was measured at 308 K in a vapour–liquid equilibrium setup at near‐ambient pressure. On the contrary, the other chosen acids were comparatively less reactive with CO2. [ABSTRACT FROM AUTHOR]

Acetaminophen (C8H9NO2, also called paracetamol) is an active metabolite of phenacetin with antipyretic and analgesic effects and has been extensively used as a painkiller. Currently, the problem of pharmaceuticals in water and sewage is common, especially in highly urbanized countries. Laboratory-scale experiments were carried out using an adsorbent—granulated activated carbon (WD-extra)—to remove acetaminophen (ACT) from water. The initial concentration of acetaminophen was 20 mg ACT/dm3. The adsorption kinetics, influence of the pH on adsorption and dose of the used adsorbent were determined under batch conditions. The adsorption of ACT on activated carbon was more efficient when the water solution was acidic (at pH 2, it was the most effective). The highest percentage of removal (99%) was obtained for the WD-extra dose of 10.0 g/dm3. The time taken to establish the dynamic equilibrium of the system was 60 min. The effectiveness of adsorption was determined based on the Freundlich and Langmuir adsorption isotherms. It was found that WD-extra activated carbon effectively removed ACT from water solutions. [ABSTRACT FROM AUTHOR]

In this work, the adsorption of amoxicillin on unmodified, propylamine-modified, and citric acid-modified cassava peels was studied at laboratory scale. Adsorption tests were carried out at amoxicillin initial concentrations of 100 and 300 mg/l at pH values of 5, 6, 7, and 8, for each of the obtained adsorbents. The adsorption capacity results showed that the best pH of operation is 8 with a time of equilibria of 420 min. The kinetic data were fitted to the pseudo-first and pseudo-second order models obtaining better results with the last one and values for K2 of 2,13 g/mmol·min for unmodified cassava peels, 1,74 g/mmol·min for citric acid-modified cassava peels and 1,52 g/mmol·min for propylamine-modified cassava peels, respectively. The maximum removal percentage and maximum adsorption capacity were 34,4% and 0,016 mmol/g, for unmodified cassava peels; 50,39% and 0,024 mmol/g, for citric acid-modified cassava peels; and 50,93% and 0,024 mmol/g, for propylamine-modified cassava peels, respectively. [ABSTRACT FROM AUTHOR]

Pesticides are pollutants found in wastewater as a result of agricultural activities. The adsorption process is a cost-effective technique among the other treatment processes because of its simplicity in design, easy operation, and high adsorption capacity for the removal of pesticides from wastewater. Activated carbon (AC) is a widely used adsorbent but due to its high production cost, its use is limited. This limitation has necessitated a growing interest in alternative sources in the production of low-cost activated carbon from agricultural wastes and other waste materials. In the present study, activated carbon produced from tobacco stems via chemical activation using phosphoric acid was tested for the removal of cypermethrin from aqueous solution. Prior to its use, the prepared activated carbon was characterized by FTIR and SEM. Tobacco stem-activated carbon with an impregnation ratio of 1:3 produced at a temperature of 600 °C was used in bench studies on the removal of cypermethrin from aqueous solutions because of its high iodine number of 776.25 mg/g and fixed carbon content of 85.33%. Batch experiments were performed to determine the optimum adsorption conditions, and suitable kinetic for the adsorption of cypermethrin onto tobacco stems activated carbon (TAC). The influence of adsorbent dosage, contact time, and initial cypermethrin concentration were studied. High-Performance Liquid Chromatography (HPLC) was used for the determination of cypermethrin concentration and a recovery percentage of up to 99.0% was obtained from a spiked concentration of 200 ppm. Equilibrium data were obtained by testing the adsorption data using the Langmuir and Freundlich models. The results obtained from the isotherm and kinetic study are best described using the Freundlich isotherms and pseudo-second-order kinetic adsorption models with the highest regression coefficients' of R2 = 0.9998 and 0.9937, respectively. Results showed that the maximum amount of cypermethrin adsorbed was 2.162 mg/g and this was achieved at 270 min of the contact time. A comparison of the prepared TAC and a commercial activated carbon (1105 m2/g, pore diameter of 1.67 nm, and micropore volume of 0.4004 cm3/g) demonstrated to have a remarkable potential for removing cypermethrin pesticide from aqueous solution. This facile route highlights the possibility of utilizing tobacco stems to produce low-cost, green, and effective activated carbon for the removal of cypermethrin from water, thus, converting the waste to a value-added product as well as providing some solutions to the many challenges faced with tobacco stem wastes disposal. The work not only offers an economic source for the production of activated carbon but also demonstrates that TAC is a promising adsorbent for the removal of cypermethrin and other organic pollutants from wastewater. [ABSTRACT FROM AUTHOR]

TiO2 nanoparticles were synthesized using Phyllanthus acidus leaf extract. The presence of amines, aliphatic alcohol, phenolic acids and hydroxyl group in the Phyllanthus acidus leaf extract may be responsible for the reduction of TiO2 nanoparticles from a precursor. Green synthesized TiO2 nanoparticles were characterized with the help of UV–visible spectroscopy, XRD, FTIR, FESEM-EDX, TEM and BET analysis. The size of nanoparticles was determined to be 20–40 nm with a surface area of 108.31 m2/g, a pore size of 1.347 nm and a total pore volume of 0.1456 cc/g. The performance of heavy metal adsorption of TiO2 nanoparticles was assessed. The process variables such as metal initial concentration, adsorbent dosage, pH and contact time for the adsorption of lead were optimized using response surface methodology (RSM) with central composite design (CCD). The lead removal efficiency of 98.6% was achieved using green synthesized TiO2 nanoparticles under optimum conditions, an initial lead concentration of 89 mg/L, a dosage of adsorbent at 0.32 g, pH of 7.8 and a contact time of 89 min. The fitting of different isotherm models was carried out with the experimental and observed data, which confirmed that the Langmuir model best fit to describe the adsorption isotherm with an adsorption capacity of 2.633 mg/g. The first-order model is the optimum kinetic model, illustrating the rate of the equation of the adsorption of lead on TiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

The present work focuses on examining the batch removal of Fe (III) from water using powdered Peganum Harmala seeds, characterized as FT-IR. In this work, several parameters are measured, including contact time, pH, Fe (III) concentration, reaction temperature effect, and adsorbent dose effect. Fe (III) adsorption was assessed using a UV-vis spectrophotometer at a wavelength of 620 nm. The findings demonstrated a positive correlation between the dosage of adsorbent and Fe (III) ions removal, with an increase in the adsorbent dose corresponding to higher elimination of Fe (III) ions. Therefore, the Langmuir isotherm model yielded more accurate equilibrium data compared to the Frendulich model. The kinetic data were mostly analyzed using a pseudo-second-order model rather than a pseudo-first-order model. Thermodynamic parameters, including enthalpy (ΔH◦), entropy (ΔS◦), and free energy (ΔG◦), were calculated. The adsorption process was found to be exothermic. Overall, Peganum Harmala was a favorable adsorbent for removing Fe (III) from aqueous solutions. [ABSTRACT FROM AUTHOR]

Abundantly generated Sawdust by local sawmills was used to prepare activated carbon (AC) by impregnation using 3 M orthophosphoric acid and calcination at 400 °C. The obtained AC was tested for the removal of Basic Brown1 dye, from aqueous solutions. The batch adsorption experiment studies were carried out to evaluate various adsorbing effect of experimental parameters such as pH, adsorbent dosage, equilibrium time and initial dye concentration. The results showed that the maximum removal of Basic Brown1 dye was achieved at pH = 5. Kinetic studies revealed that the pseudo-second-order model showed the best fitting to the experimental data. The equilibrium data were well described by Freundlich model. Thermodynamic parameters indicated that the adsorption process was endothermic and spontaneous. The results confirmed the important retention capacity of modified Sawdust to remove Basic Brown1 dye, a pollutant frequently present in the local textile industry wastewaters and causing major environmental pollution problems. [ABSTRACT FROM AUTHOR]

This study investigates the potential of Prosopis cineraria leaf powder (PCLP) as a biosorbent for removing heavy metal ions (HMIs) from aqueous solutions. The biosorption characteristics of PCLP were evaluated with respect to pH, contact time, initial concentrations, and biosorbent dosage. Equilibrium data were analyzed using Langmuir, Freundlich, Temkin, and Dubinin‐Radushkevich (D‐R) isotherm models. Langmuir isotherm demonstrated monolayer adsorption for Cr(VI) (R2 = 0.9876) and Pb(II) (R2 = 0.9990), with maximum adsorption capacities of 10.046 and 10.238 mg g−1, respectively. Kinetic analysis showed a good fit to the pseudo‐second‐order (PSO) model, with R2 values of 0.9979 for Cr(VI) and 0.9821 for Pb(II), indicating that H‐bonding and electrostatic interactions were the dominant adsorption mechanisms. Additionally, non‐linear regression analysis was performed to determine the best‐fitting equilibrium model and compared with linear isotherm and kinetic models. The results confirmed that the nonlinear method outperformed the linear method in isotherm analysis. Specifically, the nonlinear Temkin isotherm model exhibited stronger correlation with the experimental data, making it the most suitable model for fitting the equilibrium data. Conversely, the non‐linear pseudo‐second‐order models yielded comparable goodness of fit to the linear kinetic analysis results. Overall, the findings highlight PCLP as a promising, environmentally friendly, and cost‐effective biosorbent for the removal of toxic HMIs, contributing to sustainable environmental management. [ABSTRACT FROM AUTHOR]

In order to enhance the efficiency of heavy metal ion extraction from aqueous medium, new nanocomposite magnetic sorbents were synthesized on the base of natural zeolite (Zt) and nanoparticles of ZnFe2O4 (F). The composition, structure and physical–chemical properties of new composites with 2% (Zt-2F), 8% (Zt-8F) and 16% (Zt-16F) of zinc ferrite were characterized by XRD, BET adsorption–desorption of nitrogen, SEM with elemental mapping, TEM and magnetometry. The sorption capacity of materials was assessed towards Cu2+ ions in aqueous solutions, for which kinetic and equilibrium features of sorption were established. The maximal sorption capacity (amax, mg/g) of the studied materials increased in the order: Zt (19.4) < Zt-2F (27.3) < Zt-8F (30.2) < Zt-16F (32.8) < ZnFe2O4 (161.3). The kinetics of the sorption process followed a pseudo-second order kinetic model. The sorption equilibrium at zinc ferrite was successfully described by the Langmuir model, while the Freundlich model better fitted the sorption equilibrium on zeolite and composites. The efficiency of Cu2+ ion extraction from 320 mg/dm3 aqueous solution was 63% for composite Zt-16F and 100% for a sample of ZnFe2O4. It was established that the proposed composite sorbents provide the operation of several cycles without regeneration, they can be easily recycled with 0.1 N HCl solution and are capable of magnetic separation. The advantages of new composites and the proposed method of synthesis allow recommending these materials as effective sorbents of heavy metals from wastewater. [ABSTRACT FROM AUTHOR]

This study is concerned with the examination of the sorptive ability of a new carbonaceous (CPC) sorbent prepared under optimized conditions with H3PO4 activation from the citrus industrial processing pulp (CP) in removing Reactive Blue 19 dye (RB19) from an aqueous solution. Optimum removal conditions were determined based on the maximum effects of some variable process parameters. The kinetic data showed agreement with the pseudo-second-order model. The isotherm data fit the Langmuir isotherm model best, and the maximum amount of sorbed RB19 was determined as 437.89 mg/g. The calculated thermodynamic parameters showed that the process is spontaneous and endothermic in nature. Desorption studies were performed with various desorbents for the recovery of RB19 and/or recyclability of CPC. The results show that CPC is a highly effective and reusable sorbent for cleaning water containing RB19. [ABSTRACT FROM AUTHOR]

In the present study, the possibility of using a strong-base fibrous material FIBAN A-1 (Institute of Physical Organic Chemistry, National Academy of Sciences of Belarus, Belarus) as a sorbent to remove tryptophan from aqueous solutions is investigated. The capacity characteristics of the anion exchangers in the form of granules and fibers containing quaternary ammonium bases as functional groups with respect to the chosen amino acid are analyzed. The influence of the pH of the medium on the sorption of amino indolylpropanoic acid onto the A-1 fiber is determined. IR spectroscopy confirms the fact of the fixation of amino acids from solutions with pH ~5.0–5.5 due to the charge exchange of the zwitterion by the OH groups of the sorbent. The specific features of both the equilibrium and kinetics of tryptophan sorption from solutions with a pH close to the isoelectric point are studied. Based on the analysis of the isotherms of sorption of the amino acid at different temperatures, a monomolecular mechanism of the sorptive sorption process and its endothermic character are established. The kinetic characteristics of tryptophan sorption indicate a significant contribution of external diffusion to the velocity of the investigated process. [ABSTRACT FROM AUTHOR]

In this study, orange peel (OP) biochar was used as a bio-sorbent for the removal of copper and lead from wastewater in single and binary systems. The equilibrium and kinetic studies were conducted at a pH value of 5, which was the maximum adsorption pH value for both metal ions. The equilibrium studies were investigated at a varying initial concentration (10–200 mg/L) with a constant dosage of 0.1 g, while the kinetic studies were conducted at a fixed initial concentration of 200 mg/L with a constant dosage of 1 g/L for both single and binary systems. The maximum adsorption capacity of the orange peel biochar was 28.06 mg/g, 26.83 mg/g, 30.12 mg/g and 27.71 mg/g for single Cu2+, binary Cu2+, single Pb2+ and binary Pb2+ systems, respectively. The Langmuir isotherm model fitted the experimental data, suggesting that adsorption occurred on a monolayer, while the pseudo-second-order model performed well with the kinetic data. The point of zero charge (pHpzc) of the orange peel biochar was found to be 10.03, which revealed that the surface of the bio-sorbent contains basic groups. A Fourier infrared transform (FTIR) spectroscope and scanning electron microscope, coupled with energy dispersive x-ray (SEM-EDX) and x-ray diffraction analyses, were used to determine the functional groups, surface morphology, and inorganic elements present on the surface of the bio-sorbent, respectively. The results obtained have shown that orange peel biochar is efficient for the removal of Cu2+ and Pb2+ ions from an aqueous solution. [ABSTRACT FROM AUTHOR]

The present study investigates the feasibility of adsorption method for the removal of Di-n-butyl phosphate from sodium carbonate solution on adsorbents such as XAD-4 and XAD-7. The fundamental aspects of equilibrium and kinetics of adsorption have been studied. The experimental equilibrium data were fitted well with Sips isotherm, and maximum solid uptake capacity for monolayer coverage (qm) was found to be 0.363 × 10−3 mol/g and 0.385 × 10−3 mol/g for XAD-4 and XAD-7, respectively. The adsorption kinetics was well described by the pseudo-first-order model, and estimated first-order rate constant values were found to be 0.041 min−1 for XAD-4 and 0.027 min−1 for XAD-7. The transport mechanism of solute from the bulk solution to adsorbent was described in detail with suitable mathematical model, and experimental kinetic data were superimposed on numerically solved concentration profiles to calculate external mass transfer coefficient (kf) and effective diffusivity (De). The values of kf and De were estimated as 4.632 × 10−7 m/s and 8.849 × 10−13 m2/s, respectively, for XAD-4, whereas for XAD-7, the values were found to be 2.132 × 10−6 m/s and 1.389 × 10−12 m2/s. XAD-7 is found to have slightly better adsorption capacity and transport characteristics than XAD-4. [ABSTRACT FROM AUTHOR]

This is the first study to show the use of fibers from the Washingtonia filifera palm tree as an adsorbent for the removal of Crystal Violet (CV) dyestuffs from aqueous solutions by adsorption. The research on new materials to prevent the contamination of pollutants is of great importance. CV is a dye that is known to have toxic and carcinogenic effects and is used in many industries. In this study, the effects of parameters such as initial adsorbate concentration, adsorbent dose, and pH on the adsorption efficiency were investigated. The highest removal efficiency was 95.55% and the maximum adsorption capacity was found to be 85.91 mg/g. The maximum adsorption capacity of the fibers used reached a pH of 8. The BET surface area of the adsorbent was 4.1484 m2/g and the average pore width 6.8563 nm. The average pore volume was 0.00413 cm3/g for mesopores and 0.00017 cm3/g for micropores. Stegmata structures, also called silica bodies, were observed in SEM images. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) isotherms were studied. The Temkin isotherm (R2 = 0.9692) best explained the results in the stirring experiments. The Freundlich isotherm (R2 = 0.9643) best explained the stationary phase systems without stirring. It was determined that the equation that best explained the dye removal kinetics was the pseudo-second-order kinetic model. [ABSTRACT FROM AUTHOR]

CO2 separation with harmful chemicals will damage the environment. It is essential to explore greener solvents that are producible from renewable resources such as biomass. The suitability of N‐methyl‐D‐glucamine (MG), also known as meglumine, for capturing CO2, was explored in this work. This nontoxic amino sugar, which is derived from sorbitol, represents a renewable bio‐solvent. It was found that MG is especially reactive with CO2. Trials were performed in a stirred cell reactor with a flat gas–liquid interface between 303 and 313 K. The values of the pseudo‐first‐order reaction rate constant, reaction orders, and activation energy were found. The loading capacity (α) of 0.5 M MG solution was measured at T = 308 K. For a typical value of α = 0.524 mol CO2/mol MG, the corresponding equilibrium partial pressure of CO2 was 22 kPa. Finally, it was found that the catalyst Al2O3 aided in the desorption of CO2‐loaded MG solutions. Desorption efficiency using Al2O3 was higher (74%) than that achieved without this catalyst (45%). It is thus clear that MG represents a potential solvent for improved CO2 separation from gases. [ABSTRACT FROM AUTHOR]

In this study, we developed a unique adsorbent known as extractant-impregnated resin (EIR) by surface impregnation of XAD-11600 amberlite resin with the Vesavin ligand. This resin demonstrated exceptional selectivity for the absorption of lead (Pb2+) ions from aqueous solutions. The ability of EIR to remove lead from polluted water was studied as a function of experimental parameters, including the kinetics, equilibrium, and thermodynamics of the adsorption process. The experimental results provided the basis for the fitting of equilibrium adsorption isotherms with the Langmuir model, and the maximum adsorption capacity of EIR for Pb(II) ions was determined to be approximately 1662 mg/g. Kinetic and thermodynamic studies were also conducted to gain insight into the behavior of the adsorption process. It was found that the rate of penetration of lead ions into the particle was the primary factor controlling the absorption process of lead on the surface of the porous adsorbent. Additionally, the studies demonstrated that the EIR can be utilized for multiple absorption and desorption cycles.

The batch removal of Pb2+, Cd2+, and Zn2+ ions from aqueous solution using brut keratin powder prepared from Algerian sheep horns (BKASH) were investigated. The BKASH before and after biosorbent was characterized using Fourier-transform infrared spectroscopy and scanning electron microscopy. The study investigated the effects of pH, contact time, biosorbent dose, initial ion concentration, and temperature on the removal of these heavy metal ions. The results indicated that the optimal conditions for adsorption were an initial concentration of 20 mg/L for 30 min. The monolayer adsorption capacities of Pb2+, Cd2+, and Zn2+ were found to be 33.33, 23.81, and 25 mg/g, respectively, at 298 K. The maximum efficiency of Pb2+, Cd2+, and Zn2+ adsorption was obtained at pH values of 4.5, 6, and 4.5, respectively, which is higher than the adsorbent's pHZPC of 4.3. The experimental data was fit with Langmuir, Freundlich, Temkin and Elovich isotherm models, and the best coefficient of determination was deduced by Langmuir isotherm. Three models were used to evaluate the kinetics of the process, including pseudo-first-order, pseudo-second-order kinetic models and intraparticle diffusion. The pseudo-second-order model was found to have the best correlation for the adsorption of Pb2+, Cd2+, and Zn2+ on BKASH. Thermodynamic parameters were calculated and discussed. The negative Î"G° and positive Î"H° values indicated that the overall adsorption was spontaneous and endothermic. Overall, the study demonstrated that BKASH biosorbent has satisfactory biosorption capacity and can be considered an effective biosorbent for water treatment with a low concentration of heavy metal ions. [ABSTRACT FROM AUTHOR]

This study explores the possibility of using Luffa Cylindrica Cords to remove Copper from aqueous effluents. The removal of copper was investigated in both batch and continuous processes. Batch mode adsorption studies were performed by varying parameters such as contact time, pH, initial copper concentration and temperature. The different adsorption models Langmuir, Freundlich, Elivoch and Temkin were used for the mathematical description of the adsorption equilibrium, and it was found that the very well - equipped experimental data for the Langmuir model (R2=0.961), the pseudo - first - order and pseudo - second - order kinetic models were applied to the experimental data. The experimental data fitted very well the pseudo-second-order kinetic model (R2= 0.965) and also followed the model of intra particle diffusion for concentrations between 5 and 50 mg/L), whereas diffusion is not the only rate - control step. Finally the thermodynamic parameters for the adsorption of copper onto cords were also determined. The negative sign of S° shows the decreased randomness at the solid - solution interface during adsorption, and the negative sign of H° indicates that the adsorption process is exothermic. The negative sign of G° confirms the spontaneous nature of the adsorption process, physical reaction. [ABSTRACT FROM AUTHOR]

Featured Application: The content of this paper allows a positive assessment of the possibilities of using activated olive stones as a substitute adsorbent for activated carbon in the elimination of organic pollutants. This paper describes a comparative study of the adsorption of methylparaben onto commercial activated carbon and olive stones activated by calcination at 300 °C and treatment with 1 M HCl. The influence of the initial concentration of methylparaben, adsorbent dose, stirring speed and pH on the adsorption capacity of methylparaben on both adsorbents was studied. To find out the isotherm model, the kinetic model and the mechanism that best describe the adsorption process on each adsorbent, the experimental equilibrium data were analyzed using six isotherm models (Langmuir, Freundlich, Elovich, Temkin, Jovanovic and Dubinin–Radushkevich), and the experimental kinetic data were analyzed using four kinetic models (pseudo-first order, pseudo-second order, Elovich and Avrami) and two mechanistic models (Weber–Morris and Boyd). For both adsorbents, the Langmuir model best describes the adsorption equilibrium, the kinetics of the process follow a pseudo-first-order model and boundary layer diffusion is the step that mainly controls the adsorption process. The adsorption capacity of methylparaben on activated carbon is about four times higher than that of activated olive stones. The addition of graphene oxide and reduced graphene oxide to both adsorbents increases their methylparaben adsorption capacity, to a greater extent in the case of graphene oxide, being that increase more important in activated carbon than in activated olive stones. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) coupled with its two modifications HAP P123 and HAP F127 were applied for indium removal from aqueous solutions. Adsorbents' abilities to remove indium ions were assessed in relation to pH, time of contact, indium concentration, temperature, and presence of co-existing ions. Adsorption was discovered to be pH-dependent for all sorbents, with maximum indium ion removal at pH 4.0. Both the Langmuir and the Freundlich isotherm models were used to explain the experimental results. For all adsorbents, the Freundlich isotherm provided a better description of the equilibrium of the sorption. The sorption capacity computed from the Langmuir model changed from 10,799 mg/g for HAP F127 to 11071 mg/g for HAP. A number of models were used to describe the adsorption's kinetics. The adsorption of indium on HAP was better described by the pseudo-second-order model, on HAP P123 by the pseudo-first-order model, and on HAP F127 by the Elovich model. Thermodynamic parameters showed that indium ions' adsorption onto HAP adsorbents was a feasible, spontaneous, and exothermic process. The effectiveness of indium removal by the examined adsorbents was unaffected by the presence of other metal ions in the solutions. ORCA quantum chemistry software was used to theoretically examine the interactions between the surfaces of adsorbents and the indium ions. High desorption efficiency showed that the applied adsorbents can be used for manifold wastewater treatment. [ABSTRACT FROM AUTHOR]

Amberlyst A21 was used for the oleic acid adsorption from sunflower oil (SFO). The impacts of parameters such as contact time, temperature, and mass ratio of adsorbent on oleic acid adsorption were studied. The characterization of Amberlyst A21 before and after adsorption was performed by using Fourier transform infrared spectrometer (FTIR) and scanning electron microscope (SEM). The adsorption reached equilibrium 480 minutes later. The increase in temperature and the amount of adsorbent caused an increase in the amount of adsorbed oleic acid. The adsorption kinetics, isotherms, and thermodynamics were studied. The pseudo-first order kinetics well described the adsorption for all studied temperatures. The Langmuir, Freundlich, and Dubinin-Radushkevich isotherms and thermodynamic analysis were investigated at equilibrium. The suitability of the Langmuir and Freundlich isotherms indicated that the adsorption takes place under monolayer and heterogeneous surfaces. Thermodynamical results showed that adsorption occurs spontaneously and endothermic. [ABSTRACT FROM AUTHOR]

In this study, the adsorption of methyl violet from an aqueous solution using carbonised water lily (CWL) leaves powder as a low-cost, efficient and eco-friendly adsorbent was investigated using a batch system under controlled conditions. The adsorbent's moisture, organic matter, ash, bulk density, pore volume, and pH were determined. The adsorbents were characterised by scanning electron microscopy (SEM) and Fourier Transform Infrared (FT-IR) techniques which confirm the adsorption of the methyl violet onto the CWL adsorbents. The effect of adsorption parameters such as contact time, dosage, initial concentration, pH and temperature were studied for optimisation. It was confirmed that contact time, dosage, concentration, pH and temperature positively affected the adsorption process. The kinetic data were best described by pseudo-second order under all experimental temperatures. The adsorption isotherms were estimated and established to fit nicely into the D-R model compared to other models generated and tested. Thermodynamic studies of the sorption process indicate that the process was feasible, spontaneous, and exothermic and decrease in the randomness of the adsorption process during the transfer of molecules between the adsorbent and adsorbates with entropy (∆S) of 23.77 J/mol.K. due to negative values of Gibb’s free energy observed. This study confirmed that CWL could be employed as a low-cost, eco-friendly adsorbent for removing toxic dyes such as methyl violet from an aqueous solution.

Acetaminophen (C8H9NO2, also called paracetamol) is an active metabolite of phenacetin with antipyretic and analgesic effects and has been extensively used as a painkiller. Currently, the problem of pharmaceuticals in water and sewage is common, especially in highly urbanized countries. Laboratory-scale experiments were carried out using an adsorbent—granulated activated carbon (WD-extra)—to remove acetaminophen (ACT) from water. The initial concentration of acetaminophen was 20 mg ACT/dm3. The adsorption kinetics, influence of the pH on adsorption and dose of the used adsorbent were determined under batch conditions. The adsorption of ACT on activated carbon was more efficient when the water solution was acidic (at pH 2, it was the most effective). The highest percentage of removal (99%) was obtained for the WD-extra dose of 10.0 g/dm3. The time taken to establish the dynamic equilibrium of the system was 60 min. The effectiveness of adsorption was determined based on the Freundlich and Langmuir adsorption isotherms. It was found that WD-extra activated carbon effectively removed ACT from water solutions.

The present study aimed to investigate the potential of a new lignocellulosic biosorbent material derived from mature leaves of sour cherry (Prunus cerasus L.) for removing methylene blue and crystal violet dyes from aqueous solutions. The material was first characterized using several specific techniques (SEM, FTIR, color analysis). Then, the adsorption process mechanism was investigated through studies related to adsorption equilibrium, kinetics, and thermodynamics. A desorption study was also performed. Results showed that the Sips isotherm provided the best fit for the adsorption process of both dyes, with a maximum adsorption capacity of 168.6 (mg g−1) for methylene blue and 524.1 (mg g−1) for crystal violet, outperforming the capacity of other similar adsorbents. The contact time needed to reach equilibrium was 40 min for both studied dyes. The Elovich equation is the most suitable model for describing the adsorption of methylene blue, while the general order model is better suited for the adsorption of crystal violet dye. Thermodynamic analyses revealed the adsorption process to be spontaneous, favorable, and exothermic, with physical adsorption involved as the primary mechanism. The obtained results suggest that sour cherry leaves powder can be a highly efficient, eco-friendly, and cost-effective adsorbent for removing methylene blue and crystal violet dyes from aqueous solutions. [ABSTRACT FROM AUTHOR]

Hexavalent chromium [Cr (VI)] is a highly toxic and hazardous contaminant that poses serious health risks to both humans and the environment. Its presence in water sources can lead to severe health issues, including various types of cancer and respiratory ailments. Therefore, developing efficient and effective methods for Cr (VI) removal is crucial in ensuring safe and clean water supplies. The aim of this research is the environmentally responsible elimination of hexavalent chromium by bioadsorption using corn residues (CR), palm fiber (PF), and the peels of yam (YP), cassava (CP), and cocoa (CH). The study was conducted with varying levels of pH, bioadsorbent quantity, temperature, and adsorbent particle size at 200 rpm, with an initial concentration of 100 mg/L and 24 h of contact time to improve the adsorption efficiency. The process variables were evaluated and optimized using the statistical technique response surface methodology (RSM). The SEM-EDS analysis revealed that the predominant elements in the structure of the bioadsorbents were carbon and oxygen. Furthermore, the adsorption process led to the incorporation of Cr (VI) into the structure of the biomaterials, as indicated by their EDS spectra. The maximal adsorption efficiency of 99.11% was obtained at pH 2, bioadsorbent dose of 0.03 mg, 30 °C, and 0.5 mm of particle size. Various equilibrium isotherms were utilized to fit and analyze the adsorption data. The assessed maximum adsorption capacities were 38.84, 56.88, 52.82, 138.94, and 240,948.7 mg/g for YP, PF, CP, CH, and CR, respectively. The adsorption data exhibited conformity with the Freundlich and Redlich–Peterson isotherm models (R2 = 0.95), indicating that the phenomenon occurs in a multilayer. Pseudo-second order and Elovich kinetic models adjusted the kinetics of chromium (VI), suggesting that the mechanism could be controlled by chemisorption. Therefore, the residual biomasses evaluated can serve as a cost-effective adsorbent for Cr (VI) removal, and the use of RSM enables efficient modeling and prediction of the adsorption process. [ABSTRACT FROM AUTHOR]

This work investigates the potential of utilizing lime peel wastes as a low-cost adsorbent for the adsorption of cadmium ions from aquatic media. The batch system was employed for determining the adsorption performance and optimum operating conditions and parameter values such as feed concentration, adsorbent concentration, the adsorbent particle size, contact time, and initial pH for the feed. The Langmuir, Freundlich, Dubinin-Radushkevich, and Sips isotherm models were examined to evaluate the adsorption results. Regression analysis indicates that the adsorption data is well-fitted to the Freundlich isotherm. Moreover, kinetic analysis of obtained data was carried out using three models including pseudo-first-order, pseudo-second-order, and, Weber-Morris intraparticle diffusion. The pseudo-second-order model fitted the experimental data better than the others. According to thermodynamic analysis, the adsorption of cadmium on lime peel was found to be spontaneous and endothermic. The removal percentage of cadmium reached 90% which proves that lime peel wastes have great potential to be employed as biosorbent for cadmium separation from aqueous media. The regeneration of the loaded adsorbent showed that 77.8% ± 1.6% of the cadmium adsorbed on the adsorbent could be recovered by contacting the adsorbent with a 0.1 M HCl solution after four adsorption-desorption cycle. [ABSTRACT FROM AUTHOR]

This study investigated strontium removal from aqueous solution using electric arc furnace (EAF) slag. Influence of sorbent dosage (0.5–3 g/L), pH (2.5–9.5), initial concentration of Sr2+ (50–300 ppm) and temperature (20°C–45°C) was evaluated. Optimal sorbent dosage and initial Sr2+ concentration were found to be 1.5 g/L and 150 ppm, respectively. Kinetics, equilibrium and thermodynamic models were used to analyse the data. Kinetics of Sr2+ adsorption onto EAF slag was evaluated using pseudo-first-order and pseudo-second-order models and results have shown that experimental data had a better fit with the pseudo-second-order model. Langmuir and Freundlich isotherm models were used for evaluating the adsorption equilibrium and it has been shown that Langmuir model better described isotherm data. Maximal adsorption capacities of 111.11, 129.87 and 156.25 mg/g were obtained at 20°C, 30°C and 45°C, respectively. Thermodynamic investigation indicated that adsorption of Sr2+ onto EAF slag is endothermic in nature, spontaneous and more favorable at higher temperatures. [ABSTRACT FROM AUTHOR]

Elemental sulfur (S8) is a corrosive sulfur compound which was found to be extremely reactive to silver, causing intensive silver sulfide (Ag2S) deposition on on-load tap changer (OLTC) contacts in power transformers. A highly selective adsorbent (HSA), called Tesla'Ssorb, for the removal of S8 from mineral insulating oils was prepared from raw material (RM) using the novel procedure. In this study, the adsorption properties of HSA for the removal of S8 from the oil were determined. RM and HSA were characterized using various techniques, such as field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD). The performance of HSA was determined by adsorption equilibrium, thermodynamic, and kinetic study through batch experiments, at various temperatures and initial concentrations of S8. The obtained results were analyzed by Langmuir and Freundlich adsorption isotherms and it was found that equilibrium data were fitted better with the Langmuir isotherm model. The maximum adsorption capacity was 4.84 mg of S8/g of HSA at 353 K. Thermodynamic parameters, such as enthalpy (ΔH°), Gibbs free energy (ΔG°), and entropy (ΔS°), were calculated and it was found that the sorption process was spontaneous (ΔG° < 0) and endothermic in nature (ΔH° > 0). It was found that the adsorption of S8 follows pseudo-second-order kinetic model, and the activation energy indicated the activated chemisorption process. [ABSTRACT FROM AUTHOR]

Colour removal from effluents remains one of the most challenging requirements faced by industries due to the difficulty of degrading dyes which consequently escape conventional wastewater treatment processes and persist in the environment. This study aimed to assess and optimise the dye adsorption performance of banana floret, a novel biosorbent. Batch experiments were conducted to assess the effects of particle size, pH, agitation, temperature, initial concentration and sorbent dose. Kinetic and equilibrium data were modelled, and mass transfer studies were conducted to elucidate the mechanisms of biosorption. Equilibrium data were best simulated using the Sips and Langmuir isotherm models. At an optimum pH of 6.0, biosorbent dose of 1.0 mg·L–1 and temperature of 300 K, a maximum sorption capacity of 219 mg·g–1 was observed. The kinetic data were best represented by the pseudo-second-order model. The dominant transport mechanism was attributed to intraparticle diffusion, while the dominant attachment mechanism was physical sorption. The Taguchi method, in combination with analysis of variance, was used to determine the optimum levels of operational parameters for maximising the biosorption of methylene blue by banana floret. The parameter group which produced the highest biosorption capacity and percent removal was determined to be A3-B1-C3 (initial concentration = 200 mg·L–1, biosorbent dose = 500 mg·L–1, contact time = 60 min) and A1-B3-C3 (initial concentration = 50 mg·L–1, biosorbent dose = 2000 mg·L–1, contact time = 20 min), respectively. Among these parameters, the initial concentration had the most significant effect on the biosorption capacity, while sorbent dose was most significant on percent removal. A predictive model based on a quadratic equation which incorporates the factor interactions was successfully developed and validated. [ABSTRACT FROM AUTHOR]

It is infrequent to have a single metal in the wastewater. For this reason, the elimination of Pb2+ and Cd2+ in one and two-component system was examined by xanthate-modified Phaseolus vulgaris in a batch mode. Through grafting, sulphur-bearing groupings with the help of magnesium xanthate were added onto P. vulgaris and xanthate-modified innovative P. vulgaris biosorbent has been produced for the removal of metal ions, that is, lead and cadmium. These innovative sulphur sites were attained successfully and confirmed with the help of Fourier-transform infrared spectroscopy, elemental analysis, and change in surface morphology by scanning electron microscopy. The point of zero charges pHpzc of xanthate-modified P. vulgaris was observed to be 7.20 which makes it appropriate for the sorption of cations. The batch sorption implementation of xanthate-modified P. vulgaris includes sorbent amount, pH, linear and non-linear regression analysis, and kinetic curves. The xanthate-modified P. vulgaris adsorbed 95.65% cadmium (at pH 4.0) and 90.36% of lead (at pH 5.0) from a single aqueous system. The sorption of Pb2+ and Cd2+ by xanthate-modified P. vulgaris follow the linear regression of Langmuir isotherm with qmax of 160.97 and 150.50 mg/L, respectively which is substantially greater than that of many other reported ones. The xanthate-modified P. vulgaris demonstrated rapid uptake capacity of Pb2+ and Cd2+ following the high value of correlation coefficient with pseudo-second-order kinetics. This sorption process for Pb2+ and Cd2+ was found to be endothermic and spontaneous. The binding capacities however reduced in the binary system. This, therefore revealed that the xanthate-modified P. vulgaris can be an encouraging biosorbent for the remediation of Pb2+ and Cd2+ from contaminated water. [ABSTRACT FROM AUTHOR]

The adsorption behaviour of gadolinium on grafted co-polymers was evaluated. Batch tests, such as effects of adsorbent weight, shaking times at various temperatures, and initial gadolinium (III) concentration, were used to evaluate the adsorption behaviour. The best results were obtained using 5.5 pH and 400 mg/L of gadolinium as an initial concentration. According to the experimental data, the adsorption capacities of prepared polymers have been improved by addition of silica (powder and gel form). The capacity of the (poly acrylamide-acrylic acid-sodium styrene sulphonate) is 129.36 mg/g which improved to 158.48 and 168.07 for (poly acrylamide-acrylic acid- sodium styrene sulphonate-silica powder) and (poly acrylamide-acrylic acid- sodium styrene sulphonate-silica gel), respectively. The polymer (poly(sodium styrene sulphonate)-(silica gel)–acrylic acid-polyacrylamide) [P-SG] has a high adsorption capacity and the adsorption statistics are more closely related to the Langmuir model. Monolayer capacities of the three prepared polymers are 133.33, 184.8 and 206.61 mg/g. The rate of gadolinium removal improved as the temperature rose, indicating that the sorption process is endothermic. The results of experiments were matched using pseudo-second order based on the kinetics model evaluated results. The mechanism may be chemically sorption. [ABSTRACT FROM AUTHOR]

Binding kinetics has become a popular topic in pharmacology due to its potential contribution to the selectivity and duration of drug action. Yet, the overall kinetic aspects of complex binding mechanisms are still merely described in terms of elaborate algebraic equations. Interestingly, it has been recommended some 10 years ago to examine such mechanisms in terms of binding fluxes instead of the conventional rate constants. Alike the velocity of product formation in enzymology, those fluxes refer to the velocity by which one target species converts into another one. Novel binding flux‐based approaches are utilized to get a better visual insight into the "competition" between two drugs/ligands for a single target as well as between induced fit‐ and conformational selection pathways for a single ligand within a thermodynamic cycle. The present data were obtained by differential equation‐based simulations. Early on, the ligand‐binding steps "race" to equilibrium (i.e., when their forward and reverse fluxes are equal) at their individual pace. The overall/global equilibrium is only reached later on. For the competition association assays, this parting might produce a transient "overshoot" of one of the bound target species. A similar overshoot may also show up within a thermodynamic cycle and, at first glance, suggest that the induced fit pathway dominates. Yet, present findings show that under certain circumstances, it could rather be the other way round. Novel binding flux‐based approaches offer visually attractive insights into crucial aspects of "complex" binding mechanisms under non‐equilibrium conditions. [ABSTRACT FROM AUTHOR]

The study on the biosorption of copper ions using raw eggshells as an adsorbent is presented in this paper. The influence of different process parameters, such as: initial pH value of the solution, initial Cu2+ ions concentration, initial mass of the adsorbent, and stirring rate, on the biosorption capacity was evaluated. The SEM-EDS analysis was performed before and after the biosorption process. SEM micrographs indicate a change in the morphology of the sample after the biosorption process. The obtained EDS spectra indicated that K, Ca, and Mg were possibly exchanged with Cu2+ ions during the biosorption process. The equilibrium analysis showed that the Langmuir isotherm model best describes the experimental data. Four kinetic models were used to analyze the experimental data, and the results revealed that the pseudo-first order kinetic model is the best fit for the analyzed data. Calculated thermodynamic data indicated that the biosorption process is spontaneous, and that copper ions are possibly bound to the surface of the eggshells by chemisorption. The biosorption process was optimized using Response Surface Methodology (RSM) based on the Box-Behnken Design (BBD), with the selected factors: adsorbent mass, initial metal ion concentration, and contact time. [ABSTRACT FROM AUTHOR]

In this study, a plant-based adsorbent was used in order to remove lead, nickel, cobalt and cadmium metals from a wastewater sample collected from Sungun mine real wastewater. The biosorbent was one of the most abundant native plants of the Sungun region, named Chrysopogon zizanioides (C. zizanioides). The root powder of C. zizanioides was used in order to remove heavy metals from the wastewater sample. The biosorbent was characterized by FTIR, SEM, HR-TEM, EDS, BET and ZPC analyses. The effect of pH, initial metals concentrations, contact time and temperature on the biosorption process were accurately investigated. The metal concentrations were significantly reduced to lower concentrations after the biosorption process, which indicated that the C. zizanioides root powder removal efficiency was more than 95% for the metals from the wastewater sample, with maximum adsorption capacities of 31.78, 21.52, 26.69 and 27.81 mg/g, for Pb(II), Co(II), Cd(II) and Ni(II) ions, respectively. Furthermore, the adsorption kinetic results showed that the pseudo-second-order kinetic model correlated with the experimental data well, with correlation coefficient values of 1 for all metals. Isotherm studies illustrated that the Freundlich and Dubinin-Radushkevich (D-R) isotherm models could describe the obtained equilibrium data well. Moreover, from the D-R model, it was found that the biosorption type was physical. The thermodynamic studies demonstrated that the metals' biosorption was an exothermic and spontaneous process. Moreover, the reusability of the biosorbent to be used in several successive cycles, and also the percentage of recovery of adsorbed metals from the biosorbent, was investigated. Altogether, being simple and cost-effective and having a high adsorption rate, fast kinetics, easy separation and high reusability prove that C. zizanioides root powder shows significant performance for the removal of heavy metals from waste effluents. [ABSTRACT FROM AUTHOR]

In this study, the effect of bean husk, which is abundant in our country as agricultural waste, on methylene blue adsorption was investigated. XRD, SEM and FTIR analyzes were carried out to determine the surface properties of the adsorbent. Within the scope of adsorption studies, the effects of methylene blue concentration, amount of adsorbent, temperature and contact time were studied. Langmuir, Freundlich and Temkin isotherm models were investigated to define the adsorption isotherm. The pseudo-first-order, pseudo-second-order and Avrami models and the adsorption of methylene blue on the bean husk were evaluated in terms of kinetics. It has been determined that the isotherm graphs prepared by using the data obtained as a result of the experimental studies are more compatible with the Freundlich isotherm models. After kinetic studies in the adsorption of methylene blue with bean husk, it is seen that it conforms to the pseudo-second-order kinetic model. Accordingly, it can be said that the adsorption takes place in a multilayered and heterogeneous manner. This result is in agreement with the layered structure in the SEM image of the bean shell. As a result of the studies, it has been revealed that bean husk can be used as an adsorbent in the removal of methylene blue dyestuff that can be found in textile wastewater. [ABSTRACT FROM AUTHOR]