Maximum Adsorption Capacity Research Articles

Lanthanum-based magnetic biopolymers for brilliant green removal from aqueous solutions.

In this study, lanthanum (La)-based magnetic biopolymers were synthesized, and the first adsorption study was conducted on the removal of brilliant green dye from aqueous water with these biopolymers. For the adsorption study, adsorption parameters were investigatedandthe ideal adsorption conditions determined for the removal of brilliant green dye from aqueous solutions are pH 11, t 60min, m 10mg, C0 25mg/L, T 298K. It was determined that the adsorption process was compatible with the single-layer Langmuir isotherm, and maximum adsorption capacity obtained according to the Langmuir isotherm was calculated as 256.41mg/g. The adsorption process was found to be in accordance with the pseudo-second-order, and the adsorption process was explained by intra-particle diffusion. According to studies of adsorption thermodynamics, it has been established that the nature of the adsorption reaction is spontaneous, and this process is endothermic and has increasing randomness. Moreover, the reusability of magnetic lanthanum/alginate (La/Alg) biopolymers was investigated, and it was determined that the biopolymers could be used successfully. In summary, brilliant green dye has been successfully removed with simple, low-cost, environmentally friendly, and easily obtained magnetic La/Alg biopolymers. It can be stated that even low amounts of these biopolymers can be effective in the treatment of highly concentrated dye wastewaters.

Enhancing environmental sustainability: Butea monosperma leaves as a key component in WO3-based composites for water purification and therapeutic applications.

In this research, a novel nano-biocomposite material, namely, tungsten trioxide-Butea monosperma leaf powder (WO3@BLP), is an effective and eco-friendly adsorbent used for the mitigation of congo red (CR) and crystal violet (CV) dyes from its aqueous phase. The as-prepared WO3@BLP was characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), DLS analysis, and TGA. Many factors such as solution pH, WO3@BLP dose, temperature, contact time, and initial CR/CV dye concentrations were exploited to monitor the adsorption efficiency of WO3@BLP composites. The biosorption of both CR and CV dyes followed the Langmuir isotherm, with maximum adsorption capacities (qmax) reaching 84.91 mg g-1 for CR at pH 2.3 and 162.75 mg g-1 for CV at pH 8, fitting of kinetics data to the PSO model with closed values of qeexp (mg g-1) and qecal (mg g-1), i.e., 25.69 to 25.38 mg g-1 for CR dye and 29.06 to 29.08 mg g-1 for CV dye. The interaction mechanism behind the adsorption of CR and CV dyes onto the WO3@BLP bionanocomposite includes electrostatic interaction and surface complexation. The synthesized materials were tested for antifungal activity against three different Candida cells, i.e., C. albicans ATCC 90028, C. glabrata ATCC 90030, and C. tropicalis ATCC 750, by using broth dilution method on the minimum inhibiting concentration (MIC). Furthermore, the cytotoxicity of nano-formulated WO3@BLP was studied by in vitro hemolytic assay on a human host. Overall, this research presents a pioneering nano-biocomposite, WO3@BLP, as a sustainable adsorbent for CR and CV dye removal, adhering to Langmuir isotherm and pseudo-second-order kinetics. Its multifaceted approach includes elucidating interaction mechanisms, demonstrating antifungal activity, and assessing cytotoxicity, marking a significant advancement in environmental remediation.

Sulphonated date palm (Phoenix dactylifera) stone via microwave‑assisted H2SO4 activation: optimisation with desirability function for methylene blue adsorption

ABSTRACT In this work, a sulphonated date palm (Phoenix dactylifera) stone (SDPS) was produced as a cost-effective and renewable adsorbent for the removal of a cationic dye called methylene blue (MB). The production process involved the use of microwave irradiation combined with H2SO4 activation under the condition of 600 W microwave radiation for 15 min. The physicochemical characteristics of SDPS were evaluated using various analytical techniques, including XRD, BET, FTIR, pHpzc, and SEM. The Box-Behnken design (BBD) was employed to optimise key adsorption variables, including A: SDPS dosage (0.02–0.1 g/100 mL), B: pH (4–10), and C: contact time (5–25) min. According to the BBD model, the most effective removal of MB (98.4%) occurred with a dosage of 0.06 g/100 mL of SDPS, a pH of 10, and a contact time of 25 min. The rate of adsorption of the MB dye followed a pseudo second order (PSO) model, whereas the equilibrium adsorption was described by the Langmuir and Temkin models. The maximum adsorption capacity (q max ) of SDPS for MB dye was found to be 122.3 mg/g at 25°C. Several contributions to the MB dye adsorption process include electrostatic interactions, H-bonding, pore filling, and π-π stacking onto the SDPS adsorbent surface.

Experimental design of polymer synthesis applied to the removal of Cd2+ ions from water via adsorption

Cadmium is a highly toxic metal, and its presence can have adverse effects on both human health and aquatic ecosystems. The efficient removal of cadmium from wastewater is therefore of crucial importance, but traditional methods have proved to be inadequate. Thus, technologies for the treatment of wastewater containing cadmium, including adsorption, have been developed. The aim of this study was the preparation of a polymeric material by the grafting reaction of κ-carrageenan and its use as an adsorbent for cadmium removal. This was performed to study the removal capacity of cadmium ions in synthetic solutions, as well as the effects of pH and ions on adsorption capacity, adsorption kinetics, isotherms, and reusability. Additionally, the disinfectant potential of the solution was evaluated for the inactivation of total coliforms and E. coli in river water. The best adsorption capacity was 75.52 ± 1.325 mg g−1, with the kinetics described by the pseudo-second order model. Maximum adsorption capacity (127.6 ± 1.833 mg g−1) and RL (0.0113) were determined using the Langmuir model, the Freundlich model was the one that best fits the experimental data and indicated cooperative adsorption, and the Dubinin-Radushkevich isotherm was used to obtain the adsorption energy and identify that it is physical. The presence of ions K+, Na+, Mg2+, and Ca2+ in a concentration of 0.5% decreased the adsorption capacity, and that at pH 2.0, the adsorption capacity was drastically reduced. The study indicates that the polymer has potential as an adsorbent for removing cadmium from aqueous solutions and exhibits self-disinfecting properties.

Efficient Adsorption and Elimination of Tm3+ For Enhanced Seed Germination Using Pillar[5]Arene Polymer.

While rare earth elements (REEs) are essential for modern technology, their production methods raise concerns for agriculture. Researchers are now exploring ways to control and recycle REEs pollution, aiming to minimize agricultural impacts and potentially even develop methods to utilize these elements for improved crop yields. Regarding this issue, a new type of pillar[5]arene polymer (Pol-P[5]-BTZP) has been designed and synthesized by click reaction to enhance the efficiency of adsorption and recovery of rare earth metals. This polymer incorporates the unique structure of 2,6-di-1,2,3-triazolyl-pyridine. The results of various analyses revealed that Pol-P[5]-BTZP exhibits excellent thermal stability, a high specific surface area, and well-distributed networks of micropores and mesoporous structures. The adsorption capacity of Pol-P[5]-BTZP for Tm3+, a representative REE, was evaluated using the Langmuir and Freundlich isothermal adsorption models with a maximum adsorption capacity (Qmax) of 127.71 mg/g. Furthermore, the versatility of Pol-P[5]-BTZP in adsorption and recovering various REEs was tested. In addition to its adsorption capabilities, the potential of Pol-P[5]-BTZP for rare earth recovery and reuse was assessed through experiments on the impact of Tm3+ and La3+ on seed germination. These experiments demonstrated the wide-ranging applicability of Pol-P[5]-BTZP in recovering and reusing REEs for green agriculture.

Adsorptive flotation of cesium radionuclides from aqueous solutions using rice straw agriculture waste as a low-cost and eco-friendly adsorbent

ABSTRACT The removal of caesium radionuclides from an aqueous solution by flotation using rice straw (RS) agricultural waste as a low-cost and eco-friendly adsorbent in the presence of potassium ferrocyanide (KFC) was investigated. The influence of many adsorption parameters and flotation was evaluated on the removal efficiency of 137Cs. The adsorption results demonstrated that the concerned radionuclide was efficiently removed in the presence of 2 × 10−4 mol/L KFC using 10 g/L RS at pH ≥ 7. The double exponential kinetic model and the Freundlich model were the best models for fitting the adsorption kinetic and isotherm data, respectively. The maximum adsorption capacity of RS, calculated from the Langmuir model, was 280.405 mg/g. after being transferred to the flotation cell, 137Cs loaded onto ferrocyanide-modified rice straw (FMRS) was successfully floated at pH 7 using 3 × 10−4 mol/L cetyltrimethylammonium bromide (CTAB) surfactant in the presence of 4% ethanol. Removal percentages of 56% and > 99.5% were achieved for 137Cs-loaded FMRS within 5 min using sodium dodecyl sulphate (SDS) and CTAB, respectively. The results obtained in this investigation indicate the efficiency of the suggested strategy and hence its applicability for the removal of 137Cs+ from radioactive liquid wastes.

Efficient removal of Pb(II) and Cd(II) ions from wastewater using amidoxime functionalized graphene oxide

AbstractThis study aimed to develop iminodiethylamine oxime graphite oxide (IOGO) through the grafting of iminodiethylamine oxime onto graphene oxide (GO) via amidation and oximation. The primary objective was to investigate the adsorption characteristics of Pb(II) and Cd(II) ions on IOGO. Results demonstrated that IOGO exhibited exceptional adsorption capabilities, reaching maximum adsorption capacities of 798.87 mg/g for Pb(II) and 283.50 mg/g for Cd(II). Remarkably, IOGO maintained its high adsorption performance over five consecutive adsorption cycles. Specifically, the adsorption capacity for Pb(II) remained significantly stable at 480.78 mg/g, exhibiting only an 8.77% decrease. Similarly, the Cd(II) adsorption capacity remained robust at 204.13 mg/g, demonstrating a modest reduction of 10.47%. These findings underscore the feasibility of employing IOGO in repeated adsorption processes, thereby showcasing its potential for practical applications in the removal of heavy metals from aqueous solutions.

Enhanced Adsorption of Arsenate from Contaminated Waters by Magnesium-, Zinc- or Calcium-Modified Biochar—Modeling and Mechanisms

The adsorption of arsenate from wastewaters was investigated by applying Mg-, Zn- or Ca-modified nut residue biochar activated by nitrogen/steam. The parameters studied were the contact time, adsorbent dose, initial arsenate concentration and solution pH. The adsorption mechanism was investigated. Various analyses of the material before and after arsenate adsorption were carried out, and experimental data were simulated by applying two isotherm models. The results indicated that the maximum removal efficiency of arsenate was 29.4% at an initial concentration of 10 mg/L. The modification of biochar by Mg, Zn or Ca oxides increased the removal rate significantly, from 49.4% at 100 mg/L As5+ up to 8%, 97% and 97%, respectively. Zn-modified biochar presented an excellent performance for both low and high As5+ concentrations. All experimental data were accurately fitted by the Freundlich isotherm model (R2 = 0.94–0.97), confirming a multilayer adsorption mechanism. For a biochar dose of 2 g/L, the maximum capacity of adsorption was enhanced after Mg-, Zn- or Ca-modification from 12.4 mg/g to 35 mg/g, 50 mg/g and 49 mg/g, respectively. The potential mechanisms of adsorption were ligand exchange, chemical complexation, surface precipitation and electron coordination.

Application of Natural Antibacterial Plants in the Extraction of Uranium from Seawater.

Marine biofouling directly affects the performance and efficiency of uranium (U(VI)) extraction from seawater. Compared to traditional chemical methods, natural plant extracts are generally biodegradable and nontoxic, making them an environmentally friendly alternative to synthetic chemicals in solving the marine biofouling problem. The effectiveness of natural antibacterial plants (i.e., pine needle, peppermint, Acorus gramineus Soland, Cacumen platycladi, and wormwood) in solving the marine biofouling problem was evaluated in this work. Experimental results showed that natural antibacterial plants could kill Vibrio alginolyticus in solution and effectively solve the marine biofouling problem of U(VI) extraction. To improve the adsorption capacity of natural plants for U(VI) in seawater, poly(vinylphosphonic acid) (PVPA) was modified on natural antibacterial plant surfaces by irradiation grafting technology. PVPA and natural antibacterial plants work as active sites and base materials for the U(VI) extraction material, respectively. The recovery performance of PVPA/pine needle for U(VI) was preliminarily studied. Results show that the adsorption of U(VI) on PVPA/pine needle follows pseudo-second-order and Langmuir models, and the maximum adsorption capacity is 111 mg/g at 298 K and pH 8.2.

Carbonation of waste concrete: An effective and green strategy for enhancing its heavy metals removal from wastewater

Water pollution, especially Pb2+, Cd2+, Co2+, and Ni2+ released from industrial and mine wastewater, harms human health and is a global environmental concern. At the same time, the effective disposal of waste concrete originating from constructs is a global challenge. In this study, carbonated recycled concrete powder (CRP) is efficiently prepared by carbonizing waste concrete powder, which not only might enhance its adsorptive performance but also sequestrate CO2 in the form of mineral carbon. Characterization techniques revealed CRP forms calcium carbonate and highly polymerized silica gel. Batch adsorption experiments indicate that the CRP is found to have strong adsorption properties. The maximum equilibrium adsorption capacities calculated by the Langmuir model were determined as 997.03, 199.56, 148.85, and 76.69 mg/g for Pb2+, Cd2+, Co2+, and Ni2+, respectively, outperforming most waste concrete and industrial wastes reported. The adsorption mechanism mainly includes electrostatic interactions, precipitation, and ion exchange. This study proposes a method to synthesize low cost, good performance, high chemical stability, and facile preparation adsorbent using waste concrete powder, with promising applications in wastewater treatment.

Surfactant-Modified Bolivian Natural Zeolite for the Adsorption of Cr (VI) from Water

The present study reports the surfactant modification of Bolivian natural zeolite with hexadecyltrimethylammonium bromide (HTDMA-Br) for the adsorption of hexavalent chromium Cr (VI) anions from water. The surfactant-modified natural zeolite was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and Fourier-transform infrared spectroscopy (FTIR) to analyze the effect of its modification with HTDMA-Br and to verify its charge on the zeolite surface. We report a maximum adsorption capacity of 17 mg/g of Cr (VI) anions, surpassing the findings of some of the previous investigations on surfactant-modified natural zeolites of different geological origins. The analysis of the equilibrium data described the Cr (VI) anions adsorption by Langmuir isotherm and the pseudo second-order kinetic model. In addition, thermodynamics revealed an exothermic adsorption. Furthermore, anion exchange, electrostatic attraction, and chemical reduction were indicated to be dominating sorption mechanisms by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) characterization techniques.

Co/Ni/Cu-NH2BDC MOF@natural Egyptian zeolite ore nanocomposite for calcium ion removal in water softening applications.

Water softening is a treatment process required to remove calcium (Ca(II)) and magnesium (Mg(II)) cations from water streams. Nanocomposites can provide solutions for such multiple challenges and have high performance and low application costs. In this work, a multimetallic cobalt, nickel, and copper 2-aminoterephthalic acid metal-organic framework ((Co/Ni/Cu-NH2BDC) MOF) was synthesized by a simple solvothermal technique. This MOF was supported on an Egyptian natural zeolite ore and was used for the adsorption of Ca(II) ions for water-softening applications. The adsorbent was characterized using Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), N2 adsorption-desorption isotherms, and zeta potential measurements. The adsorption isotherm data for the prepared adsorbent toward Ca(II) were best fit using the Redlich-Peterson model and showed a maximum adsorption capacity of 88.1 mg/g. The adsorption kinetics revealed an equilibrium time of 10 min, which was best fit using the Avrami model. The intermolecular interactions of Ca(II) ions with zeolite and MOF were investigated by Monte Carlo simulations, molecular dynamics simulations, and FTIR and XRD analyses. The adsorption sites in the zeolite structure were oxygen atoms, while those in the MOF structure were amine nitrogen atoms. The Ca(II) ions are coordinated with the solvent molecules in both structures. Finally, the in vitro cytotoxicity of this nanocomposite was assessed, revealing viability levels of 74.57 ± 2.1% and 21 ± 2.79% for Vero and African green monkey kidney and human liver (HepG2) cells, respectively. Cytotoxicity assays help assess the environmental impact of these materials, ensuring that they do not harm aquatic organisms or disrupt ecosystems. Thus, this study demonstrated the valorization of MOF/zeolite as a valuable and industry-ready adsorbent that can appropriate Ca(II) contaminants from aqueous streams.

Highly Adsorptive Organic Xerogels for Efficient Removal of Metformin from Aqueous Solutions: Experimental and Theoretical Approach

Metformin, widely prescribed to treat type 2 diabetes for its effectiveness and low cost, has raised concerns about its presence in aqueous effluents and its potential environmental and public health impacts. To address this issue, xerogels were synthesized from resorcinol and formaldehyde, with molar ratios ranging from 0.05 to 0.40. These xerogels were thoroughly characterized using FT-IR, SEM, TGA, and TEM analyses. Batch adsorption experiments were performed with standard metformin solutions at concentrations of 50 and 500 mg/L, varying pH, and temperature to determine the adsorption isotherms of the synthesized xerogels. The adsorption data revealed a maximum adsorption capacity of 325 mg/g at pH 11 and 25 °C. Quantum chemical calculations revealed that electrostatic interactions govern metformin adsorption onto xerogels. The xerogels’ adsorption capacity was evaluated in competitive systems with CaCl2, NaCl, MgCl2, and synthetic urines. Reuse cycles demonstrated that xerogels could be reused for up to three cycles without any loss in adsorptive efficiency. The adsorption mechanisms of metformin in the adsorption process highlight the strong electrostatic interactions and hydrogen bonds between the adsorbate and the adsorbent material. Xerogels synthesized show promise as efficient adsorbents to remove metformin from aqueous solutions, helping to mitigate its environmental impact.

Preparation of 6-Amino-N-Hydroxyhexanamide-Modified Porous Chelating Resin for Adsorption of Heavy Metal Ions

Abstract: The pollution of water bodies by heavy metal ions has recently become a global concern. In this experiment, a novel chelating resin, D851-6-AHHA, was synthesized by grafting 6-amino-N-hydroxyhexanamide (6-AHHA) onto the (-CH2N-(CH2COOH)2) group of the D851 resin, which contained a hydroxamic acid group, amide group, and some carboxyl groups. This resin was developed for the purpose of removing heavy metal ions, such as Cr(III) and Pb(II), from water. The findings from static adsorption experiments demonstrated the remarkable adsorption effectiveness of D851-6-AHHA resin towards Cr(III) and Pb(II). Specifically, the maximum adsorption capacities for Cr(III) and Pb(II) were determined to be 91.50 mg/g and 611.92 mg/g, respectively. Furthermore, the adsorption kinetics of heavy metal ions by D851-6-AHHA resin followed the quasi-second-order kinetic model, while the adsorption isotherms followed the Langmuir model. These findings suggest that the adsorption process was characterized by monolayer chemisorption. The adsorption mechanism of D851-6-AHHA resin was comprehensively investigated through SEM, XRD, FT-IR, and XPS analyses, revealing a high efficiency of D851-6-AHHA resin in adsorbing Cr(III) and Pb(II). Specifically, the (-C(=O)NHOH) group exhibited a notable affinity for Cr(III) and Pb(II), forming stable multi-elemental ring structures with them. Additionally, dynamic adsorption experiments conducted using fixed-bed setups further validated the effectiveness of D851-6-AHHA resin in removing heavy metal ions from aqueous solutions. In conclusion, the experimental findings underscored the efficacy of D851-6-AHHA resin as a highly efficient adsorbent for remediating water bodies contaminated by heavy metal ions.

Highly Adsorptive Organic Xerogels for Efficient Removal of Metformin from Aqueous Solutions: Experimental and Theoretical Approach

Metformin, widely prescribed to treat type 2 diabetes for its effectiveness and low cost, has raised concerns about its presence in aqueous effluents and its potential environmental and public health impacts. To address this issue, xerogels were synthesized from resorcinol and formaldehyde, with molar ratios ranging from 0.05 to 0.40. These xerogels were thoroughly characterized using FT-IR, SEM, TGA, and TEM analyses. Batch adsorption experiments were performed with standard metformin solutions at concentrations of 50 and 500 mg/L, varying pH, and temperature to determine the adsorption isotherms of the synthesized xerogels. The adsorption data revealed a maximum adsorption capacity of 325 mg/g at pH 11 and 25 °C. Quantum chemical calculations revealed that electrostatic interactions govern metformin adsorption onto xerogels. The xerogels’ adsorption capacity was evaluated in competitive systems with CaCl2, NaCl, MgCl2, and synthetic urines. Reuse cycles demonstrated that xerogels could be reused for up to three cycles without any loss in adsorptive efficiency. The adsorption mechanisms of metformin in the adsorption process highlight the strong electrostatic interactions and hydrogen bonds between the adsorbate and the adsorbent material. Xerogels synthesized show promise as efficient adsorbents to remove metformin from aqueous solutions, helping to mitigate its environmental impact.

Preparation of PVP-BiOBr Adsorbent for Efficient Indigo Carmine Dye Removal Using Flow-Circulation Systems.

This work presents an adsorptive removal of indigo carmine (IC) dye using a polyvinylpyrrolidone capped bismuth oxybromide (PVP-BiOBr) adsorbent. PVP-BiOBr was synthesized via a simple precipitation method. The morphology and surface chemical structure of the adsorbent were characterized using XRD, SEM, FTIR, and BET analyses. The adsorption isotherm and kinetics were investigated to reveal the mechanism of dye removal. Prepared PVP-BiOBr has a crystallite size of 19.7 nm, with a mean particle size of ∼2 μm and a surface area of 5.14 m2 g-1. The optimum pH for this adsorptive process spanned the range of 4 to 9. Experimental data indicated applicability of the Langmuir isotherm model, and the study confirms a pseudo-second-order kinetics model. The maximum adsorption capacity for IC dye was 208.3 mg g-1. A flow-circulation system was developed for the treatment of IC dye contaminated water samples. PVP-BiOBr was packed inside a column and did not spill into the water sample after treatment. The removal efficiency was ≥90% after 25 min. The PVP-BiOBr adsorbent could be reused for three cycles. This work demonstrates that PVP-BiOBr is a promising candidate as an adsorbent for IC dye removal. Additionally, the flow-based system establishes an automated operation in continuous mode, which is viable for large scale applications.

Preparation of 6-Amino-N-Hydroxyhexanamide-Modified Porous Chelating Resin for Adsorption of Heavy Metal Ions

Abstract: The pollution of water bodies by heavy metal ions has recently become a global concern. In this experiment, a novel chelating resin, D851-6-AHHA, was synthesized by grafting 6-amino-N-hydroxyhexanamide (6-AHHA) onto the (-CH2N-(CH2COOH)2) group of the D851 resin, which contained a hydroxamic acid group, amide group, and some carboxyl groups. This resin was developed for the purpose of removing heavy metal ions, such as Cr(III) and Pb(II), from water. The findings from static adsorption experiments demonstrated the remarkable adsorption effectiveness of D851-6-AHHA resin towards Cr(III) and Pb(II). Specifically, the maximum adsorption capacities for Cr(III) and Pb(II) were determined to be 91.50 mg/g and 611.92 mg/g, respectively. Furthermore, the adsorption kinetics of heavy metal ions by D851-6-AHHA resin followed the quasi-second-order kinetic model, while the adsorption isotherms followed the Langmuir model. These findings suggest that the adsorption process was characterized by monolayer chemisorption. The adsorption mechanism of D851-6-AHHA resin was comprehensively investigated through SEM, XRD, FT-IR, and XPS analyses, revealing a high efficiency of D851-6-AHHA resin in adsorbing Cr(III) and Pb(II). Specifically, the (-C(=O)NHOH) group exhibited a notable affinity for Cr(III) and Pb(II), forming stable multi-elemental ring structures with them. Additionally, dynamic adsorption experiments conducted using fixed-bed setups further validated the effectiveness of D851-6-AHHA resin in removing heavy metal ions from aqueous solutions. In conclusion, the experimental findings underscored the efficacy of D851-6-AHHA resin as a highly efficient adsorbent for remediating water bodies contaminated by heavy metal ions.

Development of a sustainable adsorption system based on alginate-encapsulated clay for pharmaceutical pollutant capture in aqueous solution using Box–Behnken methodology

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

Adsorption performance of 1,4-dioxane by MCM-22 and Beta zeolites and their bio-zeolite composite system in the presence of co-contaminants

Addressing the significant challenge of efficiently separating 1,4-dioxane from aquatic environments using traditional adsorbents is crucial. In this study, we evaluated the adsorption performance of MCM-22 and Beta zeolites. Both were identified as highly effective adsorbents. Equilibrium adsorption of 1,4-dioxane was achieved within 20 min for an initial concentration of 500 mg L-1 on both MCM-22 and Beta zeolites. At 288 K, the maximum adsorption capacities fitted by Langmuir isotherm were 79.66 mg g−1 for MCM-22 and 121.66 mg g−1 for Beta zeolite. Fixed-bed column studies demonstrated that the Yan model properly predicted the behavior of both zeolites under varying flow rates. Additionally, MCM-22 exhibited a wider pore size distribution compared to Beta zeolite, while Beta zeolite demonstrated a higher volume of ultra-micropores (<1 nm) than MCM-22. This highlights the importance of pore volume filling in facilitating excellent adsorption of 1,4-dioxane by both zeolites. Further analysis via FTIR and 1H NMR confirmed the significance of Brønsted acid sites in 1,4-dioxane adsorption. The adsorption performance of both zeolites remained unaffected by initial pH values ranging from 2 to 11, as well as variations in ionic strength or the presence of natural organic matter (NOM) for both zeolites. However, the co-existence of 1,1-dichloroethene (1,1-DCE) resulted in competitive adsorption with 1,4-dioxane, leading to a notable decrease in adsorption capacity of 1,4-dioxane. In contrast, the presence of metal ions Cu2+ and Ag+ did not compete for adsorption sites with 1,4-dioxane. Our study demonstrated the effectiveness of the bio-zeolite system in regenerating spent adsorbents, surpassing water and solvent regeneration methods in efficiency and recyclability. Although addressing the persistence of 1,1-DCE remains a challenge, bio-zeolites emerge as versatile tools for mitigating the bio-inhibition of heavy metals, such as Cu2+ and Ag+, while offering a sustainable solution for 1,4-dioxane bioremediation.

Sulfonate-bridged semi-biopolyamide for Pb(II) electrochemical probing and dye adsorption

With the continuous development of modern industry, environmental problems accompanied by heavy metal Pb(II) and organic dyes become increasingly apparent, and the development of associated detection/removal materials has important practical significance thus. In this work, a novel biomass (diphenolic acid and furfurylamine)-based, polyamide-sulfonate cross-linked polymer (PA-df-OBSC) was successfully constructed. Further characterization of PA-df-OBSC indicated that the chemical structure of PA-df-OBSC consists of multiple N/O/S-containing molecular fragments as amide, tertiary amine, carboxylic acid, sulfonate ester and sulfonate acid. Such structural characteristic endows PA-df-OBSC dual functional application prospect. PA-df-OBSC can be applied as an enrichment-type Pb(II) electrochemical probe due to its specific complexation for Pb(II). The modified glassy carbon electrode (GCE) with PA-df-OBSC as active modifier presented a wide detection range (0.1–30 μmol/L) and low detection limit (1.31 × 10−8 M) for Pb(II). Besides, PA-df-OBSC also showed selective adsorption for cationic dye methylene blue (MB), with the maximum adsorption capacity up to 521.72 mg/g.