Composite Adsorbent Research Articles

Biopolymer-metal composites for selective removal and recovery of waterborne orthophosphate

Orthophosphate (Pi) remediation from effluent serves to address global water security by preventing eutrophication. Herein, chitosan (C), alginate (Alg) and three respective metal systems (Fe3+, Al3+, Cu2+) were used to prepare binary (BMC) or ternary (TMC) metal composite adsorbents. Their physicochemical properties were analyzed through XPS, IR and TGA, while the adsorption properties of the composites were characterized via adsorption isotherms and single-point experiments in saline environmental water. Al-composites formed Al–O complexes, while Fe- and Cu-composites formed in the presence of the biopolymer backbone FeO(OH) and Cu2(OH)3NO3, respectively. While Al-composites showed the highest bound water fraction (up to 16%), the Cu-composites (Cu-TMC-N, CuC-BMC-N; where N = nitrate) revealed the lowest water content. Alginate-based binary composites showed slightly higher water content, as compared to ternary and binary chitosan composites. Among the four materials (Al-TMC-N, Fe-TMC-N, Cu-TMC-N and CuC-BMC-N), the Al-TMC showed the highest Pi selectivity over sulfate, along with high Pi removal-% even in a binary mixture (sulfate + orthophosphate) despite the presence of competitive anion species. Upon spiking saline groundwater samples with low Pi (5 mg/L) that contains 2060 or 6030 mg/g sulfate, Al-TMC-N showed the highest Pi selectivity, followed by Fe-TMC-N. This trend in adsorption of Pi among the various composites is understood based on the HSAB principle for the conditions employed in this study. Removal efficiencies of Pi above 60% in Well 1 (ca. 2000 mg/L sulfate) and above 30% in Well 3 (ca. 6030 mg/L sulfate). Herein, environmentally compatible and sustainable composite adsorbents were prepared that reveal selective Pi recovery from (highly) saline groundwater that can mitigate eutrophication in aqueous media.

A hierarchically porous PEDOT embedded cryogel for in-syringe solid phase extraction of parabens in beverages

A hierarchically porous adsorbent was fabricated using polyethylene dioxythiophene (PEDOT) embedded in a polyvinyl alcohol cryogel. This adsorbent was designed for use in the in-syringe solid-phase extraction (IS-SPE) of parabens present in beverage samples. The creation of a hierarchical pore system was achieved through a reaction between a hydrochloric acid solution and calcium carbonate, strategically introduced during the cryogel synthesis within a needle hub. The porous structure of the cryogel allowed for efficient entrapment of adsorption materials, significantly increasing the number of available adsorption sites. Additionally, PEDOT was incorporated to enhance paraben adsorption through hydrophobic and π-π interactions. High-performance liquid chromatography was employed to quantify the extracted parabens. Under optimized conditions, the developed method exhibited detection limits ranging from 0.15 to 0.25 µg L–1 and quantification limits ranging from 0.50 to 1.0 µg L–1. The technique was successfully applied to assess parabens in various beverage samples, consistently obtaining extraction recoveries between 88.4% and 98.4%, and relative standard deviations (RSDs) below 6%. We conclude that the in-syringe extraction approach offers a straightforward and efficient method, while the composite adsorbent demonstrates ease of preparation and robust reproducibility, allowing for twelve extraction–desorption cycles.

Preparation, characterization, and adsorption kinetics of graphene oxide/chitosan/carboxymethyl cellulose composites for the removal of environmentally relevant toxic metals

This study attempted to develop a low-cost and eco-friendly bio-based composite adsorbent that is highly efficient in capturing potential toxic metals. The bio-composite adsorbent was prepared using graphene oxide (GO), carboxymethyl cellulose (CMC) and chitosan (CS); and characterized using FTIR, SEM-EDX and WAXD techniques. Metal-ion concentration in an aqueous solution was measured by ICP-OES. This article reveals that the adsorption of heavy metal ions varied according to the adsorbent quantity, initial metal concentration, pH, and interaction time. The metal ions' adsorption capacity (mg/g) was observed to increase when the interaction time and metal concentration increased. Conversely, metal ions adsorption was decreased with an increase in adsorbent dosages. The effect of pH on metal ions' adsorption was ion-specific. The substantial adsorption by GO/CMC/CS composite for Co2+, CrO42−, Mn2+ and Cd2+, had the respective values of 43.55, 77.70, 57.78, and 91.38 mg/g under acidic conditions. The metal ions experimental data were best fitted with pseudo-second-order (PSO) kinetics, and Freundlich isotherm model (except Co2+). The separation factors (RL) value in the present investigation were found between 0 and 1, meaning that the metal ions adsorption onto GO/CS/CMC composite is favorable. The RL and sorption intensity (1/n) values fitted well to the adsorption isotherm.

Preparation and adsorption properties of magnetic chitosan/sludge biochar composites for removal of Cu2+ ions

The magnetic chitosan/sludge biochar composite adsorbent was prepared using chitosan, Fe3O4, and sludge biochar as raw materials. The composite adsorbent was able to achieve rapid solid–liquid separation under an applied magnetic field. The morphology and microstructure of the composite adsorbent were characterized by FTIR, XRD, SEM, VSM, and BET analysis. The adsorption performance of the composite adsorbent on Cu2+ was investigated through static adsorption experiments, and the effects of adsorbent dosage, initial concentration of Cu2+, initial pH of the solution, and adsorption temperature on the adsorption efficiency of Cu2+ were discussed. The results showed that chitosan and Fe3O4 were successfully loaded on sludge biochar. When the initial concentration of Cu2+ was 30 mg/L, the dosage of the magnetic chitosan/sludge biochar composite material was 0.05 g, the adsorption time was 180 min, pH was 5, and the temperature was room temperature, the maximum removal rate of Cu2+ reached 99.77%, and the maximum adsorption capacity was 55.16 mg/g. The adsorption kinetics and adsorption isotherm data fitted well with the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, indicating that the adsorption process was chemisorption with monolayer coverage.

Composite adsorbents of aminated chitosan @ZIF-8 MOF for simultaneous efficient removal of Cu(II) and Congo Red: Batch experiments and DFT calculations

In this study, we employed a straightforward in-situ synthesis strategy to fabricate multi-site adsorption functional composites known as aminated chitosan@ZIF-8 (AmCs@ZIF-8) for the efficient removal of Cu(II) and Congo red. The AmCs@ZIF-8 adsorbed Cu(II) at pH 5 and Congo red at pH 3 with excellent removal efficiency values of 94 % and 100 % respectively. The maximum adsorption capacity for Cu(II) and Congo red are obtained as 785 mg g−1 and 1156 mg g−1, respectively. Interestingly, AmCs@ZIF-8 composites exhibited an excellent removal efficiency (>80 %) after reusing them for four sequential cycles. Analysis of the adsorption isotherm and kinetic data indicated that chemisorption primarily governed the adsorption of Cu(II) and Congo red by AmCs@ZIF-8. Furthermore, we elucidated the adsorption energy of Cu(II) and Congo red on the AmCs@ZIF-8 composite through density functional theory. Specifically, the adsorption energy values for Cu(II) with AmCs and ZIF-8 were −20.907 and −57.809 kcal·mol−1, and −26.514 and −16.242 kcal·mol−1 for Congo red, respectively. The efficient adsorption mechanism of Cu(II) and Congo red on the AmCs@ZIF-8 composite can be attributed to the synergistic effects of chelation, electrostatic attraction, ion exchange, and hydrogen bonding through the analysis of experimental characterization and theoretical calculation. Therefore, AmCs@ZIF-8 composites elevate the adsorption capacity of Cu(II) and Congo red in a single-component system and exhibit high removal efficiency (>90 %) in the context of the Cu(II)-Congo red binary system.

Designing a dual-functional ultrathin ZIF-L@GO adsorbent for simultaneous removal of phosphate and tetracycline hydrochloride: Adsorption capacity and mechanism

Inorganic phosphate and organic antibiotics, usually co-existing in wastewater, were difficult to simultaneously remove by common mono-functional adsorbents. In this work, by in-situ coating zeolitic imidazolate frameworks (ZIF-L) on graphene oxide (GO), a dual-functional ultrathin ZIF-L@GO-25 adsorbent was successfully prepared for efficient and simultaneous removal of phosphate and representative tetracycline hydrochloride (TC) from wastewater. ZIF-L@GO-25 exhibited maximum adsorption capacity for phosphate and TC respectively reached 116.3 ± 2.1 mg g−1 and 338.6 ± 6.7 mg g−1, benefiting abundant Zn-defect sites and dimethylimidazole rings exposed on its surface. Moreover, thanks to the specific innersphere complexation of Zn-defect/phosphate and π-π interaction between dimethylimidazole rings/TC molecules, > 95% removal efficiencies were achieved when the concentration of five competitive matters (Cl−, NO3−, SO42−, CO32− and humic acid) were 10 times that of phosphate/TC. Even with the binary pollutants co-existing system, only ∼3% removal decreases occurred on both phosphate and TC. Thus, this work proposed a novel preparation method of developing ZIF-based composite adsorbents for the deep treatment of actual phosphate/antibiotics-polluted wastewater.

In-situ growth of zinc sulfide on the surface of alginate-based biomass carbon: A new material for removing methylene blue/basic fuchsin and copper ions

This work aims to prepare a composite adsorbent with a fixed shape to improve the performance of carbon materials and to solve the problem of adsorbent in powder form which is difficult to recycle after use. The BC-ZnS composite system was successfully prepared by hydrothermal method based on the preparation of biomass carbon (BC) using alginate (Alg), while the ZnS component was grown in-situ on the surface of BC. The effects of Alg, Zn source, hydrothermal temperature and time on the synthesis of BC-ZnS were explored, the results indicated that ZnS was successfully grown in-situ on the BC surface, while the BC maintained its original morphology. BC-ZnS showed excellent adsorption capacity for methylene blue (MB), basic fuchsin (BF), and copper ions (Cu2+), reaching 301.50 mg/g for MB and exhibiting good cyclic stability. The adsorption of MB/BF/Cu2+ by BC-ZnS was characterized by the presence of multiple forces, where the BC component mainly depended on the electrostatic force of Alg residue, while the ZnS involves electrostatic forces, ion exchange and Lewis acid/base soft-soft interactions. The adsorption process conforms to pseudo-first-kinetics and is a spontaneous entropy-increasing process. BC-ZnS can be a candidate for reusable wastewater treatment and has excellent potential for application.

Experimental Research on the Preparation of Composite Adsorbent Based on Iron Manganese Mud to Remove Sb(III) from Water

Experimental Research on the Preparation of Composite Adsorbent Based on Iron Manganese Mud to Remove Sb(III) from Water

Easy separation dual-function Cu2O@LDH@Fe3O4 adsorbent for the removal of Cr(VI) under dark conditions: Experimental and mechanistic study

Designing a magnetic adsorbent material that is both reducible and has strong adsorption properties is significant in reducing Cr(VI) ion pollution. Herein, a 3D multifunctional composite adsorbent for Cr(VI) ions was obtained by using Fe3O4 surface-arrayed magnesium iron layered double hydroxides (Mg/Fe-LDH) micro sheets as a substrate with in situ growth of Cu2O nanoparticles (Cu2O NPs) on their surfaces. Under dark conditions, adsorption capacity of the Cu2O@LDH@Fe3O4 for Cr(VI) was up to 218.82 mg·g−1, surpassing that of Cu2O, Mg/Fe-LDH@Fe3O4, and Mg/Fe-LDH by factors of 1.39, 4.41, and 8.32 respectively. Surprisingly, the removal of Cr(VI) was as high as 76.16 % by the Cu2O@LDH@Fe3O4 (Cinitial = 200 mg/L, pH = 3). Kinetic, isotherm, and thermodynamic results reveal that the removal of Cr(VI) by the Cu2O@LDH@Fe3O4 is consistent with the pseudo-second-order kinetic model of spontaneous monomolecular layer chemisorption. Density functional theory (DFT) calculations show that HCrO4- has a lower energy band gap and is more easily reduced by Cu2O. Therefore, the reason for the adsorbent having more removal effect under acidic conditions was revealed. The XPS and FT-IR experimental mechanism analysis results indicated that Cr(VI) is immobilized on the Cu2O@LDH@Fe3O4 surface through electrostatic interactions, followed by reduction to Cr(III) by Cu2O NPs, which is subsequently adsorbed on the surface of the Cu2O@LDH@Fe3O4. This novel adsorbent structure and unique Cr(VI) removal mechanism provide new ideas for the design of future adsorbents.

Arsenic removal from coal-fired flue gas by MnO2 coated magnetic flower-like Fe3O4 composites: Experimental and DFT study

The gaseous arsenic (mainly As2O3) emitted from coal combustion has become another highly toxic volatile pollutant of concern after mercury. Unlike high-temperature arsenic removal technology, injecting adsorbents before dust collectors has more industrial application prospects, where the development of high-performance arsenic removal adsorbents at low temperatures (100–200 °C) is the core. This work developed a magnetic recyclable MnO2 coated magnetic flower-like Fe3O4 (FL-Fe3O4) composites (Fe3MnxOy) adsorbent. It shows the prepared FL-Fe3O4 has both adsorption and catalytic effects on As2O3 removal from the flue gas. The As2O3 removal amount and efficiency of Fe3MnxOy reaches their maximum at 102.96 μg/g and 55.04 % at Mn/Fe molar ratio of 1 (Fe3Mn3Oy) where the comprehensive effect of the adsorption, oxidation, and fixation of As2O3 on Fe3MnxOy gets to optimal. Lattice oxygen plays an important positive role in the arsenic removal process and O2 can continuously supplement it. Priority adsorption of SO2 will consume lattice oxygen and convert it into SO42-, which inhibits the As2O3 removal by Fe3Mn3Oy. Finally, the influence mechanism of MnO2 coating and SO2 on As2O3 removal by Fe3MnxOy was deeply revealed based on density functional theory calculations. The finding has a vital promoting effect on the industrial application of flue gas arsenic removal technology.

Fabrication of a novel chitosan/polyaspartic acid composite: A pH-tunable sorbent for efficient adsorption of heavy metal ions and dyes from water

Heavy metal ions and dyes pollutants have caused significant environmental pollution, posing a threat to human life and ecosystems. Herein, a novel pH-tunable composite adsorbent CS-PA integrated chitosan (CS) with polyaspartic acid (PA) was fabricated. The morphology and structure of CS-PA were characterized. The results indicated that PA was successfully introduced into CS, and the particle size of CS-PA was irregular and porous with a pore diameter of 10–100 μm. Adsorption experiments demonstrated that CS-PA was efficient in removing various charge properties of heavy metal ions and dyes: cationic [Cu(II) and methylene blue (MB)], anionic [Cr(VI) and congo red (CR)] species. Also, the sorption process in the experimental conditions fitted pseudo-second-order kinetic model and Langmuir isotherm. The maximum adsorption capacity of Cu(II), MB, Cr(VI), and CR were 133.33, 172.41, 138.89, and 178.57 mg/g, respectively, based on the Langmuir isotherm study. CS-PA has strong selective sorption ability for MB over Cu(II) under the acidic condition and CR over Cr(VI) at a weakly alkaline solution in their binary systems. Multiple attractions occurred in adsorbing Cu(II), MB, Cr(VI), and CR because of their diverse charge properties and structural characteristics. Finally, regeneration studies further demonstrate that <5 % in sorption efficiency on CS-PA after 5 cycles. Thus, this composite adsorbent is tunable, versatile and potentially applicable to wastewater treatment.

Optimization of the adsorption performance of herbal residues as lanthanide ion-modified carriers for phosphate by fly ash and its application

In order to mitigate the harmful effects of eutrophication in water bodies, the applications of lanthanum-modified materials for phosphate removal from wastewater have attracted much attention. Unlike conventional adsorbents, plant wastes usually have poor adsorption abilities and are difficult to be reused for desorption of phosphate due to their small pore sizes and ununiform loading of modified ions. In this paper, a composite adsorbent (LC-MM) was synthesized by hydrothermal treatment of waste traditional Chinese medical materials (MMs) with load of lanthanum carbonate and co-heating treatment with coal fly ash (CFA), which was applied to remove phosphate from water. The results showed that maximum adsorption capacity of LC-MM was 52 mg g−1, and the LC-MM showed appreciable adsorption capacity of phosphate for agricultural wastewater in the presence of complex interfering ions and for urban surface waters with low phosphate concentrations. Five adsorption-desorption cycles showed good reusability. The mechanism study showed that the La3+ ions were more uniformly distributed on the surface of the absorbents with the introduction of Fe3+, Al3+, Mg2+ and Ca2+ ions in CFA. The ligand exchange between phosphate and carbonate, the internal spherical complexation formed by lanthanum ion and phosphate, and surface chemical precipitation attachment are the main reasons why the adsorption capacity of LC-MM approached or even surpassed that of conventional lanthanum-modified adsorbents. In conclusions, this work proposed an effective method for the modification of plant materials.

Synthesis and application of lanthanum-doped magnetic biochar composite adsorbent for removal of fluoride from water.

Fluoride levels greater than 1.5mg/L in drinking water are a global environmental issue that can seriously harm the health of humans. One of the most effective techniques for defluoridating water is adsorption. The main drawbacks of many adsorbent materials include their poor adsorption capabilities, prolonged contact times, excessively low or high pH levels, and high dosages. The biochar-based magnetic nanocomposite adsorbent was synthesized in the current study and used as an adsorbent for water defluoridation. Through slow pyrolysis, coffee husk waste was converted to biochar. The composite was created by chemically co-precipitating iron and lanthanum oxide nanoparticles onto the surface of biochar. By using X-ray diffraction analysis (XRD), Fourier transform infrared spectrometry (FTIR), Brunauer-Emmett-Teller (BET), and pHPZC values, researchers were able to describe the magnetic biochar nanocomposite material. The Central Composite Design (CCD), which uses four input variables including dosage (2-5g/L), solution pH (4-8), contact time (30-70min), and initial concentration (10-20mg/L), was used to design the experiments. The quadratic model indicated that the ideal conditions for removing 98.994% of the fluoride from water (adsorbent dosage of 5g L-1, pH 5.74, contact period of 60min, and initial concentration of 12.245mg/L) would be attained. The average triplicate value in ideal circumstances produced a removal effectiveness of 98.51%, demonstrating the proposed response surface's capacity for prediction. The findings of this investigation showed that the magnetic biochar nanocomposite that was created is an effective fluoride adsorbent.

Study on anionic dye toxicity reduction from simulated media by MnO2/agro-biomass based-AC composite adsorbent

In order to reduce the consequences of increased by-products generated by demand for plants essential oil extraction factories, it is important transforming such waste disposal into useful materials. Herein, efficient adsorbent from residues of Eucalyptus camaldulensis leaves (ECL-AC) supported αMnO2 was prepared by the redox reaction between Mn2+ and Mn7+ at approximatively neutral pH and ECL-AC to increase their interactions contributing to the enhanced adsorptive capacity for Helianthine from aqueous media. The by-product was simultaneously activated by impregnation in Potassium permanganate solution as oxidizing agent followed by heating in tubular furnace under controlled atmosphere, resulting in α-MnO2-AC adsorbent. Prior to removal tests, the prepared AC- MnO2 sample was characterized for functional groups (IRFT) and pores structure by evaluation the iodine number (IN) and methylene blue index (MBI). Parameters affecting Helianthine uptake such as equilibrium time, adsorbent dose, solution pH and temperature were also studied. Well known adsorption isotherm models namely, Langmuir, Freundlich and Temkin were used for data analysis and better described by Langmuir model with a maximum uptake of 64.71 mg/g at pH 2.08. The surface area estimation indicates that AC-MnO2 better described by Langmuir model. The surface area estimation indicates that MnO2-AC is microporous/mesoporous material. Calculated thermodynamic parameters showed that the adsorption of Helianthine dye onto MnO2-AC is a spontaneous and exothermic process. Results indicate that this doped biomass based-activated carbon can be used successfully as an alternative low-cost adsorbent in the removal of Helianthine from industrial effluents.

Modification of cellulosic adsorbent via iron-based metal phenolic networks coating for efficient removal of chromium ion

Surface modification of durian rind cellulose (DCell) was done by utilizing the strong coordination effect of polyphenol-based metal phenolic networks (MPNs). MPNs from Fe(III)-tannic acid (FTN) and Fe(III)-gallic acid (FGN) were coated on DCell via a self-assembly reaction at pH 8, resulting in adsorbent composites of FTN@DCell and FGN@DCell for removal of Cr(VI). Batch adsorption experiments revealed that FTN coating resulted in an adsorbent composite with higher adsorption capacity than FGN coating, owing to the greater number of additional adsorption sites from phenolic hydroxyl groups of tannic acid. FTN@DCell exhibits an equilibrium adsorption capacity at 30°C of 110.9 mg/g for Cr(VI), significantly higher than FGN@DCell (73.63 mg/g); the adsorption capacity was increased at higher temperature (i.e., 155.8 and 116.8 mg/g at 50°C for FTN@DCell and FGN@DCell, respectively). Effects of pH, adsorbent dose, initial concentration, and coexisting ions on Cr(VI) removal were investigated. The kinetics fractal-based model Brouers-Sotolongo indicates the 1st and 2nd order reaction for Cr(VI) adsorption on FTN@DCell and FGN@DCell, respectively. The isotherm data can be described with a fractal-based model, which implies the heterogeneous nature of the adsorbent surface sites. The Cr(VI) adsorption via surface complexation with phenolic hydroxyl groups was confirmed by evaluating the functional groups shifting. FGN@DCell and FTN@DCell were found to have good reusability, maintaining over 50 % of their adsorption efficiency after four adsorption-desorption cycles. Environmental assessment with Arabidopsis thaliana demonstrated their potential in eliminating the Cr(VI) phytotoxic effect. Thus, this study has shown the efficient and economical conversion of durian waste into environmentally benign adsorbent for heavy metal treatment.

Bio-based nitrogen doped carbon-silica composites from low value sugarcane by-products for the selective adsorption of Au(III) from aqueous systems

This study investigates the development of carbon-silica composite (CSC) adsorbents with tuneable surface properties for gold adsorption from silica and molasses. Nitrogen modification of the CSC adsorbents was achieved through a facile urea impregnation onto the CSC, followed by pyrolysis at 400 °C (400C-5A). Exceptional Au(III) adsorption was demonstrated from acidic solutions, with a maximum adsorption capacity of 416.9 mg g−1. While CSC with no nitrogen modification (400C) only exhibits an adsorption capacity of 337.9 mg g−1. Langmuir isotherm model and pseudo-second order kinetic model were found to best describe the adsorption behaviour for Au(III) sorption on both nitrogen-modified and non-modified CSC. Urea modification led to nitrogen containing graphitic, pyridinic and pyrrolic functionalities, of which pyridinic groups were active sites for metal coordination, leading to enhanced adsorption and high selectivity towards Au and Pd. Au adsorptions of greater than 99.8% were revealed using both modified and unmodified CSC, even at low concentrations of gold (5 or 10 ppm). X-ray Photoelectron spectroscopy (XPS) analysis of 400C-5A following adsorption indicated the presence of both Au(0) and Au(III), demonstrating that adsorption took place through both chelation and an adsorption-reduction mechanism. These effective adsorbents derived from abundantly available, low cost, bio-based chemicals or low value by-products could create new opportunities for Au and/or Pd adsorption from acidic solutions.

Ligand imprinted composite adsorbent for effective Ni(II) ion monitoring and removal from contaminated water

Heavy metal especially nickel (Ni(II)) is the most pernicious kind of pollution since it is both poisonous and difficult to break down in nature and can cause many human disorders and diseases. The monitoring and removal of Ni(II) ions optically is required to enhance the quality of the water and make it appropriate for drinking as well as other uses around the residence. Therefore, the goal of the current work was to synthesize ligand imprinted composite adsorbent (MCA) and utilize it as an adsorbent to monitor and remove Ni(II) ions from the water. Based on the findings gathered, the MCA that was synthesized had a large particle size with a high surface area even after the ligand impregnation. The MCA was enhanced significantly in color with the contact of Ni(II) ion with limit detection at 0.35 µg/L. The maximum level of Ni(II) ions was eliminated (99 %) when the pH was adjusted to 5.50. The Langmuir model was also used to study the adsorption equilibrium data and the maximum adsorption capacity was 167.55 mg/g. Additionally, the method can selectively detect and remove Ni(II) even in the presence of diverse metal ions. Overall, the MCA offers an ideal platform for the on-site monitoring and removal of heavy metal ions, especially in resource-limited areas.

A novel block copolymer containing gadolinium oxide nanoparticles in ultrasound assisted-dispersive solid phase microextraction of total arsenic in human foodstuffs: A multivariate optimization methodology

A new poly(3-hydroxy butyrate)-b-poly(dimethyl amino ethyl methacrylate) amphiphilic block copolymer containing gadolinium oxide nanoparticles (PHB-PDMAEMA-Gd2O3-NPs) were synthesized and used as composite adsorbent for extraction of total arsenic. Characterization of the composite adsorbent material PHB-PDMAEMA-Gd2O3-NP was studied using spectroscopic techniques. Plackett-Burman design and central composite design were employed to screening and optimization of the experimental parameters. This composite adsorbent was utilized in ultrasound assisted-dispersive solid phase microextraction (UA-dSPµE) for the determination of total inorganic arsenic in foodstuffs through hydride generation atomic absorption spectrometry (HG-AAS). It demonstrates a linear relationship across arsenic concentration range of 0.07–1.12 µg/L with a correlation coefficient (0.996). It’s showed an enrichment factor of 128 and a limit of detection 0.02 µg/L for total inorganic arsenic determination. Accuracy of the developed method was confirmed through the analysis of certified reference materials with 96.0–98.5% recovery. It proved to be significantly useful UA-dSPµE method for determining total inorganic arsenic in different foodstuffs.

Preparation of mussel-inspired polydopamine-functionalized TEMPO-oxidized cellulose nanofiber-based composite aerogel as reusable adsorbent for water treatment

Water pollution is an ongoing trouble that is of significant urgency to resolve worldwide. However, traditional materials used in the process of water purification are costly and energy intensive. The preparation of low-cost, green and sustainable aerogels with low density, high porosity and high specific surface area (SSA) is a great challenge. In this paper, a mussel-inspired, low-cost, polydopamine (PDA)-functionalized TEMPO-oxidized cellulose nanofiber (TOCNF) PDA/TOCNF composite aerogel has been rationally designed and fabricated with low-density, high porosity and high SSA. The PDA/TOCNF composite aerogel shows low density (18.2 mg/cm3), high porosity (98.7 %), and large surface areas (41.3 m2/g). The resulting PDA/TOCNF composite aerogel could adsorb a maximum of 314.6 mg/g of methylene blue (MB). The recycle experiment for reusing of adsorbent showed that after five consecutive cycles, the removal ability of MB by the PDA/TOCNF composite aerogel still maintained higher than 90 %. In addition, the PDA/TOCNF composite aerogel also had a high adsorption capacity of heavy metal ions, for example, it adsorbs 446.0 mg/g of Cu2+, 222.0 mg/g of Pb2+, 267.0 mg/g of Cd2+, and 600.0 mg/g of Fe3+, respectively. The possible adsorption mechanisms imply that the PDA/TOCNF composite aerogel adsorbs MB due to the synergistic binding interactions, such as electrostatic attraction, π-π stacking interaction, Vander waals force, and hydrogen bonding. Similarly, the PDA/TOCNF composite aerogel adsorbs metal ions due to the electrostatic attraction and chelation of metal ions with the PDA/TOCNF aerogel. Therefore, PDA/TOCNF composite aerogels may have potential applications in wastewater treatment because of their sustainability and low energy consumption.

Biomass-derived carbon/iron composite (FexOy-BC (RM)) with excellent Cd(II) adsorption from wastewater – Red mud resource utilization

Red mud is an industrial by-product produced in the process of alumina refining. It contains many iron elements, and the traditional resource utilization method is to extract it. This study took an alternative approach by using red mud's iron content as the substrate to synthesize a novel iron-biochar adsorbent for removing heavy metals from wastewater. Walnut shell biochar was reacted with the iron in red mud via an in-situ reduction–oxidation process to produce an iron-carbon composite adsorbent (FexOy-BC). A series of characterization analyses (e.g., SEM, FTIR, XPS, etc.) and batch adsorption experiments were conducted to investigate the properties and Cd(II) removal performance of the adsorbent, respectively. Response surface methodology was further employed to optimize the adsorption conditions, identifying the ideal 6 g/L adsorbent dose, 10 mg/L initial Cd(II) concentration (C0), and pH 6. The optimized quadratic model demonstrated excellent fit, with an average Cd(II) removal efficiency of 92.59 % under optimal conditions. The adsorption mechanism, renewability, and preliminary cost-benefit analysis indicate that FexOy-BC has the potential to be a highly efficient and sustainable adsorbent. In summary, the new method can recover resources from red mud waste and synthesize heavy metal adsorbents, which comprehensively solves two long-standing problems of industrial waste.