Equilibrium Adsorption Capacity Research Articles

Removal of Metribuzin and Bentazon by LDH-HA Modified Material: Kinetic and Equilibrium Study

ABSTRACT This study investigates the adsorption behavior of herbicides Metribuzin and Bentazon using a soil model incorporating Layered Double Hydroxide (LDH) and humic acid. Mg3AlCl-LDH, synthesized at pH 10, was combined with humic acid to produce two distinct materials: Mg3–5%HA and Mg3–10%HA. These materials were characterized using FTIR, XRD, and SEM techniques. The research confirms that humic acid adsorbs onto the LDH surface without altering its structure, resulting in negatively charged materials. While both materials fully adsorb Metribuzin at 20 mg/L, their adsorption capacities diverge at higher concentrations, with Mg3–10%HA exhibiting a higher capacity than Mg3–5%HA. In contrast, Bentazon’s adsorption is unaffected by humic acid content, displaying identical adsorption capacities in both materials at different concentrations. Both herbicides exhibit rapid adsorption kinetics, reaching equilibrium in 15 minutes. The Avrami model accurately predicts equilibrium adsorption capacities, with Metribuzin primarily adsorbed through electrostatic attraction and hydrogen bonding, while Bentazon’s adsorption is limited due to electrostatic repulsion. The adsorption of both herbicides by Mg3-HA materials is not influenced by pH variations, likely due to the surface charge of the materials. Metribuzin retention in soil containing LDH and humic acid is effective, increasing with higher humic acid concentrations, whereas Bentazon demonstrates greater mobility and resistance. These findings provide valuable insights for developing efficient water decontamination techniques, with implications for environmental protection and public health. Policymakers, researchers, and professionals in water management and pollution control should consider these findings to enhance current practices and technologies.

Supercritical CO2 extrusion foaming of highly open-cell poly(lactic acid) foam with superior oil adsorption performance

Addressing marine oil spills and industrial water pollution necessitates the development of eco-efficient oil-absorbing materials. With increasing concern for the environment, there is a consensus to decrease the use of petroleum-based polymers. Herein, lightweight poly(lactic acid) (PLA) blend foams with varying thermoplastic polyurethane (TPU) content were fabricated via a solvent-free, eco-friendly supercritical carbon dioxide (scCO2) extrusion foaming technology. The incorporation of TPU significantly enhanced the crystallization rate of PLA, with the semi-crystallization time of PT30 and PT50 blends at 105 °C exhibiting a reduction of 77.2 % and 47.9 %, respectively, compared to neat PLA. The resulting foams exhibited an open-cell structure with excellent selective oil adsorption capabilities. Notably, the PT30 foam achieved a remarkable maximum expansion ratio of 36.0, while the PT50 foam attained the highest open-cell content of 96.2 %. The PT50 foam demonstrated an outstanding adsorption capacity, spanning from 4.7 to 18.8 g/g for diverse oils and solvents, with rapid adsorption kinetics, reaching 94.9 % of the equilibrium adsorption capacity for CCl4 within just 1 min. Furthermore, the PT50 foam retained 95.2 % of its adsorption capacity for CCl4 over 10 adsorption-desorption cycles. This study presents a scalable and sustainable approach for large-scale production of high-performance, bio-based foams, facilitating efficient oil-water separation.

Adsorption behavior and solidification mechanism of Pb(II) on synthetic C-A-S-H gels with different Ca/Si and Al/Si ratios in high alkaline conditions

Calcium silicate aluminate hydrate (C-A-S-H) is the main hydration product and its porous adsorption property can effectively inhibit Pb(Ⅱ) leaching from alkaline pore solution of alkali-activated municipal solid waste incineration (MSWI) fly ash compacts. The study examines how different ratios of Ca/Si and Al/Si in C-(A)-S-H affect Pb(Ⅱ) adsorption behavior and mechanism in high alkaline conditions. The results showed that Al-doped C-A-S-H gels have increased specific surface area and cumulative pore volume, and slightly decreased average pore size. Pb(OH)3- adsorption by C-A-S-H was mainly chemisorption with spontaneity. Temperature, pH value, Al/Si and Ca/Si ratios of C-A-S-H affected Pb(Ⅱ) adsorption. Equilibrium adsorption capacity (Qe) initially increased then decreased with higher Al/Si for C-A-S-H with Ca/Si 0.60 but decreased with higher Al/Si for Ca/Si 1.20. Active Si-OH (Q1 or Q2b) and Al-OH (Q2(1Al)) in aluminosilicate tetrahedra chains dehydrate and condense with Pb(OH)3- to form Si-O-Pb or Al-O-Pb bonds. Higher interlayer water content in low Ca/Si and Al/Si C-A-S-H facilitated ion exchange during Pb(Ⅱ) adsorption. After adsorption, aluminosilicate tetrahedra chain length increased while interlayer water content decreased. Ca(Ⅱ) and Pb(Ⅱ) in C-A-S-H underwent partial ion exchange during the adsorption process. Simulation results indicate Pb(OH)3- was more likely to polycondensate with silica tetrahedral bridging oxygen in Si2AlO2(OH)8 to form Si-O-Pb than Al-O-Pb bonds. These findings provide theoretical support for designing dosages of alkali activators and doped aluminosilicate minerals to improve the solidification efficiency of Pb(Ⅱ) in alkali-activated MSWI fly ash compacts.

Semi-wet synthesis of high-performance Li1.6Mn1.6O4 for selective lithium extraction from Salt Lakes Brine

Among the manganese-based lithium-ion sieves, Li1.6Mn1.6O4 has a high theoretical lithium adsorption capacity as a spinel ion sieve material. Small particle size orthogonal phase purity LiMnO2 powders were prepared by a semi-wet method and calcined in air at 400 °C to obtain Li1.6Mn1.6O4 a lithium-ion sieve precursor. The synergistic effects of oxygen atmosphere, heat treatment conditions and lithium/manganese molar ratio on the crystal structure of LiMnO2 and the lithium adsorption/desorption characteristics of Li1.6Mn1.6O4 were comprehensively investigated with XRD, SEM, TEM, XPS, Raman, DTA-TG and capacity retention study. Notably, when the initial lithium/manganese molar ratio was set at 1.1, and the sample underwent a calcination at 120 °C for 48 h under carefully controlled deoxygenation conditions, we observed the exclusive presence of the desired orthorhombic phase in the LiMnO2 sample. In contrast, when the synthesis conditions deviated from the optimized parameters led to the presence of the monoclinic phase of Li2MnO3. This highlights the sensitivity of Li1.6Mn1.6O4 properties to the synthesis conditions. The results of adsorption-desorption cycles show that the ion sieve Li1.6Mn1.6O4 prepared by heat treatment of ordered o-LiMnO2 is more stable, the structural stability of Li1.6Mn1.6O4 were characterized by high-temperature in-situ XRD experiments during heating from 30 to 800 °C. The equilibrium adsorption capacity was 34 mg g−1 in Qarhan Salt Lake brine at 10th cycle, and a remarkably low Mn dissolution loss rate of 0.6 %. The results have significant potential to advance the development of high-performance adsorbent in the Li-Mn-O system and contribute to the advances in lithium separation technology.

Covalent organic framework@cellulose nanofibrils@carboxymethyl cellulose composite hydrogel beads for the removal of nickel ions from aqueous solutions

A novel adsorbent, covalent organic framework (COF)@cellulose nanofibrils (CNF) @carboxymethyl cellulose (CMC) composite hydrogel bead (C-CCHB), was prepared for Ni2+ removal from aqueous solutions. The imine COF provides the main active sites for adsorption. CNF is used as the carrier for grafting COF to improve the dispersion of COF and the reinforcing material. CMC is used as the hydrogel matrix to facilitate easy recycling. The equilibrium adsorption capacity (qe) of the C-CCHB is vastly influenced by the mass ratio of COF@CNF/CMC. The optimized mass ratio of COF@CNF/CMC is 0.050/1 (g/g). The maximum adsorption is reached at pH=6. The qe of Ni2+ increases with a rise in initial concentration of the solution. Based on Langmuir isotherms, the maximum adsorption capacity of C-CCHB is 289.50 mg/g. The adsorption of Ni2+ complies with the pseudo-second-order kinetic model. The C-CCHBs still maintain preferable adsorption properties after the seventh cycle of adsorption–desorption. The Ni2+ adsorption of the C-CCHB is mainly attributed to the chelating effect and electrostatic interaction.

Management of ibuprofen in wastewater using electrospun nanofibers developed from PET and PS wastes

Electrospinning is a promising technique for the beneficial use and recycling of plastic waste polymers using simple methodologies. In this study, plastic bottles and Styrofoam wastes have been used to develop polyethylene terephthalate (PET) and polystyrene (PS) nanofibers using electrospinning technique separately without any further purification. The effect of the concentration onto the nanofiber's morphology was studied. The fabricated nanofibers were characterized using Field Emission Scanning Electron Microscope (FE-SEM), Fourier Transformed Infrared Spectroscopy (ATR-FTIR), N2 adsorption/desorption analysis, and water contact angle (WCA). Furthermore, the prepared nanofibers were applied for the adsorption of ibuprofen (IBU) from wastewater. Some parameters that can influence the adsorption efficiency of nanofibers such as solution pH, wt.% of prepared nanofibers, drug initial concentration, and contact time were studied and optimized. The results show that the equilibrium adsorption capacity was achieved after only 10 min for 12 wt% PET nanofibers which is equivalent to 364.83 mg/g. For 12 wt% PS nanofibers, an equilibrium adsorption capacity of 328.42 mg/g was achieved in 30 min. The experimental data was fitted to five isotherm and four kinetics models to understand the complicated interaction between the nanofibers and the drug. Langmuir-Freundlich isotherm model showed the best fit for experimental data for both PET and PS nanofibers. The adsorption process was characterized by predominantly physical reaction rather than chemical adsorption for both materials. The reusability study revealed that the synthesized nanofibers maintain their ability to adsorb/desorb IBU for up to five cycles. The results obtained demonstrated that fabricated nanofibers from plastic wastes could perform promising adsorbents for the management of IBU in wastewater. However, further research is needed for the scaling-up the fabrication which is required for real-world applications.

Hexagonal boron nitride-doped carbon membrane as anode for the enhanced adsorption and electrochemical oxidation of phenol

An activated carbon membrane (ACM) doped with hexagonal boron nitride (h-BN) was fabricated by using activated carbon as the raw material and phenolic resin as the binder. The preparation process involves blending raw materials, ball milling, membrane pressing, and high-temperature carbonization. The conductive ACM was employed as an anode to constitute an electrochemical membrane reactor (EMR) for phenol removal. The effect of h-BN doping rate (0–5wt.%) on the properties of ACM was explored. Results showed that ACM1 (1wt.% h-BN) displayed a small pore size (20nm), high porosity (41.6%), large specific surface area (446.8 m2/g), and strong mechanical strength (15.4MPa) compared to the pristine ACM0. The oxygen precipitation potential of ACM1 (2.11V) was much higher than that of ACM0 (1.53V), thus reducing oxygen generation at the anode in EMR for phenol degradation. The phenol removal rate of phenol obtained from EMR with ACM1 as the anode at 1.5V was up to 95.6%, which was much higher than that for ACM0 (39.3%). Density functional theory (DFT) calculations and experimental results confirmed that h-BN-doping enhanced the adsorption active sites, and adsorption energy, leading to the high performance of EMR for phenol removal. In addition, the equilibrium adsorption capacity of ACM1 (10.2mg/g) was much higher than that of ACM0 (3.7mg/g). The C atoms adjacent to pyridine N in ACM1 were identified as the adsorption and active catalytic sites by X-ray photoelectron spectroscopy (XPS) and DFT calculations. Therefore, this study sheds light on the design and fabrication of conductive carbon membranes for enhanced performance in industrial wastewater treatment.

A novel loofah-like chitosan/alginate composite aerogels prepared for efficient removal of perchlorate: Experimental and DFT study

Perchlorate, an emerging contaminant in drinking water, has attracted global attention. In this study, a novel loofah-like porous chitosan/alginate composite aerogel (CTS/SA-m) was fabricated using ionotropic pregelation and freeze-dried technology to effectively adsorb perchlorate. The performance, isotherms, thermodynamics, and kinetics of perchlorate adsorption by CTS/SA-m were systematically discussed. The results showed that the loofah-like CTS/SA-m with high hydrophilicity exhibited excellent adsorption properties. Over 95 % of the removal rate in 10 min can be achieved, with initial concentration of perchlorate and CTS/SA-m dosage of 10 mg/L and 2 g/L, respectively. And 70.15 mg/g of equilibrium adsorption capacity of perchlorate could be reached at pH 5 and 298 K. pH had little effect on the removal rate of perchlorate, the removal rate surpassed 85 % over a wide pH range of 3.0–11.0. Multilayer adsorption (MLA), intraparticle diffusion (IPD), and adsorption on the active site (AOAS) models were employed to discuss the adsorption mechanism of perchlorate. It was confirmed that double-layer chemisorption played a dominant role. Density functional theory (DFT) analysis of binding energy revealed the effect of functional groups on the ClO4− adsorption strength in the order of –NH3+ > –COOH > –NH2 > –OH. Furthermore, electrostatic potential and the independent gradient model confirmed that electrostatic interactions, hydrogen bonding, and van der Waals forces contributed to the highly efficient adsorption of perchlorate. These findings have a vital promoting effect on perchlorate removal technology in water treatment. Moreover, the loofah-like CTS/SA-m aerogel material, exhibiting outstanding performance, shows great potential in effectively in trapping perchlorate anions from aquatic systems.

Innovative strategy of turning waste into treasure: High-efficiency adsorption of heavy metals pollutants by modified amorphous calcium phosphate prepared with phosphogypsum waste

In the present work, phosphogypsum (PG) waste was used as a calcium source, and integrated with 2-hydroxyphosphonoacetic acid (HPA) doping, modified inorganic-organic amorphous calcium phosphate hybrid composite was prepared, to remove Cd2+ and Co2+in aqueous solution. The study demonstrated that when pH=8, the equilibrium adsorption capacity of hydroxyapatite (HAP) for Cd2+ and Co2+ can reach 275.84 mg/g and 70.63 mg/g, respectively. After modification with HPA, the adsorption capacity of 20HPA-HAP for Cd2+ and Co2+ was higher at 468.92 mg/g and 171.38 mg/g, respectively. Regeneration experiments show that the adsorbent has good recycling performance, and the adsorbent has a good adsorption effect on low-concentration cadmium and cobalt ions in the actual hard gold electroplating wastewater. Meanwhile, the adsorption mechanism of 20HPA-HAP for Cd2+ and Co2+ was vividly visualized through Multiwfn wavefunction program and VMD program. Therefore, the reason why doping HPA greatly improves the adsorption performance of amorphous calcium phosphate on heavy metal ions was revealed from the atomic point of view. The findings suggest a promising approach for the effective utilization of discarded PG and the effective treatment of heavy metal pollution in industrial wastewater, highlighting the dual benefit of waste material repurposing and pollution control, which was an innovative strategy of turning waste into treasure.

Delayed linker addition (DLA) synthesis of dual linker ZIF-8 for separation mono- and di-branched isomers of hexane

The separation of mono- and di-branched C6 alkane isomers is one of the most challenging industrial processes for the production of high-octane gasoline components. In this work, ZIF-8 with dual ligands of imidazole (IM) and 2-methylimidazole (2-MIM), named as DLA-ZIF-8-IM, was synthesized by the method of delayed linker addition, and the microstructure of DLA-ZIF-8-IM was analyzed. Adsorption thermodynamic, kinetic and separation properties of C6 alkane isomers were investigated. The results show that compared with SALE-ZIF-8-IM prepared by the solvent-assisted ligand exchange method, the synthesis method of DLA-ZIF-8-IM is simpler and the BET specific surface area and pore volume (2136 m2·g−1 and 0.72 cm3·g−1) of DLA-ZIF-8-IM are increased by 21 % and 14 %, which is more conducive to adsorption and diffusion of 3-methylpentane (3MP) on DLA-ZIF-8-IM. The equilibrium adsorption capacity of 3MP on DLA-ZIF-8-IM reaches up to 2.89 mmol·g−1, which is 1.1 times than that on SALE-ZIF-8-IM, and the ratio of diffusion time constants between 3MP and 2,3-dimethylbutane (23DMB) on DLA-ZIF-8-IM (5.13) is 2.2 times than that on SALE-ZIF-8-IM. Moreover, at 30℃, the breakthrough adsorption capacity of 3MP on DLA-ZIF-8-IM is 1.46 mmol·g−1, which is 1.6 times more than that of SALE-ZIF-8-IM (0.90 mmol·g−1), while the breakthrough adsorption capacity of 23DMB is basically the same. The separation factor between 3MP and 23DMB on DLA-ZIF-8-IM is 2.96 via the synergy of thermodynamic and kinetic mechanism and the dynamic adsorption capacity of 3MP reaches 1.46 mmol·g−1. DLA-ZIF-8-IM achieves complete separation of C6 alkane mixtures for obtaining single high-purity product. This work provides a novel synthesis strategy for developing C6 alkane (clear) adsorption separation materials by modulating microporous structures of dual-ligand MOFs.

Evaluation of the CH4/CO2 separation by adsorption on coconut shell activated carbon: Impact of the gas moisture on equilibrium selectivity and adsorption capacity

Upgrading biogas to biomethane is of great interest to change the energy matrix by feeding the renewable fuel produced from biomass waste into natural gas grids or directly using it to replace fossil fuels. The study aimed to assess the adsorption equilibrium of CH4, CO2, and H2O on a coconut-shell activated carbon (CAC 8X30) to provide data for further studies on its efficiency in upgrading biogas by Pressure Swing Adsorption (PSA). The adsorbent was characterized, and equilibrium parameters were estimated from monocomponent CH4, CO2, and H2O equilibrium isotherms. Binary and ternary equilibrium isotherms were simulated, and the selectivity and adsorption capacity of the CAC 8X30 were calculated in dry and wet conditions and then compared with zeolite 13X as a reference material. Regarding characterization, Nitrogen and Hydrogen Physisorption results indicated that 94 % of the pore volume is concentrated in the region of micropores. The adsorption affinity with CAC 8X30 estimated from monocomponent isotherms was in the order KH20>KCO2>KCH4. IAST-Langmuir model simulations presented good agreement with experimental binary equilibrium data. Further simulations indicated equilibrium selectivity for CO2 over CH4 (e.g., 4.7 at 1 bar and 298 K for a mixture of CH4/CO2, 60/40 vol%), which increased in the presence of moisture, indicating its suitability for upgrading humid biogas. Simulations for zeolite 13X suggested that the material is unsuitable in the presence of water vapor but presents higher selectivity than the CAC 8X30 in dry conditions. Hence, the integration of both materials might be helpful for biogas upgrading.

PH-responsive and mechanical strong chitosan-based hydrogel reinforced with rice straw cellulose micro-fibrils for efficient removal of cu(II)

Straw and chitosan are underutilized raw materials, which could make a significant contribution to sustainable development. Herein, a novel chitosan-based hydrogel incorporating rice straw cellulose micro-fibrils (SCMF) was prepared to effectively remove Cu(II). FTIR and SEM showed that straw cellulose-g-poly (acrylic acid)/chitosan-g-poly (acrylic acid) interpenetrating polymer networks were prepared and the hydrogel SCCH had a 3D porous structure after cross-linking with AA. The swelling properties of SCCH were studied and compared in various pH solution. The results indicated that SCCH replayed pH responsibility, which had the largest and smallest swelling capacity at pH9.18 and pH4.00 respectively. The pseudo-second-order kinetic model can be effectively used to evaluate swelling kinetics of hydrogels. The effects of contact time and initial concentration on Cu(II) ion removal were investigated. The equilibrium adsorption capacity (Qe) was 209.2 mg/g and the obtained results indicated that the adsorption kinetics conformed to the pseudo-second-order. Chemical adsorption combined with porous physical adsorption endowed SCCH excellent swelling and adsorption properties. Tensile, compression, bending and twisting test convinced that SCMF played a significant role on the improvement of mechanical strength. This novel 3D porous chitosan-based hydrogel was identified to be a promising sorbent with advantages of excellent sorption and mechanical properties.

Mechanistic study of highly effective phosphate removal from aqueous solutions over a new lanthanum carbonate fabricated carbon nanotube film

The effective purification of phosphate-containing wastewater is considered as increasingly important. In this study, a highly effective LC-CNT film was developed for efficient phosphate removal. Kinetic results showed that the adsorbent exhibited an improved mass transfer efficiency and a fast adsorption rate during adsorption (reaching 80% and 100% equilibrium adsorption capacity within 175 and 270 min, respectively). Kinetic model analysis suggested that the adsorption was a combined chemical physical process. Isotherm study revealed that the LC-CNT film showed a superior adsorption capacity (178.6 mg/g, estimated from the Langmuir model) with multiple adsorption mechanisms. pH study suggested that surface complexation and ligand exchange played important roles during adsorption, and the adsorbent worked well within the pH range of 3–7 with little La leakage. The ionic strength and competing anions showed little influence on the adsorbent effectiveness except for the carbonate and sulfate ions. The characterization and mechanism study revealed that the phosphate adsorption of the LC-CNT film was controlled by inner-sphere complexation, outer-sphere complexation and surface precipitation. The LC-CNT film also showed excellent regenerability and stability in cycling runs, further demonstrating its potential in industrial applications.

Efficient and ultrafast adsorption of aromatic amino acids by hyper-crosslinked porous cyclodextrin polymers with high adsorption capacity

The adsorption separation technology is of key significance in the purification of aromatic amino acids (AAAs) and the production of their derivatives. However, defects are always present in existing adsorbents for AAAs with slow adsorption rates, low adsorption capacity, and poor regeneration performance. Therefore, there is an urgent need to develop more efficient adsorbents for AAAs to improve separation and purification efficiency and productivity. In this study, partially benzylated cyclodextrin-based hyper-crosslinked porous polymers (PBCD-B-D) were prepared, among which the one with β-cyclodextrin as monomer (PBβ-CD-B-D) exhibited an extremely rapid adsorption process, a high adsorption capacity for AAAs, and a good selectivity toward AAAs over other amino acids. Specifically, the adsorption of AAAs reached equilibrium within one minute, while the equilibrium adsorption capacities of PBβ-CD-B-D for Trp and Phe were up to 524.58 mg·g−1 (almost the highest till now) and 189.48 mg·g−1, respectively. The pseudo-second-order kinetic model and the Freundlich model were better suited for describing the adsorption process. The comprehensive analysis of experimental results suggested that host–guest cooperation and π-π interactions may be the two dominant factors affecting the adsorption of AAAs on PBβ-CD-B-D. In addition, PBβ-CD-B-D exhibited good reusability, with the adsorption capacity remaining at 83.67 % after 4 adsorption–desorption cycles. Due to its low cost, good reusability, and excellent adsorption performance, PBβ-CD-B-D has great potential for application in the adsorptive removal and recovery of AAAs.

Chromium sorption on synthetic and natural rock minerals with emphasis on speciation behavior and kinetic model using Cr51

Abstract The presence of chromate in the aquatic environment poses toxicity and pollution to the environment. Therefore, the needs to establish methods to get rid of this species is a must. The effect of different natural rock minerals; pyrite, magnetite, pyrrhotite, and wurtzite as constituent parts of the Earth’s crust can play a major role in waste treatment. The properties of those minerals towards the behavior of chromium (sorption) were studied under the effect of changes of pH and contact time to treat the waste solution of toxic chromate. The total chromium species in the reaction system was determined using Cr51 as a simpler, faster and more accurate analytical tools. Concerning the effect of types of minerals, the synthetic ones, the results indicated that pyrrhotite and wurtzite were highly effective for the removal of chromate with almost 100 % sorption capacity as it was pH-independent, despite the presence of a degree of reductive ability of both minerals. While, it was 99 % at pH 8.5 and 28 % at pH 3 for pyrite and magnetite, respectively, which was pH dependent. The equilibrium adsorption capacities for chromium adsorption were 0.34 ± 0.15, 0.028 ± 0.01 and 4.27 ± 1.3 mg/g mineral for natural minerals pyrite, magnetite and synthetic one pyrhotite, respectively. However, it was found 117.7 ± 10.9 mg/g for synthetic mineral wurtzite. These results can be attributed to the redox power of oxide and sulfide minerals; magnetite and, pyrite used. For kinetic studies of chromium (VI) adsorption, non linear model approved that the reaction could be described based on pseudo-second-order kinetics in such simulated environmental heterogeneous systems.

Adsorption of Co2+ and Cr3+ in Industrial Wastewater by Magnesium Silicate Nanomaterials.

In this paper, two flower-like magnesium silicate nanomaterials were prepared. These and another two commercial magnesium silicate materials were characterized using a scanning electron microscope, the N2 adsorption-desorption method, and other methods. The structure-activity relationship between the adsorption performance of these four magnesium silicate materials and their specific surface area, pore size distribution, and pore structure was compared. The results showed that the 3-FMS modified by sodium dodecyl sulfonate (SDS) had the largest specific surface area and pore size, the best adsorption performance, and the largest experimental equilibrium adsorption capacity (qe,exp) for Co2+, reaching 190.01 mg/g, and Cr3+, reaching 208.89 mg/g. The adsorption behavior of the four materials for Co2+ and Cr3+ both fitted the pseudo-second-order kinetic model and Langmuir adsorption model, indicating that chemical monolayer uniform adsorption was the dominant adsorption process. Among them, the theoretical adsorption capacity (qm) of 3-FMS was the highest, reaching 207.62 mg/g for Co2+ and 230.85 mg/g for Cr3+. Through further research, it was found that the four materials mainly removed Co2+ and Cr3+ through electrostatic adsorption, surface metal ions (Mg2+), and acidic groups (-OH and -SO3H) exchanging with ions in solution. The adsorption performance of two self-made flower-like magnesium silicate materials for Co2+ and Cr3+ was superior to that of two commercial magnesium silicates.

Polydopamine Enhanced Interactions of Graphene Nanosheets to Fabricate Graphene/Polydopamine Aerogels with Effectively Clear Organic Pollutants.

Graphene/polydopamine aerogels (GPDXAG, where X represents the weight ratio of DA·HCl to GO) were prepared by the chemical reduction of graphene oxide (GO) using dopamine (DA) and l-ascorbic acid as reducing agents. During the gelation process, DA was polymerized to form polydopamine (PDA). The introduction of PDA in the gelation of aerogels led to a deeper reduction of GO and stronger interactions between graphene nanosheets forced by covalent cross-linking and noncovalent bonding including π-π stacking and hydrogen bonding. The weight ratio of DA·HCl to GO influencing the formation and morphology of GPDXAG was explored. With the increasing content of DA in gelation, the reduction of GO and the cross-linking degree of graphene nanosheets were enhanced, and the resulting GPDXAG had a more regular pore distribution. Additionally, introducing PDA into GPDXAG improved its hydrophobicity because of the adhesion of PDA to a network of aerogels. GPDXAG exhibited a higher removal efficiency for organic pollutants than the controlled graphene aerogels (GAG). Specifically, the adsorption capacity of GPDXAG for organic solvents was superior to that of GAG, and organic solvent was completely separated from the oil/water mixture by GPDXAG. The equilibrium adsorption capacity of GPDXAG for malachite green (MG) was measured to be 768.50 mg/g, which was higher than that for methyl orange (MO). In MG/MO mixed solutions, aerogels had obvious adsorption selectivity for the cationic dye. The adsorption mechanism of aerogels for MG was also discussed by simulating adsorption kinetic models and adsorption isothermal models.

Sodium alginate/graphene oxide (SA/GO) gel balls for Pb(II)-containing mine wastewater treatment: Molecular design and Pb(II) adsorption characteristics

In view of the difficulty in treating Pb(II)-containing mine wastewater and the low adsorption efficiency of adsorbents, a sodium alginate/graphene oxide (SA/GO) gel ball was designed via molecular simulation using graphene oxide (GO) and sodium alginate (SA) as raw materials and Ca2+ as a crosslinking agent. The morphology and structure of the prepared SA/GO gel spheres were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and their Pb(II) adsorption properties were studied. Molecular simulation studies showed that strong hydrogen bonding occurs between SA/GO and Ca2+. At a CaCl2 concentration of 5 wt%, the shear modulus reached 2.4199, indicating that the SA/GO gel balls had good mechanical strength. An SA/GO gel ball was prepared based on the optimal formula. The adsorption exploration experiment showed that when the temperature was 35 °C, the dosage of the gel ball was 0.02 g, and the adsorption time was 24 h, it had good adsorption performance. Isothermal adsorption analysis showed that at 25,35, and 45 °C, the equilibrium adsorption capacities are 418.41 mg/g, 366.30 mg/g, and 400.00 mg/g, respectively and Pb(II) adsorption using the SA/GO gel balls followed the Langmuir isothermal model, and the adsorption kinetics were quasi-second-order. XPS and EDS studies shown that Pb(II) was successfully adsorbed through complexation, ion exchange and hydroxy-carboxyl functional group reaction. The recovery experiment showed that after four adsorption cycles, the adsorption capacity of SA/GO decreased from 202.56 mg/g to 188.65 mg/g, indicating that SA/GO has a certain degree of recyclability.

Recognition and separation of artemisinin by two-dimensional GO/MXene laminar imprinted composite membranes constructed based on self-supporting technology

In order to solve the problem that some of the imprinted sites were embedded inside the membranes due to the blending method, resulting in low utilization of the imprinted sites, a two-dimensional click graphene oxide (GO)/MXene self-supported layered imprinted composite membranes (CGMMs) was devised and prepared for the adsorption and efficient discriminative separation of artemisinin. Firstly, MXene was modified by self-polymerization using dopamine (PDA), and PDA hybrid coating was constructed on the surface of MXene, which was effective in improving the oxidation brittleness and hydrophilicity of MXene. Given the structural and hydrophilic similarities between GO and MXene nanosheets, the produced CGMMs exhibit an outstanding hydrophilicity and a characteristic lamellar shape. Subsequently, spherical imprinted polymers based on MXene were successfully constructed on the surface and interlayer of stacked GO/MXene nanosheets. The performance of CGMMs was explored by isothermal adsorption, kinetic adsorption, selective adsorption tests and selective permeation tests. The equilibrium adsorption capacity of CGMMs reached 36.10 mg g−1 with satisfactory selective separation capacity (αArtemisinin/ Artesunate = 4.10 and αArtemisinin/ Dihydroartemisinin = 3.03) and excellent permeation selectivity (βArtesunate/ Artemisinin = 5.71 and βDihydroartemisinin/ Artemisinin = 4.40), which implied the successful construction of effective artemisinin-imprinted sites on CGMMs. An essential aspect of the excellent adsorption property and selectivity exhibited by the prepared CGMMs is that the cross-section of CGMMs is composed of MXene nanosheets and GO nanosheets superimposed on a laminar structure dotted with imprinted polymers, which extends the molecular transport channels and facilitates the construction of more molecular imprinting sites.

Synthesis of porous carbon/zeolite composites by low-temperature acid-alkaline leaching from coal gasification fine slag for adsorption of dye wastewater

The conversion and utilization of coal gasification slag is considered one of the key issues in the development of the modern coal chemical industry. In this work, porous carbon/Na-P1 zeolite composites were successfully prepared by a simple and easy-to-operate acid-alkali leaching method on the basis of the composition of coal gasification fine slag. The synthesized CZ-10 possessed a honeycomb-like porous carbon structure and a typical flower-cluster zeolite structure, with the specific surface area and pore volume reaching 195.68 m2/g and 0.257 m3/g, respectively. CZ-10 showed excellent adsorption performance, with an equilibrium adsorption capacity of 175.93 mg/g on methylene blue (MB) at 300 K. CZ-10 can effectively adsorb MB in a wide pH range, and the increase in pH was favorable for adsorption. According to the results of adsorption kinetics and isothermal adsorption experiments, the adsorption process was in good agreement with PSO model and Sips model. According to the characterization results and adsorption experiments, it was speculated that the adsorption of CZ-10 on MB was mainly chemisorption, and may be affected by various factors such as ion-exchange, electrostatic attraction, hydrogen bonding, π-π bonding and van der Waals forces.