Adsorption Capacity Research Articles

Mercury adsorption study and DFT calculations of sulfur-containing biomass composites prepared by inverse vulcanization

This study introduces an innovative and cost-effective biomass adsorbent, the sulfur/cardanol/potato starch composite (SCP), synthesized through inverse vulcanization for the remediation of mercury-contaminated waters. The SCP was characterized using Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS), Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA) and X-ray Diffraction (XRD) to confirm its composition, morphology, and properties. The adsorption capacity of SCP for Hg(II) was 246.88 mg/g with a removal rate of 98.75 %. Adsorption kinetics followed a pseudo-second-order model, indicating chemisorption as the dominant mechanism, while adsorption isotherms were best described by the Langmuir model. Thermodynamic studies confirmed the adsorption process as spontaneous and endothermic. Density Functional Theory (DFT) calculations further elucidate the interaction mechanisms between mercury and the adsorbent, revealing that the thiyl radicals play a crucial role in the adsorption process. The SCP also exhibited a high selectivity for Hg(II) over other co-existing ions and maintains an adsorption capacity over 223.93 mg/g after five regeneration cycles, thus promising practical applications in environmental mercury management.

A Facile Synthesis of RGO-Ag2MoO4 Nanocomposites for Efficient Lead Removal from Aqueous Solution.

Efficiently treating wastewater, particularly the elimination of heavy metal ions from water systems, continues to be one of the most pressing and complex challenges in modern environmental management. In this work, reduced graphene oxide coupled silver molybdate binary nanocomposites (RGO-Ag2MoO4 NCs) have been prepared via hydrothermal method. The crystalline nature and surface properties of the developed RGO-Ag2MoO4 NCs were proved by XRD, FTIR, SEM, and EDS techniques. Adsorption experiments demonstrated that the nanocomposites (NCs) effectively removed Pb(II) ions within 120 min, achieving a maximum removal efficiency ranging from 94.96% to 86.37% for Pb(II) concentrations between 20 and 100 mg/L at pH 6. Kinetic studies showed that the adsorption process followed a pseudo-second order model. Isotherm analysis presented that the Langmuir model provided the greatest fit for the equilibrium data, with a monolayer adsorption capacity of 128.94 mg/g. Thermodynamic analysis revealed that the adsorption process was spontaneous and endothermic. The results of this study highlight RGO-Ag2MoO4 NCs as a highly promising and eco-friendly material for the effective elimination of Pb(II) ions from wastewater. Their strong adsorption capacity, coupled with sustainable properties, makes them an efficient solution for addressing lead contamination, offering significant potential for practical applications in water treatment systems.

Adsorption removal of copper(II) from water by zero valent iron loaded dendritic mesoporous silica

The object of research is synthesized dendritic mesoporous nanoscale silica (DMSN) modified with zero-valent iron (Fe0@DMSN). This material exhibits a high adsorption capacity for heavy metal ions, in particular copper, whose increased content in the aquatic environment poses a threat to living organisms. In this regard, the main physicochemical features of the removal of copper cations from the aqueous medium using the obtained sample were investigated. The morphology of the obtained dendritic silicas was studied by electron microscopy and the presence of a layer of zero-valent iron was confirmed by X-ray diffraction analysis and infrared spectroscopy. The parameters of the porous structure of the synthesized materials were determined. It was found that after modification of mesoporous silica with particles of zero-valent iron, the value of its specific surface area decreased from 504 m2/g to 312 m2/g. This may be due to the formation of a Fe0 layer not only on their surface but also in the channels of the inorganic matrix, which has a unique dendritic structure characteristic of this type of particles. At the same time, the number of active centers increases due to the enrichment of the silica surface with functional modifier groups that show a high affinity for metal cations. The adsorption capacity of Fe0@DMSN towards Cu2+ ions has been studied and it has been shown that the maximum adsorption value is 39.8 mg/g, which is significantly higher than that of the initial synthesized DMSN sample (0.7 mg/g). The experimental data obtained indicate that the obtained sorption material based on dendritic mesoporous silica nanoparticles with a layer of reactive zero-valent iron can be used for the purification of water contaminated with metal ions. In addition, the magnetic properties of such materials, known and proven by various scientists, will make it easy to separate the solid phase in the processes of sorption water purification using magnetic separation.

Biochar derived from straw residue prepared via combined pre-treatment designed for efficient removal of tetracycline hydrochloride and sulfadiazine sodium salt

In this study, straw residue (SR) was prepared from corn straw by a combined pre-treatment method that involved both microbial treatment (Myrothecium verrucaria, Aspergillus niger, and Trichoderma reesei) and treatment with ρ-toluenesulfonic acid. After pre-treatment, the cellulose content of the residues reached 79.3 %, 72.1 %, 83.5 %, and 85.2 %, respectively. The results indicated that Aspergillus niger and Trichoderma reesei effectively destroyed the corn stover structure, improving the efficiency of the subsequent treatment. Following carbonation and activation processes, the SRs were converted into a series of biochars (ACCC, ACMC, ACTC, and ACNC) with large specific surface areas (2343, 2219, 2693, 2672 m2 g−1). The prepared biochars demonstrated excellent performance in adsorption tests performed using tetracycline hydrochloride (TC) and sulfadiazine sodium salt (SDZ) as adsorption models. The maximum adsorption capacities recorded for TC (908, 1117, 1216, and 1189 mg/g) and SDZ (930, 965, 1033, and 1083 mg/g) were higher than most of the other adsorbents. Furthermore, the potential adsorption mechanisms included pore filling, π-π interactions, hydrogen bonding, and electrostatic attraction. Even after 5 test cycles, the biochar retained over 75 % of its adsorption performance, highlighting its strong potential for applications in removing antibiotics from water.

Optimizing solvothermal synthesis of aluminum-loaded pomelo peel for enhanced fluoride adsorption using response surface methodology

Addressing fluoride contamination in water remains a critical challenge, particularly when seeking cost-effective solutions. In this study, we present a novel aluminum-loaded pomelo peel adsorbent (PPA-Al), synthesized via a one-step solvothermal method, with parameters optimized through response surface methodology. The ideal conditions were established at 2.96 g of pomelo peel, 2 g of NaAlO₂, a reaction temperature of 168.62 °C, and a duration of 140.78 minutes. Characterization of PPA-Al revealed an abundance of hydroxyl and carbon functional groups, enhancing its reactivity with coordination unsaturated aluminum sites. Adsorption isotherms conformed to both Langmuir and Freundlich models, achieving a maximum adsorption capacity of 88.81 mg·g⁻¹, outperforming many existing biomass-based adsorbents. Kinetic analysis indicated that fluoride adsorption followed a pseudo-second-order model, with thermodynamic evaluations suggesting that this process is a spontaneous endothermic reaction. Characterization techniques, including Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), confirmed interactions between fluoride ions and -OH and -CH groups, as well as the formation of Al-F bonds. Notably, the use of PPA-Al reduces groundwater treatment costs by approximately 74.33∼83.24 % compared to activated alumina, and it can be reused multiple times without reagent regeneration. These findings highlight PPA-Al as a promising, efficient material for fluoride removal, while also demonstrating innovative applications for agricultural waste.

Preparation and Characterization of Materials for Low- to Intermediate-Temperature CO2 Adsorption

Global carbon dioxide emissions are rising and the use of fossil fuels in several sectors are the leading causes. As global population and economies continue to grow significantly, the most practical method of lowering such emissions is to capture CO2. Although other technologies are more developed, adsorption is very promising and has attracted much attention. To ensure this technology’s success, it is essential to have suitable CO2 adsorbent materials. In this work, several new hydrotalcites (HTs) with different initial concentrations of ion precursors were prepared for the first time by the co-precipitation method—it was possible to verify that the ion concentrations influence the characteristics of the materials. The prepared HTs were characterized by thermogravimetric analysis (TG), X-Ray diffraction (XRD), surface area measurements and temperature-programmed desorption of CO2 (TPD-CO2) to relate their CO2 capture capacity to their physicochemical properties; the CO2 adsorption equilibrium isotherms were determined at 35 and 300 °C for the prepared samples, as well as for some commercial materials: magnesium oxide, calcium oxide, aluminium oxide and Zeolite 13X. After determining which materials present the best CO2 adsorption capacity, these were submitted to adsorption-desorption cycles to study their stability. The main objective of the work was to prepare and study different CO2 adsorbents for processes that are carried out at low and intermediate temperatures. From the experimental results, it was possible to conclude that the Zeolite 13X showed the best capacity at 35 °C, 3.38 mmol·g−1 (@ pCO2 = 1 bar), and a prepared calcined HT (c-HT2) was the best at 300 °C, 0.97 mmol·g−1 (@ pCO2 = 1 bar). Moreover, it seems there is an optimum initial concentration of the ions’ solutions for the tested HTs, which depends on the final application—c-HT1 showed a better capacity at 35 °C and c-HT2 at 300 °C. From the adsorption-desorption cycles—performed at 35 and 300 °C with the best materials using a magnetic suspension microbalance at 1 bar of CO2 partial pressure —, a working cyclic capacity of 2.69 mmol∙g−1 was achieved by the Zeolite at 35 °C; in turn, c-HT2 showed a working cyclic capacity of 0.79 mmol∙g−1 at 300 °C.

Poly (acrylic acid-co-2-hydroxyethyl methacrylate)-grafted gum ghatti hydrogel for capturing heavy metal ions

In this work, a facile route is explored for the synthesis of a novel polymer composite-based hydrogel (PC-hydrogel). The ratio of 2-(Hydroxyethyl) methacrylate (HEMA) and acrylic acid (AA) is optimized first based on Fourier transform infra-red spectroscopy, swelling ratio (SR%) and surface negative charge (PZC). Results indicate that PC-hydrogel composed of copolymer of HEMA: AA in 1:4 ratio is optimized, for grafting on Gum ghatti (Gg) during free-radical graft copolymerization process. Among all other possible combination of HEMA: AA, 1:4 ratio grafted Gg is termed as PC-hydrogel [Poly (AA-co-HEMA)-g-Gg]. PC-hydrogel exhibited negative surface charge over a wide range of pH owing to increase in AA. The swelling (g/g) and water retention ratio (%) of the prepared hydrogel have been found to be 342.6, 385 & 412.6 g/g and 74.83, 65.30 & 57.86 % in grey, tap and distilled water respectively. Furthermore, PC-hydrogel is applied for capturing Cu2+ and Co2+ ions in aqueous phases. Experimental results showed that adsorption process was pH-dependent, and the maximum capturing of Cu2+ and Co2+ was observed at neutral pH 7. Among different adsorption isotherms models like Langmuir, Freundlich, and Temkin models, experimental data fitted closely with the Langmuir adsorption model showing a maximum adsorption capacity of 381.67 and 328.94 mg/g for Cu2+ and Co2+ respectively. The capturing of metal ion followed pseudo-second-order rate model [rate constant k = 1.7 x 10−4 for Cu2+ and 1.5 x 10−4 for Co2+ g/(mg.min)]. The PC-hydrogel property retained its uptake capacity of metal ions up to the three successive adsorption−desorption cycles, and exhibited higher selectivity towards Cu2+ and Co2+ and other (NaCl, MgCl2, CaCl2) coexisting ions.

Magnetic sludge-derived biochar for Cu (II) removal: RSM-based preparation and BP artificial neural network adsorption modeling

Magnetic sludge-derived biochar (MSDB) was synthesized using response surface methodology (RSM) optimization, with sludge as the raw material and sodium pyrophosphate as the modifier. The structure and surface properties of MSDB were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET) analysis. These analyses revealed that MSDB is rich in functional groups and exhibits magnetic properties, facilitating the adsorption of Cu(II) via complexation and easy separation of MSDB through magnetic means. Batch adsorption experiments showed that under conditions of 25 °C and pH 3.0, with an MSDB dosage of 0.75 g L−1, a Cu(II) removal efficiency of 95.67 % was achieved. Thermodynamic studies demonstrated maximum adsorption capacities of 173.69 mg g−1 at 25 °C, 183.26 mg g−1 at 35 °C, and 197.96 mg g−1 at 45 °C. Additionally, the BP neural network model showed a high coefficient of determination (R2 = 0.9396) and a low mean squared error (MSE = 0.0268) in simulating the MSDB-Cu(II) adsorption process, confirming the robustness of the model in both data simulation and predictive accuracy. This method offers a promising approach for kinetic modeling and predicting adsorption behavior in related fields of study.

Adsorption behavior and quantum chemical analysis of surface functionalized polystyrene nano-plastics on gatifloxacin.

In this paper, the adsorption of gatifloxacin (GAT) by three types of polystyrene nano-plastics (PSNPs), including 400 nm polystyrene (PS), amino-modified PS (PS-NH2), and carboxyl-modified PS (PS-COOH) was studied and the adsorption mechanism were assessed. Experimental findings revealed that the equilibrium adsorption capacity of PSNPs to GAT followed the order PS-NH2 > PS-COOH > PS. The adsorption was regulated by both physical and chemical mechanisms, with intra-particle and external diffusion jointly controlling the adsorption rate. The adsorption process was heterogeneous, spontaneous, and entropy-driven. Sodium chloride (NaCl), alginic acid, copper ions (Cu2+), and zinc ions (Zn2+) inhibited adsorption, with Cu2+ and Zn2+ having the strongest effect on PS-NH2. Theoretical computations indicated that π-π and electrostatic interactions dominated PS adsorption of GAT, while PS-COOH and PS-NH2 adsorbed GAT through electrostatic interactions, hydrogen bonds, and van der Waals (vdW) forces. The surface electrostatic potential of PS-COOH and PS-NH2 was considerably higher than that of PS, with the maximum vdW penetration distance of GAT-PS-NH2 being 1.20 Å. This study's findings provide a theoretical foundation for the migration and synergistic removal of antibiotics, micro-plastics (MPs), and nano-plastics (NPs).

Wormhole Mesoporous Silica Framework with Enhanced Thiol Loading for Improved Hg2+ Sequestration.

Thiol-functionalized mesoporous silica and materials potentially dedicated to diverse applications of composite materials, metal colloids, and metal catalysts, etc. Here, we developed a new synthesis route for 3-methacryloxypropyl trimethoxy silane (MPTMS) functionalized mesoporous silica (KIT-6), achieving a 71.5 % enhancement in thiol functionalization on KIT-6 surfaces. Characterization using XRD, TEM, BET, FTIR, Raman, 29Si NMR, XPS, and ICP-OES revealed structural and morphological features. XRD, TEM, and BET confirmed the three-dimensional structural stabilization of mesoporous silica with ~4 nm pore diameter and a surface area of 1451 m2 g-1. FTIR, Raman, and 29Si NMR studies established the mechanism of thiol functionalization, the formation of a new wormhole chain structural framework (WCSF), and stabilization through hydrogen bonding within the mesopores. The 29Si NMR spectra showed characteristic peaks (T3, T2, Q4, Q3) indicating self-condensed functionalized thiols with siloxane networks. XPS analysis validated enhanced thiol functionalization, indicating a structurally homogeneous WCSF suitable for mercury adsorption. ICP-OES measured a mercury adsorption capacity of 3199.6 mg g-1 for KIT-6, with an Hg2+/S ratio of 1.8, corroborated by molecular structure and mechanism analysis. This innovative thiol functionalization approach enhances the efficacy of applications such as extracting Hg2+ from contaminated sources.

Polytriphenylamine Conjugated Microporous Polymers as Versatile Platforms for Tunable Hydrogen Storage.

Hydrogen (H2) as a fuel source presents a promising route toward decarbonization, though challenges in its storage remain significant. This study explores the synthesis and characterization of polytriphenylamine (PTPA)conjugated microporous polymers (CMPs) for H2 storage. Utilizing a combination of Buchwald-Hartwig (BH) coupling, the Bristol-Xi'an Jiaotong (BXJ) approach, and variations in monomer reactive site stoichiometry, a polymer with specific surface areas in excess of 1150 m2g-1 and micropore volume of 0.47cm3g-1 is developed. H2 storage capacities are measured, achieving excess gravimetric uptakes of 1.65 wt.% at 1bar and 2.51wt.% at 50bar and 77 K, with total capacities reaching 4.40 wt.% at 100bar and 77 K. Net adsorption isotherms reveal advantages to H2 storage using PTPA adsorbents over traditional compression up to pressures of 10bar at 77 K. High mass transfer coefficients of 4.95min-1 indicate a strong material affinity for H2. This study highlights the impact of monomer ratio adjustments on the porosity and excess, total, and net H2 adsorption capacities of PTPA-based CMPs, offering insights into the importance of a non-stoichiometric monomer concentration when developing efficient CMP-based H2 storage materials.

Purification of used Cooking Oil using a Combination of Activated Carbon and Bentonite Adsorbents

The repeated use of cooking oil at high temperatures can significantly degrade its quality, as indicated by darkened color, unpleasant odor, elevated peroxide value (PV), and free fatty acid (FFA) levels. This deterioration can contribute to health risks such as obesity, high cholesterol, heart disease, and cancer. This study investigated the effectiveness of combined activated carbon and bentonite adsorbent in reducing peroxide value and free fatty acid levels in used cooking oil. The purification method involved an adsorption process using a combination of activated carbon derived from mangosteen peel waste and bentonite. The carbonization process was carried out at 600°C for 3 hours, followed by chemical activation with H?PO? at varying concentrations of 1M, 3M, and 5M. Bentonite was activated using 5M HCl. The results demonstrated that 5 grams of activated carbon from mangosteen peel, treated with 5M H?PO?, and bentonite activated with 5M HCl, were highly effective in lowering the peroxide value and free fatty acid levels in used cooking oil. Initially, the PV of the untreated used cooking oil was 16 meq O?/kg, reduced to 3.6 meq O?/kg after treatment with the combined adsorbents. Similarly, the FFA content decreased from 2.2% to 0.09%. Both peroxide value and free fatty acid levels met the standards set by SNI 3741:2013. In conclusion, using activated carbon and bentonite is an efficient method for purifying used cooking oil, as their strong adsorption capacity effectively reduces peroxide value and free fatty acid levels.

Fragrance Carrier Based on Zeolite-A Modified Bentonite as a Controlled Release System in Air Freshener Applications

The quality of air fresheners with low cost production can be improved by using a carrier matrix such as synthetic zeolite to increase the long-lasting properties of fragrance product by encapsulation technique. The zeolite A is considerdas a safe core fragrance carrier matrix to be able to release volatile fragrance from their pores when exposed to atmospheric humidity at room temperature. Zeolite A was synthesized from natural kaolin and was formed into tube pellets with bentonite (20 wt.%) as binder to produce zeolite A-bentonite (ZAB) cylindrical pellets composite and used as a fragrance carrier matrix with a rose essential oil (Rose damascena Mill.) as parfume model. The fresh bentonite can also adsorb the rose essential oil with adsorption capacity of 1.745 g/g bentonite (74.5%). Effects of chemical activation on zeolite-A using acid (HCl) of 0.1 M and base (NaOH) of 0.1 M were studied. The ZAB tube pelletes were found to have high adsorption efficiencies of rose essential oil. ZAB4 has the highest efficiency and was used for regeneration test studies that was carried out over 10 cycles using HCl and NaOH, where the adsorption efficiency was 94.5 and 75.4%, respectively. The activated ZAB4 composite using HCl has a long life time until more than 5 weeks and more than 10 regeneration cycles. This fragrance carrier matrix based on ZAB has significant potential for extended carrier fragrance system.

Waste refractory brick material added chitosan/oxidized pullulan complex gel production and removal of heavy metals from waste water

Wastewater is a by-product of numerous industrial processes that have been demonstrated to have adverse effects on human and natural health due to the pollutants it contains. The pollutants in these substances are organic or inorganic molecules and heavy metal ions that significantly harm the environment and human health. A variety of techniques have been devised for the removal of heavy metal ions from wastewater. The adsorption process has attracted significant attention due to its straightforward implementation, cost-effectiveness, and the environmentally friendly production of adsorbent materials using biocompatible substances. In this study, the removal of Cu2+ ions from wastewater was conducted using chitosan pullulan, a biocompatible and biodegradable polymer. In addition to chitosan and pullulan, waste refractory materials from a furnace used in iron and steel production were added to these polymer materials to increase the adsorption capacity. The initial step involved grinding the waste refractory brick material. Subsequently, chitosan was dissolved in acetic acid. After that, the refractory material was suspended in this solution, facilitating the formation of hydrogel beads using a NaOH solution. The obtained hydrogels were coated with pullulan to produce polyelectrolyte gel. Pullulan was oxidized to 6-carboxypullulan by the TEMPO (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) oxidation method and the negatively charged groups in its structure interacted with the positively charged groups in the chitosan structure to produce a complex gel. The chemical structure, morphological analysis, thermal analysis, and water release analysis of the produced waste refractory brick material added chitosan/oxidized pullulan complex gels were examined. The impact of the 6-carboxypullulan coating on the gels’ properties was elucidated. Furthermore, the adsorption of Cu2⁺ was conducted using solutions containing 100, 500, and 1000 ppm Cu2⁺ ions. It has been observed that the material can clean water with over 98% efficiency, even in solutions that exceed the standards set for wastewater. The material’s efficacy in cleaning solutions with concentrations above the standard for wastewater cleaning is evidence of its high performance. Furthermore, the kinetics and isotherm of the adsorption reaction were examined. The kinetics were determined to be consistent with the Pseudo Second Order (chemical reaction controlled) and aligned with the Langmuir and Freundlich Isotherm (mixed adsorption occurred on homogeneous and heterogeneous surfaces).

Biochar Composite with Enhanced Performance Prepared Through Microbial Modification for Water Pollutant Removal.

This study developed mycelial biochar composites, BQH-AN and BQH-MV, with stable physicochemical properties and significantly improved adsorption capabilities through microbial modification. The results showed that the specific surface area and porosity of BQH-AN (3547.47 m2 g-1 and 2.37 cm3 g-1) and BQH-MV (3205.59 m2 g-1 and 2.46 cm3 g-1) were significantly higher than those of biochar BQH (2641.31 m2 g-1 and 1.81 cm3 g-1), which was produced without microbial treatment. In adsorption experiments using rhodamine B (RhB), tetracycline hydrochloride (TC), and Cr (VI), BQH-AN showed maximum adsorption capacities of 1450.79 mg g-1 for RhB, 1608.43 mg g-1 for TC, and 744.15 mg g-1 for Cr(VI). BQH-MV showed similarly strong performance, with 1329.85 mg g-1 for RhB, 1526.46 mg g-1 for TC, and 752.27 mg g-1 for Cr(VI). These values were not only higher than those of BQH but also outperformed most other biochar adsorbents. Additionally, after five reuse cycles, the pollutant removal efficiency of the mycelial biochar composites remained above 69%, demonstrating excellent regenerative ability. This study not only produced biochar with superior adsorption properties but also highlighted microbial modification as an effective way to enhance lignocellulosic biochar performance, paving the way for further biomass development.

In Situ Synthesis of CoMoO4 Microsphere@rGO as a Matrix for High-Performance Li-S Batteries at Room and Low Temperatures.

Lithium-sulfur batteries (Li-S batteries) have attracted wide attention due to their high theoretical energy density and the low cost of sulfur cathode material. However, the poor conductivity of the sulfur cathode, the polysulfide shuttle effect, and the slow redox kinetics severely affect their cycling performance and Coulombic efficiencies, especially under low-temperature conditions, where these effects are more exacerbated. To address these issues, this study designs and synthesizes a microspherical cobalt molybdate@reduced graphene oxide (CoMoO4@rGO) composite material as the cathode material for Li-S batteries. By growing CoMoO4 nanoparticles on the rGO surface, the composite material not only provides a good conductive network but also significantly enhances the adsorption capacity to polysulfides, effectively suppressing the shuttle effect. After 100 cycles at room temperature with a current density of 1 C, the reversible specific capacity of the battery stabilizes at 805 mAh g-1. Notably, at -20 °C, the S/CoMoO4@rGO composite achieves a reversible specific capacity of 840 mAh g-1. This study demonstrates that the CoMoO4@rGO composite has significant advantages in suppressing polysulfide diffusion and expanding the working temperature range of Li-S batteries, showing great potential for applications in next-generation high-performance Li-S batteries.

Adsorption characteristics and mechanism of novel ink melanin composite modified chitosan for Cd(II) in water

In this study, chitosan (CS), carboxymethyl chitosan (CMCS), and chitosan quaternary ammonium salt (HACC) were successfully loaded with ink melanin (ME) as efficient adsorbents for Cd(II) removal. The results of batch adsorption experiments and structural characterization showed that the modified CS loaded with ME improved the adsorption capacity of the composites for Cd(II). The pseudo-second-order kinetic and Langmuir equations were better suited to describe the batch adsorption experiments. The adsorption of Cd(II) was chemisorption with desirable adsorption effect when the concentration of the three composites was 0.5 mg/mL and the pH value was neutral. Among them, HACC-ME demonstrated remarkable Cd(II) adsorption performance (107.18 mg/g) and sustained an 85 % efficiency in Cd(II) removal over five adsorption-desorption cycles. Ion exchange, complexation, electrostatic attraction, and hydrophobic interaction were the primary mechanisms for Cd(II) removal. Overall, HACC-ME could be employed as a low-cost and highly efficient new natural adsorbent material for the removal of Cd(II) ions from wastewater. These findings illuminate pathways for the development of efficient and novel natural adsorbent materials for environmental cleanup purposes.

Biosorption of Pb2+, Cd2+ and Zn2+ from aqueous solutions by Agrobacterium tumefaciens S12 isolated from acid mine drainage

Heavy metal pollution is a global environmental issue, and microorganisms play a crucial role in the bioremediation of heavy metal-contaminated wastewater. The study isolated heavy metal-resistant bacterium and observed their absorption ability toward Pb2+, Cd2+ and Zn2+. We isolated Agrobacterium tumefaciens S12 from acid mine drainage. The various factors influencing its adsorption performance, including pH, biomass dosage, initial metal ion concentration, and adsorption temperature, were investigated in detail. Chemisorption controls the adsorption rate due to the results better fitted by pseudo-second order kinetics. The maximum adsorption capacities of Pb2+, Cd2+ and Zn2+ on A. tumefaciens S12 were 234, 58 and 51 mg g−1 at 30 °C from Langmuir isotherm, respectively. The adsorption processes for the three heavy metal ions were spontaneous and exothermic in nature. In bimetallic systems, biosorption of Pb2+ ions was preferential to that of Cd2+ and Zn2+. Furthermore, scanning electron microscopy coupled to energy dispersive spectroscopy, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy analysis demonstrated that the adsorption mechanisms include ion-exchange, complexation interaction between the heavy metal ions and the functional groups on the surface of biomass. The obtained results indicated that A. tumefaciens S12 can be applied as an efficient biosorbent in bioremediation technology to sequestrate heavy metal ions from aqueous solution.

Green solvents assisted de-novo synthesis and defect-engineered UiO-66 for improved CO2 adsorption and kinetics- experimental and DFT approach

The CO2 concentration in the atmosphere is increasing at an alarming rate, which is causing distress to human society and the natural environment. Adsorption is one of the most widely used methods of removing CO2 from flue gases, which reduces its adverse effects on our environment. For adsorption purposes, a facile green solvent-assisted de-novo synthesis approach was developed to construct a UiO-66′s structure to target CO2 at low pressure due to the partial pressure of CO2 in flue gases in the atmosphere (0.01⁓0.02 MPa). In the de-novo synthesis approach, a combination of various types of modulators and deep eutectic solvents (DES) are utilized to graft structural defects and induce quantitative and dispersive deep eutectic solvents onto the UiO-66 structure, respectively. The green solvent-assisted de-novo synthesis approach helped to tune all three structural parameters and preserve extra open metal sites (Lewis acid and Bronsted basis sites) with active NH2 and OH groups for improved CO2 adsorption and kinetics under flue gas conditions (CO2/N2=15/85 %). In comparison to the parent UiO-66, de-novo synthesized ChClPropx5@UiO-66 showed increased CO2 uptake (65.04 mg g-1) by 73 % at 0.15 bar and 25 °C, and the cyclic capacity remained almost similar over 10 consecutive cycles with an almost 94 % retention rate. After 3 times of regeneration at 105 °C under N2 atmosphere, the sample reserved almost similar adsorption capacity and could be recycled without dropping CO2 uptake. The strong and rapid interaction between guest CO2 and de-novo synthesized UiO-66 was confirmed by pseudo-first-order and second-order kinetics with reaction rate constants of 0.00026 and 0.00259, respectively. Furthermore, through periodic Density Functional Theory (DFT) calculations, a variety of linker defects are engineered onto the UiO-66 structure to preserve more open metal sites. For each of the engineering defects, free energies, adsorption energies, and the interaction of CO2 molecules on defect structures with bond length (Ɩ, Å) and bond angle (θ˚) are calculated for the most stable structures of UiO-66.

Preparation of Hierarchical Porous ZIF-67 and Its Application in Zinc Battery Separator

This study successfully prepared a hierarchically porous ZIF-67 (H-ZIF-67) by incorporating the polyvinylpyrrolidone (PVP) at room temperature. Compared to standard control ZIF-67 (C-ZIF-67) with a yield of 81% and a BET specific surface area of 1228 m2·g−1, the H-ZIF-67 not only exhibited improved crystallinity and pore structure but also achieved a yield of up to 93% and a BET specific surface area of 1457 m2·g−1. Due to its hierarchically porous structure, H-ZIF-67 demonstrated excellent adsorption capacity and efficiency for methylene orange (MO). Additionally, the composite separator created by combining H-ZIF-67 with nanocellulose (CNF) exhibited remarkable uniformity and dispersion in zinc batteries. In comparison to a conventional CNF separator, the porous structure and high specific surface area of H-ZIF-67 significantly enhanced its electrolyte wettability and Zn2+ transport rates. Its abundant Lewis acid sites effectively promoted the uniform deposition of Zn2+, thereby suppressing the formation of zinc dendrites and improving the cycling and safety performance of zinc-ion batteries. Experimental results indicate that the ion conductivity of the membrane was 4.31 mS·cm−1, the electrolyte absorption rate was 316%, and it could cycle stable for over 4000 h at a current density of 1 mA·cm−2 with a discharge capacity of 1 mAh·cm−2. This achievement will open up new avenues for the preparation and application of ZIF-67 composite separators in aqueous zinc-ion batteries.