Adsorption Of Metal Ions Research Articles

Nano-Fibrillated Bacterial Cellulose Nanofiber Surface Modification with EDTA for the Effective Removal of Heavy Metal Ions in Aqueous Solutions

Nano-fibrillated bacterial cellulose (NFBC) has very long fibers (>17 μm) with diameters of approximately 20 nm. Hence, they have a very high aspect ratio and surface area. The high specific surface area of NFBC can potentially be utilized as an adsorbent. However, NFBC has no functional groups that can bind metal ions, limiting its potential applications. In this study, the hydroxyl groups on the surface of NFBC were chemically modified with EDTA monoanhydride to convert NFBC into a metal adsorbent. The fiber morphology and crystal structures of the modified NFBC were almost identical to those of the unmodified NFBC, suggesting that the surface hydroxyl groups of NFBC were well-conjugated with the EDTA groups. Surface-modified NFBC preferentially adsorbed transition metals in aqueous solutions, such as Cu(II), Hg(II), Pb(II), and Cd(II), but hardly adsorbed Mg(II) and Cr(VI). The adsorption of heavy metal ions can be explained by the pseudo-second-order kinetics of the chemisorption process and the Langmuir isotherm model. Furthermore, the EDTA-modified NFBC is a renewable and recyclable adsorbent. The results of this study indicate that surface-modified NFBC can be utilized as a biosorbent for heavy metal removal in chemical, food, pharmaceutical, and other industrial fields.

Recovery of Li Through Selective Adsorption on Two Types of Calix[4]arene Derived Adsorbents

ABSTRACT Recovery of Li is one of urgent issues owing to exponential increase of Li demand of Li-ion battery. More efficient and selective reagents for Li recovery have been required. Calixarene as a host oligomer was focused on this purpose, and it was applied to adsorptive reagents. Two types of adsorbents incorporating trialkyl monoacetic acid derivatives of calix[4]arene through either impregnation or crosslinking were synthesized. The impregnated adsorbents were synthesized by impregnation of four trialkyl monoacetic acid derivatives of calix[4]arene into macroporous Ambelite XAD-7. The crosslinked adsorbents were synthesized by crosslinking of three trialkyl monoacetic acid derivatives of debutylated calix[4]arene each other using sym-trioxane under an acidic condition. Their adsorption behaviors and Li+ selectivities over other alkali metal ions were investigated. Incorporation of the ligand into the adsorbents had a negligible effect on the time required to reach equilibrium. The impregnated adsorbents exhibited extremely high Li+ selectivity over other alkali metal ions that reflected those of the incorporated ligand, whereas the crosslinked adsorbents exhibited Cs+ selectivity and mixed effects arising from incomplete dehydration and ion discrimination. The adsorption of alkali metal ions was driven by ion-exchange mechanism. The apparent adsorption equilibrium constants for alkali metal ions on both adsorbents and the separation factors between the metal ions were estimated. It was found that three alkyl branches affected the adsorption efficiency, together with separation efficiency.

Selective lead ion sensing via cotton pad-based Na2EDTA capped AuNPs: A smartphone-assisted colorimetric method.

Herein, Na2EDTA-capped AuNPs specifically designed for selective smartphone-assisted colorimetric detection are synthesized and characterized. Na2EDTA-capped AuNPs was synthesized and characterized by UV-Visible spectroscopy, ATR, Raman, XRD, SEM and EDX. The calculated activation energy of the produced nanoparticles was 0.2eV. Using XRD and SEM, the average crystallite size was found to be approximately 25nm. Only Pb2+ and Cd2+, among the following metal ions: Mg2+, K+, Ca2+, Co2+, Ni2+, Ba2+, Hg+, Bi2+, Pb2+, and Cd2+, caused the AuNa2EDTA solution's hue to shift from reddish in color to blue. Pb2+ and Cd2+ were distinguished using a Na2S solution. Cotton pad with AuNa2EDTA integrated served as the substrate for metal ion adsorption. The GIMP software-supported smartphone was used to implement the color contrast (R) method. In the 10-2000μM range, a straight line represented the relationship between 1/R and Pb2+ ion concentrations, with a limit of detection (LOD) of 0.28μM was revealed. Real water sample collected from Rupsa River, Khulna, Bangladesh was tested by the developed colorimetric method to be 80μM of Pb2+ ion. Combining the prevalence of smartphones and the potential of nanotechnology, a cotton-pad based platform functionalized with AuNa2EDTA may be a ground-breaking method for the detection of Pb2+ ions in various media.

Targeting Synthesis of Diatomic Catalysts by Selective Etching and Sequential Adsorption of Metal Atom.

Diatomic catalysts featuring a tunable structure and synergetic effects hold great promise for various reactions. However, their precise construction with specific configurations and diverse metal combinations is still challenging. Here, a selective etching and metal ion adsorption strategy is proposed to accurately assign a second metal atom (M2) geminal to the single atom site (M1-Nx) for constructing diatomic sites (e.g., Fe-Pd, Fe-Pt, Fe-Ru, Fe-Zn, Co-Fe, Co-Ni, and Co-Cu). In this strategy, hydrogen peroxide selectively etches the positively charged carbon atoms near the M1-Nx moiety (denoted as α-C) and produces vacancy, which could trap the M2 at the subsequent adsorption step. These catalysts show optimized electronic structure and enhanced oxygen reduction activity compared to single-site counterparts, and the representative Fe-Pd-NC and Co-Fe-NC catalysts stand as the most active oxygen reduction reaction catalysts (half-wave potential of 0.92 and 0.91 V, respectively). The selective etching of α-C in single-atom catalysts reported here represents a new post-treatment strategy for the targeting synthesis of diatomic sites.

Spin effects in regulating the adsorption characteristics of metal ions.

Understanding the adsorption behavior of intermediates at interfaces is crucial for various heterogeneous systems, but less attention has been paid to metal species. This study investigates the manipulation of Co3+ spin states in ZnCo2O4 spinel oxides and establishes their impact on metal ion adsorption. Using electrochemical sensing as a metric, we reveal a quasi-linear relationship between the adsorption affinity of metal ions and the high-spin state fraction of Co3+ sites. Increasing the high-spin state of Co3+ shifts its d-band center downward relative to the Fermi level, thereby weakening metal ion adsorption and enhancing sensing performance. These findings demonstrate a spin-state-dependent mechanism for optimizing interactions with various metal species, including Cu2+, Cd2+, and Pb2+. This work provides new insights into the physicochemical determinants of metal ion adsorption, paving the way for advanced sensing technologies and beyond.

Copper and zinc removal from anaerobic digestates via Sporosarcina pasteurii induced precipitation: Effect of volatile fatty acids on process performance.

Microbial induced carbonate precipitation (MICP) shows great potential for metals recovery from secondary sources, which is vital for circular economy. This study explores the feasibility of using Sporosarcina pasteurii for MICP to recover copper (Cu) and zinc (Zn) from acidogenic anaerobic digestates at laboratory scale. Pre-cultured S. pasteurii was inoculated into solutions containing 20gL-1 of urea and varying concentrations of Cu and Zn (0-25mgL-1). The system was maintained at 30°C with continuous agitation for seven days to assess Cu and Zn removal at initial pH values of 5, 6 and 7. The influence of volatile fatty acids (VFAs) on urea hydrolysis and Cu and Zn removal via S. pasteurii-induced MICP was evaluated by adding 3g COD L-1 of acetic and propionic acids to metal solutions. Results showed that S. pasteurii enhanced Cu and Zn removal, with yields varying from 22% to 100% depending on the initial pH. In the presence of VFAs, Cu and Zn removal was significantly reduced (p<0.05), however, only S. pasteurii-incubated samples exhibited Cu and Zn removal, indicating exclusive biological-driven removal. The primary mechanisms of action inferred for Cu and Zn removal in VFAs-spiked samples involved urea hydrolysis, which increased local pH and facilitated metals precipitation, as well as the adsorption of metal ions onto the negatively charged S. pasteurii cell wall. This study demonstrates the potential of S. pasteurii to enhance Cu and Zn removal from VFAs-containing media paving the way for a sustainable metals recovery alternative from waste streams.

Perchlorate supported Cu(II) based 1D polymeric chain containing 1,10-phenanthroline: Synthesis, characterization and adsorption of organic dyes and heavy metal ions

A one-dimensional (1D) copper(II) polymeric chain, [Cu(1,10-phen)(ClO4)(H2O)2]n (1), was synthesized by reacting Cu(ClO4)2·6H2O with 1,10-phenanthroline in the presence of triethylamine in methanol. X-ray crystallography revealed that 1,10-phenanthroline functions as a...

The adsorption behavior and mechanism of Cu(Ⅱ), Fe(Ⅱ) and Co(Ⅱ) on straw biochar and their Fenton-like performance for ciprofloxacin decontamination.

In this study, the adsorption of aqueous Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) on biochars at diverse synthesized temperatures was evaluated. The optimal sample BC-800 achieved superior adsorption performance of Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) at 10-50mgL-1 initial concentration. Due to the larger surface area (349.6m2/g), total pore volume (0.24cm3/g), average pore diameter (6.4nm), higher degree of graphitization (IG/ID=1.00) and stable aromatic carbon structure, BC-800 achieved excellent adsorption of Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) through multilayer chemical adsorption, corresponding to the pseudo-2nd-order and Freundlich model (Qm Cu(Ⅱ)=433.4mgg-1, Qm Fe(Ⅱ)=472.0mgg-1 and Qm Co(Ⅱ)=301.0mgg-1). After then, the adsorbed biochars with Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) were directly used as heterogeneous catalysts in Fenton-like reaction for ciprofloxacin (CIP) degradation. Compared with Co-BC-800/peroxymonosulfate (PMS) system, Co-BC-800/H2O2 system exhibited the 56.6% decontamination of CIP with lower ions leaching (0.53mg/L) within 70min. The 97.9% of CIP was finally removed by Co-BC-800/H2O2 under optimized conditions: initial pH=6.94, catalyst dosage=1.0gL-1, H2O2 concentration=0.44gL-1. Furthermore, Co-BC-800 exhibited superior acid-base adaptability (2.94-10.94) and anti-anion interference ability. The removal of CIP was achieved by the synergistic effect of adsorption and oxidative degradation. This study proposes some insights into the behavior and mechanism of metal ions adsorption on biochar and hazardous waste treatment.

Extraction of heavy metal ions from aqueous solutions by frame sorbents based on benzene-1,3,5-tricarboxylate (MBTC) and benzene-1,4-dicarboxylates (MB DC) of various metals

Pollution of soils and water sources with heavy metals leads to negative consequences for the environment associated with disruption of ecosystem balance, harm to the health of living organisms and humans. To solve this problem, organometallic frame sorbents capable of efficiently extracting heavy metal ions from aqueous solutions have been synthesized. During the conducted research, the regularities of the adsorption of cadmium, lead, copper, cobalt and nickel ions were studied using synthesized frame sorbents based on benzene-1,3,5-tricarboxylates (MBTC) and benzene-1,4-dicarboxylates (MBDC). The identification analysis performed on diffractograms of CoBTC and NiBTC powders showed the presence of structures [Co3(BTC)2·12H2O] and [Ni3(BTC)2·12H2O]. Unlike NiBTC, NiBDC dicarboxylate crystallizes in triclinic syngony (spatial group P1¯, Z = 1) and corresponds to the crystal structure [Ni3(OH)2(BDC)2··4H2O], the sample of the CuBTC compound crystallizes in cubic symmetry with the space group Fm3¯m (Z = 16) and corresponds to the crystal structure [Cu3(BTC)2·3H2O], and the CuBDC compound has a structure belonging to the monoclinic symmetry. The results of the analysis of isotherms of low-temperature nitrogen adsorption using synthesized MOFs made it possible to determine important textural characteristics of sorbents. It was noted that a strong adsorbate-adsorbent interaction is realized for CoBTC in the micropore region. It is shown that the specific surface area of synthesized sorbents, calculated by the Brunnauer-Emmett-Teller (BET) method, varies widely. Thus, for CoBTC and NiBTC compounds, it was 276.0 and 9.0 m2/g, respectively. The noted differences are due to the presence of a large number of micropores in the sorbent CoBTC. In most cases, the kinetic patterns of the adsorption of heavy metal ions can be described by a pseudo-second-order equation. The only example of the process proceeding according to the kinetic equation of the pseudo-first order is the adsorption of copper ions on the NiBDC sorbent. It is noted that cobalt, nickel and copper ions are better absorbed by sorbents containing the corresponding ions of the same name according to the Paneta-Faience rule. The linear relationship found between the sorption capacity and the logarithm of the ratio of the radius of ions to their electronegativity implies that the mechanism of adsorption of metal ions on MOFs is determined by the physicochemical properties of the ions themselves. The developed organometallic frame compounds can be effectively used in technologies for purification of water resources from toxic heavy metal ions.

Research progress in the adsorption of heavy metal ions from wastewater by modified biochar

The rapid development of modern industries is accompanied with the aggravating water heavy metal pollution, which poses a potential threat to the aquatic environment and the health of local populations. As an efficient and economical adsorbent, biochar demonstrates the adsorption capacity for heavy metal ions and its adsorption capacity is significantly enhanced after modification. Therefore, biochar can effectively mitigate environmental pollution. By reviewing the existing studies, we summarize the modification methods of biochar, compare the advantages and disadvantages of physical, biological, and chemical modification methods, analyze the effects of modification on the adsorption capacity of biochar for heavy metal ions, and expound the modification mechanism of biochar. On this basis, this article puts forward the future research directions of the application of biochar in treating coexisting pollutants, aiming to provide a reference for the application of biochar in the purification of heavy metal-containing wastewater.

MOF Derived Cobalt Ferrite Cubic Rod-Like Materials for Highly Efficient Electrochemical Simultaneous Detection of Multiple Heavy Metal Ions.

A series of CoFe2O4 materials derived from metal-organic framework were successfully constructed by the solvent-thermal method. The morphology of a typical sample CoFe2O4-1 was mostly in the form of a cubic rod-like structure with a size distribution of 3.2±0.2 μm, while a small amount of the structure presented hexagonal shape with uniform size dispersion. The XPS characterization results confirmed that the CoFe2O4-1 material contained Co3+ (Co2+/Co3+=0.98), and the redox reaction between Co2+ and Fe3+ produced more Fe2+ (Fe2+/Fe3+=1.63), leading to the production of more OV on the surface of the CoFe2O4-1 material (OV%=0.34), thereby facilitating the efficient adsorption of the efficient adsorption of heavy metal ions (HMIs). CoFe2O4-1/GCE as a typical electrode presented excellent performance for the detection of multiple HMIs. The results should be attributed to the good electrical conductivity and large electrochemically active surface area of CoFe2O4-1/GCE, accelerating the transport of ions and charges in the system. Interestingly, there are interaction mechanisms between the HMIs when performing simultaneous detection, suggesting the detection of target ions can be facilitated by adding additional ions. This study provides new research insights for the development of highly sensitive electrochemical sensors for real-time environmental monitoring.

PDA/PMMA blend membrane utilized for the selective adsorption and separation of heavy metal ions.

The detrimental effects of heavy metal aqueous pollution are attracting people's attention increasingly. Membrane separation technology plays a pivotal role in the treatment of aqueous pollution due to its low energy consumption and excellent separation effect. Inspired by the strong adhesion of heavy metal ions by the dopamine in mussel protein, we have fabricated the 5%, 10%, 20% and 30% proportion of polydopamine (PDA)/Polymethyl methacrylate (PMMA) blend membranes with dopamine structure by solvent-induced phase conversion. I-V current, UV titration and transmission tests examined the membrane's selective adsorption and retention capabilities for Fe3+, Cu2+ and Cr3+. These experiments indicated the different selectivity for Fe3+ of four blend membranes with varying PDA/PMMA fractions. Based on Langmuir's adsorption theory, the 10% blend membranes exhibited the most outstanding selective adsorption for Fe3+ with an LOD of 4.724×10-9 M. Moreover, the ability to retain Fe3+ is still close to 100% after 48 h of transmission. This study manifested that the PDA/PMMA blend membrane is capable of adsorbing trace amounts of Fe3+ from water, thereby contributing to aqueous purification.

Self-Assembled Bolaamphiphile-Based Organic Nanotubes as Efficient Cu(II) Ion Adsorbents.

Self-assembled organic nanotubes (ONTs) have been actively examined for various applications such as chemical separations and catalysis owing to their well-defined tubular nanostructures with distinct chemical environments at the wall and internal/external surfaces. Adsorption of heavy metal ions onto ONTs plays an essential role in many of these applications but has rarely been assessed quantitatively. Herein, we investigated interactions between Cu2+ and single-/quadruple-wall bolaamphiphile-based ONTs having inner carboxyl groups with different inner diameters, COOH-ONT10nm and COOH-ONT20nm. We first examined the effects of Cu2+ on their nanotubular structures using SAXS, STEM, and AFM. COOH-ONT10nm was stable in aqueous Cu2+ solution in contrast to COOH-ONT20nm owing to the presence of polyglycine-II-type hydrogen bonding networks within its wall. Subsequently, we studied the Cu2+ adsorption behavior of COOH-ONT10nm by monitoring the concentration of unbound Cu2+ using linear sweep anodic stripping voltammetry. The Cu2+ adsorption was quick, attributable to efficient Cu2+ partitioning through the open ends of the ONT, followed by fast Cu2+ diffusion in the uniform, relatively large nanochannel. More importantly, the Cu2+ adsorption capacity and affinity of COOH-ONT10nm were measured under different pH conditions using the Langmuir adsorption model. The adsorption capacity was similar at the pH range examined, showing the participation of approximately 25% of the inner carboxyl groups in the adsorption. The adsorption affinity increased with pH, indicating the essential role of the deprotonated carboxyl groups in Cu2+ adsorption. Most interestingly, the Langmuir adsorption constant was significantly higher than those of previously reported synthetic adsorbents and planar monolayer based on carboxyl binding sites. The high Cu2+ affinity of the ONT was attributable to the highly dense binding sites on the well-defined nanoscale concave structure of the inner channel. These results provide a valuable guideline for designing self-assembled nanomaterials for efficient chemical separations, detection, and catalysis.

Hydrogen Peroxide Modification Enhances the Ability of Metakaolin based Alkali Activated Materials Adsorbent to Remove the Ni2+ Ions

The presence of nickel ions in wastewater is a significant environmental concern due to its toxicity, which can cause severe health problems. Metakaolin is a pozzolanic material that can be activated by alkali to produce a highly porous and reactive material that can be utilised as a heavy metal ion adsorbent. However, the adsorption capacity of metakaolin-based adsorbents is limited by their surface chemistry and porosity. Metakaolin-based alkali-activated materials adsorbent modified with hydrogen peroxide can effectively remove nickel ions from wastewater. The modification process increases the surface area and porosity of the adsorbent, enhancing its adsorption capacity. The modified adsorbent (1.00 wt.% H2O2) showed a higher sorption capacity of 26.57 mg/g and efficiency of 85.22% compared to the non-modified adsorbent (10.55 mg/g) sorption capacity and 45.63% nickel removal efficiency, indicating the potential of hydrogen peroxide-modified adsorbents as an economical and ecologically sustainable solution for environmental applications, particularly for metal immobilization.

Removal of Chromium (VI) from Aqueous Environment Using Modified Parkia Biglobosa (Locust Bean) Shell

The different metal complexing ligands containing synthetic and natural adsorbents have been described in literature for the removal of heavy metal ions from aqueous solutions. However, the removal of Chromium (IV) ion using Parkia biglobosa is yet to be reported in literature. A new method was developed to obtain adsorption capacity using modified Parkia biglobosa shells as a natural Chromium (IV) heavy metal ion adsorbent from aqueous solution at a certain pH. Agricultural waste: Carob husks (a product derived from carob beans) were modified with HNO3 and citric acid, and their effectiveness on the removal of Cr (VI) from aqueous solutions was examined in a batch experiment. The core sizes used are 150 µm and 300 µm. The effects of different parameters such as pH, Cr (VI) concentration, adsorbent loading, and contact time were determined. The optimum pH values for the two dimensions were found to be 3 and 1, respectively. The contact time for maximum adsorption is 30 minutes. The Freundlich isotherm describes the equilibrium between liquid and solid phases. Parkia biglobosa can be said to be a good adsorbent for the removal of Chromium (VI) heavy metal ion from aqueous solutions depending on the pH of the solution.

Remediation of Ni2+ and Sr2+ ions from aqueous solutions by acacia gum/polyacrylic acid hydrogel reinforced with TiO2 nanoparticles

Abstract Globally, the environment and public health are progressively threatened due to water resource contaminants. For this purpose, a unique polyfunctional nanocomposite is created to remediate heavy metals from aqueous media. The basis of it is TiO2 composite nanoparticles (NPs) manufactured via embedding titanium oxide (TiO2) into acacia gum/acrylic acid (AG/AAc). Nanocomposite hydrogels, bearing different functional groups, are constructed employing a gamma irradiation approach that would operate as adsorbents to remove strontium (Sr2+) and nickel (Ni2+) ions from their wastes. The structure of the prepared hydrogel and its nanocomposites were confirmed by FTIR, whereas the morphology was characterized by SEM. XRD and EDX analysis confirms that the TiO2 NPs are successfully encapsulated into the prepared hydrogel. The presence of TiO2 enhances the thermal stability of the prepared hydrogel. Adsorption extent is evaluated comprehensively concerning temperature, contact time, adsorbent dosage, metal ion concentration, and pH. The physical connection between the adsorbent surface and metal ions is strengthened once TiO2 NPs are included in a copolymeric matrix, which enhances adsorption. Pseudo-second-order kinetics accurately depict the adsorption process, and the Freundlich isotherm provides the most relevant explanation of the equilibrium data. There is a demonstration that sorption is a spontaneous, feasible, and endothermic chemisorption process by examining a variety of thermodynamic parameters, including ΔH, ΔG, and ΔS.

Optimization of the chromium (Cr+6) reduction from waterways using chemically and bacterially treated agro-waste.

Heavy metals, a major source of pollution in the environment, pose a substantial threat due to their non-biodegradability and ability to accumulate in living organisms, causing health problems. Recently, researchers have been searching for cost-effective and safe ways to remove heavy metals from polluted waterways using agricultural waste substitutes. The present study focused on the low-cost treatments for the reduction of chromium Cr+6 metal from the effluent, wherein it has been found that chemically and bacterially treated agro-waste had increased heavy metal ion adsorption capabilities. A sequential optimization of the process parameters was attempted using Plackett-Burman design (PBD) and central composite design of response surface methodology (CCD-RSM) for the maximum reduction of the chromium metal from the effluent. A total of eight parameters were screened out using a 12-run PBD experiment. Out of the eight parameters, time, HCl, NaOH, and bacterial treatments were found to be significantly affecting the maximum reduction of Cr+6 from the effluent. To investigate the interactions' effects of the chosen parameters, they were evaluated using CCD-RSM. Maximum 74% Cr+6 reduction was achieved under the optimum treatment to rice husk of HCl 4.52 N, NaOH 3.53 N, bacterial suspension 7.41%, and with an interaction time 14.32 min using 30 run CCD-RSM experiment. A scanning electron microscope was used to confirm the effects of selected variables on the agro-waste for the Cr+6 reductions, as well as a Fourier transform infrared spectrometer.

Effects of particle size and aging on heavy metal adsorption by polypropylene and polystyrene microplastics under varying environmental conditions

Microplastics have become a major environmental issue because of their widespread presence and tendency to adsorb heavy metals, which can have harmful effects on aquatic ecosystems and human health. The present study investigates the adsorption mechanisms of Pb2+ and Cu2+ ions on both pristine and artificially aged microplastics (MPs) made of polystyrene (PS) and polypropylene (PP). Furthermore, the influence of MP size on the adsorption capacity under different environmental conditions was evaluated. According to the characterization of MPs, aging leads to physical damage and an increase in the number of oxygen-containing functional groups on their surface. The experimental results highlight the significantly higher adsorption ability of smaller and aged MPs compared with that of pristine MPs for both the heavy metal ions. The pseudo-second-order equation provided a better fit for the adsorption kinetics study (R2 = 0.95), suggesting that chemisorption governs the rate-limiting phase in the adsorption mechanism on the MP surfaces. The concordance between the adsorption isotherm model and Freundlich model (R2 > 0.95) indicated a predominance of multilayer adsorption. The environmental factors such as pH, humic acid, temperature, and SO42- concentration significantly affected the adsorption of Pb2⁺ and Cu2⁺ onto PP and PS MPs. These variables play a crucial role in determining the nature of the interactions between heavy metal ions and the microplastic particles under diverse environmental conditions. Electrostatic interactions, surface complexation and van der Waals forces were identified as two factors that could either improve or diminish the metal ion adsorption capacity of MPs.

Promoting CO2 Electroreduction Over ion-exchange Resin-derived Ni-N-C Catalyst with Sulfur Doping.

The utilization of renewable energy for electrocatalytic carbon dioxide reduction reaction (CO2RR) represents a pivotal technology in sustainable carbon conversion. Single-atom catalysts (SACs) featuring transition metal-nitrogen-carbon (M-N-C) structures have demonstrated exceptional electrocatalytic efficacy in CO2RR by maximizing atom efficiency. Nevertheless, further investigation is warranted to optimize the catalytic performance of SACs through the selection of suitable carbon sources and supports, as well as the modulation of the microenvironment surrounding individual metal atoms. In this study, a sulfur-doped Ni-N-C catalyst was prepared using a two-step strategy involving metal ion adsorption and thermal decomposition, with porous ion exchange resin serving as the carbon source. Due to the uniform distribution of single atom active centers on the resin-based carbon support and sulfur doping, this catalyst efficiently converts CO2 into CO with a Faradaic efficiency exceeding 90 % within the range of -0.69~-1.29 V (vs. RHE), reaching a maximum value of 97.7 % (-0.79 V vs. RHE). Theoretical calculations indicate that second-shell sulfur doping effectively promotes coupled transfer of protons and electrons, leading to a significant reduction in Gibbs free energy barriers for CO2RR intermediate products.

Plasma-engineered sugarcane bagasse: a novel strategy for efficient mercury removal from aqueous solutions.

Metal ion adsorption using agro-industrial residues has shown promising results in remediating contaminated waters. However, adsorbent effectiveness relies on their properties, often necessitating processing for modification. Considering this, plasma treatment is effective in modifying material surfaces physically and chemically. This study investigated the modification of sugarcane bagasse (SB) using plasma treatment and evaluated its efficacy as a novel adsorbent for mercury removal from aqueous solutions. SB underwent low-temperature plasma treatment with sulfur hexafluoride (SF6) as the working gas, varying treatment times (2, 30, and 60min), and fixed powers (80, 190, and 300 W) at 16Pa pressure. Characterization via SEM/EDS, FTIR, XPS, and pHpzc revealed significant structural changes like increased in porosity and alteration in proportion atomic. Additionally, the successful incorporation of fluorine was confirmed in all treatment conditions, while sulfur was detected in only some samples. Amongst the tested conditions, the SB treated with 300 W for 60min demonstrated the highest mercury removal efficiency, achieving an impressive 83.67% removal rate compared to untreated SB, which yielded only 57.95%. The adsorption mechanism exhibited both physical and chemical behavior, with chemisorption being the dominant process. The Freundlich model provided the best fit to the experimental data, with an R2 value of 0.97. In conclusion, plasma treatment can be a promising alternative for improving the physical and chemical characteristics of SB adsorbents, thereby improving their efficiency in removing mercury from aqueous solutions.