Cd Sorption Research Articles

Cd(II) Sorption by Nanomagnetic Aerogels Modified with Bentonite and Activated Carbon

Cd(II) Sorption by Nanomagnetic Aerogels Modified with Bentonite and Activated Carbon

Effective Removal of Cd from Aqueous Solutions Using P-Loaded Ca-Mn-Impregnated Biochar.

Cadmium (Cd) pollution in wastewater has become an increasingly widespread concern worldwide. Studies on Cd (II) removal using phosphate-adsorbed sorbents are limited. This study aimed to elucidate the behaviors and mechanisms of Cd (II) sorption on phosphate-loaded Ca-Mn-impregnated biochar (Ps-CMBC). The Cd (II) sorption on Ps-CMBC reached equilibrium within 2 h and exhibited a higher sorption efficiency than biochar and CMBC. Additionally, the Langmuir isotherm could better describe the Cd (II) adsorption on the sorbents. P75-CMBC had a maximum Cd (II) sorption capability of 70.13 mg·g-1 when fitted by the Langmuir isotherm model, which was approximately 3.18 and 2.86 times greater than those of biochar and CMBC, respectively. Higher pH (5-7) had minimal effect on Cd (II) sorption capacity. The results of characterization analyses, such as SEM-EDS, FTIR, and XPS, suggested that there was a considerable difference in the sorption mechanisms of Cd (II) among the sorbents. The primary sorption mechanisms for biochar, CMBC, and Ps-CMBC included electrostatic attraction and surface complexation; additionally, for Ps-CMBC, Cd (II)-π interactions and coordination of Cd (II) with P=O were critical mechanisms for Cd (II) removal. The results of this study demonstrate that phosphate-loaded CMBC can be used as an effective treatment for heavy metal pollution in aqueous media.

Primary and digested sludge-derived char as a Cd sorbent: feasibility of local utilisation

Abstract Cadmium (Cd) is a highly toxic metal, occurring in municipal wastewater and stormwater as well as in wastewater from various industries. Char derived from the pyrolysis of municipal sewage sludge has the potential to be a low-cost sorption media for the removal of Cd. However, the balance between possible local char production and demand has not been assessed previously. In this study, the Cd sorption capacities of chars derived from primary (PSC) and secondary sludge (DSC), as well as the feasibility of char production for Cd sorbent purposes, and the pyrolysis energy balance were evaluated. Results showed that the sorption capacity of PSC (9.1 mg/g; 800 °C, 70 min) was superior to that of DSC (6.0 mg/g; 800 °C, 70 min), and increased with a higher pyrolysis temperature. Pyrolysis of primary sludge had a more favourable energy balance compared with the pyrolysis of digested sludge; however, when accounting for loss of biogas production the energy balance of primary sludge pyrolysis was negative. Assessment of the regional demand (Västerås, Sweden) indicated that PSC or DSC may cover the local Cd sorbent demand. However, it was estimated that large char volumes would be required, thus making the use of DSC/PSC less feasible.

Utilized the (maleic) acid anhydride grafted cellulose to sorption of Cu(II), Mn(II), Cd(II), Fe(III) and Pb(II) in water sample

Utilized the (maleic) acid anhydride grafted cellulose to sorption of Cu(II), Mn(II), Cd(II), Fe(III) and Pb(II) in water sample

Nanosorbent based on coprecipitation of ZnO in goethite for competitive sorption of Cd(II)-Pb(II) and Cd(II)-Pb(II)-Ni(II) systems.

Amongst the various water pollutants, heavy metal ions require special attention because of their toxic nature and effects on humans and the environment. Preserving natural resources will have positive impacts on living conditions by reducing diseases and water treatment by nanotechnology is effective in solving this problem owing to the properties of nanomaterials. In this study, a goethite nanoparticle was prepared by hydrothermal method, while ZnO/goethite nanocomposite by co-precipitation was developed. The nanoparticles were characterized using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transform Electron Microscopy (TEM), Thermogravimetric Differential Thermal Analysis (TGA-DTA), Dynamic Light Scattering (DLS), and Breunner-Emmet-Teller (BET) surface area analysis. The adsorption of Cd(II)-Pb(II) and Cd(II)-Pb(II)-Ni(II) ions systems on ZnO/goethite nanocomposite was investigated in a batch mode. The findings of the study showed that nanoparticles ZnO/goethite composite were mixed of spherical and rod-like shapes. The BET results revealed average particle sizes of 41.11nm for nanoparticles for ZnO/goethite while TGA/DTA confirmed the stability of the adsorbents. The optimum adsorption capacities of the nanocomposite for Pb(II), Cd(II), and Ni(II) ions from the Pb-Cd-Ni ternary system were 415.5, 195.3, and 87.13mgg-1, respectively. The adsorption isotherm data fitted well with the Langmuir isotherm model. The study concluded that the nanoparticle adsorbents are efficient for the remediation of toxic pollutants and are, therefore, recommended for wastewater treatment.

Heavy Metal Ions(II) Sorption by a Cellulose-Based Sorbent Containing Sulfogroups.

This article concerns the effect of the chemical modification of short flax fiber on its sorption properties for heavy metal ions. The main purpose of the modification was to achieve the oxidation of flax cellulose with sodium metaperiodate to form dialdehyde cellulose. Additionally, the research shows the subsequent interaction of dialdehyde cellulose with 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid and its transformation into a derivative capable of forming chelate complexes with heavy metal ions. Additionally, this article presents the results of equilibrium and kinetics studies of the sorption of Cu(II), Cd(II), and Fe(II) ions from aqueous solutions by primary and modified cellulose sorbents. SEM spectra indicate changes in the surface structure of the modified sorbents compared to the original one. IR spectra show the appearance of amino- and sulfogroups in short flax fibers in the process of their modification. The research revealed the efficiency of the method and the possibility of its use for the purification of aqueous solutions from heavy metal ions in industrial processes.

Interaction between biochar of different particle sizes and clay minerals in changing biochar physicochemical properties and cadmium sorption capacity

Biochar exhibits substantial potential for interaction with clay minerals upon its introduction into the environment. However, the precise impact of this interaction on the surface properties of biochar and its capacity for metal sorption, particularly in relation to varying biochar particle sizes, remains unclear. Therefore, this study focused on biochar particles derived from pig bone, varying in size, and subjected them to treatment with two common clay minerals (kaolinite and montmorillonite). The objective was to scrutinize their influence on the physicochemical properties of biochar and its binding affinity for Cadmium (Cd). The results revealed that post-interaction with kaolinite and montmorillonite, the Cd sorption capacity of large biochar particles (250–425 μm) saw respective increments of 11.6% and 26.6%, whereas the Cd removal capacity of small biochar particles (25–75 μm) experienced reductions of 8.8% and 18.5%, respectively. Additionally, the surface area of the large biochar particles increased by 19.5% and 32.9%, while that of the small biochar particles decreased by 31.3% and 17.7% after interactions with kaolinite and montmorillonite, respectively. Through the analysis of 2D-FTIR-COS, it was determined that regardless of particle size, COO- on the initial pig bone biochar exhibited the highest sensitivity for Cd adsorption. However, after interaction with kaolinite and montmorillonite, Al–O and Si–O–Al groups were identified as the most responsive for the small biochar particles, while -OH and O–P–O groups exhibited heightened sensitivity for the large biochar particles in adsorbing Cd. The results of this study offer valuable insights into how typical clay minerals can impact the surface properties and metal sorption capacity of biochar of varying particle sizes, which is advantageous for optimizing the production and environmental applications of biochar.

Mercapto-palygorskite efficiently immobilizes cadmium in alkaline soil and reduces its accumulation in wheat plants: A field study

Cadmium (Cd) contamination in wheat fields has become a major environmental issue in many regions of the world. Mercapto-palygorskite (MPAL) is a high-performance amendment that can effectively immobilize Cd in alkaline wheat soil. However, MAPL as an in-situ Cd immobilization strategy for alkaline wheat soil remains to be evaluated on a field-scale and the underlying mechanisms requires further evaluation. Here, MPAL were used as soil amendment to evaluate their immobilization efficiency on Cd-contaminated alkaline soil in the field experiments. The field experiments showed that MPAL application significantly reduced wheat grain Cd concentration from 0.183 mg/kg to 0.056 mg/kg, with Cd concentration in wheat grain treated with MPAL all falling below the limit value of 0.1 mg/kg as defined in China's food safety standard (GB 2762–2022). The maximal immobilization efficiency of MPAL on soil Cd figured out by diethylenetriaminepentaacetic acid (DTPA) extraction was 61.5%. The mechanisms involved in Cd immobilization by MPAL were mainly related to the enhanced sorption of Cd onto Fe oxides, and the removal of amorphous or free Fe oxides from soil had a substantial impact on Cd immobilization efficiency by MPAL. Furthermore, the antagonistic effect between Mn and Cd uptake may also contribute to the reduction of wheat Cd accumulation after MPAL application. The current research can provide theoretical and technical support for the large-scale application of MPAL in Cd-contaminated wheat fields.

Efficient removal of toxic Cd(II) ions from waste streams by a novel modified biodegradable magnetic sorbent

Environmental remediation is challenged by the removal of harmful heavy metal contaminants from industrial waste streams. Because of its low cost and great effectiveness, adsorption is a commonly used separation method, particularly in environmental cleanup. Inexpensive, biodegradable orange peel-chitosan and Fe3O4 magnetic particles (Fe3O4-OP-CS) were combined in a simple process to create an innovative composite. Their structure and morphology were studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analyses. At room temperature, adsorption experiments were conducted, and variables such pH, initial metal ion concentration, and contact time were tuned to maximize Cd(II) removal. The results of harmful Cd(II) sorption using the synthesized composite showed that its adsorption kinetics and sorption isotherm confirm to the pseudo-second-order and Langmuir models, respectively. The thermodynamic analysis showed that Cd(II) adsorption is exothermic and spontaneous. In comparison to previously reported materials, the new composite also displayed a high adsorption capacity (qmax) of 251.88 mg/g. The composite showed three cycles of reuse and might still be able to promise a maximum saturated adsorption capacity of more than 92%, and tolerance to related metal ions (Mn, Fe, Pb, and Cr) present in Cd (II). In addition to Cd(II) sorption for preconcentration and remediation before Cd testing from waste, digested tobacco, and battery samples, the proposed method is also credible for Cd(II) sorption.

Sorption of As, Cd, and Pb by soil amendments: in situ immobilization mechanisms and implementation in contaminated agricultural soils.

The contamination of agricultural soils by toxic heavy metals, such as As, Cd, and Pb, is of great concern for crop safety as well as environmental and public health. Various adsorbents for the in situ immobilization of these metals have been widely studied, but researches on the potential and superiority of metal adsorption in agricultural soil amendments are still lacking. This study was conducted to investigate the nature of their sorption processes on soil amendments including slaked lime (SL), phosphogypsum (PG), bone meal (BM), and biochar (BC) using a series of laboratory batch tests. The Langmuir adsorption isotherm was used to predict sorption parameters. The experimental data fitted reasonably well on the Langmuir model with high correlation coefficients (R2 = 0.64-0.99) suggesting that monolayer sorption/complexation/precipitation was the dominant mechanism. Among the amendments, SL achieved the highest maximum adsorption capacity (qmax) for As and Cd at 714.3 and 2000 mg g-1, respectively, while PG had the highest qmax for Pb at 196.08 mg g-1. The results indicate that there is no direct correlation between sorption stability and maximum adsorption capacity. Among the sorbents, BC had the highest sorption stability for As (0.007 L mg-1), Cd (0.121 L mg-1), and Pb (2.273 L mg-1), respectively, albeit the qmax values for these three metals were not high. This indicates that the As, Cd, and Pb sorbed on biochar tended to be more stable than those retained on other amendments. While a large sorption capacity is important, our results provide important insights into the metal sorption stability/energy of adsorbents that will aid in the development of long-term management efficiency strategies to rehabilitate metal-contaminated arable soils.

Controllable synthesis of 3D superhydrophilic Cd(II) ion-imprinted polymer microspheres based on OV-POSS and bifunctional monomers synergy with superior selectivity for Cd(II) adsorption

Novel 3D porous Cd(II) ion-imprinted polymer (Cd(II)-IIP) microspheres based on octavinyl polyhedral oligomeric silsesquioxane (OV-POSS) were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization technique combined with the synergistic effect of N-hydroxymethylacrylamide (NMA) and 1-vinylimidazole (1-VI) as bifunctional monomers. RAFT polymerization could achieve a controllable synthesis of polymer networks on OV-POSS. The structure, composition and properties of Cd(II)-IIP were systematically investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscope, water contact angle and thermogravimetric analysis. The results showed that the adsorbent, with a water contact angle of 0 ° and superhydrophilicity, has a high potential for application in aqueous phase systems. Different parameters influencing the sorption performance of Cd(II)-IIP, such as OV-POSS ratio, functional monomers ratio, adsorbent dosage, pH and adsorption time were optimized. Under optimal conditions, the maximum adsorption amount of Cd(II)-IIP for Cd(II) was 80.21 mg/g, and the adsorption equilibrium state could be reached within 40 min. The sorption kinetics proved that the sorption was chemisorption and the rate-limiting step was intraparticle diffusion. Thermodynamic studies showed that Cd(II) sorption was a spontaneous endothermic process. Importantly, XPS analysis, density functional theory (DFT) and frontier molecular orbital (FMO) theory calculations showed that the sorption of Cd(II)-IIP was attributed to the coordination of O and N atoms with Cd(II) on NMA and1-VI, respectively. Actual water sample analysis results indicated that Cd(II)-IIP was an adsorbent of great application potential.

Heavy Metal Bioremediation Potential of Autochthonous Lactic Acid Bacteria for Use in Edible Leafy Vegetables

Heavy metals are well-known as destructive environmental pollutants that cause serious health problems. The use of bacterial biological biosorption has been proposed as a practical and environmentally friendly solution for the removal of heavy metals. The current study was conducted in in vitro and in situ conditions. Initially, seven strains of lactic acid bacteria with probiotic properties (Lacticaseibacillus casei, Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, Limosilactobacillus fermentum, Enterococcus faecium, Lactobacillus helveticus, and Lactobacillus acidophilus) were screened for their ability to bind cadmium, lead, and nickel in an aqueous solution. Three of the potent probiotic strains that showed the highest biosorption efficiency at this stage were selected for further analysis. The effect of these bacteria mixed at a ratio of 1 : 1 : 1 on the removal of toxic metals in fresh leaves of edible vegetables including coriander, leek, and parsley was evaluated within 15 and 30 minutes. During in vitro analysis, the sorption percentage of Pb and Cd appeared higher than 99% during 15 minutes of initial contact, while increasing contact time (30 minutes) had no significant effect on the removal of these metals. While during in situ analysis, Ni sorption by the selected lactic acid bacteria (LAB) isolates was significantly enhanced with increasing contact time, such that the highest biosorption rate was recorded in coriander leaves at 30 minutes (91.15%). Overall, E. faecium showed the highest sorption of Pb, Cd, and Ni (79.75 ± 0.11, 75.28 ± 0.05, and 83.99 ± 0.10%), respectively. The combination of three bacterial strains had a synergistic effect on the toxic metal binding capacity compared to the single state of these bacteria, and the biosorption level increased to 99.94 ± 0.02, 99.91 ± 0.01, and 93.75 ± 0.04%, respectively. Scanning electron microscopic (SEM) observations and energy dispersive X-ray (EDX) analysis confirmed that the majority of Pb, Cd, and Ni were bound to the surface of the bacterial cell.

Potassium permanganate modification of hydrochar enhances sorption of Pb(II), Cu(II), and Cd(II)

Hydrochars formed by hydrothermal carbonization of hickory wood, bamboo, and wheat straw at 200 °C were modified by potassium permanganate (KMnO4) for the sorption of Pb(II), Cd(II), and Cu(II). The wheat straw hydrochar (WSHyC) modified with 0.2 M KMnO4 resulted in the most promising adsorbent (WSHyC-0.2KMnO4). Characterization of WSHyC and WSHyC-0.2KMnO4 revealed that the modified hydrochar features large specific surface area, rich of surface oxygenic functional groups (OCFG), and a significant amount of MnOx micro-particles. Batch adsorption experiments indicated that the adsorption rate by WSHyC-0.2KMnO4 was faster than for WSHyC, attaining equilibrium after around 5 h. The optimum adsorption capacity (Langmuir) of Pb(II), Cd(II), and Cu(II) by WSHyC-0.2KMnO4 was 189.24, 29.06 and 32.68 mg/g, respectively, 12 ∼ 17 times greater than by WSHyC. The significantly enhanced heavy metal adsorption can be attributable to the increased OCFG and MnOx microparticles on the surface, thereby promoting ion exchange, electrostatic interactions, and complexation mechanisms.

Competitive sorption and desorption of cadmium, lead, and zinc onto peat, compost, and biochar

Soil and water contamination by potentially toxic metals (PTMs) has exerted adverse environmental impacts, which justifies studies of promising remediation alternatives. This article investigated the competitive sorption of cadmium (Cd), lead (Pb), and zinc (Zn) onto peat, compost, and biochar derived from the organic fraction of municipal solid waste (OFMSW), but its main innovation was the post-sorption assessment. The effects of contact time on competition between contaminants were systematically analyzed by batch experiments and the effectiveness of the sorption process was evaluated in desorption tests (H2O, HCl, NaOH, and NaCl) and sequential extraction. Kinetic data were well-fitted to pseudo-first-order (PFO) and pseudo-second-order (PSO) models and the intra-particle diffusion model revealed the existence of multiple linear regions, indicating the sorption process was controlled by a multi-step mechanism. The sorption capacities followed a biochar > compost > peat order, with biochar retaining more than 99% of Cd, Pb, and Zn in all samples. The general order of desorption percentage was peat > compost > biochar, with a below 0.60% biochar release, suggesting the importance of chemical processes. HCl solution (more acid pH) showed the highest release of previously sorbed contaminants and, therefore, can be employed for the reuse of sorbents (sorption/desorption cycles). The only exception was Pb desorption on biochar, with maximum release in NaOH solution. A negative Pearson correlation with F1 (acid-soluble/exchangeable fraction) for Cd and Zn and a positive one with the other steps were reported. Pb exhibited an opposite behavior, showing the highest sorption performances and the lowest desorption rates for all sorbents, justified by positive correlations with F4 (residual fraction) and negative ones with desorption. The findings suggest the evaluated sorbents, especially compost and biochar, can be effective materials in the simultaneous sorption of Cd, Pb, and Zn in wastewater, as well as an amendment for PTMs immobilization in contaminated soils.

Effects of microplastics and biochar on soil cadmium availability and wheat plant performance

AbstractBiochar is a promising amendment to promote cadmium (Cd) sorption and fixation in agricultural soil, where microplastics are emerging contaminants in soil. Herein, a greenhouse pot experiment was conducted to elucidate the effects on Cd availability in a soil–plant system by biochar and fresh/aged microplastics application. The fresh microplastics led to an obvious increase in soil Cd availability and Cd uptake by wheat plant, while the aged microplastics increased the available Cd in soil but had no effect on Cd uptake by wheat plant, which was likely attributed to the blocking effect of the aged microplastics on Cd transportation from the soil to the wheat plant. Unexpectedly, biochar had increased Cd availability and Cd uptake. The increased soil soluble Cd was because of both decreased soil pH and elevated dissolved organic matter (DOM) content resulted by biochar addition. Also, the unchanged Cd adsorption of the soil was likely responsible for the increased tested soil Cd availability. In addition, the combined effects of a greater decrease in soil pH, an increase in soil DOM content, and a reduction in Cd adsorption after the addition of microplastics to biochar‐amended soil resulted in a significant increase (ranging from 2.63% to 47.73%) in Cd availability compared to soil treated with biochar alone. Moreover, fresh microplastics inhibited wheat growth, and greater inhibition effect was observed for their aged ones. The biochar elevated the wheat biomass; however, the coexistence of microplastics and biochar decreased the wheat plant biomass compared with biochar alone, due to the negative influence of microplastics in plant growth.

Fabrication of novel 3D PEI-functionalized ZIF-8@alginate aerogel composites for efficient elimination of Pb(II) and Cd(II) from aqueous solution

ZIF-8, a metal-organic framework, has large sorption capacities for a series of heavy metals. However, it is difficult to be separated from aqueous solution, limiting its practical application in wastewater treatment. Herein, ZIF-8 was in-situ grown on the polyethyleneimine-functionalized alginate to construct the ZIF-8 @ALG-PEI aerogels with a three-dimensional network structure. This synthesis strategy not only overcomes the above-mentioned defects of ZIF-8, but also provides more functional groups, pores, and channels. The synthesized ZIF-8 @ALG-PEI aerogels exhibit outstanding removal performance towards Pb(II) and Cd(II) with maximum sorption capacity values of 295.986 and 249.838 mg·g−1, respectively. The sorption of Pb(II) and Cd(II) on ZIF-8 @ALG-PEI is strongly affected by pH, but little influenced by ionic strength. In the multi-component sorption systems, ZIF-8 @ALG-PEI shows better sorption affinity and selectivity for Pb(II) than for Cd(II). The three-dimensional network structure constructed by alginate makes Pb(II) and Cd(II) easier to contact with the surfaces of ZIF-8 @ALG-PEI. The strong surface complexation of the O- and N-containing functional groups provided by ZIF-8 and PEI with Pb(II) and Cd(II) makes the largest contribution to the removal of Pb(II) and Cd(II) by ZIF-8 @ALG-PEI. In summary, the experimental findings of this work prove that the synthesized ZIF-8 @ALG-PEI aerogels have promising applications in practical wastewater treatment.

Synthesis of magnetic sodium lignosulfonate hydrogel(Fe3O4@LS) and its adsorption behavior for Cd2+ in wastewater

Heavy metal pollution is becoming increasingly serious. Heavy metal pollutants are nonbiodegradable and can be bioenriched through the food chain, and thus, they greatly threaten the environment and human health. Hydrogels, as an ideal adsorbent, have been widely used to treat heavy metal industrial wastewater. Sodium lignosulfonate hydrogel (LS) was prepared by free-radical grafting copolymerization, and nano-Fe3O4 particles were loaded in LS by an in-situ precipitation method (Fe3O4@LS). The magnetic properties and adsorption capacity of Fe3O4@LS are closely related to the load capacity of Fe3O4. XRD, FTIR, XPS, SEM, TEM, BET, and TGA analyses of the materials were performed. Subsequently, the removal effect of the typical pollutant Cd2+ in heavy metal-polluted water was studied with Fe3O4@LS as the adsorbent. The influences of the Fe3O4@LS dosage and initial pH were investigated, and the adsorption kinetics and thermodynamics were further explored and discussed. Finally, the adsorption mechanism of Fe3O4@LS on Cd2+ was obtained. Results show that Fe3O4@LS has a more stable spatial network structure than LS, and the pore size, specific surface area and active sites increase. The maximum adsorption capacity can reach 88.00 mg/g when pH = 6 and the dosage of Fe3O4@LS is 1000 mg/L. The adsorption of Cd2+ by Fe3O4@LS conforms to pseudosecond-order kinetics and the Temkin isothermal adsorption model. Further mechanistic investigations show that the sorption of Cd2+ on Fe3O4@LS is mainly attributed to surface complexation, electrostatic attraction and coprecipitation. The coexistence of cations in water will inhibit the adsorption of Fe3O4@LS. Fe3O4@LS has superparamagnetism and a good response to an external magnetic field. The adsorption rate can still reach >60 % after four elutions with NaCl as the eluent. This material can be reused and has good application potential.

Cadmium isotope fractionation during sorption to soil minerals: Lab evidence and field implication

Stable isotope is a potent geochemical tracer unveiling the dynamic sources of cadmium (Cd) in the environment. However, the sorption process of aqueous Cd onto solid surfaces (e.g., soil) fractionates isotopic signatures, which makes it difficult to interpret its sources and migration processes. Understanding how Cd fractionates during sorption to soil minerals, therefore, provides necessary data to open the isotope fractionation black box of liquid-solid phase partition of Cd. In this study, we explored isotopic fractionation characteristics during Cd sorption to typical soil minerals. Distinct Cd isotope fractionation was observed during sorption, including goethite (∆114/110Cdsolid−solution=−0.51∼−0.47‰), montmorillonite (−0.34∼−0.32‰), quartz (−0.34∼−0.30‰), gibbsite (−0.29∼−0.25‰), and kaolinite (−0.09∼−0.07‰), where lighter isotopes tended to be preferentially sorbed to the solid phase in a reversible manner. We've also conducted a field survey in a historical flooding-affected region to explore Cd isotopic compositions of soil samples adjacent to a polluted creek. Distinct isotopic signatures for surficial soils and deep soils were observed, which was depicted by a binary mixing mode. Leaching of Cd from mine tailings to the creek, as well as its re-adsorption to soil during historical flooding events both led to preferential enrichment of light isotopes in the solid phase, which was consistent with findings from lab sorption experiments. Mineralogical analyses including EPMA, TOF-SIMS, Mössbauer spectra, XRD, and chemical extraction tests, were applied to unveil how Cd was bound to soil minerals at field. Possible linkage between lab and field data were discussed on the basis of these findings. Results from this study are encouraging for future application of Cd isotopes for source tracing.

Enhanced removal of Pb (II) and Cd (II) ions from aqueous systems using coated magnetic nanoparticles in activated carbon derived from corncob waste

The study investigated the use of a cheap, high-efficiency, and eco-friendly adsorbent as an alternative to activated carbon coated Maghemite nanoparticles (γ-Fe3O4) for removing lead and cadmium ions from aqueous solutions. The Maghemite nanoparticles were synthesized using a sol-gel method. The characteristics of the adsorbent SEM, FT-IR, XRD and pHZPC, were analysed. The adsorption isotherm data were examined, and the data showed good fit with the Langmuir, Temkin and Freundlich isotherm models. The maximum adsorption capacity for Pb (II) and Cd (II) ions, as determined by the Langmuir isotherm, was found to be 127 mg/g and 100 mg/g, respectively. The kinetics of adsorption were studied using four kinetic models: pseudo-first order, pseudo-second order and Elovich model. Among these, the pseudo-second order kinetic model showed a good fit with high correlation values. Thermodynamic parameters such as the change in free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were calculated. These parameters indicated that the sorption of Pb (II) and Cd (II) ions is feasible, spontaneous, and endothermic. Overall, the results demonstrated that Maghemite nanoparticle coated activated carbon derived from agricultural biomass could be an attractive option for removing metals from industrial effluents. This alternative adsorbent offers advantages such as cost-effectiveness, high efficiency, and environmental friendliness in the removal of lead and cadmium ions from aqueous solutions.

Use of Chrysosporium/carbon nanotubes for preconcentration of ultra-trace cadmium levels from various samples after extensive studies on its adsorption properties

Carbon nanotubes were used to immobilize Chrysosporium fungus for building an adequate adsorbent to be used as an desirable sorbent for preconcentration and measurement of cadmium ultra-trace levels in various samples. After characterization, the potential of Chrysosporium/carbon nanotubes for the sorption of Cd(II) ions was scrutinized by the aid of central composite design, and comprehensive studies of sorption equilibrium, kinetics and thermodynamic aspects were accomplished. Then, the composite was utilized for preconcentration of ultra-trace cadmium levels, by a mini-column packed with Chrysosporium/carbon nanotubes, before its determination with ICP-OES. The outcomes vouchsafed that (i) Chrysosporium/carbon nanotube has a high tendency for selective and rapid sorption of cadmium ion, at pH 6.1, and (ii) kinetic, equilibrium, and thermodynamic studies showed a high affinity of the Chrysosporium/carbon nanotubes for cadmium ion. Also, the outcomes displayed that cadmium can quantitatively be sorbed at a flow speed lesser than 7.0 mL/min and a 1.0 M HCl solution (3.0 mL) was sufficient to desorbe the analyte. Eventually, preconcentration and measurement of Cd(II) in different foods and waters were successfully accomplished with good accuracy, high precision (RSDs ≤5.65%), and low limit of detection (0.015 μg/L).