Mechanism Of Cd2 Research Articles

Cadmium and calcium ions' effects on the growth of Pleurotus ostreatus mycelia are related to phosphatidylethanolamine content

Heavy metal Cd2+ can easily be accumulated by fungi, causing significant stress, with the fungal cell membrane being one of the primary targets. However, the understanding of the mechanisms behind this stress remains limited. This study investigated the changes in membrane lipid molecules of Pleurotus ostreatus mycelia under Cd2+ stress and the antagonistic effect of Ca2+ on this stress. Cd2+ in the growth media significantly inhibited mycelial growth, with increasing intensity at higher concentrations. The addition of Ca2+ mitigated this Cd2+-induced growth inhibition. Lipidomic analysis showed that Cd2+ reduced membrane lipid content and altered lipid composition, while Ca2+ counteracted these changes. The effects of both Cd2+ and Ca2+ on lipids are dose dependent and phosphatidylethanolamine appeared most affected. Cd2+ also caused a phosphatidylcholine/phosphatidylethanolamine ratio increase at high concentrations, but Ca2+ helped maintain normal levels. The acyl chain length and unsaturation of lipids remained unaffected, suggesting Cd2+ doesn't alter acyl chain structure of lipids. These findings suggest that Cd2+ may affect the growth of mycelia by inhibiting the synthesis of membrane lipids, particular the synthesis of phosphatidylethanolamine, providing novel insights into the mechanisms of Cd2+ stress in fungi and the role of Ca2+ in mitigating the stress.

Adsorption of Cd2+ by Lactobacillus plantarum Immobilized on Distiller's Grains Biochar: Mechanism and Action.

Immobilized microbial technology has recently emerged as a prominent research focus for the remediation of heavy metal pollution because of its superior treatment efficiency, ease of operation, environmental friendliness, and cost-effectiveness. This study investigated the adsorption characteristics and mechanisms of Cd2+ solutions by Lactobacillus plantarum adsorbed immobilized on distiller's grains biochar (XIM) and Lactobacillus plantarum-encapsulated immobilized on distiller's grains biochar (BIM). The findings reveal that the maximum adsorption capacity and efficiency were achieved at a pH solution of 6.0. Specifically, at an adsorption equilibrium concentration of cadmium at 60 mg/L, XIM and BIM had adsorption capacities of 8.40 ± 0.30 mg/g and 12.23 ± 0.05 mg/g, respectively. BIM demonstrated noticeably greater adsorption capacities than XIM at various cadmium solution concentrations. A combination of isothermal adsorption modeling, kinetic modeling, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffractometer (XRD), and Fourier-transform infrared spectroscopy (FTIR) analyses showed that cadmium adsorption by XIM primarily involved physical adsorption and pore retention. In contrast, the adsorption mechanism of BIM was mainly attributed to the formation of Cd(CN)2 crystals.

Competitive sequestration behavior and mechanism of Cd2+, Pb2+and Ni2+ ions from single, binary and ternary metal laden solution by Hevea brasiliensis wood sawdust (HBS)

HeveaBrasiliensis wood sawdust (HBS), a lignocellulosic material, was employed for the eradication of Cd(II), Pb(II), and Ni(II) from synthetic single and multi-metalsystem. In the realm of multimetal adsorption, HBS exhibited the most substantial adsorption capacities for heavy metals, in the order: Pb(II) > Cd(II) > Ni(II). Experiments involving batch process were carried out to explore the rolesofpH, contact duration, HBS quantity, and preliminary metal concentrations on the adsorption capacity. Optimal conditions for biosorption of metal ions were determined as pH 5.0, dosage of 7 gL−1, and an equilibrium time of 90 min. The pseudo-second-order kinetics andLangmuirisotherm had a favorable alignment with the biosorption of all individual metal ions. Adsorption capacity was 8.45, 13.01 and 6.04 mg g− 1 for Cd, Pb and Ni respectively in single metal system. In binary and ternary system the capacity and adsorption percentages decreases significantly due the presence of competitive metal ions. HBS demonstrated effectiveness in treating real wastewater containing Cd2+, Pb2+and Ni2+ ionsin both single and mixed metal solutions, highlighting the necessity of thoroughly considering the impact of competitive adsorption. SEM with EDS results indicated single metal fixing in a multi-ion solution followed complex mechanisms. The surface area and functional group studies were conducted utilizing BET and a FTIR Spectrometer. Electrostatic attraction and complexation mechanisms were identified as responsible factor for capturing metal ions to the active surfaces of the bio sorbent. Cost analysis reflected the adsorbent cost was $0.021 per liter of mixed contaminated ternary effluent (30 mg L−1).

Immobilization Behavior and Mechanism of Cd2+ by Sulfate-Reducing Bacteria in Anoxic Environments

It is vital to remove cadmium from wastewater because of its potential harm to the natural environment and human health. It was found that sulfate-reducing bacteria (SRB) had a good fixing effect on Cd under a strict anaerobic environment. However, there are few reports on the immobilization effect and mechanism of SRB on Cd in an anoxic environment. This study revealed the effects of initial Cd2+ concentration, initial SO42− concentration, temperature, pH, and C/N ratio on the immobilization of Cd2+ by SRB in aqueous solution under an anoxic environment. The experimental results showed that under the conditions of initial concentration of Cd2+ within 0 mg/L~30 mg/L, initial concentration of SO42− within 1200 mg/L, temperature within 25 °C~35 °C, pH neutral, and C/N ratio of 20:1, the immobilization rate of Cd2+ by SRB is above 90%. The characterization results showed that bioadsorption and chemical precipitation were the main mechanisms of SRB immobilization of Cd2+ in an anoxic environment.

Realizing High Performance Tunable Sensing Mode and Selectivity of Metal Ions Based on Carbon Dot

AbstractWe have adopted a straightforward, eco‐friendly and economically profitable pyrolysis route of tailoring quantum dot size carbon particles (CD) from the leaves of Arundo donax. The synthesized uniformly dispersed CD1 and CD2 have an average diameter of 4.5 nm and 3.5 nm respectively as determined via HRTEM. FT‐IR analysis corroborated nitric acid treatment leads to rich surface functionalization of CD2. Experimentally estimated average fluorescence (FL) lifetime of the as‐prepared CD1 and CD2 are 2.31 ns and 3.87 ns respectively. Juxtapose to other metal ions, Cd+2 ions can efficiently quench FL of CD1, while Cr+6 ions, on contrary, prominently enhanced FL of CD2. Benefitting from their FL response, a turn off sensor was built using CD1 to detect Cd+2 ions and a turn on‐off sensor by CD2 to sense Cr+6 with impressive limit of detections of 2.58 nM and 1.73 nM respectively. They exhibit superior performance compare to other documented nanoscopic materials. The FL “turn off” interaction mechanism of CD1 was attributed mainly to static quenching. While that of “turn on‐off” mechanism for CD2 was ascribed to chelation enhanced fluorescence phenomenon and a rare partial combination of inner filter effect plus dominate dynamic type of quenching.

Efficient extraction performance and mechanisms of Cd2+ and Pb2+ in water by novel dicationic ionic liquids

Ten novel hydrophobic dicationic ionic liquids (DILs) were synthesized and applied for the extraction of heavy metals in aqueous solutions. Their physicochemical properties were measured at ambient temperature, and the leaching behaviors of the as-prepared DILs in water were assessed by TOC analysis. Metal extraction experiments were carried out to evaluate the extraction performances of the DILs. It was found that the extraction rates of up to 0.45 and 0.53 mg·(g·min)−1 were achieved with 100 mg DILs for 5 mL of 5 mg/L Cd2+ and Pb2+ solutions. Besides, the extraction efficiencies of Cd2+ and Pb2+ were respectively up to 95.48% and 98.46%, when the volumes of the simulated wastewater were expanded by a factor of 20 at a constant extraction phase ratio (1000 mg DILs for 50 mL of 5 mg/L Cd2+ or Pb2+ solutions). The reusability of the novel DILs was successfully proved by the back-extraction experiments with 0.5 M HNO3. Finally, taking Cd2+ extraction as an example, the extraction mechanism based on FTIR analysis and quantum chemical calculations showed that both S and O atoms in the anions of DILs had physical and quasi-chemical interactions with Cd2+, which were stronger than the electrostatic attraction.

High efficiency and mechanisms of Cd2+, Cu2+, Mn2+ removal from aqueous solution by modified tobermorite

In this work, nanoscale magnesium oxide and activated carbon were simultaneously loaded on tobermorite through a gelation-calcination method. The new composite (TOB@C@MgO) was used as an effective adsorbent to remove Cd2+, Cu2+, and Mn2+ from aqueous solution and actual wastewater. Its specific surface area was determined to be 146.90 m2/g, and its sedimentation property was found to be satisfactory. At an initial ion concentration of 500 mg/L, a solution pH of 5.2 ± 0.2, an adsorbent dosage of 1.5 g/L, and a temperature of 25 °C, the adsorption equilibrium for Cd2+, Cu2+, and Mn2+ was reached within 2 h, 4 h, and 6 h, with a removal efficiency of 100 %, 90 %, and 64 %, respectively. The pseudo-second-order model and Langmuir model fitted the kinetic and isothermal adsorption data well. The maximum adsorption capacity for Cd2+, Cu2+, and Mn2+ by TOB@C@MgO, as calculated from the Langmuir model, was 1000.00 mg/g, 526.32 mg/g, and 416.67 mg/g, respectively. The selective sequence of metal ions by TOB@C@MgO was in the order of Cd2+ > Cu2+ > Mn2+. Besides, TOB@C@MgO demonstrated effective treatment of actual wastewater, and exhibited reasonably good reusability and stability. Different characterizations revealed that Cd2+, Cu2+, and Mn2+ removal by TOB@C@MgO was primarily dominated by ion exchange. Surface precipitation/complexation, interaction with π electrons, and physical adsorption also contributed to the fixation of Cd2+, Cu2+, and Mn2+ onto the surface of TOB@C@MgO.

Insight into the Mechanism of Cd2+ Removal by MgAl Layered Double Hydroxides with Different Host-Guest Interactions.

Layered double hydroxides (LDHs) have shown great potential as adsorbents for the removal of heavy metals. Nevertheless, how the host-guest interactions of LDHs affect the removal mechanism remains to be less explored. Herein, CO3 2- /NO3 - /SO4 2- /Cl- intercalated MgAl-LDHs with different host-guest interactions were fabricated and their removal mechanism for Cd2+ was investigated. The removal capacity increased in the order of MgAl-CO3 (127.3 mg/g)<MgAl-SO4 (173.3 mg/g)<MgAl-NO3 (305.0 mg/g)≈MgAl-Cl (312.5 mg/g). The quasi-in-situ XRD and XAS demonstrated that Cd2+ was removed as CdCO3 for MgAl-CO3 , while for MgAl-Cl/NO3 /SO4 , Cd2+ was removed as CdAl-LDHs by an isomorphic substitution mechanism. DFT calculations revealed that compared to the CdAl-LDHs formation the Gibbs free energy of the CdCO3 formation was lower, which made it easier to remove Cd2+ as CdCO3 on MgAl-CO3 . Conversely, isomorphic substitution of MgAl-NO3 to obtain CdAl-LDHs was a free energy reduction process.

Potential application of Curtobacterium sp. GX_31 for efficient biosorption of Cadmium: Isotherm and kinetic evaluation

In this study, the adsorption capacity and mechanism of Cd2+ by both live and dead Curtobacterium sp. GX_31 biomasses were evaluated using a batch experiment, adsorption isotherm and kinetic models, scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) analysis. The optimal pH, dosage, and contact time were 6.0, 1.0 g/L, and 60 min, respectively. Under optimal conditions, the removal efficiency was >90% for the live biomass and close to 100% for the dead biomass at an initial Cd2+ concentration of ≤10 mg/L, and the maximum adsorption capacities were 37.04 and 40.16 mg/g for the live and dead biosorbents with 200 mg/L Cd2+. The R2 values of the isotherm models indicated that the Temkin isotherm model was best fitted for both the live and dead biomass. The parameters KL (0.3998 vs. 5.1066), n (4.0177 vs. 6.0205), and bT (507.7947 vs. 675.3512) implied that the dead cells had a higher affinity, stronger adsorption, and higher binding energy than the live cells. The kinetic study showed that the pseudo-second-order model was more suitable for depicting the biosorption process, demonstrating that the rate-limiting step might be chemisorption and more than one step, which was confirmed by the intra-particle diffusion model. SEM analysis identified Cd2+ adsorbed onto the cell surface. FT-IR spectra suggested that hydroxyl, amino, carboxyl, sulphate and carbonyl functional groups might be involved in Cd2+ adsorption. Based on the results obtained, Curtobacterium sp. GX_31 might be a promising novel biosorbent for Cd2+-contaminated soil or water, especially at lower concentrations.

A biphenyl thiosemicarbazide based fluorogenic chemosensor for selective recognition of Cd2+: application in cell bioimaging.

A diversified biphenyl thiosemicarbazide based chemosensor (HBMC) has been fabricated and reported for the specific detection of Cd2+ in a MeOH : H2O (4 : 1) solution. We observed a chromogenic change from colorless to light yellow colour, and it showed a "turn-on" fluorogenic change from non fluorescent to blooming cyan colour. In fluorometric titration a sharp "turn-on" emission for Cd2+ was observed with a ∼16 fold increase in fluorescence intensity value at 496 nm by incremental addition of Cd2+ ions in the MeOH : H2O (4 : 1) solution. The reversibility of the chemosensor (HBMC) was confirmed by a sequential addition of the EDTA solution. Again the binding stoichiometry of HBMC with Cd2+ was found to be 2 : 1, as confirmed by Job's plot analysis and HRMS spectra of the HBMC-Cd2+ complex. The mechanism for Cd2+ sensing in MeOH : H2O (4 : 1) is based upon the inhibition of CN isomerization and ESIPT process and simultaneously turning on the CHEF (chelation enhanced fluorescence) process. The limit of detection for Cd2+ was found to be in the order of 10-8 (M), which implies that HBMC is an efficient probe to detect Cd2+ at the microscopic level. A reusability study was performed and on-sight detection of cadmium ions by the chemosensor (HBMC) was established by dip-stick experiment. In vitro detection of Cd2+ in human breast cancer cells (MDA-MB-231) by HBMC discloses its cell permeability and biocompatible nature. Computational studies (DFT and TDDFT) with the probe HBMC and HBMC-Cd2+ complex were also performed.

Adsorption characteristics and mechanisms of Cd2+ from aqueous solution by biochar derived from corn stover

Corn stover could be pyrolysed to prepare biochar for removing pollutants in water and realizing the resource utilization of biomass. The aims of the present study were to investigate the optimal preparation and adsorption conditions of biochar and to reveal the adsorption characteristics and mechanisms of Cd2+ in water by biochar. For this purpose, with Cd2+ as the target pollutant, the pyrolysis conditions involved in the pyrolysis temperature, retention time, and heating rate were evaluated and optimized. Additionally, the characteristics, mechanisms and optimal adsorption conditions of Cd2+ by biochar were determined. A series of characterization techniques was employed, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and specific surface area analysis (SBET). The optimum pyrolysis parameters were a pyrolysis temperature of 700 °C, a retention time of 2.5 h, and a heating rate of 5 °C/min. Acid/base modification did not improve the adsorption capacity of biochar. The Langmuir and the Elovich model were the most suitable isotherm and kinetic models for equilibrium data, respectively. The maximum adsorption capacity fitted by Langmuir model was 13.4 mg/g. Furthermore, mineral precipitation and π electron interactions were shown to be the main adsorption mechanisms of Cd2+. The optimum adsorption conditions for Cd2+ in water were a CaCl2 electrolyte solution of 0.01 mol/L, a pH level of 6.7, and a biochar dosage of 0.4 g. Our results indicated that corn stover biochar was an appropriate approach for improving the status of water with Cd2+ contamination in the short term and for promoting a new perspective for the rational utilization of corn stover and the low-cost pollution control of heavy metals in water.

Understanding Cd2+ Adsorption Mechanism on Montmorillonite Surfaces by Combining DFT and MD

The adsorption mechanism of Cd2+ on different cleavage planes of montmorillonite was investigated using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The most stable adsorption energies of Cd2+ on the (001) and (010) surfaces were −88.74 kJ/mol and −283.55 kJ/mol, respectively. On the (001) surface, Cd2+ was adsorbed on the centre of the silicon–oxygen ring by electrostatic interactions, whereas on the (010) surface, Cd2+ was adsorbed between two ≡Al–OH groups and formed two covalent bonds with O, which was mainly due to the interaction between the Cd s and O p orbitals. Upon the partial substitution of Na+ by Cd2+, Cd2+ was adsorbed on the (001) surface as inner-sphere surface complexes, with a hydration number of 5.01 and a diffusion coefficient of 0 m2/s. Whereas, when Cd2+ completely replaced Na+, part of the Cd2+ moved from the inner-sphere surface complexes to the outer-sphere surface complexes owing to its competitive adsorption. In this case, its hydration number became 6.05, and the diffusion coefficient increased to 1.83 × 10−10 m2/s. This study provides the theoretical background necessary for the development of montmorillonite-based adsorbents.

Effect of oxidative aging of biochar on relative distribution of competitive adsorption mechanism of Cd2+ and Pb2+

In this study, aged biochar (CCB350 and CCB650) were obtained from pyrolysis of corn stalk biochar (CB350 and CB650) at the degree of 350 °C and 650 °C by artificial oxidation with hydrogen peroxide (H2O2). Also, the mechanism of Pb2+ and Cd2+ on fresh and aged biochars was analyzed qualitatively and quantitatively by batch adsorption experiments combined with characterization. The adsorption isotherm results showed that aging treatment decreased the adsorption capacity of Pb2+ and Cd2+ and inhibited the competitive adsorption behavior of heavy metals. In the single-metal system, precipitation and cation exchange were considered as the main adsorption mechanisms for CB350 and CB650, with a ratio of 40.07–48.23% and 38.04–57.19%, respectively. Competition between Pb2+ and Cd2+ increased the relative contribution of mineral precipitation, but decreased the contribution of cation exchange mechanism. Aging resulted in the rise of the contribution of surface complexation to the adsorption of Pb2+ and Cd2+ on biochars, especially in low-temperature biochars, but weakened the contribution of mineral precipitation to the adsorption. Further, the contribution of other adsorption mechanisms was significantly enhanced for high-temperature aged biochars. These results are important to evaluate its long-term application prospects in the natural environment.

Enhanced removal of Cd2+ by nano zero-valent iron modified attapulgite from aqueous solution: Optimal design，characterization and adsorption mechanism

Nano zero-valent iron (nZVI) modified attapulgite composite (nZVI@ATP) was prepared by liquid phase reduction method for Cd2+ removal from aqueous solution. A series of characterization methods confirmed that nZVI particles with a particle size of 50–100 nm were evenly distributes on the surface of attapulgite after pickling, which greatly overcomes the agglomeration of nZVI. Composite material had the optimum removal rate of Cd2+ when the ratio of iron to attapulgite was 1: 2. More than 98% of Cd2+ was removed from aqueous solution using nZVI@ATP at an initial condition of 100 mg/LCd2+ under the conditions of 1 g/L of nZVI@ATP, pH 5.0 and a temperature of 25 ℃, much higher than that of attapulgite. Kinetic studies revealed that Cd2+ adsorption process followed the pseudo-second-order model, and basically reached the adsorption equilibrium after 2 h, indicating that chemisorption was the dominant adsorption mechanism. Adsorption thermodynamics showed that the adsorption process was a spontaneous endothermic reaction, accompanied by the increase in entropy. The Freundlich adsorption isotherm model could well fit the adsorption process. The presence of Na+, Ca2+ and Mg2+ in the solution strongly inhibited the removal of Cd2+. The mechanism of Cd2+ removal by nZVI@ATP involved multiple processes, mainly including surface-complexation adsorption and precipitation/co-precipitation. The results exhibited that nZVI@ATP has excellent potential as an adsorbent for the removal of Cd2+ from the contaminated water.

Characterization of Biochars Produced by Co-Pyrolysis of Hami Melon (Cantaloupes) Straw Mixed with Polypropylene and Their Adsorption Properties of Cadmium.

Reuse of waste from Hami melon (cantaloupes) straws (HS) mingled with polypropylene (PP) ropes is necessary and beneficial to mitigate environmental pollution. The objective of this study was to investigate the characteristics and mechanisms of Cd2+ adsorption on biochars produced by co-pyrolysis of HS-PP with various mixing ratios. N2-sorption, scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), elemental analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravity, and differential thermal gravity (TG/DTG) were applied to evaluate the physicochemical properties of materials. Batch adsorption experiments were carried out for investigating the effects of initial pH, Cd2+ concentration, and adsorption time. It was found that the Langmuir and pseudo-second-order models fitted best for the experimental data, indicating the dominant adsorption of co-pyrolysis biochars is via monolayer adsorption. Biochar derived at 4/1 mixing ratio of HS/PP by weight percentage had the highest adsorption capacity of 108.91 mg·g−1. Based on adsorption isotherm and kinetic analysis in combined with EDS, FTIR, and XRD analysis, it was concluded that the main adsorption mechanism of co-pyrolysis biochar involved the surface adsorption, cation exchange, complexation of Cd2+ with surface functional groups, and chemical precipitation. This study also demonstrates that agricultural wastes to biochar is a sustainable way to circular economy.

Single and Binary Adsorption Behaviour and Mechanisms of Cd2+, Cu2+ and Ni2+ onto Modified Biochar in Aqueous Solutions

The chitosan–EDTA modified magnetic biochar (E–CMBC) was successfully used as a novel adsorbent to remove heavy metals. The adsorption behaviour and mechanisms of E–CMBC to Cd2+, Cu2+ and Ni2+ were performed in single and binary system in aqueous solutions. In single–metal system, the adsorption process of Cd2+, Cu2+ and Ni2+ on E–CMBC fitted well with the Avrami fractional–order kinetics model and the Langmuir isotherm model. The measured maximum adsorption capacities were 61.08 mg g−1, 48.36 mg g−1 and 41.17 mg g−1 for Cd2+, Cu2+ and Ni2+, respectively. In binary–metal system, coexisting ions have obvious competitive adsorption behaviour on E–CMBC when the concentration of heavy meal beyond 20 mg L−1. The maximum adsorption capacities of the heavy metals were found to be lower than that in single–metal system. The order of the competitive adsorption ability was Cu2+ &gt; Ni2+ &gt; Cd2+. Interestingly, in Cd2+–Cu2+ system the earlier adsorbed Cd2+ could be completely replaced by Cu2+ from the solution. Different competitive adsorption ability of those heavy metal were due to the characteristics of heavy metal and resultant affinity of the adsorption sites on E–CMBC. The adsorption mechanism indicated that chemical adsorption played a dominating role. Therefore, E–CMBC could be a potential adsorbent for wastewater treatment.

Ziziphus jujube waste-derived biomass as cost-effective adsorbent for the sequestration of Cd2+ from aqueous solution: Isotherm and kinetics studies

This investigation reports Ziziphus jujube waste seeds derived biomass adsorbent (ZYB) prepared via chemical activation (ZnCl2) for the sequestration of cadmium ions (Cd2+) from aqueous solution. The prepared adsorbent was characterized by XRD, FTIR, SEM, EDX to appraise the physicochemical characteristics of adsorbent as well as the mechanism of Cd2+adsorption. Influence of process parameters like dose, time, initial concentration, and pH, related to adsorption was studied by employing batch mode. Different Isotherm and Kinetic models were employed to analysis equilibrium data. Freundlich isotherm model best suited with higher R2 value 0.978 facilitating multilayer adsorption on to heterogenous surface of ZYB. Maximum adsorption capacity was found to be 49.40 mg/g. Pseudo-second order governs the reactions kinetics. Regeneration of Cd2+ loaded adsorbent was performed through four consecutive adsorption–desorption cycles without greater loss in efficiency. Thus, better sorption capacity, good regeneration potential, economic feasibility along with environmentally friendly nature corroborates ZYB as a potential adsorbent.

Quantitative analysis on the mechanism of Cd2+ removal by MgCl2-modified biochar in aqueous solutions

In this study, a pristine biochar (BC) and MgCl2-modified biochar (MBC) were prepared using Pennisetum sp. straw for removing Cd2+ from aqueous solutions. Scanning electron microscope (SEM) imaging combined with energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), as well as the surface area and porosity analyses were used to reveal the physico-chemical characteristics of the pristine and modified adsorbents. Results suggested that MgCl2 impregnation during the synthesis had enhanced the specific surface area and pore volume of the biochar. Batch adsorption experiments indicated that the Cd2+ adsorption data of MBC fitted the Langmuir isothermal and pseudo-second order kinetic models, indicating a chemical adsorption was undergoing in the system. The maximum adsorption capacity of Cd2+ on MBC was 763.12 mg/g, which was 11.15 times higher than that of the pristine BC. The Cd2+ removal by MBC was mainly attributed to the mechanisms in an order: Cd(OH)2 precipitation (73.43%) > ion exchange (22.67%) > Cd2+-π interaction (3.88%), with negligible contributions from functional group complexation, electrostatic attraction and physical adsorption. The MBC could thus be used as a promising adsorbent for Cd2+ removal from aqueous solutions.

Adsorption of Cd2+ Ions from Aqueous Solution Using Biomasses of Theobroma cacao, Zea mays, Manihot esculenta, Dioscorea rotundata and Elaeis guineensis

In this work, the mechanisms of cadmium (Cd2+) adsorption on residual biomasses from husks of yam (Dioscorea rotundata), cassava (Manihor esculenta), cocoa (Theobroma cacao), corn (Zea mays) and oil palm bagasse (Elaeis guineensis) were studied in order to evaluate the effect of temperature, adsorbent dose and particle size in a batch system. Isotherms and adsorption kinetics were determined and adjusted to different models. The biomaterials were characterized using the techniques of Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Results reveal that the possible mechanisms of Cd2+ adsorption in bioadsorbents were ion exchange and complexation with -COOH and -OH groups. From the experimentation, it was found that best conditions were presented at 55 °C, particle size 0.5 mm and 0.03 g adsorbent. The following biomass performance was obtained in terms of adsorption capacities: cocoa husk (CH) &gt; corn cob residues (CCR) &gt; cassava peel (CP) &gt; palm bagasse (OPB) &gt; yam peel (YP), according to the Langmuir and Dubinin- Radushkevich (D-R) models. The equilibrium of Cd2+ adsorption over YP and OPB was well described by Langmuir’s isothermal model, while for CH, CCR and CP the model that best fit experimental data was Freundlich’s model. The results of D-R model suggested that the process is controlled by physisorption mechanism with strong interactions among active sites and Cd2+ ions. The kinetics for all systems studied fit the pseudo-second order model. The values of the thermodynamic parameters established that cadmium removal is of endothermic nature and not spontaneous using YP and CP, and exothermic, spontaneous and irreversible when using OPB, CH and CCR. The results suggest the use of YP, OPB, CH, CP and CCR residues for the removal of aqueous Cd2+.

Laboratory Adsorption Studies on Cadmium (II) by Nonwoven Chitosan/Phosphorylated Microcellulose Nanocomposite

The rapid growth of human population and global industrialization has resulted in the generation of larger amounts of wastewater containing various pollutants, among which toxic heavy metals. Adsorption is efficient for this purpose, but its application is limited by the high cost of adsorbent materials. Chitosan (CS) and phosphorylated microcellulose (PMC) have a high potential as low-cost and effective adsorbents for water remediation. Nonwoven CS/PMC nanocomposite fiber mats were produced by electrospinning with up to 50% by weight of PMC. The thermal, chemical, and morphological properties of the mats were studied. Batch adsorption trials were carried out using Cd2+ ions. Kinetics and isotherm models were tested against experimental results and the thermodynamic properties were calculated. Results showed that the pseudo-second order model best fitted experimental data and suggested chemisorption as the mechanism for Cd2+ removal. Langmuir isotherm best described equilibrium data reaching the maximum adsorption capacity of 283 mg/g at 60 °C. This high value was attributed mainly to the large amount of phosphate groups, which require less energy to capture the metal cations. Thermodynamic evaluation suggested that the adsorption is a spontaneous endothermic reaction. These results confirm that CS/PMC mats are easy to produce, and provide high adsorption capacity in simulated wastewater containing Cd2+. These laboratory-based adsorption experiments will assist in selecting/ranking of potential candidate matrices, and scale-up development of technologies for complex wastewater applications.