Adsorption Of Cd Research Articles

Biosorption of Cd(II), Co(II), and Cu(II) onto Microalgae under Acidic and Neutral Conditions

The biosorption of Cd, Co, and Cu onto three microalgae species (Chlorella vulgaris, Scenedesmus sp., and Spirulina platensis) was compared to determine the microalgae’s capability for heavy metal adsorption in acidic and neutral environments. The Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models were used to characterize the adsorption of the heavy metals onto microalgae. The maximum adsorption capacity (qmax) determined using the Langmuir and D-R model showed results in the order of Cu > Co > Cd in both acidic and neutral conditions. A shift from acidic to neutral conditions increased the microalgae’s adsorption affinity for heavy metals, as determined using the Freundlich parameter (KF). The adsorption affinity of the biomass for Cd and Co was in the order S. platensis > C. vulgaris > Scenedesmus sp. while that of Cu was in the order C. vulgaris > Scenedesmus sp. > S. platensis. In addition, it was found that the adsorption of Cd and Co enhanced the production of Dissolved Organic Content (DOC) as a byproduct of biosorption, whereas the adsorption of Cu appeared to suppress the generation of DOC. The mean adsorption energy (E) values computed by the D-R model were less than 8 (kJ/mol), indicating that physisorption was the primary force of sorption in both acidic and neutral settings. The findings of this study suggest that microalgae may be used as a low-cost adsorbent for metal removal from industrial effluent.

Quantitative Soil Characterization for Biochar-Cd Adsorption: Machine Learning Prediction Models for Cd Transformation and Immobilization.

Soil pollution with cadmium (Cd) poses serious health and environmental consequences. The study investigated the incubation of several soil samples and conducted quantitative soil characterization to assess the influence of biochar (BC) on Cd adsorption. The aim was to develop predictive models for Cd concentrations using statistical and modeling approaches dependent on soil characteristics. The potential risk linked to the transformation and immobilization of Cd adsorption by BC in the soil could be conservatively assessed by pH, clay, cation exchange capacity, organic carbon, and electrical conductivity. In this study, Long Short-Term Memory (LSTM), Bidirectional Gated Recurrent Unit (BiGRU), and 5-layer CNN Convolutional Neural Networks (CNNs) were applied for risk assessments to establish a framework for evaluating Cd risk in BC amended soils to predict Cd transformation. In the case of control soils (CK), the BiGRU model showed commendable performance, with an R2 value of 0.85, indicating an approximate 85.37% variance in the actual Cd. The LSTM model, which incorporates sequence data, produced less accurate results (R2=0.84), while the 5-layer CNN model had an R2 value of 0.91, indicating that the CNN model could account for over 91% of the variation in actual Cd levels. In the case of BC-applied soils, the BiGRU model demonstrated a strong correlation between predicted and actual values with R2 (0.93), indicating that the model explained 93.21% of the variance in Cd concentrations. Similarly, the LSTM model showed a notable increase in performance with BC-treated soil data. The R2 value for this model stands at a robust R2 (0.94), reflecting its enhanced ability to predict Cd levels with BC incorporation. Outperforming both recurrent models, the 5-layer CNN model attained the highest precision with an R2 value of 0.95, suggesting that 95.58% of the variance in the actual Cd data can be explained by the CNN model's predictions in BC-amended soils. Consequently, this study suggests developing ecological soil remediation strategies that can effectively manage heavy metal pollution in soils for environmental sustainability.

Effects of aging processes on spent mushroom Substrate-Derived Biochar: Adsorption characteristics of Cd(II) and Cr(VI)

To explore how chemical, physical and biological process impact the adsorption capacity of biochar for cations and anions, five kinds of spent mushroom substrate biochars including PB (carbonized Auricularia auricula substrate at 600 °C for 6 h), NB (Aged PB at 25 °C and 40 % moisture for 12 mon), AB (PB treated with 20 % mixed acid solution at 70 °C for 6 h), FB (PB subjected to 16 freeze–thaw cycles between − 20 °C and 25 °C) and MB (PB incubated with microbes from contaminated soil for 15 cycles) were prepared under simulated conditions, the internal mechanisms were revealed. Results showed that all aging processes caused a variation in crystal quantity and structure on different biochar. AB, NB and MB had higher hydrophilicity and polarity, and more positive charges than PB. Moreover, AB and MB had a higher cation exchange capacity (CEC) (70.7 and 75.3 cmol/kg) and more oxygen-containing functional groups than PB. MB has the maximum adsorption capacity for Cd(II) (24.2 mg/g), followed by PB (23.5 mg/g), FB (22.7 mg/g), NB (22.2 mg/g), and AB (22.0 mg/g). Langmuir model better described the Cd(II) adsorption onto NB, FB, and PB, while Freundlich better described AB and MB. As for Cr(VI), the maximum adsorption capacity followed the order: MB (24.1 mg/g) > AB (23.7 mg/g) > FB (23.5 mg/g) > PB (23.0 mg/g) > NB (22.7 mg/g). Langmuir model was better for Cr(VI) adsorption onto FB and PB, while Freundlich was better for AB, NB and MB. The pseudo-first-order kinetic model fits for Cd adsorption by FB，while the pseudo-second-order kinetic model fit for the adsorption of Cd and Cr by other biochars. The adsorption of Cr by all biochars was significantly related to the content of lactone group. Acidification and organic acids from microorganisms increased the pHPZC values of AB and MB, which was not conducive to the adsorption of Cd. The surface fragmentation of FB caused by the freezing and thawing process promoted its adsorption of Cd.

Synthesis, application and molecular docking of modified cellulose with diaminoguanidine as complexing agent for selective separation of Cu (II), Cd (II) and Hg (II) ions from alum sample

A new modified cellulose with diaminoguanidine (Cel-Gua) synthesized for specific recovery of Cu (II), Cd (II), and Hg (II) from the alum sample. Cellulose was silanized by 3-chloropropyltrimethoxysilane and then was modified with diaminoguanidine to obtain N-donor chelating fibers. Fourier transform-infrared spectroscopy, scanning electron microscopy, X-ray diffraction, zeta potential, electrons disperse X-ray analysis, elemental analyses (C, H and N), and thermogravimetric analysis were used for characterization. Factors influencing the adsorption were thoroughly examined. Under the optimal conditions, the Cel-Gua sorbent displayed maximum adsorption capacities of 94.33, 112.10 and 95.78 mg/g for Cu (II), Cd (II), and Hg (II), respectively. The sorption process of metal ions is equipped by kinetic model PSO and Langmuir adsorption isotherm. The calculated thermodynamic variables confirmed that the adsorption of Cu (II), Cd (II) and Hg (II) by Cel-Gua sorbent is a spontaneous and exothermic process. In our study, we used the molecular operating environment software to conduct molecular docking simulations on the Cel-Gua compound. The results of the docking simulations showed that the Cel-Gua compound displayed greater potency and a stronger affinity for the Avr2 effector protein derived from Fusarium oxysporum, a fungal plant pathogen (code 5OD4). The adsorbent was stable for 7 cycles, thus allowing its safe reutilization.

Removal and stabilization of As and Cd in water/soil using silicate-supported nano zero-valent iron composites: Preparation, behavior, mechanism and cost analysis

A novel silicate-supported nano zero-valent iron composite material (nZVI@SS) for the removal and stabilization of arsenic (As) and cadmium (Cd) in water/soil had been developed through the modification of low-grade oolitic iron ore (OI) by reduction, while refinery sludge (RS) as reductant, manganese carbonate (MC) as additive in this work. The As and Cd adsorption capacity of nZVI@SS reached 93.91 mg·g−1 and 265.81 mg·g−1, respectively. Its specific surface area and pore volume increased by 19.28 m2·g−1 and 0.24 cm3·g−1, respectively when compared with unmodified OI. In the actual soil leaching process, using 2 % nZVI@SS for 30 days, the leaching concentrations of As and Cd decreased by 87.86 % and 85.51 % respectively, while their bioavailable contents were reduced by 15.59 mg·kg−1 and 1.40 mg·kg−1, correspondingly. The formation of chemical precipitates as Fe-As, Ca-As compounds, and Cd(OH)2 was the main mechanism of their adsorption process. Therefore, HMs adsorbed by nZVI@SS were difficult to desorb, making it more suitable for passivation/stabilization of HMs in groundwater/soil. Furthermore, the production cost of nZVI@SS was approximately 50 $/T, below the average market value of comparable adsorption materials. This method made low-grade minerals into environmentally friendly materials with high added value, significantly reduced the environmental risk of HMs in water/soil, and provided a new approach for the development of sustainable environmentally friendly materials using hazardous waste RS as a resource.

Removal of Cd(II) from aqueous solution using biosorbent based on agricultural waste sorgum bagasse (Sorghum bicolor (L.) Moench) activated NaOH

ABSTRACT Cadmium (Cd(II)) contamination is very harmful to the aquatic environment. Currently, the removal of Cd(II) from water is widely studied to reduce its toxicity. In this study, agricultural waste sorghum bagasse (SB) was activated with NaOH and used to adsorb Cd(II) in aqueous solution. NaOH-activated sorghum bagasse (SB-NaOH) was characterised using Fourier transform infrared spectroscopy (FTIR) to investigate the functional groups, scanning electron microscopy (SEM-EDX) to observe surface morphology, X-ray diffraction (XRD) to analyzed the structure and chemical composition, and Brunauer–Emmett–Teller (BET) method to evaluate pore size. The batch system was used to investigate the adsorption parameters such as adsorbent mass, contact time, initial concentration, pH, and temperature. The optimum conditions of Cd(II) adsorption were at pH 5, 70 min, 600, 100 mg/L, and 30°C. The maximum adsorption percentage was 96.48%. The pseudo-second-order is suitable for kinetic models of Cd(II) adsorption and the isotherm model was Langmuir model. The Gibbs free energy obtained a positive value and the enthalpy had a negative value, indicating that the adsorption of Cd(II) is an exothermic process. Therefore, SB-NaOH adsorbent can be used as a potential adsorbent with easy and economical treatment to reduce Cd(II) in the aquatic environment.

Adsorption of cadmium (II) on organic xerogel microspheres: effect of adding sepiolite or vermiculite and operating conditions on the adsorption capacity.

The organic xerogel (OX) was synthesized through sol-gel polymerization of formaldehyde and resorcinol in inverse emulsion using Na2CO3 as a catalyst. Meanwhile, OX containing sepiolite (OX-Sep) and vermiculite (OX-Ver) were prepared similarly to OX but adding clays during synthesis. All materials were mesoporous and presented spherical morphology, and the surface of these materials exhibited an acidic character because the concentration of acidic sites was higher than those of basic sites. Cd(II) adsorption from aqueous solutions onto OX, OX-Sep, and OX-Ver was examined, and the OX-Sep showed the highest adsorption capacity towards Cd(II) of 189.7mg/g, being 1.5, 2, and 36 times higher than that of OX-Ver, OX, and Sep. The OX-Sep capacity for adsorbing Cd(II) was significantly lessened by decreasing the pH from 7 to 4 and raising the ionic strength from 0.01 N to 0.1 N. This trend was ascribed to electrostatic attraction between the Cd+2 in water and the negatively charged surface of OX-Sep. Besides, desorption studies at pH 4 showed that the average desorption percentage of Cd(II) adsorbed on OX-Sep was 80%. The characterization results and the effect of the operating conditions on the adsorption capacity proved that electrostatic attraction and cation exchange play a crucial role in the adsorption mechanism.

Aging properties of polyethylene and polylactic acid microplastics and their adsorption behavior of Cd(II) and Cr(VI) in aquatic environments

In this study, we examined the aging characteristics of polyethylene (PE) and polylactic acid (PLA) microplastics (MPs), examining the adsorption behaviors and mechanisms concerning Cd(II) and Cr(VI) under both single and binary systems. The results revealed that aging treatment changed the physicochemical properties of MPs. The aging mechanisms of PLA and PE MPs were shown to be similar by the 2D-FTIR-COS study. These mechanisms involve the formation of oxygen-containing functional groups through the combination of carbon chain breakdown and oxygen. Aged MPs had a greater ability to adsorb metal ions than pristine MPs, with PLA MPs outperforming PE MPs. After 30 days of aging, Cd(II) adsorption increased by 40.61 % and 25.49 % for PE and PLA MPs, respectively, while Cr(VI) adsorption increased by 37.50 % and 69.29 %, respectively. The adsorption ability of PE and PLA MPs with Cd(II) or Cr(VI) under binary systems was less than that under single systems, with Cd(II) exhibiting more adsorption competitiveness than Cr(VI). Humic acid (HA), ionic species and strength, solution pH, and adsorption of Cd(II) and Cr(VI) were found to be significantly correlated. Further investigation into the adsorption mechanisms of Cd(II) and Cr(VI) on PE and PLA MPs revealed that pore-filling, electrostatic interactions, complexation, and hydrogen bonding play important roles in the adsorption process. The study's conclusions are crucial for assessing the risk associated with concurrent contamination by metal ions and microplastics.

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.

Efficient removal of Pb(II) and Cd(II) ions from wastewater using amidoxime functionalized graphene oxide

AbstractThis study aimed to develop iminodiethylamine oxime graphite oxide (IOGO) through the grafting of iminodiethylamine oxime onto graphene oxide (GO) via amidation and oximation. The primary objective was to investigate the adsorption characteristics of Pb(II) and Cd(II) ions on IOGO. Results demonstrated that IOGO exhibited exceptional adsorption capabilities, reaching maximum adsorption capacities of 798.87 mg/g for Pb(II) and 283.50 mg/g for Cd(II). Remarkably, IOGO maintained its high adsorption performance over five consecutive adsorption cycles. Specifically, the adsorption capacity for Pb(II) remained significantly stable at 480.78 mg/g, exhibiting only an 8.77% decrease. Similarly, the Cd(II) adsorption capacity remained robust at 204.13 mg/g, demonstrating a modest reduction of 10.47%. These findings underscore the feasibility of employing IOGO in repeated adsorption processes, thereby showcasing its potential for practical applications in the removal of heavy metals from aqueous solutions.

Adsorption of trace metals onto different plastics during long-term exposure in an estuarine environment: Influence of time, stratified water column, and specific surface area

The pervasive increase of plastics in marine systems and subsequent trace metals (TM) adsorption represents a critical environmental challenge. This long-term study is first to investigate how duration of exposure and stratified water column impact TM adsorption on various plastics in an estuary. We exposed polypropylene (PP), polyethylene (PE), poly(ethylene terephthalate) (PET), and fluorinated ethylene propylene (FEP) to estuarine conditions, categorizing them into three distinct groups to capture diverse human activities: pre-production pellets (Pellets), single-use plastics (SUP) and laboratory plastics (Lab). Plastic and water samples were analyzed before deployment and 1, 4, 7 and 16 months after deployment at three depths in the stratified Krka River estuary (Croatia). We measured TM concentrations, pH and salinity in the water column, and adsorbed TM amounts on plastics. Additionally, we examined plastic sample surfaces by Raman spectroscopy and scanning electron microscopy. TM speciation was modeled from water column data to better explain adsorption processes. Statistical analysis indicates that Zn, Cd, Pb, Ni, and Co adsorption depends on both duration of exposure and stratified water column, while Cu is influenced solely by duration of exposure to estuarine environment. Adsorbed TM amounts varied significantly among the plastic groups (Pellets, SUP and Lab), but not among different polymer types (PP, PE, PET and FEP). A noteworthy observation was the difference in the results of statistical analysis when investigating TM amounts expressed by plastic sample mass and by plastic sample surface area. Results expressed by plastic sample mass showed a difference between SUP group versus Pellets and Lab groups, while results expressed by plastic sample surface area distinguished Pellets group compared to other two groups. Therefore, we suggest presenting TM adsorption results in similar studies both by plastic sample mass and by plastic sample surface area. This approach will improve the understanding of TM adsorption on plastics, and enable more effective comparisons among the scientific literature dealing with plastics of different specific surface areas.

Efficient removal of cadmium and lead in water by using nano-manganese oxide-loaded hydrochloric acid pretreated biochar

Cadmium (Cd) and lead (Pb) contaminated water pose a serious threat to the safety of aquatic organisms and human food, which is a hot topic in the world. To improve the removal efficiency of straw biochar (BC) on Cd and Pb pollution water, the modified biochar (BCHMn) was manufactured by loading nano-manganese oxide (nano-MnOx) on hydrochloric acid pretreated BC. The adsorptive properties of Cd2+ and Pb2+ for BCHMn were examined by isothermal, kinetic adsorption models, and cycle tests. The results indicated that the adsorption of Cd2+ and Pb2+ by BCHMn is suitable for Langmuir, Sips, Avrami, and pseudo-second-order kinetic model, suggesting monolayer and heterogeneous chemical adsorption. The maximum theoretical adsorptive amount of Cd2+ and Pb2+ on BCHMn are 108.21 mg/g and 312.16 mg/g, respectively. The adsorption mechanism of BCHMn is primarily mineral precipitation, π electron interaction, and ion exchange. Moreover, BCHMn contained the special birnessite (δ-MnO2) structures and MnOx, which can form stable complexes with Cd/Pb (such as Mn-O-Cd/Pb and Mn-R-O-Cd/Pb). These results indicate that BCHMn can efficiently remove Cd2+ and Pb2+ from water, and provide a reference for the comprehensive utilization of straw waste and water pollution control.

Investigation of Cd(II) removal mechanism during biogenic Mn(II) oxidation by Cladosporium sp. XM01

Biogenic Mn oxides (BMOs) represent the most prevalent natural form of Mn oxides, having a significant influence on the biogeochemical cycling of Cd in the environment. The surface reactivity of BMOs is intricately linked to their structural characteristics. However, there remains a scarcity of knowledge regarding the structural disparities of BMOs during their formation in the context of heavy metal removal. This study investigates the fine mineralogical characteristics of three BMOs formed by the Mn-oxidizing fungus Cladosporium sp. XM01 during cultivation, namely immature BMO (Imm-BMO), low mature BMO (Low-BMO), and high mature BMO (High-BMO), and their adsorption mechanism for Cd(II). Analysis of Mn K-edge X-ray absorption fine structure indicated three BMOs exhibit a hexagonal birnessite structure with interlayer Mn(II/III), and Imm-BMO (48.6 %) exhibits a higher proportion of Mn(II/III) components compared to Low-BMO (14.4 %) and High-BMO (13.9 %). The results suggested a gradual decrease in Cd(II) adsorption capacity, following the order of Imm-BMO, Low-BMO, and High-BMO. Conversely, Cd(II) showed higher fixation capacity on Low-BMO (56.2 %−63.1 %) and High-BMO (64.4 %−70.6 %) compared to Imm-BMO (45.4 %−52.6 %), indicating an opposite trend in Cd(II) fixation. Specifically, the enhanced Cd(II) fixation performance during BMOs formation can be attributed to the availability of more vacancies and interlayer spaces for Cd(II) occupation and retention, respectively. Additionally, compared with pH 7.5, pH 5.5 was found to be more conducive to Cd(II) fixation on BMOs, attributed to the increased availability of more vacancies. Overall, this study enhances our understanding of the structural transformation during BMOs formation and its implication for Cd(II) adsorption behavior.

The critical role of organic matter for cadmium-lead interactions in soil: Mechanisms and risks

Understanding the interaction mechanisms between complex heavy metals and soil components is a prerequisite for effectively forecasting the mobility and availability of contaminants in soils. Soil organic matter (SOM), with its diverse functional groups, has long been a focal point of research interest. In this study, four soils with manipulated levels of SOM, cadmium (Cd) and lead (Pb) were subjected to a 90-day incubation experiment. The competitive interactions between Cd and Pb in soils were investigated using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray adsorption near-edge structure (XANES) analysis. Our results indicate that Pb competed with Cd for adsorption sites on the surface of SOM, particularly on carboxyl and hydroxyl functional groups. Approximately 22.6 % of Cd adsorption sites on humus were occupied by Pb. The use of sequentially extracted exchangeable heavy metals as indicators for environment risk assessments, considering variations in soil physico-chemical properties and synergistic or antagonistic effects between contaminants, provides a better estimation of metal bioavailability and its potential impacts. Integrating comprehensive contamination characterization of heavy metal interactions with the soil organic phase is an important advancement to assess the environmental risks of heavy metal dynamics in soil compared to individual contamination assessments.

Urease-producing bacteria combined with pig manure biochar immobilize Cd and inhibit the absorption of Cd in lettuce (Lactuca sativa L.).

The synergistic remediation of heavy metal-contaminated soil by functional strains and biochar has been widely studied. However, the mechanisms by which urease-producing bacteria combine with pig manure biochar (PMB) to immobilize Cd and inhibit Cd absorption in vegetables are still unclear. In our study, the effects and mechanisms of PMB combined with the urease-producing bacterium TJ6 (TJ6 + PMB) on Cd adsorption were explored. The effects of TJ6 + PMB on the Cd content and pH of the leachate were also studied through a 56-day soil leaching experiment. Moreover, the effects of the complexes on Cd absorption and microbial mechanisms in lettuce were explored through pot experiments. The results showed that PMB provided strain TJ6 with a greater ability to adsorb Cd, inducing the generation of CdS and CdCO3, and thereby reducing the Cd content (71.1%) and increasing the pH and urease activity in the culture medium. TJ6 + PMB improved lettuce dry weight and reduced Cd absorption. These positive effects were likely due to (1) TJ6 + PMB increased the organic matter and NH4+ contents, (2) TJ6 + PMB transformed available Cd into residual Cd and decreased the Cd content in the leachate, and (3) TJ6 + PMB altered the structure of the rhizosphere bacterial and fungal communities in lettuce, increasing the relative abundances of Stachybotrys, Agrocybe, Gaiellales, and Gemmatimonas. These genera can promote plant growth, decompose organic matter, and release phosphorus. Interestingly, the fungal communities were more sensitive to the addition of TJ6 and PMB, which play important roles in the decomposition of organic matter and immobilization of Cd. In conclusion, this study revealed the mechanism by which urease-producing bacteria combined with pig manure biochar immobilize Cd and provided a theoretical basis for safe pig manure return to Cd-polluted farmland. This study also provides technical approaches and bacterial resources for the remediation of heavy metal-contaminated soil.

Comparative Linkage of Novel Anti-Tumor Pd(II) Complex with Bio-Macromulecules: Fluorescence, UV-Vis, DFT, Molecular Docking and Molecular Dynamics Simulation Studies.

A novel mononuclear palladium complex, [Pd(dach)(SSA)], where dach and SSA are diaminocyclohexane and sulfosalicylic acid ligands, respectively, has been synthesized and identified utilizing analytical and spectral methods. DFT calculations, namely geometry optimization, MEP, HOMO-LUMO and NBO analysis, have been conducted at B3LYP level by aug-ccpVTZ-PP and 6-311G(d, p) basis sets. NBO and HOMO-LUMO analysis exhibited that the palladium compound is stable. MEP showed the potential sites of molecule for the interaction. By employing MTT assay, the cytotoxicity activity of the aforesaid compound was examined on K562 cell line, which revealed a proper activity compared to cisplatin. To ascertain the lipophilicity of the newly made compound, the partition coefficient measurement was accomplished, which follows the order of cisplatin < Pd(II) complex. Next, investigation of binding properties of the studied compound with DNA of calf thymus and BSA were done by spectroscopic (CD, fluorescence emission and electronic adsorption) and non-spectroscopic (viscosity measurements, DNA gel electrophoresis, molecular docking and molecular dynamics simulation) methods. The outcomes of CD and UV-Vis spectroscopy demonstrated that the title compound refolded the protein via increasing the alpha helix percentage. The data obtained from UV-Vis studies indicated the non-intercalative mutual action between Pd(II) complex with DNA. It also revealed that the Kapp magnitude of CT-DNA (7.43 × 104 M- 1) is higher than the BSA (5.17 × 103 M- 1), and L1/2 (midpoint of transition) of CT-DNA (5 µM) is lower than the BSA (5.7 µM), indicating that the complex has a greater binding affinity to CT-DNA than BSA. Fluorescence quenching mechanism of the two biomolecules by the metal complex is static and the calculated thermodynamic parameters (ΔS° < 0 and ΔH° < 0) suggested the hydrogen bonding and/ or van der Waals forces with DNA and BSA. Further, molecular docking indicated that the studied compound fits into the groove of DNA and the site I of BSA. The stability of metal compound-DNA/-BSA in the presence of H2O solvent and over the time were validated via molecular dynamics simulation.

Statistical modeling and optimization of heavy metals (Pb and Cd) adsorption from aqueous solution by synthesis of Fe3O4/SiO2/PAM: isotherm, kinetics, and thermodynamic

In this study, magnetic material was synthesized using iron salts, then silicon-specific material was used to gain porosity, straight-chain polyacrylamide (PAM) was modified to give the surface functional properties, and the final product synthesized Fe3O4/SiO2/PAM nanocomposite material. Heavy metal (Pb and Cd) removal studies were carried out with the synthesized composite material, considering the central composite design and response surface methodology (CCD-RSM) optimization model. The effects of various parameters, for example, the initial concentration, pH, adsorbent dose, temperature and contact time, were investigated as a part of this study. To optimize these parameters, the CCD-RSM model was applied to design the experiments. Analysis of variance (ANOVA) was applied to evaluate statistical parameters and investigate interactions of variables. In the designed experimental set, the amount of adsorbent (30 mg), pH 7.0 value, temperature (40 °C), initial concentration of Pb (80 mg/L) and Cd (20 mg/L) and 90 min contact time were determined as the optimum conditions. The high coefficient of determination of both metals showed good agreement between experimental results and predicted values (R2 0.99; 0.95). TEM, SEM, XRD, FTIR, BET and Zeta potential analyses were performed to characterize the structure and morphology of the adsorbent. In Pb2+ and Cd2+ heavy metal removal studies, maximum adsorption capacities were determined as 66.54 and 13.22 mg/g, respectively. Additionally, adsorption isotherms, adsorption kinetics and thermodynamic modeling studies were conducted. Features such as large surface area and high adsorption capacity of the synthesized nanoparticles were observed. In this study, Fe3O4/SiO2/PAM demonstrated its potential as an effective adsorbent for the removal of heavy metal ions present in simulated wastewater samples. In particular, we can say that the material has a strong selectivity, as well as a high affinity for Pb(II) ions.

Cadmium Removal by Adsorption on Biochars Derived from Wood Industry and Craft Beer Production Wastes

Cadmium pollution is a serious environmental issue that has an impact on both the ecosystem and human health. As a result, its removal from water is essential. Agro-industrial wastes are suggested as a sustainable adsorbent option, as they are among the most readily available renewable sources worldwide. Biochar is a carbonized biomass that has been shown to be a viable and novel adsorbent. This article compares the results of cadmium adsorption on biochars derived from wood industry and craft beer production wastes. Biochars were characterized before and after adsorption. Batch adsorption results of 0.18 mmol/L Cd(II) concentration solutions indicated adsorption percentages (A%) of 99.7% and 92.2% for sawdust biochar and barley biochar, respectively. For this cadmium concentration, the sawdust biochar presented an adsorption capacity (qm) of 0.0172 mmol/L, while the barley biochar presented a value of 0.0159 mmol/L. The influence of initial Cd(II) concentration on single and multimetal solutions was studied, and a decrease in Cd(II) adsorption on sawdust biochar was observed in the presence of Ni(II) and Zn(II). The Freundlich isotherm model was found to be the best fit to the data for Cd(II) adsorption isotherms on both biochars. According to the results of this article, sawdust biochar has the best performance as an adsorbent and can be safely disposed of in building bricks at the end of its useful life.

Montmorillonite Clay as an Adsorbent for the Remediation of Cd (II) Ions in Aqueous Solutions: A Comparison With Pb (II) Ions

ABSTRACTHeavy metal ions are hazardous to both human health and the environment. Montmorillonite (MMT) clay has recently piqued interest for its adsorption capacity of heavy metals and its use in controlling contaminants, in particular in surface and waste waters. This research sheds light on the possibility of the application of natural Albanian MMT clay from the Prrenjas Region of Albania as an adsorbent of Cd (II) ions in aqueous solutions, making a comparison with the capacity of such clay for the adsorption of Pb (II) ions. The set of variables studied included concentrations of metal ions, amount of clay pH, time, and temperature of interaction and adsorption process (all of them following batch technique), and optimal conditions have been determined. The adsorption capacity of natural clay for Cd (II) ions was 6.735 mg/g, as compared to 17.9 mg/g for Pb (II) ions. Langmuir and Freundlich isotherms were applied to evaluate the mode of adsorption with results showing that all isotherms are linear and the Langmuir model fitted better with the experimental data. It is determined that the adsorption of Cd (II), similar to that of Pb (II), is well‐fitted by the second‐order reaction kinetic following the Lagergen model. The results demonstrate good potentiality for Prrenjas MMT as a low‐cost adsorbent to remove Cd (II) from aqueous systems, in particular, for wastewater treatment.

Cd(II) and Zn(II) adsorption on lignite‐derived humic substances and cattle manure biochar

AbstractExcessive industrial release of trace elements may pose a great risk to the environment. Conventional remediation treatments have considerable limitations, making less expensive new technologies an important research area. Batch experiments were conducted at room temperature to investigate the use of two lignite‐derived humic products (nano‐humus and humic powder) and a cattle manure biochar as adsorbents in the removal of cadmium and zinc from laboratory synthesized water. Nano‐humus was most effective in adsorbing Cd(II), wherein 89% adsorption was rapidly achieved in 15 min. The adsorbed amount of Cd(II) and Zn(II) both increased with initial metal ion concentrations from 25 to 125 mg L−1. Despite being produced from the same sources, nano‐humus and humic powder showed different properties and adsorption behaviors. The adsorption mechanism of nano‐humus followed the Freundlich isotherm model and pseudo‐second‐order kinetic model, indicating multilayer chemisorption. Humic powder followed the pseudo‐second‐order kinetic model, although it had a low isotherm model fit, implying chemisorption‐dominated adsorption. Cattle manure biochar followed the Freundlich isotherm and pseudo‐first‐order kinetics model, suggesting diffusion‐dominated multilayer adsorption. Of the three adsorbents tested, nano‐humus had greatest potential as an effective and inexpensive material for metal remediation.