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This research delved into the effects of nutrient limitation on the level of sporulation and the cadmium adsorption capacity of the bacterium Bacillus sp. isolated from the rhizosphere of endemic soils in the Region of Valparaiso, Chile. The bacteria were subjected to nitrogen limitation in fed-batch mode and were compared to bacteria grown in batch culture without nutrient limitation. The cultures were carried out in a 3 L bioreactor with an external nitrogen supply of ammonium at a flow of 0.123 L h−1. The specific maximum growth rate was 0.42 h−1 in batch and 0.45 h−1 in the exponential phase of the fed-batch. The analysis of sporulation did not show any significant difference between the biomass coming from the fed-batch and batch cultures. It was found that maximum cadmium adsorption capacity varied with culture strategy. The dry biomass grown without nutrient limitation exhibited a maximum adsorption capacity for cadmium of 65.0 mg Cd g−1 biomass. Conversely, the limited biomass achieved a lower cadmium adsorption capacity of approximately 36.0 mg Cd g−1 biomass. FTIR analysis showed that nitrogen limitation induced changes in the composition of the outer cell wall, specifically an increase of deacetlylated polysaccharides, reducing the relative amount of secondary amines and proteins from the peptidoglycan matrix. Amino groups from acetylated polysaccharides and proteins have been associated elsewhere with greater cadmium affinity, which could explain the poor results obtained with the nitrogen-restricted biomass. This study shows that new physiological states displaying different adsorption capabilities were effectively obtained by engineering the cell coverage of the bacteria using varying culture strategies. The fed-batch culture proved to be a valuable tool for studying PGPR strains for biosorption and other applications. Exploring diverse nutrient limitations and other pollutants in this bacterium and other members of the PGPR family offer great opportunities to tailor biosorption strategies based on specific conditions, ultimately contributing to sustainable environmental solutions. [Display omitted] • Fed batch culture. • Promoting Growth Plant Rhizobacteria (PGPR). • Nutrient availability. • Adsorption characteristics. • FTIR analysis. [ABSTRACT FROM AUTHOR]

• A novel olivine-magnesite composite material for removal of heavy metals was prepared by simply ball-milling. • Interface interaction of Mg 2 SiO 4 /MgCO 3 facilitated the formation of CdCO 3. • Significant fixation of Cd2+ was achieved even under weakly acidic conditions (pH=4). In this study, an efficient stabilizer material for cadmium (Cd2+) treatment was successfully prepared by simply co-milling olivine with magnesite. Several analytical methods including XRD, TEM, SEM and FTIR, combined with theoretical calculations (DFT), were used to investigate mechanochemical interfacial reaction between two minerals, and the reaction mechanism of Cd removal, with ion exchange between Cd2+ and Mg2+ as the main pathway. A fixation capacity of Cd2+ as high as 270.61 mg/g, much higher than that of the pristine minerals and even the individual/physical mixture of milled olivine and magnesite, has been obtained at optimized conditions, with a neutral pH value of the solution after treatment to allow its direct discharge. The as-proposed Mg-based stabilizer with various advantages such as cost benefits, green feature etc., will boosts the utilization efficiency of natural minerals over the elaborately prepared adsorbents. [Display omitted] [ABSTRACT FROM AUTHOR]

The release of cadmium into the environment is a significant global concern due to its toxicity, non-biodegradability, and persistence in nature. There is an urgent need for effective, eco-friendly, and cost-effective systems for removing Cd because of the many drawbacks of conventional physicochemical techniques. This study investigated the ability of the extremophile red microalgal strain Galdieria sulphuraria CCMEE 5587.1 to tolerate and remove Cd (II) ions at acidic pH in a controlled laboratory environment. Three distinct concentrations of Cd (1.5 mg L−1, 3 mg L−1, and 6 mg L−1) were introduced to the cyanidium medium, and G. sulphuraria cells were introduced in the medium and grown for ten days. Four distinct aspects were identified regarding Cd removal: time course Cd removal, total Cd removal, extracellular Cd removal, and intracellular Cd removal. The inhibitory effects of Cd on G. sulphuraria growth were observed using a daily growth profile. Initial incubation days showed an inhibition of G. sulphuraria growth. In addition, increasing the Cd concentration in the medium decreased the growth rate of G. sulphuraria. Rapid Cd removal occurred on the first day of the experiment, followed by a steady removal of Cd until the last day. The highest total removal efficiency occurred in a medium containing 3 mg L−1 of Cd ions, which was 30%. In contrast, the highest sorption capacity occurred in a medium containing 6 mg L−1 of Cd ions, which was 1.59 mg g−1 of dry biomass. In all media compositions, a major fraction (>80%) of Cd removal occurred via adsorption on the cell surface (extracellular). These results showed that G. sulphuraria cells can remove Cd ions from aqueous solution, which makes them a potential bioremediation option for heavy metal removal. [ABSTRACT FROM AUTHOR]

AbstractThis study investigates the equilibrium and kinetics of copper and cadmium adsorption from aqueous solutions using groundnut husk. Characterization of the groundnut husk reveals various functional groups and a porous morphology. Isothermal studies were conducted, and different models were evaluated to fit the data. The Langmuir model exhibits the best fit for copper adsorption, while the Temkin and Dubinin–Radushkevich (DR) isotherm models show superior fitting for cadmium adsorption. Results suggest that physisorption significantly influences both cases, with mean sorption adsorption energy lower than 8000 J/mole. Error analysis reveals that the Freundlich and Temkin models demonstrate maximum adsorption capacity, with lower Chi-square (ꭓ2), Sum of Square Errors (SSE), and SAE compared to Langmuir and DR models. Additionally, intra-particle diffusion was analyzed using the Weber and Morris equation. Evaluation of model parameters indicates that cadmium demonstrates better nonlinear fitting of data compared to copper. FTIR and SEM analysis confirm the involvement of various functional groups in adsorption and reveal changes in surface distribution post-adsorption due to copper and cadmium presence. [ABSTRACT FROM AUTHOR]

Cadmium (Cd2+) pollution in soil and water bodies is a significant environmental concern, necessitating effective remediation strategies. Traditional methods often fall short in efficiency, cost-effectiveness, and environmental sustainability. This study develops and evaluates the effectiveness of chitosan–gelatin–hydroxypropyl methylcellulose (CS-GEL-HPMC) membranes for Cd2+ removal from polluted environments. CS-GEL-HPMC membranes were synthesized with varying HPMC concentrations. Their structural and morphological characteristics were analyzed using UV–visible absorption spectroscopy and FT-IR. The membranes' stability across different pH levels and their morphological traits were assessed. The adsorption efficiency for Cd2+ ions was evaluated in both aqueous solutions and soil environments under varying conditions of pH, initial ion concentration, and contact time. The CS-GEL-HPMC membranes demonstrated significant structural integrity and stability, especially at higher HPMC concentrations. UV–visible and FT-IR analyses confirmed the successful integration of HPMC into the CS-GEL matrix. In aqueous solutions, the membranes exhibited efficient Cd2+ adsorption, with the best performance observed for the CS30-GEL30-HPMC40 membrane. The adsorption capacity was influenced by contact time, initial Cd2+ concentration, and pH. In soil treatments, the membranes effectively reduced Cd2+ concentrations, with higher membrane dosages yielding better results. The incorporation of additives like (hydroxyapatite) HAP, fly ash (FA), and cement further enhanced the remediation efficiency. In summary, CS-GEL-HPMC membranes, particularly when combined with additives, emerge as a promising, sustainable solution for Cd2+ remediation in both soil and water bodies. This study highlights the potential of biopolymer-based composites in environmental clean-up efforts, offering a novel approach that is both effective and eco-friendly. [ABSTRACT FROM AUTHOR]

Water pollution caused by heavy metals is a major environmental problem, threatening water production, food safety, and human health. Cadmium (Cd) pollution is particularly serious because of food-chain biomagnification at toxic concentrations. Modified biochar is promising for heavy metal removal; however, efficient adsorbents for Cd removal are lacking. In the present study, a novel adsorbent, silica gel-modified biochar (SGB), was prepared and applied to treat sewage polluted by Cd. Through the batch adsorption experiments, it is known that SGB possessed outstanding Cd removal ability and recycleability. Furthermore, the adsorption behavior and mechanisms were analyzed by the application of kinetic and isotherm models. The maximum Cd2+ adsorption capacity of SGB was 38.08 mg g−1, and after five recycling processes, the Cd2+ removal rate was still 86.89 %. When the pH of the solution was 7.0, SGB showed the strongest Cd2+ adsorption capacity (29.06 mg g−1). When competitive ions existed, biochar also had high Cd removal efficiency, although the effect of Pb2+ was greater than those of Cu2+ and Zn2+, indicating that SGB was applicable to complex polluted water. Additionally, the main Cd2+ adsorption mechanisms by SGB were electrostatic interactions, π-π interactions, complexation, and co-precipitation. These results showed that SGB can effectively treat Cd-contaminated wastewater as a new adsorbent.

Biochar (BC) boasts diverse environmental applications. However, its potential for environmental biomonitoring has, surprisingly, remained largely unexplored. This study presents a preliminary analysis of BC's potential as a biomonitor for the environmental availability of ionic Cd, utilizing the lichen Evernia prunastri (L.) Ach. as a reference organism. For this purpose, the lichen E. prunastri and two types of wood-derived biochar, biochar 1 (BC1) and biochar 2 (BC2), obtained from two anonymous producers, were investigated for their ability to accumulate, or sequester and subsequently release, Cd when exposed to Cd-depleted conditions. Samples of lichen and biochar (fractions between 2 and 4 mm) were soaked for 1 h in a solution containing deionized water (control), 10 µM, and 100 µM Cd2+ (accumulation phase). Then, 50% of the treated samples were soaked for 24 h in deionized water (depuration phase). The lichen showed a very good ability to adsorb ionic Cd, higher than the two biochar samples (more than 46.5%), and a weak ability to release the metal (ca. 6%). As compared to the lichen, BC2 showed a lower capacity for Cd accumulation (−48%) and release (ca. 3%). BC1, on the other hand, showed a slightly higher Cd accumulation capacity than BC2 (+3.6%), but a release capacity similar to that of the lichen (ca. 5%). The surface area and the cation exchange capacity of the organism and the tested materials seem to play a key role in their ability to accumulate and sequester Cd, respectively. This study suggests the potential use of BC as a (bio)monitor for the presence of PTEs in atmospheric depositions and, perhaps, water bodies. [ABSTRACT FROM AUTHOR]

The release of cadmium into the environment is a significant global concern due to its toxicity, non-biodegradability, and persistence in nature. There is an urgent need for effective, eco-friendly, and cost-effective systems for removing Cd because of the many drawbacks of conventional physicochemical techniques. This study investigated the ability of the extremophile red microalgal strain Galdieria sulphuraria CCMEE 5587.1 to tolerate and remove Cd (II) ions at acidic pH in a controlled laboratory environment. Three distinct concentrations of Cd (1.5 mg L−1, 3 mg L−1, and 6 mg L−1) were introduced to the cyanidium medium, and G. sulphuraria cells were introduced in the medium and grown for ten days. Four distinct aspects were identified regarding Cd removal: time course Cd removal, total Cd removal, extracellular Cd removal, and intracellular Cd removal. The inhibitory effects of Cd on G. sulphuraria growth were observed using a daily growth profile. Initial incubation days showed an inhibition of G. sulphuraria growth. In addition, increasing the Cd concentration in the medium decreased the growth rate of G. sulphuraria. Rapid Cd removal occurred on the first day of the experiment, followed by a steady removal of Cd until the last day. The highest total removal efficiency occurred in a medium containing 3 mg L−1 of Cd ions, which was 30%. In contrast, the highest sorption capacity occurred in a medium containing 6 mg L−1 of Cd ions, which was 1.59 mg g−1 of dry biomass. In all media compositions, a major fraction (>80%) of Cd removal occurred via adsorption on the cell surface (extracellular). These results showed that G. sulphuraria cells can remove Cd ions from aqueous solution, which makes them a potential bioremediation option for heavy metal removal.

Indonesia, notably in Central Kalimantan, has the potential for raw zirconia mineral, but it has not been successfully developed as a material that has ecologically friendly, high economic and technical value. The magnetic nanoparticles coated zirconia mineral was synthesized by using one-pot solvothermal processes, and then was used as adsorbent for water and wastewater treatment in adsorption process. Zirconia minerals are turned into composites with magnetic nanoparticles with the addition of hexane diamine to create the composite with amino groups (MH@ZrO2). It was then utilized as adsorbent to adsorb lead and cadmium metal in an artificial solution, and lower the metal content of lead/ (Pb(II)) and cadmium (Cd(II)) in it. The first stage was to determine the equilibrium of contact time (30, 60, 120, 240, and 360 min) of the adsorbent in binding Pb(II) and Cd(II) ions. The variations of pH 3, 5, 7, and 9 in the solution during adsorption were also examined to establish appropriate conditions for the adsorption process. The observations of magnetic nanoparticles composites based on a Scanning Electron Microscopy (SEM) analysis showed that magnetic nanoparticles with the diameter of 30–50 nm were generated on the face of zirconia minerals. X-Ray Diffraction (X-RD) analysis revealed that zirconia minerals treatment lowered the Crystallinity Index by 11.19% and the silica content by 98%. A Fourier Transform Infra-Red (FT-IR) spectrometer showed an adsorption peak of 590 cm−1 for the Fe-O bond on Fe3O4. Meanwhile, the optimum condition for Pb(II) and Cd(II) adsorption with pHe around 7 ± 0.2 for 360 min resulted in an adsorption density of 117.67 mg/g and 24.19 mg/g, respectively. The MH@ZrO2 led to development for high potential adsorbent due to stable material and easy separation, and capable for absorbing Pb(II) and Cd(II) ions from an aqueous solution.

Presence of trace metal pollutants in the aquatic system is a worldwide foremost concern. The present investigation was an attempt to find out the novel biosorbent for the removal of Cadmium(CdII) from contaminated water. The leaf of Sesbania bispinosa was screened out as a potential Cd(II) removing biosorbent from thirty different natural biomasses by physico-chemical and sorption process characterizations. Biosorption capacity of S. bispinosa was determined by batch mode biosorption method with the functions of solution pH, contact time, biosorbent dose and initial Cd(II) concentration. Obtained results were analyzed for isotherm and kinetic study. The S. bispinosa biosorbent exhibited the biosorption equilibrium of Cd(II) uptake in 30 min. At pH 4, biosorbent dose of 1 g/L was sufficient for maximum Cd(II) uptake. Scanning Electron Microscopy (SEM) images and Fourier Transform Infrared Spectroscopy (FTIR) spectra confirmed the favourable sorption surface characteristics. The data also demonstrated that Freundlich isotherm (R2=0.998) is the better fitted model compared to Langmuir model and the maximum sorption capacity was found to be 33.33 mg/g. Suitabilty of pseudo second order reaction pathway was observed during the kinetic study. Most especially, The selected biosorbent is ascertained effective in removing multimetals [Cd(II) - 67.51 %, Cr(VI) – 40.36 %, Pb(II) – 100 % and Cu(II) – 59.01 %] from a quaternary aqueous solution of Cd(II), Cr(VI), Pb(II) and Cu(II) mixture and spent biosorbent can be easily regenerated by applying 0.1 M HCl solution as a desorbing agent. It, therefore, could be concluded that leaves of S.bispinosa might be a low-cost and environmentally sound novel biosorbent for the treatment of Cd(II) contaminated water.

Cadmium (Cd) is documented as one of the most lethal metals and poses a major threat to all life forms in the environment due to its toxic effects. Bioremediation of hazardous metals has received considerable and growing interest over the years. The functional fungi with tolerance to the heavy metal Cd were screened from the mining soil samples. Two fungi isolates from coal mine soil were characterized as Sarocladium sp. M2 and Sarocladium sp. M6 based on morphological and partial ITS sequencing analysis. M2 and M6 exhibited high levels of resistance to cadmium, and they were investigated for their micro-morphology and application in heavy metal removal with different concentration Cd(II) (0, 50, 100, 150 and 200 mg/L). The colony morphology of M2 and M6 gradually become very similar to that of bacteria with the increase of cadmium concentration (150–200 mg/L). Micro-morphological studies showed that Cd(II) exposure caused the disappearance of conidial heads and the occurrence of hyphae breakage (100–200 mg/L Cd(II), which is consistent to the colony morphology results. The surface/volume ratio of the spores decreased with the presence of Cd(II). The removal potential of fungi for cadmium was quantified by atomic absorption spectrometry. M2 and M6 showed great potential as bioremediators for highly Cd(II)-contaminated environment. The highest Cd(II) biosorption capacity was 5.13 ± 0.21 mg/g for M2 and 6.04 ± 0.21 mg/g for M6. The highest heavy metal sorption by M2 removed 57.11% ± 4.45% Cd(II) while that of M6 removed 48.35% ± 1.44% Cd(II) in 200 mg/L initial concentration Cd(II). To the best of our knowledge, this is the first report that cadmium induced the change of reproduction mode of the Sarocladium, from conidia to arthrospores, which made the colony morphological modifications, from the fungi colony morphology to the bacteria colony morphology. The arthrospore-modified (hyphae breakage) seemed to accumulate greater amounts of heavy metals than filamentous hyphae formation.

Sorptive removal of cadmium (Cd) from the aqueous solutions using the easily available natural materials is an attractive method. However, the adsorption efficiencies of these materials, such as clays, are typically low. Besides, they are generally in relatively low stability and renewability, which restrict their application. Thus, modification of these materials to enhance their performance on Cd removal has gained growing attentions. Herein, the integration of calcination and ferric chloride (FeCl3) was used to modify a typical clay, i.e., attapulgite, to increase the adsorption sites, and thus to develop a robust adsorbent for Cd. Under the optimum conditions for attapulgite modification (i.e., the mass ratio of FeCl3 to attapulgite was 1:2, calcination temperature was 350 °C, and calcination time was 1.5 h) and Cd adsorption (i.e., initial pH of 6.0, adsorption temperature of 25 °C, and adsorbent dosage of 1.0 g/L), the maximum adsorption capacity of the modified attapulgite toward Cd was 149.9 mg/g. Mechanisms of surface complexation and electrostatic attraction were involved in the efficient removal of Cd. The adsorption of Cd increased with pH due to the increased electrostatic attraction. Metal cations inhibited the Cd adsorption through competing with the adsorption sites. The changes of Gibbs-free energy during the adsorption of Cd were lower than zero and decreased with temperature, suggesting the process was spontaneous and endothermic. The removal efficiency of Cd after 5 times of recycle maintained at 82% of that of the raw modified attapulgite demonstrated the stability of the adsorbent. These results suggested that the modified attapulgite is robust for Cd removal and is promising for land application. [ABSTRACT FROM AUTHOR]

Heavy metal contamination in water resources is a major issue worldwide. Metals released into the environment endanger human health, owing to their persistence and absorption into the food chain. Cadmium is a highly toxic heavy metal, which causes severe health hazards in human beings as well as in animals. To overcome the issue, current research focused on cadmium ion removal from the polluted water by using porous magnetic chitosan composite produced from Kaphal (Myrica esculenta) leaves. The synthesized composite was characterized by BET, XRD, FT-IR, FE-SEM with EDX, and VSM to understand the structural, textural, surface functional, morphological-compositional, and magnetic properties, respectively, that contributed to the adsorption of Cd. The maximum Cd adsorption capacities observed for the Fe3O4 nanoparticles (MNPs) and porous magnetic chitosan (MCS) composite were 290 mg/g and 426 mg/g, respectively. Both the adsorption processes followed second-order kinetics. Batch adsorption studies were carried out to understand the optimum conditions for the fast adsorption process. Both the adsorbents could be regenerated for up to seven cycles without appreciable loss in adsorption capacity. The porous magnetic chitosan composite showed improved adsorption compared to MNPs. The mechanism for cadmium ion adsorption by MNPs and MCS has been postulated. Magnetic-modified chitosan-based composites that exhibit high adsorption efficiency, regeneration, and easy separation from a solution have broad development prospects in various industrial sewage and wastewater treatment fields. [ABSTRACT FROM AUTHOR]

The practical use of HKUST-1, a commercially accessible material with significant capability in adsorption-based separation, is hindered by its vulnerability to water. In the current study, we proposed a method to prepare NH2-SiO2@HKUST-1 with improved water stability and enhanced performance for cadmium removal from the water environment. FTIR, XRD, SEM, EDS, and BET studies showed that NH2-SiO2 nanoparticles were successfully immobilized on HKUST-1, totally inhibiting moisture-induced performance degeneration of NH2-SiO2@HKUST-1 for cadmium removal from water. While HKUST-1 exhibited a cadmium adsorption capacity of 38.6 mg/g, NH2-SiO2@HKUST-1 demonstrated 8.4-fold better performance, a high cadmium removal capacity of 324.9 mg/g, under optimal process conditions obtained using Response Surface Methodology. The water stability tests revealed that whereas HKUST-1 lost its crystallinity and capacity for cadmium adsorption after six days of exposure to water,NH2-SiO2@HKUST-1 preserved its crystalline structure and 86% of its original cadmium removal capacity. Thermodynamic analysis revealed that the adsorption of cadmium onto NH2-SiO2@HKUST-1 occurred spontaneously and that physical adsorption was the main mechanism during the process. Langmuir isotherm successfully described cadmium adsorption onto NH2-SiO2@HKUST-1. Cadmium adsorption onto NH2-SiO2@HKUST-1 reached equilibrium remarkably fast after 10 min, and the pseudo-second-order model showed that this model best describes the kinetic data. [ABSTRACT FROM AUTHOR]

The increasing generation of wastewater with high levels of pollutants has become a serious environmental challenge. In this context, sustainable technologies are required to treat wastewater efficiently. Therefore, it was proposed to evaluate the effect of the biomass of Chlorella sp. on the removal of cadmium and chemical oxygen demand (COD) from municipal wastewater in the district of Urpay, Pataz, La Libertad, Peru, and the generation of electric power through single-chamber microbial fuel cells (MFC). An experimental design was applied, where nine treatments were carried out evaluating three doses of Chlorella sp. (10%, 20% and 30%) at pH values of 6.5, 7.0, and 7.5 of the residual water. Managing to generate peak current and voltage values of 4.61 mA and 1118.5 mV in the MFC at a pH of 7.5 with a dose of 30% of Chlorella sp., this same MFC managed to decrease concentrations of cadmium and COD by 97.5 and 15% in 25 and 15 days, respectively. This investigation demonstrated the importance of Chlorella sp. for the reduction in these two parameters, managing to provide a new method for the elimination of these pollutants in wastewater. [ABSTRACT FROM AUTHOR]

Cadmium is one of the most toxic heavy metal ions found in wastewaters and its remedial methods are globally investigated. Removal methods based on biomaterials as adsorbents are proving to be simple, effective and eco-friendly. In the present investigation, bio-adsorbents derived from Cochlospermum regium plant stems (CRSP) and its active carbon (CRAC) are observed to have good adsorption for toxic cadmium ions. Hence, extraction conditions are optimized for maximum Cd-extraction: 55.0% with 'CRSP' and 70.0% with 'CRAC', from Cd2+ solutions of concentration: 25.0 mg/L. The adsorption capacities are 6.9 mg/g with CRSP and 12.6 mg/g with 'CRAC'. When 'CRAC' is impregnated with nano-CeO2 (CRAC.nCeO2) and is used as adsorbent, the percentage of Cd-extraction is increased to 90.0% and adsorption capacity to 22.5 mg/g at the optimized extraction conditions. To overcome the agglomeration of nanoparticles, the 'CRAC.nCeO2' is immobilized in Zr-alginate beads and thus obtained beads are investigated as adsorbent. With beads (CRAC.nCeO2–Zr.alg), the percentage of Cd-adsorption is enhanced to 95.0% and adsorption capacity to 24.6 mg/g. The adsorbents are characterized by adopting XRD and FTIR techniques. The adsorption mechanism is assessed by evaluating thermodynamic parameters, isotherm and kinetic models. The thermodynamic parameters and FTIR spectral characteristics indicate the formation of 'surface complex' between Cd2+ and adsorbent's functional groups. The adsorption follows Freundlich isotherm and pseudo-second order model. Many co-ions have not effected the percentage of extraction and interestingly, the presence of some cations (Al3+ and Fe3+) have synergistically enhanced the Cd-extraction. Spent sorbents can be regenerated and reused with marginal loss of adsorption capacity. The adsorbents developed are successfully used to treat real Cd-polluted wastewater. The novelty of the present investigation is that the effective, eco-friendly, renewable and robust sorbents with high sorption capacities are developed for Cd-remediation of water. The merit of the present investigation is that adsorbents with high sorption capacities, are developed based on bio materials of Cochlospermum regium and nano-CeO2. Zirconium alginate beads doped with nano-CeO2 and active carbon of Cochlospermum regium stems, are found to be highly effective for Cd-removal and spent adsorbent can be regenerated and re-used for five cycles. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) accumulation in rice protein has long been considered a significant threat to human health. In the present study, a costless and effective method based on gluconic acid (GA) rinsing of rice protein was developed to reduce Cd contamination in rice protein. Moreover, the effect of GA on the structural and functional properties of rice protein was evaluated. With liquid–solid ratio of 30 mL/g and oscillation time of 120 min, 96.0% and 93.6% of Cd were eliminated from rice protein‐H and rice protein‐L, respectively. In addition, the results of scanning electron microscopy, Fourier transform infrared, and sodium dodecyl sulfate polyacrylamide gel electrophoresis analyses showed that GA treatment did not significantly change the structural properties of rice protein. However, GA treatment increased foaming properties, water holding capacity, and oil holding capacity of the rice protein, without affecting its further applicability. Thus, the proposed GA rinsing method can be considered a green and efficient strategy to solve the issue brought by Cd residual contamination in rice protein. Practical Application: Given the advantages of green and efficient agriculture, gluconic acid (GA) has emerged as a powerful strategy for removing the Cd from rice protein. The method developed herein showed great potentials for applications in the manufacture of rice‐based products. [ABSTRACT FROM AUTHOR]

Designing an efficient and recyclable adsorbent for cadmium pollution control is an urgent necessity. In this paper, cow manure, an abundant agricultural/animal husbandry byproduct, was employed as the raw material for the synthesis of magnetic cow manure biochar. The optimal preparation conditions were found using the response surface methodology model: 160 °C for the hydrothermal temperature, 600 °C for the pyrolysis temperature, and Fe-loading with 10 wt%. The optimal reaction conditions were also identified via the response surface methodology model: a dosage of 1 g·L−1, a pH of 7, and an initial concentration of 100 mg·L−1. The pseudo-second-order model and the Langmuir model were used to fit the Cd(II) adsorption, and the adsorption capacity was 612.43 mg·g−1. The adsorption was dominated by chemisorption with the mechanisms of ion-exchange, electrostatic attraction, pore-filling, co-precipitation, and the formation of complexations. Compared to the response surface methodology model, the back-propagation artificial neural network model fit the Cd(II) adsorption better as the error values were less. All these results demonstrate the potential application of CM for Cd(II) removal and its optimization through machine-learning processes. [ABSTRACT FROM AUTHOR]

The adsorption mechanisms of Cd2+ removal from synthetic water using blended biochar from bamboo sawdust (BSD) and rice husk (RH) feedstocks at BSD/RH ratios 1:1, 1:3, and 3:1 were investigated. The equilibrium isotherms (Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich) and kinetics (pseudo-first order, pseudo-second order, Elovich, and intra-particle diffusion kinetic adsorption models) and thermodynamics were examined. The BSD/RH biochar ratio of 1:1, 1:3, and 3:1 produced the Cd2+ removal of 99.2%, 98.3%, and 97.24% respectively. The adsorption investigation found insignificant differences in removal efficiency across the biochar ratio combinations. Furthermore, the equilibrium isotherm analyses for the BSD/RH ratio of 3:1 and 1:1 are best described by in favor of the Freundlich model, whereas for BSD/RH biochar ratio of 1:3 best matched the Langmuir model. The thermodynamic study revealed that the process is non-spontaneous, endothermic, and dominated by the physisorption mechanism. Generally, physisorption was discovered to be the dominant process controlling the Cd2+ removal from the solution. [ABSTRACT FROM AUTHOR]

The sulfidation of nanoscale zerovalent iron (nZVI) has received increasing attention for reducing the oxidizability of nZVI and improving its reactivity toward heavy metal ions. Here, a sulfide (S)-modified attapulgite (ATP)-supported nanoscale nZVI composite (S-nZVI@ATP) was rapidly synthesized under acidic conditions and used to alleviate Cd2+ toxicity from an aqueous solution. The degree of oxidation of S-nZVI@ATP was less than that of nZVI@ATP, indicating that the sulfide modification significantly reduced the oxidation of nZVI. The optimal loading ratio was at an S-to-Fe molar ratio of 0.75, and the adsorption performance of S-nZVI@ATP for Cd2+ was significantly improved compared with that of nZVI@ATP. The removal of Cd2+ by S-nZVI@ATP was 100% when the adsorbent addition was 1 g/L, the solution was 30 mL, and the adsorption was performed at 25 °C for 24 h with an initial Cd2+ concentration of 100 mg/L. Kinetics studies showed that the adsorption process of Cd followed the pseudo-second-order model, indicating that chemisorption was the dominant adsorption mechanism. The adsorption of Cd2+ by S-nZVI @ATP is dominated by the complexation between the iron oxide or iron hydroxide shell of S-nZVI and Cd2+ and the formation of Cd(OH)2 and CdS precipitates. HIGHLIGHTS S-nZVI was loaded on ATP, effectively preventing nZVI agglomeration, and the sulfide modification significantly reduced the oxidation of nZVI.; Cd2+ removal was mailly attributed to complex with the iron oxides or iron hydroxide shell of S-nZVI.; S-nZVI@ATP showed a stable adsorption effect on Cd2+ over a wide pH range.; The removal of Cd2+ by S-nZVI@ATP follows the quasi-second-order kinetic adsorption model.;

Composite copper–ceria-based adsorbent prepared by different sol–gel and co-precipitation methods and their performances were examined for cadmium removal from aqueous solution. Cadmium as a pollutant in drinking water is a severe problem that has negative health effects on humans. In the present study, the prepared adsorbents were characterized using a particle size analyzer, BET surface area, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analysis. TEM analysis revealed the presence of approximately hexagonal-shaped copper oxide ceria with size ranging from 15 to 20 nm and having an average size distribution of 15.45 nm for sol–gel and 16.79 nm for co-precipitation prepared adsorbents. Synthesized adsorbents obtained using the sol–gel method showed better cadmium removal than those obtained using co-precipitation methods. Adsorption data of adsorption isotherm and kinetic models were analyzed. Cadmium's adsorption was more rapid in the sol–gel copper oxide ceria adsorbent compared to the co-precipitation copper oxide ceria adsorbent. Equilibrium was attained quickly because of the higher surface area of CuO/CeO2 prepared by the sol–gel method. The equilibrium adsorption capability of sol–gel copper oxide ceria was more than 93%, while the co-precipitation copper oxide ceria's equilibrium adsorption capability was approximately 89%. The prepared copper–ceria composite adsorbents showed good performance toward cadmium removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

Biochar (BC) boasts diverse environmental applications. However, its potential for environmental biomonitoring has, surprisingly, remained largely unexplored. This study presents a preliminary analysis of BC’s potential as a biomonitor for the environmental availability of ionic Cd, utilizing the lichen Evernia prunastri (L.) Ach. as a reference organism. For this purpose, the lichen E. prunastri and two types of wood-derived biochar, biochar 1 (BC1) and biochar 2 (BC2), obtained from two anonymous producers, were investigated for their ability to accumulate, or sequester and subsequently release, Cd when exposed to Cd-depleted conditions. Samples of lichen and biochar (fractions between 2 and 4 mm) were soaked for 1 h in a solution containing deionized water (control), 10 µM, and 100 µM Cd2+ (accumulation phase). Then, 50% of the treated samples were soaked for 24 h in deionized water (depuration phase). The lichen showed a very good ability to adsorb ionic Cd, higher than the two biochar samples (more than 46.5%), and a weak ability to release the metal (ca. 6%). As compared to the lichen, BC2 showed a lower capacity for Cd accumulation (−48%) and release (ca. 3%). BC1, on the other hand, showed a slightly higher Cd accumulation capacity than BC2 (+3.6%), but a release capacity similar to that of the lichen (ca. 5%). The surface area and the cation exchange capacity of the organism and the tested materials seem to play a key role in their ability to accumulate and sequester Cd, respectively. This study suggests the potential use of BC as a (bio)monitor for the presence of PTEs in atmospheric depositions and, perhaps, water bodies.

Investigating the effect of presoaking, as one of the most important physical factors affecting the adsorption behavior of biochar, on the adsorption of heavy metals by modified or non-modified biochar and presoaking mechanism is still an open issue. In this study, the water presoaking effect on the kinetics of cadmium (Cd) adsorption by rice husk biochar (produced at 450 °C, B1, and at 600 °C, B2) and the rice husk biochar modified with magnesium chloride (B1 modified with MgCl2, MB1, and B2 modified with MgCl2, MB2) was investigated. Furthermore, the effect of pH (2, 5, and 6), temperature (15, 25, and 35 °C), and biochar particle size (100 and 500 µm) on the kinetics of Cd adsorption was also investigated. Results revealed that the content of Cd adsorbed by the presoaked biochar was significantly higher than that by the non-presoaked biochar. The highest Cd adsorption capacity of MB2 and MB1 was 98.4 and 97.6 mg g−1, respectively, which was much better than that of B1 (7.6 mg g−1) and B2 (7.5 mg g−1). The modeling of kinetics results showed that in all cases pseudo-second-order model was well-fitted (R2>0.99) with Cd adsorption data. The results also indicated that the highest Cd adsorption values were observed at pH 6 in presoaked MB1 with size of 100 µm as well as at the temperature of 35 °C in presoaked MB2, indicating the optimum conditions for this process. The presoaking process was not affected by biochar size and pH, and the difference in adsorbed Cd content between presoaked biochars and non-presoaked ones was also similar. However, the temperature had a negative effect on presoaking. The presoaking process decreased micropores (

In this study, Si Mg doped industrial lignin-based carbon materials (SLCs) were prepared by water bath silicification and MgCl 2 activation to remove Cd2+ from aqueous solutions. What's more, the doping of Si Mg jointly promoted the excellent physicochemical properties of the material, e.g., high specific surface area, good pore volume, and numerous oxygen-containing groups. The Cd2+ batch adsorption experiments proved that SLCs have good Cd2+ removal capacity within pH 3–7, and the adsorption model demonstrated the adsorption process as a physicochemically complex process. The maximum adsorption of Cd2+ in the SLC was 665.35 mg/g, and the contributing factors to the removal of Cd2+ were as follows: ion exchange (59.36 %) > Cd2+ precipitation (24.93 %) > oxygen-containing functional group complexation (14.79 %) > Cd2+–π interactions (0.92 %). In addition, the complexation of Si O, Mg O, and Cd precipitates allowed the formation of a three-dimensional fiber mesh structure. The application of SLCs has the potential to eliminate Cd2+ pollution in water bodies, and its preparation is simple and environmentally friendly. Finally, this study provides a theoretical basis for an in-depth understanding of the mechanism of heavy metal adsorption by inorganic nonmetals in combination with metal oxides. [ABSTRACT FROM AUTHOR]

This study introduces a highly efficient tripolyphosphate -tethered cellulose sorbent for cadmium (Cd2⁺) removal from aqueous solutions. Characterization through FTIR and SEM revealed the material's structural properties. The sorbent achieved 99% Cd2⁺ removal even at a minimal dosage of 0.05 g. Optimal sorption occurred within the pH range of 4–6, influenced by the sorbent's weak acidic functional groups. Rapid kinetics, reaching equilibrium within a minute, and a high sorption capacity (up to 18.03 mg/g at 50 °C) were observed. Langmuir isotherm modeling confirmed monolayer sorption, and thermodynamic studies indicated a spontaneous, endothermic process with increased randomness at the solid-liquid interface. Selectivity studies demonstrated strong Cd2⁺ removal performance in the presence of competing ions, with minimal interference from monovalent ions but notable effects from divalent ions. The sorbent exhibited consistent reusability over multiple cycles. XPS analysis conclusively established an ion exchange mechanism between Cd2⁺ and negatively charged P 3 O 10 5− groups as the primary removal pathway. This research highlights the potential of TPP-tethered cellulose as a promising sorbent for effective Cd2⁺ remediation. [Display omitted] • Novel TPP-tethered cellulose sorbent for efficient Cd2⁺ removal. • Rapid kinetic, achieving equilibrium within a minute. • Effective Cd2⁺ removal in the presence of competing ions. • Regenerable sorbent for sustainable Cd2⁺ remediation. [ABSTRACT FROM AUTHOR]

Despite advancements in wastewater treatment technologies, heavy metal contamination, especially cadmium (Cd), severely threatens human health and ecosystems. The purpose of this work is to compare the removal of Cd (II) ions from aqueous solutions by chemically modified mixed seaweed biosorbent (CMSB) and physically modified mixed seaweed biosorbent (PMSB). BET, SEM, EDAX, FTIR, and XRD techniques characterized the mixed seaweed biosorbents before and after adsorption. They are well-known for their sustainability, affordability, and biodegradability. The BET study revealed that CMSB had a surface area of 19.682 m2/g, while PMSB had a lower surface area of 14.803 m2/g. The optimum adsorption conditions were a temperature of 303 K, pH of 6.0, and biosorbent dosages of 1 g/L for CMSB and 2.5 g/L for PMSB. For CMSB and PMSB, the most efficient contact times were 40 and 80 min, respectively. The Langmuir model was demonstrated to be the best fit for the experimental data when compared to other isotherm models, with a coefficient of determination, or R2, of 0.9713 and a maximum monolayer capacity of 151.2 mg/g and 181.6 mg/g for physical and chemical activated mixed seaweed biomass. There was a significant relationship between the R2 values of chemically modified and physically modified biomass. The findings demonstrate that pseudo-second-order kinetics more accurately represent the adsorption process than pseudo-first-order and Elovich models. Thermodynamic experiments validated the endothermic, spontaneous and favourable characteristics of the removal process. According to the results of the current study, PMSB and CMSB may be used as effective adsorbents to remove Cd (II) from aqueous solutions. [Display omitted] • Utilizing PMSB and CMSB, the adsorption of Cd (II) ion was investigated. • Maximum Cd (II) ion adsorption capacity of 181.6 mg/g was observed with CMSB. • Fits with Pseudo-second-order kinetics and the Langmuir adsorption isotherm. • Chemically modified mixed seaweed is an effective adsorbent. [ABSTRACT FROM AUTHOR]

This project studied Cd(II) uptake from phenols-bearing wastewater using magnetic carbon nanotubes (MCNT) as adsorbent. Initially, Cd(II) complexation with various phenols was confirmed by FT-IR spectroscopy. Factors affecting Cd removal are: solution pH; type of phenol [phenol (Ph), 2-chlorophenol (2-CP), 2-nitrophenol (2-NP), and 2,4-dinitrophenol (2,4-DNP)]; Mag:CNT mass ratio; Cd:phenolic compound molar ratio; and the effect of order of adding adsorption components (MCNT, Cd(II), phenolic compound) to the extraction medium. It was found that the presence of phenols in the extraction medium caused a 10–50% decrease in Cd(II) uptake. This was probably due to a competition between phenols/surface functional groups towards Cd(II); or phenols/Cd(II) to occupy the surface functional groups. 2,4-DNP was selected as a model phenolic compound. The optimum adsorption conditions [1:1 M ratio of (Cd(II):2,4-DNP) at pH 6 using MCNT(1:1) adsorbent] resulted in adsorption capacity of 17.9 mg Cd g−1. The best order of adding reagents was (Cd(II) + MCNT(1:1)) and then 2,4-DNP. The regeneration of the adsorbent was possible by using 0.5 M HNO3 where 90% of adsorption efficiency was reserved after three times of successive use. Upon presence of co-existing ions, 75% of the adsorption efficiency was maintained. The applicability of the proposed adsorption method on real water samples was evaluated.

The present work studies the efficiency of new innovative quaternized polysulfone (PSFQ)/ionic liquid (IL) membranes in the treatment process of water containing cadmium ions (Cd(II)). The design and development of the polysulfone membranes with morphology tailored by the use of ILs (Cyphos 101 IL and Aliquat 336) was based on the rheological study of the casting solutions that dictated the optimal compositions of ILs and facilitated the preparation of the membranes for performance tests. Thus, according to the variation of the rheological functions obtained (G′, G″), it was demonstrated that Aliquat 336 has better compatibility with PSFQ, facilitating the workability of the solution and improving the final properties of the membranes relative to Cyphos 101 IL. However, the casting solutions consisting of 5 wt.% Ph-IL and 15 wt.% Am-IL content produce membranes with superior physico-chemical properties. Also, the surface chemistry and morphology analysis of the membranes obtained were investigated in order to understand the relationship between the PSFQ and ILs, as well as their surface properties, as indicators for their future applications. Additionally, the results obtained from the kinetic studies regarding Cd(II) removal from aqueous solutions and the amount of Cd(II) accumulated onto the membranes showed that the ILs enhance the filtration efficiency of the membranes studied and underlined the positive effect of IL in the structure of the quaternized polysulfone membranes. A content of 15 wt.% Aliquat 336 in PSFQ membranes shows the best properties for Cd(II) removal from aqueous solutions; the maximum amount of Cd(II) accumulated on the membrane studied was 3300 mg/m2. This behaviour was maintained for two cycles of washing/filtration, and then the efficiency decreased by 20%. The results obtained showed that the membranes functionalized with ionic liquid could be used efficiently in the treatment of water containing trace concentration of cadmium. [ABSTRACT FROM AUTHOR]

Cadmium adsorption was studied using resin, zeolite and fish bone to identify alternatives for the removal of cadmium from giant squid hydrolyzed. Optimized pH and adsorbent dose for the standard cadmium solution were determined in preliminary assays under batch conditions. The adsorption kinetic was determined by pseudo-first-order, pseudo-second order and Elovich models. On the other hand, adsorption isotherms were fitted to the Langmuir and Freundlich models. A good correlation was observed by the three adsorbents between the experimental data and the pseudo-second-order kinetic model, with correlation coefficient values (R2) greater than 0.99, while Freundlich was the best fitted for all the adsorbents. From comparative study between the standard cadmium solution and giant squid hydrolyzed, standard solution had a better cadmium removal than giant squid hydrolyzed. These results were attributed to the complexity of giant squid hydrolyzed, the interference of other metals and the presence of amino acids, which led to competition for active sites. In terms of reusability of the adsorbents, resin could be repeatedly used in cadmium adsorption without detectable losses with respect to initial adsorption capacities. The use of resin and fish bone as adsorbents for cadmium in giant squid hydrolyzed processing is a good alternative for remove cadmium in aqueous food marine ingredient by batch method. [ABSTRACT FROM AUTHOR]

The advancement in conservationist strategies for development of nanoparticles is elemental to the subject of nanotechnology. Green protocols are highly preferred over conventional methods as they are environmentally benign. Certain phytochemicals in plant extracts exhibit natural tendencies of bio-reduction of salts. They also possess the ability of stabilizing these reduced particles by capping them. In present study leaf extract of Catharanthus roseus, an evergreen subshrub has been utilized for production of AgNPs and CuO-NPs. Synthesized nanoparticles were evaluated for their cadmium, chromium removal and antibacterial potential against S. aureus. AgNPs and CuO-NPs were optimized by varying salt concentration, leaf extract concentration and time interval to obtain better yield. UV–Vis spectroscopy was used to detect biogenic AgNPs and CuO-NPs. Wavelength range used for AgNPs and CuO-NPs was 300–700 and 200–700 nm successively. The morphology of nanoparticles was determined to be spherical and within 100 nm using SEM images. FT-IR investigation confirmed the presence of amines and alcohols in AgNPs. IR spectra of CuO-NPs revealed the ubiety of aldehydes/ ketones and carboxylic acids. The average distribution for silver was 602.9 nm and for copper was1066 nm as confirmed by DLS analysis. Further zeta-potential for AgNPs and CuO-NPs was recorded -16.4 mV and -6.18 mV. Kirby Bauer test for S.aureus show maximum ZOI i.e. 16 mm in case of AgNP (50 µl) and 10 mm in case of CuO-NP (50 µl). Highest chromium and cadmium removal was observed in case of biogenic silver nanoparticles i.e. 47.84% and 5.68% respectively. This is the first work that presents a comparative study of biogenic AgNPs and CuO-NPs from the leaf extract of Catharanthus roseus. Our findings can also help in improving the current scenario of metalloid pollution in soil and water environments. Hence, proper scaling up can make biogenic AgNPs and CuO-NPs a noteworthy tool in industries as well. [ABSTRACT FROM AUTHOR]

Shortcomings of individual biochar or microbial technologies often exist in heavy metal removal from wastewater and may be circumvented by coupled use of biochar and microorganisms. In this study, Bacillus subtilis and each of three biochars of different origins (corn stalk, peanut shell, and pine wood) were coupled forming composite systems to treat a cadmium (Cd, 50 mg/L) wastewater formulated with CdCl2 in batch tests. Biochar in composite system enhanced the activity and Cd adsorption of B. subtilis. Compared with single systems with Cd removal up to 33%, the composite system with corn stalk biochar showed up to 62% Cd removal, which was greater than the sum of respective single B. subtilis and biochar systems. Further analysis showed that the removal of Cd by the corn stalk composite system could be considered to consist of three successive stages, that is, the biochar-dominant adsorption stage, the B. subtilis-dominant adsorption stage, and the final biofilm formation stage. The final stage may have provided the composite system with the ability to achieve prolonged steady removal of Cd. The biochar-microorganism composite system shows a promising application for heavy metal wastewater treatment. HIGHLIGHTS Biochar enhanced the activity and cadmium adsorption of Bacillus subtilis.; Corn stalk composite system had higher cadmium removal efficiency than peanut shell and pine wood composite systems.; Cadmiun removal in corn stalk composite system was higher than the sum of the single biochar and Bacillus subtilis systems.; Cadmium removal in corn stalk composite system could be divided into three stages.;

Eco-friendly and sustainable practices must be followed while using the right plants and microbes to remove harmful heavy metals from the soil. The goal of the current study was to ascertain how effectively sorghum plants removed cadmium (Cd) from the soil using polyamines and mycorrhiza. Plant-biochemicals such as free amino acids, ascorbic acids, anthocyanin, proline, and catalase, APX, peroxidase activities were considered as markers in this study which revealed the adverse plant growth performance under 70 and 150 ppm of Cd concentration (w/w) after 30,60, and 90 days of treatment. The plants showed a mitigating effect against high Cd-concentration with exogenous use of mycorrhiza and putrescine. The treatment T17 (mycorrhiza +5 mM putrescine) showed a substantial decrease in the content of total free amino acid, ascorbic acid, catalase, APX, peroxidase by 228.36%, 39.79%, 59.06%, 182.79% 106.97%, respectively after 90 days as compared to T12 (150 ppm Cd). Anthocyanin content was negatively correlated (−0.503, −0.556, and −0.613) at p < 0.01 with other studied markers, with an increase by 10.52% in T17 treated plant as compared to T12. The concentration of Cd in root increased by 49.6% (141 ppm) and decreased in the shoot by 71% (17.8 ppm) in T17 treated plant as compared to T12 after 90 days. The application of mycorrhiza and putrescine significantly increased BCF (>1) and decreased TF (<1) for Cd translocation. The administration of mycorrhiza and putrescine boosted the Cd removal efficiency of sorghum plants, according to FTIR, XRD, and DSC analysis. As a result, this study demonstrates novel approaches for induced phytoremediation activity of plants via mycorrhiza and putrescine augmentation, which can be a promising option for efficient bioremediation in contaminated sites. [Display omitted] • Plant biomolecules were used as markers to assess cadmium (Cd) removal by sorghum plant. • Exogenous use of mycorrhiza and putrescine reduced Cd in shoot by 71% than control. • Mycorrhiza and putrescine significantly increased BCF (>1) and decreased TF (<1) for Cd translocation. • FTIR, XRD and DSC study validated the Cd removal efficacy of treated sorghum plant. [ABSTRACT FROM AUTHOR]

Water pollution caused by heavy metals is a major environmental problem, threatening water production, food safety, and human health. Cadmium (Cd) pollution is particularly serious because of food-chain biomagnification at toxic concentrations. Modified biochar is promising for heavy metal removal; however, efficient adsorbents for Cd removal are lacking. In the present study, a novel adsorbent, silica gel-modified biochar (SGB), was prepared and applied to treat sewage polluted by Cd. Through the batch adsorption experiments, it is known that SGB possessed outstanding Cd removal ability and recycleability. Furthermore, the adsorption behavior and mechanisms were analyzed by the application of kinetic and isotherm models. The maximum Cd2+ adsorption capacity of SGB was 38.08 mg g−1, and after five recycling processes, the Cd2+ removal rate was still 86.89 %. When the pH of the solution was 7.0, SGB showed the strongest Cd2+ adsorption capacity (29.06 mg g−1). When competitive ions existed, biochar also had high Cd removal efficiency, although the effect of Pb2+ was greater than those of Cu2+ and Zn2+, indicating that SGB was applicable to complex polluted water. Additionally, the main Cd2+ adsorption mechanisms by SGB were electrostatic interactions, π-π interactions, complexation, and co-precipitation. These results showed that SGB can effectively treat Cd-contaminated wastewater as a new adsorbent. [Display omitted] • SGB showed an outstanding Cd removal ability and excellent recyclability. • SGB showed the strongest Cd2+ adsorption capacity when the solution pH was 7.0. • SGB acted via electrostatic, π-π interactions, complexation, and co-precipitation. • SGB is expected to be beneficial for treating Cd-polluted water. • SGB also had high Cd removal efficiency in complex polluted water. [ABSTRACT FROM AUTHOR]

Biopolymer based membranes have garnered remarkable attention as an alternative to synthetic polymer based membranes due to exceptional properties such as biocompatibility, renewable, biodegradability and environmentally-benign. In this study, a novel porous chitosan/chitin whiskers composite membrane was successfully fabricated with the extraction of polyethylene glycol (PEG) for the removal of cadmium ions. The physicochemical and mechanical properties of selected composite samples were examined by varying the amount of chitin and PEG concentration respectively. Surface morphologies characterization study proves that highly porous structure is induced through the PEG dissolution meanwhile incorporation of chitin whiskers aids to produce a well-dispersed membrane with smaller pore size. Herein, strong interfacial adhesion between chitosan and chitin leads to interconnected network and increase in compactness of the matrix. Furthermore, these composite membranes exhibited high efficiency in cadmium ions removal. Overall, this study provides a framework on understanding the way to control the pore size, physicochemical and mechanical properties of polymer membranes using PEG and chitin whiskers. Thus, these bio-composite membranes have a great potential to be extensively employed in wastewater treatment. [ABSTRACT FROM AUTHOR]

In this study, a new adsorbent, which was synthesized by using SBA-15Santa Barbara Amorphous. modified with 1,5-diphenyl carbazide, was employed to extract cadmium (Cd) from aquatic systems. First, the sorbent was identified via various characterization techniques, and then the response surface methodology approach was applied for modeling and optimizing the adsorption performance of the sorbent. Under optimum conditions ($\mathrm{pH}=5.75$, an adsorbent dose of 4.55 mg, and a Cd concentration of 25.39 mg/L), an adsorption capacity of 160 mg/g was obtained. In addition, the sorption process was fast; it attained equilibrium in 25.39 min. Furthermore, the sorbent regenerated by nitric acid was reused without any significant loss of adsorption capacity. Finally, the experimental data were studied by different isotherm models and well described by the Langmuir model.

Sludge-based activated carbon (AC) was prepared for the cadmium (Cd) removal from the aqueous solution. X-ray diffraction and Fourier transform infrared were applied as two main techniques to investigate the surface characterizations of the adsorbent. Response surface methodology (RSM), which was coupled with central composite design (CCD), was applied to study the impact of three major parameters, such as pH, dosage (D) and initial concentrate (C) on the percentage of Cadmium removal. The RSM model indicates that the optimum points of Cd removal were 90% at pH = 8.74 and D/C = 50. The Financial Feasibility and Investment Strategy was also investigated to consider key indicators in the financial feasibility of water treatment projects. The present study shows the systematic investigation of an attractive adsorbent to remove Cd from an aqueous solution. Also, in this study, modern investment strategies and efficient financing methods for water treatment projects are provided. The results showed that this type of adsorbent is appropriately able to eliminate Cd from water and aqueous solution.

The abilities of three indigenous bacteria for bioremediation of cadmium contaminated soils collected from Agbabu Farm Settlement close to mining sites in Ondo state, Nigeria was studied to provide helpful information for soils remediation and soils health management in this sub-region for Millennium Development Goals accomplishment. Bacillus subtilis, Proteus mirabilis, and Escherichia coli isolated from the soils were inoculated into different soil samples conditioned with optimized factors determined from the first phase experiments. The conditioned samples were experimented for residual cadmium concentration with time in days using Atomic Absorption Spectrophotometer. The soil cadmium attenuation from the initial concentration of 70.21 mg/kg to below the maximum allowable of 3 mg/kg was hard for the organisms. Bacillus subtilis performed correction at time 35 days with an efficiency of 96.10 % and residual concentration of 2.74 mg/kg. Proteus mirabilis and Escherichia coli with respective, high efficiencies of 85.05% and 79.35% failed. The removal rate capacities were -0.131d-1 for B. subtilis; -0.111d-1 for P. mirabilis; -0.105d-1 for E. coli. Four kinetic models fitted described the experimental data well. The models assessment revealed the removals to be transport controlled as diffusion process was the rate-controlling step.

Heavy metal contamination of water is a burning global issue, and enormous importance has been given on easily applicable watertreatment methods namely adsorption. However, search for an efficient and reusable adsorbent is ever-evolving. In this study, activated carbon from highly ligno-cellulosic jute stick (JS-AC), the agricultural by-product of jute (Corchorus olitorius), was evaluated as a new adsorbent for removing cadmium (Cd) from the aqueous medium. The direct and interaction effects of four independent adsorption factors namely, initial Cd(II) concentration (20–100 mg/L), adsorbent dose (0.5–1 g/L), solution pH (3–7), and time (30–180 min) were investigated by applying response surface methodology (RSM). A 24 Box-Behnken matrix model with 3 centre points indicated that the maximum % Cd(II) removal was achieved at the initial concentration, dose, pH and time of 60.87 mg/L, 0.5 g/L, 7, and 30 min, respectively. The adsorption equilibrium was investigated by applying Freundlich, Langmuir, Temkin, and Jovanoic isotherm models while Langmuir isotherm exhibited the best fit (R2 = 0.99). The maximum Cd(II) adsorption capacity value of JS-AC was 73.53 mg/g. Finally, JS-AC was regenerated with 0.1M HNO3 as the desorption medium and reused for five successive cycles. This study indicated that jute stick, the under-utilised agro-residue of a cash crop, could be converted into a valuable product like JS-AC which offers immense application potential as an efficient and reusable adsorbent to treat Cd(II) contaminated aqueous medium before releasing in the environment. [ABSTRACT FROM AUTHOR]

BACKGROUND: Adsorption has been widely applied in wastewater treatment for heavy metal removal. Due to the high cost of adsorbent materials, various types of materials including agricultural, industrial wastes and naturally abundant materials have emerged as low‐cost adsorbents in recent years. However, enhancement processes need to be developed to improve the adsorption capability of the raw materials. It is still a challenge to find an economic material with high adsorption capacity. This paper demonstrates a strategy to activate a recycled waste material using a simple activating process, while significantly improving the adsorption capacity of cadmium from wastewater. RESULTS: The raw material feedstock is the non‐metallic aluminosilicate material obtained from the recycling of waste printed circuit boards (PCBs). By a simple thermal alkali activation process using potassium hydroxide as activation agent, the product material shows a strong capability of cadmium removal from effluent containing a high adsorption capacity of 2.12 mmol g−1. Initial metal concentration, dosage and pH effect on the adsorption isotherm and kinetics have been investigated. The experimental results include full characterization tests on this waste PCB‐derived adsorbent, and the in situ measurement of cadmium, calcium and potassium ions, since all are involved in the exchange sorption mechanism. CONCLUSION: By combining kinetic modelling analysis and X‐ray photoelectron spectroscopy, the novel adsorption mechanism has been explained and quantified as a dual ion‐exchange mechanism with the millimoles of cadmium exchanged mass balancing with the millimoles of calcium and 0.5 mmol potassium going into solution. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Activated coconut coir (ACC) was prepared by activation of raw coconut coir dust with 50 wt.% phosphoric acid followed by pyrolysis at 450°C in a nitrogen atmosphere. ACC demonstrated high efficacy in the removal of Cd(II) from aqueous solutions. Batch adsorption studies were carried out to study the effect of adsorbent dose, agitation time, pH and initial concentration of Cd(II) on the adsorption of Cd(II) on ACC. It was found that adsorption equilibrium was achieved rapidly within 10 min of agitation time and 98% of Cd(II) was removed from 10.00 mg L–1 Cd(II) solution at pH of 6 with 0.200 g of ACC. The rate of adsorption of Cd(II) on ACC followed pseudo-second-order kinetics. The equilibrium adsorption obeys linear Langmuir isotherm model for Cd(II) concentrations in the range of 10.00–100.00 mg L–1, whereas, in the entire concentration range of Cd(II) from 10.00 to 664.00 mg L–1, adsorption obeys non-linear Freundlich isotherm model. The maximum Cd(II) adsorption capacity of ACC was 45.02 mg g–1. The desorption study suggests that the ACC can be easily regenerated by simply washing it with 0.025 mol L–1 HCl solution. Because of the very rapid and simplicity of the adsorption and desorption processes, ACC has potential application as a promising adsorbent in the removal of cadmium ions from wastewater and water purification applications. [ABSTRACT FROM AUTHOR]

In this study, a novel and facile route for the synthesis of cyclodextrin-conjugated graphene oxide (CDs–GO) nanocomposites by esterification reaction in the presence of EDC/DMAP as catalyst, was developed. The formation of CDs–GO was successfully approved by FT-IR, SEM, TEM, TGA and BET analyses. Then competitive adsorption capacity of cadmium ion by CDs–GO composites and the impact of different empirical parameters like contact time, initial metal ion concentration, and initial pH on the adsorption process were studied. The results showed that β-CD–GO at pH 7 is suitable for removing Cd(II) with 90 % removal efficiency. Also, the adsorption capacity experiment at constant concentration of 50 ppm of Cd(II) showed that more than 50 % of Cd(II) ions could be adsorbed by γ-CD–GO reaching an equilibrium within 2 h. Therefore, the γ-CD–GO and α-CD–GO showed high adsorption capacity toward Cd2+ (222.22 mg/g) which were pointedly more than that of β-CD–GO (208.33 mg/g). Furthermore, adsorption kinetics, isotherm studies, and thermodynamic analyses were evaluated. The adsorption data exhibited excellent fit to the pseudo-second-order (R2 > 0.99) and Freundlich isotherm models. [ABSTRACT FROM AUTHOR]

Heavy metals removal from wastewaters and surface waters using low cost and eco-friendly adsorbents is one of the best ways to eliminate these impurities. In the current study, the nanocomposites based on chitosan-g-(acrylamide-co-itaconic acid) and titanium dioxide or silicon dioxide nanoparticles, were synthesized and their antibacterial property and the removal of Cd2+ from an aqueous solution have been investigated. The hydrogel and nanocomposites were synthesized via in situ polymerization within TiO2 and SiO2 nanoparticles separately. The products were characterized using FTIR, TGA, SEM, BET and EDX techniques. These analyses proved the synthesized nanocomposites and dispersion of nanoparticles with desirable properties. Nanocomposites were shown as porous structures with the average pore diameter of 4.40 and 5.05 nm for TiO2 and SiO2 composite, respectively. In addition, water absorption results indicated that by increasing the amount of nano particles, the water absorption decreases from 28 to 15 g/g for SiO2 nanocomposite and from 21 to 11 g/g for TiO2 nanocomposite. The effect of initial pH, initial concentration and time has been studied. Highest cadmium adsorption capacity for TiO2 and SiO2 nanocomposites respectively are 303, and 291 mg/gr. In addition, the equilibrium data and kinetics are described perfectly by pseudo second order kinetics and Freundlich isotherm. Freundlich isotherm has fitted the experimental data with the R2 of 0.96 and 0.91 for SiO2 and TiO2 nanocomposite, respectively. Antibacterial results showed that the synthesized nanocomposite inhibits the growth of E. coli and S. aureus.

Heavy metals released by various industries are among the major pollutants found in water resources. In this research, biosorption technique was employed to remove cadmium (Cd2+) from an aqueous system using a novel biosorbent developed from okara waste (OW), a residue from soya bean–based food and beverage processing. Characterisation results revealed that the OW biosorbent contained functional groups such as hydroxyl-, carboxyl- and sulphur-based functional groups, and the surface of the biosorbent was rough with multiple fissures which might be the binding sites for the pollutant. The effects of dosage, solution pH, initial Cd2+ concentration, temperature and contact time were investigated using batch adsorption mode. The biosorption equilibrium and kinetic were best described by the Langmuir and Elovich models, respectively. The maximum biosorption capacities predicted by the Langmuir model were 10.91–14.80 mg/g at 30–70 °C, and the biosorption process was favourable as evident from 0 < RL < 1. The uptake of Cd2+ by the OW biosorbent was spontaneous and endothermic. The plausible biosorption mechanisms of this study could be ionic exchange, hydrogen bonding and electrostatic interactions. The Cd2+ loaded OW biosorbent could be regenerated using 0.4 M of HCl solution and regeneration was studied for 4 adsorption-desorption cycles. The present investigation supported that OW can be reused as a value-added biosorbent product for the removal of Cd2+ from the contaminated water. [ABSTRACT FROM AUTHOR]

Cadmium is one of the leading pollutants due to its persistence and high mobility in the environment. In this work, the sorption behavior of cadmium ions were investigated using a newly synthesized adsorbent, multidentate amine ligand decorated hairy brushes on PS-DVB microbeads. The adsorption parameters were examined to evaluate the optimum values for pH, contact time, temperature and adsorbent amount (pH of 7.0, 5.0 mg adsorbent amount, 60.0 min. contact time, 25°C). The adsorption process well fitted with Langmuir isotherm and pseudo-second order model. The promising results indicated that the sorbent is a good alternative in cadmium removal studies. [ABSTRACT FROM AUTHOR]

Zeolite is a versatile and effective reactive material used in permeable reactive barriers (PRBs) for remediating groundwater contaminated with heavy metals. In this study, we evaluated the influence of subsurface environmental conditions, namely contamination level (C 0) and groundwater velocity (v), on predicting the longevity of zeolite for cadmium (Cd) removal. Batch experiments were performed to investigate the effect of C 0 on Cd removal, and column experiments were performed to examine how Cd transportation through zeolite varies at different C 0 and v. Breakthrough curves (BTCs) were analyzed with an advection-dispersion equation (ADE) coupled with nonequilibrium sorption rate models. The reaction parameters indicating the performance metrics of zeolite were determined using an iterative fitting approach—retardation factor (R), partitioning coefficient (β), and mass transfer coefficient (ω). R exhibited dependence on C 0 , but was unrelated to v ; its rapid increase at lower C 0 was explained by Langmuir sorption isotherms. β and ω, integral to sorption dynamics and mass transfer, respectively, showcased functional relationships with v. β decreased gradually as v increased, described by the nonequilibrium sorption model, whereas ω increased steadily with v , guided by the Monod function. Using the relationship of these parameters, the fate and transport of Cd within zeolite was simulated under various subsurface environmental conditions to construct the longevity prediction function. Thus, this study introduces a method for predicting the longevity of reactive materials, which can be valuable for designing PRBs with high longevity in the future. [Display omitted] • Zeolite exhibits nonlinear sorption concerning Cd by the contamination level (C 0). • Cd sorption on zeolite exhibits nonequilibrium rate by the groundwater velocity (v). • Nonequilibrium sorption parameters could be determined considering site-specific conditions. • Longevity as a zeolite in the permeable reactive barrier was predicted. [ABSTRACT FROM AUTHOR]