Adsorption properties of Pb(II) and Cd(II) in acid mine drainage by oyster shell loaded lignite composite in different morphologies.

A new idea to alleviate environmental pollution is the development of low-cost adsorbents using natural minerals and fishery wastes to treat high concentrations of heavy metal pollutants in acid mine drainage (AMD). Adsorbent morphology, adsorptive and regenerative capacity, and application potential are limiting factors for their large-scale use. Oyster shells capable of releasing alkalinity were loaded on the surface of lignite to develop two composite adsorbents with different morphologies (powdery and globular) for the treatment of AMD containing Pb(II) and Cd(II). The results show that the ability of the adsorbent to treat AMD is closely related to its morphologies. The pseudo-second-order kinetic model and the Langmuir model are suitable to describe the adsorption process of OS-M(P), and the maximum adsorption saturation capacities of Pb(II) and Cd(II) are 332.6219 mg/g and 318.9854 mg/g, respectively. The pseudo-second-order kinetic model and the Freundlich model are suitable to describe the adsorption process of OS-M(G). A synergistic result of electrostatic adsorption, neutralization precipitation, ion exchange and complex reaction is achieved in the removal of Pb(II) and Cd(II) by two morphologies of adsorbents. The regeneration times (5 times) and recovery rate (75.75%) of OS-M(G) are higher than those of OS-M(P) (3 times) and recovery rate (20%). The ability of OS-M(G) to treat actual AMD wastewater is still better than that of OS-M(P). OS-M(G) can be used as a promising environmentally friendly adsorbent for the long-term remediation of AMD. This study provides a comprehensive picture of resource management and reuse opportunities for natural mineral and fishery wastes.

Chicken manure-derived biochar enhanced the potential of Comamonas testosteroni ZG2 to remediate Cd contaminated soil.

The combined remediation of Cd-contaminated soil using biochar and microorganisms has a good application value. In this study, the effect of chicken manure-derived biochar on CdCO3 precipitation induced by Comamonas testosteroni ZG2 was investigated. The results showed that biochar could be used as the carrier of strain ZG2, enhance the resistance of strain ZG2 to Cd, and reduce the toxicity of Cd to bacterial cells. Cd adsorbed by biochar could be induced by strain ZG2 to form CdCO3 precipitation. Strain ZG2 could also induce CdCO3 precipitation when biochar was added during precipitation formation and fermentation broth formation. The CdCO3 precipitation could enter the pores of the biochar and attach to the surface of the biochar. The single and combined effects of strain ZG2 and biochar could realize the remediation of Cd-contaminated soil to a certain extent. The overall effect was in the order of strain ZG2 with biochar > biochar > strain ZG2. The combination of strain ZG2 and biochar reduced soil available Cd by 48.2%, the aboveground biomass of pakchoi increased by 72.1%, and the aboveground Cd content decreased by 73.3%. At the same time, it promoted the growth and development of the root system and improved the microbial community structure of the rhizosphere soil. The results indicated that chicken manure-derived biochar could enhance the stability of CdCO3 precipitation induced by strain ZG2, and strain ZG2 combined with biochar could achieve a more stable remediation effect on Cd-contaminated soil.

Cd(II)-based complex loaded with drug doxorubicin hydrogels against leukemia and reinforcement learning.

A new 3D metal-organic frameworks [Cd6(L)4(bipy)3(H2O)2·H2O] (1) was gained by employing Cd(II) and organic ligand [H3L = 4,4',4''-(benzene-1,3,5-triyltris(oxy))tribenzoic acid)benzene acid; bipy = 4,4'-bipyridine] in the solvothermal condition, which has been fully examined via single-X ray diffraction, FTIR and elemental analysis and so on. Using natural polysaccharides hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) as raw materials, we successfully prepared HA/CMCS hydrogels and observed their internal micromorphology by scanning electron microscopy. Using doxorubicin (Dox) as a drug model, we synthesized a novel metal gel particle loaded with doxorubicin, and their encapsulation and release effects were studied using fluorescence spectroscopy, followed by further investigation of their components through thermogravimetric analysis. Based on this, the therapeutic effect on leukemia was evaluated. Finally, an enhanced learning method for automatically designing new ligand structures from host ligands was proposed. Through generative modeling and molecular docking simulations, the biological behavior of the host and predicted cadmium complexes was extensively studied.

The quorum sensing SinI/R system contributes to cadmium immobilization in Ensifer adhaerens NER9 in the cadmium-contaminated solution.

In this study, the cadmium (Cd)-tolerant Ensifer adhaerens strain NER9 with quorum sensing (QS) systems (responsible for N-acyl homoserine lactone (AHL) production) was characterized for QS system-mediated Cd immobilization and the underlying mechanisms involved. Whole-genome sequence analysis revealed that strain NER9 contains the QS SinI/R and TraI/R systems. Strains NER9 and the NER9∆sinI/R, NER9∆traI/R, and NER9∆sinI/R-traI/R mutants were constructed and compared for QS SinI/R and TraI/R system-mediated Cd immobilization in the solution and the mechanisms involved. After 24 h of incubation, strain NER9 significantly decreased the Cd concentration in the Cd-contaminated solution compared with the NER9∆sinI/R, NER9∆traI/R, and NER9∆sinI/R-traI/R mutants. The NER9∆sinI/R mutant had a greater impact on Cd immobilization and a lower impact on the activities of AHLs than did the NER9∆traI/R mutant. The NER9∆sinI/R mutant had significantly greater Cd concentrations and lower cell wall- and exopolysaccharide (EPS)-adsorbed Cd contents than did strain NER9. Furthermore, the NER9∆sinI/R mutant presented a decrease in the number of functional groups interacting with Cd, compared with strain NER9. These results suggested that the SinI/R system in strain NER9 contributed to Cd immobilization by mediating cell wall- and EPS-adsorption in Cd-containing solution.

Synthesis, characterization and column adsorption properties of gum ghatti and water hyacianth derived cellulose grafted poly(vinyl sulfonic acid-co-acrylamide) composites.

Vinylsulfonic acid (VSA), acrylamide (AM) and N, N methylene bis acrylamide(MBA) were copolymerized by radical polymerization in the presence of gum ghatti (GG) and treated water hyacianth (WH) in water. Several composite copolymers were prepared by varying the i) AM: VSA molar ratios ii) wt% of GG and iii) wt% of treated WH based on a Box-Behnken Design(BBD) of a response surface methodology (RSM) model with three input variables and the batch adsorption capacity (mg/g) of 100 mg/L Cd (II) from water as response. The composite polymer was characterized by Fourier transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis(TGA), X- ray photo electron spectroscopy (XPS), compressive strength, pH reversibility, pH at point zero charge (pHPZC), Brunauer-Emmett-Teller (BET) surface area and scanning electron microscopy (SEM). The network parameters of the composites were determined. The copolymer composite prepared with AM: VSA of 5:1 containing 10 wt% GG and 4 wt% treated WH showed an optimum batch adsorption capacity of 399.15 mg/g Cd (II) from water containing 100 mg/L Cd (II). The same composite showed an adsorption capacity of 170.1 mg/g and a removal% of 31.5 at a feed concentration/feed flow rate/bed height of 150 mgL-1/30mLmin-1/30 mm in a fixed bed column.

Penicillium oxalicum induced phosphate precipitation enhanced cadmium (Cd) immobilization by simultaneously accelerating Cd biosorption and biomineralization.

Soil cadmium (Cd) is immobilized by the progressing biomineralization process as microbial induced phosphate precipitation (MIPP), which is regulated by phosphate (P) solubilizing microorganisms and P sources. However, little attention has been paid to the implications of Cd biosorption during MIPP. In this study, the newly isolated Penicillium oxalicum could immobilize 5.4-12.6 % of Cd2+, while the presence of hydroxyapatite (HAP) considerably enhanced Cd2+ immobilization in P. oxalicum and reached over 99 % Cd2+ immobilization efficiency within 7 days. Compared to P. oxalicum mono inoculation, MIPP dramatically boosted Cd biosorption and biomineralization efficiency by 71 % and 16 % after 96 h cultivation, respectively. P. oxalicum preferred to absorbing Cd2+ and reaching maximum Cd2+ biosorption efficiency of 87.8 % in the presence of HAP. More surface groups in P. oxalicum and HAP mineral involved adsorption which resulted in the formation of Cd-apatite [Ca8Cd2(PO4)6(OH)2] via ion exchange. Intracellular S2-, secreted organic acids and soluble P via HAP solubilization complexed with Cd2+, progressively mineralized into Cd5(PO4)3OH, Cd(H2PO4)2, C4H6CdO4 and CdS. These results suggested that Cd2+ immobilization was enhanced simultaneously by the accelerated biosorption and biomineralization during P. oxalicum induced P precipitation. Our findings revealed new mechanisms of Cd immobilization in MIPP process and offered clues for remediation practices at metal contaminated sites.

High-throughput visualization mutation screening technology to enhance the specificity of CadR based whole-cell cadmium biosensor.

As a heavy metal pollutant, Cd2+ often enters the human body through the food chain causing great harm to human health. Whole-cell biosensor is an emerging technology for rapid on-site detection of heavy metals with the advantages of inexpensive, fast to mass-produce, and strong in anti-interference resistance, but suffering from insatisfactory specificity. In this study, a strategy of Adjacent Site Saturation Mutation (ASSM) was designed to improve the specificity of transcription factor CadR, which acted as the recognition element and determined the specificity of whole cell Cd2+ biosensors. A specific saturated library was constructed using the strategy of adjacent mutation. After two rounds of high-throughput visual screening, a whole-cell biosensor with good response to Cd2+, and with significant weakened Hg2+ interference was obtained. The optimized whole-cell biosensor showed a linear dynamic concentration range from 500 nM to 100 µM, a detection limit of 0.079 µM, and has satisfactory specificity and anti-interference. The ASSM strategy proposed in this study can provide a new method for the application of synthetic biology in food safety detection, indicating the importance of whole-cell biosensors for the detection of heavy metals.

Does livestock-Manure-Derived Biochar Suitable for the Stabilization of Cadmium and Zinc in Contaminated Soil?

Both livestock-manure and livestock-manure-derived biochar have been used to remediate heavy metal-contaminated soil. However, direct comparisons of the heavy metal stabilization efficiency of livestock-manure and EQC-manure-biochar (derived from an equal quantity of corresponding livestock-manure) are limited. In the present study, the effect of livestock-manures and EQC-manure-biochars on soil properties and heavy metal bioavailability and leachability were compared using two contrasting soils (Ferralsols and Fluvisols). The results showed that both the livestock-manures and EQC-manure-biochars significantly changed soil pH, available phosphorus, available potassium, alkaline nitrogen and organic matter content (p < 0.05), but the trends were variable. In Ferralsols, the DTPA-extractable Cd and Zn decreased by -0.38%~5.70% and - 3.79%~9.98% with livestock-manure application and by -7.99%~7.23% and - 5.67%~7.17% with EQC-manure-biochars application. In Fluvisols, the DTPA-extractable Cd and Zn decreased by 13.39%~17.41% and - 45.26%~14.24% with livestock-manure application and by 10.76%~16.90% and - 36.38%~16.37% with EQC-manure-biochar application. Furthermore, the change in TCLP-extractable Cd and Zn in both soils was similar to that of DTPA-extractable Cd and Zn. Notably, the Cd and Zn stabilization efficiency of the EQC-manure-biochars was no better than that of the corresponding livestock-manures. These results suggest that the use of livestock-manure-derived biochar is not cost-effective for the remediation of heavy metal-contaminated soil.

Removal of cadmium and cobalt from water by Slovak bentonites: efficiency, isotherms, and kinetic study.

Slovak bentonite was used as an effective natural adsorbent for the removal of Cd(II) and Co(II). Characterization of the samples was conducted using X-ray diffraction (XRD), high-resolution scanning electron microscopy with an X-ray energy dispersion spectrometer (SEM-EDS), and infrared spectroscopy (FT-IR). Adsorption experiments were carried out for pure water and artificial seawater, each containing cobalt and cadmium cations within the concentration range of 5-60 mg/L. The highest bentonite adsorption capacities of the tested bentonites were 23.5 (Cd) and 32.2 (Co) mg g-1. The kinetics data revealed that, in addition to chemisorption, intraparticle diffusion contributes to metal removal. The physical and structural properties of bentonites play an important role in adsorption. Bentonite P 135 from the Lieskovec deposit showed the highest efficiency for removing both ions, with removal percentages exceeding 90% and 77.5% for pure water and artificial seawater, respectively. The results indicate the suitability of using Slovak bentonites as an alternative sorbent for both metal extractions. The mechanism of metal ion adsorption on bentonite clay can be understood through surface complexation and ion exchange. The examined bentonite deposits show potential as promising natural sorbents for the removal of cobalt and cadmium cations from polluted waters.

Integration of metal organic framework nanoparticles into sodium alginate biopolymer-based three-dimensional membrane capsules for the efficient removal of toxic metal cations from water and real sewage.

Sodium alginate (SA) biopolymer has been recognized as an efficient adsorbent material owing to their unique characteristics, including biodegradability, non-toxic nature, and presence of abundant hydrophilic functional groups. Accordingly, in the current research work, UiO-66-OH and UiO-66-(OH)2 metal organic framework (MOF) nanoparticles (NPs) have been integrated into SA biopolymer-based three-dimensional (3-D) membrane capsules (MCs) via a simple and facile approach to remove toxic metal cations (Cu2+ and Cd2+) from water and real sewage. The newly configured capsules were characterized by FTIR, SEM, XRD, EDX and XPS analyses techniques. Exceptional sorption properties of the as-developed capsules were ensured by evaluation of the pertinent operational parameters, i.e., contents of MOF-NPs (1-100 wt%), adsorbent dosage (0.001-0.05 g), content time (0-360 h), pH (1-8), initial concentration of metal cations (5-1000 mg/L) and reaction temperature (298.15-333.15 K) on the eradication of Cu2+ and Cd2+ metal cations. It was found that hydrophilic functional groups (-OH and -COOH) have performed an imperative role in the smooth loading of MOF-NPs into 3-D membrane capsules via intra/inter-molecular hydrogen bonding and van der waals potencies. The maximum monolayer uptake capacities (as calculated by the Langmuir isotherm model) of Cd2+ and Cu2+ by 3-D SGMMCs-OH were 940 and 1150 mg/g, respectively, and by 3-D SGMMCs-(OH)2 were 1375 and 1575 mg/g, respectively, under optimum conditions. The as-developed capsules have demonstrated superior selectivity against targeted metal cations under designated pH and maintained >80 % removal efficiency up to six consecutive treatment cycles. Removal mechanisms of metal cations by the 3-D SGMMCs-OH/(OH)2 was proposed, and electrostatic interaction, ion-exchange, inner-sphere coordination bonds/interactions, and aromatic ligands exchange were observed to be the key removal mechanisms. Notably, FTIR and XPS analysis indicated that hydroxyl groups of Zr-OH and BDC-OH/(OH)2 aromatic linkers played vital roles in Cu2+ and Cd2+ adsorption by participating in inner-sphere coordination interactions and aromatic ligands exchange mechanisms. The as-prepared capsules indicated >70 % removal efficiency of Cu2+ from real electroplating wastewater in the manifestation of other competitive metal ions and pollutants under selected experimental conditions. Thus, it was observed that newly configured 3-D SGMMCs-OH/(OH)2 have offered a valuable discernment into the development of MOFs-based water decontamination 3-D capsules for industrial applications.

Innovative recovery of matrix layered double hydroxide from simulated acid mine wastewater for the removal of copper and cadmium from wastewater.

This study innovatively added biochar to optimize regulation in the neutralization process of simulated acid mine drainage (AMD) and recovered a new type of matrix layered double hydroxides (MLDH), which can be used to remove copper (Cu(II)) and cadmium (Cd(II)) from wastewater. A series of batch experiments show that MLDH with strong selective removal ability of Cu(II) and Cd(II) can be successfully obtained by adding biochar (BC) at pH = 5 end in the neutralization process. Kinetic and isotherm modeling studies indicated that the removal of Cu(II) and Cd(II) by the MLDH was a chemical multilayer adsorption process. The removal mechanism of Cu(II) and Cd(II) was further analyzed through related characterization analysis with contribution rate calculation: the removal rates of Cu(II) and Cd(II) by ion exchange were 42.7% and 26%, while that by precipitation were 34.5% and 49.9%, respectively. This study can provide a theoretical reference and experimental basis for the recovery and utilization of valuable by-products in AMD and the treatment of heavy metal wastewater.

CRISPR/Cas12a-Amplified Aptamer Switch Microplate Assay for Small Molecules.

The presence of small molecule contaminants such as mycotoxins and heavy metals in foods and the environment causes a serious threat to human health and huge economic losses. The development of simple, rapid, sensitive, and on-site methods for small molecule pollutant detection is highly demanded. Here, combining the advantages of structure-switchable aptamer-mediated signal conversion and CRISPR/Cas12a-based signal amplification, we developed a CRISPR/Cas12a-amplified aptamer switch assay on a microplate for sensitive small molecule detection. In this assay, a short DNA strand complementary to the aptamer (cDNA) is immobilized on a microplate, which can capture the aptamer-linked active DNA probe (Apt-acDNA) in the sample solution when the target is absent. With the addition of the Cas12a reporter system, the captured Apt-acDNA probes activate Cas12a to indiscriminately cleave fluorescent DNA substrates, producing a high fluorescence signal. When the target is present, the Apt-acDNA probe specifically binds to the target rather than hybridizing with cDNA on the microplate, and the fluorescence signal is reduced. The analytical performance of our method was demonstrated by the detection of two highly toxic pollutants, aflatoxin B1 (AFB1) and cadmium ion (Cd2+), as examples. The assay exhibited good selectivity and high sensitivity, with detection limits of 31 pM AFB1 and 3.9 nM Cd2+. It also allowed the detection of targets in the actual sample matrix. With the general signal conversion strategy, this method can be used to detect other targets by simply changing the aptamer and cDNA, showing potential practical applications in broad fields.

Biofilm hydrogel derived from physical crosslinking (self-assembly) of xanthan gum and chitosan for removing Cd2+, Ni2+, and Cu2+ from aqueous solution.

This study aimed to fabricate a series of biodegradable hydrogel films by gelating/physically crosslinking a blend of xanthan gum (XG) and chitosan (CS) in various combinations using a facile, green, and low cost solution casting technique. The adsorption of Cd2+, Cu2+ and Ni2+ by the XG/CS biofilm in aqueous solution was studied in batch experiments to determine how the pH of the solution, contact time, dosage of adsorbent, initial metal ion concentration and ionic strength affect its adsorption. A highly pH-dependent adsorption process was observed for three metal ions. A maximum amount of Cd2+, Ni2+, and Cu2+ ions was adsorbable with 50 mg of the adsorbent at pH 6.0 for an initial metal concentration of 50 mg.L-1. An empirical pseudo-second-order model seems to fit the kinetic experimental data reasonably well. It was found that the Langmuir model correlated better with equilibrium isotherm when compared with the Freundlich model. For Cd2+, Ni2+, and Cu2+ ions at 25 °C, the maximum monolayer adsorption capacity was 152.33, 144.79, and 139.71 mg.g-1, respectively. Furthermore, the biofilm was capable of regenerating, allowing metal ions to adsorb and desorb for five consecutive cycles. Therefore, the developed biodegradable film offers the potential for remediation of specified metal ions.

Decoration of dandelion-like manganese-doped iron oxide microflowers on plasma-treated biochar for alleviation of heavy metal pollution in water.

Carbon-based biowaste incorporated with inorganic oxides as a composite is an enticing option to mitigate heavy metal pollution in water resources due to its more economical and efficient performance. With this in mind, we constructed manganese-doped iron oxide microflowers resembling the dandelion-like structure on the surface of cold plasma-treated carbonized rice husk (MnFe2O3/PCRH). The prepared composite exhibited 45% and 19% higher removal rates for Cu2+ and Cd2+, respectively than the pristine CRH. The MnFe2O3/PCRH composite was characterized using XRD, FTIR, FESEM, EDX, HR-TEM, XPS, BET, TGA, and zeta potential, while the adsorption capacities were investigated as a function of pH, time, and initial concentration in batch trials. As for the kinetics, the pseudo-second-order was the rate-limiting over the pseudo-first-order and Elovich model, demonstrating that the chemisorption process governed the adsorption of Cu2+ and Cd2+. Additionally, the maximum adsorption capacities of the MnFe2O3/PCRH were found to be 122.8 and 102.5 mg/g for Cu2+ and Cd2+, respectively. Based on thorough examinations by FESEM-EDS, FTIR, and XPS, the possible mechanisms for the adsorption can be ascribed to surface complexation by oxygen-containing groups, a dissolution-precipitation of the ions with -OH groups, electrostatic attraction between metal ions and the adsorbent's partially charged surface, coordination of Cu2+ and Cd2+ with π electrons by aromatic/graphitic carbon in the MnFe2O3/PCRH, and pore filling and diffusion. Lastly, the adsorption efficiencies were maintained at about 70% of its initial adsorption even after five adsorption-desorption cycles, displaying its remarkable stability and reusability.

CdIn2Se4@chitosan heterojunction nanocomposite with ultrahigh photocatalytic activity under sunlight driven photodegradation of organic pollutants.

This research focused on synthesizing a CdIn2Se4@Ch nanocomposite by doping CdIn2Se4 into chitosan using a photolysis assisted ultrasonic process. The aim was to enhance the photodegradation efficiency of ofloxacin and 2,4-dichlorophenoxyacetic acid under sunlight. The synthesized CdIn2Se4@Ch nanocomposite was investigated via different techniques, including XRD, XPS, FTIR, TEM, DSC, TGA, UV-Vis and PL. The study also investigated the influence of various reaction parameters, including the effects of inorganic and organic ions. The synthesized nanocomposite demonstrated exceptional efficiency, achieving 86 % and 95 % removal rates, with corresponding rate constants of 0.025 and 0.047 min-1. This performance surpasses that of CdIn2Se4 by approximately 1.35 and 2.25 times, respectively. The values of COD were decreased to 78 and 86 % for ofloxacin and 2,4-dichlorophenoxyacetic, while the TOC values decreased to 71 and 84 %, respectively, from their premier values. The improvement in performance is associated with the introduction of CdIn2Se4 into chitosan, resulting in the self-integration of Cd into the catalyst. This creates a localized accumulation point for electrons, enhancing the efficiency of charge separation and further reducing the surface charge of chitosan. Experimental evidence suggests that superoxide and hydroxyl radicals play a significant role in the photodegradation of pollutants. Additionally, the nanocomposite exhibits excellent stability and can be reused up to five times, indicating remarkable stability and reusability of the developed photocatalyst.

Iron and silicon modified biochar for enhancing cadmium removal from water: Unveiling the crucial role of iron-induced silicon dissolution.

The interaction mechanisms of silicon (Si) and active ingredient iron (Fe) on cadmium (Cd) removal are still unknown. Herein, the Fe/Si modified biochar (Fe/Si-BC) was synthesized to enhance Cd removal by pre-immersion of Fe and ball milling loading of Si. Detailed characterizations indicated that Fe and Si were successfully introduced into Fe/Si-BC, resulting in the formation of a new metallic silicate (Ca2.87Fe0.13(SiO3)2). The maximum Cd adsorption capacity of Fe/Si-BC (31.66 mg g-1) was 3.6 times and 2.5 times higher than that of Fe-BC (8.89 mg g-1) and Si-BC (11.03 mg g-1), respectively, deriving from an enhancement of Si dissolution induced by Fe introduction. The dissolved Si could capture and combine Cd to form CdSiO3 precipitation, which was strongly supported by the random forest regression and correlation between dissolved Si content and Cd adsorption capacity. This study advances the mechanistic insights into synergistic functions of Si and Fe in Cd removal.

High performance self-assembled sulfidized nanoscale zero-valent iron for the immobilization of cadmium in contaminated sediments: Optimization, microbial response, and mechanisms.

Sulfidized nanoscale zero-valent iron (S-nZVI) showed excellent removal capacity for cadmium (Cd) in aqueous phase. However, the remediation effects of S-nZVI on Cd-contaminated sediment and its interactions with microorganisms in relation to Cd fate remain unclear. The complexity of the external environment posed a challenge for Cd remediation. This study synthesized S-nZVI with different S and Fe precursors to investigate the effect of precursors and applied the optimal material to immobilize Cd in sediments. Characterization analysis revealed that the precursor affected the morphology, Fe0 crystallinity, and the degree of oxidation of the material. Incubation experiments demonstrated that the immobilization efficiency of Cd using S-nZVIFe3++S2- (S/Fe = 0.14) reached the peak value of 99.54%. 1% and 5% dosages of S-nZVI significantly reduced Cd concentration in the overlying water, DTPA-extractable Cd content, and exchangeable (EX) Cd speciation (P < 0.05). Cd leaching in sediment and total iron in the overlying water remained at low levels during 90 d of incubation. Notably, each treatment maintained a high Cd immobilization efficiency under different pH, water/sediment ratio, organic acid, and coexisting ion conditions. Sediment physicochemical properties, functional bacteria, and a range of adsorption, complexation and precipitation of CdS effects dominated Cd immobilization.

Chitosan-assisted self-assembly of flower-shaped ε-Fe2O3 nanoparticles on screen-printed carbon electrode for Impedimetric detection of Cd2+, Pb2+, and Hg2+ heavy metal ions in various water samples.

This study focuses on the fabrication of a novel sensing platform on a screen-printed carbon electrode, modified by a combination of hydrothermally synthesized iron dioxide (ε-Fe2O3) nanoparticles and Chitosan (CS) biopolymer. This unique organic-inorganic hybrid material was developed for Electrochemical Impedance Spectroscopy (EIS) sensing, specifically targeting heavy metal ions that include Hg2+, Cd2+, as well as Pb2+. The investigation encompassed a comprehensive analysis of various aspects of the prepared Fe2O3 and CS/ε-Fe2O3 nanocomposites, including phase identification, determination of crystallite size, assessment of surface morphology, etc. CS/ε-Fe2O3 was drop-casted and deposited on the Screen-Printed Electrode (SPE). The resulting sensor exhibited excellent performance in the precise and selective quantification of Hg2+, Cd2+, and Pb2+ ions, with minimal interference from other substances. The fabricated sensor exhibits excellent performance as the detection range for Hg2+, Cd2+, and Pb2+ ions linearity is 2-20 µM, sensitivity, and LOD are 243 Ω/ µM cm2 and 0.191 µM, 191 Ω/µM cm2, and 0.167 µM, 879 Ω/ µM cm2, and 0.177 µM respectively. The stability of the CS/ε-Fe2O3/SPE electrode is demonstrated by checking its conductivity for up to 60 days for Hg2+, Cd2+, and Pb2+ ions. The reusability of the fabricated electrode is 14 scans, 13 scans, and 12 scans for Hg2+, Cd2+, and Pb2+ ions respectively. The findings indicate the successful development of an innovative CS/ε-Fe2O3 electrode for the EIS sensing platform. This platform demonstrates notable potential for addressing the critical need for efficient and sensitive EIS sensors capable of detecting a range of hazardous heavy metal ions, including Hg2+, Cd2+, and Pb2+.

Microwave promoted graft copolymerization of poly(ethylacrylate) onto k-carrageenan for removal of Cd and Ni from aqueous solution.

Microwave promoted graft copolymerization of poly (ethyl acrylate) onto kappa-carrageenan in presence of a redox pair (ascorbic acid and potassium persulfate) led to the formation of a novel copolymer hydrogel, kappa-carrageenan-graft-poly (ethylacrylate). By varying the reaction conditions such as the microwave power, reaction time, concentration of kappa-carrageenan, ascorbic acid and persulfate, copolymers of highest percentage grafting was obtained and characterized by FT-IR, SEM, TGA and XRD. The copolymer was evaluated as an adsorbent for the adsorption of Ni(II) and Cd(II). Various adsorption parameters such as contact time, pH, initial metal ion concentration, temperature, electrolyte strength and adsorbent dosage were varied to obtain the optimum conditions for the adsorption. The adsorption data for Cd(II), fitted better for Langmuir and Ni(II), fitted much better for Freundlich adsorption isotherm model. Maximum adsorption obtained for cadmium ions and nickel ions was 308.6 mg/g-1 and 305.8 mg/g-1 respectively. The adsorption of both metal ions followed pseudo second order kinetic model. The positive ΔH values endorsed the adsorption process to be endothermic in nature. The negative values of ΔG indicate the spontaneity of the adsorption process while the positive ΔS values showed that the adsorption of metal ions proceeded with increased randomness at the surface of the copolymer. High recovery percentage of the metal ions from the adsorbent indicates that the copolymer can be used for more adsorption cycles.