Search Results (71)

Currently, few studies have revealed the comprehensive effects of environmental organic matter, freeze–thaw and oxidative aging on the adsorption performance of cadmium (Cd(II)), which is essential for the sustainable stability evaluation of the adsorbent. Herein, we observed that humic acids (HAs) extracted from different soils inhibited the adsorption performance of Cd(II) onto the cuttlebone-derived samples by occupying the different major adsorption active sites of the adsorbent, and the lower cadmium-complexation ability of HAs would increase the occupation of adsorption sites. The freeze–thaw process increased the pore size and volume of the cuttlebone-derived samples, while oxidative aging enhanced the specific surface area and introduced additional C–O/C=O groups. These changes promoted the adsorption performance of Cd(II) in the cuttlebone-derived samples after freeze–thaw or oxidative aging. Additionally, the resistances of cuttlebone-based adsorbents to HAs, freeze–thaw, and oxidative aging were elucidated and optimized by simple alkali boiling or carbonization treatment. Furthermore, the adsorption capacities of Cd(II) by samples in the natural cadmium-contaminated river ranged from 548.99 mg g⁻¹ to 571.55 mg g⁻¹, which are higher values than those of most reported adsorbents. Therefore, this work provides an important experimental basis for the practical application and sustainable design of adsorbents under real environmental conditions. Full article

With the increasing severity of cadmium (Cd) contamination in soil and its persistent toxicity, developing efficient remediation methods has become a critical necessity. In this study, sodium borohydride (NaBH₄) and tea polyphenols (TP) were employed as reducing agents to synthesize biochar (BC)-supported nanoscale zero-valent iron (nZVI), denoted as BH₄-nZVI/BC and TP-nZVI/BC, respectively. The effects of dosage, pH, and reaction time on Cd immobilization efficiency were systematically investigated. Both composites effectively stabilized Cd, significantly reducing its mobility and toxicity. Toxicity Characteristic Leaching Procedure (TCLP) results showed that Cd leaching concentrations decreased to 8.23 mg/L for BH₄-nZVI/BC and 4.65 mg/L for TP-nZVI/BC, corresponding to performance improvements of 29.9% and 60.5%. The immobilization process was attributed to the reduction of Cd(II) into less toxic species, together with adsorption and complexation with oxygen-containing groups (-OH, -COOH, phenolic) on biochar. TP-nZVI/BC exhibited superior long-term stability, while maintaining slightly lower efficiency than BH₄-nZVI/BC under certain conditions. Microbial community analysis revealed minimal ecological disturbance, and TP-nZVI/BC even promoted microbial diversity recovery. Mechanistic analyses further indicated that tea polyphenols formed a protective layer on nZVI, which inhibited particle agglomeration and oxidation, reduced the formation of iron oxides, preserved Fe⁰ activity, and enhanced microbial compatibility. In addition, the hydroxyl and phenolic groups of tea polyphenols contributed directly to Cd(II) complexation, reinforcing long-term immobilization. Therefore, TP-nZVI/BC is demonstrated to be an efficient, sustainable, and environmentally friendly amendment for Cd-contaminated soil remediation, combining effective immobilization with advantages in stability, ecological compatibility, and long-term effectiveness. Full article

Cadmium (Cd) pollution in rice crops is a global environmental challenge, endangering food security and sustainable agricultural development. Cd ions are highly dynamic and toxic and can easily accumulate in rice grains, resulting in adverse consequences on human health and ecological safety. With accelerated industrialization and abundant agricultural activities, Cd enters paddy soils through multiple pathways, leading to increasingly complex processes of migration and transformation of Cd in the soil–rice ecosystem. Although recent studies have substantially advanced our comprehension of the pathways promoting the uptake, transport, and accumulation of Cd in rice, this information is scattered and lacks systematic integration, leading to an incomplete understanding of the entire contamination process. This review adopts a rigorous perspective spanning from soil input to grain accumulation and comprehensively summarizes the absorption pathways, translocation mechanisms, and remediation strategies for Cd pollution in rice. The effects of phytotoxicity induced by Cd on rice growth are thoroughly analyzed, and recent advances in various mitigation strategies are highlighted, including agronomic management, cultivar improvement, bioremediation, and signal regulation. By integrating the findings of latest research, this review (i) proposes a mechanistic network of Cd contamination occurrence and control in rice; (ii) elucidates critical regulatory nodes; and (iii) offers a theoretical framework for growing rice cultivars with a low Cd content, remediating Cd-contaminated farmlands, and ensuring food safety. Full article

Cadmium {Cd (II)} poses a high risk to ecological security and human health due to its high toxicity, easy migration and difficult degradation. Using waste rubber seed shell biochar (RSSB) as the carrier material of nZVI may inhibit the caking oxidation of zero-valent iron and improve the removal efficiency of Cd (II) from water. Through a series of batch experiments, the adsorption mechanism of modified biochar on Cd (II) clarified that the removal effect of nano-zero-valent iron-rubber seed shell biochar (nZVI-RSSB) on heavy metals in water was better than that of RSSB. The results showed that when the dosage of complex biochar was 80 mg, the initial concentration of Cd (II) was 50 mg/L, and the solution pH was 6, the maximum adsorption capacity of nZVI-RSSB for Cd (II) reached 30.42 mg/g, compared with the RSSB of 13.32 mg/g. The adsorption kinetics model showed that chemisorption and physical adsorption existed simultaneously. The results of the in-particle diffusion model show that the adsorption process may be divided into two stages. The Langmuir competitive adsorption model was followed. Electrostatic adsorption and precipitation/co-precipitation could be the main ways for the removal of Cd (II) by composite materials. Meanwhile, the synergistic adsorption of nZVI-RSSB composites with multiple metals in actual water showed its application potential in water pollution control. Hence, the nZVI-RSSB not only successfully inhibits the caking oxidation of zero-valent iron, but also effectively improves the removal efficiency of heavy metals from water. Full article

Salinomycin is a polyether ionophorous antibiotic with promising antineoplastic properties. Published studies have revealed that the compound also exerts pronounced antidotal activity against cadmium (Cd) and lead (Pb) intoxications. It has been proven that salinomycin with Cd(II) forms a coordination compound of a composition [Cd(C₄₂H₆₉O₁₁)₂(H₂O)₂] and an octahedral molecular geometry, while the coordination compound of the antibiotic with Pb(II) has a square pyramidal structure and composition [Pb(C₄₂H₆₉O₁₁)(NO₃)]. To date, there is no published information about the ability of salinomycin to form complexes with the mercury ion (Hg(II)). Herein, we report, for the first time, a synthetic procedure for a complex compound of salinomycin with Hg(II). The coordination compound was characterized by a variety of methods, such as elemental analysis, attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), electrospray ionization–mass spectrometry (ESI-MS), powder X-ray diffraction, nuclear magnetic resonance spectroscopy (NMR), thermogravimetry with differential thermal analysis (TG-DTA), and thermogravimetry with mass spectrometry (TG-MS). The elemental analysis data revealed that the new compound is of the chemical composition [Hg(C₄₂H₆₉O₁₁)(H₂O)(OH)]. Based on the results from the spectral analyses, the most probable structure of the complex was proposed. Full article

Cadmium (Cd) mobilization in paddy soils during redox fluctuations poses significant risks to rice safety. This study investigated the efficacy of nano-calcium carbonate (NCC), nano-hydroxyapatite (NHAP), and their composite (C+P) in immobilizing Cd under simulated flooding–drainage cycles. Soil treatments (0.5% and 1.0% w/w) were subjected to 40 day anaerobic and 20 day aerobic incubation. The results demonstrated that NCC and C+P elevated the soil pH by 1.35–1.39 and 0.72–1.01 units during the anaerobic and aerobic phases, respectively. These amendments suppressed Fe(II) and Mn(II) release by 41–75%, correlating with reduced Cd bioavailability. While nanomaterials minimally influenced Cd speciation during flooding, aerobic conditions triggered a marked shift: residual Cd fractions increased by 80.8–116.4% under NCC, driven by CdCO₃ precipitation and phosphate complexation. Cd release rates decreased by 53.6–66.8% in NCC and C+P treatments during oxidation. Microbial analysis revealed diminished bacterial diversity but enriched Firmicutes (up to 58.9%), which positively correlated with pH and residual Cd. Redundancy analysis identified pH and Fe/Mn dynamics as key regulators of the microbial community structure. NCC emerged as the most effective amendment. This study highlights the potential of NCC-based strategies for mitigating Cd risks in acidic paddy soils, particularly during post-flooding drainage. Full article

Microplastics (MPs) can serve as vectors for heavy metals in aquatic environments; however, the adsorption behavior of MPs on multiple heavy metal systems is still unclear. This study investigated the adsorption characteristics of biodegradable poly (butylene succinate) (PBS) for cadmium (Cd(II)) and arsenic (As(III)) in both single and binary systems. Adsorption isotherms were studied using the Linear, Langmuir, and Freundlich models, and further analysis of MPs adsorption characteristics was conducted using site energy distribution theory and density functional theory. The results indicate that the maximum adsorption capacities of PBS for Cd(II) and As(III) are 2.997 mg/g and 2.606 mg/g, respectively, with the Freundlich model providing the best fit, suggesting multilayer adsorption on heterogeneous sites. As(III) has a higher adsorption affinity for PBS than Cd(II), with a binding energy of −11.219 kcal/mol. Additionally, the adsorption mechanisms of Cd(II) and As(III) on PBS include electrostatic interactions and surface complexation, with the primary adsorption sites at the C=O of the carboxyl group and the hydroxyl group. The comprehension of interfacial interactions between biodegradable plastics and heavy metals is facilitated by a combination of theoretical calculations and experimental investigations. Full article

This article presents a study of cadmium removal from nitrate medium using adsorption in calcined mesoporous silica (MCM-C), mesoporous silica doped (MCM_DIOPA), and calcined and impregnated mesoporous silica (MCM@DIOPA), with diisooctylphosphinic acid (DIOPA). The sorbents were synthesized via a sol–gel method. Several characterization techniques, such as XRD, FTIR spectroscopy, N₂ sorption and elemental analysis, have been used to determine the main structural, textural, and chemical properties of prepared sorbents. Batch adsorption and kinetics tests were carried out, where the influence of pH and contact time of the sorbents and their role in cation removal were studied. Experimental results show poor sorption efficiencies with MCM-C and MCM_DIOPA at pH 5.85. At the same pH, better cadmium extraction was attained by MCM@DIOPA and was achieved within 30 min. The pseudo-second-order model is the most appropriate model to describe the elimination mechanism of Cd(II) ions. The Langmuir equation was used to model the sorption isotherm and the maximum sorption capacity of Cd(II) is 22.16 mg/g (200 mmol/kg). The complex type of the probable extracted species isCdL2-HL. Full article

Lead (Pb) and cadmium (Cd) are toxic pollutants that are prevalent in wastewater and pose a serious threat to the natural environment. In this study, a new immobilized bacterial microsphere (CYB-SA) was prepared from corn stalk biochar and Klebsiella grimontii by sodium alginate encapsulation and vacuum freeze-drying technology. The removal effect of CYB-SA on Pb(II) and Cd(II) in a monometallic contaminated solution was studied. The results showed that the removal of Pb(II) and Cd(II) by CYB-SA was 99.14% and 83.35% at a dosage of 2.0 g/L and pH = 7, respectively, which was 10.77% and 18.58% higher than that of biochar alone. According to the Langmuir isotherm model, the maximum adsorption capacities of Pb(II) and Cd(II) by CYB-SA at 40 °C were 278.69 mg/g and 71.75 mg/g, respectively. A combination of the kinetic model, the isothermal adsorption model, scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analyses showed that the main adsorption mechanisms of CYB-SA encompass functional group complexation, ion exchange, electrostatic attraction and physical adsorption. The findings of this study offer practical and theoretical insights into the development of highly efficient adsorbents for heavy metals. Full article

The aim of this study was to identify key proteins of synaptic transmission in the cochlear nucleus (CN) that are involved in normal hearing, acoustic stimulation, and tinnitus. A gene list was compiled from the GeneCards database using the keywords “synaptic transmission” AND “tinnitus” AND “cochlear nucleus” (Tin). For comparison, two gene lists with the keywords “auditory perception” (AP) AND “acoustic stimulation” (AcouStim) were built. The STRING protein–protein interaction (PPI) network and the Cytoscape data analyzer were used to identify the top two high-degree proteins (HDPs) and their high-score interaction proteins (HSIPs), together referred to as key proteins. The top1 key proteins of the Tin-process were BDNF, NTRK1, NTRK3, and NTF3; the top2 key proteins are FOS, JUN, CREB1, EGR1, MAPK1, and MAPK3. Highly significant GO terms in CN in tinnitus were “RNA polymerase II transcription factor complex”, “late endosome”, cellular response to cadmium ion”, “cellular response to reactive oxygen species”, and “nerve growth factor signaling pathway”, indicating changes in vesicle and cell homeostasis. In contrast to the spiral ganglion, where important changes in tinnitus are characterized by processes at the level of cells, important biological changes in the CN take place at the level of synapses and transcription. Full article

Heavy metals constitute pollutants that are particularly common in air, water, and soil. They are present in both urban and rural environments, on land, and in marine ecosystems, where they cause serious environmental problems since they do not degrade easily, remain almost unchanged for long periods, and bioaccumulate. The detection and especially the quantification of metals require a systematic process. Regular monitoring is necessary because of seasonal variations in metal levels. Consequently, there is a significant need for rapid and low-cost metal determination methods. In this study, we compare and analytically validate absorption spectrometry with a sensitive voltammetric method, which uses a bismuth film-plated electrode surface and applies stripping voltammetry. Atomic absorption spectroscopy (AAS) represents a well-established analytical technique, while the applicability of anodic stripping voltammetry (ASV) in complicated sample matrices such as soil samples is currently unknown. This sample-handling challenge is investigated in the present study. The results show that the AAS and ASV methods were satisfactorily correlated and showed that the metal concentration in soils was lower than the limit values but with an increasing trend. Therefore, continuous monitoring of metal levels in the urban complex of a city is necessary and a matter of great importance. The limits of detection of cadmium (Cd) were lower when using the stripping voltammetry (SWASV) graphite furnace technique compared with those obtained with AAS when using the graphite furnace. However, when using flame atomic absorption spectroscopy (flame-AAS), the measurements tended to overestimate the concentration of Cd compared with the values found using SWASV. This highlights the differences in sensitivity and accuracy between these analytical methods for detecting Cd. The SWASV method has the advantage of being cheaper and faster, enabling the simultaneous determination of heavy elements across the range of concentrations that these elements can occur in Mediterranean soils. Additionally, a dsDNA biosensor is suggested for the discrimination of Cu(I) along with Cu(II) based on the oxidation peak of guanine, and adenine residues can be applied in the redox speciation analysis of copper in soil, which represents an issue of great importance. Full article

The discharge of lead and cadmium wastewater, along with the pollution caused by phosphogypsum, represents a particularly urgent environmental issue. This study employed a straightforward hydrothermal method to convert phosphogypsum into porous calcium silicate hydrate (P-CSH), which was then used to remove and recover Pb(II) and Cd(II) from wastewater. The adsorption capacities of P-CSH for Pb(II) and Cd(II) were notably high at 989.3 mg/g and 290.3 mg/g, respectively. The adsorption processes adhered to the pseudo-second-order kinetics model and the Langmuir isotherm model. Due to identical adsorption sites on P-CSH for both Pb(II) and Cd(II), competitive interaction occurred when both ions were present simultaneously. Additionally, the adsorption efficacy was minimally impacted by the presence of common coexisting cations in wastewater. The dominant mechanisms for removing Pb(II) and Cd(II) via P-CSH were chemical precipitation and surface complexation. Moreover, the adsorbed heavy metals were efficiently separated and reclaimed from the wastewater through a stepwise desorption process. The primary components of the residue from stepwise desorption were quartz and amorphous SiO₂. Following dissolution via pressurized alkaline leaching, this residue could be recycled for synthesizing P-CSH. This research offered a new strategy for the resourceful use of phosphogypsum and heavy metal wastewater. Full article

Pyrene derivatives are regularly proposed for use in biochemistry as dyes due to their photochemical characteristics. Their antibacterial properties are, however, much less well understood. New complexes based on 4-[(E)-2-(1-pyrenyl)vinyl]pyridine (PyPe) have been synthesized with metal ions that are known to possess antimicrobial properties, such as zinc(II), cadmium(II), and mercury(II). The metal ion salts, free ligand, combinations thereof, and the coordination compounds themselves were tested for their antibacterial properties through microdilution assays. We found that the ligand is able to modulate the antibacterial properties of transition metal ions, depending on the complex stability, the distance between the ligand and the metal ions, and the metal ions themselves. The coordination by the ligand weakened the antibacterial properties of heavy metal ions (Cd(II), Hg(II), Bi(III)), allowing the bacteria to survive higher concentrations thereof. Mixing the ligand and the metal ion salts without forming the complex beforehand enhanced the antibacterial properties of the cations. Being non-cytotoxic itself, the ligand therefore balances the biological consequences of heavy metal ions between toxicity and therapeutic weapons, depending on its use as a coordinating ligand or simple adjuvant. Full article

With the development of industrial activities and the agricultural and mining industries, farmland soils are facing serious problems related to heavy metal contamination, especially cadmium (Cd) and arsenic (As) contamination. In this study, two industrial by-products, phosphogypsum (PG) and red mud (RM), were modified by lanthanum (La) impregnation to form a new composite (L-PR) to investigate the adsorption performance of Cd(II)/As(V) in both single and binary systems. The adsorption mechanisms of Cd(II)/As(V) on L-PR were analyzed using SEM, XRD, FTIR, and XPS. The passivation effect of L-PR on the Cd-As composite contaminated soil was confirmed through a soil cultivation experiment. The adsorption experiments revealed that L-PR showed superior adsorption capabilities for Cd(II) and As(V) compared to PG and RM. Additionally, L-PR was found to be less affected by changes in pH. The kinetic studies indicated that Cd(II) and As(V) adsorption by L-PR followed the second-order kinetic model most accurately. Isothermal adsorption experiments revealed that the adsorption of Cd(II) by L-PR was more in accordance with the Freundlich model, while As(V) was more in accordance with the Langmuir model. The mechanisms of Cd(II) and As(V) adsorption on L-PR involved electrostatic attraction, ion exchange, complexation, and precipitation. The adsorption of Cd(II) is dominated by complexation and precipitation, and the adsorption of As(V) is dominated by ion exchange and complexation. Soil cultivation experiments showed that L-PR significantly reduced the available Cd and As concentrations in soil by 86.01% and 27.80%, respectively, and it could induce the transformation of non-stable Cd(II)/As(V) to the more stable residual. In summary, L-PR exhibits facile preparation, excellent adsorption performance, and is capable of simultaneously removing Cd(II) and As(V) from aqueous solutions while immobilizing these contaminants in soil. These remarkable attributes made it a highly promising alternative for the simultaneous treatment of various toxic metal contaminants. Full article

The coordination chemistry of 2-pyridyl ketoximes continues to attract the interest of many inorganic chemistry groups around the world for a variety of reasons. Cadmium(II) complexes of such ligands have provided models of solvent extraction of this toxic metal ion from aqueous environments using 2-pyridyl ketoxime extractants. Di-2-pyridyl ketone oxime (dpkoxH) is a unique member of this family of ligands because its substituent on the oxime carbon bears another potential donor site, i.e., a second 2-pyridyl group. The goal of this study was to investigate the reactions of cadmium(II) halides and dpkoxH in order to assess the structural role (if any) of the halogeno ligand and compare the products with their zinc(II) analogs. The synthetic studies provided access to complexes {[CdCl₂(dpkoxH)∙2H₂O]}_n (1∙2H₂O), {[CdBr₂(dpkoxH)]}_n (2) and {[CdI₂(dpkoxH)]}_n (3) in 50–60% yields. The structures of the complexes were determined by single-crystal X-ray crystallography. The compounds consist of structurally similar 1D zigzag chains, but only 2 and 3 are strictly isomorphous. Neighboring Cd^II atoms are alternately doubly bridged by halogeno and dpkoxH ligands, the latter adopting the η¹:η¹:η¹:μ (or 2.0111 using Harris notation) coordination mode. A terminal halogeno group completes distorted octahedral coordination at each metal ion, and the coordination sphere of the Cd^II atoms is {Cd^II(η¹ − X)(μ − X)₂(N_pyridyl)₂(N_oxime)} (X = Cl, Br, I). The trans-donor–atom pairs in 1∙2H₂O are Cl_terminal/N_oxime and two Cl_bridging/N_pyridyl; on the contrary, these donor–atom pairs are X_terminal/N_pyridyl, X_bridging/N_oxime, and X_bridging/N_pyridyl (X = Br, I). There are intrachain H-bonding interactions in the structures. The packing of the chains in 1∙2H₂O is achieved via π-π stacking interactions, while the 3D architecture of the isomorphous 2 and 3 is built via C-H∙∙∙C_g (C_g is the centroid of one pyridyl ring) and π-π overlaps. The molecular structures of 1∙2H₂O and 2 are different compared with their [ZnX₂(dpkoxH)] (X = Cl, Br) analogs. The polymeric compounds were characterized by IR and Raman spectroscopies in the solid state, and the data were interpreted in terms of the known molecular structures. The solid-state structures of the complexes are not retained in DMSO, as proven via NMR (¹H, ¹³C, and ¹¹³Cd NMR) spectroscopy and molar conductivity data. The complexes completely release the coordinated dpkoxH molecule, and the dominant species in solution seem to be [Cd(DMSO)₆]²⁺ in the case of the chloro and bromo complexes and [CdI₂(DMSO)₄]. Full article