Residual Metal Research Articles

Borenium-Catalyzed "Boron Walking" for Remote Site-Selective Hydroboration.

Remote functionalization through progressive olefin isomerization enables site-selective modification at a distal position, diversifying the synthetic approaches. However, the developed protocols have long relied on transition metal catalysis. Transition metal catalysts are deemed irreplaceable, albeit facing challenges in metal residue and catalyst poisoning. In this work, we present a pioneering approach that employs a borenium ion as a catalyst for site-selective, remote borylation, eliminating the need for metal catalysts. As the reaction progresses, borylation isomers at different positions emerge, gradually and ultimately converging into the predominant α-borylation product. This process is akin to a "walking" of a boron moiety along a carbon skeleton toward an aryl terminus. Detailed mechanistic studies and DFT calculations substantiate the borenium-catalyzed, stepwise migration via a reversible B-H insertion/elimination sequence. This remote borylation exhibits good functional group compatibility, complementing those methods reliant on transition metals. Furthermore, this metal-free protocol permits the convenient synthesis of silyl-remote-boryl compounds, demonstrating an opposite regioselectivity to that observed in transition-metal-catalyzed tandem silylation-borylation reactions. This discovery therefore contributes to site-selective, remote difunctionalization via sequential C-B and C-Si derivatizations, exemplified by the synthesis of amino-remote-alcohol bioactive molecules.

Heavy metal phytoremediation potential of Cosmos bipinnatus for use in chromium-contaminated regions of Dravyavati River, Jaipur, Rajasthan, India.

Due to their toxicity and permanence, heavy metals pose a significant threat as pollutants. Metals leach into soil from human activities including mining, manufacturing, and farming. Phytoremediation involves removing contaminants from soils using herbaceous plants and trees; it is a cost-effective, non-invasive, and aesthetically pleasing technique. The current research investigated the phytoremediation capacity of Cosmos bipinnatus in soil that had been polluted with chromium (Cr) along the Dravyavati River in Jaipur. The plant uptake of heavy metals was studied for 20, 40, 60, and 80 days of growth in pot and field experiments using atomic absorption spectrophotometry (AAS) to analyze residual heavy metal concentrations in the plant's shoots and roots. Chromium exhibited variation in total absorption by plants depending on the type of treatment. Using the translocation factor, it was observed that after 80 days in Nala soil 80% + wheat husk 20% (H2), the plant's capacity to absorb Cr was equivalent and considerably higher. Nola soil 80% + wheat husk 20%; H2, and Nala soil 70% + wheat husk 30%; H3 were among the treatments with TFs more than 1; however, the BCF values were all lower than 1. Additionally, root uptake was greater than shoot uptake. Thus, at H3 and H2 treatments, C. bipinnatus was determined to be an efficient phytoextractor for Cr, but at other concentrations, it acted as an excluder.

Exploring the catalytic performance of recyclable zinc indium sulfide in polymer synthesis: Well-controlled photoATRP of acrylates

Zinc indium sulfide has been used as a heterogeneous recyclable photocatalyst in visible light-induced atom transfer radical polymerization (ATRP). The photocatalyst was found to catalyze ATRP via an oxidative quenching mechanism without any additives. Polymers in high conversion and good control can be obtained. The kinetic study, light on/off experiment and the block copolymer synthesis showed the “living”/controlled nature of the polymerization. The photocatalyst can be reused for five times without obvious loss of control in the polymerization. Metal residue was not detected in the resulting polymers. This strategy provides a noval way for well-controlled polymer synthesis using recyclable visible light photocatalysis.

Coagulative removal of polyethylene microplastics using polyaluminum chloride in conjunction with laminarin

As emerging pollutants in water, microplastics pose potential risks to aquatic organisms and human health. Previous studies have shown that traditional metal coagulants are effective in removing microplastics from water, but they come with drawbacks such as high chemical dosage and metal residues. Therefore, it is important to explore more efficient coagulation systems. This study utilized laminarin (LA) as a coagulant aid in combination with polyaluminum chloride (PAC) to investigate its enhanced coagulation performance on polyethylene microplastics in water. The performance of coagulation systems for the removal of microplastics was evaluated for different agent dosages, pH, anion and HA content. Experimental results demonstrated that the compounded system (PAC-LA) significantly improved the removal efficiency of PE microplastics compared to the single PAC system, achieving a removal rate of 91.5% while reducing the dosage of PAC. The enhanced coagulation mechanism of LA was analyzed using various techniques including scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and zeta potential analysis. The results indicated that charge neutralization and sweep flocculation were the primary coagulation mechanisms in the presence of PAC alone. The effect of charge neutralization and adsorption was strengthened with the introduction of LA. The coagulation system of PAC-LA showed higher removal rates of PE microplastics under different environmental conditions such as varying pH levels, co-existing anions, and humic acid, suggesting a promising application for microplastic control in water.

Two-step process to recover metal and mineral residues from municipal solid waste incinerated (MSWI) ashes

The utilization potential of mineral fractions after metal recovery from fly ash and air pollution control residues from a municipal solid waste incineration plant was studied. Chemical leaching using acidic (H2SO4), and alkaline (NaOH) solutions was applied for metal recovery from fly ash and air pollution control residues from a municipal solid waste incineration plant. Subsequently, the feasibility of recycling both untreated and treated samples in cementitious materials was evaluated. This study aims to investigate the influences of chemical leaching on the structures and properties of MSWI residues as well as examine the utilization potential in cementitious materials of mineral residues after leaching, and their environmental risk. The use of acidic and alkaline leachants had good efficiency in critical metal recovery and unvalued/hazardous metal removal: 99 % of As, 72–80 % of Cd, 47–60 % of Zn, Cu, Co or Mn. After leaching, the chemical composition, physical properties, and mineralogical phases of the incinerated residues were substantially modified. The postleaching mineral residues showed potential for use in supplementary cementitious materials with enhanced reactivity and control of hydration kinetics. The compressive strength of cement pastes using 20 % of MSWI residues can obtain 14 MPa after 7 days. Detrimental impacts from potential toxic elements in incinerated residues can be alleviated through chemical leaching.

Study on toxicity responses in Xenopus tropicalis long-term exposure to norfloxacin, oxytetracycline and arsenic

The presence of residues of antibiotics and heavy metals in the global aquatic environment is a widespread potential environmental risk. Here, we studied their effect on Xenopus tropicalis by analysing the hepatotoxic effects of norfloxacin (NOR), oxytetracycline (OTC), and arsenic (As) on its histology, lipidomics, proteases, and cytokines. The results showed that development was inhibited, and additional vacuolation, sinusoids, pyknosis, nuclei, cell lysis, and leukocyte infiltration were observed in the liver after 72 days of exposure to NOR (0.1–4.0 mg L−1), OTC (0.1–4.0 mg L−1), and/or As (0.3–3.5 μg L−1). In addition, the size and number of lipid droplets increased with the superposition of drugs, disrupting lipid droplet homeostasis. Lipidomics proved that the intensity of lipid responses related to lipid metabolism was disrupted, especially for CerP and TAG. In addition, the lipotoxicity induced by joint exposure was more potent than that induced by a single exposure. Compared with the controls, the ROS levels in the liver were 7.21%–37.18% greater, which promoted oxidative stress damage. By revealing the underlying mechanisms involved, we found that the liver can resist oxidative stress and lipid peroxidation by regulating the expression of multiple cytokines. Our study provides new insights into the hepatotoxicity and underlying mechanisms in aquatic amphibians caused by long-term exposure to low concentrations of NOR, OTC, and/or As.

Action plan strategies for a new approach to the combination of yeast and ultrasonic waves for the reduction of heavy metal residues in rice

This study was conducted to combine two physical (ultrasonic) and biological (Saccharomyces cerevisiae) methods to reduce heavy metals such as Arsenic (As), Cadmium (Cd), and Lead (Pb) in rice, which is the most widely consumed grain. The concentrations of As, Cd, and Pb were found to be significantly affected after different treatments, were on uncooked rice samples (R1-R9): As R9 (2.05 ± 0.01) Cd R1, R3, R5, R8 (1.20 ± 0.01), Pb R6 (3.04 ± 0.173) (µgkg− 1) and in cooked rice samples were (C1-C10): As C10 (0.35 ± 0.27) Cd C9, C10 (1.00 ± 0.02), Pb C1 (3.52 ± 0.17) (µgkg− 1). The results showed that using ultrasound treatment combined with yeast (C10) had the greatest effect on reducing As among all treatments. In addition, C9, and C10 treatments were effective in reducing Cd concentration in cooked rice samples, and R6 treatment was effective in reducing Pb concentration in uncooked samples. The rice’s thermal qualities and specific textural traits were also affected by some or all of these treatments. The samples with modified particle sizes had the greatest sensory evaluation scores (C9). Moreover, sensory evaluation results showed that a specific treatment combining yeast and ultrasound (C3) maintained good sensory qualities and did not negatively affect the sensory qualities without sacrificing texture. Overall, this approach provides a promising method for the reduction of heavy metals in rice. A combination of biological and physical treatments can be used to reduce the heavy metals content (As, Cd, Pb) in rice. Stakeholders can use the aforementioned actions to optimize heavy metal content in the food chain, which requires the support of policymakers to promote public health.

Evaluating the productivity of five forages for the phytoremediation of heavy metal-contaminated land

Post-tin mining land holds promise for cultivating forage crops, with the potential to address Pb metal contamination through plant-based phytoremediation. However, the presence of heavy metals and depleted soil fertility resulting from tin mining activities may pose challenges to plant productivity and contribute to residual heavy metal accumulation. This study aims to assess the productivity and phytoremediation capacity of Pb by various grass species on reclaimed mining land. Using a randomised block design with three replications, the study was conducted over a four-year period in a post-mining area in Central Bangka Regency, Indonesia. Three grass species: Megathyrsus maximus (‘Riversdale’ and ‘Purple guinea’), Pennisetum purpureum (‘Taiwan’ and ‘Mott’), and Chrysopogon zizanioides were evaluated for forage production, quality, digestibility, and heavy metal content. It was shown that ‘Riversdale’ and ‘Purple guinea’ cultivars had relatively stable production for over four years, with the crude protein content of all grass types remaining relatively low (<6%), apart from ‘Mott’ cultivar, which had a crude protein content of 10%. The Pb concentration in the plants remained below the permitted limits for ruminants. In the post-tin mining site, ‘Riversdale’ and ‘Purple guinea’ cultivars showed potential for development. It is concluded that mined land can be replanted with forage crops for phytoremediation purposes. ‘Purple guinea’ and ‘Riversdale’ cultivars emerge as potential livestock feed sources on ex-mining land due to their four-year productive stability and low lead (Pb) concentration in their shoots, which falls below the safe threshold for cattle.

Uniform Polymer Microspheres by Photoinduced Metal-Free Atom Transfer Radical Precipitation Polymerization.

Herein, a photoinduced method is introduced for the synthesis of highly cross-linked and uniform polymer microspheres by atom transfer radical polymerization (ATRP) at room temperature and in the absence of stabilizers or surfactants. Uniform particles are obtained at monomer concentrations as high as 10% (by volume), with polymers being exempt from contamination by residual transition metal catalysts, thereby overcoming the two major longstanding problems associated with thermally initiated ATRP-mediated precipitation polymerization. Moreover, the obtained particles have also immobilized ATRP initiators on their surface, which directly enables the controlled growth of densely grafted polymer layers with adjustable thickness and a well-defined chemical composition. The method is then employed successfully for the synthesis of molecularly imprinted polymer microspheres.

An infrared radiation-responsive high-entropy CoCaMgMnAlFe-LDHs for controllable hydrogen generation via NaBH4 hydrolysis: Utilization of steel slag and lithium-ion battery liquid waste

Green processing of steel slag and lithium-ion battery liquid waste poses a global environmental challenge. This study utilizes waste acid (containing Co2+, H+ and NO3–) and alkali solutions (containing Li+, Na+, OH– and CO32–) from lithium-ion battery manufacturing to recover metal cations from steel slag (containing Ca2+, Mg2+, Al3+, Fe3+, and Mn2+), preparing high-entropy CoCaMgMnAlFe-LDHs catalysts for controllable hydrogen generation via NaBH4 hydrolysis. The ultimate residue, without any residual hazardous metal cations, enabling safe reintroduction into the natural environment. The presence of Co2+ endows the CoCaMgMnAlFe-LDHs catalyst with rapid photo-thermal conversion capability, enabling it to rapidly heat up under infrared radiation and efficiently catalyze the reaction of NaBH4 hydrolysis. The hydrogen generation rate reaches 1.12 mol·h−1·g−1·W−1 driven by 1050 nm infrared radiation. This study provides a novel approach to the environmentally friendly treatment and high-value utilization of steel slag and lithium-ion battery liquid waste.

Wood Polymer Composites Based on the Recycled Polyethylene Blends from Municipal Waste and Ethiopian Indigenous Bamboo (Oxytenanthera abyssinica) Fibrous Particles Through Chemical Coupling Crosslinking.

Valorization of potential thermoplastic waste is an effective strategy to address resource scarcity and reduce valuable thermoplastic waste. In this study, new ecofriendly biomass-derived wood polymer composites (WPCs) were produced from three different types of recycled polyethylene (PE) municipal waste, namely linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), or high-density polyethylene (HDPE), and their blend with equal composition (33/33/33 by wt.%). Bamboo particle reinforcement derived from indigenous Ethiopian lowland bamboo (LLB), which had never been utilized before in a WPC formulation, was used as the dispersed phase. Before utilization, recycled LLDPE, MDPE, and HDPE were carefully characterized to determine their chemical compositions, residual metals, polycyclic aromatic hydrocarbons, and thermal properties. Similarly, the fundamental mechanical properties of the WPCs, such as tensile strength, modulus of elasticity, flexural strength, modulus of rupture, and unnotched impact strength, were evaluated. Finally, the thermal stability and interphase coupling efficiency of maleic-anhydride-grafted polypropylene (MAPP) were carefully investigated. WPCs formulated by melt-blending either of the recycled PEs or the blend of recycled PE with bamboo particles showed significant improvement due to MAPP enhancing interfacial adhesion and thermally induced crosslinking, despite inherent immiscibility. These results were confirmed using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The formulated WPCs may promote PE waste cascading valorization, offering sustainable alternatives and maximizing LLB utilization. Furthermore, comparison with well-known standards for polyolefin-based WPCs indicated that the prepared WPCs can be used as alternative sustainable building materials and related applications.

Refining habitat selection for sulfate-reducing bacteria: Evaluating suitability and adaptability for sulfate-metal wastewater treatment during anaerobic-to-aerobic transitions

Inoculating sulfate-reducing bacteria (SRB) habitats offers an eco-friendly method for treating sulfate-metal laden wastewater, characterized by high sulfate levels, low pH, and elevated heavy metals. This study optimizes source habitat selection of SRB by evaluating groundwater, sewage sludge, and lake sediment, focusing on their suitability and adaptability to aerobic-anaerobic transitions in industrial settings. Sewage sludge, with its slightly acidic pH, reducing environment, and high nutrient levels (Total organic carbon: 207.53 g kg−1, Total nitrogen: 47.12 g kg−1), provides robust SRB potential, as supported by its highest diversity index. However, heavy metals and polycyclic aromatic hydrocarbons pose application challenges. All habitats effectively reduced metal concentrations anaerobically, with Cu removal reaching 95%–99%, and groundwater achieved the highest chemical oxygen demand reduction (63.6%) aerobically. Sludge and sediment showed high biomass and extracellular polymeric substances (EPS) accumulation, while groundwater's nucleic acid-rich EPS enhanced metal immobilization, resulting in stable residual metal forms but with potential remobilization under oxidative conditions. Microbial analysis revealed that Proteobacteria and Firmicutes were key players during transitions, with the highest SRB abundance in groundwater. SRB composition varied across habitats, with Sedimentibacter (13.04%), Desulfovibrio (6.33%), and Desulfomonile (8.1%) dominating in groundwater, sludge, and sediment, respectively, during the anaerobic stage. Functional analysis highlighted sludge's persistence in sulfate reduction under aerobic conditions, while groundwater's limited nitrogen cycle involvement indicated broader biogeochemical limitations. Collectively, these findings highlight strengths and limitations of each habitat as SRB inoculum source, emphasizing the importance of tailored anaerobic-to-aerobic strategies for effective wastewater management.

Assessment of Quality parameters and Safety in Indigofera tinctoria L. (Avuri) Rootbark extract

Avuri (Indigofera tinctoria Linn) has widely been used for the treatment of poisonous bites, epilepsy, nervous disorders, bronchitis, dermatological disorders, and liver ailments in Indian traditional medicine. Extensive research has been made into the aerial extracts of this plant for medicine preparation. Despite being used in medicinal formulations, especially in the treatment of poisonous bites the root bark has been less studied. This study is the physiochemical and safety of methanolic extract of Avuri verpattai. Roots were excised from mature plants collected from the Hills of Palani, then the root bark was peeled and air-dried. Extraction was done in a Soxhlet apparatus using a methanolic extraction procedure. Further, the extracts were used for preliminary phytochemical, physiochemical analysis, and safety analysis like aflatoxin, pesticide residue, Microbial contamination, and heavy metals. The phytochemical analysis showed the presence of alkaloids, flavanoids, steroids, triterpenoids, coumarin, phenol, tannin, saponin, sugar and betacyanin. The physiochemical tests conducted on the root bark extract unveiled specific parameters: pH(4.73), Total ash (3.59% w/w), acid insoluble ash (0.4751% w/w), loss on drying at 105°C(3.45% w/w), water-soluble extractive (8.74%w/w), and alcohol soluble extractive (1.91% w/w). The bulk density was 0.2496g/ml, while the tapped density was determined as 0.4940g/ml for the extracts. Safety assessment conducted via aflatoxin analysis, microbial contamination, and pesticide residues, indicated the absence of such toxins in the extract. Additionally, trace amounts of heavy metals mercury and arsenic were detected at levels of 0.334 and 1.970ppm, respectively. The study reveals that the Methanolic extract of Avuri verpattai has significant quality and safety. Consequently, these parameters can serve in the study of Avuri verpattai Extract, as an important Siddha medicinal preparation.

The curious case of the Dana platypus and what it can teach us about how lead shotgun pellets behave in fluid preserved museum specimens and may limit their scientific value.

Fluid preserved animal specimens in the collections of natural history museums constitute an invaluable archive of past and present animal diversity. Well-preserved specimens have a shelf-life spanning centuries and are widely used for e.g. anatomical, taxonomical and genetic studies. The way specimens were collected depended on the type of animal and the historical setting. As many small mammals and birds were historically collected by shooting, large quantities of heavy metal residues, primarily lead, may have been introduced into the sample in the form of lead shot pellets. Over time, these pellets may react with tissue fluids and/or the fixation and preservation agents and corrode into lead salts. As these chemicals are toxic, they could constitute a health issue to collection staff. Additionally, heavy element chemicals interfere with several imaging technologies increasingly used for non-invasive studies, and may confound anatomical and pathological investigations on affected specimens. Here we present a case-study based on platypus (Ornithorhynchus anatinus) and other small mammals containing lead pellets from the collection of The Natural History Museum of Denmark.

Robust Catalytic SEAr H/D Exchange of Arenes with D2O: Metal‐Free Deuteration of Natural Complexes and Drugs

AbstractA catalytic metal‐free approach for the H/D exchange in aromatic compounds using D2O as the terminal deuterating reagent has been developed. This metal‐free protocol employs a triaryl carbenium as the mediator and showcases a wide applicability in the late‐stage deuteration of various natural products and small‐molecule drugs. Gram‐scale deuteration was successfully demonstrated with β‐Estradiol, highlighting the method‘s practicability. Detailed mechanistic insights, supported by DFT calculations, unveiled the essential role of in situ generated acidic species in this electrophilic aromatic substitution process. This newly developed method offers a sustainable and versatile alternative to traditional metal‐catalyzed H/D exchange techniques, addressing challenges such as the use of expensive metals, impurity formation, and the necessity for residual metal removal from the final products.

Robust Catalytic SEAr H/D Exchange of Arenes with D2O: Metal-Free Deuteration of Natural Complexes and Drugs.

A catalytic metal-free approach for the H/D exchange in aromatic compounds using D2O as the terminal deuterating reagent has been developed. This metal-free protocol employs a triaryl carbenium as the mediator and showcases a wide applicability in the late-stage deuteration of various natural products and small-molecule drugs. Gram-scale deuteration was successfully demonstrated with β-Estradiol, highlighting the method's practicability. Detailed mechanistic insights, supported by DFT calculations, unveiled the essential role of in situ generated acidic species in this electrophilic aromatic substitution process. This newly developed method offers a sustainable and versatile alternative to traditional metal-catalyzed H/D exchange techniques, addressing challenges such as the use of expensive metals, impurity formation, and the necessity for residual metal removal from the final products.

Activation of periodate by CNT for selective catalytic oxidation: The overlooked significant role of residual metal species as catalytic sites

Carbon nanotubes (CNTs) catalyzed activation of peroxides has been extensively investigated, while the role of residual metal species in CNT in the catalysis is largely overlooked. In the study, calcination treatment of pristine CNT at high temperatures was employed as an approach to gain an insight into the role of residual metal species as catalytic sites in promoted catalytic activation of periodate (PI). Firstly, the calcination treatment at 500–1100 °C significantly promoted PI activation by calcined CNT. By constructing the quantitative structure–activity relationships (QSARs) between several surface and bulk properties of CNT (such as total surface oxygen content, surface carbonyl group, bulk defect and residual metal species) and PI activation performance, the residual metal species were identified as the catalytic sites. Moreover, the purification method of pristine CNT in the concentrated HNO3 was confirmed to be not efficient to remove these residual metals. The calcination treatment can tune the electronic structure of residual metal species, and promote their exposure and electron donation capacity for PI activation, thus significantly improving PI activation performance. Moreover, IO3• was identified as the dominant reactive species in CNT/PI system via a line of approaches including quenching experiments, PI decomposition in the presence/absence of organic pollutants, electrochemical testes, high selectivity in degradation of organic pollutants, QSARs of substituted phenols, and analysis of degradation products of 4-bromophenol. Furthermore, the CNT/PI system exhibited a wide pH application range of 3–11, high anti-interference to bicarbonate, chloride and phosphate in water. The study advances the understanding on the residual metal species in CNT and its overlooked catalytic role in PI activation, and also provides a high-performance oxidation process for wastewater purification.

In Situ Formation of Stable Dual-Layer Solid Electrolyte Interphase for Enhanced Stability and Cycle Life in All-Solid-State Lithium Metal Batteries.

All-solid-state lithium metal batteries have emerged as a promising solution to overcoming the energy density and safety challenges associated with conventional lithium-ion batteries. Solid polymer electrolytes, particularly those based on poly(vinylidene fluoride) (PVDF) and dimethylformamide (DMF), demonstrate significant potential. However, interfacial side reactions between residual DMF solvents and lithium metal present substantial challenges. In this study, we investigate the in situ formation of solid electrolyte interphase protective layers to mitigate these side reactions. By incorporating F-rich additives, such as fluoroethylene carbonate and lithium difluorophosphate, we successfully establish a dual-layer inorganic SEI structure characterized by an outer LiF layer and an inner Li2O layer. Consequently, our approach extends the cycle life of lithium symmetric batteries to 3000 h. Additionally, the Li||LiFePO4 solid-state battery demonstrates exceptional stability, enduring 400 cycles at a 1C rate with an impressive capacity retention of 84%. This strategic methodology effectively leverages the benefits of residual solvents, ensuring both enhanced battery efficiency and long-term operational stability for PVDF-based all-solid-state lithium metal batteries.

Cross-jurisdictional analysis and forecasting of North American nuclear fuel inventory using a standardized unit

This study fills the noted gap in comparative analyses of spent nuclear fuel (SNF) by assessing inventories from two key nuclear power regions, the USA and Canada, using a comprehensive analytical framework and standardized data from 2009 to 2021. In the USA, SNF inventory increased by 14.7 % in fuel assembly weight and 47 % in residual heavy metal content compared to Canada, in line with their use of light water reactors. Canada's SNF production is directly correlated to its nuclear power output, influenced by the lower burnup of natural uranium fuel used in CANDU reactors (R2 = 0.57; p-value < 0.05) while the USA shows insignificant correlation, likely due to a variety of reactor types and higher burnup rates (R2 = 0.008; p-value > 0.05). Further, the study identifies a strong negative correlation between uranium mine production and SNF inventory in the USA, indicating a reliance on imports amidst negligible domestic mining. In contrast, Canada also exhibits moderate negative dependency due to its position as a major uranium exporting jurisdiction. The obtained negative correlations with coal rents in both countries indicate a shift towards more nuclear energy use, impacting economic growth and energy patterns. The developed predictive models indicate a higher future SNF increase in Canada than in the USA. These findings are essential for planning the transition from temporary to permanent SNF disposal, ensuring safe long term management of radioactive waste.

Synergistic removal of malachite green and Cr(Ⅵ) using ethylenediamine disuccinic acid functionalized silica gel

As common industrial raw materials, malachite green (MG) and Cr(Ⅵ) generally coexist in waste liquids discharged from the paper printing, leather, and textile industries, causing serious harm to humans and the environment. Therefore, developing an effective method for the synergistic removal of MG and Cr(Ⅵ) from aquatic environments is of great research value. In this work, the non-homogeneous Fenton-like catalysts, namely, EDDS-Silica and EDDS-Co2+-Silica were successfully prepared using ethylenediamine disuccinic acid (EDDS) and silica gel (Silica) as raw materials, and a non-homogeneous Fenton-like catalytic method was developed for the efficient and synergistic removal of MG and Cr(Ⅵ) from wastewater. EDDS-Silica and EDDS-Co2+-Silica were analyzed using Fourier infrared spectroscopy and X-ray photoelectron spectroscopy to determine their structural composition and elemental contents. The catalytic degradation and removal effects of these materials in an MG single-waste system were also investigated. The results demonstrated that the incorporation of both materials can overcome the limitation of the conventional Fenton reaction, which is its applicability to acidic environments only. Moreover, EDDS-Co2+-Silica showed better degradation effects on MG than EDDS-Silica. Quantitative calculations based on density functional theory were used to predict the optimal coordination forms between Co2+and EDDS-Silica as well as the MG structure. The lowest unoccupied and highest occupied molecular orbitals of the catalysts were then used to predict the active sites on which MG tends to capture or release electrons during the degradation reaction. The optimal conditions for the synergistic removal of MG and Cr(Ⅵ) from a binary system using EDDS-Co2+-Silica were further investigated under different influencing factors. The results showed that EDDS-Co2+-Silica still had excellent catalytic effect on the degradation rate of MG in the range of pH 3-7, and the optimal conditions were as follows: solution pH, 7; degradation time, 1 h; temperature, 25 ℃; H2O2 concentration, 20 mmol/L; and the initial mass concentration of Cr(Ⅵ), 25 mg/L. Under the above conditions, the degradation rate was increased from 87.25% to 96.67% compared with that in the MG monosystem. Obvious enhancements in degradation effect and efficiency confirmed that the incorporation of EDDS-Co2+-Silica was favorable for the synergistic removal of MG and Cr(Ⅵ) in the binary system. Strongly oxidizing Cr(Ⅵ) can participate in the Fenton reaction, thus promoting MG degradation over a wide pH range. Thus, a positive synergistic effect exists between MG and Cr(Ⅵ). Considering that a large number of metal ions remained in the solution after the degradation reaction, EDDS-Silica was added to the degradation solution, and adsorption experiments were performed for 4 h at 30 ℃to adsorb and remove Cr and Fe via the strong chelating property of EDDS. The total residual mass concentrations of Cr and Fe were 4.96 and 1.02 mg/L, respectively, which meet national emission standards. These findings indicate that EDDS-Silica has good effects on the removal of residual metal ions after the nonhomogeneous Fenton reaction. As heterogeneous Fenton-like catalysts, the aminopolycarboxylic acid-modified materials proposed in this study can simultaneously promote the Fenton reaction and remove residual metal ions, thereby effectively removing MG and Cr(Ⅵ) from the binary system while ensuring that the content of residual metal ions in the system meets environmental emission standards. This study has broad application prospects in dye degradation and heavy-metal-ion wastewater treatment, and provides a reference value and theoretical basis for the development of other similar ligand-modified materials.