Highly efficient removal of thallium in wastewater by MnFe2O4-biochar composite

Adsorptive behavior of thallium using Fe3O4-kaolin composite synthesized by a room temperature ferrite process

Thallium (Tl) contaminants pose serious threats to the ecological environment and human health due to its acute/chronic poisoning on the health of most organisms even at low concentrations. To find a rapid and efficient technology in removing Tl from waters thus becomes a crucial issue. A magnetic Fe₃O₄-kaolin composite (denoted by FKC) with high specific surface area (133.7 m²/g) was successfully synthesized via a simple and low-cost technique for Tl(I) removing from various water media. The HRTEM images confirmed the existence of lattice fingers Fe₃O₄ and displayed that a large number of Fe₃O₄ nanoparticles dispersed on the surface of kaolin sheets. Compared with kaolin or Fe₃O₄ alone, FKC enhanced obviously the adsorption rate and capacity of Tl(I) over a wide pH range (4.5-9.0). The maximum adsorption capacity of FKC for Tl(I) was 19,347 mg/kg (calculated by Langmuir model), which was almost one hundred times and two times higher than those of kaolin and Fe₃O₄, respectively. Importantly, FKC was observed to have a great potential in removing Tl(I) from surface water, groundwater, and tap water in more alkaline conditions. By applying the external magnetic field, FKC could be recovered efficiently (99%) and rapidly (20 s). Moreover, Tl L₃-edge XANES spectra revealed that Tl(I) was adsorbed on the FKC and would not be converted to more toxic Tl(III). The cations (CaCl₂, NaCl, and KCl) and the ionic strength with concentrations of 0.001-1.0 mol/L showed a great influence on the adsorption of Tl(I) by FKC, implying that this adsorption was dominated by outer-sphere surface complexation at investigated pH values. The information provided is essential for designing a rapid and effective scavenger for removing Tl in various natural waters.

Thermochemical conversion of heavy metal contaminated biomass: Fate of the metals and their impact on products

With the rapid depletion of fossil energy and increasingly severe environmental pollution, the development of biomass resources for biorefineries has become a new research focus. However, heavy metals may be released during the thermochemical treatment when the biomass materials used in biomass conversion are contaminated by heavy metals. This can cause secondary environmental pollution or transference to the target products, reducing product quality. Therefore, having a systematic understanding of the fate of heavy metals in biomass conversion is necessary for alleviating potential risks. This study presents the current status of contaminated biomass and conversion products involving thermochemical processes, the migration, transformation, and impact of heavy metals in biomass conversion was investigated, and the utilization of heavy metals in contaminated biomass was briefly outlined. This review aims to link biomass conversion to the fate of heavy metals, avoid existing risks as much as possible to produce cleaner products efficiently, and promote the sustainable development of heavy metal contaminated biomass resources.

Unexpected enrichment of thallium and its geochemical behaviors in soils impacted by historically industrial activities using lead‑zinc carbonate minerals

Thallium is a trace metal with severe toxicity. Contamination of thallium (Tl) generated by steel and non-ferrous metals industry is gaining growing concern worldwide. However, little is known on Tl contamination owing to industrial activities using carbonate minerals. This study revealed abundant geochemical mobile/bioavailable Tl (> 65.7%, in average; mostly in oxidizable fraction) in soils from a carbonate-hosted PbZn ore utilizing area in China for the first time. Unexpected Tl enrichment was observed in soil accompanying with 3655, 7820, 100.1, 27.3 and 29.9 mg/kg (in average) of Pb, Zn, As, Cd and Sb, respectively. Characterization using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis further confirmed that historical industrial activities impose anthropogenic catastrophic effects on the local agricultural soil system. The ecological and health risk assessment of heavy metal(loid)s in soils proclaimed serious potential non-carcinogenic risks of Pb and V to adults, and Pb, Tl and As to children. Sequential extraction analysis showed that Tl, as well as Pb, Zn, Mn, Co, and Cd, mainly existed in the mobile fractions (exchangeable/acid-extractable, reducible and oxidizable), indicating an ecological risk of biological accumulation of multiple metal(loid)s in this area. These findings provide a theoretical basis for taking appropriate remediation measures in order to ensure safety of soils in such industrial areas likewise.

Recent advances in application of iron-manganese oxide nanomaterials for removal of heavy metals in the aquatic environment

Heavy metal pollution has a serious negative impact on the ecological environment and human health due to its toxicity, persistence, and non-biodegradable properties. Among the technologies applied in heavy metals removal, adsorption has been widely used as the most promising method because of its simple operation, high removal efficiency, strong applicability, and low cost. Iron-manganese oxide nanomaterials, as an effective absorbent, have attracted wide attention due to their simple preparation, wide material sources, and lower ecological impact. So far, no quantitative investigation has been conducted on the preparation and application of iron-manganese oxide nanomaterials in heavy metals removal. This review discussed the preparation methods and characteristics of iron‑manganese oxide nanomaterials over the past decade and provided some basic information for the improvement of preparation methods. The physicochemical properties of iron‑manganese oxide nanomaterials and environmental conditions are regarded as important factors that affect the removal efficiency of heavy metals. In addition, the removal mechanisms of heavy metals in aqueous solution with iron‑manganese oxide nanomaterials were mainly included redox, complex precipitation, electrostatic attraction, and ion exchange. The reusability and practicability in actual wastewater treatment of 3nganese oxide nanomaterials were further discussed. Several key problems still need to be solved in the existing progress, such as improving the ability and stability of the iron‑manganese oxide nanomaterials to remove heavy metals from actual wastewater. In conclusion, this review provides a future direction for the application of iron‑manganese oxide nanomaterials for heavy metals removal and even in the large-scale treatment of actual wastewater.

Recent Advances of Emerging Organic Pollutants Degradation in Environment by Non-Thermal Plasma Technology: A Review

Emerging organic pollutants (EOPs), including endocrine disrupting compounds (EDCs), pharmaceuticals and personal care products (PPCPs), and persistent organic pollutants (POPs), constitute a problem in the environmental field as they are difficult to completely degrade by conventional treatment methods. Non-thermal plasma technology is a novel advanced oxidation process, which combines the effects of free radical oxidation, ozone oxidation, ultraviolet radiation, shockwave, etc. This paper summarized and discussed the research progress of non-thermal plasma remediation of EOPs-contaminated water and soil. In addition, the reactive species in the process of non-thermal plasma degradation of EOPs were summarized, and the degradation pathways and degradation mechanisms of EOPs were evaluated of selected EOPs for different study cases. At the same time, the effect of non-thermal plasma in synergy with other techniques on the degradation of EOPs in the environment was evaluated. Finally, the bottleneck problems of non-thermal plasma technology are summarized, and some suggestions for the future development of non-thermal plasma technology in the environmental remediation were presented. This review contributes to our better understanding of non-thermal plasma technology for remediation of EOPs-contaminated water and soil, hoping to provide reference for relevant practitioners.

Thermodynamic and kinetic coupling modeling for thallium(I) sorption at a heterogeneous titanium dioxide interface

The transformations of monovalent thallium (Tl) in an aqueous environment may be affected significantly by Tl(I) partitioning at the solid-water interface during sorption. Models used to quantify the kinetics of Tl(I) adsorption on heterogeneous adsorbents and formation of multiple complexes under a wide range of water chemistry conditions can accurately predict the environmental fate of thallium. In this study, Tl(I) sorption on representative titanium dioxide at different solution pH values and loading concentrations was investigated with two unified adsorption models, diffuse layer modeling and kinetics modeling. Three Tl(I) surface complexes, TiOTl, TiOHTl⁺, and TiOTlOH^-, were used in the diffuse layer model and successfully described batch adsorption and the results of spectroscopic analyses. The contribution of TiOHTl⁺ to the adsorption capacity was much higher than those of TiOTl and TiOTlOH^- under neutral and weakly alkaline conditions, while the species TiOTlOH^- predominated among Tl(I) complexes in strongly alkaline environments. The adsorption and desorption rate coefficients derived from thermodynamics and kinetics coupling modeling suggested the influence of different complex characteristics on adsorption and desorption of Tl(I). Our results provide a comprehensive model for predicting the dynamic binding behavior of Tl at heterogeneous solid-water interfaces.

The Use of Gigantochloa Bamboo-Derived Biochar for the Removal of Methylene Blue from Aqueous Solution

In this study, locally grown bamboo (Gigantochloa spp.) was used as feedstock for pyrolysis production of biochar under various pyrolysis temperatures (400–800°C). The resultant biochars were tested for their performance in adsorptive removal of the methylene blue (MB) dye. The scope of the adsorption experiment includes the effects of adsorbent dosage, solution pH, initial adsorbate concentration, and contact time. The adsorption data confirmed that pyrolysis temperature has a significant effect on adsorptive performance, whereas biochar pyrolysed at 500°C (BC500) has the highest adsorptive performance with the maximum adsorption capacity (derived from the Langmuir model) being 86.6 mg g-1. Basic characterisations (SEM, EDX, XRD, FTIR, and BET) were carried out for BC500 where FTIR and SEM confirmed the adsorption of MB onto the biochar, while the BET data showed the reduction of the BET surface area, total pore volume, and pore diameter after the adsorption process.

A comprehensive review on emerging trends in industrial wastewater research

Rapid industrialization is one of the intricate factors that is linked to the depletion of water resources and increased generation of wastewater. Due to various obstructions and impediments, such as ineffective treatment solutions, exorbitant prices, lack of basic amenities, insufficient financial assistance, and technical expertise, sustainable treatment of industrial effluents has become an onerous process in most parts of the world. The majority of current treatment solutions are conventional and outdated, and thus fall short to remove all the contaminants efficiently from the industrial wastewater. Moreover, poorly treated or untreated industrial effluents are indiscriminately dumped into water bodies such as lakes, ponds, and rivers, causing substantial health hazards to humans and animals and serious threats to the aquatic ecosystem. Thus, there is a need for highly efficient, cost-effective, and sustainable technologies for the treatment of industrial wastewater. Employment of microbial technologies such as microbial fuel cells and microalgal technologies, treatment of wastewater can be coupled with the production of bioelectricity and valuable biomass, respectively. Moreover, with nanofiltration and biochar technologies, the efficiency of the overall treatment procedure can be increased to a greater extent. The present review aims to highlight opportunities and challenges associated with some of the emerging trends in industrial wastewater research.

Adsorptive removal of pollutants from water using magnesium ferrite nanoadsorbent: a promising future material for water purification

Nanoadsorbents having large specific surface area, high pore volume with tunable pore size, affordability and easy magnetic separation gained much popularity in recent time. Iron-based nanoadsorbents showed higher adsorption capacity for different pollutant removal from water among other periodic elements. Spinel ferrite nanomaterials among iron-bearing adsorbent class performed better than single iron oxide and hydroxides due to their large surface area, mesoporous pore, high pore volume and stability. This work aimed at focusing on water treatment using magnesium ferrite (MgFe₂O₄) nanomaterials. Synthesis routes, properties and pollutant adsorption were critically investigated to explore the performance of magnesium ferrite in water treatment. Structural and surface properties were greatly affected by the factors involved in different synthesis routes and iron and magnesium ratio. Complete removal of pollutants through adsorption was achieved using magnesium ferrite. Pollutant adsorption capacity of MgFe₂O₄ and its modified forms was found several folds higher than Fe₂O₃ and Fe₃O₄ nanomaterials. In addition, MgFe₂O₄ showed strong stability in water than other pure iron oxide and hydroxide. Modification with graphene oxide, activated carbon, biochar and silica was demonstrated to be beneficial for enhanced adsorption capacity. Complex formation was suggested as a dominant mechanism for pollutant adsorption. These nanomaterials could be a viable and competitive adsorbent for diverse pollutant removal from water.

Stable isotope fractionation of thallium as novel evidence for its geochemical transfer during lead‑zinc smelting activities

Thallium (Tl) is a highly toxic trace metal. Lead (Pb)‑zinc (Zn) smelting, which is a pillar industry in various countries, is regarded as one of the dominant anthropogenic sources of Tl contamination in the environment. In this study, thallium isotope data have been evaluated for raw material and a set of industrial wastes produced at different stages of Pb-Zn smelting in a representative large facility located by the North River, South China, in order to capture Tl isotope signatures of such typical anthropogenic origin for laying the foundation of tracking Tl pollution. Large variations in Tl isotopic compositions of raw Pb-Zn ores and solid smelting wastes produced along the process chain were observed. The ε²⁰⁵Tl values of raw Pb-Zn ores and return fines are -0.87 ± 0.26 and -1.0 ± 0.17, respectively, contrasted by increasingly more negative values for electrostatic precipitator dust (ε²⁰⁵Tl = -2.03 ± 0.14), lime neutralizing slag (ε²⁰⁵Tl = -2.36 ± 0.18), and acid sludge (ε²⁰⁵Tl = -4.62 ± 0.76). The heaviest ε²⁰⁵Tl (1.12 ± 0.51) was found in clinker. These results show that isotopic fractionation occurs during the smelting processes. Obviously, the lighter Tl isotope is enriched in the vapor phase (-3.75 ε²⁰⁵Tl units). Further XPS and STEM-EDS analyses show that Tl isotope fractionation conforms to the Rayleigh fractionation model, and adsorption of ²⁰⁵Tl onto hematite (Fe₂O₃) may play an important role in the enrichment of the heavier Tl isotope. The findings demonstrate that Tl isotope analysis is a robust tool to aid our understanding of Tl behavior in smelting processes and to provide a basis for source apportionment of Tl contaminations.

Highly efficient removal of thallium(I) by facilely fabricated amorphous titanium dioxide from water and wastewater

In this study, amorphous hydrous titanium dioxide was synthesized by a facile precipitation method at room temperature, aiming to effectively remove thallium(I) from water. The titanium dioxide prepared using ammonia as precipitant (TiO2I) is more effective for thallium(I) uptake than the one synthesized with sodium hydroxide (TiO2II). The TiO2 obtained particles are amorphous, aggregates of many nanoparticles and irregular in shape. The thallium(I) uptake increases with the rise of solution pH value. Under neutral pH conditions, the maximal thallium(I) adsorption capacities of TiO2I and TiO2II are 302.6 and 230.3 mg/g, respectively, outperforming most of the reported adsorbents. The amorphous TiO2 has high selectivity towards thallium(I) in the presence of multiple cations such as K+, Ca2+, Mg2+, Zn2+ and Ni2+. Moreover, the TiO2I is efficient in removing thallium(I) from real river water and mining wastewater. Additionally, the spent TiO2I can be regenerated using hydrochloric acid solution and reused. The Tl(I) adsorption is achieved via replacing the H+ in hydroxyl group on the surface of TiO2 and forming inner-sphere surface complexes. Owing to its high efficiency, facile synthesis and environmental friendliness, the TiO2I has the potential to be used as an alternative adsorbent to remove Tl(I) from water.

Sustainable remediation of hazardous environmental pollutants using biochar-based nanohybrid materials

Biochar is a well-known carbon material with diversified functionalities and excellent physicochemical characteristics with high wastewater treatment potential. This review aims to summarize recent advancements in the development of biochar and biochar-based nanohybrid materials as a potential tool for the removal of harmful organic compounds such as synthetic dyes/effluents. The formation of biochar using pyrolysis of renewable feedstocks and their applications in various industries are explained hereafter. The characteristics and construction of biochar-based hybrid materials are explained in detail. Diversity of feedstocks, including municipal wastes, industrial byproducts, agricultural, and forestry residues, endows different biochar types with a wide structural variety. The production of cost-effective biochar drives the interest in manipulating biochars and induces desire functionality using nanoscale reinforcements. Various types of biochars, such as magnetic biochar, layered nanomaterial coated biochar, nanometallic oxide composites, chemically and physically functionalized biochar, have been produced. With the aid of nanomaterial, hybrid biochar exhibits a high potential to remove toxic contaminants. Depending upon biochar type, dyes/effluents can be removed via different mechanisms, including the Fenton process, photocatalytic degradation, π-π interaction, electrostatic interaction, and physical adsorption. In conclusion, desired physicochemical features, and tunable surface properties of biochar present high potential material in removing organic dyes and other effluents. The blended biochar with different materials/nanomaterials endows broader development and multi-functional opportunities for treating dyes/effluents.

Mn(II)-Mn(III)-Mn(IV) redox cycling inhibits the removal of methylparaben and acetaminophen mediated by horseradish peroxidase: New insights into the mechanism

Catalyzed oxidative coupling reactions mediated by enzyme have been proposed as an effective remediation strategy to remove micropollutants, however, little is known about how the Mn(II) redox cycling affects the horseradish peroxidase (HRP)-mediated reactions in wastewater treatment. Here, we explored the removal of two pharmaceuticals and personal care products (PPCPs), methylparaben (MeP) and acetaminophen (AAP), in HRP-mediated reaction system with dissolved Mn (II). It was found that the conversion rate of AAP was about 284 times higher than that of MeP, and Mn (II) significantly inhibited HRP-catalyzed MeP removal but had little influence on that of AAP. X-ray photoelectron spectroscopy (XPS) and theoretical calculations demonstrated that HRP converted Mn(II) into Mn(III), and then generated MnO₂ colloid, which inhibited the removal of the substrates. Moreover, the results of theoretical calculations also showed that the binding energy between HRP and Mn was 27.68 kcal/mol, which was higher than that of MeP (25.24 kcal/mol) and lower than that of AAP (30.19 kcal/mol). Therefore, when MeP and Mn (II) coexisted in the reaction system, HRP preferentially reacted with Mn(II), which explained the different impacts of Mn (II) on the removal of MeP and AAP. Additionally, Mn (II) significantly altered the product distribution by decreasing the amount of polymerization products. Overall, our work here revealed the roles of Mn (II) in the removal of MeP and AAP mediated by HRP, having strong implications for an accurate assessment of the influence of Mn(II) redox cycling on the removal of PPCPs in wastewater treatment.

Thallium geochemical fractionation and migration in Tl-As rich soils: The key controls

Thallium (Tl) pollution caused by mining and processing of Tl-enriched ores has become an increasing concern. This study explored the geochemical fractionation and vertical transfer of Tl in a soil profile (200 cm) from a representative Tl-As mineralized area, Southwest China. The results showed that the soils were heavily enriched by Tl and As, with concentration ranging from 3.91-17.3 and 1830-8840 mg/kg (6.79 and 2973 mg/kg in average), respectively. Approximately 50% of Tl occurred in geochemically mobile fractions in the topsoil, wherein the reducible fraction was the most enriched fraction. Further characterization using LA-ICP-MS and TEM revealed that enriched Tl and As in soils were mainly inherited from the weathering of mine tailing piles upstream. XPS characterization indicated that Fe oxides herein may play a critical role in the oxidation of Tl(I) to Tl(III) which provoked further adsorption of Tl onto Fe oxides, thereby facilitating Tl enrichment in the reducible fraction. The findings highlight that the pivotal role of Fe oxides from mineralized area in the co-mobility and migration of Tl and As in the depth profile.

New insights into ball milling effects on MgAl-LDHs exfoliation on biochar support: A case study for cadmium adsorption

Ball milling (BM) as a solvent-free technology has been widely used to tailor the biochar-based adsorbents with high porosity and well dispersion for enhancing their environmental applications. In this study, the ball-milled layered double hydroxides (LDHs) biochar composite (B-LDHs-BC) was successfully fabricated with BM method for Cd(II) adsorption and the BM effects on the LDHs-BC structure-performance relationships were investigated. The solid-state characterization demonstrated the LDHs were successfully exfoliated by BM on the B-LDHs-BC surface which was identified by the enlarged basal spacing and reduced crystallite size of the LDHs. Although the BET surface area of B-LDHs-BC (226 m²/g) was slightly lower than the ball-milled BC, the B-LDHs-BC had more O-containing functional groups and higher adsorption capacity (119 mg/g). The kinetics experiments indicated that the Cd(II) removal by B-LDHs-BC was through both the physical and chemical adsorption processes, and the liquid membrane diffusion was the rate-controlling step. The positive BM effects mainly induced more abundant acidic functional groups and active adsorption sites, and thus enhanced Cd(II) performance of B-LDHs-BC. This work demonstrated a facile solvent-free method for production of the exfoliated LDHs modified BC composite, and also well illustrated the BM effects which can extend their practical use in environment.

Escalating health risk of thallium and arsenic from farmland contamination fueled by cement-making activities: A hidden but significant source

Soil-to-vegetable migration of toxic metal(loid)s is a pivotal pathway of human exposure to chemical intoxication. Thallium (Tl) and arsenic (As) are highly toxic metal(loid)s but their co-occurrence in soils and vegetables remain poorly understood. Herein, the present study focuses on potential health risk arising from co-occurrence of TlAs in various common vegetables cultivated in different farmlands around an industrial area featured by cement production activities. The results reveal obvious co-contamination of Tl (2.28 ± 1.39 mg/kg) and As (102.0 ± 66.7 mg/kg) in soils. Fine particles bearing sulfide and other minerals associated with Tl and As are detected in fly ash from cement plant, which can be migrated by wind over a long distance with hidden but inevitable pollution. Bioaccumulation Factor (BCF) and Enrichment Factor (EF) show that taro and corn preferentially accumulate Tl especially in underground parts. Hazard Quotient (HQ) indicates that consumption of these vegetables may result in chronic poisoning and/or even carcinogenic risk. The study highlights that the pathway and high risk of co-contamination of TlAs in the nearby farmlands posed by cement-making activities should be highly concerned.

Activated low-grade phosphate rocks for simultaneously reducing the phosphorus loss and cadmium uptake by rice in paddy soil

Cadmium (Cd) pollution and phosphorus (P) leaching in paddy soils has raised the global concern. In this study, two kinds of the low grade phosphate rocks activated by the sodium lignosulfonate (SL) and humic acid (HA) were fabricated for soil Cd passivation and reduction of the soil P leaching simultaneously. The mechanisms of the Cd adsorption and passivation by the activated phosphate rocks (APRs) were investigated through the batch experiment and the indoor culture test (i.e., incubation and pot experiments) in the Cd-polluted paddy soil. The effects of the APRs on the potted rice growth, uptake of Cd by rice and P loss were also studied. In comparison with the superphosphate treatment, the cumulative P loss from SL- and HA-APRs were reduced by the 65.2% and 65.3%. In terms of the Cd passivation, the Cd adsorbed on the APRs was through the chemical ways (i.e., ligand exchange and the formation of internal complexes). The application of the APRs significantly decreased the soil exchangeable Cd by 48.9%-55.0%, while the Fe/Mn oxides-bound Cd and residual Cd increased significantly by 19.6%-20.3% and 50.7%-69.4%, respectively. Pot experiment also suggested that both the APRs treatments (SL- and HA-APRs) significantly diminished soil Cd accumulation in rice (by 72.7% and 62.8%) coupling with the significantly decreased P leaching. These results provide a sustainable way to explore a novel cost-effective, high-efficient and bi-functional mineral-based soil amendments for environmental remediation.

Geochemical and U-Th isotopic insights on uranium enrichment in reservoir sediments

Uranium (U) geochemistry and its isotopic compositions of reservoir sediments in U mine area were poorly understood. Herein, U and Th isotopic compositions were employed to investigate source apportionment and geochemical behavior of U in 41 reservoir sediments from a U mining area, Guangdong, China. The remarkably high contents of both total U (207.3-1117.7 mg/kg) and acid-leachable U (90.3-638.5 mg/kg) in the sediments exhibit a severe U contamination and mobilization-release risk. The U/Th activity ratios (ARs) indicate that all sediments have been contaminated apparently by U as a result of discharge of U containing wastewater, especially uranium mill tailings (UMT) leachate, while the variations of U/Th ARs are dominated by U geochemical behaviors (mainly redox process and adsorption). The U isotopic compositions (δ²³⁸U) showed a large variance through the sediment profile, varying from - 0.62 to - 0.04‰. The relation between δ²³⁸U and acid-leachable U fraction demonstrates that the U isotopic fractionation in sediments can be controlled by bedrock weathering (natural activity), UMT leachate (anthropogenic activity) and subsequent biogeochemical processes. The findings suggest that U-Th isotopes are a powerful tool to better understand U geochemical processes and enrichment mechanism in sediments that were affected by combined sources and driving forces.

Occurrence, potential ecological risks, and degradation of endocrine disrupter, nonylphenol, from the aqueous environment

Nonylphenol (NP) is considered a potential endocrine-disrupting chemical affecting humans and the environment. Due to widespread occurrence in the aquatic environment and neuro-, immuno, reproductive, and estrogenic effects, nonylphenol calls for considerable attention from the scientific community, researchers, government officials, and the public. It can persist in the environment, especially soil, for a long duration because of its high hydrophobic nature. Nonylphenol is incorporated into the water matrices via agricultural run-off, wastewater effluents, agricultural sources, and groundwater leakage from the soil. In this regard, assessment of the source, fate, toxic effect, and removal of nonylphenol seems a high-priority concern. Remediation of nonylphenol is possible through physicochemical and microbial methods. Microbial methods are widely used due to ecofriendly in nature. The microbial strains of the genera, Sphingomonas, Sphingobium, Pseudomonas, Pseudoxanthomonas, Thauera, Novosphingonium, Bacillus, Stenotrophomonas, Clostridium, Arthrobacter, Acidovorax, Maricurvus, Rhizobium, Corynebacterium, Rhodococcus, Burkholderia, Acinetobacter, Aspergillus, Pleurotus, Trametes, Clavariopsis, Candida, Phanerochaete, Bjerkandera, Mucor, Fusarium and Metarhizium have been reported for their potential role in the degradation of NP via its metabolic pathway. This study outlines the recent information on the occurrence, origin, and potential ecological and human-related risks of nonylphenol. The current development in the removal of nonylphenol from the environment using different methods is discussed. Despite the significant importance of nonylphenol and its effects on the environment, the number of studies in this area is limited. This review gives an in-depth understanding of NP occurrence, fate, toxicity, and remediation from the environments.

Thallium in aquatic environments and the factors controlling Tl behavior

Although thallium (Tl) usually exists in a very low level in the natural environment, it is highly toxic. With the development of mining and metallurgical industry and the wide application of Tl in the field of high technologies, Tl poses an increasing threat to the ecological environment and human health. This paper summarizes the research results of the toxicity of Tl as well as the distribution, occurrence forms, migration, and transformation mechanism of Tl in rivers, lakes, mining areas, estuaries, coastal waters, and oceans. It also discusses the influence mechanisms of pH, redox potential, suspended particulate matters, photochemical reaction, natural minerals, cation/anion, organic matters, and microorganisms on the environmental behavior of Tl. This paper points out the shortcomings of Tl research methods in water environment, and looks forward to the future development directions: First, the technology for separating Tl(III) and Tl(I) is still immature, especially it is difficult to effectively separate Tl(III) and Tl(I) in seawater. Second, the development of many advanced in situ detection technologies will bring great convenience to the studies of the dynamic mechanisms of Tl migration and transformation in the environments. Third, adsorption is the most effective mechanism to remove Tl from water, in which modified metal oxides or macrocyclic organic compounds have high application potential.

Mechanism analysis of MnFe2O4/FeSX for removal of Cr(VI) from aqueous phase

By using Na₂S as a sulfur source, sulfur-doped MnFe₂O₄ was prepared using one-step solvent thermal method and utilized to remove hexavalent chromium. The materials were characterized through scanning electron microscopy, transmission electron microscopy, high-resolution TEM, X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer-Emmett-Teller method, zeta potential test, vibrating sample magnetometry, and X-ray photoelectron spectroscopy. When the pH was 3, the adsorption capacity of MnFe₂O₄/FeS_X-0.5 to Cr(VI) was 43.36 mg/g, which was roughly five times that of MnFe₂O₄ (8.90 mg/g). MnFe₂O₄/FeS_X-0.5 and MnFe₂O₄ fitted the Freundlich and pseudo-second-order kinetic models well. The electrochemical test analysis results showed that MnFe₂O₄/FeS_X had a faster MnFe₂O₄ electron transfer rate and higher electron transfer capacity than MnFe₂O₄, and thus promoted the reduction of Cr(VI) to Cr(III). This finding could be attributed to the lower electronegativity of the sulfur element than the oxygen element. In addition, the formation of additional FeS_X through sulfur doping improved the Cr(VI) removal ability of the prepared materials. The XPS and desorption results showed that more than 80% of the adsorbed Cr(VI) were reduced to Cr(III), which indicated that reduction was an important mechanism for Cr(VI) removal. This study verified that sulfur-doped manganese ferrite can be utilized in the high-efficiency removal of Cr(VI).

Bacterial response to soil property changes caused by wood ash from wildfire in forest soils around mining areas: Relevance of bacterial community composition, carbon and nitrogen cycling

The different physical-chemical properties of the black ash (200-500 °C) and white ash (>510 °C) generated by wildfire may result in varied impacts on soil biological and abiotic indicators. Many studies have highlighted the environmental impacts of wood ash application due to its complex mixture of beneficial and detrimental compounds. However, few studies have compared the effect of black ash and white ash on soil, especially for the heavy metal polluted soil. In this study, we used the comparative analysis of parallel microcosm experiments to study the impacts of white ash and black ash on bioavailable heavy metals and metabolic potentials of microbial community. The results indicated that both white ash and black ash increased the concentration of soil bioavailable As and Cr, while the increasing trend of bioavailable As could be limited by Ca in the treatment of white ash. The addition of black ash could enhance the abundance of genes related to the Calvin cycle (CBB). Different kinds of wood ash inputs into soils could cause the differences in the microbial taxa for carbon fixation, as indicated by the dominance of different taxa for carbon fixation in white ash versus black ash treatments. Additionally, both white ash and black ash impaired dissimilatory nitrate reduction to ammonium (DNRA), nitrate assimilation and nitrification, while white ash enhanced denitrification.

Effects of bamboo biochar on nitrogen conservation during co-composting of layer manure and spent mushroom substrate

Layer manure (LM) and spent mushroom substrate (SMS) are two kinds of nitrogen (N) rich solid wastes generate in the poultry breeding and agriculture production. Composting is an effective way to recycle the LM and SMS. However, a large amount of N in the LM and SMS was lost via volatilisation during composting, with negative environmental and economic consequences. This study investigated the effect of incorporating biochar at the ratio of 5%, 10%, and 15% (w/w) during co-composting of LM and SMS on ammonia (NH3) and nitrogen oxide (N2O) volatilisation and N retention. After the 35-day composting, the results showed that the pile temperature and seed germination index in biochar treatments were significantly improved in comparison with control treatment. The nitrogen in all treatments was lost in the form of N2O (0.05∼0.1%) and NH3 (13.1∼20.2%). Likewise, the total nitrogen loss was 28.9%, 20.3%, and 24.9%, respectively, of which N2O-N accounts for 0.05∼0.10%. Compared with control treatment, the total amount of NH3 volatilisation in biochar treatments of 5%BC, 10%BC and 15%BC was decreased by 21.2%, 33.1%, and 26.1%, respectively. The total amount of N2O emission was decreased by 39.0%, 13.2%, and 1.6%, respectively. Adding 10% and 15% biochar can significantly reduce NH3 volatilisation while adding 5% biochar treatment didn't significantly reduce NH3 emissions but showed the best performance in reducing N2O emission. The addition of 10% biochar in co-composting of LM and SMS is the recommended dosage that exhibited the best performance in improving composting quality and reducing nitrogen loss.

Cadmium isotopic fractionation in lead-zinc smelting process and signatures in fluvial sediments

Cadmium (Cd) is a toxic heavy metal pollutant. Various industrial activities, especially metal smelting, are the main sources of Cd pollution. Cd isotopes have exhibited the ability to be excellent source tracers and can be used to assess the pollution contributions from different sources. Herein, in a typical lead-zinc smelter, Shaoguan, China, significant Cd isotopic fractionation was found during the high temperature smelting process and followed a Rayleigh distillation model. The heavier Cd isotopes were concentrated in the slag, while the lighter Cd isotopes were concentrated in the dust. In the downstream sediment profile of the smelter, sediments have extremely high Cd concentrations that far exceed the Chinese background sediment, indicating severe pollution levels. The ε^114/110Cd of the sediment core, ranged from - 0.62 ± 0.5-1.73 ± 0.5, are found between slag (ε^114/110Cd=10.42) and dust (ε^114/110Cd=-5.68). The binary mixture model suggests that 88-93% of the Cd in sediment profile was derived from the slag, and 7-12% from the deposition of dust. The findings demonstrate the great potential to apply Cd isotopes as a new geochemical tool to distinguish anthropogenic sources and quantify the contribution from various sources in the environment.

Porous biochar-supported MnFe2O4 magnetic nanocomposite as an excellent adsorbent for simultaneous and effective removal of organic/inorganic arsenic from water

To solve the problem of organic and inorganic arsenic species contamination in drinking water and/or wastewater, porous biochar-supported MnFe₂O₄ magnetic nanocomposite (BC-MF) was successfully fabricated and used as an excellent adsorbent for simultaneous removal of p-ASA and As(V) from water environment. This obtained BC-MF displayed remarkable adsorption performance for both p-ASA and As(V) removal at acidic and neutral pH (3-7), and di-anionic and mono-anionic species of p-ASA and As(V) facilitated the adsorption process. Specifically, BC-MF exceeded some reported adsorbents, and the adsorption capacities of p-ASA and As(V) were approximately 105 and 90 mg/g at a 10 μg/L equilibrium concentration. Satisfactory adsorption behavior including adsorption isotherms, competitive ions, humic acid (HA), and regeneration/reusability property in single and binary systems demonstrated the BC-MF can improve the potential application for arsenic-containing wastewater remediation. Proposed adsorption mechanism indicated that electrostatic interaction and surface complexation were involved the p-ASA and As(V) immobilization, whereas hydrogen bonding and π-π interactions may also contribute to the p-ASA removal. Additionally, the prominent sequestration p-ASA and As(V) performance in different water matrix and fixed-bed column studies indicated that BC-MF was a promising nanocomposite for simultaneously removal of organic and inorganic arsenic species in practical wastewater treatment.

Dispersive micro-solid phase extraction with a magnetic nanocomposite followed by electrothermal atomic absorption measurement for the speciation of thallium

A magnetic dispersive micro-solid phase extraction procedure for the determination of the thallium content in waters is presented. The incorporation in the sample (10 mL) of a small amount of graphene-Fe₃O₄ composite (3.6 mg) in the presence of 10^-4 mol L^-1 Aliquat 336 at pH 2 results in the complete retention of both thallium(I) and thallium(III). After separation with a magnet, the micro-solid phase recovered is treated with 0.05 mL of a 0.1 mol L^-1 sodium ethylenediaminetetracetate solution at pH 9, and the supernatant obtained after application of the magnet is introduced in the electrothermal atomizer of an atomic absorption spectrometer to obtain the signal corresponding to the total thallium content. For speciation, the trivalent form in a second sample aliquot is separated by means of a liquid-liquid extraction stage with chloroform and methyl trioctyl ammonium in the presence of bromide, and the signal corresponding to the monovalent form is obtained, the concentration of thallium(III) being obtained by difference. The enrichment factor is 185, which permits a detection limit as low as 0.01 μg L^-1 of the analyte to be achieved. The relative standard deviation for five measurements at the 0.1 μg L^-1 thallium level is below 5%. The reliability of the procedure is verified by analysing five certified reference samples for which speciation data are also given.

Pedogeochemical distribution of gallium, indium and thallium, their potential availability and associated risk in highly-weathered soil profiles of Taiwan

Gallium (Ga), indium (In), and thallium (Tl) are emerging soil contaminants. Profile distribution of total content and available form as well as assessing the contamination degree of these elements in highly-weathered soils have not been studied. Consequently, the aim of this study was to determine the distribution of total (HF-digestion) and available (EDTA-extracted form) content of Ga, In, and Tl in eleven soil profiles collected from aged fluvial materials on the Quaternary terraces representing highly-weathered soils (Ultisols and Oxisols) in Taiwan as affected by soil properties. We also assessed the soils contamination degree using indices including enrichment factor (EF), geo-accumulation index (I_geo), and pollution loading index (PLI). The total element content varied from 9460 to 2340 μg kg^-1 for Ga, 4.77-37.1 μg kg^-1 for In, and from 55.7 to 206 μg kg^-1 for Tl. The elements showed different profile distribution in the soils. Soil contamination degree was low in all profiles according to the I_geo and PLI values, but the contamination degree according to the EF was severe for Ga and minor or moderate for In in selected horizons of some profiles. The median content of EDTA-extracted Ga, In, and Tl accounted for 24.0, 8.70, and 5.1% of the total content, respectively. The available Ga and Tl can be predicted by a function of total element and clay using multivariate linear regression analysis. The available In was not able to be predicted by a significant fit of the regression with total In and the studied soil properties, and thus we require more assessment approaches of In availability for the soils in the future.

Emergent thallium exposure from uranium mill tailings

Thallium (Tl) pollution caused by the exploitation of uranium (U) mines has long been neglected due to its low crustal abundance. However, Tl may be enriched in minerals of U ore because Tl has both sulfurophile and lithophile properties. Herein, a semi-dynamic leaching experiment combined with statistical analysis, geochemical speciation and multi-characterization provided novel insight into the distinct features and mechanisms of Tl release from uranium mill tailings (UMT). The results showed that particle size effects prevail over the pH on Tl release, and surface dissolution is the pivotal mechanism controlling Tl release based on Fick's diffusion model. The study revealed that long-term leaching and weathering can lead to the increased acid-extractable and oxidizable fractions of Tl in UMT, and that the exposure and dissolution of Tl-containing sulfides would largely enhance the flux of Tl release. The findings indicate that UMT containing (abundant) pyrite should be paid particular attention due to Tl exposure. Besides, critical concern over the potential Tl pollution in universal U mining and hydrometallurgical areas likewise may need to be seriously reconsidered.

Synthesis of Manganese Ferrite/Graphene Oxide Magnetic Nanocomposite for Pollutants Removal from Water

These days, environmental pollution, notably water pollution, has increasingly caused severe human health problems. The major water pollutants are heavy metals. MnFe2O4/GO nanocomposite was prepared in the current work via in situ method and tested to remove lead ion Pb2+ and neutral red (NR) dye from water. The prepared nanocomposite was characterized using different techniques, including X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectra, and vibrating sample magnetometer. The prepared nanocomposite showed high adsorption capacity toward Pb2+ and NR dye removal according to Langmuir fitting indicating the monolayer homogeneous adsorption of pollutants over the adsorbent surface and can be separated easily with an external magnet. The effect of different factors, including contact time, pH, initial concentration, and adsorbent dose on the adsorption, were also studied. The increased concentration of pollutants led to increased adsorption capacity from 63 to 625 mg/g for Pb2+ ions and from 20 to 90 mg/g for NR dye. The increased adsorbent dose led to increased removal efficiency from 39% to 98.8% and from 63% to 94% for Pb2+ and NR dye, respectively. The optimum pH for the adsorption of both pollutants was found to be 6.0. The reusability of MnFe2O4/GO nanocomposite was studied for up to five cycles. The nanocomposite can keep its efficiency even after the studied cycles. So, the prepared magnetic nanocomposite is a promising material for water treatment.

New insights on nanostructure of ordered mesoporous FeMn bimetal oxides (OMFMs) by a novel inverse micelle method and their superior arsenic sequestration performance: Effect of calcination temperature and role of Fe/Mn oxides

A series of ordered mesoporous FeMn bimetal oxides (OMFMs) were fabricated by using a novel inverse micelle method, and the texture, nanostructure and interface chemistry properties of OMFMs were closely correlated to the calcination temperature. Due to the amorphous regular inner-connected nanostructure and bimetallic synergistic effect, the obtained OMFMs exhibited superior arsenic sequestration performance than pure mesoporous Fe oxides (PMF) and Mn oxides (PMM). The optimum ratio of Fe/Mn and calcination temperature for arsenic removal was 3/1 and 350 °C (OMFM-3), and the maximum As(III) and As(V) adsorption capacities of OMFM-3 were 174.59 and 134.58 mg/g, respectively. Solution pH value negligibly affected the uptake of arsenic (ranged from 3.0 to 7.0), while SiO₃^2-/PO₄^3- ions and humic acid (HA) displayed significant inhibitory effect on arsenic removal by OMFM-3. According to the mechanism of arsenic removal, which simultaneously analyzed the arsenic redox transformation in aqueous phase and on solid phase interface, it was concluded that manganese oxides in OMFM-3 mainly played the role as a remarkable As(III) oxidant in water, whereas iron oxides dominantly acted as an excellent arsenic species adsorbent. Finally, the prominent arsenic sequestration behavior and performance in surface water suggested that OMFM-3 could be a promising and hopeful candidate for arsenic-contaminated (especially As(III)) surface water and groundwater remediation and treatment.

Heavy-ion irradiation effects on uranium-contaminated soil for nuclear waste

In the field of radioactive waste immobilization, the investigation of irradiation stability is of considerable importance. In this study, uranium-contaminated soil samples were irradiated by 1.5 MeV Xe²⁰⁺ ions with fluences ranging from 1 × 10¹² to 1 × 10¹⁵ ions/cm². Xe²⁰⁺ heavy-ion radiation was used to simulate the self-irradiation of actinide nuclides. The uranium-contaminated soil samples were sintered via microwaves. Grazing incidence X-ray diffraction results showed that irradiation can cause crystallization of the sample. After irradiation, the Vickers hardness of the samples decreased slightly. Comparative analysis showed that the sample had good radiation resistance, and the leaching rate (28 d) of the sample increased slightly after irradiation, but the overall performance was stable. Our investigation reveals the corresponding mechanism of uranium-contaminated soil irradiation of 1.5 MeV Xe²⁰⁺ ions.

Degradation of anthraquinone dye reactive blue 19 using persulfate activated with Fe/Mn modified biochar: Radical/non-radical mechanisms and fixed-bed reactor study

In this study, a heterogeneous activator was prepared via the Fe/Mn modification of sludge-derived biochar (Fe/MnBC) to achieve high-efficiency activation of persulfate (PS) for reactive blue 19 (RB19) degradation. The morphologies and chemical states of Fe/MnBC were examined by various characterizations. A comprehensive assessment was conducted to reveal the effects of biochar preparation conditions and system reaction conditions. According to the results of scavenger quenching experiments and electron paramagnetic resonance (EPR) testing, the mechanisms of Fe/MnBC combined PS system on RB19 degradation were proposed, including radical and non-radical mechanisms. The formation and involvement of sulfate radical (SO₄^·-), hydroxyl radical (OH^·), and singlet oxygen (¹O₂) were proved in this system, and Fe(IV)/Mn(VII) was also speculated to participate in the non-radical degradation process. These findings give a new insight into the mechanisms of PS activated by metal-biochar composite. Besides, fixed-bed reactor (FBR) experiments indicated that the Fe/MnBC has considerable PS activation potential for dyes removal. The degradation process was further modeled by the central composite design (CCD-RSM) and artificial neural networks (ANN) methods. The statistical metrics and prediction indicated that the prediction results of ANN model were better than CCD-RSM model, and the ANN model could perfectly predict the reaction process of Fe/MnBC FBR for engineering applications.

Biochar industry to circular economy

Biochar, produced as a by-product of pyrolysis/gasification of waste biomass, shows great potential to reduce the environment impact, address the climate change issue, and establish a circular economy model. Despite the promising outlook, the research on the benefits of biochar remains highly debated. This has been attributed to the heterogeneity of biochar itself, with its inherent physical, chemical and biological properties highly influenced by production variables such as feedstock types and treating conditions. Hence, to enable meaningful comparison of results, establishment of an agreed international standard to govern the production of biochar for specific uses is necessary. In this study, we analyzed four key uses of biochar: 1) in agriculture and horticulture, 2) as construction material, 3) as activated carbon, and 4) in anaerobic digestion. Then the guidelines for the properties of biochar, especially for the concentrations of toxic heavy metals, for its environmental friendly application were proposed in the context of Singapore. The international status of the biochar industry code of practice, feedback from Singapore local industry and government agencies, as well as future perspectives for the biochar industry were explained.

A meta-analysis of heavy metal bioavailability response to biochar aging: Importance of soil and biochar properties

Biochar has been widely applied to remediate the heavy metal-polluted soils, whereas biochar aging can induce the changes of the biochar physic-chemical properties. Afterwards, the bioavailability of heavy metals (BHM) will vary in soils which likely increase the unstable fractions of heavy metals and the following environmental risks. To explore the biochar aging effects on the BHM changes in responses to the variation of experimental conditions and biochar properties, a meta-analysis for the literatures published before May 2020 was conducted. A sum of 257 independent observations from 22 published papers was obtained. The results from the analysis of boosted regression tree showed that the soil pH was the most important factor influencing the BHM changes in biochar amended soil, followed by soil texture, aging time and biochar pyrolysis temperature. The results of this review showed that the BHM was decreased by 16.9%, 28.7% and 6.4% in weakly acid soil (pH 6.00-6.99), coarse- and medium-textured soils, respectively, but increased by 149% and 121% in the alkaline (pH > 8.00) and fine-textured soils. The BHM declined in the soils amended with biochar pyrolyzed at relative high temperature (> 500 °C), and increased during aging in soils amended with biochar pyrolyzed at relatively low temperature (401-500 °C). In terms of diverse immobilized heavy metals, only bioavailable Zn in soil decreased after aging. However, there was no significant changes in Cd, Cu and Pb's bioavalability. Besides, the BHM was decreased by 18.6% within the short-term (less than one year) biochar aging, while showed inverse trend during the longer aging processes. Besides, the application of lignin-enriched biochar may counteract the positive effects of the biochar aging on BHM. Our works may promote the interpretation of the interference factors on the BHM changes and filled the research gaps on biochar aging process in soils.

Activation of MnFe2O4 by sulfite for fast and efficient removal of arsenic(III) at circumneutral pH: Involvement of Mn(III)

As(III) oxidation to As(V) is deemed necessary for better arsenic removal, and separation is still the optimal approach for water remediation from As(III). Herein, sulfite (SIV) was adopted to activate MnFe₂O₄ for simultaneous oxidation and adsorption of As(III) in neutral water. The As(III) removal was more efficient than a peroxidation of As(III) followed by adsorption. The adsorption capacity of MnFe₂O₄/S(IV) for As(III) (26.257 mg g^-1) was much higher than those of MnFe₂O₄ alone for As(III) (9.491 mg g^-1) and As(V) (9.142 mg g^-1). The mechanistic study corroborated that intermediate Mn(III) was the dominant oxidant responsible for rapid oxidation of As(III), and the dual roles of S(IV) as a complexing ligand and a precursor of oxysulfur radicals accelerated the redox cycle of Mn(II)/Mn(III). Moreover, S(IV) enhanced arsenic adsorption by driving more production of monodentate complexes. As(III) can be effectively removed over a wide range of temperatures (283.15-313.15 K) and pH (3-10) with the optimal pH of 7. The effect of coexisting ions and reusability of MnFe₂O₄ were also investigated. Especially, the superior performance of MnFe₂O₄/S(IV) for As(III) removal in various water matrixes may help develop new removal technologies based on active Mn(III) for the water decontamination from As(III).

Novel magnetic loofah sponge biochar enhancing microbial responses for the remediation of polycyclic aromatic hydrocarbons-contaminated sediment

Magnetic activated carbon and magnetic biochar have been widely used for contaminants removal due to the advantages of sequestration and recovery. However, the remediation function and microbial response of conductive magnetic carbonaceous materials for treating organic contaminated sediment are poorly understood. In this study we applied novel three-dimensional mesh magnetic loofah sponge biochar (MagLsBC), made from natural agricultural product, to remediate polycyclic aromatic hydrocarbons (PAHs)-contaminated sediment. Compared to other carbon-based materials, MagLsBC achieved the high reduction of PAHs content and bioavailability in sediment by respectively 31.9 % and 38.1 % after 350 days. Microbial analysis showed that MagLsBC amended sediment had different community diversity, structure and enriched dominant species associated with the aromatic hydrocarbon metabolism. And MagLsBC amendment significantly increased the aromatic compounds degradation function, which was not observed in other treatments, and methanogenesis function. Further analysis revealed that the enhanced microbial responses in MagLsBC amended sediment were related with the high conductivity of MagLsBC. These results give the new insights into the effect of magnetic carbon materials on microbial community and organic pollutants degradation function during the long period amendment, demonstrating MagLsBC as an effective material with the biostimulation potential for the risk control of PAHs contamination.

Enhanced adsorption of tetracycline by an iron and manganese oxides loaded biochar: Kinetics, mechanism and column adsorption

A Fe/Mn oxides loaded biochar (FeMn-BC) was prepared to enhance the adsorption of tetracycline (TC). γ-Fe₂O₃ and MnO₂ were assigned to the Fe and Mn oxides, respectively. The enhanced adsorption of TC was dominated by the loaded γ-Fe₂O₃ and MnO₂. According to Akaike-Information-Criteria evaluation, Elovich kinetic and Langmuir isotherm models could best describe the adsorption with a maximum capacity of 14.24 mg/g. During adsorption process, the γ-Fe₂O₃ and MnO₂ hydrolyzed into hydroxides (FeOOH and MnOOH) which acted as bases to complex with TC^2- ion under alkaline condition (pH = 11). After the adsorption, the concentrations of leached Fe and Mn could meet the requirements PRC standards GB13456-2012 and GB8978-1996, respectively. The FeMn-BC had ~24% on TC removal (initial concentration of 20 mg/L) after four-cycles regeneration. The FeMn-BC was also available for TC adsorptions in column tests and actual wastewater.

Emerging risks of toxic metal(loid)s in soil-vegetables influenced by steel-making activities and isotopic source apportionment

Industrial activities tend to deteriorate adjacent agricultural lands due to accumulation of potentially toxic elements in soils and crops. However, better understanding of their distinctive source partitions and transfer process remains insufficient in steel-making area. The paper focuses on the pollution levels, health risks, and provenance identification of Tl, As, Pb, Cu, Ni, Co, Sb, Cd, Zn, Be, Cr, Fe, Mn, Mo, Sn, and V in common vegetables from different farmlands near a steel-making plant. The results showed that the Tl, As, Pb, Cd, Cr, Cu and Mn were of high-level contamination in soils and generally above the maximum permissible level (MPL). Calculation using hazard quotients (HQ) exhibited that consumption of the studied vegetables may entail significant health risks to residents, especially for children, resulting from the elevated contents of Tl, As and associated toxic elements. Calculation by binary mixing model using Pb isotopic compositions suggested that steel-making activities contributed to 35-80% of the contamination of Pb and As in vegetables. It is necessary to adopt appropriate remediation measures to mitigate the farmland contamination and ensure the food safety of the agricultural products.

Mitigation of arsenic accumulation in arugula (Eruca sativa Mill.) using Fe/Al/Zn impregnated biochar composites

Arsenic (As) contamination of aquatic and soil environments is a global concern, highlighting the importance of As removal via high-efficiency and low-cost removal technologies. In the present study, novel trimetallic biochar was developed through pyrolyzing corn straw impregnated with inexpensive metal Fe/Al/Zn (hydr)oxides. The results of SEM, FTIR, and XRD verified the formation of metal oxyhydroxides on the surface of the modified biochars, and the modification increased the specific surface area (SSA), total pore volume (TPV), and surface charge of the Fe/Al/Zn (hydr)oxides modified biochar (FAZ-CB). Compared with the original biochar, higher sorption rates and capacities was observed for the FAZ-CB. The maximum As (V) adsorption capacities of FAZ-CB reached 82.9 mg g^-1. A pot experiment showed that application of FAZ-CB decreased bioavailable As fractions in the red soil significantly reduced the uptake of As by arugula in edible part and root (42.6 and 56.8%, respectively). The present study demonstrated the superiority of FAZ-CB in the As(V) immobilization in red soil, suggesting that it is a promising candidate for practical application for As immobilization. Therefore, FAZ-CB can be used as a promising functionalized biochar to remediate As contaminated red soil.

Distribution patterns and sources of heavy metals in soils from an industry undeveloped city in Southern China

The accumulations of heavy metals in urban soils are derived from natural parent materials and complex anthropogenic emission sources. This paper investigated metal contamination in urban soils at an industry undeveloped city (Haikou) in southern China, an ideal place to quantitatively assess the contribution of metals from different sources. The concentrations of most heavy metals in the urban soils of Haikou were much lower than their guideline values and that of those from other big cities in China. In contrast, the chemical speciation of metals in this study was similar to those from other cities. The spatial distributions of heavy metals and principal component analysis (PCA) revealed that basaltic parent materials, traffic emissions, and coal combustion were the main factors controlling the distribution of metals in the soils. The Pb isotope signatures of the Haikou soils were greatly different from those of the Beijing and Shanghai soils, but similar to those of the Guangzhou soils, suggesting the common sources of Pb in southern China cities. The results of ternary mixing model of Pb isotopes showed that the contributions of Pb from natural background, coal combustion and traffic emission sources were 5.3-82.4% (mean: 39.7 ± 21.1%), 0-85.7% (mean: 25.5 ± 24.6%), and 1.9-64% (mean: 34.8 ± 22.9%), respectively. This suggests that traffic emission is still the most important anthropogenic source of Pb in Haikou.

Quantitative isotopic fingerprinting of thallium associated with potentially toxic elements (PTEs) in fluvial sediment cores with multiple anthropogenic sources

Thallium (Tl) is a dispersed trace metal showing remarkable toxicity. Various anthropogenic activities may generate Tl contamination in river sediments, posing tremendous risks to aquatic life and human health. This paper aimed to provide insight into the vertical distribution, risk assessment and source tracing of Tl and other potentially toxic elements (PTEs) (lead, cadmium, zinc and copper) in three representative sediment cores from a riverine catchment impacted by multiple anthropogenic activities (such as steel-making and Pb-Zn smelting). The results showed high accumulations of Tl combined with associated PTEs in the depth profiles. Calculations according to three risk assessment methods by enrichment factor (EF), geoaccumulation index (I_geo) and the potential ecological risk index (PERI) all indicated a significant contamination by Tl in all the sediments. Furthermore, lead isotopes were analyzed to fingerprint the contamination sources and to calculate their quantitative contributions to the sediments using the IsoSource software. The results indicated that a steel-making plant was the most important contamination source (∼56%), followed by a Pb-Zn smelter (∼20%). The natural parental bedrock was found to contribute ∼24%. The findings highlight the importance of including multiple anthropogenic sources for quantitative fingerprinting of Tl and related metals by the lead isotopic approach in complicated environmental systems.