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Green water treatment technologies are widely popular, and magnetic coagulation is one of the most popular methods and has been successfully applied in industry. Among them, magnetic seeds are crucial for the flocculation of contaminants. The objective of this work was to investigate the potential of magnetic metal–organic frameworks (MMOFs) as a seed in assisting polymeric ferric sulfate (PFS) flocculant, specifically exploring their applicability in algal-contaminated water. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, ferrite timing spectroscopy, and flocculation tests were used to characterize the structure and flocculation properties of MMOFs and PFS (PFS-MMOFs) composites, highlighting the stability of magnetic seed MMOFs and the flocculation effect of the composites. The results show that MMOFs have good dispersion and stability in acidic PFS solutions, which are favorable for engineering applications. MMOFs and PFS are bonded by hydrogen bonds, which enhance the polarity and dispersion of MMOFs, as well as the molecular chains of PFS. In the presence of MMOFs, it affected the distribution of iron species in the PFS, which means that the performance of coagulation may be changed. Coagulation with PFS-MMOFs was effective under different hydraulic conditions. It also showed better results than PFS in terms of dissolved organic carbon (DOC) removal and ultraviolet absorption value at 254 nm (UV254). In addition, the PFS-MMOFs in algal-infested waters were superior to the PFS. Overall, the findings tested in this study indicated that MMOFs are good magnetic seeds for remediation of water pollution in conjunction with PFS, potentially enhancing conventional coagulation. [ABSTRACT FROM AUTHOR]

The Hunan region is a high geological background area of black rock series rich in various metallic elements; accordingly, local heavy metal pollution is severe. Previous studies on black shale have primarily focused on the lower Cambrian strata, while research on Carboniferous black shale remains scarce. To better explore the activity law of heavy metals during Carboniferous black shale weathering, this study analyzed the elemental components of samples through field observations of outcrops in the Qiziqiao area of central Hunan province, China using inductively coupled plasma mass spectrometry and X-ray fluorescence spectrometry. The results showed that the heavy metal content of black shale under different degrees of weathering varied greatly, with different heavy metals maintaining distinct migration and enrichment rules throughout this process. The heavy metal content in Carboniferous black shale and soils of central Hunan was generally less than that of the regional lower Cambrian black shale and soil; however, the Cd content in the black shale soil was slightly higher than background values, while the Sr content was substantially higher than background values. Heavy metals V, Cr, Co, Ni, Cu, and Pb were not generally leached or released during weathering, and may undergo relative enrichment or secondary enrichment. Comparatively, Zn, Cd, and Ba can be more readily leached and released, and may undergo secondary enrichment. The lithophilic element Sr tended to leach out overall and expressed strong activity, whereas the chemical activities of the high-field-strength elements, Zr and Hf, were relatively stable. During soil formation, all heavy metal elements save Sr were significantly enriched. The enrichment factor analysis of different degrees of weathered black shale reveals that the heavy metals Ba, Hf, and Sr in black shale soil originate from the parent rock. V, Cr, Co, Ni, Cu, Zn, Cd, and Pb are influenced by both natural and anthropogenic factors, with Cd being significantly impacted by human activities. The evaluation of soil heavy metals using the geoaccumulation index method indicates that V, Cr, Co, Ni, Cu, Zn, Zr, Ba, Hf, and Pb are non-polluted, Cd exhibits moderate pollution, and Sr shows moderately heavy pollution. From a geochemical perspective, it can be inferred that heavy metals in black shale soil are likely to be secondarily enriched in clay and iron oxide minerals. [ABSTRACT FROM AUTHOR]

To improve the removal of antimony (Sb) from contaminated water, sepiolite (Sep) was chosen as the feedstock, modified with an acid–base and a ferric ion to yield a hydroxy-iron/acid–base-modified sepiolite composite (HI/ABsep). The surface structure of the HI/ABsep and the removal effect of the HI/ABsep on Sb (III) were investigated using potassium tartrate of antimony as the source of antimony and HI/ABsep as the adsorbent. The structural features of the HI/ABsep were analyzed by SEM, FTIR, PXRD, BET, and XPS methods. Static adsorption experiments were performed to investigate the effects of adsorption time, temperature, adsorbent dosage, and pH on the Sb (III) adsorbed by HI/ABsep. This demonstrates that sepiolite has a well-developed pore structure and is an excellent scaffold for the formation of hydroxy-iron. HI/ABsep adsorption of Sb (III) showed the best fit to the pseudo-second-order model and the Freundlich model. The maximum saturated adsorption capacity of the HI/ABsep regarding Sb (III) from Langmuir's model is 25.67 mg/g at 298 K. Based on the research results, the HI/ABsep has the advantages of easy synthesis and good adsorption performance and has the potential to become a remediation for wastewater contaminated with the heavy metal Sb (III). [ABSTRACT FROM AUTHOR]

In this study, we analyzed 53 topsoil samples from the Xikuangshan South Mine in Hunan Province to investigate the distribution characteristics of pH and the concentrations of selected metals to determine the controlling factors and identify their sources. Kriging interpolation, correlation analysis, principal component analysis, the index of the geoaccumulation index, and Hakanson's potential ecological risk were applied. The results show that the mean values of Pb, As, Cd, and Sb in the study area were larger than the background value of mountain soil in Hunan Province, and only the average Cr concentration was slightly lower than the background value. The spatial distributions of pH and five metals in the soil were very different, indicating that pH had no significant effect on the distribution of the metals. The wind, rivers, and land‐use patterns in different regions of the study area may be the main reasons for their distribution patterns. The correlation component and principal component analysis revealed that Pb showed positive correlations with Cr and Cd, respectively, and Sb‐As and Cr‐Cd showed strong paired correlations. The cumulative proportion of the first two components accounted for 70.516% of the total variance, which suggests that mining activities are a major source of As and Sb, whereas Pb, Cr, and Cd were derived from natural and anthropogenic sources. The geoaccumulation index revealed that the major pollutants in the soils were mainly Cd, followed by Sb and As. The soils in the study area were moderately contaminated with Pb and lightly polluted by Cr. The ecological hazards of each metal in descending order were Cd > Sb > As > Pb > Cr. The index of the comprehensive potential ecological risk for metals indicated that the Xikuangshan South Mine is at or above a moderate ecological risk level, with an extremely strong potential for ecological risks posed by Cd and Sb. Integr Environ Assess Manag 2022;18:748–756. © 2021 SETAC Key Points: The mean values of Pb, As, Cd and Sb in the Xikuangshan South Mine are over the background value of mountain soil in Hunan Province, only the average Cr content is slightly lower than the background value.pH had no significant effect on the spatial distribution of metals, the wind, rivers and land use patterns in different regions may be the main reasons for their distinguishing distribution patterns.The cumulative proportion of the first two components suggest mining activities were the major sources for As and Sb, natural and anthropogenic sources for Pb, Cr and Cd.The index of comprehensive potential ecological risk for metals indicated that the Xikuangshan South Mine was at or above the level of moderate ecological risk, with an extremely strong potential for the ecological risks pose by Cd and Sb. [ABSTRACT FROM AUTHOR]

Manganese released from the piled manganese ore wastes is a great threat to the local ecosystem and human health. The mechanism and dynamic characteristics of manganese release from the manganese ore wastes were studied based on the static and dynamic experiments. The concentration of manganese in the leaching solution under the intensive state is twice that resulted from the static state; the manganese release from the waste rock increased with the increase of the solid-liquid ratio and reached 922.3 mg/L when the solid-liquid ratio was 1:5. When the particle size of waste rock was less than 180 μm, the release amount of manganese was the largest and reached 491.3 mg/L. When the pH was 7 and the rainfall intensity was 80 mL/h, the increase of leaching time contributed to the rapidly decreased amount of manganese released, and the leaching process reached equilibrium gradually. The cumulative release of manganese increased with the increase of rainfall duration. In the dynamic leaching process, the change of pH and EC of the leachate had nothing to do with the initial pH of leaching agent but has a close relationship with the hydrolysis of minerals in waste. According to the experimental results, it was found that the double constant equation model fitted the kinetic process of release process better. The purpose of this study was to provide a scientific basis for the assessment and control of manganese pollution in soil and groundwater in manganese mining area. [ABSTRACT FROM AUTHOR]

Antimony (Sb) is a priority pollutant in many countries and regions due to its chronic toxicity and potential carcinogenicity. Elevated concentrations of Sb in the environmental originating from mining and other anthropogenic sources are of particular global concern, so the prevention and control of the source of pollution and environment remediation are urgent. It is widely accepted that indigenous microbes play an important role in Sb speciation, mobility, bioavailability, and fate in the natural environment. Especially, antimony-oxidizing bacteria can promote the release of antimony from ore deposits to the wider environment. However, it can also oxidize the more toxic antimonite [Sb(III)] to the less-toxic antimonate [Sb(V)], which is considered as a potentially environmentally friendly and efficient remediation technology for Sb pollution. Therefore, understanding its biological oxidation mechanism has great practical significance to protect environment and human health. This paper reviews studies of the isolation, identification, diversity, Sb(III) resistance mechanisms, Sb(III) oxidation characteristics and mechanism and potential application of Sb-oxidizing bacteria. The aim is to provide a theoretical basis and reference for the diversity and metabolic mechanism of Sb-oxidizing bacteria, the prevention and control of Sb pollution sources, and the application of environment treatment for Sb pollution. [ABSTRACT FROM AUTHOR]

Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) are important components of the aquatic environment and may produce harmful disinfection by‐products through chlorination associated with water treatment processes. Therefore, it is necessary to remove them from the water. Coagulation is a cost‐effective water treatment technique as the key unit in the pretreatment of drinking water but deals with DON poorly. We present a study to investigate the enhancement of poly aluminum chloride (PAC) using a cationic polymer for the removal of both DON and DOC. The cationic dimethyl diallyl ammonium chloride (PDMDAAC) polymer was hybridized with PAC to remove DON and DOC. The results showed that the PDMDAAC increased the charge neutralization capacity of PAC and floc aggregation, thereby increasing the settling efficiency of the flocs. The PDMDAAC increased the amount of colloidal species in PAC, which was beneficial to the formation of adsorption‐bridging. With the increase of pH, a greater proportion of colloidal adsorption sites were used in the removal of DON. The DOC, DON, and turbidity removal were dependent on multiple interactions through charge neutralization, adsorption‐bridging, and floc sweeping. However, DOC and DON removal were primarily determined by adsorption‐bridging and floc sweeping, while turbidity removal was mainly dependent on charge neutralization. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Microscale zero‐valent iron (mZVI) is an efficient material for removing heavy metals from water, and iron‐oxidizing bacteria are the primary microorganisms responsible for iron corrosion. We investigated the effects of Sphaerotilus natans on antimony [Sb(V)] removal by mZVI using batch experiments. RESULTS: At an initial Fe0 dose of 0.1 g L–1, 40 mg L–1 Sb(V) was almost completely removed in an abiotic system. Although S. natans exhibited significant tolerance to Sb(V), its ability to adsorb Sb(V) was poor. Most importantly, the presence of S. natans reduced the removal rate of aqueous Sb(V) by mZVI by up to 39%. The value of the redox potential in the biologically mediated system was lower than that in the abiotic control, indicating oxygen consumption by S. natans. In the presence of S. natans, the main reaction products were FeOOH and FeSb2O6, compared to Fe2O3 in the abiotic system. Biomineralization of Fe3+ ions by S. natans may have occurred during the experiment, but it did not play a significant role in Sb(V) removal. CONCLUSION: mZVI can be efficiently used to remove Sb(V) from water. However, the presence of S. natans may inhibit its removal ability, likely due to the decreased mass transfer and lower corrosion of iron. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

With the rapidly increasing industrial and agricultural development, a large amount of sludge has been produced from much water treatment. Sludge treatment has become one of the most important environmental issues. Resource utilization of sludge is one of the important efficient methods for solving this issue. Sludge-based activated carbon (SBAC) materials have high adsorption performance and can effectively remove environmental pollutants including typical organic matter and heavy metals through physical and chemical processes. Therefore, developing efficient SBAC materials is important and valuable. At present, preparation, modification, and application of SBAC materials have gained widespread attention. This paper provides a review of the research on SBAC preparation and modification and its utilization in removing environmental pollutants. It included the following topics present in this review: conventional and new methods for preparation of SBAC were clearly present; the effective methods for improving SBAC performance via physical and chemical modification were reviewed; and the correlation of their physic-chemical properties of SBAC with pollutants’ removal efficiencies as well as the removal mechanisms was revealed. SBAC has a better adsorption performance than commercial activated carbon in some aspects. Furthermore, it is a cost-effective technique and has a wide range of raw materials. However, there are still some drawbacks to its research; thus, some suggestions for further research were given in this review. [ABSTRACT FROM AUTHOR]

Sb release characteristics of blast furnace slag, mining waste rock and tailing sand were investigated in static immersion and dynamic leaching test. These three kinds of waste samples were collected from the antimony mine in Lengshuijiang, China, produced in mining smelting process. Effects of solid/liquid ratio, sample size and pH of leaching solution on Sb release characteristics were inspected based on the analysis of scanning electron microscope, pH and EC of leachate. The optimal parameters for Sb leaching of each sample were analyzed. For blast furnace slag and mining waste rock, Sb release contents increased along with the decline of solid/liquid ratio. The maximum accumulative release contents were 42.13, 34.26 mg/kg at the solid/liquid ratio of 1:20. While Sb release content for tailing sand decreased first and then increased with the reduction of solid/liquid ratio. When the solid/liquid ratio was 1:5, the accumulative Sb release content reached the most (24.30 mg/kg). Sb release content of mining waste rock increased with the drop of leaching solution pH, with the highest accumulative release content of 26.01 mg/kg at pH 2.0. Sb release contents of blast furnace slag and tailing sand showed positive correlation with the variation of leaching solution pH. The maximum accumulative release contents of these two samples were 215.91 and 147.83 mg/kg, respectively, when leaching solution pH was 7.0. In summary, Sb release capacity of the three samples in descending order was tailing sand, blast furnace slag and mining waste rock. pH and EC of the leachate in dynamic test varied independently with the initial pH of leaching solution while showing close relationship with mineral hydrolysis in the waste. [ABSTRACT FROM AUTHOR]

Gemini surfactants, with double hydrophilic and hydrophobic groups, offer potentially orders of magnitude greater surface activity compared to similar single unit molecules. A cationic Gemini surfactant (Propyl didodecyldimethylammonium Bromide, PDDDAB) and a conventional cationic surfactant (Dodecyltrimethylammonium Bromide, DTAB) were used to pre-treat and generate activated carbon. The removal efficiency of the surfactant-modified activated carbon through adsorption of chromium(VI) was investigated under controlled laboratory conditions. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to investigate the surface changes of surfactant-modified activated carbon. The effect of important parameters such as adsorbent dosage, pH, ionic strength and contact time were also investigated. The chromium(VI) was adsorbed more significantly on the Gemini surfactant-modified activated carbon than on the conventional surfactant-modified activated carbon. The correlation coefficients show the data best fit the Freundlich model, which confirms the monolayer adsorption of chromium(VI) onto Gemini surfactant-modified activated carbon. From this assessment, the surfactant-modified (especially Gemini surfactant-modified) activated carbon in this study showed promise for practical applications to treat water pollution. [ABSTRACT FROM AUTHOR]