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Microplastics are plastic particles less than 5 mm in diameter and are widely present in water environments. Their unique surface structures can adsorb coexisting pollutants in the surrounding environment, such as antibiotics and metal ions, leading to compound pollution. The adsorption of ciprofloxacin on polyethylene microplastics under different environmental conditions (pH and salinity) was investigated. The Freundlich model fitted well at 25 °C, indicating that the adsorption of ciprofloxacin by polyethylene microplastics was multilayered, and Fourier Transform infrared spectroscopy (FTIR) analysis indicated that the adsorption of ciprofloxacin by polyethylene microplastics was physical. The kinetic adsorption of ciprofloxacin on polyethylene microplastics followed a pseudo-second-order mode. Heavy metals (Cu2+, Cr3+, Cr6+, Cd2+, and Pb2+) affected the adsorption of ciprofloxacin by microplastics, which was related to the type and concentration of metal ions and the valence state of the ions. The acute toxicity of microplastics and the microplastic-ciprofloxacin-Cu2+ complex were evaluated using luminescent Photobacterium phosphoreum , demonstrating the polyethylene toxicity microplastic-ciprofloxacin-Cu2+ complex was mainly caused by Cu2+ and ciprofloxacin rather than microplastics. This study provides theoretical support for the environmental behavior and ecological effects of microplastics in aqueous environments. [Display omitted] • Ciprofloxacin adsorption on polyethylene microplastics is multilayered. • Adsorption kinetic shows a pseudo-second order pattern. • The concentration and valence of heavy metals influence the adsorption process. • Toxicity of complex pollutants are mainly caused by metal ions and ciprofloxacin. [ABSTRACT FROM AUTHOR]

The fastest-growing microbe Vibrio natriegens is an excellent platform for bioproduction processes. Until now, this marine bacterium has not been examined for bioremediation applications, where the production of substantial amounts of biomass would be beneficial. V. natriegens can perform extracellular electron transfer (EET) to Fe(III) via a single porin-cytochrome circuit conserved in Vibrionaceae. Electroactive microbes capable of EET to Fe(III) usually also reduce toxic metals such as carcinogenic Cr(VI), which is converted to Cr(III), thus decreasing its toxicity and mobility. Here, the performance of V. natriegens was explored for the bioremediation of Cr(VI). At a density of 100 mg/mL, V. natriegens removed 5–20 mg/L Cr(VI) within 30 s and 100 mg/L Cr(VI) within 10 min. In comparison, the model bacterium Escherichia coli grown to a comparable cell density removed Cr(VI) 36 times slower. To eliminate Cr(VI), V. natriegens had to be metabolically active, and functional outer-membrane c -type cytochromes were required. At the end of the Cr(VI) removal process, V. natriegens had reduced all of it into Cr(III) while adsorbing more than half of the metallic ions. These results demonstrate that V. natriegens , with its fast metabolism, is a viable option for the rapid treatment of aqueous pollution with Cr. [Display omitted] • The fast-growing microbe Vibrio natriegens can reduce and adsorb toxic chromium. • High-density V. natriegens removed 5–20 mg/L Cr(VI) within 30 s. • V. natriegens at the same density also removed 100 mg/L Cr(VI) within minutes. • Cr(VI) was reduced extracellularly and Cr(III) was adsorbed by the microbes. • A porin-cytochrome complex is likely involved in Cr(VI) conversion. [ABSTRACT FROM AUTHOR]

With the development of industry, heavy metal (HM) pollution of soil has become an increasingly serious problem. Using passivators made of industrial by-products to immobilize HMs in contaminated soil is a promising in-situ remediation technology. In this study, the electrolytic manganese slag (EMS) was modified into a passivator (named M-EMS) by ball milling, and the effects of M-EMS on adsorption of As(V) in aquatic samples and on immobilization of As(V) and other HMs in soil samples were investigated under different conditions. Results demonstrated that M-EMS had a maximum As(V) adsorption capacity of 65.3 mg/g in the aquatic samples. Adding M-EMS to the soil reduced the leaching of As (from 657.2 to 319.8 μg/L) and other HMs after 30 d of incubation, reduced the bioavailability of As(V) and improved the quality and microbial activity of the soil. The mechanism for M-EMS to immobilize As in the soil are complex reactions, ion exchange reaction with As and electrostatic adsorption. This work provides new ideas of using waste residue matrix composites for sustainable remediation of Arsenic in the aquatic environment and soil. [Display omitted] • A novel EMS/pyrite-based passivator (M-EMS) was developed. • M-EMS can passivate As and other heavy metals in soil and reduce their bioavailability. • The immobilization mechanisms include precipitation, adsorption, and ion exchange. [ABSTRACT FROM AUTHOR]

Arsenic-containing wastewater and arsenic-contaminated soils can cause serious environmental pollution. In this study, mixtures of electrolytic manganese residues (EMRs) and calcite were superheated to different temperatures to prepare a novel passivator for arsenic [As(V)] removal in an aqueous environment, as well as for passivating As and other heavy metals (HMs) (e.g. Cr, Cd, and Pb) in the soil. The results showed that the optimal passivator superheated at 800 °C (C-EMR-800) and had a maximum As(V) adsorption capacity of 35 mg/g in solution. The excellent adsorption performance could be modelled using a second-order kinetic model, which demonstrated that adsorption is more consistent with chemisorption. The leaching concentration of As in contaminated soil amended with C-EMR-800 was reduced from 62.81 to 5.84 μg/L within 10 d, which is lower than that of the Chinese national standard (GB/T 5085.3–2007); C-EMR-800 also showed excellent passivating effects on other HMs (Cr, Cd, and Pb). The mechanisms for As removal by C-EMR-800 are linked to chemical reactions (e.g. precipitation), adsorption, and microbial passivation. Collectively, this study demonstrates an eco-friendly "waste-to-soil remediation" strategy that can address issues related to the reutilization of solid waste and remediation of HM-contaminated soil. [Display omitted] • A novel EMR/calcite-based passivator (C-EMR-800) was developed. • C-EMR absorbed As(V) in solution and passivated As, Pb, Cd, and Cr in soil. • Mechanisms for HMs removal include precipitation, adsorption and microbial passivation. • Solid waste reutilization and remediation of HM-contaminated soil were addressed. • The function of the microbial community is altered for soil remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • ECS as a substrate for S-nZVI can effectively avoid agglomeration. • S-nZVI@ECS can effectively remove Cd(II), Cu(II) and Pb(II) in a wide pH range. • The mechanisms include reduction, complexation, and precipitation. • Cu(II) and Pb(II) removal are almost unaffected in the presence of Cd(II). Exhausted copper slag (ECS) is an industrially utilized secondary waste, and due to its large volume and potential environmental risks, the utilization of ECS in a safe manner is required. In this study, a novel synthetic composite (S-nZVI@ECS) was prepared by loading sulfidized nanoscale zerovalent iron (S-nZVI) onto ECS for the removal of Cd(II), Cu(II), and Pb(II) from aqueous solutions. The composite not only provides a new idea for utilizing ECS but also prevents S-nZVI particles from agglomerating. The optimized S-nZVI@ECS can achieve efficient removal of the three heavy metals over a wide pH range without being affected by coexisting ions (Na+, K+, Mg2+, Ca2+). With the respective maximum adsorption capacities of these three cationic heavy metals being as high as 173.01, 93.81, and 338.98 mg/g (based on the Langmuir model), the elimination of S-nZVI@ECS for these three cationic heavy metals could be fitted with the Langmuir and Freundlich models well, and the associated mechanisms (including redox reactions, complexation, and precipitation) were elucidated. The novel S-nZVI@ECS composites prepared in this study using secondary waste as a substrate have good potential for removing cationic heavy metals from aqueous solutions. [ABSTRACT FROM AUTHOR]