Novel Ag@NH2-UiO-66(Zr) photocatalyst with controllable charge transfer pathways for efficient Cr(VI) remediation

NH2-MIL-125(Ti)/TiO2 heterojunction with non-disturbed dual reactive centers for synchronous photocatalytic removal of Cr(VI) and organic dyes

Chromium (VI) (Cr(VI)) generally coexists with organic dyes in industrial effluents, posing a formidable challenge in water purification. Herein, NH2-MIL-125(Ti)/TiO2 Z-scheme heterojunction with intimate interfacial contact was synthesized for synchronous removal of pollutant in coexisting Cr(VI)/dyes system under simulated solar irradiation. Structural and optical investigations indicated that a well-defined interface was formed by establishing a Ti-N-C bond, facilitating the spatial separation of the photoexcited carriers of the Z-scheme heterojunction. The optimum NH2-MIL-125(Ti)/TiO2 nanocomposites show superior performance in photocatalytic removal of the pollutants in the Cr(VI) (5 mg/L, 97.2%)/MB (40 mg/L, 100%) coexistence systems within 120 min, which is comparable to that in the single system. The electron spin resonance (ESR) tests, radicals scavenging experiments, and density functional theory (DFT) cannulations unveiled that TiO2 could serve as oxidation centers to generate hydroxyl radicals (•OH) for MB oxidation, while the NH2-MIL-125(Ti) with exposed Ti nodes could act as reduction centers to effectively adsorb Cr2O72- and inject photo-generated electrons (e-) to accomplish the in-site photoreduction of Cr(VI) into Cr(III) under illumination. Particularly, owing to the spatial separation and non-disturbed dual reactive centers, the reduction and oxidation processes could be well accommodated, which could allow MB and Cr(VI) to be removed synchronously. This work demonstrated the great potential of applying duel reactive centers to eliminate multipollutant simultaneously in the actual scenarios for wastewater treatment.

FeS-based nanocomposites: A promising approach for sustainable environmental remediation - Focus on adsorption and photocatalysis - A review

Population expansion, industrialization, urban development, and climate changes increased the water crisis in terms of drinking water availability. Among the various nanomaterials for nanoremediation towards water treatment, FeS-based nanocomposites have emerged as promising candidates in the adsorptive and photocatalytic removal of contaminants. This paper, therefore, evaluates the potential of FeS-based nanocomposites for environmental applications, more specifically the combined use of adsorption and photocatalysis. Pyrite and mackinawite structures outcompeted the other FeS configurations due to their large surface areas, numerous active sites, and enhanced conductivity, factors that enhance the adsorption and photovoltaic processes. To improve photocatalytic performance FeS requires modification with additional materials. Various fabrication strategies (including hydrothermal method, co-precipitation, electrochemical anodization, electrospinning, impregnation, green synthesis, mechanochemical approach/ball milling) of FeS-based composites and their efficacy and the mechanisms for removing organic and inorganic pollutants are reviewed in this paper. The structural characteristics of FeS scaffolds play a crucial role in the effective removal of heavy metals, such as Hg and Cr ions, primarily through ion exchange and surface complexation. Organic pollutants such as methylene blue and tetracycline were effectively degraded by advanced oxidation processes (AOPs). A large scale applications of FeS include industrial wastewater treatment, groundwater remediation towards trichloroethylene and other organic solvents removal, municipal wastewater, oil spills cleanup, pre-treatment for seawater desalination. Current challenges relate to catalysts stability, their removal after treatment stage, recycling, metals leaching and up-scaling as well as high effectiveness in real case-scenario and costs optimization. In summary, this review will help to advance research in the field of environmental remediation using FeS-based nanocomposites.

Efficient photocatalytic degradation of antibiotics using Z-scheme MIL-88(Fe)/Ti3C2/MoO3: Mechanistic insights and toxicity assessment

Antibiotic residues cause water contamination and disrupt aquatic ecosystems. Herein, we reported the fabrication of a novel Z-scheme heterojunction, MIL-88A(Fe)/Ti3C2/MoO3 (MTO), for safe and efficient removal of antibiotics. Ti3C2 was introduced into the MIL-88A(Fe)/MoO3 (MO) heterojunction as an electronic mediator to accelerate charge separation. Consequently, the ternary MTO achieved a tetracycline (TC) degradation rate 2.5 times higher than that of MO. Notably, the MTO heterojunction maintained high TC degradation efficiency over 36 consecutive hours without significant decline. Photogenerated holes, hydroxyl radicals, and superoxide radicals synergistically led to efficient and deep mineralization of TC. Furthermore, toxicity assessments were performed using Toxicity Estimation Software Tool (T.E.S.T.), bacteria (S. aureus and E. coli) cultivation, wheat germination and cultivation. The results all confirmed the safe degradation of TC. Therefore, this study provides a promising strategy for photocatalytic removal of antibiotics and promotes sustainable water purification technologies.