Templating agent-mediated Cobalt oxide encapsulated in Mesoporous silica as an efficient oxone activator for elimination of toxic anionic azo dye in water: Mechanistic and DFT-assisted investigations

Boosting elimination of sunscreen, Tetrahydroxybenzophenone (BP-2), from water using monopersulfate activated by thorny NanoBox of Co@C prepared via the engineered etching strategy: A comparative and mechanistic investigation

As sunscreens, benzophenones (BPs), are regarded as emerging contaminants, most of studies are focused on removal of 2-hydroxy-4-methoxybenzophenone (BP-3), which, however, has been employed for protecting skin. Another major class of BPs, which is used to prevent UV-induce degradation in various products, is completely neglected. Thus, this present study aims to develop a useful advanced oxidation process (AOP) for the first time to eliminate such a class of BP sunscreens from contaminated water. Specifically, 2,2',4,4'-Tetrahydroxybenzophenone (BP-2) would be focused here as BP-2 is intensively used in perfumes, lipsticks, and plastics for preventing the UV-induced degradation. As monopersulfate (MPS)-based AOP is practical for degrading emerging contaminants, a facile nanostructured cobalt-based material is then developed for maximizing catalytic activities of MPS activation by immobilizing Co nanoparticles onto carbon substrates. In particular, ZIF-67 is employed as a template, followed by the etching and carbonization treatments to afford the thorny nanobox of Co@C (TNBCC) with the hollow-nanostructure. In comparison to the solid (non-hollow) nanocube of Co@C (NCCC) from the direct carbonization of ZIF-67, TNBCC possesses not only the excellent textural features, but also superior electrochemical properties and highly reactive surfaces, making TNBCC exhibit the significantly higher catalytic activity than NCCC as well as Co₃O₄ in activating MPS to degrade BP-2. Mechanisms of BP-2 degradation are also elucidated and ascribed to both radical and non-radical routes. These advantageous features make TNBCC a useful catalyst of activating MPS in BP-2 degradation.

Degradation of tartrazine by Oxone® in the presence of cobalt based catalyst supported on pillared montmorillonite - Efficient technology even in extreme conditions

The catalytic degradation of hazardous organic contaminants in industrial wastewater is a promising technology. Reactions of tartrazine, the synthetic yellow azo dye, with Oxone® in the presence of catalyst in strong acidic condition (pH 2), were detected by using UV-Vis spectroscopy. In order to extend the applicability profile of Co-supported Al-pillared montmorillonite catalyst an investigation of Oxone® induced reactions were performed in extreme acidic environment. The products of the reactions were identified by liquid chromatography-mass spectrometry (LC-MS). Along with the catalytic decomposition of tartrazine induced by radical attack (confirmed as unique reaction path under neutral and alkaline conditions), the formation of tartrazine derivatives by reaction of nucleophilic addition was also detected. The presence of derivatives under acidic conditions slowed down the hydrolysis of tartrazine diazo bond in comparison to the reactions in neutral environment. Nevertheless, the reaction in acidic conditions (pH 2) is faster than the one conducted in alkaline conditions (pH 11). Theoretical calculations were used to complete and clarify the mechanisms of tartrazine derivatization and degradation, as well as to predict the UV-Vis spectra of compounds which could serve as predictors of certain reaction phases. ECOSAR program, used to estimate toxicological profile of compounds to aquatic animals, indicated an increase in the harmfulness of the compounds identified by LC-MS as degradation products from the reaction conducted for 240min. It could be concluded that an intensification of the process parameters (higher concentration of Oxone®, higher catalyst loading, increased reaction time, etc.) is needed in order to obtain only biodegradable products.

Efficient and selective removal of Hg(II) from water using recyclable hierarchical MoS2/Fe3O4 nanocomposites

Developing practical and cost-effective adsorbents with satisfactory mercury (Hg) remediation capability is indispensable for aquatic environment safety and public health. Herein, a recyclable hierarchical MoS₂/Fe₃O₄ nanocomposite (by in-situ growth of MoS₂ nanosheets on the surface of Fe₃O₄ nanospheres) is presented for the selective removal of Hg(II) from aquatic samples. It exhibited high adsorption capacity (∼1923.5 mg g ^-1), fast kinetics (k₂ ∼ 0.56 mg g ^-1 min^-1), broad working pH range (2-11), excellent selectivity (K_d > 1.0 × 10⁷ mL g ^-1), and great reusability (removal efficiency > 90% after 20 cycles). In particular, removal efficiencies of up to ∼97% for different Hg(II) concentrations (10-1000 μg L ^-1) in natural water and industrial effluents confirmed the practicability of MoS₂/Fe₃O₄. The possible mechanism for effective Hg(II) removal was discussed by a series of characterization analyses, which was attributed to the alteration of the MoS₂ structure and the surface coordination of Hg-S. The accessibility of surface sulfur sites and the diffusion of Hg(II) in the solid-liquid system were enhanced due to the advantage of the expanded interlayer spacing (0.96 nm) and the hierarchical structure. This study suggests that MoS₂/Fe₃O₄ is a promising material for Hg(II) removal in actual scenarios and provides a feasible approach by rationally constructing hierarchical structures to promote the practical applications of MoS₂ in sustainable water treatments.