Degradation of 2,4,6-trichlorophenol in aqueous systems through the association of zero-valent-copper-mediated reduction and UVC/H2O2: effect of water matrix and toxicity assessment

Biochar-supported sulfurized nanoscale zero-valent iron facilitates extensive dechlorination and rapid removal of 2,4,6-Trichlorophenol in aqueous solution

Nanoscale zero-valent iron (NZVI) has been widely used in rapid remediation of contaminants. However, several obstacles such as aggregation and surface passivation hampered NZVI from further application. In this study, sulfurized nanoscale-zero valent iron supported by biochar (BC-SNZVI) was successfully synthesized and utilized for highly efficient 2,4,6-Trichlorophenol (2,4,6-TCP) dechlorination in aqueous solution. SEM-EDS analysis revealed the even distribution of SNZVI on the surface of BC. FTIR, XRD, XPS and N₂ Brunauer-Emmett-Teller (BET) adsorption analyses were carried out to characterize the materials. Results showed that BC-SNZVI with S/Fe molar ratio of 0.088, Na₂S₂O₃ as sulfurization agent, and pre-sulfurization as the sulfurization strategy exhibited the superior performance for 2,4,6-TCP removal. The overall removal of 2,4,6-TCP was well described with the pseudo-first-order kinetics (R² > 0.9), and the observed kinetics constant K_obs was 0.083 min^-1 with BC-SNZVI, which was one order of magnitude higher than that of BC-NZVI (0.0092 min^-1) and SNZVI (0.0042 min^-1), and two orders of magnitude higher than that of NZVI (0.00092 min^-1). Moreover, the removal efficiency of 2,4,6-TCP reached 99.5% by BC-SNZVI with dosage of 0.5 g·L^-1, initial 2,4,6-TCP concentration of 30 mg·L^-1 and initial solution pH of 3 within 180 min. The removal of 2,4,6-TCP by BC-SNZVI was acid-promoted and the removal efficiencies of 2,4,6-TCP decreased with the increase of initial 2,4,6-TCP concentrations. Furthermore, more extensive dechlorination of 2,4,6-TCP was achieved with BC-SNZVI and complete dechlorination product phenol became predominant. The facilitation of sulfur for Fe⁰ utilization and electron distribution in the presence of biochar remarkably enhanced the dechlorination performance of BC-SNZVI for 2,4,6-TCP. These findings provide insights into BC-SNZVI as an alternative engineering carbon based NZVI material for treating chlorinated phenols.

Oxidation towards enrofloxacin degradation over nanoscale zero-valent copper: mechanism and products

Enrofloxacin (ENR) is a widely used veterinary fluoroquinolone antibiotic and is frequently detected in water environments. The degradation of ENR was examined utilizing molecular oxygen mediation using nanometer zero-valent copper (nZVC) as the catalyst in this work. The dosage of nZVC, initial pH, and reaction temperature were investigated as contributing factors to ENR degradation. The effects of Cl^-, NO^3-, SO4^2-, and humic acid on the degradation of ENR were investigated. The actual effects were evaluated using natural water. The reactive oxygen species (ROS) that participated in the reaction were identified, their generation mechanisms were elucidated, and the effects on ENR degradation were assessed. More emphasis was given to exploring ENR degradation and transformation pathways via analyses of HPLC-TOF-MS. Data showed that at 35 ℃, with an initial pH of 3 and exposed to air, an nZVC dose of 0.5 g·L^-1 degraded ENR by 99.51% dramatically. HO^• radicals were identified as the dominant ROS, and conversions among Cu⁰, Cu⁺, and Cu²⁺ played crucial roles in the generation of ROS. The destruction mechanism of ENR was speculated based on analyses of HPLC-TOF-MS results as the transformation of the piperazine ring into an oxidized state with a -COOH substitution with HO^•, which caused ENR to be mineralized and converted into CO₂, H₂O, and [Formula: see text]. The ECOSAR program has been used to evaluate the toxicity of ENR and its degradation products, and oxidative degradation of nZVC significantly reduced its toxicity and increased its biodegradability. This research proposes a capable and practical method for removing ENR from water.

The Influence of Copper on Halogenation/Dehalogenation Reactions of Aromatic Compounds and Its Role in the Destruction of Polyhalogenated Aromatic Contaminants

The effect of copper and its compounds on halogenation and dehalogenation of aromatic compounds will be discussed in the proposed article. Cu oxidized to appropriate halides is an effective halogenation catalyst not only for the synthesis of halogenated benzenes or their derivatives as desired organic fine chemicals, but is also an effective catalyst for the undesirable formation of thermodynamically stable and very toxic polychlorinated and polybrominated aromatic compounds such as polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans accompanied incineration of waste contaminated with halogenated compounds or even inorganic halides. With appropriate change in reaction conditions, copper and its alloys or oxides are also able to effectively catalyze dehalogenation reactions, as will be presented in this review.