Sodium hypochlorite and Cu-O-Mn/ columnar activated carbon catalytic oxidation for treatment of ultra-high concentration polyvinyl alcohol wastewater

Complete degradation of high concentration polyvinyl alcohol (PVA) is challenging. In this article, a two-stage process of NaClO pre-oxidation and columnar activated carbon (loaded with metal active components) catalytic oxidation was used to treat high concentration PVA wastewater. The degree of polymerization of PVA is 2400 and the water concentration is 15 wt %. In the first stage, NaClO efficiently broken long chain to short, the viscosity of PVA solution decreased from 45,100 mPaS to 4.65 mPaS. And in the second stage, the short chain was further oxidized to small molecules under H₂O₂ with catalysts. The solution COD decreased from 206,240 mg/L to 38.38 mg/L. The composition of catalysts and the reaction conditions were optimized, the degradation mechanism was discussed. According to the experimental results, small pore size (8-10 mesh) activated carbon loaded copper and manganese catalyst (C₁M₁AC-S) was the best choice. The optimal conditions of C₁M₁AC-S were: molar ratio of copper to manganese was 2:1, the loading rate was 25 wt% and the dosage was 9.76 mg/100 ml. The whole process is mild (25 °C-40 °C) and reaction time is short (100 min). Moreover, free radical scavenging experiments shown that the catalytic oxidation stage follows the mechanism of hydroxyl radical reaction.

Co-oxidative removal of arsenite and tetracycline based on a heterogeneous Fenton-like reaction using iron nanoparticles-impregnated biochar

A highly efficient, eco-friendly and relatively low-cost catalyst is necessary to tackle bottlenecks in the treatment of industrial wastewater laden with heavy metals and antibiotic such as livestock farm and biogas liquids. This study investigated co-oxidative removal of arsenite (As(III)) and tetracycline (TC) by iron nanoparticles (Fe NP)-impregnated carbons based on heterogeneous Fenton-like reactions. The composites included Fe NP@biochar (BC), Fe NP@hydrochar (HC), and Fe NP@HC-derived pyrolysis char (HDPC). The functions of N and S atoms and the loading mass of the Fe NP in the Fe NP@BC in heterogeneous Fenton-like reactions were studied. To sustain its cost-effectiveness, the spent Fe NP@BC was regenerated using NaOH. Among the composites, the Fe NP@BC achieved an almost complete removal of As(III) and TC under optimized conditions (1.0 g/L of dose; 10 mM H₂O₂; pH 6; 4 h of reaction; As(III): 50 μM; TC: 50 μM). The co-oxidative removal of As(III) and TC by the Fe NP@ BC was controlled by the synergistic interactions between the Fe NPs and the active N and S sites of the BC for generating reactive oxygen species (ROS). After four consecutive regeneration cycles, about 61 and 95% of As(III) and TC removal were attained. This implies that the spent carbocatalyst still has reasonable catalytic activities for reuse. Overall, this suggests that adding technological values to unused biochar as a carbocatalyst like Fe NP@BC was promising for co-oxidative removal of As(III) and TC from contaminated water.

Fenton-like degradation of sulfathiazole using copper-modified MgFe-CO3 layered double hydroxide

The catalytic activity of layered double hydroxides, with and without insertion of copper, was evaluated in a heterogeneous Fenton process for degradation of the antibiotic sulfathiazole (STZ). The characterizations with different techniques revealed lamellar structures formed by stacking of layers containing magnesium, iron, and copper cations. The insertion of copper in the lamellar structure increased the specific area of the material and the degradation kinetics, achieving complete STZ removal after 90 min. X-ray photoelectron spectroscopy analysis showed the presence of Cu(II) and Cu(I) surface sites, which contributed to the generation of hydroxyl and hydroperoxyl/superoxide radicals. It also indicated an increase of Cu(I) content after use. For both materials, but specially for LDH without copper, addition of tert-butyl alcohol and p-benzoquinone hindered STZ degradation, indicating the importance of hydroxyl and hydroperoxyl/superoxide radicals in the degradation process, respectively. These results demonstrated the potential of copper-modified MgFe-CO₃ as a catalyst for the degradation of emerging contaminants, offering the benefits of easy preparation and high efficiency in the Fenton process.

Rapid degradation of azo-dye using Mn–Al powders produced by ball-milling

This study was conducted on the reduction reaction of the azo dye Reactive Black 5 by means of the Mn₈₅Al₁₅ particles prepared by melt-spinning and ball-milling processes.