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Electro-activated persulfate has displayed good performance in the oxidation of antibiotic pollutants in wastewater. However, high power consumption and the introduction of excessive sulfate ions hinder the application of this technology. This research provided a novel strategy for the applications of small power supply and simple devices in antibiotic pollutant treatment. It has been confirmed that sulfate radical ( SO 4 ∙ - ) could be generated at the boron-doped diamond (BDD) anode in both low and high current conditions. This study proposed a novel low current density electrochemical technology assisted by peroxymonosulfate (PMS) for the degradation of antibiotics. Adding 1 mg/L PMS at current density as low as 1.25 mA/cm2 increased the electro-oxidation rates of ciprofloxacin 5-fold from 1.92 ± 0.67 h−1to 9.70 ± 0.10 h−1. According to the Butler-Volmer equation, the introduction of PMS changed the mechanism of electrode reactions, thermodynamic properties of the system therefore changed. The electron spin resonance (ESR) test has confirmed that hydroxyl radical (•OH), SO 4 ∙ - , and singlet oxygen (1O2) are all generated in low current electrochemical systems. Quenching experiments illustrate that both radical and non-radical ways play essential roles in electro-oxidation processes. The contribution rates of •OH, SO 4 ∙ - , and 1O2 were 15.6%, 33.2%, and 40.5%, respectively. An oxidation peak was observed in cyclic voltammetry (CV) around +1.2 V, indicating that PMS electrolyte may drive oxidation at this potential. Besides, the reaction pathways of ciprofloxacin were speculated. Four transformation pathways including stepwise piperazine ring cleavage, OH/F substitution, cyclopropane ring cleavage, and decarboxylation were proposed for ciprofloxacin degradation. [ABSTRACT FROM AUTHOR]

The direct biological treatment of high concentrations of toxic organics in landfill leachate represents a formidable challenge. Given the excellent performance of adsorption and catalytic oxidation of sulfonated cobalt phthalocyanine / activated carbon (CoSPc/AC), this study investigated the removal of chemical oxygen demand (COD) from landfill leachate by CoSPc/AC under different conditions of temperatures, carrier particle sizes and concentrations. The response surface model further optimized the experimental conditions. Under conditions of 60 °C temperature, 50 mesh carrier particle size, and 14,697 mg/L influent COD, the predicted COD removal efficiency reached a maximum of 79.25%. The catalysts were characterized by X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy. It was revealed that the adsorption of COD in landfill leachate by activated carbon was primarily by physical adsorption, and the adsorbed organic matters were attached to a fixed point outside the activated carbon until the adsorption equilibrium was reached. The catalytic oxidation of COD mainly depends on CoSPc-O2−, CO3+ and sulfonic acid groups which had strong oxidizing properties after activation. The carrier-catalyst prepared in this study had high adsorption capacity of activated carbon as well as a good chemical oxidation capacity.Article Highlights: CoSPc/AC is more suitable for the pretreatment of landfill leachate. The adsorption mainly proceeded via physical adsorption. The catalytic oxidation mainly depended on CoSPc-O2-, Co3+ and sulfonic acid groups. [ABSTRACT FROM AUTHOR]

In this paper, a ruthenium/titanium dioxide (Ru/TiO2) composite photocatalyst was successfully prepared with the sol–gel method. The composite catalysts were characterised by UV–Vis diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. After being immobilised, the photocatalyst showed good photocatalytic activity and removed the ammonia molecules in the ultraviolet visible light region. The experimental results of ammonia nitrogen removal showed that the Ru/TiO2 photocatalyst removes ammonia molecules with high efficiency under UV irradiation at a wavelength of 365 nm. Finally, through experimental analysis of NO2− and NO3− production in the process of photocatalytic oxidation, the mechanism of ammonia nitrogen removal and the reduction of nitrate nitrogen in the process of photocatalytic oxidation are proposed. Under high-intensity light, NH4+ can be effectively removed, while photogenerated electrons have a reduction effect on NO3− and the generation of NO3− can be controlled. [ABSTRACT FROM AUTHOR]