Synthesis of layered double hydroxide-based hybrid electrode for efficient removal of phosphate ions in capacitive deionization.

The removal of phosphate ions by capacitive deionization has become one of the most frontier research topics in the water treatment field in recent years. In this work, hybrid electrodes composed of nickel-iron layered double hydroxide (NiFe-LDH) - anchored on activated carbon fiber (ACF)-were synthesized by a hydrothermal method and subsequently applied in capacitive deionization to remove phosphate ions. The adsorption performance of the two hybrid electrodes on phosphate ions was compared by capacitive deionization experiments. The experiment was carried out for 3 hours to reach equilibrium, and the optimum adsorption of 33.48 mg/g was obtained using NiFe-LDH/ACF-2 hybrid electrode at room temperature (25 °C) and pH = 6.0. The results showed that increasing the loading capacity of NiFe-LDH on ACF might enhance the adsorption capacity of phosphate ions. Furthermore, the calculation of adsorption kinetics and adsorption isotherms elucidated that the adsorption capacity increased with the increasing of applied voltage. Meanwhile, the experimental data were fitted well with pseudo-first-order kinetics and Langmuir isotherms. Notably, it was observed that the pH first increased, then decreased during the adsorption due to the electrolysis of water, while the form of phosphate ions was transformed, with low pH favoring the adsorption of phosphate ions.

Enhanced electro-Fenton degradation of tetracycline in aqueous solution using a self-supported BiOCl/CF cathode.

The cathode material is critical to the yield of hydrogen peroxide (H2O2) and electro-Fenton (EF) performance. In this work, bismuth oxychloride (BiOCl) as one of the representatives of ternary oxides was grown in situ on carbon felt (CF) through a simple solvothermal method and employed directly as a self-standing cathode for the EF degradation of the target contaminant tetracycline (TC). TC can be almost completely degraded, up to 95% in 90 min under the heterogeneous EF process. The characterizations demonstrated that the BiOCl/CF electrode exhibited excellent conductivity due to CF as the supporting carbon material with a 3D network structure; meanwhile, this hybrid electrode also possessed abundant active sites attributed to the decorated BiOCl having rich oxygen defects. Finally, the rational reaction mechanism of TC was also elucidated by the X-ray photoelectron spectroscopy (XPS) spectrum, free radical quenching experiments and electron paramagnetic resonance (EPR) spectra, in which hydroxyl radicals (c OH) were considered as the dominant active oxidants and BiOCl had a synergistic effect on in-situ generation and decomposition of H2O2.