Efficient coating of titanium composite electrodes with various metal oxides for electrochemical removal of ammonia

A variety of coated titanium (Ti) electrodes were prepared for ammonia wastewater treatment. The influence of precursor salts in the prepared coatings of the titanium plate electrodes was investigated using thermal decomposition by different dissolved nickel (Ni), copper (Cu), tin (Sn), and antimony (Sb) chloride salts. The metal chlorides (tin chloride SnCl4·5H2O, nickel chloride NiCl2·6H2O, antimony chloride SbCl3, and cupric chloride CuCl2·2H2O) were dissolved in a suitable solvent to prepare three kinds of solutions with the following mole ratios: 98.2:1.6:0.2, Sn:Sb:Cu; 98.2:1.6:0.2, Sn:Sb:Ni; and 98.2:1.6:0.1:0.1, Sn:Sb:Cu:Ni. During the immersion, drying, and heating of the electrode to a specific temperature, chlorides were transformed to an oxide coating layer to form Ti/SnO2–Sb2O3–CuO–NiO (TSCN), Ti/SnO2–Sb2O3–NiO (TSN), and Ti/SnO2–Sb2O3–CuO (TSC) anodes. The structural properties and surface morphologies of the products were investigated by atomic force microscopy (AFM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The component of the coated layer was tested by energy dispersive spectroscopy (EDS), and the electrochemical performance was evaluated by cyclic voltammetry. In the present investigation, the batch electrochemical oxidation experiments were carried out using the three anodes and Cu/Zn cathode, at various operating parameters of, NaCl concentrations of 100, 200, 300, 400, 500, 1000, and 1500 ​mg/L, an initial ammonia concentration of 100 ​mg/L, a current density of 10 mA/cm2, and a pH of 7. Results revealed that the Ti electrode coated with the SnO2–Sb2O3–CuO anode had the highest anodic currents of 0.12 A, the smallest grain size of 40.76 ​nm, and the smallest crystal size of 18.1 ​nm. The results showed that after 60 ​min of electrolysis time, the coated electrode (TSC) possessed the best removal efficiency of 84.3% for the highest NaCl concentration studied of 1500 ​mg/L.