Piezocatalytic degradation of organic dyes and production of H2O2 with hydroxyapatite

Hydroxyapatite (HAP) is a widely available and environmentally friendly material that exhibits excellent biocompatibility and versatile physicochemical properties, hence it has drawn a great deal of recent research interests. However, its piezoelectric properties have not been fully exploited so far. The aim of present work is to develop a facile method to prepare HAP with good piezoelectric activity and explore its potential application in the degradation of organic pollutants and production of H2O2. In present work, the HAP was prepared by a simple chemical precipitation followed by calcination at 200 ℃ in atmospheric condition. The piezocatalytic activity of HAP was investigated by the degradation of organic dyes and the production of H2O2. The factors that affect the piezocatalytic degradation, including the dose of catalyst, dye concentration, temperature, initial pH, and ultrasonic power were systematically studied. In the optimized condition, the degradation rates of 92%, 88%, 86% and 90% are readily obtained for 5 mg/L rhodamine B (RhB), methylene blue (MB), methyl orange (MO) and crystal violet (CV) respectively in 30 min ultrasonic treatment. The reaction mechanism was studied by tree radical tests and electron spin resonance (ESR) spectra and results confirmed that •OH plays the key role in the degradation reaction. The production of H2O2 was also preliminarily evaluated, an accumulated concentration of 152.24 μmol/L H2O2 was achieved in pure water within 30 min. The stability study showed that the HAP can maintain its piezocatalytic performance for at least 4 times of recycle experiments. Thus the HAP obtained from a simple synthetic method has a great potential in the application for wastewater purification and H2O2 production.