Study of adsorption-oxidative degradation of PAHs over organic–inorganic hybrid layered double hydroxides†
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are well-known hazardous pollutants. As a result, numerous methods have been designed and developed for their effective treatment. In this study, an adsorption-oxidation degradation process was explored for PAH degradation using CuZnFeAl layered double hydroxide (LDH), which was synthesized using a co-precipitation method. LDH was then subjected to high-temperature roasting to obtain CuZnFeAl layered double oxide (LDO), which was subsequently modified with a sodium dodecyl sulfate solution (SDS) to obtain SDS/LDO. Characterization studies substantiated that SDS/LDO was successfully modified. Naphthalene (Nap) and phenanthrene (PA) were used as PAH model pollutants and the degradation effects of different oxidants were evaluated. The results of adsorption-oxidation coupling degradation showed that the conversion rates of Nap and PA using ozone as an oxidant over SDS/LDO reached 98.5% and 99.9%, respectively. The kinetic study of the degradation of Nap and PA by adsorption-oxidation showed that the degradation of Nap and PA followed pseudo-first-order reaction kinetics. A mechanism study verified the existence of several free radicals, such as ˙OH, 1O2 and ˙O2−, which can continuously degrade PAHs. The degradation of Nap and PA gradually resulted in small organic molecular compounds, such as phenolic compounds, esters and alcohols, and were finally oxidized into H2O and CO2.