Catalytic oxidative degradation of paracetamol in water solutions over Al/Fe -pillared clay

Abstract

The performance of Al/Fe-pillared clay as a heterogeneous Fenton-type catalyst for the oxidative degradation of paracetamol was firstly studied in this research. The Al/Fe-pillared clay was synthesized by using bentonite and intercalating solution prepared by alkaline hydrolysis of a mixture of AlCl₃ and FeCl₃ (Al/Fe 10/1 mol/mol, OH/(Fe+Al) 2.0). The solid was then heated at 500 °C for 2 h and characterized by FTIR, XRD, SEM and low temperature nitrogen adsorption analysis. The clay pillarization resulted in the formation of micropores and a threefold increase in the specific surface area.The degradation rate was studied by the decrease in paracetamol concentration measured by HPLC. Al/Fe-pillared clay showed high activity in the Fenton degradation of paracetamol: the catalytic reaction rate increased 25 times compared to the non-catalytic reaction, which was caused by the formation of ∙OH and ∙HO₂ radicals, as shown by tests using radical scavengers. It was found that the rate and efficiency of paracetamol degradation depended on pH, the ratio of paracetamol and hydrogen peroxide concentrations, the catalyst content and temperature. The optimal conditions were determined, allowing to achieve high efficiency of paracetamol degradation and high catalyst stability (Fe leaching was less 1 ppm). 100% paracetamol removal was achieved in 90 min at pH 4.0, a stoichiometric amount of H₂O₂ ([H₂O₂]/[PCT] 21 mol/mol), 1 g/L catalyst, 50 °C. Al/Fe-pillared was used in three consecutive cycles without regeneration and loss of activity. The results showed that Al/Fe-pillared clay could be a promising heterogeneous Fenton catalyst for the removal of pharmaceutical pollutants from wastewater.