Effect of mixed metal oxide-based catalysts for the removal of hydrophobic phthalates from water

Contaminants of emerging concern (CECs) such as phthalic acid esters (PAEs) are ubiquitous, toxic and persistent in aquatic environments. Current study explored mixed metal oxide catalysts derived from magnesium aluminium (MAH), magnesium aluminium ruthenium (MAR-H), magnesium aluminium nickel (MANH) hydroxides and copper aluminium hydroxides of ammonium (CAM-Am) and sodium molybdate (CAM-Na) to remove dibutyl phthalate (DBP) and di-2-ethyl hexyl phthalate (DEHP) from water. Powder X-ray diffraction (XRD) studies of the catalysts before and after the treatment showed that their structures were stable and robust. During Fourier Transform Infrared (FTIR) studies, vibrational bands or peaks of ester and alkane functional groups of DBP and DEHP were observed at all the catalysts after treatment. Thermogravimetric analysis (TGA) confirmed phthalate adsorption at the five catalysts. Hydrolysis of DBP and DEHP was observed during treatment using CAM-Am and CAM-Na that was analysed and quantified using total organic carbon (TOC), high performance liquid chromatography (HPLC) and high-resolution mass spectrometry (HRMS). From TOC analyses, optimal conditions of 500 mg L-1 catalyst dosage and 30 h treatment time were deduced for catalytic hydrolysis of DBP and DEHP. Present study illustrated that the catalysts MAH and MANH can adsorb PAEs while CAM-Na can adsorb and hydrolyse them. Conventional water and wastewater treatment systems are unable to remove hydrophobic phthalates efficiently. Hence, these compounds have become a grave concern. In the present work, phthalate removal from water using three types of magnesium-based and two types of copper-based catalysts was studied. The results will help to better understand how to utilize mixed metal oxides for water remediation. image