Combination of tertiary solar photo-Fenton and adsorption processes in the treatment of hospital wastewater: The removal of pharmaceuticals and their transformation products

Abstract

In this work, the degradation of a mixture of nine pharmaceuticals was performed in near environmental concentrations (500 µg L−1) using hospital wastewater as the matrix and employing as a coupling strategy solar photo-Fenton (SPF) treatment followed by adsorption. Different SPF approaches were studied. The best condition chosen for the degradation of the pharmaceuticals by SPF was that which used an initial concentration of H2O2 of 100 mg L−1 and multiple additions of Fe2+ of 5 mg L−1 at times of t = 0, 5, and 10 min in hospital wastewater. Degradation of 80% was obtained for Fluconazole, whereas the degradation of other pharmaceuticals achieved 99% of primary elimination. Consequently, 38 Transformation Products (TPs) were generated by the SPF process. The combination of SPF with the adsorption process using avocado seed activated carbon (ASAC) as sorbent was used to prevent TPs reaching the aqueous environment. For this reason, the SPF process was stopped after 15 min; and within this time, the largest number of TPs (28 TPs) was observed. A volume of 20 mL of hospital wastewater (HWW) previously treated by SPF was combined with 14 mg ASAC, for 15 min of contact time. This coupling removed 30 of the 36 compounds (remaining pharmaceuticals and TPs), with an open-chain and highly polar TPs having a 50% and 60% removal for FLT TP2 and FLT TP3, respectively. With respect to compounds that present aromatic rings, these presented a 98–100% removal rate in the coupled processes, with π–π interactions as the main interaction mechanisms with ASAC.