Removal of hydrochlorothiazide micropollutant from synthetic pharmaceutical effluent by ionic flocculation

Abstract

Emerging pollutants (EPs) have recently been reported to affect the quality of water and pose high risks to human health. The recalcitrant behavior of the drug hydrochlorothiazide (HCT) in wastewater, for example, highlights the need to develop new treatments that are more efficient in removing this pollutant. In this study, the removal of hydrochlorothiazide from a synthetic pharmaceutical effluent through micellar ionic flocculation was evaluated, using a biodegradable anionic surfactant, derived from natural materials such as coconut oil and animal fat. The effects of different parameters, such as contact time, stirring speed, temperature, surfactant concentration and pH on drug removal efficiency were assessed. Under optimal processing conditions: [HCT] = 20 ppm, [surfactant] = 300 ppm, 1:2 calcium/surfactant ratio, temperature 30 °C, contact time 5 min, fast stirring speed 100 rpm, slow stirring speed 50 rpm and pH 10, HCT removal efficiency reached 88%, indicating that ionic flocculation using base soap is a promising technique in the treatment of pharmaceutical effluents contaminated by hydrochlorothiazide. The desorption kinetics of HCT from the floc surface were also analyzed, confirming that desorption is governed by the pseudo-second order, where interactions between the polar group of the base soap (COOH−), Ca+2 ions and HCT (C7H8ClN3O4S2) detach the HCT molecules present in the flocs. Moreover, 15% of HCT was spontaneously desorbed after 40 min.