Removal of pharmaceutical compounds from urine via chemical coagulation by green synthesized ZnO-nanoparticles followed by microfiltration for safe reuse

Abstract

In the present study green chemistry was employed for synthesizing ZnO nanoparticles using the extract of black tea solid waste and Zn acetate dihydrate. The characterization of the green synthesized ZnO was conducted by XRD, SEM, HR-TEM, DLS and EDAX. Urine samples from donors under medication with Ibuprofen, Ephedrine and Propranolol were separated and collected through a diversion toilet. A batch experiment was conducted in order to determine the optimum dose of green synthesized ZnO nanoparticles for the removal of the pharmaceutical compounds from human urine. The determined optimum dose of the ZnO nanoparticles was 1.5 g/l. ZnO nanoparticle possess the ability to adsorb the Pharmaceutical active compounds (PACs) on the surface. In addition, it binds such adsorbed particles and facilitates their precipitation. Coagulant reagents react with some of the suspended and colloidal particles in water/wastewater to enhance their binding together, thus, allowing their removal in the subsequent treatment processes. The mechanism of aggregation consists of the combination of charge neutralization, entrapment, adsorption and/or complexion with the coagulant ions to form insoluble precipitate. Thus, the particles and colloids can be removed. A semi-pilot plant consisted of mixing tank for chemical coagulation using the predetermined ZnO nanoparticles followed by microfiltration unit, was designed and operated continuously for the treatment of the separated urine. The overall results of the semi-pilot study showed that the concentration of Ibuprofen, Ephedrine and Propranolol decreased from 5.0, 10.15 and 15.2 mg/l to 0.01, 0.10 and 0.03 mg/l respectively. The overall removal rate exceeded 99%. Meanwhile, the treatment system succeeded to improve the physical and chemical characteristics of the contaminated human urine. The treated urine could be safely used for agriculture purposes without any environmental threat. Keywords: ZnO nanoparticles, Green synthesis, Pharmaceutical removal, Chemical coagulation, Urine safe reuse, Membrane microfiltration