Recycling of end-of-life reverse osmosis membranes by oxidative treatment: A technical evaluation

Abstract

The adverse impacts caused by the disposal of thousands of tonnes per annum of reverse osmosis (RO) membranes modules have grown dramatically around the world. The objective of this study was to evaluate the technical feasibility of recycling by chemical oxidation of end-of-life RO membranes for applications in other separation processes with specifications less rigorous. The recycling technique consisted in to cause a membrane exposition with oxidant solutions in order to remove its aromatic polyamide layer and subsequent conversion to a porous membrane. The recycling technique was evaluated bywater permeability and salt rejection tests before and after the oxidative treatments. Initially, membranes' chemical cleaning and pretreatment procedureswere assessed. Among factors evaluated, the oxidizing agent, its concentration and pH, associated with the oxidative treatment time, showed important influence on the oxidation of the membranes. Results showed that sodium hypochlorite and potassium permanganate are efficient agents for the membrane recycling. The great increased permeability and decreased salt rejection indicated changes on membranes' selective properties. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and contact angle characterization techniques revealedmarked changes on themain membranes' physical-chemical properties, such asmorphology, roughness and hydrophobicity. Reuse of produced effluents and fouling tendency of recycled membranes were also evaluated.