Rejuvenating polyamide reverse osmosis membranes by tannic acid treatment

Abstract

Reverse osmosis (RO) is an efficient and often used technique for water desalination and industrial demineralized water production. The use of polyamide based membranes provides higher permeate fluxes than other polymers, while the resistance to oxidant agents is very low. The efficient lifetime of polyamide membranes varies between 3 and 5years. To improve this lifetime, the membranes can be submitted to a chemical treatment that could recover permeate flux and salt rejection characteristics. The purpose of this work is to investigate the efficiency of a rejuvenation procedure using tannic acid as a rejuvenating agent. The experiments were performed in a bench scale RO system with two different commercial polyamide membranes. Several conditions were analyzed, including tannic acid concentration, solution pH, transmembrane pressure and membrane cleaning conditions. Saline rejection and permeate flux were the parameters used to evaluate the efficiency of the process. The results obtained in the bench scale experiments were used to perform a test in an industrial membrane module that had been operating in an industrial demineralization plant for 5years. The effects of the operating conditions of membrane cleaning on the efficiency of the rejuvenation treatment are also provided.