Comprehensive treatment of aroma chemicals industrial effluent with substantial COD content by a novel PVP/polyamide composite hydrophilized RO membrane

Abstract

A hydrophilized polyvinyl pyrrolidone/polyamide composite high rejection reverse osmosis (HPA-HR RO) membrane was used for the treatment of aroma chemicals containing effluent coming as multiple effect evaporators (MEE) condensate at UK Aromatics Pvt. Ltd., Boisar, Maharashtra. The unique membrane has an active composite layer of polyamide prepared by interfacial polymerization of high diamine (3%) and acid chloride (0.2%) monomer concentrations, which is further coated with polyvinyl pyrrolidone (PVP) to enhance hydrophilicity and chemical inertness. The plant provides removal of total dissolved solids (TDS) from 2500 to 3500 ppm in the feed to a value of 50–100 ppm in the permeate water indicating a rejection of more than 95% of the dissolved solids, with a high water recovery of 80% in permeate. Similarly, complete rejection of color was observed from dark brown to colorless (transparent), whereas the COD content was brought down from 3000 to 5000 mg/L in the MEE condensate to around 1000 mg/L indicating removal of 60 % to 80% depending upon the pressure applied to overcome the high osmotic pressure of the effluent. Physicochemical interactions between the PVP and polyamide skin layers of the composite membrane make the separating barrier durable and highly hydrophilic. Water would have greater sorption due to high affinity with the membrane and higher diffusion coefficient from its smaller size, while the less polar esters that constitute most of the COD would have low interaction and their larger molecular sizes make them less diffusive. The recovered permeate water has been reused in various internal industrial applications like cooling towers, cleaning, etc. at UK Aromatics.