End-of-life RO membranes recycling: Reuse as NF membranes by polyelectrolyte layer-by-layer deposition

Abstract

Nowadays, end-of-life (EoL) reverse osmosis (RO) membranes are considered as waste, hence they are incinerated or discarded in landfills. Due to the environmental problem of disposed membranes, their reuse as nanofiltration (NF) membranes was studied in this study. At first, the fouling of EoL membrane was cleaned and then the effect of sodium hypochlorite (NaOCl) on removing the polyamide (PA) layer and pure water permeability (PWP) of EoL membranes was investigated. With regard to NaOCl exposure intensities, three groups of EoL membranes with PWP of about 10, 20, and 30 L/(m 2 h bar) were selected as substrates to convert them to NF membranes by deposition of polyelectrolyte (PE) multilayers. The effects of PE type, substrate permeability, and the charge of outer layer on the performance of the resultant NF membranes were studied. As one of the best results, NF membrane composed of eight bilayers of SC498/KE253 polyelectrolytes on substrates with PWP of 18 L/(m 2 h bar) had salt water permeability (SWP) of 11 L/(m 2 h bar) and 94% rejection of MgSO 4 . Other results are also competitive with commercial NF membranes. The maximum NaCl and MgSO 4 rejection of prepared membranes were 92% and 98%, respectively, at a feed pressure of 10 bar. In addition, the stability test showed that the prepared membranes are stable over a long period of filtration.

Fouling is the beginning: upcycling biopolymer-fouled substrates for fabricating high-permeance thin-film composite polyamide membranes

“…Environmental engineers and material scientists have attempted downcycling end-of-life high pressure reverse osmosis/nanofiltration (RO/NF) membranes into NF/ultrafiltration (UF) membranes after appropriate treatment (Fig. 1A) (12,13). Nevertheless, for fouled/end-of-life low pressure membranes (MF/UF), how to recycle these membranes in a cost-effective and technically feasible way remains a great challenge.…”

Electrospun Nanostructured Membrane Engineering Using Reverse Osmosis Recycled Modules: Membrane Distillation Application

“…This type of RO membrane was recycled using PA oxidizing agents such as sodium hypochlorite (NaOCl) to fully or partially degrade the PA layer responsible of irreversible fouling [ 8 , 10 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. By applying different exposure doses to the oxidizing agent, quantified by units of parts per million of NaOCl used in the cleaning solution multiplied by the exposure time in hours (ppm·h), discarded RO membranes have been transformed to membranes for microfiltration (MF), ultrafiltration (UF) or nanofiltration (NF) separation processes [ 10 , 13 , 15 , 16 , 17 , 18 , 23 ]. In other research studies, after exposing the RO modules to NaClO oxidizing aqueous solution, the membranes were transformed to anion or cation exchanged membranes for electrodialysis (ED) or to microsystin-degrading biofilms for membrane bioreactors by applying adequate approaches [ 19 , 20 , 21 , 22 , 24 ].…”

Recycling of Spent Reverse Osmosis Membranes for Second Use in the Clarification of Wet-Process Phosphoric Acid

“…In this study, a process is reported that allows for the recycling of spent membranes taken from seawater desalination plants or similar plants and their reuse them as microfiltration or ultrafiltration membranes. The recycling is based on the removal of both the fouling and active layers of spent membrane using a suitable stripper to avoid damaging the microporous layer of the membrane [16]. The regenerated membrane was subjected to clarification of a WPPA to access its performance in terms of flux and rejection of suspended particles and organic matter.…”