Application of novel eco-friendly membranes prepared with recycled high-impact polystyrene to municipal wastewater treatment

In the frame of circular economy, plastic wastes could be used for producing eco-friendly membranes. Specifically, in this work, recycled high impact polystyrene (HIPS), whose world production reached 3.2 million metric tons in 2024, has been used for the manufacture of microporous membranes by the nonsolvent-induced phase separation (NIPS) method. Three different polymer concentrations were tested (20, 25 and 30% w/w) in the manufacture of the membranes. Two different lab scale plants with a dead-end cell and a cross-flow module, respectively, were used. The manufactured membranes were applied for the for the filtration of samples from effluents from secondary and primary treatments of a municipal wastewater treatment plant, which has not been reported previously in the bibliography, being a scientific novelty. Results with the dead-end cell drove to the selection of the membranes made with 20% of HIPS with and without thermal post-treatment. In the tests with secondary effluents, these membranes yielded permeates with enough quality to be reused in agriculture in terms of turbidity and microbial analysis (0 coliforms forming units of E. coli and turbidity lower than 1 NTU), fully comparable with those provided by commercial membranes. The membrane made with 20% of recycled HIPS with thermal post-treatment achieved chemical oxygen demand and turbidity removal efficiencies higher than 35 and 90%, respectively, in the application to primary effluent. Most of the membrane fouling was reversible.