# Recycled Polystyrene as a Sustainable Material for Hollow Fiber Membranes in Dye Filtration

## TL;DR

This paper shows how recycled polystyrene can be used to make efficient hollow fiber membranes for filtering dyes from water.

## Contribution

A novel method to repurpose expanded polystyrene waste into high-performance membranes for dye filtration.

## Key findings

- Membranes with up to 30% recycled EPS showed no polymer segregation and improved compatibility.
- Water flux increased significantly with higher sEPS content, reaching 21.2 L m−2 h−1 at 2 bar.
- The 80/20s membrane achieved 98.3% rejection of Reactive Black 5 dye.

## Abstract

Expanded polystyrene (EPS) waste was chemically modified by sulfonation to obtain sulfonated EPS (sEPS), which was subsequently blended with virgin polyphenylsulfone (PPSU) at concentrations ranging from 10 to 50% to elaborate hollow fiber membranes for dye removal. The membranes were elaborated by non-solvent-induced phase separation and characterized by scanning electron microscopy, mechanical properties, antifouling, water flux measurements, and dye rejection performance. Scanning electron microscopy images of PPSU/sEPS blends showed well-defined membrane cross-sections with no polymer segregation up to 30% recycled EPS content, indicating improved compatibility due to EPS sulfonation. The HFMs present mean pore radii ranging from 4.2 ± 0.5 to 11.1 ± 1.0 nm with porosity up to 80%. Water flux improved significantly from 3.1 to 21.2 L m−2 h−1 at 2 bar as sEPS content increased. Dye rejection performance was promising, with Reactive Black 5 rejection ranging from 77% to 99%. The 80/20s PPSU/sEPS membrane showed the highest Reactive Black 5 rejection at 98.3% and revealed a 70.3% rejection in a 24 h dye mixture test. Furthermore, the 70/30s displayed superior anti-fouling properties, achieving a 99.3% flux recovery ratio in a xanthan gum solution at 2 bar. This study demonstrates a novel approach to transform EPS waste into high-performance hollow fiber membrane with competitive antifouling and dye separation properties.