This study investigated the effects of fly ash loading on the characteristics of polyvinyl chloride (PVC) membranes for reverse electrodialysis (RED). The membranes were prepared by adding different concentrations of fly ash (0.5-2 wt%) to the casting solution. The surface chemistry of the prepared membranes was analyzed using Fourier transform infrared spectroscopy. The swelling degree (SD) was used as an indicator of the membranes' water uptake. Titration using NaOH (0.01 M) was performed to measure the membranes' ion exchange capacity (IEC) and conductivity. The PVC membrane with 2 wt% fly ash demonstrated the highest SD (83.78%), IEC (0.163 meq/g), and conductivity (8.7×10 −2 µS/cm). The results show that the presence of fly ash significantly affects the characteristics of PVC membranes for RED.