Photocatalytic geopolymer membranes from Indonesian fly ash: TiO2 integration, stability, and methylene blue degradation

This study reports TiO 2 -modified geopolymer membranes synthesized from Indonesian Class C and F fly ash for methylene blue (MB) degradation. TiO 2 (0–5 wt%) improved compressive and flexural strength, with Class C showing faster setting and higher strength at 3 wt% TiO 2 . MB removal reached up to 99.3 %, although permeability declined with increased TiO 2 . UV-assisted regeneration restored membrane performance over three filtration cycles, demonstrating self-cleaning capability. These findings highlight the potential of fly ash-based photocatalytic geopolymer membranes for wastewater treatment applications. • Methylene blue (MB) removal reaches 99.3 % (Class C) and 98.6 % (Class F) with 5 wt% TiO 2 . • UV-assisted self-cleaning restores permeability over three filtration cycles. • TiO 2 -geopolymer membranes show strong potential for wastewater treatment. • Optimized TiO 2 dosage balances strength, MB removal, and filtration efficiency. • With addition of 5 % TiO 2 , Class C sets 17 × faster than Class F fly ash; TiO 2 enhances setting but reduces permeability.