Impact of residual aluminum on nanofiltration gypsum scaling: Mitigation roles played by different species

Residual aluminum (Al) is a growing pollutant in nanofiltration (NF) membrane-based drinking water treatment. To investigate the impact of distinct Al species fouling layers on gypsum scaling during NF, gypsum scaling tests were conducted on bare and three Al-conditioned (AlCl 3 -, Al 13 , and Al 30 -) membranes. The morphology of gypsum, the role of Al species on Ca 2+ adsorption during gypsum scaling, and the interactions between gypsum crystals and Al-conditioned membranes were investigated. Results indicated that Al-conditioned membranes had lower flux decline than the bare membrane, with the order of AlCl 3 -