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Chemical inhibition of combined gypsum and iron oxides membrane fouling during reverse osmosis desalination process: Prevention and regeneration of membranes

2023; Elsevier BV; Volume: 551; Linguagem: Inglês

10.1016/j.desal.2023.116414

1873-4464

Emna Melliti, Bart Van der Bruggen, Hamza Elfil,

Fuel Cells and Related Materials

This paper explores the performance of carboxylic acids as environmentally friendly chemical inhibitors and cleaning agents during combined membrane fouling by gypsum and iron oxides. The efficiency of citric acid and two other carboxylic acids was evaluated during combined fouling trials by measuring normalized fluxes drops, using an RO pilot unit. The effect of acid concentration, pH variation and gypsum supersaturation were evaluated. SEM, EDX, X-Ray diffraction and FTIR were used to identify the composition and morphology of fouled membranes. The results indicated that at low pH, citric acid serves to restore the flux drop. This acid serves to orient the crystals towards the hemihydrate form with a flat, thin structure. By increasing the pH, the acid retains its effectiveness and serves to delay the Fe2+ oxidation ions and the precipitation of calcium sulfate for more than 3 h. By comparing them to the citric acid, ascorbic and tartaric acid showed a similar effect at acidic pH. In both cases, normalized fluxes were recovered with the use of 100 ppm of each acid. However, at alkaline pH, citric shows a better performance. The regeneration of RO membranes fouled by iron oxides and gypsum appears to be more effective with citric acid than the other two acids.