Evaluation of hydrolyzed poly(isobutylene-alt-maleic anhydride) as a polyelectrolyte draw solution for forward osmosis desalination

• Hydrolyzed poly(isobutylene-alt-maleic acid) (PIAM-Na) was synthesized and used as draw solute for FO desalination.
• Nontoxic PIAM-Na produced high osmotic pressure DS with low viscosity.
• PIAM-Na showed two Tg values well above the operation temperature of FO-MD hybrid process.
• 0.375 g/mL of PIAM-Na produced maximum flux with lowest RSF at AL-DS mode compared to conventional salt.

The forward osmosis (FO) desalination consisting of polyelectrolyte-based draw solution (DS) is gaining more interest due to low reverse solute flux (RSF) and easy DS recovery. In the current work, a novel solute for the DS was prepared by the base hydrolysis of poly(isobutylene-alt-maleic anhydride) (IBMA) using NaOH. The hydrolyzed product, i.e., sodium salt of IBMA (IBMA-Na), was dissolved in deionized (DI) water at various concentrations to obtain the DS. The FO experiments were conducted using commercially available cellulose triacetate (CTA) flat sheet membrane. The cytotoxicity study by the MTT assay method proved nontoxic nature of IBMA-Na and thermogravimetric (TGA) analysis of IBMA-Na showed two glass transition temperature (Tg) values well above the operation temperatures of FO-MD hybrid process. High osmotic pressure (Π) values with low viscosity were obtained for IBMA-Na with a concentration up to 0.375 g/mL, and Π values increased drastically thereafter. The DS consisting of 0.375 g/mL of IBMA-Na showed the flux of 34 L/m2 h at active layer facing DS (AL-DS) mode with a RSF of 0.196 gMH at 60 °C. The recycling of the DS was easily achieved using the membrane distillation process and revealed its potential application in the FO-MD hybrid desalination process.

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