Developing sustainable draw solute for forward osmosis process using poly(amidoamine) dendrimer coated magnetic nanoparticles

Forward osmosis is the least energy intensive water treatment membrane process, however, designing a sustainable draw solute is still a critical research necessity. In this work, we developed Poly(amidoamine) dendrimer coated magnetic nanoparticles (PAMAM-MNPs) to be used as a draw solute in the forward osmosis process. Poly(amidoamine) dendrimer was selected due to its highly branched tree-like structure, diverse types of terminal groups, and ability to induce high osmotic pressure. The synthesized MNPs had a crystalline structure of a single-phase magnetite, spherical shape with an average size of 11.8 nm for bare MNPs, and 17.1 nm for PAMAM-MNPs. The performance of the synthesized MNPs as draw solute was tested using a bench scale forward osmosis setup. The average water flux obtained was 12.9 LMH during the first running cycle and decreased with time due to the dilution of draw solution. The MNPs were easily recovered using a permanent magnet and reused as draw solute for multiple cycles. The average water decreased by almost 25 % after four running cycles due to membrane fouling. This study highlighted the performance and limitations of using a newly developed dendrimer coated MNPs draw solute in the forward osmosis process.