Acid-reinforced ionic cross-linking of sodium alginate/polyamidoamine dendrimer blended composite membranes for isopropanol dehydration through pervaporation

Extreme swelling of hydrophilic polymer such as sodium alginate in aqueous liquid mixture separation processes has always been a problem that needs to be resolved. Herein, the ionic interactions between polyamidoamine (PAMAM) dendrimers and sodium alginate (SA) were improved by using simple aqueous acidic solution after obtaining the dense composite membranes. The zero generation PAMAM dendrimer (G(0)) used has four terminal primary amine reactive groups (P4). The acid-reinforced ionic cross-linked (ARIC) membranes gave an impressive water stability even at high water content in feed of 90 wt% during the separation process. The composite membranes were characterized accordingly for their chemical and physical properties. Also, the efficiency of the ARIC process was evaluated by separating alcohol/water mixtures through pervaporation at varying feed concentration and temperature. Impressively, the membranes treated with sulfuric acid resulted to a smaller free volume size compared to hydrochloric acid revealed by positron annihilation spectroscopy (PAS). This means that a lower swelling degree for the sulfuric acid-treated membranes giving better separation efficiency even at high water feed composition. The best pervaporation separation performance was observed in separating 70/30 wt% isopropanol/H2O aqueous solution at 55 C. It has a permeation flux of 6.59 kg m(-2) h(-1) and a 99.97 wt% water content in permeate. The membrane, SA-P4-H2SO4/PVDF also exhibited good stability for 552 h maintaining a water concentration in permeate above 97 wt%.

Automated summary

The ionic interactions between PAMAM dendrimers and sodium alginate were improved by using an acidic solution, resulting in better separation efficiency and water stability in liquid mixture separation processes.