Novel synthesis of ultrafiltration membranes by crosslinking metal (II)-Alginate hydrogels with hexamethylene 1,6 -Diisocyanate in inert solvent: Application for remediation of wastewater by removal of toxic pollutants

Abstract

Hexamethylene 1,6- diisocyanate (HDI) crosslinking agent has been used for novel synthesis of ultrafiltration (UF) membranes from polysaccharide derivatives as natural polymers for the first time. This process takes place by crosslinking the soft membranes of Cu (II)-alginate hydrogels (Cu-Alg2)n with 9 % of (HDI) in dryness acetone (DA) for obtaining its corresponding (CCu-Alg2)n as UF membranes. These new crosslinking membranes can be used for uptaking the toxic metal ion contaminants from wastewater in purification of drinking water. The pore size in such membranes can be controlled by varying the pH of the alginate sol using either NaH2PO4 or Na2HPO4 simple salts. The formed crosslinking membranes (CCu-Alg2)n were characterized by the elemental, FTIR and SEM/EDAX analyses. The experimental results of the crosslinking membranes (CCu-Alg2)n in its hydrogen form (CH2-Alg2)n showed high affinity for removal of some divalent metal ions such as Cu2+, Ni2+, Co2+, Cd2+ and Pb2+ ion pollutants at the pH s 2–6. Also, they revealed high selective separation of some tested metal ions such as Ag+ and Cu2+ from electrolyte mixtures involving these metal ions with other divalent metal ions (0.1–0.5 mmole /L) at 25 °C. Again, such crosslinking membranes of (CCu-Alg2)n has proven high capability for isolation the Serratia marcescens Grahams-negative fine bacterium from contaminated media. The nature of geometrical configuration for chelation of Cu (II) ions with the alginate functional groups (–COO– and –OH) in its non-crosslinked (Cu-Alg2)n and crosslinked with HDI membranes (CCu-Alg2)n were suggested and discussed.