Synthesis of sodium alginate grafted and silver nanoparticles filled anionic copolymer polyelectrolytes for adsorption and photocatalytic degradation of a cationic dye from water.

Sodium alginate (SA) was grafted to poly (acrylonitrile-co‑sodium acrylate-co-acrylic acid). The grafted copolymer was crosslinked with N. N, methylene bis acrylamide (MBA). Silver nanoparticles (AgNPs) were generated in situ within the growing polymer network by reducing 0.1 mM silver nitrate with 0.05 mM ascorbic acid (ASA). The effect of initiator concentration, total monomer concentration, SA weight%, MBA weight% and acrylonitrile (AN):sodium acrylate (NaAA)/ acrylic acid (AA) molar ratios on the grafting were studied. The nanocomposite was characterized and used for adsorption of methylene blue (MB) dye from water. The composite was also used for photocatalytic degradation of the dye in the presence of sun light. The Box-Behnken design (BBD) of response surface methodology (RSM) with different compositions resulted in an optimized composition of 5:1 M ratio of AN:NaAA/AA, 1 wt% MBA and 2 wt% SA. The nanocomposite (SACP5Ag) prepared with the optimized composition showed an equilibrium batch adsorption(q, mg/g)/removal(R)% of 245/98 from 50 mg/L MB dye in water and a q /R% of 18.87/31.4 in a fixed bed adsorption at a feed inlet concentration(mgL)/inflow rate (mLmin)/bed height (mm) of 100/20/25. The composite showed a photocatalytic degradation efficiency of 98 % in sunlight for 80 min and a 1st order rate constant of 0.02 min.