Effects of carboxymethyl cellulose grafting on stability and reactivity of zerovalent iron in water systems

Abstract

The present study investigated the effects of degree of substitution (DS) and grafting method (pre-grafting or post-grafting) of carboxymethyl cellulose (CMC) on particle size, surface chemistry, colloidal and oxidative stability and reactivity of zerovalent iron (ZVI) particles. CMC with different DS were systematically synthesized by etherification of cellulose using monochloroacetic acid (MCA) in alcoholic medium. Structural Identity and purity of CMC was confirmed using NMR, FTIR and XRD analyses. It was found that DS of CMC can regulate the particle size, stability, dispersibility and reactivity of stabilized ZVI particles. CMC stabilized ZVI particles had smaller particle size, higher surface area and high dispersibility as compared to bare ZVI particles. Further, less aggregation was observed in higher DS CMC stabilized ZVI samples compared to lower DS CMC stabilized ZVI samples due to the better shielding ability for van der waals attractive forces. Also, the reactivity of stabilized ZVI particles was better than bare ZVI particles as the complete degradation of naphthenic acid was achieved in 180 min (>95% in 60 min). The colloidal stability and reactivity of stabilized ZVI particles remained intact even after 6 months of storage. Overall, CMC was found most efficient in colloidal stabilization of ZVI particles both in pre-grafting as well as post-grafting mode.