Bifunctional hybrid magnetic colloidal clusters for efficient oil sludge recovery

Abstract

Oil contamination of water bodies due to oil spills, industrial waste discharge, oil leaks, etc. poses a major threat to the quality of groundwater, soil, and living organisms. To combat this issue through effective environmental remediation, efficient and cost-effective materials and innovative strategies are required. Here, we report a novel bifunctional magnetic material for efficient oil sludge removal using superparamagnetic colloidal nanocrystal clusters(BSPM-CNC) of nickel ion doped iron oxide with a shell of nitrogen-activated carboxymethyl cellulose char. The BSPM-CNC is synthesized by using a single-step procedure using water as a solvent. The crystallite and cluster size were tuned by varying Ni2+ ion concentration, carboxymethyl cellulose, and urea ratio. The cluster size was found to increase, when the carboxymethyl cellulose and urea ratio was reduced, due to insufficient stabilization of the capping agent that allowed the formation of secondary structures. X-ray photoelectron spectroscopy results confirmed the presence of nitrogen in the shell because of the condensation of OH and carbonyl groups of CMC with amine groups of urea, sp2-type carbon, C-O/N and O-CO bonding states. Laser Raman spectra of the char showed two major bands G and D bands, originating from the sp2 bonds and sp2 microdomains of the bond angle disorder caused by the sp3 hybridizations, respectively. The BSPM-CNC was found to be very efficient for oil sludge removal, where an oil removal efficiency of ∼ 98% was achieved with a cluster loading of 16 mg/L. The mechanism of sorption of oil are π-π interaction between aromatic hydrocarbons and graphitic domains of BSPM-CNC, Lewis-acid base interaction between nitrogenous char and delocalized electron cloud, and absorption into the pores of clusters. Our new approach provides a new platform to produce magnetic nanoclusters for the efficient removal of oil pollutants.