Modified tapioca starch for iron nanoparticle dispersion in aqueous media: potential uses for environmental remediation

Abstract

Synthesis of cost-effective surface-modified nanoscale zero-valent iron (NZVI) for use in environmental remediation is a challenge. Herein, we report the synthesis of modified tapioca starch-coated NZVI (CNZVI) particles and their application for effective aqueous nitrate remediation. We used 2-octen-1-ylsuccinic anhydride (OSA) to modify the native starch and, thus introduced carboxyl and ester groups for effective binding of the starch to the NZVI surface. Coating NZVI (3 g L−1) with 35% OSA-modified tapioca starch (10 g L−1) significantly improved colloidal stability of CNZVI in deionized (DI) water compared to bare (unmodified) NZVI (p = 0.000). Approximately 66% of CNZVI remained suspended till 2 h as compared to 4% of bare NZVI. Nitrate removal studies (20, 40, and 60 mg $${\text{NO}}_{3}^{ - }$$ –N L−1 and 1 g L−1 of nanoparticles) showed CNZVI removed nitrate effectively (54–71% removal). The nitrate removal by CNZVI followed second-order reactions with surface normalized reaction rate constants ranging from 0.003 to 0.007 L m−2 h−1. Shelf life of the coated nanoparticles was found to be 3 months. High biochemical oxygen demand was expressed during respirometric biodegradation studies indicating ease of biodegradation of the CNZVI particles. Coating NZVI particles with OSA-modified tapioca starch is expected to have widespread scientific and industrial application potentials for ex situ as well as in situ contaminant remediation. The authors opine that the use of tapioca starch as the raw material for coated nanoparticle synthesis will be a value addition for the crop, and thus, nanotechnology will contribute to agricultural economy.