Removal of zinc oxide nanoparticles in aqueous environment using functionalized sorbents derived from sago waste

The increase in sago processing industries especially in Malaysia has inadvertently created its waste effect on the environment. The study therefore modified the raw sago waste residue (hampas) generated by three (3) chemical processes; esterification, acetylation and phosphorylation. The as-prepared sorbents were characterized by surface area analyser (BET), Fourier transform infrared (FTIR) spectroscopy, field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). Thereafter, their sorption efficiencies were evaluated on zinc oxide nanoparticles in lake water in a laboratory-scaled column-bed sorption study. Spectra analysis confirmed the presence of ester and ether functionality in the esterified and acetylated samples, whereas phosphoric ester and amine functionality were present in the phosphorylated sample. The acetylated sample recorded the largest surface area (29.02 m(2)/g) and degree of substitution (1.99). The experimental data established that acetylated sago residue recorded the maximum column capacity of 4.50 mg/g in all the parameters examined. Meanwhile, increase in influent concentration (1.51-5.04 mg/L) and flow rate (4.20-6.60 ml/min) decreased the breakthrough time while increase in column-bed height (3-7 cm) increased the breakthrough time for the three sorbents. However, Adams-Bohart model adequately described the behaviour of the sorption process better than Thomas and Yoon-Nelson models. The results suggested that acetylated sago residue is potentially scalable for removing zinc oxide nanoparticles from water.