Preparation of green biosorbent using rice hull to preconcentrate, remove and recover heavy metal and other metal elements from water

Sodium hydroxide treated rice hulls were investigated to preconcentrate, remove, and recover metal ions including Be2+, Al3+, Cr3+, Co2+, Ni2+, Cu2+, Zn2+, Sr2+, Ag+, Cd2+, Ba2+, and Pb2+ in both batch mode and column mode. Sodium hydroxide treatment significantly improved the removal efficiency for all metal ions of interest compared to the untreated rice hull. The removal kinetics were extremely fast for Co, Ni, Cu, Zn, Sr, Cd, and Ba, which made the treated rice hull a promising economic green adsorbent to preconcentrate, remove, and recover low-level metal ions in column mode at relatively high throughput. The principal removal mechanism is believed to be the electrostatic attraction between the negatively charged rice hulls and the positively charged metal ions. pH had a drastic impact on the removal for different metal ions and a pH of 5 worked best for most of the metal ions of interest. Processed rice hulls provide an economic alternative to costly resins that are currently commercially available products designed for metal ion preconcentration for trace metal analysis, and more importantly, for toxic heavy metal removal and recovery from the environment. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Sodium hydroxide-treated rice hulls showed significantly improved removal efficiency for metal ions such as Co, Ni, Cu, Zn, Sr, Cd, and Ba, with a fast removal kinetics. The principal removal mechanism is believed to be the electrostatic attraction between the negatively charged rice hulls and the positively charged metal ions, with a pH of 5 working best for most metal ions. Processed rice hulls provide an economic alternative for metal ion preconcentration and toxic heavy metal removal.