Rapid and efficient chromium (VI) removal from aqueous solutions using nickel hydroxide nanoplates (nNiHs)

Abstract

Chromium (VI) water contamination still represents a great risk to human health. Consequently, the need for unconventional adsorbents with remarkable sorption abilities is dramatically increasing. Hence, in this study, nickel hydroxide nanoplates (nNiHs) were developed to achieve rapid and significant Cr(VI) removal from aqueous solutions. nNiHs showed an average particle size and crystallite size of 36.8 nm and 8.68 nm, respectively. Different reaction parameters were investigated, including nNiHs dosage, pH, reaction temperature, initial Cr(VI) concentration, and co-existing anions. nNiHs could efficiently remove 20 mg/L Cr(VI) concentration over a wide pH and temperature range(s) (5.0–9.0) and (25–75 °C), respectively. Pseudo 2nd order kinetic model and Freundlich isotherm model were the best to fit experimental data. A maximum Cr(VI) sorption capacity of 71.25 mg/g was achieved at the optimal reaction conditions (pH 5.0, temperature 25 °C, and dosage 2 g/L), comparable to the previously reported values. The governing Cr(VI) removal mechanism by nNiHs involved the high dominance of electrostatic adsorption and the low dominance of co-precipitation. The high sorption potential of the nNiHs and the high affinity of the aqueous Cr(VI) species, enabled the proposed adsorbent to yield an efficient performance in binary environmental systems.