Study on the equilibrium and kinetics of nickel adsorption on rice husk: the role of activation

Abstract

Rice husk is an agricultural byproduct that is produced in huge quantities during the rice milling process. Following the trend of utilizing agricultural waste, rice husk is activated by many activators to synthesize heavy metal ion adsorbent materials. This work presents the results of the study on the adsorption of nickel ions (Ni2+) by activated rice husks. The husk was activated by three agents (NaOH, acetic acid, and H2O2), which removed 73.29 percent of the hemicellulose and 60.25 percent of the ligin (calculated by the Chesson-Datta method). The influence of time on the adsorption capacity of Ni2+ ions of activated rice husks was carried out with an initial concentration of Ni2+ ions of 160mg/L and a pH of 5.5. The concentration of adsorbent was 1,0 g.L-1. After 80 minutes of adsorption, the equilibrium adsorption capacity reached 33.33 mg.g-1. The maximum adsorption capacity calculated by the Langmuir adsorption model was 57.46 mg.g-1. Three kinetic models (Lagergren's apparent first-order kinetics, second-order apparent kinetics and Webber-Morris internal diffusion kinetics) were also studied and analyzed.