Alteration of bentonite from Ughelli by nitric acid activation: Kinetics and physicochemical properties

Abstract

The physicochemical properties of Ughelli bentonite was modified by nitric acid activation to improve its performance. The bentonite mineral was reacted with different concentrations of nitric acid ranging from 2 to 16 mol.L-1. The reactions were performed at different times and temperatures to study the process kinetics. The chemical composition and physical characteristics of the natural and treated samples were analyzed. To investigate the adsorptive performance of the modified samples, they were used to bleach soya bean oil. The surface area and adsorption capacity increased from 117.6 m2.g-1 to 364 m2.g-1 and 29 to 95 %, respectively, after activating with 14 mol.L-1 of HNO3. Kinetics studies showed that the activation process were controlled by the chemical reaction step and can be given by: 1 - (1 - X)1/3 = k t; where X is the fraction of the cations removed at time t. This study has proved that bentonite from Ughelli can be modified by nitric acid activation to increase its performance as adsorbent in the vegetable oil purification industry.