Removal of mercury ion from wastewater using natural zeolite: effect of humic acid to adsorption isotherm

Abstract

Abstract As Indonesia possessed a considerable amount of gold deposit, many golds mining activities, including the small-scale one, is commonly found. A simple mining technique (amalgamation) that utilizes mercury (Hg) will generate mercury-containing wastewater. One of the prospective Hg removal methods from wastewater is adsorption. In addition, it is also possible that metal contained in the wastewater interacts with other substances, such as humic acid. This experiment was aimed to examine the adsorption process of Hg2+ ions in the wastewater using natural zeolite. The effect of the presence of humic acid, which might be found in sewage, toward the adsorption capacity of Hg2+ onto natural zeolite was investigated. The natural zeolite, which contained several types of minerals, was obtained from Klaten, Central Java. The experiment was conducted using ten mg/L HgCl2 as the initial concentration and ten mg/L humic acids. A comprehensive study that includes isotherm and the kinetic study was carried out. Experimental results showed that the presence of humic acid was found to reduce the capacity of Hg2+ adsorption on natural zeolite. Freundlich isotherm model was found to be more suitable to represent equilibrium adsorption data. Kinetic examination revealed that the pseudo-second-order model was able to produce a better agreement with experimental data.