Fluoride and Chromium Removal from Contaminated Water Using Activatd Alum Based Water Treatment Sludge as an Adsorbent

Abstract

Chromium and Fluorine are among the prioritized contaminants of water which are causes for disease if taken above recommended levels. Hence their removal by implementing a cost effective, locally accessible, not time consuming and environmentally friendly technology has been widely studied by many scholars The objective of this study was to use Activated Alum sludge from the water treatment plant as an adsorbent for the removal of chromium from chromium contaminated tannery wastewater and Fluoride from Fluoride riche well water at optimized value of pH, contact time, adsorbent dose and initial concentration. To improve the adsorption ability, the original alum water treated sludge; the sample was treated thermal at different temperature, digested with hydrochloric acid alone and/or acid digestion followed by thermal treatment. Hydrochloric acid treatment improved the adsorption efficiency of the sludge on the fluoride and Chromium in water significantly, with maximum adsorption efficiency of 92% and 83.802%, respectively. The effects of experimental parameters such as, pH of initial concentration of Chromium and Fluoride solutions, contact time, dosage of adsorbent and initial concentration of chromium and fluoride in the solutions were thoroughly investigated. Those showed that 95.5% removal efficiency observed at pH 2, 1.5h contact time and 20g/L of adsorbent dose for fluoride removal. Highest removal efficiency of chromium, 91.04% were observed at pH 4, 2.5h contact time and 20g/L of adsorbent dose. With this optimum condition kinetics and isotherm of the adsorption process were analyzed using different models. The result revealed that kinetics of the process fitted well the pseudo-second order kinetic model and from the tested isotherm models the Feundlich model was found to be the best fit. Moreover, SEM images and XRD patterns of the adsorbent were recorded to get a better insight into the adsorption process. In general activation of Alum based water treatment sludge improved its potential to be used as an alternative low cost adsorbent for the removal of chromium and Fluoride from contaminated water.