Diatomite quality improvement by calcination for removal of arsenic from contaminated water

Abstract

The purpose of this research was to investigate the possibility of treated diatomite to be used as an adsorbent for As (III) and As (V) removal. In the preparation of treated diatomite adsorbent, two factors of temperature and time for calcination were studied in the batch experiments. The aims of batch experiments were to study the optimum of temperature and time for preparing treated diatomite, concentrations of As (III) and As (V), pH, contact time, amount of treated diatomite and the competing anions. The adsorption equilibrium was studied by the Freundlich and Langmuir isotherm euations. The optimum conditions of treated diatomite and the efficiency of arsenic removal from arsenic contaminated surface water were studied. The experimental results showed two appropriate adsorbents for removal As (III) and As (v) under the condition of calcinations at 400ํC for 6 hours (CD4006) and at 800ํC for 6 hours (CD8006). It was found that the efficiency of CD4006 and CD8006 adsorbents for removal As (III) and As (V) depended on pH, contact time and amount of treated diatomite. The optimum conditions for As (III) and As (V) removal were as follows: 10 mg/l of As (III) and As (V) concentrations at pH 5 for 5 hours with shaking rate of 180 rpm and the 3.0 g of CD4006 and CD8006 adsorbents. The efficiency of AS (III) and As (V) removal were 98.72% and 99.05%, respectively. The adsorption isotherm for As (III) and As(V) removal was complied with the Fruendlich isothem. The maximum capacities of adsorbents were 1.77 mg AS (III)/g CD4006 and 0.55 mg As (V) / g CD8006. For the results of the competing anions, the removal of As (III) and As (V) was affected by phosphate anion. Using 0.1 g of CD4006 and CD8006 adsorbents for removal arsenic from arsenic contaminated surface water at the concentration of 1.95 mg/l, the arsenic was reduced to < 0.05 mg/l. Therefore, the water quality could meet the discharge standard of Bottled Drinking Water Quality Standards (WHO As maximum allowable 0.01 mg/l).