Abstract:
Soil containing high contents of arsenate can be harmful to human from theirs contribute into the food chain. This research studied arsenate contaminated soil treatment based on 4 types of washing agent (pH 11) including distilled water, ferric chloride, rhamnolipids and rhamnolipids with ferric chloride. Two types of soil were used as simulated soil including kaolinite and silica sand. The soils were defined not contain organic and both of its had negative charges on its soil surface. Arsenate and rhamnolipids adsorption on kaolinite were fitted to Freundlich isotherm and pseudo-second order kinetic. In the case of silica sand, Arsenate and rhamnolipids adsorption were fitted to Freundlich isotherm, Langmuir isotherm and pseudo-second order kinetic, respectively. For observed an amount of arsenate contamination, kaolinite and silica sand adsorbed arsenate 80.10 mg.As/kg.soil and 29.16 mg.As/kg.soil, respectively. Regarding kaolinite, the best condition was observed when using rhamnolipids, followed by ferric chloride, distilled water and rhamnolipids with ferric chloride with removal efficiency of 63.36% at 20 hrs washing time, 59.72% at 20 hrs washing time, 54.47% at 24 hrs washing time and 32.56% at 16 hrs washing time. In the case of silica sand, the best washing agent was ferric chloride, followed by rhamnolipids, rhamnolipids with ferric chloride and distilled water, with removal efficiency of 96.63% at 4 hrs washing time, 86.14% at 4 hrs washing time, 75.18% at 8 hrs washing time and 29.54% at 24 hrs washing time. The treatment of arsenate contaminated soil by rhamnolipids and ferric chloride separately was proven to be efficient. In addition, even using rhamnolipids and ferric chloride separately had better efficiency than its mixture but the result reveals the good prospect to apply rhamnolipid with ferric chloride for preventing arsenic re-adsorption onto the soil.