A study on hydrothermal disposal of sodium arsenate waste from Ga-As processing

Hydrothermal disposal of sodium arsenate waste was investigated with the ai m of removing As from solution, and its precipitation as crystalline iron a rsenate. The precipitate was characterized by XRD and SEM, and leach tests were conducted to examine the precipitates solubility. The optimum formatio n condition for crystalline iron arsenate was pH 0.3-1.7, temperature 150-2 00 degrees C, Fe/As 1.0 and time 10-40 min. Over 98% arsenic in the waste c an be precipitated. The solid product is mainly iron arsenate which has a s olubility below 5 mg/l. The preliminary work showed that hydrothermal dispo sal is a feasible option for treatment of sodium arsenate waste. (C) 1999 K luwer Academic Publishers.