Recovery of water from saturated solutions by membrane processes

Abstract

Recovery of water from spent aqueous streams is well known through the use of reverse osmosis (RO) but the extent of recovery is limited primarily by the scaling potential of dissolved species and the osmotic pressure of the concentrate stream. Mining industries, particularly the ones which use sulphuric acid leaching, discharge large quantities of effluents containing dissolved solutes with significant amounts of calcium and sulphate. Chemical method for the removal of sulphate is economically prohibitive to meet the discharge norm. The effluents therefore are often diluted and discharged or sent to dry areas for solar evaporation. Application of RO for the recovery of water is restricted by the scaling of sparingly soluble calcium sulphate. The use of commercial antiscalants does not help as they do not reduce the quantity of sulphates in the discharge stream. Experiments were carried out using nanofiltration (NF) membrane process with commercially available membrane element primarily to remove sulphate...