APPLICATION OF NANOFILTRATION TECHNOLOGY TO IMPROVE SEA WATER NEUTRALIZATION OF BAYER PROCESS RESIDUE

摘要

Sea water neutralization of alkaline Bayer process solid waste residue is a sustainable solution to turn a hazardous waste material into a benign, non-hazardous material that can be re-used in some applications. The concentrations of the active neutralizing agents in sea water, calcium and magnesium, are low and large volumes of sea water are required to neutralize the alkaline residue. Nanofiltration of sea water can produce a concentrate containing up to four times the calcium and magnesium levels in sea water, while the mono-valent ions, like sodium and chloride, are only marginally concentrated. This significantly reduces the volume of sea water required for the neutralization process and hence the size of neutralization equipment. Other advantages include improved reaction kinetics and reduced salinity of the neutralized residue, making it more suitable for certain applications. The nanofiltration permeate, with lower scaling potential, is also an improved feed for sea water reverse osmosis plants to produce potable water.