Boron Removal By Reverse Osmosis Membranes

Abstract

While most of the chemicals present in water could be effectively rejected by reverse osmosis membranes, removal of some trace elements such as boron is relatively low. The interplay between pH and ionic strength is believed to be the key to understand the boron removal. Owing to several reports of lower pKa at higher salinity to form negatively charged and larger size borate ion, one may expect to achieve better boron removal at higher salinity. At pH 9, boron removal by brackish water reverse osmosis (BWRO) membranes was found to be lower at higher salinity. However, ESPAB and SWC4+ membranes showed concave pattern removal from low to high salinity. At pH 7, trends of removal by BWRO membranes at different salinities were found to be similar to those at pH 9. However, removal by ESPAB and SWC4+ remained constant across all salinities. Removal mechanisms seemed to vary under different situations.