NANOFILTRATION PROCESS FOR IMPURITY REMOVAL

摘要

Nanofiltration membranes have been identified that can unexpectedly provide for competitive removal of silica and sulfate from brine in alkaline conditions. Such membranes are known as monolithic nanofiltration membranes and are particularly suitable for removing silica and sulfate impurities from a brine stream in a brine electrolysis plant.

主权项

1. A method for removing silica and sulfate impurities from a brine stream using a nanofiltration system, the brine stream comprising an aqueous solution of NaCl, silica impurity, and sulfate impurity, the method comprising:
employing a monolithic nanofiltration membrane in the nanofiltration system, wherein:
the monolithic nanofiltration membrane comprises a polymeric semipermeable membrane and a nanofiltration layer;the polymeric semipermeable membrane comprises a non-cross-linked base polymer and a cross-linked skin on a surface of the base polymer; andthe nanofiltration layer is covalently bonded to the cross-linked skin in the polymeric semipermeable membrane; adjusting the pH of the brine stream to be greater than 9; and subjecting the brine stream to the nanofiltration system.