Abstract: In order to realize the recovery of NaCl in high-salt wastewater, a nanofiltration-reverse osmosis double-membrane cascade combined process was used to purify the mixed simulated wastewater contained NaCl and Na₂SO₄. The concentration ratio, operating pressure, flow rate and temperature were investigated, and the most excellent technical conditions were determined. The experimental results showed that the value of [NaCl]/[Na₂SO₄] was not less than 41.45 in reverse osmosis concentrate, which indicated that the process can achieve separation of NaCl and Na₂SO₄ effectively; In addition, the reverse osmosis membrane can separate Cl^－ with the rejection rate of Cl^－ more than 96%, and the purity of the recovered NaCl can reach over 97.5%.

Key words: high-salt wastewater, nanofiltration technology, reverse osmoses