Abstract:

A large number of neutral wastewater will be produced in the process of chlorinated titanium dioxide by inorganic coating treatment technology,which contains a small amount of titanium dioxide and water-soluble salts.At present,the titanium dioxide and water-soluble salts are discharged outside by most of the enterprises.The membrane integration（ceramic membrane+reverse osmosis membrane+nanofiltration membrane) treatment process was used to study the chlorination titanium dioxide post-treatment wastewater.TiO₂ was separated and recovered by ceramic membrane filtration;the clear liquid of ceramic membrane was concentrated by reverse osmosis membrane and the clean water was recycled;the concentrated liquid of reverse osmosis was separated by nanofiltration membrane to separate sodium sulfate and sodium chloride.The results showed that the average flux of ceramic membrane was 650 L/（m ²·h）,the mass concentration of titanium dioxide in the concentrate was 90 g/L,and mass concentration of titanium dioxide in permeate was less than 0.001 g/L.With the filtration of reverse osmosis membrane,retention rate of sodium sulfate and sodium chloride could reached above 99.5% and the mass fraction of salt in concentrated water was above 4%.Sodium sulfate and sodium chloride in concentrated water were separated by nanofiltration membrane.With the filtration of nanofiltration membrane,retention rate of sodium sulfate could reached 97%.Sodium sulfate concentration can reach more than 14%.

Key words: chlorination of titanium dioxide, post-treatment wastewater, ceramic membrane, reverse osmosis membrane, nanofiltration membrane