a b s t r a c t
The advanced oxidation technology dominated the disposal of reverse osmosis concentrate in textile and
dyeing industry due to its extremely low biodegradability. For resource conservation and sustainable
development, the reverse osmosis concentrate was reused in dyeing procedure after being treated
properly with combining method of persulfate oxidation and lime-soda softening. Firstly, the refractory
organics was oxidized by persulfate thermal activation and the results indicated that the most efficient
and economical reaction happened with initial pH ¼ 5.0, 1000 mg/L initial persulfate concentration and
75 C. In this process, chemical oxygen demand degradation fitted the pseudo-first-order model well and
the sodium sulfate concentration increased from 9600 to about 10,350 mg/L. Then, the hardness of
reverse osmosis concentrate including Ca2þ and Mg2þ hardness was softened efficiently by lime-soda
softening technology and appropriate lime and soda concentration was determined to be 150 mg/L
and 800 mg/L, respectively. Finally, the effluent was employed as the dyeing water to test the reuse
feasibility in dyeing of reactive dyes. Color strength, color difference and color fastness were all used to
evaluate the dyeing performance and dyeing results showed that the effluent which was treated properly
(COD 21.5 mg/L, total hardness 17.0 mg/L) was available for reuse in reactive dyes dyeing procedure.
The study provided a novel method to treat and reuse reverse osmosis concentrate and more importantly,
it promoted sodium