Abstract:Black liquor produced from refined cotton production is highly concentrated refractory organic wastewater containing complicated components. Pretreatment by physical-chemical processes is preferred. The pretreatment of the black liquor by acidification was studied. Reaction conditions such as pH and retention time were investigated. UV-vis scanning

GC-MS and acute toxicity test were used for analyzing the changes of the composition before and after the acidification. The results showed that the pH of 2 and the retention time of 90 mins were the best conditions. COD decreased from 5 400 mg?L^-1 to 3 180 mg?L^-1 by the ratio of 41.1%. The removal rate of chromaticity could reach 43.5%. Both species and content of organic compounds decreased to a certain extent. Organic compounds with carbon chain number of nine or more were precipitated or degraded. The dilution ratio of LIR50 (50% of luminosity inhibition rate) decreased from 250 to 140

reducing the acute toxicity by 44%. Acidification for black liquor achieved good effect

providing favorable conditions for subsequent biological treatment.