Study on the pretreatment of black liquor produced from refined cotton production by acidification

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 5400 mg &middot L-1 to 3180 mg &middot 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.EI0SUPPL. 1208-212+2274