Study On Extraction Of Volatile Fatty Acids From Anaerobicly Acidified Broth Of Organic Wastes

Recycling organic acid by anaerobic fermentation of organic waste is an important aspect with value-added products and higher technological content using of biological technology. The composition of organic waste is complex and unstable, and the resulting instability of many metabolic pathways and the fermentation products. Mixed culture caused a lot of organic acids and its concerntration was very low. Therefore, the separation of mixed organic acids has been of important and difficult through anaerobic fermentation of organic waste.This paper investigated the optimum conditions of two-step evaporation method and extraction of mixed organic solvent based on chemical complexation. Taking into account the problems of complex extraction, to further explore the best conditions of recovery of mixed organic acid and extractant through the direct use of tributyl phosphate (TBP) and back extraction of mixed organic acids from TBP by vacuum evaporation.The main conclusions are as follows:(1) Mixing organic acid recovery by two-step evaporation method, prior to joining 10 g/L Ca (OH)2, adjust the broth pH=1, recovery rate of acetic acid was 49.5%, recovery rate of mixed organic acid can reach 37.94%.(2) By choosing 30% tri-octylamine(TOA)+30%n-octanol+40% sulfonated kerosene(v/v) as extractant, after 4 times the cross-flow extractions, recovery rate for the simulation of the fermentation was 99%, for the actual fermentation broth 80%.The use of 0.148 mol/L NaOH stripping, t'=80℃, the stripping rate was 80%,recovery rate of mixed organic acid was 80%; Extraction ability of extractants recovered slightly decrease, but does not affect the extraction efficiency.(3) Directly with TBP to complex extraction, the concentration of TBP was 3.63 mol/L, the concentration of mixed organic acid was 20 g/L, equilibrium time 5 min, room temperature, the ratio of water phase and oil phase was 1:1, after 3 times extraction, the extraction efficiency can reach 98.47%; Effect of mixed organic acid extraction affected by the concentration of NaCI, the more NaCI concentration, the more conducive to extraction.(4)Based on "temperature swing effect", stripping the organic phase enriched mixture of organic acids,by comparing the stripping with hot water and vacuum evaporation method, found that the effect of vacuum evaporation was better;In the vacuum of 0.095 Mpa,70 rpm, the evaporation temperature was 100℃, the ratio of water phase and oil phase was 1:1, the evaporation time was 30 min, after three stripping, the mixed organic acids of E'up to 94.74%, C'up to 4.88 g/L, in which E'of acetic acid was 99.74%, E'of propionic acid was 91.42% and E'of butyrate acid was 66.63%, E'of valeric acid was 40.52%; Mixed organic acid and acetic acid recovery was 93.29%,98.21% respectively.(5)TBP recovered can be reused, so can greatly reduce the cost of extraction.