Development of a process for n-butanol recovery from ABE wastewater streams by membrane technology

The aceton-butyl-ethanolic fermentation process (ABE) is a biotechnological process that leads to the production of acetone, n-butanol and ethanol (ABE compounds) from glucose sources and amides by use of certain biomasses. The process was developed initially during the middle of the last century and suffers from decline due to the greater petrochemical production of products and the lowering of the costs of the sector. Nowadays, the ABE process is regaining great interest because the fraction with the highest concentration, i.e. n-butanol, is an excellent constituent for biofuels. The ABE process has been optimized over time to obtain maximum yields of n-butanol, but the problem of separating and concentrating the butanol in the outlet stream of the ABE process persists. To allow an adequate use, often distillation by use of more columns is required. Moreover, the contained biomasses and suspended solids, in high quantity, must be eliminated, leading to overall high treatment costs. This work will report the main idea and some preliminary experimental results for the development and application of a process based on membrane technologies, to separate and concentrate the butanol from ABE process streams to sensibly reduce the difficulty to perform a final distillation. The proposed treatment process is composed by ultrafiltration, pervaporation, nanofiltration and a final mixing/demixing operation. Attention was paid to the productivity, selectivity and longevity of the used membranes. The optimization of these three parameters is essential to achieve a level of reliability and feasibility of the proposed process, in particular the avoidance of membrane fouling.