Recovery of Valuable Solvents from the Pharmaceutical industry Wastewater

Abstract

The circular economy focuses on making the highest use of any molecule before being discarded. Compounds diluted in waste aqueous streams are usually eliminated instead of being recovered. When the separation process is not efficient enough, the energy consumed does not compensate the material recovered. The wastewater stream with diluted isopropanol and ethyl acetate from the pharmaceutical industry is an example of this situation, e.g., from the production of the antibiotic called ampicillin sodium. Pollution caused during ampicillin sodium production is due to the wastewater generated containing Ethyl Acetate (ETAC) and Isopropyl Alcohol (IPOH). In the literature, novel chemical processes have been proposed to recover these valuable compounds but require a third compound used as an extractive agent. Any third compound added to the mixture remains there and its presence in traces is unavoidable. The impurification of these solvents is a major issue for the pharmaceutical industry. In this study, a novel process is proposed that avoids the addition of an extractive agent. This type of wastewater has only 3 % of solvents and the ratio of isopropanol versus ethyl acetate in the feed is 5:1. Volatile solvents would be easily recovered from an ideal mixture; at least to reach a wastewater with 1 % solvents content. Unfortunately, there are four azeotropes present in the system studied and the separation is not straightforward. However, taking advantage of water / ethyl acetate immiscibility region and properly recycling and mixing process streams, then the mixture separation is possible employing only three distillation columns and a decanter. The process has been rigorously simulated and its feasibility proven. The environmental impact of the various alternatives proposed has been assessed using Waste Reduction Algorithm Software V.1.0 (WAR). Ethyl acetate and isopropanol can be separated from water without extracting agents, possibility proven using residue curve maps. The study shows that diluted wastewater streams are a suitable source of chemicals.