Industrial scale extraction and stripping devices for continuous recovery of gallic acid from Chinese nutgall processing wastewater

Abstract

In this study, we report the industrial application of an efficient technology for the recovery of gallic acid from Chinese nutgall processing wastewater. The recovery of gallic acid by industrial scale extraction and stripping devices was performed, with tributyl phosphate as the extractant and kerosene as the diluent. The results showed that the theoretical extraction stage was four, while the theoretical stripping stage was two. A closed-cycle system was studied for the continuous countercurrent extraction and stripping, with a five-stage extraction device and a three-stage reflux stripping device. The results showed that the multistage extraction-stripping system could steadily run for a long period, the average gallic acid level in the raffinate was 0.85 g·L−1, and the gallic acid content recovered in the strip liquor was higher than 120 g·L−1. The average extraction yield of gallic acid was 94.14%. When the strip liquor was used as raw material for production, the average production yield increased by 8.64%. In addition, after extraction, the CODCr in the wastewater decreased by 38.19%, and the biodegradability of wastewater improved by 1.6 times. This study provided a new impetus for the sustainable development of the Chinese nutgall processing industry. Keywords: Extraction, Gallic acid, Recovery, Stripping, Wastewater