Treatment of Vegetable Tanning Spent Liquors

Briggs and coworkers (28) were able to remove about 90% of the tannin by absorption on Amberlite XAD-2 resin. The resin could be regenerated and the absorbed materials collected by washing with acetone, which could be recovered by distillation. The recovered tannin had a purity of 80% and preliminary economic feasibility analyses indicated that its recovery and reuse could result in a significant net operating profit for the treatment process. 

When a total of 10 g of tannin had been added to the 31 test vessels, the total gas production was about 1.31/day with a methane content of about 60%. At these levels of tannin addition, there was little difference between quebracho and wattle tannin treatments. The quebracho tannin was more inhibitory to the system than the wattle tannin at higher concentrations. With proper control, this approach would seem to be an effective process for reduction of both COD and color removal. 

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