Method for improving decoloring efficiency of gallic acid

The invention discloses a method for improving the decoloring efficiency of gallic acid. In order to overcome the defects that an existing decoloring method is large in quantity of activated carbon, poor in decoloring and the like, the pH value of nutgall hydrolysate is improved to 3-4, and 1.5 kg of EDTA-2Na is added to per 250 kg of the nutgall hydrolysate; pure water is added to the obtained coarse gallic acid product, and the weight of the pure water is 8 times that of the coarse gallic acid product; then 5% of activated carbon used for secondary decoloring of the last batch is added, and primarily decolored filtrate is obtained; and 3-5% of new activated carbon is added in the obtained primarily decolored filtrate, decoloring, filtering, crystallization and dewatering are carried out, and the finished gallic acid product is obtained. The method is used for production of gallic acid, and can remarkably reduce the quantity of activated carbon in the production of gallic acid, reduce the decoloring cost by