Determination of Lignin and Tannin in Aqueous Solutions by a Modified Method

摘要

Industrial effluents containing lignin and tannin from pulp mills, tanneries, and glue factories can be effectively treated by a chemical coagulation/precipitation process with calcium hydroxide. However, residual concentrations cannot be accurately determined by the existing Standard Method by APHA-AWWA-WPCF due to interferences of calcium ions and others. This report proposes a modified analytical procedure for eliminating the interferences caused by calcium, ferrous iron, and sulfite ions in lignin and tannin determinations. The procedure is based on the reduction of tungstophosphoric and molybdophosphoric acids by tannins and lignins to produce a blue color suitable for the estimation of concentrations up to at least 10 mg/l for tannic acid as well as lignin.