Determination of lignin concentration in bleaching effluent via Coomassie brilliant blue G-250 method

Abstract

Kraft pulp and alkali peroxide mechanical pulp were prepared with aspen and wheat straw and bleached with chlorine dioxide, an alkali extraction strengthened by hydrogen peroxide, hydrogen peroxide, or peroxyacetic acid. Eight different bleaching effluents were obtained, and a Coomassie brilliant blue G-250 method was applied to determine the lignin content in each of the bleaching effluents. The visible light spectra indicated that the alkali-soluble lignin and the alkali bleaching effluent could increase the absorbance of Coomassie brilliant blue G-250 at 640 nm, but the acidic soluble lignin and the acidic bleaching effluent did not increase absorbance. Thus, the Coomassie brilliant blue G-250 method applied to alkali bleaching effluents but did not apply to acidic bleaching effluents. An analysis of the pH, particle size, zeta potential, and visible light spectra determination showed the Coomassie brilliant blue G-250 absorbed on lignin particles, which caused the absorbance increase at 640 nm. With the actual measured value of the lignin content obtained via the Klason lignin method, the relative error of the results obtained via the Coomassie brilliant blue G-250 method was less than or equal to 3.8%.