Electrochemical degradation of industrial alkali lignin

Abstract

At present, the wastewater, produced in pulp and paper industry, which contains lignin molecules, is still difficult to treat due to the structure complexity of lignin. In this paper, the industrial alkali lignin (AL) was treated with a Violuric acid(VA)-mediated electrochemica l degradation system, and the lignin degradation efficiency at different treatment parameters including temperature, time, VA concentration , electrolyte concentration, voltage and lignin concentration were discussed in detail. The changes of chemical oxygen demand (COD) and total carbon content (TOC) of this lignin-containing solution were also monitored. The results showed that in this electrochemically catalyzed system containing Ti/ Sn-Sb-Ir as anode, the industrial AL can be oxidized into small molecular products. The optimum conditions of electrochemic al degradation of AL are time 8 h, voltage 5.5 V, temperature 60 ˚C, alkali lignin 10 g/L, VA 2 mmol/L and Na2SO4 0.2 mol/L. At this condition, higher than 70 % AL can be oxidized and become water soluble, the COD and TOC of this AL-containing solution reduced by 45 % and 20 % respectively. The color of the solution changed from dark to light yellow. This process offered a new process of treating/oxidizing AL-containing wastewater in pulp and paper industry.