Electrochemical Oxidation of Lignosulfonate: Total Organic Carbon Oxidation Kinetics

Lignin derivatives account for a significant fraction of biorefractory pollutants in wastewater from the pulp and paper industry. Electrochemical oxidation has been described as an efficient alternative in wastewater treatment based on electrogenerated oxidation. Lignosulfonate was selected in this work as a biorefractory reference pollutant. Total organic carbon (TOC) removal was higher than 80% under the selected experimental conditions, where chemical oxygen demand (COD) was in the range 500-1500 mg O-2 L-1, current density was between 30 and 60 mA cm(-2), and the concentrations of sodium sulfate and sodium chloride supporting electrolytes were 2500 and 5000 mg L-1. Experimental conditions were selected to evaluate the technical suitability of the process and to establish a kinetic model and parameters. Experiments were carried out in a laboratory scale single cell flow electrochemical reactor with boron-doped diamond electrodes. A first-order kinetic model is in good agreement with previously reported results, and kinetic parameters depending mainly on the current density agree well with previous references. A model describing the influence of the current density in the kinetic parameters allows us to calculate the surface electrochemical reaction kinetic constant and the mass transfer coefficient.