Degradation of calcium lignosulfonate using gamma-ray irradiation

Gamma-ray irradiation was proven to be a promising means for the removal of calcium lignosulfonate (CaLS). At a dose rate of 55 Gy min(-1), over 90% of CaLS was mineralized to CO2, H2O and sulfates within 3-d irradiation. The degradation of CaLS with the initial CaLS concentrations ranging from 40 to 200 mg l(-1) followed zero-order kinetics at the dose rates of 16-150 Gy min(-1). The zero-order degradation rate constant was functionally related with irradiation dose rate. Experiments performed with or without addition of radical scavengers demonstrated that the role of OH was predominant in CaLS degradation and the reductive species made minor contributions to CaLS degradation. Addition of appropriate amounts of H2O2 significantly enhanced the mineralization of CaLS, e.g., addition of 10 mM H2O2 at a dose rate of 55 Gy min(-1) elevated the mineralization rate constant by five times. The addition of Fenton's reagent to irradiated CaLS solutions facilitated the degradation of CaLS, but no obviously synergistic effect was observed. (C) 2004 Elsevier Ltd. All rights reserved.