Photoelectrocatalytic humic acid degradation kinetics and effect of pH, applied potential and inorganic ions

Abstract

AbstractThis study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV254 removal and the degradation of color (Vis400) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10−1 min−1, 8.3 × 10−2 min−1 and 2.49 × 10−2 min−1 (R2 > 0.97) for UV254 degradation and 1.7 × 10−1 min−1, 6.5 × 10−2 min−1 and 2.0 × 10−2 min−1 for color removal from 5 mg dm−3, 10 mg dm−3 and 25 mg dm−3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm−3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV254 removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry