The formation of chloride ion from diuron degradation was investigated. The concentration of chloride ion quickly increased with increasing the reaction time, suggesting a very fast degradation/dechlorination stage (Fig. 6a). The total amount of chloride ion produced after 60 min of irradiation time was approximately 8.2 × 10−5 mol L−1 (95% conversion of the diuron chloride content). Therefore, the quantity of chloride ion released from diuron mineralization was lower than that expected from stoichiometry indicating that chloride remained adsorbed onto the photocatalyst surface [41].