Effective Removal and Mineralization of 8-Hydroxyquinoline-5-sulfonic Acid through a Pressurized Electro-Fenton-like Process with Ni-Cu-Al Layered Double Hydroxide

Ni-Cu-Al layered double hydroxide (Ni-Cu-Al LDH) was proposed as an electro-Fenton-like catalyst for 8-hydroxyquinoline-5-sulfonic acid (8-HQS) removal in water. The properties of the prepared catalysts were characterized by using X-ray, SEM and EDAX analyses. The effect of numerous operative parameters on the removal of 8-HQS and total organic carbon (TOC) was studied. Very high level removal of both 8-HQS and TOC (87 and 79 %, respectively) were obtained by using a pressurized electro-Fenton-like process (PrEFL-LDH) atP=10 bars, using a Ti/IrO2-Ta(2)O(5)anode for 6 h. The process presented good performances in a large range of pH (3-10) and gave better removals of 8-HQS and TOC with respect to that achieved by bothi)EF catalyzed by homogeneous (FeSO4) or natural heterogeneous catalysts (pyrite and chalcopyrite) andii)anodic oxidation at a boron doped diamond anode. Ni-Cu-Al LDH retained its catalytic activity after four cycles. Moreover, the carboxylic acid intermediates were identified and analyzed by HPLC.