TIO₂-MODIFIED ZEOLITE-CARBON NANOTUBES COMPOSITE ELECTRODE FOR PHOTOELECTRODEGRADATION OF PENTACHLOROPHENOL FROM WATER UNDER UV IRRADIATION

Abstract

Three types of composite electrode materials, i.e. carbon nanotubes-epoxy (CNT), zeolite-carbon nanotubes-epoxy (ZCNT) and TiO2-modified zeolite-carbon nanotubes-epoxy (TiZCNT), were synthesized, morphologically and electrically characterized, and tested in the photoelectrodegradation of pentachlorophenol (PCP) from water. The electrode composite materials were synthesized by the two-roll mill method, and a higher porosity of zeolite-modified electrode, caused by the zeolite incorporation, was noticed by means of scanning electron microscopy. Electroactive surface area, determined by classical methods using cyclic voltammetry (CV), and electric conductivity, determined by the four-point method, were negatively affected by the presence of zeolite. The photoelectrochemical behaviour of the electrodes, under ultraviolet (UV) irradiation, towards the pentachlorophenol oxidation was studied, and the photoelectrocatalytic activity of each electrode was determined. The PCP oxidation occurred in two steps at +0.65 V and +0.94 V vs. saturated calomel electrode SCE under UV irradiation. The oxidation peak recorded at +0.65 V vs. SCE appeared only under UV irradiation and it is considered that the photoelectrooxidation peak corresponded to PCP photoelectrooxidation. Also, the enhancement of PCP electrooxidation at +0.94 V vs. SCE was noticed under UV irradiation, which confirmed the photelectrocatalytic activity. The performance of the PCP degradation process, expressed as degradation efficiency and electrochemical efficiency, recommended the operation of photoelectrocatalysis at a bias voltage application of +0.8 V/SCE, while the mineralization degree recommended a bias voltage value of +1.5 V/SCE.