Electro-Fenton Degradation Of Triclosan Using A Graphene Doped Gas-diffusion Electrode

Triclosan (TCS), which is as a typical broad-spectrum disinfectant of pharmaceutical and personal care products (PPCPs), has a quick and good sterilization effect, and also have prominent deodorant, antibacterial effect. It commonly exist in in personal care products such as cosmetics, deodorants, mouthwash, soap and ointment, and also exists in some household objects, such as bedding, kitchen utensils, snacks, dolls and garbage bags. Some research results indicate that TCS is difficult to degradate by microorganism in anaerobic environment and become a potential threat to the ecosystem and human health due to a prolonged stay in environment. At present, there is no a specifical treatment process for TCS in the traditional drinking water and wastewater treatment plants, and the existing treatment process does not remove TCS completely. Electro-Fenton, as an advanced oxidation technique, has many advantages, such as ease of control, amenability to automation, high efficiency, and environmental compatibility, etc. It is more suitable for bio-degradable organic waste water, and has attracted many attentions of researchers in recent years. The in-situ electrogenerated H2O2, which is as the hard-core in the electro-Fenton system, has aroused people greatly research interest. It is important to develop a suitable cathode electrode, increase the oxygen mass transfer to the electrode surface, improve the catalytic activity for oxygen reduction reaction, thus improve the production rate of H2O2. Compared with carbon nanotubes and fullerene, graphene has more excellent mechanical properties, good electrical conductivity and chemical stability. Combined with its special single atomic layer of a two-dimensional structure and high specific surface area, graphene is the outstanding electrode materials used in fuel cell, lithium ion battery and super capacitor. Based on these, a graphene doped gas-diffusion electrode was prepared using rGO, graphite powder and PTFE in this work. An undivided electro-Fenton system was constructed with the reduced graphene oxide (rGO)-doped GDE as cathode and Pt sheet as anode to evaluate generation of H2O2. The influences of the additive amount of graphene, current densities and the electrolyte concentration on electrochemical generation of H2O2and current efficiency were investigated in detail. Then, the electro-Fenton oxidation system was constructed to degrade triclosan model wastewater. The influences of electrolyte pH and Fe2+concentration on the removal rate of triclosan were investigated. Specific as follows: Firstly, graphite oxide was prepared by Hummers’ method, then stripped and dispersed in ultrasonic to obtain graphene oxide, which returned to graphene (rGO) using a method of hydrazine hydrate chemical reduction. The properties, such as structure, chemical composition and purity, were characterized by SEM, TEM, FT-IR, XRD, Raman spectrometer and XPS. The photos of SEM and TEM showed the transparent and plicated structure of rGO.The results indicated that the oxygen-containing functional groups of GO were removed and GO was reduced to rGO.Then, a graphene doped gas-diffusion electrode (rGO/C GDE) was prepared using rGO, graphite powder and PTFE. An undivided electro-Fenton system was constructed with rGO/C GDE as cathode and Pt sheet as anode to evaluate generation of H2O2.The results that the maximum yield of H2O2is187.1mg/L under the conditions of Mgraphite:Mgraphene=8:1, current density of2.0mA/cm2and0.05mol/L electrolyte concentration after180min. Repeat10times, the accumulation of H2O2concentration decreased only7%, which indicated that rGO/C GDE for oxygen reduction reaction has good stability.Finally, the electro-Fenton oxidation system was constructed to degrade triclosan model wastewater. The influences of initial concentration, electrolyte pH and Fe2+concentration on the removal rate of triclosan were investigated. Under the optimal conditions of pH3.0and Fe2+concentrationof0.75mmol/L, nearly73.9%of triclosan can be removed in180min electrolysis. This would provide theoretical basis and the technical parameters of practical application of TCS treatment using electricity-Fenton technology.