Preparation Of Palladium Modified Nickel Foam Electrode And Its Application To Chlorophenols Compounds Electrocatalytic Hydrodechlorination In Aqueous Solutions

Chlorophenols compounds with great toxicity are carcinogenic, teratogenic, mutagenic, and difficult to be biodegraded. Their degradation period in the environment is long, and they have caused great damage to the natural environment. So chlorophenols compounds have been listed as priority control of pollutants by many countries. In recent years, more and more investigators have paid attentions to the electrocatalytic hydrodechlorination to deal with chlorophenols compounds, because this method has many advantages such as high flexibility, easy to control, low cost, non-secondary pollution and so on. In this article, palladium-modified nickel foam electrodes were prepared and used as cathode to degrade 4-chlorophenol and 2,4-dichlorophenol. Preparation conditions of electrodes and the influencing factors of disposing chlorophenols compounds were investigated.The preparation technology of the palladium-modified nickel foam electrodes, using the method of constant current electrodeposition, had been optimized in this paper. The preparation conditions, including the deposition current, the deposition temperature, the deposition time and the concentration of PdCl2 solution, were investigated. Experimental results showed that along with the increase of the deposition current, the dechlorination property of Pd/Ni-foam electrode rose firstly, then droped. The increase of deposition temperature could not bring about bigger influence on the dechlorination property. With rising of the concentration of PdCl2 solution, the property got better, but fluctuated with the extension of deposition time. Considering the dechlorination property of electrodes, cost and energy consumption, the best preparation technology conditions were 6mA(deposition current), 40℃(deposition temperature), 1.0mmol/L(concentration of PdCl2), 120min(deposits time, until the yellow PdCl2 solution turned colorless) and the Pd/Ni-foam electrode had good stability and reusability.Some modern physical methods, such as X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), X-ray diffraction(XRD) and so on, were used to characterize the elements and valence, surface morphology and crystal structure of the Pd/Ni-foam electrode. The results indicate that Pd particle had loaded on the surface of Ni-foam substrate and presented micro sizes, uniform distribution, close structure, large specific surface area, and certain space extensibility at the best preparation condition.The effects of initial concentration, current intensity and temperature on the hydrodechlorination of 4-chlorophenol and 2,4-dichlorophenol were examined in the aqueous. Relatively high initial concentration(1mmol/L), moderate current intensity (5mA), and temperature(50℃) were beneficial to improve the hydrodechlorination of 4-chlorophenol in consideration of the removal rate and current efficiency. Under the optimized conditions, 1mmol/L of 4-chlorophenol could be removed rapidly with the rate of 100% after 80min electrolysis. For 2,4-dichlorophenol, the optimized conditions were 0.5mmol/L, 5mA and 40°C, the removal rate reached 62.6% after 180min electrolysis. The degradation of 4-chlorophenol and 2,4-dichlorophenol on Pd/Ni-foam electrode is in good agreement with the fisrt-odrer reaction kinetics equation.