Preparation Of Modified Pd Electrodes And Their Dechlorination Of 4-chlorophenol

Chlorinated organic pollutants are stable in structure,strong in toxicity,and difficult to biodegrade,which have a "triple effect" on the human body.Chlorophenols Compounds?CPs?in environmental waters can cause serious pollution to the ecological environment and pose a serious threat to the safety of animals,plants,and humans in the water.Based on traditional technology,electrocatalytic hydrodechlorination?ECH?is a green cleaning technology that can degrade and dechlorinate chlorinated pollutants under mild conditions without secondary pollution.It has a good degradation and application prospect for chlorophenol pollutants.Among them,the selection and preparation of electrodes is still one of the focuses and hotspots of domestic and foreign research.In this paper,two kinds of composite electrodes,palladium/polypyrrole reduced graphene oxide/nickel foam?Pd/PPy-rGO/NF?and palladium/ iron-cobalt phosphide/nickel foam?Pd/CoFeP/NF?were prepared.The composite electrodes were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,and other methods.The preparation conditions and electrochemical reduction dechlorination conditions of Pd/PPy-rGO/NF and Pd/CoFeP/NF electrodes were optimized by using 4-chlorophenol?4-CP?as the target pollutant.The specific contents were as follows:?1?PPy-rGO/NF electrode composite material was prepared for one step by a constant current deposition method,and Pd/PPy-rGO/NF electrode was prepared by the pulse deposition method.According to the characterization results of SEM,XRD and XPS,the PPy-rGO intermediate layer was a network nanowire structure,which expanded the specific surface area of the electrode substrate,promoted the deposition of Pd,avoided metal agglomeration,and provided more active sites for dechlorination.Through the dechlorination experiment,the preparation condition,operation condition,and stability of the electrode were optimized.The experimental results showed that: under the operating conditions of electrolyte concentration of 0.05 M,initial pH of 3.0,and dechlorination current of 0.625 mA/cm²,the degradation efficiency reached the optimal after dechlorination degradation for 120 minutes,reaching 95.8%.Under the same experimental conditions,the dechlorination efficiency of the Pd/PPy-rGO/NF electrode could still reach 93.9% after 4 cycles of use,which proved that the electrode has excellent stability.?2?Pd/CoFeP/NF electrodes were prepared by the hydrothermal method and pulsed deposition method.SEM,EDS,XRD,and other characterizations show that the CoFeP intermediate layer presented an uneven sheet-like structure,which provided a larger specific surface area and good dispersion for the loading of Pd particles.The influence of dechlorination conditions on the dechlorination performance of the electrode and the stability of the electrode was investigated.The experimental results showed that: when the concentration of solution electrolyte Na₂SO₄ was 0.05 M,the initial pH of the cathode was 3.0,and the dechlorination current density was 0.75 mA/cm²,the dechlorination efficiency was 91.8% after 120 minutes of electrolysis.The degradation effect of the Pd/CoFeP/NF electrode decreased after four cycles under the same experimental conditions,but the dechlorination efficiency remained at 87%.It might be that the change of electrode surface morphology led to the loss of some active sites,which affects the electrocatalytic efficiency.The experiment showed that the electrode has good stability,and the main product of 4-CP degradation was phenol.In summary,two kinds of composite electrodes were prepared for this paper.The preparation of electrode materials and the conditions of electrocatalytic hydrogenation and dechlorination were investigated with 4-CP as the target pollutant.In general,electrochemical hydrodechlorination technology has a better dechlorination degradation ability for the degradation of chlorophenols organic pollutants in water,which provides a certain technical reference to the treatment of chlorophenols wastewater by reducing the cost of electrode preparation.