Research On Electrocatalytic Conversion Of Nitrate And Sulfide

Water resources shortage and sewage treatment have been widely concerned by the society,therefore various methods are being developed to treat agricultural,industrial and domestic sewage.Among them,nitrate sewage and sulfide sewage are two common and stubborn forms of sewage,existing in animal husbandry,petroleum industry,mineral industry,leather manufacturing industry,domestic water and other sources of sewage,which have a huge impact on the nature and human society.In this paper,nitrate wastewater and sulfide wastewater are treated by electrocatalysis,and nitrate and sulfur ions are converted into high value-added chemical products,namely ammonia and sulfur.The main contents of this paper are as follows:（1）Preparation of D-Cu₂O/Cu/CF material for electrocatalytic nitrate reductionThe D-Cu₂O/Cu/CF material as well as corresponding contrast samples were prepared by single step electrodeposition.The electrocatalytic reduction performance of D-Cu₂O/Cu/CF material was tested under the conditions of low concentration and high concentration nitrate.Under low nitrate concentration,the Faraday efficiency,conversion,selectivity and ammonia yield rate of the materials were 87.1%,98.9%,40.0%and 10.7mg·h^-1·cm^-2,respectively.Under high nitrate concentration,the material showed a stable current density of 1 A·cm^-2and an ammonia yield rate of 49 mg·h^-1·cm^-2.The change of ion concentration during the reaction,the change of copper valence before and after the reaction,and the catalytic performance of different contrast samples.Moreover,the reaction intermediates and material surface changes have been investigated through in-situ infrared spectroscopy and in-situ Raman spectroscopy.The synergetic effect between Cu⁺and Cu for efficient electrocatalytic nitrate reduction has been proposed,which is also confirmed by DFT calculation.（2）Preparation of Ni/NF materials for electrocatalytic sulfide oxidation and co-electrolysis of sulfide and nitrateNi/NF materials were prepared by multi-step electrodeposition.The influences of deposition time,alkalization and other preparation conditions on the properties of the materials were investigated.The Faraday efficiency and sulfur yield rate were 98.0%and66.12 mg·h^-1·cm^-2,respectively.The sulfur rate of removal reached 90.9%.Electrochemical co-catalysis of sulfide and nitrate was carried out to obtain two kinds of high value-added chemical products and treat sulfide wastewater and nitrate wastewater at the same time.In the H-type electrolytic cell containing 0.5 mol·L^-1Na₂S and 0.1 mol·L^-1NaNO₃,the electrochemical cocatalysis test was carried out.After 8 hours electrolysis,the removal rate of nitrate and sulfur ion reached 92.86%and 88.37%,respectively,which achieved the purpose of simultaneously treating nitrate pollution and sulfide pollution.Moreover,the ammonia and sulfur generation can be as high as 66.78μg·h^-1·cm^-2and 24.77 mg·h^-1·cm^-2,respitively.