Study On The Production Mechanism Of Metal Hydride Flocs In Electrocoagulation Process

With the development of chemical industry,wastewater treatment has become an urgent problem to be solved.Currently electrocoagulation technology is applied to treat various kinds of waste water.Most scholars only concentrated on optimization of operating conditions,but there are few studies on the electrocoagulation separation mechanism.The electrocoagulation technology separates and removes contaminants from the water through the exclusive adsorption of flocs,net capture,and adsorption bridges.The production and adsorption of metal hydroxide floc in electrocoagulation process determines the efficiency of electrocoagulation,and the production and structure of flocs will play a crucial role in the electrocoagulation efficiency.This paper focuses on the production and structure of flocs on the efficiency of their adsorption pollutants mechanism.Due to?-FeOOH and?-FeOOH are rich in hydroxyl radicals,they have good adsorption properties.The influence mechanism of process parameters such as aeration rate,initial pH value,and precipitation time on the metal hydride flocs structure in electrocoagulation process was proposed.The dye wastewater and copper-bearing wastewater were selected as the treatment targets,and the effects of floe production and structure on the efficiency of its adsorption pollutants were explored.The results showed that with the increase of aeration rate,?-FeOOH and?-FeOOH in iron flocs were gradually oxidized to?-Fe₂O₃.The longer the precipitation time,the lower the content of?-FeOOH and?-FeOOH,and the higher the content of?-Fe₂O₃ in the flocs.At pH<5,the flocs are mainly in the form of?-FeOOH and?-FeOOH.At pH>5,the iron flocs are mainly?-Fe₂O₃ and?-FeOOH.Under alkaline conditions,the addition of trace amounts of Na₂SiO₃ or EDTA reagents can effectively inhibit the conversion of?-FeOOH to?-FeOOH and?-Fe₂O₃.The effects of supporting electrolyte types and electrode combinations on flocs production and structure were proposed.In addition,the electrochemical performance of electrodes during electrocoagulation was studied.It was found that support electrolyte have a greater impact on flocs production and structure.In the electrocoagulation of aluminum electrode,the amount of aluminum flocs produced when NaCl+Na₂SO₄ is the supporting electrolyte is the most,and the aluminum flocs structure is mainly AlO?OH?.The polarization curve of the Al electrode was studied.It was found that the NaCl solution was the electrolyte with the lowest corrosion potential,the highest self-corrosion current,and the highest Al³⁺precipitation.In the electrocoagulation of iron electrode,when the supporting electrolyte is NaCl+Na₂SO₄,the amount of iron flocs produced is the largest,and the structure of iron flocs is mainly?-FeOOH.When the electrolyte is NaAc and NaNO₃,the production of iron flocs is extremely low.Therefore,electrocoagulation with Ac^-and NO₃^-wastewater in the electrocoagulation using iron electrodes will reduce the electrocoagulation separation efficiency.In electrocoagulation of zinc electrode,the amount of zinc flocs produced when Na₂SO₄ is an electrolyte is the largest,and the zinc flocs is mainly in the form of Zn?OH?₂.From the anodic polarization curve analysis of Zn,the corrosion rate of Zn electrode in Na₂SO₄ and NaCl solution is the largest.When the anode material is the same,the flocs production is highest when the cathode material is aluminum.When the cathode materials are the same,the output of EC flocs under different anode materials is in the following order:aluminum>iron>zinc.