Research On Arsenic Precipitation Behavior And Phase Transformation Of Arsenic-containing Wastewater By Hydrothermal Scorodite Method

Arsenic is a highly toxic element and widely present in minerals.As the mining activity progresses,arsenic is also released,and they are entering industrial water.The industrial precipitation method is widely used to treat arsenic-containing wastewater,and the obtained arsenic of pricipitates is easy to environmental influences.In the world,the best harmless arsenic-containing solid waste is scorodite.So the arsenic in the arsenic-containing wastewater is precipitated to form scorodite.It is of great significance for the copper metallurgical to be able to treat arsenic-containing hazardous materials harmlessly.Among the problems,the experimental materials are arsenic-containing wastewater in the copper smelting process.The arsenic arsenic arsenic was studied by hydrothermal method,and the following research results were obtained:(1)In this paper,the arsenic-containing wastewater produced by the copper smelting process is studied.The effects of macroscopic technical parameters such as Fe/As molar ratio,initial p H,reaction temperature,oxygen partial pressure and reaction time on the arsenic precipitation process and the phase transformation of arsenic slag were investigated.The experimental results indicate that:The arsenic and iron removal rate is 98.14% and 87.68%at initial arsenic concentration 19g/L,initial Fe/As molar ratio of 1.5,initial pH of 1,temperature 160?,agitation speed 500r/min,oxygen partial pressure of 0.6MPa and the reaction time of 3 hours,respectively,under hydrothermal conditions,and the As,Fe,O,H and S content of the arsenic precipitates is 22.15%,25.55%,45.91%,3.02%and 3.37%.The particle size of residue is 18.6?m,and the specific surface area of the arsenic slag is reduced to 0.019m²/g.(2)The Fe(?) oxidation have a significant effect on the phase composition of the As-precipitated residue in the process of scorodite formation.Fe(?) oxidation is first-order reaction.The apparent activation energy of Fe(?) oxidation is 118.075kJ/mol and the reaction is controlled by chemical reaction.After analysis,scorodite is the main phase,the arsenic precipitates is mainly composed of iron and arsenic and contains only tiny amount of sulfur.It is advantageous to form bigger size pricipitates when lower temperatures,innital pH and agitation speed,higher initial Fe/As molar ratio.(3)Hydrothermal precipitation arsenic as scorodite and the conversion behavior of process metastable phases were investigated.Lower initial pH,partial pressure of oxygen and reaction temperature,increased of the molar ratio of Fe/As,extended the reaction time is not only beneficial to increase the precipitation rate of As and Fe in the solution,but also to the metastable coversion in the solution.The phase of the jarosite was transformed to reduce the sulfur content in the pricipitates and promote the growth of the scorodite grain.The SO₄^2- shock absorption peak in the precipitation was weakened,and the specific surface area of scorodite was decreased and the particle size was increased,indicating that the metastable phase of the pricipitates was converted into the scorodite phase.(4)More than 98% of the arsenic in the arsenic-containing wastewater is solidified into a scorodite phase,and the arsenic-containing solution contains 0.56 g/L of arsenic.After deep arsenic removal by microbiological or membrane separation,Reachable emission standards.