Study On Arsenic Removal In Wastewater From Bacterial Oxidation Of Refractory Gold Ore In Gansu

At present,bacterial oxidation method has become main method of processing refractory gold ores,so large amount of bacterial oxidation liquid waste are generated.Bacterial oxidation liquid waste has strong acid,high arsenic and high iron characteristics.Chemical neutralization precipitation is generally adopted in industry to deal with this kind of liquid waste,enabling arsenic to generate ferric arsenate sediment of relatively stable scorodite structure and being removed from solution,so a large amount of arsenic waste residue are produced.The processing of arsenic waste residue in industry usually adopts pile up or landfill treatment.But in the middle of processing arsenical wastewater,we cannot ensure that all the generated residues containing arsenic are of stable scorodite structure,so the research on the stability of residues containing arsenic is necessary.The article takes waste water generated in a gold ore in Gansu as object of study,taking calcium oxide and magnesium oxide as precipitator,and using the feature of solution itself to neutralize and remove arsenic by chemical precipitation method.Making process mineralogy analysis on slag phase and studying its leaching toxicity so as to provide basis for follow-up study of the effect of mole ratio of iron and arsenic on stability of arsenic sedimentation:making X-ray scattering analysis on slag phase produced by bacterial oxidation liquid waste in different mole ratio of iron and arsenic and perform experiment of the stability of arsenic in simulated natural environment.The main research content and result are as follows:According to the difference of solubility of arsenate of compound,using magnesia or calcium oxide as precipitator to remove the arsenic in waste oxidation liquor,investigating the effect of technological parameter like reaction time,pH,stirring speed,temperature on removal rate of arsenic and iron at one time,and studying the function of magnesium oxide or calcium oxide in the process of arsenic precipitation.The result shows that removing the arsenic of bacterial oxidation liquid waste under the condition of best reaction also can realize the objective of wastewater purification.The roles that magnesium oxide and calcium oxide played in the process of removing arsenic:firstly,adjusting pH,realizing sedimentation of arsenic and iron;secondly,providing Mg²⁺?Ca²⁺ and form refractory arsenic acid magnesium,calcium arsenate precipitation by combining arsenic anion in the solution.the component of arsenic and magnesium sedimentation are relatively complicated,and it can generated stable scorodite structure in low ratio of iron and arsenic?ratio of iron and arsenic is 3?;arsenic and calcium has large amount of gypsum constituents,and this side-fact indicates that calcium oxide as arsenical generated large amount of sedimentation;the longer arsenic and magnesium sedimentation,the arsenic contents in leached solution are greater;the stability is related with molar ratio of iron and arsenic,the larger ratio of iron and arsenic is,the better stability of arsenic in arsenic and magnesium sedimentation;the stability of arsenic and calcium sedimentation is worse than arsenic and magnesium sedimentation;whatever arsenic and magnesium sedimentation or arsenic and calcium sedimentation,the changing trend of content of iron in leaching liquor is consistent with change of arsenic.