Study On The Technology Of Magnetic Fe₃O₄ Disposal Of Copper Smelting Pollution Acid

Arsenic,associated element of copper mine,was a part of waste acid with flue gas at smelting process of copper concentrate.The output of waste acid was too much,which was 100 to 200 thousand cibe when the output of blister copper was 100thousand ton every year.The content of waste acid was much and in which were much sulfuric acid and other heavy metal.The concentration of sulfuric acid was about 10 to 100 g/L and the concentration of arsenic was 1 to 20 g/L.Harmless disposal of waste acid was tough,which was deemed to challenge at copper smelting process.There were some problems that a great number of solid waste generated at lime-ferric process and sulfidization process.The cost and requirement of equipment were high at concentrating process.According to advantage of scorodite in arsenic fixed process,ferric oxide was used to dispose waste acid because ferric oxide could play the role of neutralization,adsorption and solidification.The treatment of waste acid was researched which used ferric oxide,and Fe₃O₄ was the greatest material for disposing waste acid.This paper explored the best reaction condition such as Fe/As molar ratio,time,pH and temperature.Fe₃O₄ of precipitation was recycled and utilized,while filtrate was purified by neutralization.The process of treatment was shown and generation mechanism of scorodite was revealed.The difference was great in dissolution,adsorbing and precipitating in reaction between ferric oxide and waste acid.High-voltage experimentation was carried out at150 ^oC to study influence of time,pH and Fe/As molar ratio.The results showed that ferric oxide could dissolve in waste acid and generated scorodite.Fe₃O₄ was the easiest dissolution among ferric oxide.When value of pH was between 1.5 and 2,ferric oxide was easier dissolution and produced scorodite,and higher pH value was bad for dissolving.The best Fe/As molar ratio was 2,which was good for generation of scorodite.Arsenic concentration reduced from 13000mg/L to 2500mg/L by Fe₂O₃and Fe?OH?₃,while arsenic concentration reduced to 12 mg/L by Fe₃O₄.Based on the results of high-voltage experimentation,Fe₃O₄ was chosen as material for disposing waste to study the influence of Fe/As molar ratio,time,pH and temperature at constant pressure.The results showed that a part of Fe₃O₄ was dissolved in waste acid at pretreatment process.The influence of Fe/As molar ratio was great in removal essiciency of arsenic.As reaction time extending,Fe₃O₄dissolved in waste acid gradually and produced ferric arsenate.Then ferric arsenate crystallized and transformed to scorodite.When reaction time was 12 h,the removal essiciency of arsenic was the highest.When value of pH was between 1.5 and 2,ferric oxide was easier dissolution and produced scorodite,and higher pH value was bad for dissolving.Increasing reaction temperature was good for dissolving of Fe₃O₄ and synthesis of scorodite.There was the best effect for removaling arsenic of waste acid at the condition which iron-arsenic mole ratio was 3.15,reaction time was 12 hours,pH was 2 and temperature was 90 ^oC.In this condition the arsenic of filtrate could reach 9.018 mg/L,and removal efficiency of arsenic was 99.93%.The leached arsenic in TCLP of the precipitate generated in condition was 0.82mg/L,which is far low identification standard.Much Fe₃O₄ powder was not reaction with waste acid,therefore,magnetic separation was used for recycling redundant Fe₃O₄ powder.Recycling Fe₃O₄ powder could be used to return to dispose waste acid or to be puddling raw material.The filtrate should be purified to emission.The lime was used to neutralize filtrate and removal residual arsenic.The filtrate after decontamination could be discharged to environment.This paper used Fe₃O₄ powder as the material to dispose waste acid at constant pressure,which could removal most arsenic and form scorodite in precipitate.After recycling Fe₃O₄ powder and cleaning filtrate,the aim that reducing output of hazardous waste was achieved.Solid waste was lower leaching toxicity than identification standard.This process had more short process,more simple operation and lower cost than traditional handling methods.