Study On Harmless Treatment And Valuable Elements Recovery Of Neutralization Residue From Copper Mine Acid Wastewater

Copper plays a very important role in the national economy.In recent years,with the rapid development of economy,the demand for ore in copper smelting industry is increasing day by day.In the mining process of copper mines,acidic wastewater containing low pH value and high concentration of heavy metal ions and sulphates is often discharged,which pollutes the surrounding environment,groundwater and harms human body.Widely used at present,the treatment of acidic wastewater lime neutralization and its derivative method,engineering utilization rate as high as over 90%,in the long term causes a large amount of residue and accumulation is difficult to handle,enrichment of copper,iron and other metal elements in residue if direct landfill waste of resources,not only the heavy metal elements such as copper,nickel and arsenic under the effect of acid rain will into the soil and groundwater pollution environment,with the increasingly strict environmental protection,these piles of neutralization residue has been unable to meet the requirements of environmental protection,it must be harmless treatment.At present,researchers of many research related smelting of acidic waste water disposal,but the study about harmless treatment and resource recovery of residue is almost blank,therefore,it is of great significance to adopt appropriate methods to recycle resources and develop green cycle by using proper methods to treat toxic elements and recycle valuable metal elements in neutralization residue.By means of XRF,XRD,SEM-EDS,laser particle size analysis and other detection methods,on the basis of determining the composition and occurrence state of the valuable elements in the neutralization residue,the E-pH diagram of the water system of copper,iron,zinc,nickel and arsenic was drawn,indicating the regions where the relevant substances are stable existed in ionic state in the aqueous solution.Thermodynamic analysis shows that when pH is between 0 to 3,the valuable elements in neutralization residue can be removed in aqueous solution in the form of ions.During the experiment,the neutralization residue was treated by acid leaching and valuable metal was recovered with sulfuric acid system.The influences of sulfuric acid volume concentration,liquid-solid ratio,reaction temperature,reaction time and stirring speed on the leaching process of neutralizing slag were studied by single factor test and orthogonal experiment-Finally,the optimum leaching conditions of neutralization slag were determined as follows:Under the conditions of 15%of sulfuric acid concentration,3:1 of liquid-solid ratio,80℃ of reaction temperature,120 min of reaction time and 250 rpm of stirring speed,the leaching rate of copper reach 99%,iron 96%,zinc 90%,nickel 94%,arsenic 89%.After the toxicity test of HJ/T299-2007,the content of Cu,Fe,Zn,Ni and As has been reduced to the national standard GB5085.3-2007 below the prescribed dangerous value,which can be sold as general solid waste stable discharge,and harmless to the environment.On the basis of acid leaching,the enriched copper,iron and a small amount of arsenic,zinc and nickel in the leaching solution were recovered.Determines its "In advance to remove iron and sulfide method to recover the copper(nickel,zinc)then sodium sulfate evaporates and crystallizes" as the main system of the craft route,and optimizing the experiment conditions of lye types,the amount of hydrogen peroxide,the methods of iron and arsenic separation,the dosage of sodium hydrogen sulfide,vulcanization reaction time and satisfy the pH control points,the best experimental conditions is:the pH of remove iron and arsenic in advance control in 3.5,the dosage of hydrogen peroxide is 10 ml/L,30 min of the reaction time.In the vulcanization process,2 g/L sodium hydrogen sulfide was added,and 20 min of the reaction time.Neutralize pH is 7.5 in the standard discharge stage,and the reaction time is 60 min.Iron hydroxide,iron arsenate precipitation,sulfide slag,sodium sulfate crystal recovery,among which sulfide slag copper grade of 57%has economic value,standard water discharge or return to the washing process.