Research On Tailings Mortar Neutralization-Vulcanization-Coagulation Technique For Treatment Of Industrial Wastewater Produced By A Non-ferrous Metal Smelting Enterprise

In most recent years, frequently occurred heavy metal pollution accidents postedgreat threat to the environment and human health. A great amount of heavy metalcontaining waste water is generated in the mining, dressing, and smelting process ofheavy metal mining and dressing industry, which accounts for the largest percentageof heavy metal pollutant generation in all industries. Therefore, it is very important toimprove heavy metal containing waste water treatment process for the heavy metalmining and dressing industry.A heavy metal mining and dressing plant in China generates a large amount ofacidic heavy metal containing waste water in production, and the waste water treatedwith existing treatment process cannot meet the standard of <Emission Standard ofPollutants for Copper, Nickel, Cobalt Industry>（GB25476—2010）. Therefore, anappropriate technique and process is needed for waste water deep treatment in thisplant. It is found after investigation that there are alkaline contents like CaO andMgO in the tailings generated in the mining and dressing process, and the smallparticles in the tailings are mainly composed of clay minerals and oxidants of iron andaluminum. These tailings can not only neutralize acid, and also precipitate and adsorbheavy metal and other pollutants, which provide a feasible method to treat acidicheavy metal containing waste water.Based on the characteristics of tailings mortar, this study discussed the feasibilityof using tailings mortar to neutralized acidic heavy metal containing waste water,designed lab experiment of neutralization-sulfuration-coagulation with tailings mortarand its pilot test, discussed treatment effects and ranking of influencing factors forabove heavy metal containing waste water treatment process, and fixed up theoptimum process parameters. Major study process and results are:a)studied the neutralization effect of tailings mortar with acidic heavy metalcontaining waste water, and discussed the mix ratio of the tailings mortar and wastewater （mortar water ratio‘hereafter）, effect of reaction time of the mortar and acidicwaste water to concentration and pH of effluent. The results indicated that a higher mortar water ratio improved waste water treatment effect, the heavy metal contentdecreased and pH increased for the waste water after neutralization with tailingsmortar. However, this method cannot help decrease arsenic, cadmium, and nickellevel to meet the requirement of <Emission Standard of Pollutants for Copper, Nickel,Cobalt Industry>（GB25476—2010）.b)studied the neutralization-sulfuration-coagulation process treatment effect oftailings mortar to acidic heavy metal containing waste water. The results demonstrateda excellent heavy metal removal effect of waste water by tailings mortarneutralization-sulfuration-coagulation process.16set of experimental data indicatedthat over99%nickel, copper, lead, arsenic, and cadmium were removed, and theheavy metal content and pH of the effluent met the emission standard.c)A pilot test was carried out with industry waste water in plant based on the labexperiment. The results indicated that heavy metal content in the effluent of all16setof test met the emission standard, but some COD_crdidn‘t. After comprehensiveequilibrium analysis, the optimum process parameters are fixed as: mortar water ratioat12:1, feed amount of sodium sulfide at15mL/L, reaction time of sodium sulfide at30min, feed ratio of ferrous sulfate and waste water at0.03, coagulation time at30min.Test results confirmed that at above condition, the pollutants removal effect werealmost all better than other tests, and COD also met the emission standard, whichproved the reliability of these process parameters.d) Heavy metal leaching experiment showed low leaching toxicity of precipitantafter reaction, which indicated precipitants generated with this method would notaffect underground water and surrounding environment.