The heavy metals and calcium-magnesium ions in the wastewater of flue gas wet desulfurization of coal-fired boilers are harm-ful.The study of precipitation and removal law is beneficial to the recovery of useful elements and the reuse of wastewater.The paper used alkaline precipitation method to classify desulfurization wastewater for treatment,and the precipitation products were characterized by SEM-EDS.The results show that the removal of heavy metals,recovery of magnesium resources,removal of fluoride and reduction of wastewater hardness can be achieved by using Ca(OH)2 as precipitator.In the process of removing heavy metal ions,when the pH value of desulphurization wastewater is 9.0～9.5,the heavy metal ions in the wastewater can be effectively removed and meet the discharge standard.Magnesium ions have almost no loss,and the calcium increase rate is also relatively low,only below 4.6％.Adjusting the pH value of the wastewater to 9.5～9.7 can effectively recover the magnesium element in the wastewater,the recovery rate of magnesium is above 62％,the recovery effect is better.Under the alkaline condition,adding Na2CO3 into the wastewater can effectively reduce the cal-cium ions and residual magnesium ions in the wastewater and achieve the goal of reducing wastewater hardness.The SEM-EDS spectra of precipitates at different pH values show that the removal of heavy metal pollutants and recovery of magnesium element can be a-chieved by staged pH treatment of desulphurization wastewater.By studying the precipitation law of heavy metals and calcium-magnesi-um scaling ions in desulphurization wastewater,the reuse of useful components of separating and separating salts in wastewater was real-ized,and the possibility of secondary pollution caused by dangerous waste of miscellaneous salts was avoided,the target of zero discharge of desulphurization wastewater was achieved.
desulphurization wastewateralkali precipitationheavy metal ionscalcium and magnesium ions
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