Study On Treatment Of Vanadium Smelting Wastewater Containing Heavy Metals And Ammonia Nitrogen: With Process Of Flocculation And Precipitation Combined Adsorption

It is difficult to remove for heavy metals and ammonia-nitrogen in the vanadiumsmelting wastewater. There are few researches on the treatment of this kind ofwastewater at present, and it is lack of effective treatment technique as well. In orderto develop an effective process for treatment of vanadium smelting wastewater, thisresearch studied characteristics of the pollutants and the removal effect of adsorptionprocess using modified activated carbon and flocculation process using ferrous sulfate（FeSO₄·7H₂O） and polyethylene glycol/polyacrylamide （PEG/PAM） mixed flocculantfor treatment of heavy metals in smelting wastewater, and of adsorption process usingmodified activated carbon and macroporous chelating resin for treatment ofammonia-nitrogen. Effects of related factors on the removal of pollutants werediscussed. Basing on optimal conditions, treatment effect of the process ferroussulfate-PEG/PAM flocculation combined two-stage adsorption by D403resin onheavy metals and ammonia complex wastewater.The main research conclusions are as follows.（1） The optimal parameters of Ferrous Sulfate-PEG/PAM mixed FlocculationProcess for treatment of vanadium smelting wastewater （the initial concentrations ofAs, V, Cr, Cd, Fe and NH₃-N are8.18,1.1538,0.1053and1.033mg/L, the initial pHrange is4.0⁵.0） are as follows: dosage of FeSO₄·7H₂O is0.2705g/L, pH range forflocculation is about8.2, preparation ratio for PEG/PAM flocculant is50%,concentration of which is2.0g/L and dosage is25mL/L. Under the optimumcondition, removal rate of As, V, Cr and Cd ions were98.22%,91.08%,100%and94.5%respectively, the pH of treated wastewater is8.0, and the residual concentrationof Fe is0.0530mg/L, which are all meet the national emission standard。But it has noeffect on the removal of NH₃-N.（2） At a adsorption time of8hours and adsorbent dosage of60g/L, the removalrates of V, Cr, Cd, As and NH₃-N adsorbed by modified activated carbon10%AC are76.1%,99.3%,89.1%,14.1%and17.4%respectively. And the increase rate of V, Cr,Cd, As and NH₃-N for modified activated carbon10%AC are30%,75%,7.1%,6.0%,and respectively. The sort of adsorption capability for modified activated carbons is10%AC>5%AC>1%AC>AC.（3） For the removal of NH₃-N, it can be removed from60.0mg/L to10.0mg/L below by two-stage adsorption process with macroporous chelating resin Type D403.The optimal resin dosages of first-stage and second-stage adsorption are200g/L and80¹50g/L respectively. And optimal adsorption times of first-stage and second-stageadsorption are1.0hour and0.5hour respectively. Under the optimal conditions,removal rates of NH₃-N for first-stage and second-stage adsorption were61.7%and62.1%respectively, and after two-stage adsorption the concentration of NH₃-N couldbe reduced to about9.1mg/L.（4） Conduct three sets of parallel processing that treat the vanadium smeltingwastewater with treatment technology which is combined adsorption process usingmacroporous chelating resin D403with flocculation process using ferrous sulfate（FeSO₄·7H₂O） and polyethylene glycol/polyacrylamide （PEG/PAM） mixed flocculant.On the basis of the best parameters of flocculation treatment method and two D403resin adsorption process, the residual concentration range of As, V, and NH₃-N are0.0003⁰.0010,0.071⁰.090and7.30⁷.55mg/L，the residual concentrations of Cr,Cd, Fe are undetected, and value of pH is7.76⁷.86, which are all meet the nationalemission standard.