Study On Lixiviation Characteristics Of Wastewater Sludge From Sulfuric Acid Plants

Sulfuric acid is an important basic chemical raw material,widelyused in iron-steel,metallurgy,petrochemical,chemical,military and manyother fields.During the process of producing sulfuric acid,massivewaste-water,waste-gas,and waste-sludge are discharged and cause severeenvironmental pollution.The quality of sulfuric acid waste-water iscomplex,and will exist different levels of Cu,Cd,Pb,Zn,NiandCr,As andother heavy metals,due to the differences in the sources of raw materialsand production process,sludge generated in waste-water treatment processfor these heavy metal pollutions provides a carrier.At present,the finaldisposal of sludge is to landfill,incineration,touhai,agricultural,or to beused as materials.The side effect is that by corrade and erode action,themetals especially the volatilizable ones would stand a good chance tore-enter the environment and then do harm to the balance of thenature.Different lixiviations when they are in different environmentstatus.Type ownership of waste-water sludg from sulfuric acid plant,athome and abroad have not yet see the systematic reports.This paper takessulfuric acid plant waste-water sludge samples of four large enterprises inHubei Province as sample,heavy metals are distilled by three differentleaching method,study its lixiviation rule,different lixiviations isresearched when they are in different leaching environment status.Themajor study results go like follows:(1)Lixiviations by level shake,in four size fraction of differententerprises,it has little impact on lixiviations of Cu,Cd,Ni and Fe bydifferent size fraction;larger size fraction is conducive to the lixiviationsof Pb,Zn;in YH and XY samples,the lixiviations of Cr is higher when thesize fraction of0.075~0.2mm;in XF and XY samples,the lixiviations ofAs is lower when the size fraction of0.2~2.0mm.(2)Lixiviations by sulfuric-nitric acid,in four size fraction ofdifferent enterprises, it has a certain impact on lixiviations of Cu,Cd,Ni,Cr and Fe by different size fraction;little impact on lixiviationsof Zn;larger size fraction is not conducive to the lixiviations of Pb;thelixiviations of As is higher when the size fraction of0.075~0.2mm,moreobvious to XF sample.(3)Lixiviations by acetic acid buffer solution, in four size fraction ofdifferent enterprises,larger size fraction is not conducive to thelixiviations of Pb;it has little impact on lixiviations of Cu,Cd,Zn,Ni andFe by different size fraction;the lixiviations of Cr increase when the sizefraction less than0.075mm in XF sample,but in XY and HL samples,thelixiviations of Cr increase when the size fraction decrease,more obviousto the size fraction less than0.2mm;the lixiviations of As is higher whenthe size fraction of0.075~0.2mm in XF sample.(4)Through comparing the three leaching methods,the same sludgesample,the lixiviations of Cu,Cd,Zn,Fe is better with level shake andsulfuric-nitric acid,the lixiviations of Pb is better with acetic acid buffersolution,the lixiviations of Ni,Cr,As is almost with the levelshake,sulfuric-nitric acid and acetic acid buffer solution,specifically selectwhich method,depending on the particular circumstances.(5)In YH sludge sample,when the size fraction is uniform,the levelshake and acetic acid buffer solution are applicable,others,when the sizefraction is uneven,sulfuric-nitric acid is applicable.(6)In XF and HL sludge samples,when the size fraction isuniform,the level shake or sulfuric-nitric acid is applicable,others,whenthe size fraction is uneven,the acetic acid buffer solution is applicable.(7)In XY sludge sample,when the size fraction is uniform,the aceticacid buffer solution is applicable,others,when the size fraction isuneven,the level shake and sulfuric-nitric acid are applicable.(8)This article carried leaching toxicity test on the waste-watersludge of sulfuric acid plant,in accordance with 《Hazardous WasteIdentification Standard Leaching Toxicity Identification》GB5085.3-2007,this kind of waste-water sludge should be attributed to dangerous waste,so its treatment and disposal must be in accordance withthe hazardous waste management requirements.