Experimental Research On Removal Of Chloride Ion In Wastewater By Lime With Aluminum Salt Precipitation Method

Chloride ion?Cl^-?is one kind of common corrosive anion in wastewater,the high concentration of chloride ion could lead to corrosion of metal pipeline,salinization of soil,negative effect on plant growth,even harm to human body.Consequently,it is especially important to control emission concentration of chloride ion in wastewater.Currently,partial areas in the state have promulgated relevant regulations on chloride ion in wastewater,eg.,Liao Ning Province sewage discharge standard DB21/1627-2008,requires that directly discharged chloride ion concentration in water should not exceed 400mg/L,and in collecting website system sewage plant chloride ion concentration not more than 1000.0mg/L.With the emphasize on ecological environmental protection,as well as constant attention on environmental quality and ecological environmental concerns,chloride ion emission standard is getting more strictly,so degradation of chloride ion in wastewater will become an inevitable trend.In this paper,the wastewater containing a single chloride ion?Cl^-?,chloride ion?Cl^-?and sulfate ion(SO₄^2-)coexistence,chloride ion?Cl^-?and carbanion(CO₃^2-)coexistence as the research sample,taking advantage of lime with aluminum salt precipitation method,and used calcium oxide and sodium aluminate as raw materials to make reaction with chloride ion in wastewater,in order to get rid of chloride ion through sediment,and through the experimental research of SO₄^2- and CO₃^2- on the Clremoval effect.Finally,the appropriate process conditions for the removal of Cl^- from different water samples were analyzed by experiments,and the main research conclusions as followings:?1?By lime with aluminum salt precipitation method to get rid of chloride ion out of a single Cl^- content wastewater,the effect of mole ratio of reagents,stirring speed,reaction time,reaction temperature,different initial concentration of Cl^- on removing Cl^- from wastewater was investigated.It also researched experiment of structural characteristics of precipitation products.The conclusions as followings:under the conditions of temperature 25?,reagent ratio n?Ca?: n?Al?: n?Cl?= 20:5:2,stirring speed 400r/min,reaction time 2h,its chloride ion removal rate achieved88.6%,and favorable layered effect between final sediment and supernatant liquid.Moreover,chloride ion content in wastewater was reduced from 2500.0mg/L to283.2mg/L.Meanwhile with the increase of concentration of Cl^-,the removal rate increased first and then decreased.And the precipitate of Ca₄Al₂Cl₂?OH?₁₂ is Freund's salt by XRD analysis,the Ca₄Al₂Cl₂?OH?₁₂ has incomplete layered structure by meansof SEM.?2?By lime with aluminum salt precipitation method to dispose of chloride ion?Cl^-?and sulfate ion(SO₄^2-)coexistence in wastewater,the effect of different initial concentration of SO₄^2- on removing Cl^- from wastewater was investigated,and the influence of certain concentration of SO₄^2- on removing the different initial concentration of Cl^- from wastewater was studied.The conclusions as followings: the lower the initial concentration of SO₄^2-,the higher the removal rate of Cl^-.And under the conditions of SO₄^2- initial concentration decreased to 500.0mg/L,temperature25?,reagent ratio n?Ca?: n?Al?=4:1,n?Ca?: n?Cl?=10:1,stirring speed 400r/min,reaction time 2h,its chloride ion removal rate reached 62.8%.Moreover,chloride ion content in wastewater reduced from 2500.0mg/L to 929.7mg/L.In addition,between final sediment and supernatant liquid,the layered effect was favorable.Under the conditions of SO₄^2- initial concentration decreased to 500.0mg/L,the higher the initial concentration of Cl^-,the lower the removal rate.In the end,by research to the resource recycling of the precipitate could remove the concentration of 500.0mg/L SO₄^2- and lower concentration of Cl^- from wastewater.?3?By lime with aluminum salt precipitation method to dispose of chloride ion?Cl^-?and carbanion(CO₃^2-)coexistence in wastewater,the effect of different initial concentration of CO₃^2- on removing Cl^- from wastewater was investigated,and the influence of certain concentration of CO₃^2- on removing the different initial concentration of Cl^- from wastewater was studied.The conclusions as followings: the lower the initial concentration of CO₃^2-,the higher the removal rate of Cl^-.And under the conditions of CO₃^2- initial concentration reduced to 500.0mg/L,temperature 25?,reagent ratios n?Ca?:n?Al?=4:1,n?Ca?: n?Cl?=10:1,stirring speed 400r/min,reaction time 2h,its chloride ion removal rate reached 65.1%.Moreover,chloride ion content in wastewater reduced from 2500.0mg/L to 872.6mg/L.In addition,between final sediment and supernatant liquid,the layered effect was favorable.And according to the experimental result,when the wastewater containing Cl^- and CO₃^2-,the higher the initial concentration of Cl^-,the lower the removal rate.In the end,by research to the resource recycling of the precipitate could remove lower concentration of Cl^- from wastewater.