Study On Extraction And Separation Of Waste Hydrochloric Acid Containing Iron

Before the steel plate is cold-rolled,hydrochloric acid is generally used to remove the surface rust.When the hydrogen chloride content in hydrochloric acid is less than 10% and the total iron ion content is 60 to 130 g/L,the acid solution cannot be used any more and waste hydrochloric acid is formed.China will produce a large amount of cold-washed pickled waste hydrochloric acid each year.It is estimated that approximately 190 tons of cold-rolled pickled waste hydrochloric acid will be generated in 2017,and this kind of waste hydrochloric acid has been listed in the ?National Hazardous Waste List?.Waste hydrochloric acid contained11.45%(143.12 g/L)of total iron,9.68%(121.12 g/L)of ferrous iron,1.77%(22.12 g/L)of ferric iron,and 0.67 mol/L(24.61 g/L)of hydrogen chloride.And trace silica solids.It can be seen that the proportion of recyclable resources is relatively large.If it is handled improperly,it will not only result in waste of resources but also harm the environment.Through literature surveys and field visits,there are many ways to treat this type of waste hydrochloric acid,which is based on comprehensive comparison of merits and demerits.The extraction method is characterized by its short cycle,small footprint,low cost,high efficiency,and wide source of raw materials.There is great potential in dealing with this kind of waste hydrochloric acid.Solid-state extraction and separation using extraction method,and explore its optimal extraction conditions.The extractants used in this article are N235(trioctyl/tert-alkyl tertiary amine),P204[bis-(2-ethylhexyl)phosphoric acid],TOA(tri-n-octylamine),TBP(tributyl phosphate),P507(2-ethylhexylphosphonic acid 2-ethylhexyl ester),P350(methylphosphonic acid two heptane),diluents are toluene,glycerol,iso-octanol,and sulfonated kerosene,respectively,and are mixed into organics in different proportions.Phase,at the time when O/A = 1:1,the rust-removing waste hydrochloric acid of a cold-rolled steel plate plant was extracted and separated.The results showed that: in [25% N235 + 70% sulfonated kerosene + 5% glycerol(all volume percentages)],the total iron extraction rate in the back extraction rate was 20.75% and30.52%,respectively;the ferrous extraction rate and the The extraction rates were 6.3% and42.76%,respectively.The extraction rate and stripping rate of acid were 87.41% and 6%,respectively.The separation factor of iron ion/chloride ion was 30.07 and 3.1,respectively.The acid extraction/separation coefficient and the extraction separation coefficient were103.28 and 11.7,respectively.By comparing the separation of All ions and H2 O by different extractants,it can be clearly seen that the extraction amount of TBP,P350 and P507 is relatively low,the extraction rate is 10%-15%,the reverse extraction volume is relatively low,and the reverse extraction rate is 20%-40%,of which TBP back extraction rate is more prominent,can have 60%,but its total extraction rate is about 13%.N235,P204,TOA extraction is relatively large,the extraction rate is above 15%;the amount of back extraction is also relatively high,the reverse extraction rate is between 40%and 80%,of which N235 performance is particularly prominent,the total extraction rate is as high as 21%.The extraction rate was as high as 35.4% and the reaction conditions at this time were(25% N235 + 70% toluene + 5% glycerol).The effect of using N235-P204 synergistic extraction system is not as good as that of using N235 alone.Therefore,after establishing that the organic phase composition is [25%N235+70%sulfonated kerosene+5% glycerol(all volume ratios)],explore the conditions under different waste acid concentrations,mixing oscillation time,temperature,and oscillating intensity.Effect on extraction efficiency.The experimental results show that with the increase of the dilution times(2-15 times),the extraction rate of ferrous iron is more obvious,and the other extraction rates of total iron and acid are not much changed.This may be due to the fact that extractant extraction of ferrous iron reaches saturation capacity,so the efficiency of ferrous extraction is improved.However,the saturation capacity of the extraction agent for extracting ferric iron and the acid has not yet been reached.Therefore,as the original waste acid is diluted,the extraction efficiency does not change significantly.The mixing oscillating time reaches the equilibrium state of extraction in 15 minutes.If the ultrasonic oscillation is used,the time for reaching the equilibrium state can be shortened by half,and the equilibrium state can be reached at about 6 minutes.The final experimental results showed that the machine phase composition was [25%N235+70%sulfonated kerosene+5% glycerol(all volume ratios)],which could better separate the hydrochloric acid from the waste hydrochloric acid and the extraction rate of its acid.Upto 87.41%.The acidity of the waste hydrochloric acid solution after extraction is greatly reduced,and the problem of difficult oxidation of divalent iron ions is solved.In addition,the extracted hydrochloric acid can be back-extracted with pure water and reused to save production costs and reduce pollution.