The Research On Spent Pickling Liquors And Sludge Treatment In Metal Surface Treatment

Spent Pickling Liquors(SPL)comes from the process of metal pickling.Acid is used as cleaning agents in pickling of metal surface and a lot of ground such as machinery industry and metallurgical industry.The process generates a large amount of waste acid.Spent pickling liquors is a hazardous waste because it is acidic and contains a large quantity of metal ions.It will cause severe environmental pollution and waste of resource if not properly treated.The traditional neutralization method that putting slaked lime to acid directly will cause secondary pollutant.The sludge of this method will produce a lot of sludge containing a high percentage of metal.This thesis studied the comprehensive utilization of spent pickling liquors and picking sludge by preparing PFC coagulant.This method has a unique environmental and economic significance.A production and processing factory of Zhejiang Province produces a lot of used acid containing a large amount of metal ion especially ferric ion discharges.The factory treats it by putting a large amount of lime and generate sludge containing a large amount of mental ion classified as hazardous wastes.The pickling sludge has a high treating price.This research took the spent pickling liquors and sludge as research object and preparing PFC coagulant from them to discuss a proper way to realize the comprehensive utilization of spent pickling liquors and picking sludge.Aspects of the thesis are:(1)How to recover hydrochloric acid of higher concentration when recovering acid from SPL has been studied.Adding chlorine salt to approve improve the concentration and recovery rate of acid was chosen and 1mol/L Calcium Chloride had a better effect;(2)Some factors of the oxidative polymerization of preparing PFC from SPL were discussed.The results show that under the conditions of the distill rate is 30%,c(P)/c(Fe)=0.1,c(Na Cl O3)/c(Fe2+)=0.15,room temperature,can have the best results.The production can basically meet the requires of HGT 4672-2014 and achieved good results in coagulating experiment.(3)Pickling sludge was acid leached by SPL.Hydrochloric acid was used after SPL..The results show that under the conditions of liquid-solid ratio 8,reaction time 40 min,liquid-solid ratio of hydrochloric acid and sludge 4,proportional reduction of sludge and recovery rate of Fe achieved 68.5% and 87.2% respectively.Excess sludge can be as building materials because of low content of heavy metal.(4)PFC had been prepared from acid leaching solution.The results show that room temperature,c(P)/c(Fe)=0.1,c(Na Cl O3)/c(Fe2+)=0.15,the production can basically meet the requires of HGT 4672-2014 and achieved good results in coagulating experiment.