Preparation Of Polyferric Chloride From Steel Pickling Waste Liquid And Its Applied Basic Research

In the process of steel processing,usually need to add acid treatment on the surface of the oxide film,which will produce a large number of steel pickling waste liquor.The waste liquid of steel pickling has the characteristics of strong acid and heavy metal ions.It is a kind of industrial wastewater which is difficult to treat.It can not be discharged directly without treatment.Traditionally,the method of treating the pickling waste is to neutralize the precipitation method,which will produce a large amount of sludge with heavy metals,which is difficult to dehydrate the sludge and even cause secondary pollution to the groundwater.This study analyzed the composition of pickling waste liquor,and explored a way to recycle the waste water of hydrochloric acid pickling.The steel pickling waste liquid was used to prepare polymeric ferric chloride?PFC?and used for water treatment.In this study,the inorganic polymer flocculant polyferric chloride was prepared by direct oxidation of hydrochloric acid pickling waste liquor.The optimum reaction conditions were determined by single factor variable method.This paper discusses the influence of the amount of oxidant,reaction time,reaction temperature,dosage of hydrochloric acid on the conversion rate of Fe²⁺,the amount of the stabilizer,curing time,dosage of hydrochloric acid and reaction temperature on the influence of basicity,optimizing the reaction conditions,draw the following conclusions:?1?When the molar ratio of NaClO₃ to Fe²⁺is 0.1776,the oxidation reaction time is 48min,the conversion rate of Fe²⁺is the highest,and the conversion rate is 98.7%;The amount of acid is 6 mL per 100 mL of pickling waste liquor,and the reaction temperature is the most suitable for normal temperature;The addition of stabilizer can make PFC not precipitate in the process of hydrolysis polymerization,and also can guarantee a certain basicity.Therefore,the curing time of 12 h and KH₂PO₄ adding amount of 0.1 g is the most suitable.?2?Under the optimum reaction conditions,when the dosage of NaClO₃ was 4.3 g,the reaction time?40⁵0?min,the addition of hydrochloric acid was 8 mL,the curing time was12 h and the KH₂PO₄ was 0.1 g,The total iron content in the prepared PFC is about 15.4%and the salt degree is?9¹2?%.The self-made PFC and PFC on the market for Ganjiang River water treatment flocculation experiment.The flocculation performance of the two flocculants was compared by investigating the removal effect of flocculants on the turbidity of the river water,and the reaction conditions were optimized.The following conclusions were obtained:?1?Flocculation comparison experiment showed that under the same reaction conditions,the removal of turbidity by self-made PFC was inferior to that of PFC sold on the market;When the dosage of flocculant was the same,the removal rate of PFC was lower?5¹5?%than that of market PFC,but the homemade PFC had a wider range of adaptability to raw water pH.?2?The experiment results show that when the self-made PFC in dosage of 200 mg/L,the speed of 150 r/min,pH value is?8⁹?,flocculation reaction temperature,stirring time 8min,settling time 20 min after the reaction,the residual turbidity was 4.48 NTU,the removal rate reached 86.3%,the turbidity removal effect is the best.Considering the stability of PFC,chitosan?CTS?and PFC were mixed at certain mass ratio to obtain CTS-PFC,so as to achieve the purpose of modification.The modified PFC and unmodified PFC were used together to treat municipal sewage.The decolorization rate and COD_Crr removal rate of flocculants were investigated to determine the flocculation performance of PFC before and after modification,and the reaction conditions were optimized.The following conclusions were obtained:?1?This method can not only improve the flocculation performance of cationic flocculant,but also overcome the instability of PFC by modifying the CTS embedded in PFC;CTS-PFC and PFC for the treatment of city sewage,in under the same reaction conditions of flocculant,the removal rate of CTS-PFC is better than PFC on the city sewage decolorization rate and COD_Cr,CTS-PFC in domestic wastewater treatment by pH and CTS-PFC effects of smaller,faster settlement.?2?Experimental results show that the m?CTS?:m?PFC?=1:2,the curing time is 6 h,the speculation was 1 g/L,pH value is?6⁷?,speed of 150 r/min,the settling time is 15 min,the best flocculation effect,the decolorization rate was 93.7%,the removal rate of COD_Cr50.7%.According to the design plan of this technology,the waste liquid of acid pickling is recycled.The pickling waste liquid treatment per day is 2 t,a total investment of 300thousand and 800 yuan.According to the calculation of 300 days a year,the annual operating response is 171 thousand yuan,the annual processing fee can be entrusted to 9 thousand yuan,product income is 298 thousand yuan per year,equipment depreciation fee of 12 thousand and900 yuan per year.Therefore,the annual profit can reach 123 thousand and 100 yuan.