Study On Treatment Of Fluorine-containing Wastewater From Titanium And Titanium Alloy Processing

This paper studies the fluorine-containing acid pickling wastewater produced by Baoti Group Pipe-Rod Plant.Small-scale experiments was carried out in laboratory with raw water:water quality characteristics were analyzed,the types of precipitators and coagulants were determined,Through a series of single-factor experiments,the treatment effects of the factors such as pH,calcium chloride dosage,stirring intensity,PAC dosage,PAM dosage and settling time under the optimum conditions were explored,and the reaction behavior of calcium fluoride precipitation formation was explored,the paper analyzes the precipitates produced in the stages of chemical precipitation and coagulation precipitation by the method of XRD and SEM tin to obtain the internal structure and surface microstructure of sediment.Based on the experimental results and on the basis of summarizing the disadvantages of traditional treatment methods,this paper designs an improved secondary treatment process of CaCl₂+PAC+PAM.The technical parameters of main structures and equipment in the process plan are explained,Both the investment and operation cost are also estimated,It provides Suggestions and solutions to the problems encountered in the later debugging process.The result of laboratory test shows that it can reduce the fluoride ion concentration in raw water from 120mg/L to 7.8mg/L under the best conditions that the pH is 8,the proportion of calcium chloride dosage is 3.5:1,the dosage of PAC and PAM is 400 mg/L and 3 mg/L respectively,the stirring strength is 150r/min,the precipitation time is 30minutes.Calcium fluoride precipitation behavior experiment finds Calcium fluoride requires 60 mg/L of calcium ions to precipitate and it is necessary to add 1200mg/L¹500mg/L calcium chloride To reduce fluoride to 10 mg/L when fluorine in water is within the initial concentration range of 120mg/L⁵0mg/L.We also find Calcium fluoride precipitation occurs at a concentration of 300mg/L¹000mg/L and Calcium chloride is needed to add 1800mg/L³000mg/L to reduce fluoride ion to 10 mg/L,when fluorine in water is within the initial concentration range of 30mg/L¹5mg/L;XRD analysis shows that all fluoride ions in water have been precipitated in the form of calcium fluoride;The results of SEM analysis shows that PAC and PAM can agglomerate the small colloidal particles together by adsorption,complexation,bridging and netting,which can effectively enhance the sedimentation effect.Cost estimates based on technical parameters of structures and supporting water treatment equipment show that the total investment is 583.9 million yuan,and the daily operating cost is 428.96 RMB.Later engineering debugging results displays that the pickling waste water treatment system can run stably and efficiently in the case of continuous inflow of water.At the same time,after treatment,the effluent quality indexes are as follows:pH is 7 to 8,fluorine ion concentration is less than 10mg/L,COD is less than50mg/L,and the effluent SS can be reduced to 13mg/L through the inclined pipe sedimentation tank and sand filter,which meet the national first-level discharge standard and the expected standard.Fig.20,table 12,64 references.