Study On Futher Treatment Of Fluoride-containing Wastewater From Aluminium Production By Using New Material And Technology

Treatment of industrial wastewater containing fluoride has been taken more seriously.This paper indicated the main source and harm of waste water containing fluorine. Based on the research of wastewater containing fluoride from aluminium production, the technology about composite modified zeolite and re-treatment had been studied. These two fluoride removal methods can be applied to different occasions.In this paper, NaCl and Al2(SO4)3 were studied to modified mordenite.The removing fluoride performance of NaCl-Al2(SO4)3 composite modified zeolite was researched.The pH value, temperature,contact time and other factors which can affect the fluorine performance were studied.The mechanism of fluoride removal about the composite modified zeolite was discussed.Base on the research of the modified zeolite,fluoride-containing wastewater from aluminum industry were classified according to the level of the fluoride, the water which has higher fluoride content was treated by carbide slag at first, and then mixed with the water which contains less fluoride. Aluminum sulfate, carbide slag and polyacrylamide (PAM) were used in re-treatment of wastewater.The factors and mechanism of fluoride removal about the re-treatment technology were discussed. Further defluorination can be realized by using both the re-treatment technology and NaCl-Al2(SO4)3 composite modified zeolite.Research results show that:(1) The effect of modified zeolite by using NaCl and Al2(SO4)3 is obvious; when 6% NaCl and 15% Al2(SO4)3 are used to modify zeolite, the fluoride removal rate is up to 59.60%. When water temperature and pH value fluctuate,the modified zeolite has a good adaptability. (2) Fluoride-containing wastewater from aluminium production were classified according to the level of the fluoride, the water which has higher fluoride content reacted with carbide slag and coagulation-sedimentation at first, and then mixing with the water which contains less fluoride. Then the re-treatment was operated by using aluminum sulfate, carbide slag and polyacrylamide (PAM).The concentration of fluoride ion is less than 9 mg/L when the concentration of aluminum sulfate reaches 0.27g/L～0.30g/L. This luoride concentration can meet the discharge requirements. Then aluminum processing enterprises can treat some re-treated wastewater by NaCl-Al2(SO4)3 composite modified zeolite,the fluoride ion concentration can be reduced to 3.43mg/ L,reaching the quality requirements of reuse water to most of the process. (3) In the re-treatment process,Al2 (SO4) 3 play an important role as reactant, the fluoride removal law of NaCl-Al2(SO4)3 composite modified zeolite is not entirely consistent with the Langmuir and the Freunlich isotherm,so its mechanism of fluoride removal is not limited to physical adsorption and ion exchange, the complexation reaction works also.Experimental study in this paper kept in touch with practical workshop and accorded to the actual situation of industrial.When we established the experimental programs including the operation and the experimental material, etc, the treatment's effect and operation cost were considered always. The technical program has a good practical and extension.