The Fluorine-Containing Wastewater Treatment In The Production Of High-purity Graphite

Graphite is a kind of important mineral resources, widely used in many field.Graphite resources is very abundant in Heilongjiang Province, the most reserves the world, but at present, graphite industry is lack of scientific and technological content.The exploit and utilization of resources is rugged, high purity graphite that cutting-edge technology and national defense need have to be imported in great quantities, which producing huge trade deficit. High purity graphite production is an important topic of the graphite enterprises in Heilongjiang province, and wastewater treatment related to high purity graphite production is one of the important content of this subject. For reasons of economy and practicality, the high purity graphite production mainly use the hydrofluoric acid method, as a resault,a large amount of wastewater containing fluorine is produced. Wastewater that contains excessive fluoride will pollute the environment, do damage to the crops and livestock’s normal growth, even seriously affect human health, process research of removing fluoride in industrial wastewater is particularly important.The research object of this article is fluoride wastewater from Aoyu graphite company, the fluoride wastewater from graphiteproductionhas the characteristics ofstrong acidity and high content of fluorine ion.The most effective treatment method is to use lime for processing. The current treatment of lime cost huge dosage, treatment effect is not good, so,the process need to be study and improve.The experimental material is based on the original factory wastewater,through the comparing of different precipitant,adding way of CaO and the amount of CaCl₂,the optimal precipitant,addition way and suitable drug dose range of CaO and CaCl₂ is determined.Then,the interaction between CaO, CaCl₂, and PAC was determined by the orthogonal test,the best solution is found through another orthogonal test.Then the contrast verification test is carried out. The final plan is that, every 80 ml of raw water, adding 140g/L CaO, 25g/L CaCl₂, 1600 mg/LPAC,300 mg/LPAM. This scheme can treat the original water from fluoride concentration of 30000 mg/L, PH around 1 to fluoride concentration of 4.6mg/L, PH is 7 8, 24 hours of sludge volume average of 69.25 ml（plus or minus 1 ml）, 30 minutes average sludge settling velocity is 3.9 ml/min（plus or minus 0.3 ml）.Treatment of fluoride wastewater usually contains precipitation—coagulation secondary process. Lime precipitation process is the core of the processing steps,usually the fluorine ion in effluent after lime precipitation treatment is around 30 mg/L,then the effluent overflow to a coagulation process which can make the water down to standard.The reasearch is aim at the precipitation process, optimizing the parameters of this section.Soit can provide guidance for precipitation process, improve the efficiency and save cost,it can also lighten the load for subsequent technology,so it is of certain engineering significance.