Research On New Technology Of Fluorine Removal From High Fluorine Wastewater

The wastewater containing fluorine is an increasing danger to the environment with industrial development.The most commonly used treatment for fluoride removal from industrial wastewater is chemical precipitation.However,it has some disadvantages,such as the voluminous sludge with high moisture content,hard to dispose and recycle.The induced crystallization method is studied for removal fluorine from the wastewater containing high content of fluorine in this study.The modified calcium salt is defluorinating agent and calcium fluoride is crystal seed.This method overcomes many disadvantages mentioned above which exists in chemical precipitation process.The process of removing fluorine from wastewater was simulated in order to understand the effect of the induced crystallization method by using the modified calcium salt on removing fluorine in this thesis.The optimal process conditions are temperature 25 ?,time 60 min,pH 6?10,crystal seed 6?8g/L,the amount of the residual calcium is 300mg/L.From the experiments,it has been found that increasing the concentrations of Mg2+,SO42-and PO43-lead to the residual fluorine increasing in the solution.The concetrations of Cl-and SiF62-have a certain effect on removing fluorine from the solution.The wastewater from some plant is used to do experiments in this study.The concentration of fluorine decreases from 769.76 mg/L to 10 mg/L,which means the wastewater can be discharged.The main component of the fluoride-containing slag is calcium fluoride.The content of calcium fluoride is over 95%.Due to the composition and the low water content,the fluoride-containing slag obtained from the fluoride removal process could be used as the seed or be sale as the product.The results indicate that the induced crystallization technology by using the modified calcium salt has a good effect on removing fluorine from waste water.When it is compared with other fluoride removal methods,it has some advantages,including easy operation,shorter process,low cost,good treatment effect.Moreover,fluorine can be recycled make this process have a good prospect in industrial application.