Study of preparation of zirconium loaded flyash and its effect for adsorption of fluoride in wastewater of coking plant

In order to explore the capacity of zirconium-modified flyash for adsorption of fluoride in wastewater of coking plant, the flyash of a coal-fired power plant in Hunan Province is taken as the object of study.The flyash is made to carry active zirconium hydroxide through surface modification by using hot alkaline and zirconium loading processes to enhance the capacity of flyash for adsorption of fluoride in the wastewater of a coking plant.As evidenced by test result, a best fluoride removal result can be expected at a Zr(IV)/flyash mass ratio of 1∶30 and a surface modification time of 60 minutes.For adsorption of fluoride in simulated wastewater containing 100mg/L of fluoride with the flyash, the equilibrium adsorption capacity is 18.60mg/g with a fluoride removal rate up to 93%.Adsorption thermodynamics study shows that the capacity is consistent with the Langmuir modeling result with a calculated maximum staturation capacity being as high as 50.36 mg/g, three times higher than that of the flyash in its originally untreated state.