关键词: 高浓度硫酸钠溶液, 深度净化, 氟离子, 聚氯化铝, 响应曲面法

Abstract:

It was proposed to use polyaluminum chloride（PAC，similarly hereinafter） for deep purification of F^- in high concentration sodium sulfate solution.The effects of molar ratio of aluminum to fluoride，reaction endpoint pH and flocculation time on the removal rate of F^- were studied.The regression equation model obtained through the response surface method was used to predict the optimal experimental condition parameters for deep purification of F^-.At the same time，the obtained response surface map and contour map were used to intuitively reflect the influence of various factors on the removal rate of fluoride ions and the strength of their interaction.The significant factors affecting the removal rate of fluoride ions from high to low were endpoint pH，molar ratio of aluminum to fluorine，and flocculation time.The response surface methodology was used to optimize the mathematical model established by PAC to remove fluoride ions from high concentration sodium sulfate solution.The fitting value was highly consistent with the validation test results.The stock solution contained 292.85 g/L of salt and 70.58 mg/L of fluoride ions.The optimal process parameters of model optimization：the molar ratio of aluminum to fluoride was 15.6，the endpoint pH was 7.6，and the flocculation time was 50 min.The removal rate of fluoride ions was 94.03%，which was verified by three tests.It was found that the actual average removal rate of fluoride ions was 93.56% after multiple experimental verifications.The difference between the removal rate of fluoride ions and the predicted value of the model was 0.47%.The fluoride ions in the liquid could be reduced from 70.58 mg/L to 4.55 mg/L after purification，indicating high accuracy and reliability of the model optimization conditions.

Key words: high concentration sodium sulfate solution, deep purification, fluoride ion, aluminium chlorohydrate, response surface methodology