A study on continuous and batch electrocoagulation process for fluoride removal

作者:Lu, Jun*; Tang, Qing; Wang, Zhong-Ru; Xu, Chao; Lin, Sheng-Ling
来源:Desalination and Water Treatment, 2016, 57(58): 28417-28425.
DOI:10.1080/19443994.2016.1186567

摘要

Continuous and batch electrocoagulation processes (CEC and BEC) for treating fluoride-containing solution were investigated and compared. The poor mixture and uneven distribution of flocs during BEC lead to a lower removal efficiency, when compared with CEC. Under whole range of current densities, the superiority of CEC is obvious. However, at high residence time, CEC process, which has intense back mixing has a lower removal efficiency when compared with BEC. Also it was found that even at same charge loading, the CEC differ a lot with BEC. The influences of charge loading and initial pH on CEC process were investigated with the consideration of utilization rate of electro-generated Al element. The molar ratio of F/Al in sludge presents a trend of gradual decline with the increment of charge loading. The molar ratio of (OH + F) to Al element in sludge conforms the fact that the F- is removed not only by Al(OH)(3-x)F-x(s) precipitation but also by the absorption of aluminum flocs. The influent at the condition of weak acid leads to a maximum production of aluminum hydroxide flocs along the whole electrolysis channel from inlet to outlet. This leads to the maximum removal efficiency. This was also proved by the fact that the utilization rate of Al element in sludge reaches its maximum under weak acid condition.