Defluorination of Water by the “Inline” Coagulation–Ultrafiltration Method

Background. The various methods used for water defluorination (sedimentation, coagulation, ion exchange, etc.) cannot be used at high (>10 mg/dm3) content of fluorides. Therefore, the development of new high-performance methods of water purification from ions of F- is extremely important and relevant. Objective. Determination of the effectiveness of the process of water defluorination by “inline” coagulation–UF method. Methods. Dosing of coagulant into a stream of “inline” water, followed by using the ultrafiltration method with domestic tubular ceramic membranes from clay minerals. Results. The influence of duration of process, the initial concentration of the ions F- and Fе3+ in solution and its pH on the concentration of ions F- in permeate and specific performance of the Jv of the membrane has been investigated. It is shown that for water defluorination with the concentration of the starting solution F- value of 5.0–10.5 mg/dm3 and Fе3+ = 17,0–32,0 mg/dm3, with рН 3,0–3,5 and P = 1.0 MPa the concentration of ions F- and Fе3+ permeate was at the level of their MCL in drinking water. Conclusions. The high efficiency of water defluorination by “inline” coagulation–UF method using coagulant FeCl3∙6H2O has been shown. The parameters of the specified process by which water purification from ions of F- and Fe3+ to norms of maximum permissible concentration in drinking water are determined. The expediency of using the method for water defluorination in an acidic medium followed by its neutralization is justified.