No abstract

No abstract

REMOVAL OF FLUORIDE IONS BY BATCH ELECTRODIALYSIS Suitability of conventional batch electrodialysis to fluoride removal from aqueous solutions has been investigated. The experiments were conducted with the use of laboratory installation PCCell BED-1 System at a constant current density (1.56 or 2.34 mA/cm 2). The influence of initial fluoride and salt (NaCl) concentration, as well as the presence of organic matter on the process performance was studied. It was found that the separation efficiency increased upon decrease of initial fluoride content in model solutions. Permissible final concentration of fluorides in the product water (1.5 mg/dm 3) was obtained for experiments with solutions of initial fluoride concentration equal to 5 mg F-/dm 3 and 10 mg F-/dm 3. The presence of humic acids in fluoride solutions subjected to electrodialysis treatment has no adverse effect on the defluorization and desalination efficiency. The calculated electrical energy demand depended on composition of fluoride solution and varied from 0.121 to 0.895 kWh/m 3 .

No abstract

No abstract

Fluorine is a chemical element with the symbol F. Many fluorine compounds are very water-soluble. In aqueous environments it only occurs as fluoride. The content of Fions in natural surface water is usually not higher than 0.3 mg/dm 3 [1, 2]. According to WHO guidelines the permissible concentration in drinking water cannot be higher than 1.5 mg/dm 3. There are two sources of fluoride in the environment-natural

The usability of surfactant-aided ultrafiltration for removal of fluoride ions from aqueous solutions has been investigated. The experiments were conducted with the use of cellulose and polyethersulfone membranes. Fluoride solutions containing 10 and 100 mg F-/dm 3 and cationic surfactants: octadecylamine acetate (ODA) and hexadecylpyridium chloride (CPC) were used in the experiments. The concentration of surfactants amounted to 320-960 mg/dm 3. Ultrafiltration process was run under a transmembrane pressure of 0.2 MPa. In the course of experiments, the effects of initial fluoride concentration, surfactant concentration and membrane type on the fluoride retention coefficient as well as the permeate flux were studied. It was found that the increase of the surfactant concentration effected in improvement of the separation efficiency. On contrary, the permeate flux decreased upon increase of the surfactant concentration. The process efficiency was also strongly influenced by the membrane and surfactant type. The permissible concentration of fluoride in the final product (below 1.5 mg F-/dm 3) was obtained for the test with initial solutions containing 10 mg F-/dm 3 , polyethersulfone membrane and CPC concentration equal to 644 and 966 mg/dm 3 .

Abstract.Water contamination by fluoride is a common problem present in many regions of the world.