Removement of Selenium and Fluorine from Effluents with High Concentration Chloride Ions

摘要

An effluent standard is becoming severe from a viewpoint of environmental conservation in recent years. Perceiving to reduce selenium (Se(Vi)) that it is said to be difficulty, the examination was conducted for removal of selenium in solution with the high concentration of chloride ions which made the removal more difficult. Moreover, the experiment was carried out to remove selenium and fluorine which behaved as anion. The results can be summarized as follows:1) SeO_3~(2-) (IV) ions could be removed easily even in the solution with the high concentration of chloride ions. In the case of SeO_4~(2-) (VI), it was needed to be reduced to SeO_3~(2-). The quantity of reducing agent for solution including much amount of chloride ions was required as much as thousand times of amount of SeO_4~(2-).2) FeSO_4 centre dot 7H_2O was desirable for a reducing agent for the solution of high chloride concentration. FeCl_3 was needed to decrease the concentration of Fe. Furthermore, Ca(OH)_2 was suited to adjust pH rather than NaOH. Ca(OH)_2 improved the efficiency of both filtration and removal of SeO_4~(2-).3) It was possible to remove fluorine by using H_3PO_4 and to remove selenium with FeSO_4 continuously. Furthermore, the reaction of both was carried out under the same condition, pH 10. Therefore, it was found that it is an easy processing method to control pH.