Method for treating fluoric containing drainage

Abstract

The invention provides a treatment method for fluoride-containing wasterwater, which can inhibit precipitation of fine calcium fluoride to get stable treated water and produce sludge with low miosture content in less procedures. The treatment method includes: a reaction procedure of adding calcium compound into the fluoride-containing wasterwater to produce insoluble with calcium fluoride, a separation procedure of performing solid-liquid separation between the sludge with calcium fluoride insoluble and separation water, a sludge return procedure of returning the separated sludge used as returning sludge to the reaction procedure. In the reaction procedure, calcium compound, the equivalent of which is less than the equivalent of the fluoride compound ions, is added to the reaction groove of the first section by using two series connected reaction grooves, to ensure that the density of the calcium ions residues is more than 1 milligram per litre and less than 5 milligram per litre, andthe density of the fluoride compound ions residues is less than 80 milligram per litre; calcuim compound, the equivalent of which is more than the equivalent of the fluoride compound residues in the reaction groove of the first section, is added to the reaction groove of the second section, to ensure that the density of the fluoride ions is less than 15 milligram per litre.

Description

technical field [0001] The present invention relates to adding calcium compounds such as calcium chloride and calcium hydroxide to fluorine-containing wastewater to make fluorine into insoluble calcium fluoride (CaF 2 ) for solid-liquid separation. In particular, the present invention relates to a method for treating fluorine-containing wastewater by making calcium compounds effectively act on fluorine in wastewater to obtain treated water with excellent water quality and generate sludge with low water content. Background technique [0002] Examples of fluorine-containing water containing fluoride ions include fluorine-containing wastewater discharged from the silicon wafer manufacturing process, pickling wastewater discharged from the stainless steel sheet manufacturing process, wastewater from aluminum surface treatment, and hydrofluoric acid production in the manufacture of semiconductor components. Waste water, waste water from fertilizer manufacturing, waste water from...

AI Technical Summary

Problems solved by technology

[0006] When calcium hydroxide is used as a reagent to make fluorine insoluble, and also as a pH regulator to adjust the pH to 10-11, sometimes calcium hydroxide with an equivalent of fluoride ion or more is added, and fine calcium fluoride is precipitated. Leakage in the treated water, resulting in instability of the treated water quality

In addition, if the generated fine calcium fluoride is coagulated and precipitated using a coagulant such as a polymer in order to obtain treated water of excellent water quality, the moisture content of the generated sludge will increase and the amount of waste will increase.

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