公开(公告)号：US11286181B2

公开(公告)日：2022-03-29

申请号：US16347431

申请日：2017-09-12

Applicant: KURITA WATER INDUSTRIES LTD.

Inventor： Shuhei Izawa ,  Ippei Tanaka

IPC: C02F1/52 ,  C02F1/58 ,  C02F1/62 ,  C02F9/00 ,  C02F11/122 ,  C02F101/10 ,  C02F101/14 ,  C02F101/20 ,  C02F103/16 ,  C02F1/00

Abstract: A calcium fluoride precipitation inhibitor is added to waste water containing sulfuric acid, fluorine (fluoride ions and hydrogen fluoride) and heavy metal ions to generate pretreated water. A calcium compound is added to the pretreated water to generate a first insolubilized product at a pH of less than 5, followed by solid-liquid separation. A calcium compound is added to a first separated water after the solid-liquid separation to generate a second insolubilized product at a pH of 3 to 7 (provided that the pH is a pH higher than in the first reaction step), followed by solid-liquid separation. An alkali is added to a second separated water after the solid-liquid separation to give a pH of 8 or more, thereby generating a third insolubilized product, followed by solid-liquid separation.