Filtering method of a colloidal solution
AssigneeSanyo Electric Co., Ltd.
InventorsHiroyuki Umezawa, Masahiro Iseki, Motoyuki Tsuihiji, Hirofumi Iinuma
Life of this patent
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Abstract
A filtering method is directed to a wastewater of CMP process, which includes sub-micrometer particles suspended as colloid. The wastewater is filtered by a gel membrane formed on a surface of plastic filter. A coagulant or a pH adjuster is added to the wastewater so that the sub-micrometer particles are coagulated to form the gel membrane.
Claims31
A method of filtering a colloidal solution containing colloidal substances, comprising:
- providing a first filter in the colloidal solution;
- adding an additive to the colloidal solution so that the colloidal substances are coagulated in the colloidal solution;
- sucking the colloidal solution through the first filter so that the coagulated colloidal substances are accumulated on a surface of the first filter to form a gel membrane;
- and
- filtering the colloidal solution using the gel membrane as a second filter formed on the first filter.
A method of filtering a colloidal solution containing colloidal substances, comprising:
- providing a first filter in the colloidal solution;
- adding an additive to the colloidal solution so that the colloidal substances are coagulated in the colloidal solution;
- sucking the colloidal solution through the first filter so that the coagulated colloidal substances are accumulated on a surface of the first filter to form a gel membrane;
- filtering the colloidal solution using the gel membrane as a second filter formed on the first filter until the second filter clogs;
- removing at least a part of the clogged second filter;
- and
- repeating the adding, the sucking and filtering.
A method of filtering a CMP slurry containing colloidal substances and ammonium, comprising:
- providing a first filter in the colloidal solution;
- adding hypochlorous acid or sodium hypochlorite to the CMP slurry so as to decompose the ammonium and to change pH of the CMP slurry;
- sucking the CMP slurry through the first filter so that coagulated colloidal substances are accumulated on a surface of the first filter to form a gel membrane;
- and
- filtering the CMP slurry using the gel membrane as a second filter formed on the first filter.
Dependencies are inferred from the claim text.