Process for treating a sludge or drainage containing chromium (VI) compounds with a solidifying agent
AssigneeOnoda Cement Co., Ltd.
InventorsHiroshi Uchikawa, Masao Shimoda
Life of this patent
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Abstract
This invention relates to a process for treating a sludge or a drainage containing chromium (VI) compounds with a calcium haloaluminate bearing rapid hardening cement in a short period of time. The solidified material developes high strength and has shown a extremely Cr.sup.6+ fixation.
Claims9
A process for solidifying an industrial waste sludge containing chromium (VI) compounds, comprising mixing the sludge and a rapid hardening cement consisting of from 5 to 60% by weight of 11 CaO.multidot.7Al.sub.2 O.sub.3 .multidot.CaX.sub.2, where X is halogen;
- and 3 CaOSiO.sub.2 solid solution, 2 CaO.multidot. Fe.sub.2 O.sub.3 -6 CaO.multidot.2 Al.sub.2 O.sub.3 .multidot. Fe.sub.2 O.sub.3 iron solid solution and a material selected from the group consisting of anhydrous gypsum and a mixture of anhydrous gypsum and hemihydrate gypsum, in an amount such that the weight ratio of Al.sub.2 O.sub.3 /SO.sub.3 in the cement is 0.4 to 1.8 based on SO.sub.3.
A process for solidifying a sludge containing chromium (VI) compounds obtained from the waste from the recovery of chromium from chromium ore, or the waste discharged from a chromium plating factory or from a leather tanning factory, said process comprising mixing the sludge and a rapid hardening cement consisting of from 5-60% by weight of 11CaO.multidot.7Al.sub.2 O.sub.3 .multidot. CaX.sub.2, where X is halogen;
- and 3 CaO.multidot. SiO.sub.2 solid solution, 2 CaOSiO.sub.2 solid solution 2 CaO.multidot. Fe.sub.2 O.sub.3 - 6 CaO.multidot.2 Al.sub.2 O.sub.3 .multidot. Fe.sub.2 O.sub.3 iron solution;
- and a material selected from the group consisting of anhydrous gypsum and a mixture of anhydrous gypsum and hemihydrate gypsum, in an amount such that the weight ratio of Al.sub.2 O.sub.3 /SO.sub.3 in the cement is 0.4 to 1.8 based on SO.sub.3.
The process of claim 4, wherein the boric acid and its salt, bicarbonates, silicic acid salts, silicofluorides, quick lime, hydrated lime, and phosphoric acid salts recited in claim 14 are added to the rapid hardening cement in amounts less than 3% by weight thereof.
The process of claim 4, wherein the organic carboxylic acids, saccharides, lignin sulfonic acid salts, higher alcohol esters of sulfuric acid and alkaryl sulfonic acid salts recited in claim 14 are added to the rapid hardening cement in amounts less than 3 percent by weight thereof.
Dependencies are inferred from the claim text.