Method for treating metal-contaminated water and soil
First Claim
1. A method of removing metal contaminants from water, comprising the steps of:
- (a) dispersing lignin derivatives in said metal-contaminated water;
(b) dispersing a coagulant in the mixture formed in step (a);
(c) causing the formation of a floc in the mixture formed in step (b);
(d) allowing said floc to coagulate and form a sludge; and
(e) separating said sludge from an aqueous filtrate.
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Abstract
A method for removing metal contaminants from water uses lignin derivatives, such as lignosulfonates and kraft lignin, a coagulant, such as a metal salt, and a pH-increasing composition. The lignin derivative is dispersed in the contaminated water, the coagulant is added and the pH is adjusted as required to cause flocculation. A sludge is formed that contains the metals and that is separated from the treated water by filtration. Related methods are used to reduce the leachable metal content of contaminated soils. The invention also provides a composition for stabilizing the metal contaminants in soil, comprising lignin derivatives, a coagulant and a composition for increasing the pH. The mixture is blended with the contaminated soil, reducing its leachable metal content.
40 Citations
23 Claims
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1. A method of removing metal contaminants from water, comprising the steps of:
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(a) dispersing lignin derivatives in said metal-contaminated water;
(b) dispersing a coagulant in the mixture formed in step (a);
(c) causing the formation of a floc in the mixture formed in step (b);
(d) allowing said floc to coagulate and form a sludge; and
(e) separating said sludge from an aqueous filtrate. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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2. A method of removing metal contaminants from water, comprising the steps of:
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(a) dispersing lignin derivatives in said metal-contaminated water;
(b) dispersing a coagulant in the mixture formed in step (a);
(c) causing the formation of a floc in the mixture formed in step (b); and
(d) separating said floc from an aqueous filtrate.
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23. A method of removing metal contaminants from water, comprising the steps of:
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(a) dispersing lignin derivatives in said metal-contaminated water, said lignin derivatives comprising one or more of lignosulfonates and kraft lignin. (b) dispersing ferric chloride in the mixture formed in step (a), the mass ratio of the lignin derivatives to the ferric chloride being at least 1;
1;
(c) adjusting the pH of the mixture formed in step (b) to a pH in the range of 4-10, causing the formation of a floc;
(d) allowing said floc to settle, resulting in a liquid and a ferric sludge; and
(e) separating said sludge from said liquid.
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Specification