Fixation and stabilization of lead in contaminated soil and solid waste
AssigneeMAECORP Incorporated
InventorsDhiraj Pal, Karl Yost
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Abstract
A two-step treatment process is disclosed for application of lead-toxic wastes to fixate and stabilize leachable lead contained therein. The process employs the use of a sulfate compound, such as gypsum, in a first step; and a phosphate reagent, such as phosphoric acid, in a second step. After thorough mixing and curing, a substantially solid end product is formed in which the lead is chemically fixed and remains in stabilized form for indefinite geologic periods. The process reduces Toxicity Characteristic Leaching Procedure lead levels below the regulatory threshold of 5 mg/l as required by the U.S. Environmental Protection Agency. The waste also beneficially undergoes volume reduction in a short curing time, and is applicable in a variety of situations.
Claims20
A treatment process for treating lead-toxic solid wastes to stabilize leachable lead contained therein, said process comprising the steps of:
- mixing a solid waste containing leachable lead with a sulfate compound having at least one sulfate ion for reacting with said leachable lead to produce a first mixture, said first mixture containing a substantially insoluble lead compound or mineral species;
- and
- mixing said first mixture with a phosphate reagent having at least one phosphate ion for reacting with leachable lead remaining said first mixture to produce a second mixture, said second mixture containing a substantially insoluble lead compound or mineral species;
- curing said second mixture for a period
- such that the material so treated is substantially solid in form at the end of curing, the material passes the paint filter test, TCLP lead levels are decreased below 5.0 mg/l, the volume of said solid waste is reduced as a result of treatment and curing, and no secondary waste streams are generated.
A treatment process for treating solid wastes to stabilize leachable lead contained therein, said process comprising the steps of:
- mixing a solid waste containing leachable lead with gypsum to produce a first mixture, said first mixture containing a substantially insoluble lead compound of mineral species;
- and
- mixing said first mixture with phosphoric acid for reacting with leachable lead remaining in said first mixture to produce a second mixture, said second mixture containing a substantially insoluble lead compound or mineral species;
- curing said second mixture for a period
- such that the material so treated is substantially solid in form at the end of curing, the material passes the paint filter test, TCLP lead levels are decreased below 5.0 mg/l, the volume of said solid waste is reduced as a result of treatment and curing, and no secondary waste streams are generated.
Dependencies are inferred from the claim text.