Methods for the treatment of metallic particles such as heavy metal particles and objects contaminated with the metallic particles. For the treatment of objects contaminated with the metallic particles, a stabilizing composition may be applied to the object with or without a fixation agent. For the treatment of free-flowing metallic particles, an agglomeration agent may be used with or without a stabilizing agent.

A reagent system for treating heavy metal-contaminated materials is provided and includes an oxidizer, a soluble phosphate, and an alkaline hydroxide source, such as a caustic soda or lime. A method of treating mine waste bearing one or more heavy metals is also provided and includes the step of admixing a reagent system with heavy metal-containing material to preferentially reduce the leachability of heavy metals and form precipitates and complexes of low metal solubility that remain stable within the host solid matrix for long durations in acidic and abrasive conditions.

The present invention discloses a method for detoxifying chromium slag by using high sulfur coal. The method includes: sieving chromium slag into coarse-grained chromium slag and fine-grained chromium slag, air-drying and crushing both the coarse-grained chromium slag and the fine-grained chromium slag; separately mixing the crushed coarse-grained chromium slag and fine-grained chromium slag with the crushed high sulfur coal uniformly; adjusting pH values of a coarse-grained slag mixture and a fine-grained slag mixture to 8.0-11.0 and moisture content thereof to 12%-18%; conducting reduction on the treated coarse-grained slag mixture and fine-grained slag mixture, where the reduction temperature of the fine-grained slag mixture is 500-700 C., the reduction time of the fine-grained slag mixture is 10-30 min, the reduction temperature of the coarse-grained slag mixture is 800-1000 C., the reduction time of the coarse-grained slag mixture is 10-30 min; after the reduction, conducting water quenching, and discharging the product.

An adsorbent and photocatalytic decontamination gel consisting of a colloidal solution comprising, preferably consisting of: 8% to 30% by weight, preferably 10% to 30% by weight, more preferably 15% to 20% by weight, better still 15% to 20% by weight, the value 15% being excluded, even better still 16% to 20% by weight, for example 20% by weight of TiO.sub.2, optionally doped, relative to the weight of the gel; optionally 0.01% to 10% by weight, preferably 0.1% to 5% by weight, relative to the weight of the gel, of at least one dye and/or of at least one pigment; optionally 0.1% to 2% by weight, relative to the weight of the gel, of at least one surfactant; optionally 0.05% to 5% by weight, preferably 0.05% to 2% by weight, relative to the weight of the gel, of at least one superabsorbent polymer; and the balance of solvent.

Provided is a hexavalent chromium treatment agent capable of penetrating inside of a leather and capable of reducing not only hexavalent chromium present in the vicinity of the surface of the leather but also hexavalent chromium present inside the leather into trivalent chromium. The hexavalent chromium treatment agent of the present invention comprises a hexavalent chromium-reducing compound capable of reducing hexavalent chromium into trivalent chromium, a nonionic surfactant, and an aqueous solvent. The hexavalent chromium-reducing compound preferably comprises an organic compound (A) that has a specific structure capable of acting to reduce hexavalent chromium into trivalent chromium, that has a hydroxyphenyl group, and that has no aldehyde groups and no carboxyl groups.

A method of treating, stabilizing, precipitating, or otherwise removing heavy metal ions contained in a contaminated media, which method includes: providing a sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance; contacting said contaminated media containing heavy metal ions with the sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance; and allowing the contaminated media containing the heavy metal ions to react with said sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance, such that the contaminated media containing heavy metal ions form single or mixed metal-sulfide precipitates or co-precipitates.

A process is disclosed for treating a Bayer process waste comprising a slurry containing bauxite residue and dissolved aluminum. The process comprises supplying the waste to a settling area to cause the bauxite residue to settle out of the slurry, thereby producing a supernatant liquor. The process further comprises neutralizing the supernatant liquor with a solution containing magnesium and calcium to produce a neutralized slurry containing precipitated hydrotalcites and thickening the neutralized slurry to produce a clarified effluent and a compacted slurry containing the precipitated hydrotalcites, part of said compacted slurry being recirculated to the supernatant liquor to be neutralized and/or directly to the neutralizing step. The clarified effluent and the compacted slurry are disposed of separately. Also disclosed is a plant for treating a Bayer process waste.

A process for immobilizing a mercury-containing waste, which comprises: stabilizing the mercury of the waste by precipitating the mercury as mercury (II) sulfide; thenencapsulating the waste by cementation, the cementation comprising coating the waste in a cement paste obtained by mixing a composition comprising a powder of at least one binder chosen from hydraulic cements, alkali-activated cements and acid-activated cements, with an aqueous mixing solution, then hardening the cement paste; and which is characterized in that the precipitation of the mercury as mercury (II) sulfide is obtained by reacting the mercury with a thiosulfate in a basic aqueous medium, while stirring and in the presence of a sulfide of an alkali metal, the molar ratio of the thiosulfate to the mercury being at least equal to 1. Applications: immobilization of any mercury-containing waste regardless of the origin thereof and, in particular, of mercury-containing waste from nuclear facilities.

A polymeric polysulfide is disclosed. The polymeric polysulfide is formed by reacting a fatty acid composition comprising at least one unsaturated fatty acid or derivative thereof with sulfur, at a weight ratio between 9:1 and 1:9, under inverse vulcanisation conditions to produce a polymeric polysulfide wherein at least 50% of the fatty acids or derivatives thereof in the fatty acid composition are unsaturated.

Methods and systems for bioremediation of heavy metal contaminants in waste materials (e.g., sludge and combustion wastes from a coal-fired power plant). The systems described in the present application include at least one waste treatment unit (e.g., a flue gas cleaner or a waste lagoon) that includes one or more selected bacterial strains disposed therein consume and/or reclaim at least a portion of the heavy metal in the combustion wastes. Methods include inoculating a waste treatment unit with one or more selected bacteria that consume and/or reclaim at least a portion of the heavy metal in the combustion wastes. Methods may include periodic reinoculation of the waste treatment unit with fresh bacteria and period recovery of the bacteria from the waste treatment unit.