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US 5,296,293 AGranted
Particulate material suitable for the removal of heavy metals
AssigneeE. I. Du Pont de Nemours and Company
InventorWolfram Jobst
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AssigneeE. I. Du Pont de Nemours and Company
InventorWolfram Jobst
Estimating the term…
A particulate material suitable for the removal of heavy metals from an aqueous effluent comprises a finely ground solid encapsulated in a microporous shell of a polyvinyl chloride. The solid may be peat. The shell comprises a sufficient amount of polyvinyl chloride to utilize the adsorptive qualities of the peat while imparting structural integrity thereto. A process for making the particulate material comprises the steps of dissolving a polyvinyl chloride in an organic solvent therefor to produce a polymer solution, combining the polymer solution with a solid to produce a homogenous dispersion, forming droplets from the dispersion and contacting the droplets with water to precipitate out a particulate material comprising a finely ground solid encapsulated in a microporous shell of the polyvinyl chloride. The material may be modified after the solid is encapsulated, or the solid of the material may be modified before it is encapsulated. The material or the peat is modified with a calcium salt, such as calcium carbonate, or a sodium salt, such as sodium hydroxide. Raw peat which is modified with a calcium salt, preferably calcium carbonate, is also suitable for the removal of heavy metals from an aqueous effluent.
A particulate material suitable for the removal of heavy metals from an aqueous effluent, comprising:
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
Comprising organic material: naturally occurring macromolecular compounds, e.g. humic acids or their derivatives
Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof:…
Synthetic macromolecular compounds: obtained by reactions only involving carbon to carbon unsaturated bonds
Characterised by their physical properties: sorbent size or size distribution, e.g. particle size
Term ended 23 Dec 2011 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
1. Field of the Invention
The present invention relates to a particulate material suitable for the removal of heavy metals from an aqueous effluent, a process for making the material and a system and a method for removing heavy metals from an aqueous effluent using the particulate material. 2. Description of the Related Art
Raw wastewater generated by industry and contaminated ground water contain substantial concentrations of metal ions, oxides, cyanides and other substances. Common pre-treatment techniques of wastewater or ground water typically involve flocculation, hydroxide or sulfide precipitation, clarification and pH adjustment of the water.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate the presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.
FIG. 1 is a schematic diagram of a system used to make the particulate material according to a first, second and fourth embodiment of the present invention.
FIG. 2 is a schematic diagram of an adsorption and desorption system which uses the material of any of the first, second or third embodiments of the present invention.
Reference will now be made in detail to the present preferred embodiments of the invention as illustrated in the accompanying drawings.
In accordance with a first embodiment of the present invention, there is provided a particulate material suitable for the removal of heavy metals from an aqueous effluent. The particulate material comprises peat. Peat is a known complex organic material which is formed from the partial decomposition of sphagnum moss, sedges, or other bog plants. The principal components of peat are lignin and hemicellulose, most of which eventually break down to humic substances. The molecules of these components bear various polar functional groups, such as phenols, hydroxyls, carboxyls and ketones, which are involved in chemical bonding. Because of the polar nature of these components, peat has a large capacity for adsorbing dissolved metals and polar organic or inorganic molecules.
The peat used in the present invention is finely ground to an average size below about 30 mesh. If the peat is ground much coarser, it is more difficult to encapsulate. Also, coarse peat slows down the adsorption process. Conversely, it is not desirable to grind the peat too finely, since it is uneconomical to grind peat to a size below about 300 mesh.