Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1996-07-17
1998-09-01
Hruskoci, Peter A.
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
210716, 210728, 252175, 252181, 423122, 423132, 423140, 4231503, 423DIG2, C02F 156
Patent
active
058007164
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the treatment of acidic liquors, to a process for the production of valuable water treatment agents and other valuable commercial products thereby and to the agents or products so produced.
Aqueous acidic liquors containing dissolved aluminium and/or iron compounds are produced on a large scale, mainly as waste products, in various industries. An example of this is the liquor produced from the treatment of aluminosiliceous or aluminoferrosiliceous minerals with acids such as, for example, sulphuric acid or hydrochloric acid, to increase the surface area of the minerals and to activate them for various uses, for example for edible oil purification or for paper coating applications. The acidic liquor so produced contains a substantial proportion of dissolved aluminium and/or iron compounds. This liquor may be neutralized with lime to produce a cake or slurry for disposal to land-fill. Another example is acidic mine drainage water which may contain a substantial proportion of dissolved iron compounds and may likewise be neutralized with lime to produce a slurry which is usually aerated to convert the iron to the ferric form and allowed to settle to produce a solid waste product for disposal. Waste pickling liquors also contain substantial quantities of dissolved iron compounds. The disposal of such waste products represents a considerable expense and is increasingly considered to be ecologically undesirable. It would be of considerable benefit to industry and to the environment to provide means for utilising these and other similar liquors as raw materials for further processing.
The present invention provides a process for the treatment of aqueous acidic liquors containing dissolved aluminium and/or iron compounds to produce an aluminium and/or iron sulfate water-treatment product, the process being characterized by the combination of steps comprising contacting the liquor with a basic material capable of reacting with the dissolved aluminium and/or iron compounds to precipitate aluminium and/or iron values, separating the precipitate in the form of a cake or slurry from the remaining liquor, treating the cake or slurry with sulphuric acid to re-dissolve aluminium and/or iron values and to produce a solution of aluminium and/or iron sulfate and separating suspended solid matter from the solution.
The acidic liquor to be treated according to the invention is very suitably derived from the acid treatment of aluminosiliceous or aluminoferrosiliceous minerals such as smectites, kaolinites, attapulgites, sepiolites or the like and particularly, within the smectites, montmorillonites. In this case the water treatment product is an aluminium sulphate or an aluminium-iron sulphate. In the case of acidic liquors derived from purely ferrous sources, such as the acidic mine drainage liquors referred to above, which may contain up to about 1000 mg/l Fe and up to about 4000 mg/l sulphate, or more, an iron sulphate water treatment product is produced. The invention will be described hereafter with particular reference to the treatment of liquors derived from the acid treatment of montmorillonite clay minerals. However, the description is to be modified as required to relate to the treatment of liquors derived from the acid treatment of other materials indicated above, or to the treatment of other acidic aluminium and/or iron containing liquors, unless the context requires otherwise. The acidic liquor may have a pH below 4 but more usually below 3, for example from 0.5 to 3.
The term "liquor" is used herein in a practical sense to include reference to liquid plant or mine effluent including any suspended solid matter which may be present.
The montmorillonite clay minerals, which term is used to include bentonites, are layered minerals composed of an octahedrally coordinated aluminium layer connected by the sharing of oxygen atoms to two adjacent tetrahedrally coordinated silicon layers. The aluminium in the octahedral layer is partially substituted by iron and may also be substituted
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Clarke Neil
Newton John Harris
Hruskoci Peter A.
Laporte Industries Limited
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