Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1989-07-24
1992-06-16
Andrews, Melvyn J.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
423112, 423DIG14, C01G 1500, C25C 122
Patent
active
051222418
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the recovery of gallium contained in various raw materials or secondary raw materials together with impurities such as the metalloids of Group V of the periodic table of the elements.
More particularly it relates to the treatment either of solutions of gallium chloride, or of materials containing gallium in the wholly or partially reduced state.
As an example of reduced materials of this kind containing gallium may be mentioned gallium metal and the phosphides, arsenides, nitrides and antimonides of this metal.
Gallium, whether present in primary or secondary raw materials, is often combined with Group V elements: thus, the dust from phosphorus plants, the residues from processing of gallium arsenide and gallium phosphide and so on.
For economic reasons, it is preferable that the processes for the treatment of these products or of these solutions employ techniques of the chloride route already partially perfected for the primary recovery of gallium where impurities of this kind do not occur. In general these techniques employ trialkyl phosphates, particularly the most common of these tributyl phosphate, currently designated by its letter symbol in English TBP, which will serve as a paradigm for this family (cf. Science and Technology of tributyl phosphate, volume 2, pages 97-99, RC Press Inc).
An initial difficulty lies in the presence, among the materials containing gallium, of other elements having similar chemical properties such as, for example, indium and more generally metals having volatile suboxides. Furthermore, the Group V elements often have properties similar to those of III compounds, which makes separation difficult.
According to the conventional techniques for the recovery of gallium, this element is brought into hydrochloric acid solution and is recovered by liquid-liquid extraction of the gallium trichloride formed by means of liposoluble complexing agents of Lewis acids, agents such as amines and neutral organophosphorus compounds of the trioctylphosphine oxide (TOPO) and tributyl phosphate (TBP) type.
A second difficulty in the treatment of these secondary raw materials lies in the particularly pyrophoric and inflammable nature of these products and of the gases which they produce from their reaction with water. Thus in aqueous phases gallium phosphide produces phosphines, compounds which are very inflammable, certain of which would be the source of the combustion of natural evolutions of methane and would cause what is commonly called "will-o'-the-wisps".
It is also advisable to mention that the hydrogenous compounds of arsenic, antimony and phosphorus are highly toxic.
One of the objects of the present invention is to provide a process derived from the processes above but adapted to the particular problems of materials containing gallium mentioned above.
Thus, one of the objects of the present invention is to provide a process which enables, starting from the same extractive reactants as previously used, a good separation of gallium in the form of the chloride to be ensured from the Group V metalloids or from the impurities which are likely to be present in wastes of gallium III-V compounds or in other sources of supply of materials containing gallium. Among these impurities may be mentioned indium and antimony.
These objects as well as others which will appear subsequently are achieved by means of a process of hydrometallurgical treatment of a solution of materials containing gallium comprising in addition at least one metalloid from Group V of the periodic table of the elements, characterized in that it comprises the following steps: solution to be extracted (for example obtained from step a) described below by addition of hydrochloric acid and an alkali metal chloride or an alkaline earth metal chloride; least one neutral pentavalent phosphorus compound having a phosphorus-oxygen double bond.
Once the gallium placed in solution at a concentration preferably at least equal to 20 g/l, advantageously from 30 to 200 g/l (the zeros not being significant f
REFERENCES:
patent: 4094753 (1978-06-01), Charlton
patent: 4666575 (1987-05-01), Kubo
patent: 4759917 (1988-07-01), Coleman
patent: 4927609 (1990-05-01), Leveque et al.
Patent Abstracts of Japan, vol. 11, No. 53 (C-404)(2500), Feb. 19, 1987.
Andrews Melvyn J.
Metaleurop S.A.
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