Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group viib metal
Reexamination Certificate
1998-04-01
2001-01-09
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group viib metal
Reexamination Certificate
active
06171562
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related to a process for the extraction and elimination of deleterious material present in natural manganese dioxide (NMD), as well as in natural concentrated manganese dioxide obtained by said process.
2. Description of the Related Art
Natural manganese dioxide (NMD) is frequently used in the manufacture of electrochemical batteries. However, NMD normally contains a very high content of deleterious material, such as copper, nickel, cobalt, iron, aluminum, potassium, and the like, which is highly undesirable to manufacturers of such electrochemical batteries. The deleterious material, mainly the heavy metals, drastically reduces the discharging performance of the electrochemical batteries, while significantly increasing the corrosion thereof.
The process of hydrochloric acid (HCl) leaching of manganese ore has been described in several documents, especially in documents published in the late 1960's and early 1970's, when a large surplus of HCl derived from polyvinyl chloride (PVC) processing was available. Such leaching processes were based on the manganese ore being treated with an HCl solution under certain reaction conditions, especially temperature and HCl concentration. Examples of patents, which disclose such process are AU Patent 435 309, U.S. Pat. No. 3,437,345, published Application DE 2 164 799, U.S. Pat. No.3,770,868, and U.S. Pat. No. 4,872,909. Other references similarly processes for leaching of manganese dioxide, such as “A New Process for the Production of Synthetic Battery grade Manganese Dioxide”, National Chemical Engineering Conference, Surfers Paradise, Queensland, (1974). All such references, which represent the state of the art processes for the leaching of manganese dioxide, denote that the interesting phase of such process is the liquid i.e., the leaching phase. Therefore, the concentrate or solid residue of non-leached manganese dioxide in such process has a high concentration of deleterious material and, as a consequence, a low concentration of MnO
2
, which, as mentioned above, is highly undesirable. There is no known process for the leaching of NMD ore which supplies, in industrial quantities, a concentrate of manganese dioxide having acceptable levels of deleterious material and which retains its original crystalline structure.
OBJECTS OF THE INVENTION
Therefore, the first object of this invention is to provide a process for the extraction and elimination of deleterious material from the NMD ore, performed in a convenient way and which eliminates the drawbacks and inconveniences of the prior technique.
Another object of this invention is to provide a process for the extraction and elimination of deleterious material, such as Cu, Ni, Co, Fe, Al, K and the like from NMD.
Another object of this invention is to provide a process to obtain a concentrate of NMD with a low level of deleterious material and, as a consequence, a high level of manganese dioxide, with minimum dissolution of the manganese dioxide, to retain the original crystalline structure, which is highly electroactive in electrochemical batteries.
Still another object of this invention is to provide a concentrate of manganese dioxide having a content of deleterious material which is so low that it may be highly desired by the manufacturers of electrochemical batteries.
Another object of this invention is to provide a concentrate of manganese dioxide which reduces the amount of corrosion in electrochemical batteries.
SUMMARY OF THE INVENTION
Following a first embodiment this invention includes, basically, the following stages:
a) feeding a reactor with an HCl and water mixture having an HCl concentration within the range from about 9% to 25% w/w while stirring and heating;
b) maintaining the temperature of the mixture in the reactor at about 80 to 95° C.;
c) feeding reactor with an amount of crushed NMD ore, such to provide a concentration of the reaction pulp from about 10% to 40%, depending upon the HCl concentration; and
d) leaching to produce a leaching reaction of the NMD ore with HCl, for a period of about 10 to 60 minutes.
Following a second embodiment of this invention, through the above-described process, a concentrate of manganese dioxide is obtained, in which the MnO
2
content ranges from about to 85% to 95%.
DETAILED DESCRIPTION OF THE INVENTION
Following the terms of this invention, exploratory leaching tests were performed with NMD ore using HCl, to check for the existence of preferred solubility levels of deleterious materials, such as Cu, Ni, Co, Fe, Al, K and the like, relative to the original MnO
2
. The tests considered variable values such as temperature, HCl concentration, reaction time and pulp density. In the tests, all such parameters were found to be of importance.
The preferred solubilization of the different deleterious components in the original MnO
2
was determined to be as of equal importance, considering that the concentration of the mineral by the leaching process is determined by the solubility of the impurities, and not the mineral ore. In this case, the mineral ore is MnO
2
, in the form of “nsutita”.
With the statistical results on hand, optimization tests were programmed. In this phase of the development, the effect performed by four independent variable values was checked: HCl concentration, temperature, leaching time and pulp density, which change at the same time, in respect to the dependent variable values, MnO
2
recovery, MnO
2
content and the content of deleterious materials. Surprisingly, it was noticed that the effects provided by the different independent variables, HCl concentration, temperature, leaching time and pulp density in respect to the dependent variables, recovery of MnO
2
, content of MnO
2
and the content of deleterious materials, are important and highly beneficial in terms of final purity of the concentrate of manganese dioxide. In the process of this invention, the concentrate is the undissolved ore, with the leaching liquor being kept for future treatment. The importance of HCl concentration and of temperature in respect of the other variables became especially clear. It was shown, as an example, that the minimum HCl concentration should not be less than about 9% w/w. It was shown further that the minimum reaction temperature may not be lower than about 80° C. nor higher than about 95° C. It was noticed that if the reaction temperature is less than about 80° C., the process becomes uneconomical and that if the temperature is higher than about 95° C., it becomes too difficult to use HCl, due to its vapor pressure and oxidizing power.
Therefore, following the terms of this invention, a process is established for the extraction and elimination of deleterious material from the original MnO
2
, such as Cu, Ni, Co, Fe, Al, K and the like, by the preferential solubility thereof in an HCl solution which ranges from about 9% to 25% w/w in a reactor. The quantity of NMD ore/quantity of HCl rate is such that a pulp should be obtained with a density from about 10% to 40%. The density of the pulp is determined by the concentration of HCl used in the solution. The pulp is then reacted for about 10 to 60 minutes by leaching at a temperature of about 80° C. to 95° C. The reaction time is determined by the extraction level of the deleterious material and by the desired recovery of MnO
2
. One skilled in the art will know how to easily select the conditions under which the reaction will be performed, based upon the expected result. After the reaction, the resulting pulp is filtered and the resulting cake, which is the concentrate of manganese dioxide, is taken for drying and the filtrate, which is the hydrochloric acid liquor, is recycled to the beginning of the process.
The successive reutilization of the hydrochloric acid liquor increases the concentration of heavy metals, which is fundamental for its later extraction by chemical and/or electrochemical means. Besides, the process results in a higher solubility of the heavy metals relative to MnO
2
. However
Amaral Josue Coelho
Paixao Jose Marcio Matta Machado
Bos Steven
Companhia Vale Do Rio Doce
Helfgott & Karas P.C.
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