Mesa Minerals Limited
Research and Development

R&D History

Mesa has had a successful track record in research and development since 1996, when the Company looked to assess whether the medium grade ferruginous manganese deposits present on its mining tenements could be utilized for the production of manganese chemicals. After an exhaustive review, a detailed bench-scale testing confirmed that the use of a modified sulfur dioxide leach had the potential to convert the then uneconomic manganese deposits into high value manganese products.

Mesa undertook extensive research into the feasibility of using the sulfur dioxide leach process route to produce alkaline grade electrolytic manganese dioxide (EMD) including the funding an $2 million Demonstration Plant programme in 2001. This programme proved to be a very successful research exercise as the range of high quality EMD products produced were tested by leading battery manufacturers and found to be equal to, or better than, existing commercially available materials. The Demonstration Plant work has been used as the foundations of Mesa’s feasibilities studies.

Mesa has since gained patent protection for its sulfur dioxide leach process and for further interdependent process innovations that involve:

  • utilising solvent extraction technology as an alternative to conventional electrolyte purification steps in alkaline EMD production; and
  • producing a valuable micro nutrient fertilizer (MNF) product from the tailings of an EMD plant which uses Mesa’s sulfur dioxide leach process.

Mesa’s ongoing commitment to R&D will ensure that the Company remains a technology leader in hydrometallurgical manganese processing. Current projects are focused upon the co-production of manganese fertilizers and manganese electrolytics, the capture and use of sulfur dioxide contained in waste gas streams, alternate generation methods for sulfur dioxide and continuing research into the crystal structures of EMD’s for use in alkaline and lithium ion batteries.

Sulfur Dioxide Leach Process

The Leach Process

While the process of sulfur dioxide leaching of manganese dioxide to produce a manganese sulfate solution has been widely reported for many years, it has not yet been successful in commercial applications of the technology due to the formation of by-products such as dithionates. These by-products have precluded its use for production of manganese electrolytic products such as EMD or electrolytic manganese metal (EMM) and for the production of bulk manganese chemicals as these dithionates will subsequently degrade, with the emission of harmful gases and, in some cases, the lowering of the quality of the product produced. All previous attempts to use a sulfur dioxide leach at production scale to reduce manganese dioxide materials have eventually failed due, amongst other things, to a build up of deleterious compounds in the process liquor.

Through its innovative research approach Mesa has been able to understand the reactions that lead to the formation of dithionates, and by controlling these reactions, to allow sulfur dioxide leaching to be efficiently used for the first time commercially to produce high value manganese products. The success of this work has showed that for the first time low grade manganese ores, presently deemed uneconomic as feed material for pyrometallurgical processing, can be utilized by Mesa’s sulfur dioxide leach process to produce high quality alkaline quality EMD products.

Mesa has sought patent protection for its innovative sulfur dioxide leach process approach in a number of key locations where low grade manganese ore deposits exist so that it can ensure, through licencing or production activities, that its investment in research leads to returns for its shareholders.

While Mesa has developed this technology specifically for treating low grade manganese dioxide ores to produce EMD, it also believes that this technology is applicable for treating any grade of manganese dioxide ore, or any other manganese dioxide containing materials. Examples of the latter including: mine site tailings, fumes and tailings from ferro-alloy production facilities, ocean floor manganese nodules, wastes from zinc refinery cells, wastes from nickel refining and the manganese dioxide contained in used alkaline or carbon zinc batteries returned for recycling. The solutions generated by processing such materials in conjunction with an ore feed in a Mesa leach could then be purified and used in the production of EMD, EMM and other manganese chemicals.

The Mesa Continuous Demonstration Plant Project

During 2001 the Company built and operated a Demonstration Plant that was a small-scale copy of its innovative sulfur dioxide leach process through to the production of EMD powders for battery testing evaluation.

The plant was designed by Lycopodium Pty Ltd and was located in a purpose built building onsite at Murdoch University. Mesa collaborated with Murdoch University and the AJ Parker Centre for Hydrometallurgy on the project. The operating staff for the six month long, twenty four hour per day operation were Mineral Science/Chemistry students and postgraduate students from these institutions, supervised by experienced Mesa staff.

The Demonstration Plant project was a highly successful research programme where many process conditions were verified and defined for later use in a commercial plant operation. Mesa also produced more than 500 kg of high purity alkaline grade EMD products that were delivered to key alkaline battery manufacturers around the world. These products were made under a range of specialized conditions that were tailored to specific battery company needs and the results from independent battery tested will be discussed in detail in a following section.

While the production of alkaline grade products was a key purpose of the Demonstration Plant programme, it was also significant that Mesa was able to reach equilibrium levels of all minor elements and thereby show that the sulfur dioxide leach process developed was robust. Furthermore, the Demonstration Plant exercise proved conclusively that Mesa had overcome the dithionate by-product issues that had previously hampered the use of sulfur dioxide leaching of manganese dioxide by other organizations.

Battery Performance Testing of Mesa’s EMD Products

A key outcome from Mesa’s extensive Demonstration Plant programme was to show the manufacturers of the highest quality alkaline batteries that Mesa had the technology in-house to make EMD that was equivalent to or better than the EMD’s that they were presently purchasing for use in their alkaline batteries.

To achieve this aim Mesa sent a range of its products to battery makers and laboratories around the world to gain independent verification as to the quality of the EMD products produced. This included an extensive programme that involved testing batteries made from the Mesa EMD under various test conditions that mimic the use of batteries in applications such as camera flashes, tape recorders, CD Walkman, motor driven toys, transistor radios plus a further set of continuous and pulsed tests that subject the batteries to extreme load conditions.

This range of extensive tests was also performed on batteries that had been aged for various lengths of time at elevated temperatures to replicate extreme storage conditions that batteries may be subjected to once purchased by a consumer. These aging tests are critical to the qualification of an EMD by a battery maker as they enable the battery maker to verify that the batteries made using the EMD producers’ product won’t cause corrosion and leaking that could damage the consumers’ expensive appliances.

The independent battery test results showed that Mesa’s products matched or exceeded the results obtained for EMD’s currently available on the market. These results were also confirmed by battery manufacturers who, without exception, indicated that the Mesa Demonstration Plant products were of very high quality, and should meet their quality specifications for commercial alkaline battery manufacture.

These comments are very significant considering that these favourable test results were collected using battery formulations that have yet to be optimised to complement the unique characteristics of the Mesa product, and considering that electroplating issues associated with the small size of the demonstration plant anodes (ie, detrimental ‘edge effects’) should result in better quality EMD being produced off full-scale anodes.

Solvent Extraction Technology for Manganese Processing

The company has been a leader in developing and pioneering a purely hydrometallurgical route for the dissolution of manganese from manganese dioxide wastes. This process is more cost effective and environmentally superior to the conventional roast reduction acid leach process.

Whilst the leaching of manganese dioxide ore for EMD production is the core activity for Mesa, several environmentally driven opportunities exist to supplement production by utilising waste product streams containing high manganese concentrations from existing production plants in Australia and overseas. These waste streams are currently neutralized (at significant cost) and consigned to tailings empoundments (at some environmental risk). To accommodate some of these waste streams Mesa has undertaken extensive testing and research in collaboration with CSIRO Minerals in the use of solvent extraction technologies for recovering and purifying manganese rich waste streams.

Mesa has performed extensive bench scale and pilot scale testing on a process flowsheet for recovering manganese units from manganese rich saline process streams exiting nickel laterite plants. This work has shown that solvent extraction is a viable alternative to the conventional processes for making EMD especially when waste manganese units are available for reprocessing. Mesa believe it is the first company to have successfully proven the applicability of solvent extraction for EMD production.

Mesa has sought patent protection for its process flowsheet which links sulphur dioxide leaching with the recovery and purification of manganese solution by solvent extraction. This process is unique to the EMD industry and is expected to become the benchmark for world’s best practice in years to come.

This research again demonstrates how Mesa is seeking to implement novel technology to the manganese processing industry for its own use or for the purpose of licensing it to industries where manganese wastes have proven to be a liability in the past. The key advantage of the solvent extraction route is the ability to concentrate dilute streams of manganese in saline backgrounds and then convert this into a high purity manganese sulfate solution that can be readily used for both EMD and EMM production.

Co-Production of Manganese Fertilizers and Manganese Electrolytics

EMD and EMM plant tailings ore currently impounded in tailings ponds at considerable financial and environmental cost to the producer and the local community and indeterminate environmental risk arising from the interplay of the inherent chemical nature of the material with the quality of the impoundment practices and the inherent nature of the lands upon which the ponds are built. In the Mesa process for producing EMD or EMM, the presence of SO2 as a reductant during the leaching process produces water insoluble oxides which are bioleachable.

The make up of these bioleachable oxides varies depending on the manganese ore source used for any given project, but invariably the tailing will produce a very good slow release MNF product for soils deficient in manganese, iron, calcium, sulfur, potassium and a range of other trace elements. Mesa has developed a unique process to utilise these tailing as a manganese rich MNF product, either in the form of a suspension concentrate for spray application, or in the form of a granulated product for mechanical/pneumatic dispersion. (NB: Such a product is particularly suited to the needs of agriculturalists in both India and Australia where Mesa is endeavoring to establish its process at full production scale.)

Hence, for an existing or aspiring producer of manganese electrolytic products, the adoption of the Mesa sulfur dioxide leach and MNF processes will:

  • eliminate the costs and risks associated with tailings impoundment;
  • reduce the land requirement for a plant by at least half;
  • take away the unsightly tailings ponds that are feature of conventional plants;
  • take away the cost and pollution potential of the conventional roasting circuit; and
  • create a second valuable revenue stream.

Capture and Use of SO2 Contained in Waste Gases

The volume and specification of the SO2 gas used in the Mesa sulfur dioxide leach process can be generated from sulfur in a number or different ways or bought in, on a just in time basis, or importantly, extracted from the waste gases of many thermal power plants or roasting plants at metal smelters and refineries. The choice of an SO2 gas source will depend on the location of any given manganese electrolytic plant, but because of the synergies that can be achieved, Mesa is focusing R&D effort towards methods of generating the SO2 gas requirement from sources of SO2 emissions to atmosphere.

Various techniques exist commercially for doing this and others are theoretically possible. Mesa is seeking to develop those that are technically and economically sound and provide benefits for both the SO2 emitter and the aspiring manganese electrolytic product producer. In this regard, our particular focus has been on ‘partial liquefaction’ technologies that will provide a high quality gas feed to the EMD or EMM producer, whilst at the same time providing a valuable component of the SO2 emitters environmental control processes. In this regard, it is instructive to note that in China today, the continued existence of many small scale thermal power plants is dependant on their meeting both the central government’s stringent new environmental standards and the additional requirement that they be associated with the production of a high value product.

Thus the use of Mesa processes to recognise the latent synergies between an EMD or EMM plant and a power plant can be a powerful solution in the developing world where demand for higher production volumes now must be reconciled with demand for improved environmental standards. Similarly, if say an EMD or EMM plant was sited adjacent to an electrolytic zinc refinery’s sinter plant, from which it derived its SO2 gas needs, it could also consume in the sulfur dioxide leach the andode slimes (sometimes referred to as ‘manganese mud’) that is produced in the zinc refining process and is a problematic and costly material to store in tailings ponds. This is a solution that would make great commercial and environmental sense wherever in the world it was sited.

Alternate SO2 Generation Methods

The most common method of producing SO2 involvers the burning of sulfur in air as is done in sulfuric acid production plants that do not utilize an SO2 waste gas stream from another process. This method can only produce 16% to 18% SO2 with the balance of the gas being predominantly nitrogen, which is far too low a concentration for use as the reductant in a leaching process. This method also creates hot gas handling problems that alone would preclude its use in practice. For these reasons, Mesa’s R&D efforts have been directed towards those methods that will allow SO2 concentrations of at least 80% to be achieved and handled, such as:

  • the burning of sulfur in oxygen;
  • the reacting of sulfur trioxide gas with molten sulfur; and
  • the reacting of oleum with molten sulfur.

Where SO2 needs to be generated rather than bought in as a liquefied gas or captured from a waste gas stream, the choice of a generation method will depend on on a number of factors that will be site specific. Mesa’s R&D efforts are directed towards ensuring that for any site, a solution that optimizes resource utilization, minimises costs and matches the technical capabilities of the plant operator will be available.

Crystal Structure of Manganese Dioxides

EMD Electrowinning Technology

EMD performance in batteries is not a static target and to ensure the company remains at the forefront of product quality, Mesa has been investing in R&D to allow the company to produce a “Best in Class” EMD product.

As relatively little is known about the crystal formation parameters that affect the fundamental properties of EMD, and hence its performance in batteries, this subject has been selected as a prime topic for collaborative research with key research institutions.

The objective of this project is to understand the types of crystal phases that occur in the best performing EMD’s through various microscopy techniques and then to use this information to model the type of manganese dioxide crystal that is best suited to superior battery performance. Once this is identifies the aim is to find a way that allows this crystal phase to be preferentially plated during the production process. The aim will then be to control the crystal phases and ideally promote the rate that the desired phase is formed in the plating cell. This project is drawing upon successful models developed at Curtin University for the alumina industry.

Mesa is presently collaborating with researchers at Curtin University of Technology, the AJ Parker Centre for Hydrometallurgy and the Nanochemistry Research Institute in a project titled “Better Batteries via Controlling the Properties of Electrolytic Manganese Dioxide”. This project is partly funded by the Commonwealth Government through a grant from the Australian Research Council and aims to address the shortcomings in the current understanding of how the most battery active EMD’s are formed.

Through the understanding of how to control the crystallization of the best EMD’s, by focusing on the relationships between fundamental physical, chemical and electrochemical properties, Mesa and its collaborators believe they will be able to optimize the EMD deposition process. This new level of understanding will ensure that EMD’s with superior battery performance will be consistently produced at Mesa’s production facilities and will assist Mesa to remain at the forefront of technological advances in the EMD industry.

Molecular Modelling

A part of the collaborative research project with Curtin University and the Nanochemistry Research Institute researchers are striving to understand the structures of key manganese dioxide crystals through the use of molecular modelling techniques. The researchers have focused most of their energy on understanding the key properties of the crystal phases that make up high quality alkaline grade EMD’s, but work has also progressed into the gaining a greater insight into the properties of the LiMn2O4 spinel.

This compound is important in the battery industry as it is the basis for the lithium manganese oxide (LMO) version of the Li-ion battery, where lithium ions move in and out of the spinel lattice, depending on the charge state of the rechargeable battery. The LMO battery has cost, environmental and weight advantages over the present cobalt based Li-ion battery, which are now bringing it into prominence.

While the benefits from this type of research work may not flow to Mesa in the short term, Mesa believes that by investing further in quality research, the company will have a competitive edge and will be at the leading edge of developments for many years to come and thus will create significant shareholder wealth.

Simultaneous Electro-Deposition of EMM and EMD

The conventional methods for producing manganese electrolytics involve the electro-deposition of EMM on the cathodes and EMD on the anodes of different electrochemical cells that are subjected to different operating conditions. Some research, such as that recently published by Irwin R Higgins in support of US patent application No. 907509, suggests that it is technically possible to deposit EMD and EMM simultaneously on the anode and cathode respectively of an undivided cell.

Whilst there is little doubt that this is technically and practically feasible, the real difficulty that a proponent would face is in ensuring that the chemical and physical characteristics of the EMD produced were in line with those that battery makers requires to optimise the performance of the EMD in their batteries. Despite this quite significant problem, Mesa believes that this is an area worthy of further study and is directing R&D effort to this end.

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