There is increasing pressure from authorities in many countries to find cyanide-free methods for gold processing due to environmental and safety risks. Therefore, it is now under investigation whether the knowledge extraction and formalization procedure can be applied for comparing cyanide-free leaching methods for a certain type of raw material. Research is needed to determine and code the similarity models related to cyanide-free processes. The task is challenging, since most of the processes are still in the development phase and there is not much information available on the new-coming processes.
At the moment, primary gold production is based on cyanide leaching of gold ores [
The author is conducting doctoral studies in Aalto University, Finland with the aim
to develop a tool for comparing cyanide-free gold leaching methods. The tool will
uti-lize case-based reasoning (CBR), which uses fuzzy logic to compare real life cases
with the user’s input material [
In addition to the CBR tool, new hydrometallurgical research will be made in the field of cyanide-free gold leaching. When possible, this new information will be incorporated into the CBR tool, either as additional cases or as a basis for constructing similarity models. 2
The tasks of the research project are divided into two categories; implementation of the process selection tool (T1) and evaluation and development of existing cyanidefree leaching methods (T2). 2.1
The first task is divided into four sub-tasks. First, the amount and quality of the relevant and available information needs to be mapped (T1.1). Then a simple prototype tool is developed for general use (T1.2) and a user interface will be constructed (T1.3). After the construction of the prototype tool, a more complex tool will be implemented for professional use (T1.4).
Task 2 is also divided into four sub-tasks. First, the most promising cyanide-free gold leaching methods are determined for further inspection (T2.1). Simultaneously, an extensive literary research is conducted to support both T2.1 and the construction of the CBR based tool (T2.2). Then the functionality of selected leaching processes is experimentally verified (T2.3). Challenges detected during the experiments are taken under closer inspection and attempts will be made to discover solutions to these processing difficulties (T2.4). 2.3
A half-year research period is being arranged to the research group of Professor Thomas Roth-Berghofer in the University of West London (UWL). Their group has extensive knowledge on CBR applications and this collaboration will greatly benefit both univer-sities. 2.4
The schedule for the research work that will be carried out are presented in Table 1. The doctoral dissertation will be composed simultaneously with the research work over the three-year-project. This project began in February 2016, when the author started as a doctoral candidate in the research group of Hydrometallurgy and Corrosion in Aalto University. Since then, a conference paper for ICCBR’16 has been completed and a non-peer-reviewed paper has also been written for a gold processing conference ALTA2016. Altogether, the project has advanced as planned; all tasks scheduled to begin during spring 2016 have been initiated (T1.1; T1.2; T2.1; T2.2; T2.3).
Rintala et al. [
A preliminary knowledge model has already been constructed using the myCBR 3.01 open source software and a detailed description of it will be given in the author’s poster 1 http://mycbr-project.net/ presentation in ICCBR’16. Naturally, this is just a simple beginning, on which the author intends to build upon later during this project. In order to illustrate the tool, the preliminary model is described here in short.
The system utilizes attributes presented in Table 2. The attributes were selected based on a review article analysis and interviews of hydrometallurgical professionals.
The case base of 24 specimens was compiled from various scientific articles that presented experimental data on cyanide-free leaching of gold ores. As an example, an imaginary case is presented in Table 3.
Similarity models were developed for each attribute. Only two methods were present in the cases and therefore the similarity between those values was either 1 or 0. Attributes of the type Floating point number were given linear distance functions, whereas the mineralogical attributes Mineral 1 (most abundant in the ore) and Mineral 2 (second most abundant in the ore) were assigned similarity values based on the types of metallic and non-metallic chemical elements present in the minerals. The cases were assigned global similarities from 0.00 to 1.00 based on the combined local similarities.
One possible way for a researcher to utilize the tool is when they are faced with a gold ore that has not been experimented on with cyanide-free leaching techniques. They would analyze the material, query its mineralogy and gold content and as a result they would get the previously conducted experiments on most similar gold ores. This way they could aquire relevant information about the cyanide-free techniques applicable for their particular material. Then they could perform experiments on the material, thus producing a new case for the case base.
At the moment, the solution does not describe the leaching technique in more detail than just the leaching agent and the acquired result in the form of the Extraction attribute. As the tool is developed, more process parameters will be added such as temperature, pressure and solid-liquid ratio.
Towards the end of this PhD, an evaluation will be performed in the form of an actual material that will be queried and laboratory scale test that will be conducted on the basis of the results given by the CBR tool. Alternatives to CBR have yet to be considered in this project. 4
The doctoral dissertation will be a thesis by publication, consisting of a published conference paper and journal articles. At the moment, the scheme for the publications is as follows: • Applicability of case-based reasoning for selection of cyanide-free gold leaching methods
Conference: ICCBR’16, Atlanta Georgia, USA (accepted) • A case-based reasoning tool for comparing cyanide-free gold leaching processes • Evaluation of a case-based reasoning tool for comparing cyanide-free gold leaching processes • Challenges related to gold ore leaching in chloride solutions – from laboratory scale to industrial process 5