Nikolaos Koukoulis, Georgios N. Anastassakis
ABSTRACT. The current paper deals with the re-processing of mineralised mine waste from magnesite processing operations aiming at the recovery of the value. Two cases of mineralised waste were examined. First, waste derived from the removal of “fine” before hand-sorting, with particle size of -40 mm; this waste is usually stockpiled, comprises mostly of relatively coarse particles and is of relatively high-grade in magnesite. The separation methods applied were sorting, sink-float tests and magnetic separation. In general, the results from the application of physical separation methods were satisfactory. Commercial concentrates were obtained from sorting with MgCO3-grade ranging between 94 and 97% MgCO3 and yield about 46%; in case of mixing concentrate with middling, yield rises to 58-64% while grade slightly drops to 91-94%. Equally satisfactory were the results from sink-float separation at sp.gr. 2.88 (grade 95%, yield 45%) but questions arise from the small sp.gr. difference of magnesite and gangues. Finally, the less satisfactory results obtained from magnetic separation (grade around 80-85%, yield 33-65%) may be due to inefficient particles liberation and higher magnetic field is maybe required. Second, mineralised waste consisting of fine particles from size reduction operations were tested. These fines were processed with selective magnetic coating as well as co-agglomeration / magnetic separation techniques. In general, the results of physicochemical processing of fines were very encouraging both on single minerals and their artificial mixtures. In case of magnetic coating, the effect of pH, collector concentration and kerosene dose was studied first on single minerals. Optimum results were obtained for pH=9, dodecylamine solution 4.5×10-5 M and kerosene 2.5 L/t. Tests on artificial mineral mixtures at optimum conditions and magnetic separation at 0.8 A resulted in non-magnetic product with MgCO3-grade higher than 99%. The parameters examined in co-agglomeration / magnetic separation tests were the same as with magnetic coating. Best conditions for co-agglomeration on single minerals were pH=8, dodecylamine 2 kg/t, kerosene 4 L/t. Tests on mineral mixture reveals that the MgCO3-grade increases with dodecylamine but the yield drops.
Key words: magnesite, serpentine, waste, hydrophobic agglomeration.
DOI: 10.5281/zenodo.7007041
DOI: https://doi.org/10.58903/c16182118
1. Adiansyah J. S., Rosano M., Vink S., Keir G., 2015. A framework for a sustainable approach to mine tailings management: Disposal strategies, Journal of Cleaner Production, 108, 1050–1062. https://doi.org/10.1016/j.jclepro.2015.07.139
2. Anastassakis G., Design of an integrated resource management system for total resource recovery. Technical/ Economical problems and future perspectives, Proceedings TMS Fall 2002 Congress on Recycling and Waste Treatment, in: Mineral and Metal Processing: Technical and Economic Aspects, ed. B. Bjorkman, C. Samuelsson, J-O Wiksström, v. 1, 199 – 208.
3. Anastassakis G. N., 1999. A study on the separation of magnesite fines by magnetic carrier methods, Colloids and Surfaces – A: Physicochemical and Engineering Aspects, 149, 585-593. https://doi.org/10.1016/S0927-7757(98)00562-7
4. Anastassakis G. N., 2012. Fine/ultrafine mineral particles separation through hydrophobic agglomeration, Encyclopedia of Colloids and Surfaces, ed. P. Somasundaran, Taylor & Francis, England.
5. Bimpilas G., Anastassakis G. N., Magnetic separation of fine gangue minerals from magnesite as hydrophobic co-agglomerates, Proceedings of IMPC, 1-15 September 2016, Quebec City, Canada, paper No 338, ISBN: 978-1-926872-29-2, Canadian Institute of Mining, Metallurgy and Petroleum, Canada.
6. Dimopoulos I., 2012. Utilisation of magnesite hand-sorting waste from the location Gerorema, Evia, Diploma Thesis, National Technical University of Athens.
7. Dimopoulos I., Anastassakis G. N., Recovery of magnesite from fine waste material rejected before hand-sorting, Proceedings of XV Balkan Mineral Processing Congress, 12-16 June 2013, Sozopol, Bulgaria.
8. EC-JRC, 2009. Reference Document on Best Available Techniques for Management of Tailings and Waste-Rock in Mining Activities. European Commission Joint Research Centre, Luxembourg.
9. Eurostat, 2015. Waste Generation and Treatment. Publications Office of the European Union. http://ec.europa.eu/eurostat/data/database (access: June 22, 2022).
10. Fuerstenau D. W., Chander S., Abouzeid A. M., 1979. The recovery of fine particles by physical separation methods, P. Somasundaran & N. Arbiter (Eds.), AIMMPE.
11. Garbarino E., Orveillon G., Saveyn H., Barthe P., Eder P., 2018. Best available techniques (BAT) reference document for the management of waste from extractive industries. In: Accordance with Directive 2006/21/EC. Publications Office of the European Union, Luxembourg. https://publications.jrc.ec.europa.eu/repository/handle/JRC109657
12. Hoang D. H., Ebert D., Robert Möckel R., Rudolph M., 2021. Impact of sodium hexametaphosphate on the flotation of ultrafine magnesite from dolomite-rich desliming tailings, Minerals, 2021, 11(5), 499. https://doi.org/10.3390/min11050499
13. IAI, 2015. Bauxite Residue: Management Best Practice. International Aluminium Institute & European Aluminium Association.
14. Lottermoser B. G., 2010. Mine wastes: characterisation, treatment and environmental impacts, Springer, Berlin. https://doi.org/10.1007/978-3-642-12419-8
15. Rankin W. J., 2015. Towards zero waste, AusIMM Bull. 2015, 32–37.
16. Rulyov N. N., 2016. Combined microflotation of fine minerals: theory and experiment, Mineral Processing and Extractive Metallurgy, 125(2), 81-85.
17. Sajjad M., Otsuki A., 2022. Correlation between flotation and rheology of fine particle suspensions, Metals 2022, 12, 270. https://doi.org/10.1080/03719553.2016.1156303
18. Yang B., Huang P., Song S., Luo H., Zhang Y., 2018. Hydrophobic agglomeration of apatite fines induced by sodium oleate in aqueous solutions, Results in Physics, 9, 970-977 https://doi.org/10.1016/j.rinp.2018.03.049