National University of Science and Technology (NUST) MISIS (Moscow, Russia):

Pestryak I. V., Associate Professor, Candidate of Engineering Sciences, Associate Professor, spestryak@mail.ru
Morozov V. V., Professor, Doctor of Engineering Sciences, Professor, dchmggu@mail.ru

In conditions of closed water circulation, the floatability of molybdenite decreases. Similarly, the recovery of molybdenite into the bulk concentrate is reduced when dosing lime in the grinding operation. To establish the reasons for the decline in technological indicators, the influence of calcium ions on the state of the surface and floatability of molybdenite in the conditions of grinding and collective flotation was investigated. Thermodynamic calculations show the possibility of formation under grinding conditions (pH = 7.2–8.5) on the surface of the calcium molybdate mineral. The formation of insoluble compounds is indicated by a decrease in the oxidation rate of the mineral with an increase in the concentration of calcium and molybdenum ions in the aqueous phase. X-ray spectroscopic studies have shown that an excess of calcium ions leads to chemical interaction and fixation of calcium compounds on the surface of molybdenite. In the pH range from 7.6 to 8.5, calcium molybdenum prevails, and in the pH range from 8.5 to 10.3 calcium carbonate prevails It has been established that with an increase in the pH of the medium to 10.3, characteristic of the flotation process, calcium molybdate becomes calcium carbonate, which hydrophilizes the surface of molybdenum and reduces its floatability. To prevent the negative influence of calcium and molybdat ions on the flotation of molybdenum, it is proposed to use water sources with a reduced concentration of these components. It is possible to reduce the formation of hydrophilic coatings on the surface by reducing the rate of oxidation of molybdenum or to prevent the formation of calcium molybdat on it by regulating the pH of the aqueous phase.

1. Baatarkhuu Zh. Technology of copper porphyry ore beneficiation based on the study of their genetic and morphological features. Erdenet: Publisher MAMBH–MMRA, 2006. p. 182.
2. Pestryak I. V., Erdenetuyaa O., Morozov V. V. Return water improvement at Erdenet mining complex. Obogashchenie Rud. 2013. No. 2. pp. 3–8.
3. Nakhael F., Irannajad M. Investigation of effective parameters for molybdenite recovery from porphyry copper ores in industrial flotation circuit. Physicochemical Problems of Mineral Processing. 2014. Vol. 50(2). pp. 477–491.
4. Desyatov A. M., Khersonsky M. I., Ganbaatar Z., Delger R., Baatarkhuu Zh., Tuyaa Ts. Improvement of copper–molybdenum flotation in rough concentrate scavenging circuit. Gorny Informatsionno-Analiticheskiy Byulleten. 2013. No. 10. pp. 74–79.
5. Castro S. Physico-chemical factors in flotation of Cu-Mo-Fe ores with seawater: a critical review. Physicochemical Problems of Mineral Processing. 2018. Vol. 54 (4). pp. 1223–1236.
6. Castro S., Rioseco P., Laskowski J. S. Depression of molybdenite in sea water. Proc. of XXVI International Mineral Processing Congress, New Delhi, India. 2012. pp. 737–752.
7. He Wan, Juanping Qu, Tingshu He, Xianzhong Bu, Wei Yang, Hui Li A new concept on high-calcium flotation
wastewater reuse. Minerals. 2018. Vol. 8 (11). pp. 496–504.
8. Bocharov V.A., Ignatkina V.A., Khachatryan L.S., Baatarkhuu Zh. Modified reagent mode in porphyry coppermolybdenum ore flotation. Fiziko-tekhnicheskie Problemy Pererabotki Rudnykh Poleznykh Iskopaemykh. 2008. No. 1. pp. 27–31.
9. Pestryak I. V., Erdenetuyaa O., Morozov V. V. Research and testing of reagent-free conditioning of effluents of the industrial unit of the mining and processing plant. Nauchnyi Vestnik MGGU. 2012. No. 12. pp. 66–80.
10. Nagaraj D. R., Farinato R. S. Chemical factor effects in saline and hypersaline waters in the flotation of Cu and Cu-Mo ores. Proceedings of XXVII International Mineral Processing Congress, Santiago, Chile. 2014. Chap. 3: Flotation chemistry.
11. Abramov A. A. Flotation. Physical and chemical modeling of processes. Moscow: Gornaya Kniga, 2010. 607 p.
12. Thermal constants of substances: database. URL: http://www.chem.msu.su/cgibin/tkv.pl?show=welcome.html
13. Chase M. W., Davies C. A., Downey J. R., Frurip D. J., McDonald R. A., Syverud A.N. JANAF Thermochemical tables. Third edition. Journal of Physical and Chemical Reference Data. 1985. Vol. 14, Supplement No. 1. 1880 p.
14. Zanin M., Ametov I., Grano S., Zhou L., Skinner W. A study of mechanisms affecting molybdenite recovery in a bulk copper/molybdenum flotation circuit. International Journal of Mineral Processing. 2009. Vol. 93. pp. 256–266.
15. Semenova I. V., Khoroshilova A. N., Florianovich G. M. Corrosion and corrosion protection. Moscow: Fizmatlit, 2010. 416 p.
16. Liu W., Moran C. J., Vink S. A review of the effect of water quality on flotation. Minerals Engineering. 2013. Vol. 53. pp. 91–100.
17. Castro S., Lopez-Valdivieso A., Laskowski J. S. Review of the flotation of molybdenite. Part I: Surface properties and floatability. International Journal of Mineral Processing. 2016. Vol. 148. pp. 48–58.