Gamma processes of shear flocculation, oil agglomeration and liquid–liquid extraction A. Ozkan, S. Duzyol ⇑ Department of Mining Engineering, Selcuk University, 42075 Konya, Turkey article info Article history: Received 6 August 2013 Received in revised form 27 May 2014 Accepted 3 June 2014 Available online 13 June 2014 Keywords: Gamma flotation Gamma shear flocculation Gamma oil agglomeration Gamma liquid–liquid extraction abstract Gamma flotation process is characterized by emphasis on the control of solution surface tension and the separation of minerals in suspension with this technique is based on the differences in wettability of min- erals. The wettability properties of mineral surfaces can be defined in terms of their values of critical sur- face tension of wetting (c c ) as a quantifying parameter, which is an essential property to achieve selectivity in surface chemistry-based separation processes. That is, the gamma flotation technique uti- lizes the differences in the critical surface tension of wetting (c c ) of minerals. Similar to the flotation method, shear flocculation, oil agglomeration and liquid–liquid extraction processes also utilize differ- ences in wettability of minerals. Therefore, the separations of minerals by the control of surface tension in the shear flocculation, oil agglomeration and liquid–liquid extraction methods can be provided. In this study, the separations of some minerals with these processes have been investigated by using the control of the solution surface tension and the successful results could be reached. Consequently, these new separation processes have been defined as ‘gamma shear flocculation’, ‘gamma oil agglomeration’ and ‘gamma liquid–liquid extraction’. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction As the grade of mineral deposits decreases, the valuable minerals often appear in the form of finely disseminated grains in an ore. Therefore, size reduction by crushing and grinding is required to liberate the valuable constituents. However, fine particles produced during the comminution processes decrease the efficiency of the concentration processes in mineral processing operations. Therefore, there is considerable interest in developing a process that could successfully handle such fine particles [1,2]. Shear floccula- tion is the aggregation of fine particles in a convenient stirring regime after hydrophobization by the adsorption of surfactants [3]. Oil agglomeration and liquid–liquid extraction are important separation techniques among oil-assisted fine particle processing processes [4]. In the oil agglomeration technique, hydrophobic min- erals in aqueous suspensions are aggregated by oil droplets since oil preferentially wets the hydrophobic surfaces. Solid particles, there- fore, can be bridged by the second liquid which is immiscible with the medium in which the process takes place [4,5]. In the case of liquid–liquid extraction process, large amounts of organic and aqueous phases are contacted and the minerals, depending on their hydrophobicity, transfer either to the aqueous or organic phases. Both processes are only possible when the treated minerals are sufficiently hydrophobic so that they are selectively wetted in water by oil [4,6]. The wettability properties of mineral surfaces can be defined in terms of their values of ‘critical surface tension of wetting (c c )’, which is an essential characteristic in achieving selectivity in surface chemistry processes such as flotation, shear flocculation, oil agglomeration and liquid–liquid extraction [7,8]. The contact angle (h) has been extensively used to assess the hydrophobicity or wettability degree of the minerals or solids in mineral process- ing theory and practice. Shafrin and Zisman [9] found that the contact angle (h) of a sessile liquid drop on a solid surface decreases in tandem with decrease of the air–liquid interfacial ten- sion. Thereafter, Yarar and Kaoma [10] reported that the flotation recovery of minerals decreases as decrease of the air–liquid interfacial tension of the liquids used as flotation medium. Similar to the flotation behavior of minerals, the shear flocculation, oil agglomeration and liquid–liquid extraction recoveries of minerals also decrease with decreasing the air–liquid interfacial tension. Eventually, while the flotation and shear flocculation of minerals do not occur at the air–liquid interfacial tensions below ‘the critical surface tension of wetting (c c )’ value of the mineral [10,11], the oil http://dx.doi.org/10.1016/j.seppur.2014.06.001 1383-5866/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +90 332 2232043; fax: +90 332 2410635. E-mail address: selmad@selcuk.edu.tr (S. Duzyol). Separation and Purification Technology 132 (2014) 446–451 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur