Surface nanobubbles on the hydrophobic surface and their implication to flotation

Abstract

Nanobubbles play a potential role in the application of the flotation of fine particles. In this work, the identification of nanoentities was performed with a contact mode atomic force microscope (AFM). Moreover, the influences of setpoint ratio and amplitude of the cantilever and the responses of the formed surface nanobubbles to the fluctuation of pH, salt concentration, and surfactant concentration in the slurry were respectively studied. Nanobubbles were reported on the highly oriented pyrolytic graphite (HOPG) surface as the HOPG was immersed in deionized water under ambient temperature. The coalescence of nanobubbles occurred under contact mode, which provides strong evidence of the gaseous nature of these nanostructures on HOPG. The measuring height of the surface nanobubbles decreased with the setpoint ratio. The changes in the pH and concentration of methyl isobutyl carbinol (MIBC) show a negligible influence on the lateral size and height of the preexisting surface nanobubbles. The addition of LiCl results in a negligible change of the lateral size; however, an obvious change is noticed in the height of surface nanobubbles. The results are expected to provide a valuable reference in understanding the properties of surface nanobubbles and in the design of nanobubble-assisted flotation processes.

Keywords

surface nanobubbles / flotation / pH / salt concentration / surfactant concentration

References

[1] Yoon RH, Luttrell GH. The effect of bubble size on fine particle flotation. Miner. Process. Extr. Metall. Rev., 1989, 5(1–4): 101.

[2] Ozkan A, Aydogan S, Yekeler M. Critical solution surface tension for oil agglomeration. Int. J. Miner. Process., 2005, 76(1–2): 83.

[3] Duzyol S, Ozkan A, Yekeler M. Critical oil-liquid interfacial tension for some oil-assisted fine particle processing methods. Colloids Surf. A, 2012, 398, 32.

[4] Duzyol S, Ozkan A. Effect of contact angle, surface tension and zeta potential on oil agglomeration of celestite. Miner. Eng., 2014, 65, 74.

[5] Weisseborn PK, Warren LJ, Dunn JG. Selective flocculation of ultrafine iron ore. 1. Mechanism of adsorption of starch onto hematite. Colloids Surf. A, 1995, 99(1): 11.

[6] Mandre NR, Panigrahi D. Studies on selective flocculation of complex sulphides using cellulose xanthate. Int. J. Miner. Process., 1997, 50(3): 177.

[7] Dogu I, Arol AI. Separation of dark-colored minerals from feldspar by selective flocculation using starch. Powder Technol., 2004, 139(3): 258.

[8] Song SX, Valdivieso AL. Hydrophobic flocculation flotation for beneficiating fine coal and minerals. Sep. Sci. Technol., 1998, 33(8): 1195.

[9] Song S, Lopez-Valdivieso A, Reyes-Bahena JL, Lara-Valenzuela C. Floc flotation of galena and sphalerite fines. Miner. Eng., 2001, 14(1): 87.

[10] Song S, Zhang Y, Wu K, Lopez-Valdivieso A, Lu S. Flotation of coal fines as hydrophobic flocs for ash rejection. J. Dispersion Sci. Technol., 2004, 25(1): 75.

[11] Parker JL, Claesson PM, Attard P. Bubbles, cavities, and the long-ranged attraction between hydrophobic surfaces. J. Phys. Chem., 1994, 98(34): 8468.

[12] S.T. Lou, Z.Q. Ouyang, Y. Zhang, X.J. Li, J. Hu, M.Q. Li, and F.J. Yang, Nanobubbles on solid surface imaged by atomic force microscopy, J. Vac. Sci. Technol. B, 18(2000), No. 5, art. No. 2573.

[13] Ishida N, Inoue T, Miyahara M, Higashitani K. Nano bubbles on a hydrophobic surface in water observed by tapping-mode atomic force microscopy. Langmuir, 2000, 16(16): 6377.

[14] Tyrrell JWG, Attard P. Atomic force microscope images of nanobubbles on a hydrophobic surface and corresponding force-separation data. Langmuir, 2002, 18(1): 160.

[15] Ishida N, Higashitani K. Interaction forces between chemically modified hydrophobic surfaces evaluated by AFM—The role of nanoscopic bubbles in the interactions. Miner. Eng., 2006, 19(6–8): 719.

[16] Peng H, Hampton MA, Nguyen AV. Nanobubbles do not sit alone at the solid-liquid interface. Langmuir, 2013, 29(20): 6123.

[17] Zhang XH, Kumar A, Scales PJ. Effects of solvency and interfacial nanobubbles on surface forces and bubble attachment at solid surfaces. Langmuir, 2011, 27(6): 2484.

[18] Knüpfer P, Ditscherlein L, Peuker UA. Nanobubble enhanced agglomeration of hydrophobic powders. Colloids Surf. A, 2017, 530, 117.

[19] Zhou ZA, Xu ZH, Finch JA, Masliyah JH, Chow RS. On the role of cavitation in particle collection in flotation — A critical review. II. Miner. Eng., 2009, 22(5): 419.

[20] Li HP, Afacan A, Liu QX, Xu ZH. Study interactions between fine particles and micron size bubbles generated by hydrodynamic cavitation. Miner. Eng., 2015, 84, 106.

[21] Calgaroto S, Azevedo A, Rubio J. Flotation of quartz particles assisted by nanobubbles. Int. J. Miner. Process., 2015, 137, 64.

[22] Tao DP, Sobhy A. Nanobubble effects on hydrodynamic interactions between particles and bubbles. Powder Technol., 2019, 346, 385.

[23] W.G. Zhou, C.N. Wu, H.Z. Lv, B.L. Zhao, K. Liu, and L.M. Ou, Nanobubbles heterogeneous nucleation induced by temperature rise and its influence on minerals flotation, Appl. Surf. Sci., 508(2020), art. No. 145282.

[24] Stöckelhuber KW, Radoev B, Wenger A, Schulze HJ. Rupture of wetting films caused by nanobubbles. Langmuir, 2004, 20(1): 164.

[25] V.S. Ajaev, Effect of nanoscale bubbles on viscous flow and rupture in thin liquid films, Phys. Fluids, 18(2006), No. 6, art. No. 068101.

[26] Hassas BV, Jin JQ, Dang LX, Wang XM, Miller JD. Attachment, coalescence, and spreading of carbon dioxide nanobubbles at pyrite surfaces. Langmuir, 2018, 34(47): 14317.

[27] Butt HJ, Cappella B, Kappl M. Force measurements with the atomic force microscope: Technique, interpretation and applications. Surf. Sci. Rep., 2005, 59(1–6): 1.

[28] C.W. Li, X. Li, M. Xu, and H.J. Zhang, Effect of ultrasonication on the flotation of fine graphite particles: Nanobubbles or not? Ultrason. Sonochem., 69(2020), art. No. 105243.

[29] Lohse D, Zhang XH. Surface nanobubbles and nanodroplets. Rev. Mod. Phys., 2015, 87(3): 981.

[30] Evans DR, Craig VSJ, Senden TJ. The hydrophobic force: Nanobubbles or polymeric contaminant?. Physica A, 2004, 339(1–2): 101.

[31] Borkent BM, de Beer S, Mugele F, Lohse D. On the shape of surface nanobubbles. Langmuir, 2010, 26(1): 260.

[32] Berkelaar RP, Dietrich E, Kip GAM, Kooij ES, Zandvliet HJW, Lohse D. Exposing nanobubble-like objects to a degassed environment. Soft Matter, 2014, 10(27): 4947.

[33] An HJ, Liu GM, Craig VSJ. Wetting of nanophases: Nanobubbles, nanodroplets and micropancakes on hydrophobic surfaces. Adv. Colloid Interface Sci., 2015, 222, 9.

[34] Ditscherlein L, Fritzsche J, Peuker UA. Study of nanobubbles on hydrophilic and hydrophobic alumina surfaces. Colloids Surf. A, 2016, 497, 242.

[35] Yang JW, Duan JM, Fornasiero D, Ralston J. Very small bubble formation at the solid-water interface. J. Phys. Chem. B, 2003, 107(25): 6139.

[36] Zhang XH, Quinn A, Ducker WA. Nanobubbles at the interface between water and a hydrophobic solid. Langmuir, 2008, 24(9): 4756.

[37] Zhang XH, Uddin MH, Yang HJ, Toikka G, Ducker W, Maeda N. Effects of surfactants on the formation and the stability of interfacial nanobubbles. Langmuir, 2012, 28(28): 10471.

[38] Anczykowski B, Krüger D, Babcock KL, Fuchs H. Basic properties of dynamic force spectroscopy with the scanning force microscope in experiment and simulation. Ultramicroscopy, 1996, 66(3–4): 251.

[39] Su CM, Huang L, Kjoller K. Direct measurement of tapping force with a cantilever deflection force sensor. Ultramicroscopy, 2004, 100(3–4): 233.

[40] S. Yang, E.S. Kooij, B. Poelsema, D. Lohse, and H.J.W. Zandvliet, Correlation between geometry and nanobubble distribution on HOPG surface, Europhys. Lett., 81(2008), No. 6, art. No. 64006.

[41] Zhao BY, Song Y, Wang S, Dai B, Zhang LJ, Dong YM, Lü JH, Hu J. Mechanical mapping of nanobubbles by PeakForce atomic force microscopy. Soft Matter, 2013, 9(37): 8837.

[42] Mishchuk N, Ralston J, Fornasiero D. Influence of very small bubbles on particle/bubble heterocoagulation. J. Colloid Interface Sci., 2006, 301(1): 168.

[43] Mishchuk NA. The model of hydrophobic attraction in the framework of classical DLVO forces. Adv. Colloid Interface Sci., 2011, 168(1–2): 149.