Journal of Physical Science, Vol. 30(3), 207–221, 2019 © Penerbit Universiti Sains Malaysia, 2019. This work is licensed under the terms of the Creative Commons Attribution (CC BY) (http://creativecommons.org/licenses/by/4.0/). Efect of Additives on Hydrophobicity of PVDF Membrane in Two-stage Coagulation Baths for Desalination Abdul Latif Ahmad, * Mohamad Razif Mohd Ramli and Mohamad Izrin Mohamad Esham School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Pulau Pinang, Malaysia * Corresponding author: chlatif@usm.my Published online: 25 November 2019 To cite this article: Ahmad, A. L., Mohd Ramli, M. R. & Mohamad Esham, M. I. (2019). Efect of additives on hydrophobicity of PVDF membrane in two-stage coagulation baths for desalination. J. Phys. Sci., 30(3), 207–221, https://doi.org/10.21315/jps2019.30.3.13 To link to this article: https://doi.org/10.21315/jps2019.30.3.13 ABSTRACT: This research aimed to improve the hydrophobic polyvinylidene fuoride (PVDF) membrane for direct contact membrane distillation (DCMD) desalination by mixing various additives (dibutyl phthalate and glycerol) in polymer solution via two- stage/dual coagulation bath (CB) system. The efect of each additive on the surface and cross-sectional morphology of PVDF membrane was investigated. The addition of additives showed increased in membranes porosity, but the water contact angle was less than 90° when immersed in single CB (distilled water). Membrane prepared with two-stage CB system immersed into methanol CB for 20 min and transferred into distilled water CB for 24 h exhibited high water contact angle of 114.2°, 142.6° and 120.1° for membrane M-3, M-4 and M-5, respectively. The porosity of membrane signifcantly increased when incorporated with additives. The membrane was further evaluated in DCMD operation for separation performance. The DCMD tested using distilled water and 35 g l –1 of sodium chloride (NaCl) aqueous solution in feed showed M-4 achieved the highest fux among other membranes at 13.85 kg –2 m –2 h –1 with 99% salt rejection under 70°C of feed temperature. Keywords: Polyvinylidene fuoride, coagulation bath, direct contact membrane distillation, PVDF, desalination 1. INTRODUCTION Membrane technology has become a popular separation technology and has been widely applied for its application in food processing, pharmaceutical industry, drinking water treatment, water purifcation, desalination of sea and brackish water. 1–5 Pressure-driven membrane water treatment process such as microfltration