2.1. Direct contact membrane distillation (DCMD)
Direct contact membrane distillation (DCMD) is the most widely
used configuration in MD due to its simplicity [19]. As such, a benchscale DCMD was used in this study as shown in Fig. 1. The membrane
cell was made of acrylic with depth, width, and length of 0.2 cm, 5.0 cm
and 8.0 cm, respectively. A hydrophobic polytetrafluoroethylene
(PTFE) flat sheet membrane (General Electric, US) with used with a
40 cm2 effective membrane area for mass transfer. The membrane
support layer is made of polypropylene. The porosity, average pore size
and membrane thickness provided by the supplier were 70–80%,
0.2 µm, and 179 µm, respectively [15].
A moderate temperature of 55 °C was used as feed temperature (Tf).
This is based on our previous study that showed organic fouling
reduction at lower feed temperature [14]. Deionized (DI) water was
used as the initial permeate solution, which was set at a permeate
temperature (Tp) of 25 °C. The bulk temperatures were maintained at
± 3 °C for all experiments. The feed and permeate solutions (2 L each)
were channelled into the membrane cell at a feed and permeate flow
velocity (vf and vp) of 0.06 m/s in a counter current mode with a gear
pump.