## 1 Introduction  
Water resource depletion is a widespread issue on a global scale. With the growth of the global economy and the increase in population, this problem has become increasingly prominent [1; 2]. At present, the best solution to the lack of water resources is conservation while also developing and utilizing techniques to treat water of poor quality. Figuring out how to solve the problems of seawater desalination and sewage treatment cost effectively and in an energy-efficient way has become the key to solving the problem of water shortage [3; 4]. Membrane processes are now important in water treatment in many countries, because membrane separation has more advantages than thermal technology [5]. In particular, this includes avoiding expensive and inefficient heat, and a reduction in environmental problems associated with fuel combustion, thereby reducing production costs. Nevertheless, well-known membrane separation techniques, such as reverse osmosis (RO) [6], have been proven to be unsuitable for current need, which include, for example, the connection between membrane permeability and selectivity, while employing membrane technology for specific purposes [7; 8]. For example, for the desalination of high salt feed liquid, high level pre-treatment requirements for raw materials, and higher level of membrane contamination resistance, many membranes are ineffective at removing newly developed pollutants and small-molecule pollutants from water [9; 10] since membranes only have the ability to concentrate these contaminants and not completely eliminate them. Thus, researchers attempted to combine membrane separation technology with the aid of thermal distillation technology to integrate the relative merits of two approaches, namely membrane distillation (MD) [11; 12]. MD is a separation technique that relies on heat. The temperature difference between the membrane's two sides acts as the engine for heat transfer, which leads to a vapor pressure difference [13; 14]; this causes vapor to go through the membrane pores, inside the membrane module, and the condensation to pure water occurs at the cool liquid/gas interface [15]. On feeds that include volatility solutes [16], when these solutes' boiling points are lower than those of water, they will pass through the membrane so as to separate the raw material liquid. Due of MD's non-isothermal properties, a film that is hydrophobic will not be soaked by water; therefore, membrane contamination is not easy to occur. When compared to conventional membrane methods like RO [17; 18], it has a higher interception rate for solutes, and is unaffected by high salt solutions and high permeate pressure. Furthermore, lower operating levels of pressure and temperature are possible for MD [19; 20] because the membrane barrier only necessitates a narrower vapor space. It works well with green power sources or thermal waste sources [20; 21]. Additionally, because of its less complex configuration, it is becoming a practical separation process that can be used in ocean water and brackish water desalination, in the preparation of ultrapure water [22], chemical material recovery and concentration, water solutions' volatile solutes' removal and recovery, in juice from fruit and liquid food concentration, in cleaning up sewage, and in other fields [23]. Especially in the treatment of wastewater, membrane distillation can operate at extremely high concentrations, even to saturation, compared to other membrane processes [24; 25].