Chemical fiber oil wastewater needs to be separated

http://bbs.hcbbs.com/viewthread.php?tid=100112 explains it in more detail

Use a demulsifier. Demulsifier: Since some solids are insoluble in water, when one or more of these solids are present in large quantities in an aqueous solution, they can exist in the water in an emulsified state under the action of hydraulic forces or external agitation, thus forming an emulsion. Theoretically, such a system is unstable, but when certain surfactants (such as soil particles) are present, the emulsification becomes very strong, to the point where it is difficult to separate the two phases. The most typical examples are oil-water mixtures in oil-water separation processes and water-oil mixtures in wastewater treatment; in these cases, relatively stable water-in-oil or oil-in-water structures are formed, and the theoretical basis for this is the \"double-layer structure\". 　　In this case, some chemicals are added to disrupt the stable double-layer structure as well as to stabilize the emulsion system, thereby achieving phase separation. These agents used to break down emulsions are called demulsifiers.

Types of demulsifiers: 1. W/O type emulsion demulsifiers. In the development of demulsifiers for crude oil, W/O type emulsion demulsifiers were the first to be developed and applied. Worldwide, three generations of products have been developed since the 1920s to the present. The first generation of W/O emulsion demulsifiers appeared in the 1920s–1930s; they were mainly low-molecular-weight anionic SAA (surfactants), including carboxylates, sulfates, and sulfonates. These demulsifiers were characterized by being inexpensive, requiring large amounts to be used, having poor efficacy, and being susceptible to the influence of electrolytes. The second generation of demulsifiers developed in the 1940s–1950s were mainly low-molecular-weight non-ionic SAA substances such as OP, PEG-8000, and Tween. These demulsifiers could withstand acids, bases, and salts, but their demulsification efficiency was still poor. After the 1960s, third-generation demulsifiers were developed, mainly high-molecular-weight non-ionic SAA types. These demulsifiers feature low dosage requirements, good demulsification efficiency, and high specificity, but they have poor versatility [5]. China’s petroleum industry started relatively late; the major oil fields in the east were put into development one after another from the late 1950s. Initially, second-generation domestic W/O emulsion demulsifiers such as OP, PEG, and sulfonated castor oil, as well as SAA products, were used for a short period of time, but they failed to meet the production requirements. Normal dehydration of emulsified crude oil had to be maintained by using third-generation foreign demulsifiers. In the mid-1960s, the Shengli Oil Field and the Daqing Oil Field collaborated with domestic research institutions to develop the third-generation domestic W/O type emulsion demulsifiers. In-depth studies were conducted on the demulsification efficiency and mechanisms of these domestic demulsifiers, which further promoted their adoption and use. The main W/O type emulsion demulsifiers developed and used in our country are listed in Table 1. 2 O/W emulsion demulsifiers. O/W emulsion demulsifiers were developed relatively late; these demulsifiers can be classified into the following four categories: The first category consists of electrolytes, which are compressible and help reduce the diffusion double layer on the surface of oil droplets, thereby decreasing the charge on those surfaces and increasing the likelihood of collision and merging between the oil droplets. Examples of electrolytes that can be used include NaCl, MgCl2, CaCl2, Al(NO3)3, CrCl3, and ZrOC2 ； The second category consists of low-molecular-weight alcohols, such as methanol, ethanol, n-butanol, isopropanol, n-pentanol, etc.; low-molecular-weight amines or low-molecular-weight acids also have effects similar to those of low-molecular-weight alcohols ； The third category is SAA, which mainly includes anionic SAA such as cetyltrimethylammonium chloride and didecyldimethylammonium chloride. These can react with anionic emulsifiers to alter their hydrophile-lipophile balance, or they can adsorb on the surface of water-soluble clay particles to change their wettability, thereby disrupting O/W emulsions. Furthermore, some anionic SAA that can serve as O/W emulsifiers, as well as oil-soluble non-ionic SAA, can also be used as O/W emulsion demulsifiers. The fourth category consists of high-molecular-weight substances; cationic high-molecular-weight substances are primarily used, but non-ionic high-molecular-weight substances can also be employed. Demulsification is achieved by forming an unstable adsorption film that coalesces oil droplets or by using solubilizing emulsifiers. The various demulsifiers mentioned above are usually used in combination; for example, alkoxylated phenolic resins are combined with polyamine polyethers, high-concentration petroleum sulfonates are combined with inorganic salts, low-molecular-weight alcohols are combined with salts, and quaternary ammonium salts, alcohols, and salts are combined as well. The effect of these composite agents is better than that of the individual agents used alone. The use and development of O/W emulsion demulsifiers in our country have just begun; to date, only one O/W emulsion demulsifier, CW-01, has been developed. It was developed in 1989; its production method involves the ring-opening polymerization of epichlorohydrin, after which the resulting chlorinated polyether is cationized using a low-molecular-weight amine to yield a cationic polyether. This agent is a polymeric SAA with both cationic and non-ionic properties, and it is highly effective in removing emulsified oil droplets from oilfield wastewater. It is currently widely used in the wastewater treatment systems of the Shengli Oilfield and other oilfields in combination with other demulsifiers.

After demulsification, air flotation can be used to separate oil from water.

I’m sorry; I didn’t explain clearly the components of synthetic fiber oils. The components of synthetic fiber oils can be divided into two main categories: (1) Main components—smoothers, antistatic agents, emulsifiers； (2) Secondary components: wetting agents, softeners, chelating agents, leveling agents, antioxidants, detergents, penetrants, pH regulators, viscosity improvers. I’ve come up with a plan; please help me analyze it: first use microfiltration for pre-treatment, then proceed with nanofiltration. The concentrated liquid can be reused, while the permeate flows into the subsequent wastewater treatment system. The permeate after nanofiltration should not pose too much strain on the subsequent wastewater treatment processes, right? Is this method feasible? About 3.5 T per day, how much would the investment be?