Membrane extraction is a new type of separation technology that combines membrane processes with liquid-liquid extraction processes. It differs from traditional liquid-liquid extraction processes in that the mass transfer process occurs on the interface layer formed by the feed liquid phase and the solvent phase filled with membrane pores. Therefore, it is also called fixed interface layer membrane extraction, abbreviated as membrane-based solvent extraction or membrane extraction. 

Membrane extraction involves placing a microporous membrane between the raw liquid and the extractant. Due to the extractant's wettability towards the membrane, it rapidly penetrates each micropore of the membrane and comes into contact with the raw liquid on the other side of the membrane, forming a stable interface layer. The separated solutes then pass through this interface layer from the raw liquid to the extractant. This mass transfer process does not involve the dispersion and aggregation of liquid droplets as in traditional liquid-liquid extraction processes. 

Characteristics of Membrane Extraction Technology: 

The membrane extraction process does not involve the dispersion and coalescence of phases, thereby reducing the carry-over loss of the extractant in the liquid phase. 

★ During the membrane extraction process, the feed liquid phase and the solvent phase flow on both sides of the membrane. There is no direct contact of liquid-liquid two-phase flow, and the flow of the feed liquid is not affected by the flow of the solvent. Therefore, the requirements for the performance of the extractant can be relaxed. 

The membrane extraction process is not affected by "backmixing" or restricted by "liquid flooding" conditions. 

The membrane extraction process can achieve the same-level extraction and desorption processes. The process's mass transfer efficiency can be enhanced by measures such as promoting migration through a flowing carrier. 

During membrane extraction, the feed liquid phase and the solvent phase flow on both sides of the membrane respectively, without forming a direct liquid-liquid two-phase flow. When selecting the extraction agent, the requirements for its physical properties are greatly relaxed, and some high-concentration and highly efficient extraction agents can be used. 

Extraction membrane: 

The membrane extraction methods can be classified into two main categories: hydrophobic membranes and hydrophilic membranes. 

The main types of hydrophobic membrane materials include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polypropylene (PP), etc. 

The hydrophilic membrane materials mainly include cellulose esters, polycarbonate (PC), polysulfone/polyethersulfone (PSF/PES), polyimide/polyetherimide (PI/PEI), and polyalkylamide (PA), etc. 

Selection of extractant: 

☆ Selectivity is high, and the separation factor for the separated substances should be large. 

☆ The extraction capacity is large. The extractant should have functional groups and an appropriate molecular weight. 

☆ It has strong chemical stability, is not prone to hydrolysis or decomposition, is resistant to acids, alkalis, salts, oxidants or reductants, and causes little corrosion to the equipment. 

The physical and chemical properties of the extractant are appropriate, including the density, viscosity of the extractant, and the interfacial tension of the system. 

☆ The solubility is excellent. The extractant and its complex are easily soluble in the organic phase but insoluble in the aqueous phase. 

☆ Faster extraction and desorption efficiency. 

☆ Easy for re-extraction and solute recovery. 

☆ Safe operation and highly efficient.

1. Each pump can operate independently and be adjusted separately for speed. The pressurization power component uses a custom peristaltic pump, which is quiet, has stable pressure, and has reliable performance. It also has a frequency conversion control function, allowing the flow rate to be freely adjusted. The material feeding flow rate can be adjusted through buttons to ensure that different materials can be tested under different flow rates. 

2. The power supply of the equipment is controlled by two switches. When the low-voltage power is in operation, it can fully ensure the safety of both the equipment and personnel. 

3. The pump machine is equipped with a pressure sensing system. It allows for the setting of the maximum pressure, enabling automatic protection against overpressure, thus ensuring the safety of both personnel and materials during the test. 

4. It can be equipped with other types of microfiltration and ultrafiltration membrane elements. 

5. The overall appearance of the equipment is elegant, with excellent stability, simple operation, small running volume, and the frame is made of stainless steel. All stainless steel welding is carried out under automatic argon protection, with single-sided welding and double-sided forming. The inner and outer surfaces of the pipes have excellent quality, and there are no welding points in the pipes in contact with the materials, ensuring the equipment's pressure resistance and corrosion resistance. The equipment is easy to operate, clean and hygienic, and safe and reliable.

Three peristaltic pumps, three sets of digital pressure gauges, three sets of pressure sensors, three beakers, three pressure regulating valves, three stirrers, equipment brackets, interlocking couplings, and a number of pipes and their connecting pieces.