Pressure-driven membrane separation technology, also known as membrane filtration technology, is an advanced method of advanced water treatment. According to the different membrane selectivity, it can be divided into reverse osmosis (RO), nanofiltration (NF), and ultrafiltration. Filter (UF) and microfiltration (MF).
Membrane filtration technology introduction
Membrane Filtration Technology Microfiltration Membrane Filtration (MF)
Microfiltration Membrane (MF) filtration technology is a screening process and belongs to the category of precision filtration. It can be divided into two types: surface type and deep type.
The microfiltration operation has both deadend and crossflow filtration. The former type of membrane is used in dilute feeds and small scale applications, and the filters are mostly disposable. The latter, also known as tangential flow operation or cross-flow filtration, is suitable for industrial large-scale applications. The characteristics of such membranes are the need for periodic on-line cleaning and regeneration to restore the filtration performance of the membrane.
MF is mainly used in the sterilization and filtration of the pharmaceutical industry, water for the integrated circuits of the electronics industry, etc. In addition, the pretreatment of the municipal wastewater treatment and wastewater treatment has also been widely used.
Membrane Filtration Technology UF Membrane Filtration Technology (UF)
Ultrafiltration membrane (UF) is a membrane process between microfiltration and nanofiltration. It uses the principle of separation by sieving. The molecular weight cutoff for organics is from 3000 to 300,000 Dalton. It is suitable for macromolecules and small molecules. Separation, concentration and purification of molecular substances.
Early industrial ultrafiltration was applied to wastewater and sewage treatment. For more than 30 years, with the development of ultrafiltration technology, ultrafiltration technology has been involved in food, beverage processing, pharmaceutical industry, biological agents, Chinese medicine preparations, clinical medicine, printing and dyeing wastewater, food industry wastewater treatment, resource recovery, and environmental engineering. And many other fields.
Membrane Filtration Technology Nanofiltration Membrane Filtration (NF)
As the name implies, it refers to a membrane having “nano-sized pores”, which is between ultrafiltration and reverse osmosis, and has a molecular weight cut-off of 200 to 1000 Daltons for organic matter, and a 99% rejection rate for divalent ions, particularly anions. Suitable for the concentration and desalination of low molecular weight substances.
Nanofiltration is also suitable for the purification and softening of water, the removal of trihalomethane intermediates such as THM, low-molecular-weight organics and pesticides, sulfates and other harmful substances. Nanofiltration for the concentration and desalination of whey has also been used in the industry, can increase the concentration of lactose to 29%, and the ash removal rate of 90%.
Nanofiltration is also used in the following areas:
food industry
Beverage industry
biomedicine
Organic acid preparation
Fine Chemicals
Environmental protection industry
Membrane Filtration Technology Reverse Osmosis (RO)
Infiltration is the process of spontaneous flow of water from the dilute solution side through the semi-permeable membrane to the concentrated solution side. The concentrated solution is continuously diluted with the continuous flow of water. When the pressure of the water flowing to the concentrated solution is sufficient to prevent the water from continuing to flow in, the percolation is in equilibrium, that is, dynamic equilibrium is reached. When a pressure is applied to the concentrated solution and the pressure is greater than the osmotic pressure, the water in the concentrated solution will overcome the osmotic pressure and flow through the semi-permeable membrane to the dilute solution, resulting in a higher concentration of the concentrated solution. This process is penetration. The opposite process is called reverse osmosis.
Reverse osmosis separation technology is a modern advanced desalination technology for water treatment. Reverse osmosis membrane separation technology is based on the principle of reverse osmosis membrane
The specific features are as follows:
The solute and water are separated using low pressure as the membrane separation power under the condition that the phase transition does not occur at room temperature.
Reverse osmosis membrane separation technology has a wide range of impurity removal.
Higher salt rejection rate and water reuse rate can retain solute with particle size more than a few nanometers.
The separation device is simple, the operation, maintenance and self-control are simple, and the site is safe and sanitary.
Due to the advanced, high-efficiency and energy-saving features of reverse osmosis separation technology, it is mainly used for pharmaceutical water, pure water preparation and concentration of heat-sensitive substances. The main application areas include the following:
Food and beverage industry
Preparation of drinking water, pure water, ultrapure water
Seawater, brackish water desalination
Power, electronics, semiconductor industry water
Pharmaceutical industry process water, preparation water, water for injection, sterile heat-free pure water
Industrial process water, boiler water and cooling water
Membrane filtration technology other
In addition to the above four commonly used membrane separation processes, there are also dialysis, membrane reactors, membrane gas separation and so on.