Reverse osmosis RO | Nanofiltration NF | Ultrafiltration UF | Microfiltration MF | |
Membrane type | Asymmetric membrane | Asymmetric membrane | Asymmetric membrane | Symmetrical; asymmetric membrane |
Thickness film thickness | 150μm | 150μm | 150-250μm | 10-150μm |
Aperture | <0.002μm | <0.002μm | 0.2-0.02μm | 4-0.02μm |
Interception component | HMWC, LMWC | HMWC, monosaccharides, polysaccharides and polysaccharides, multivalent anions | Small molecule combination, protein, polysaccharide, virus | Granules, clay, bacteria |
Membrane material | Cellulose acetate (CA), film | Cellulose acetate (CA), | Ceramic, polysulfone (PSO), polyvinylidene fluoride (PVDF), cellulose acetate (CA), film | Ceramic, polypropylene (PP), polyvinylidene fluoride (PVDF) |
Membrane component type | Tubular, rolled, plate and frame | Tubular, rolled, plate and frame | Tubular, hollow fiber, roll, plate and frame | Tubular, hollow fiber, roll |
Operating pressure Mpa | 1.5-15 | 0.5-3.5 | 0.1-1.0 | <0.2 |
For microfiltration, the retention characteristics of the membrane are characterized by the pore size of the membrane. Generally, the pore size ranges from 0.1 to 10 μm, so the microfiltration membrane can separate large diameter bacteria, suspended solids, etc., and the ability to remove proteins. Very weak. It can be used as clarification, security filtration and air sterilization of general liquid.
For ultrafiltration, the retention characteristics of the membrane are characterized by the molecular weight cut off for standard organics. The molecular weight cutoff usually ranges from 1000 to 300,000, so ultrafiltration membranes can be used for macromolecular organics (eg proteins, bacteria), colloids, suspended solids. Separation is widely used in the clarification of feed liquids, the separation and purification of macromolecular organic matters, and the removal of heat sources.
For nanofiltration, the retention characteristics of the membrane are characterized by the rejection of standard NaCl, MgSO4, CaCl2 solutions, usually in the range of 60%-98%, and the corresponding molecular weight cutoff range is 100-1000, so the nanofiltration membrane It is possible to separate small organic substances and the like from water and inorganic salts to achieve desalination and concentration.
The reverse osmosis intercepts all ions, allowing only water to pass through the membrane, and the effluent is ion-free water. The reverse osmosis method can remove soluble metal salts, organic matter, bacteria, colloidal particles, and heat-generating substances, that is, it can trap all ions, and the reverse osmosis membrane has been widely used in producing pure water, demineralized water, and ion-free water.
Introduction to membrane separation technology
Clarification and purification technology - ultra/microfiltration membrane system
The membrane used for clarification and purification separation is mainly ultra/microfiltration membrane. Due to its wide range of diameters, it can be widely used in solid-liquid separation, classification of large and small molecular substances, pigment removal, product purification, oil and water. Separation and other processes.
Ultra/microfiltration membrane separation can replace the natural sedimentation, plate and frame filtration, centrifuge separation, solvent extraction, resin purification, activated carbon pigmentation and other processes in the traditional process.
The membrane separation modules that can be used for clarification and purification techniques are mainly: ceramic membranes, flat membranes, stainless steel membranes, hollow fiber membranes, wound membranes, tubular membranes.
Characteristics of clarification and purification by membrane separation:
1, can get absolute true solution, product stability is good;
2. High filtration and separation yield;
3. Good separation effect, high product quality and low operating cost;
4. Shorten the production cycle and reduce production costs;
5. The process does not need to add chemicals, solvent solvents, and does not bring in secondary pollutants;
6, easy to operate, occupying a small area, low labor costs;
7. It has good expandability and is easy to realize the demand for industrial expansion;
8, the equipment can run automatically, stability, and easy maintenance.
Concentrated purification technology - nanofiltration membrane system
The membrane separation technology mainly uses a nanofiltration membrane with a molecular weight cut-off of 100-1000 Dal in the concentration and purification process. The main characteristic of the nanofiltration membrane is that the retention performance of divalent ions, functional sugars, small molecular pigments, peptides and the like is higher than 98%, and 30-50% for some monovalent ions, small molecules, acids and bases, alcohols, etc. The permeation performance is often applied to the classification of solute, the elution of low molecular substances in solution, the adjustment of ionic components, the separation, refining and concentration of substances in solvent systems.
Nanofiltration membrane separation technology is often used to replace the freeze-drying, thin film evaporation, ion exchange desalination, resin process concentration, neutralization processes in traditional processes. The membrane purification module can be mainly used for the concentrated purification technology: a roll film, a flat film, and a tubular film.
Advantages of concentrated purification by nanofiltration membrane separation technology:
1. The energy consumption is extremely low, saving the cost of the concentration process;
2. The process has no chemical reaction, no phase change, no other impurities and decomposition and denaturation of the product;
3. At the normal temperature, the purpose of concentration and purification is achieved, without causing damage to the active ingredients, and the process yield is high;
4, can completely remove the salt in the product, reduce product ash, improve product purity;
5. Recoverable acid, alkali, alcohol and other substances in the solution;
6, the device structure is simple and compact, and the floor space is small;
7, easy to operate, can achieve automated work, good stability and easy maintenance.
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