1. Granular filter media: the main force of cost-effective filtration
Granular filter media is the most widely used type of filter media, which mainly purifies fluids through physical adsorption and interception. Common types include:
1). Quartz sand: particle size 0.5-1.2mm, strong acid and alkali resistance, low cost, often used for drinking water pretreatment and sewage treatment (refer to "Industrial Water Treatment Technology Manual").
2). Activated carbon: divided into coal and coconut shell, with a porosity of up to 500-1500m²/g (data source: US Environmental Protection Agency EPA), can adsorb organic matter and heavy metals, suitable for water purifiers and air purification.
3). Anthracite: low density (1.4-1.6g/cm³), combined with quartz sand to improve filtration efficiency, mostly used in double-layer filter tanks.
The disadvantage of granular filter media is that it is easy to compact and needs regular backwashing, with a lifespan of about 3-5 years.
2. Fiber filter material: the choice of efficient and fine filtration
Fiber filter material is made of flexible material with high filtration accuracy. Representative types are:
1). Polypropylene fiber: corrosion-resistant, can be made into PP cotton filter element, pore size 1-10μm, used for pre-filtration of household water purifiers.
2). Glass fiber: high temperature resistant (≤280℃), often used in industrial waste gas treatment, such as power plant desulfurization system.
3). Ceramic fiber: combined with particle and fiber characteristics, strong impact resistance, suitable for high viscosity liquid filtration in the chemical industry.
The disadvantage of fiber filter material is low strength, easy to break after long-term use, and needs to be replaced regularly.
3. Membrane filter material and emerging materials: advanced technology application
1). Membrane filter material:
- Microfiltration membrane (0.1-10μm): remove bacteria and suspended matter, such as end filtration of household water purifiers.
- Ultrafiltration membrane (0.01-0.1μm): can intercept viruses and is widely used in medical dialysis (refer to the "Membrane Separation Technology Application Guide").
2). Porous ceramic filter media: High temperature resistant (>1000℃), corrosion resistant, but high cost, mostly used for high temperature gas purification in the metallurgical industry.
3). New composite filter media: such as graphene modified filter media, the adsorption capacity is increased by more than 3 times ("Nature Materials" 2022 research), but it has not yet been commercialized on a large scale.
4. How to choose the right filter media?
Comprehensive evaluation based on filtration objectives (such as turbidity removal, sterilization, decolorization), fluid properties (pH value, temperature) and cost budget. For example:
- The combination of "quartz sand + activated carbon" is commonly used in water plants;
- Ultrapure water in the electronics industry needs to be matched with membrane filter media;
- Ceramic filter media is preferred for high temperature flue gas treatment.
In the future, as environmental protection standards are improved, high-efficiency and long-life composite filter media will become the focus of research and development.