Forward osmosis-looking for new technology of water treatment desalination

As a potential new technology of water purification and seawater desalination, forward osmosis is being studied theoretically and practically from many angles in the world. Forward osmosis and reverse osmosis are a pair of interactive methods. Foreign 1976 has an original attempt of liquid-liquid system, and domestic 1992 invented the forward osmosis (pressureless) adsorption osmotic desalination of liquid-solid system (cn92110710.2). It was not until about 10 years later that we followed the international trend again and started the standard imitation and replication mode. In 2008, there was a summary report. With the rapid development of science and technology, pressure-driven reverse osmosis membrane separation technology (RO) has made great innovations and improvements in membrane, membrane module, equipment and technology, but people are more and more aware of the limitations of RO technology in the field of energy conservation and environmental protection. As far as seawater desalination is concerned, RO technology can be considered to be close to the peak of development. Therefore, foreign countries have carried out the related research on "Forward Osmosis Membrane Separation Technology (FO)", and achieved certain results, which have been applied in seawater desalination, sewage treatment, food processing, medicine and other fields, especially "Pressure Delayed Osmosis (FRO) seawater power generation", which is a promising clean and renewable energy development technology J, while domestic research on FO is less concerned, and there are not many related researches and papers. Although, in the 1990s, China had a creative invention "seawater desalination by pressureless adsorption and infiltration" (CN92110710.2).

Forward osmosis separation technology has been applied for a long time. A long time ago, people used salt to store food for a long time, because in a high-salt environment, most bacteria, molds and pathogenic bacteria would be dehydrated to death or temporarily lose their activity. Nowadays, people have begun to use forward osmosis membrane separation technology to study seawater desalination, industrial wastewater treatment, landfill leachate treatment and so on. The food industry uses forward osmosis membrane separation to concentrate beverages in the laboratory; The life support system in emergency rescue uses forward osmosis membrane separation technology to produce fresh water. With the development of materials science, forward osmosis technology has been applied to the controlled release of drugs in human body. (11990s)

Non-pressurized adsorption infiltration seawater desalination method, or "forward osmosis method", is to let water penetrate into a solution or solid with super absorbent or salt concentration even exceeding seawater through a porous membrane without external pressure, but the special salt extract in the solution is easy to evaporate without increasing too much heat (the energy ratio of thermal energy to reverse osmosis pressurization? )。 Divided into two directions: solid salt and liquid salt. Desorption of solid salt consumes less energy.

Seawater desalination technology: pressureless adsorption and infiltration seawater desalination method (CN 92110710.2)1992: invented by Deng Yu in 1990s and included in American Chemical Abstracts.

The other two methods are innovative and improved in membrane structure: the principle and function of water softener: according to the principle of ion exchange, that is, Na+ is used to exchange Mg2+Ca2+, so that the hardness in water is reduced to below 70 mg/L to become soft water. The main function of this water treatment equipment is to remove alkali and scale from water.

Advantages and disadvantages of water treatment equipment of water softener;

Advantages: descaling, good water-alkali effect, large flow and basically no reduction of water pressure. The water produced by the water treatment equipment of the water softener has strong cleaning ability and strong washing, shower, beauty and skin care effects; It can also reduce energy consumption. At the same time, it also saves washing supplies and reduces the intensity of housework. The water produced by the water treatment equipment of the water softener is most suitable for domestic use.

Disadvantages: the water treatment equipment of the water softener can't remove bacteria, viruses and organic matter, so it can't be directly drunk; Salt needs to be consumed in the regeneration process; And a certain amount of wastewater is generated.

Application fields of softened water: bathroom, kitchen, laundry, heating, boiler, water supply for central air conditioning equipment, beauty care and other fields. Principle and function of water purifier: PP cotton, activated carbon, RO membrane and other filter elements are used for five or more stages of filtration, among which RO membrane is the core, and RO membrane is the filter element with the highest filtration accuracy at present. The produced water is pure water and can be directly drunk.

Advantages and disadvantages of water treatment equipment of pure water machine;

Advantages: the water treatment equipment of the water purifier has high filtration accuracy and is suitable for all kinds of water quality. Pure water is pure water with good taste and does not contain any impurities.

Disadvantages: the water treatment equipment of pure water machine produces less water every day, which can only solve drinking and cooking; The first three filter elements have a short service life and need to be replaced regularly; Not suitable for long-term direct drinking, especially for children and the elderly.

Ultrafiltration machine is the mainstream product in water treatment equipment of water purifier, with high precision, good purification effect, long service life of filter element and automatic cleaning of filter element.

Principle and function of water purifier: Using 0.0 1 micron ultrafiltration membrane separation technology, it can effectively remove harmful substances such as sediment, rust, suspended solids, colloid, bacteria, viruses, macromolecular organic substances and so on.

Advantages and disadvantages of water treatment equipment of water purifier;

Advantages: the water treatment equipment of the water purifier has high filtration accuracy; Pure water is close to mineral water and can be directly drunk raw; Large flow; The filter element has long service life; Automatic cleaning filter element; Do not need electricity; Don't waste water.

Disadvantages: the water purifier water treatment equipment descaling, water and alkali effect is poor, suitable for areas with moderate hardness; A single ultrafiltration machine can not completely remove the odor in water, and the water quality tastes poor; It is troublesome to change the core, and it is impossible to completely remove heavy metals from the water. The nanofiltration membrane water treatment machine is a slightly loose water treatment machine with nanofiltration membrane as the main component, similar to the reverse osmosis membrane. Nanofiltration membrane is a charged membrane, which can carry out electro-adsorption, partially remove F ions with high electrical properties, and has a nano-dense pore size, so that macromolecules cannot pass through, free water molecules partially pass through, NaCl partially passes through, and less calcium ions and magnesium ions can pass through. It includes the advantages of the above water processor and avoids secondary water treatment.