The invention and large-scale application of reverse osmosis is a landmark achievement in the development of modern water treatment technology. As an advanced membrane separation technology developed since 1950s, reverse osmosis has been widely used in seawater desalination, brackish water desalination, domestic water purification and wastewater reuse. In 2018, the world's desalinated water produced by reverse osmosis technology has reached more than 11 billion tons, which can be used by 320 million people. In the past 70 years, many important scientists, entrepreneurs and a large number of technology companies have jointly performed a brilliant development of reverse osmosis technology.

       We know that doctors often use normal saline when giving patients infusion, which is 0.9% sodium chloride solution. This concentration is equivalent to the concentration of human body fluid, so it will not cause harm to human body due to significant penetration on both sides of cell membrane after infusion. Although the phenomenon of infiltration occurs every day in our bodies, it was not until 1748 that French physicist Jean Antoine nollet first discovered it from a scientific point of view.

       Nolai is a great man who loves science. It is said that he also demonstrated the Leiden bottle discharge experiment to Louis XV. He used the pig bladder as a semi permeable membrane to separate two different concentrations of ethanol aqueous solution, thus observed the penetration phenomenon through the experiment. In 1886, a Dutch scientist proposed the osmotic pressure calculation of dilute solution by summarizing the experimental data. If you've studied physical chemistry, you may remember that this man's name is Van & lsquot Hoff.

       In the 1950s, the Kennedy administration began to place its hope on desalination in order to solve the problem of water shortage in some arid areas of the United States and the problem of national overuse of groundwater. In 1952, the United States Congress passed the saline water conversion act. In 1953, it began to fund desalination technology research, although the fund was only 175000 US dollars in that year. In 1955, the U.S. Department of the interior set up the office of saline water (OSW) to coordinate the research of various desalination technologies. In 1970, the annual funding for OSW increased to about $26 million.

       In 1949, Gerald Hassler of the University of California, Los Angeles (UCLA) and others first started the study of membrane desalination. In 1950, Hasler described the concept of "salt repelling osmotic membrane" in an internal report of UCLA, but his follow-up research was a bit biased. In August 1956, Hasler first coined the word "reverse osmosis" in another UCLA internal report.

       Around 1954, Professor Charles Reid's team at the University of Florida, funded by OSW, also began to study desalination osmotic membrane. They evaluated many commercial membranes found in the market, and found that cellulose acetate membrane has good semi permeability, salt rejection rate is more than 99%, and water permeability coefficient is 0.00012m3/m2 & middot; d· atm。 Although the permeability of membrane is more than two orders of magnitude lower than that of modern commercial membrane, which has no commercial value, they used synthetic membrane for the first time to verify the concept of pressure driven reverse osmosis membrane desalination. In April 1957, reed and his colleague E. J. Breton used the word "ro" in a report to OSW.

       Interestingly, in the era of no Internet and Moments, although the two universities were studying desalination membrane, they did not know each other until they met at a seminar organized by OSW in November 1957.

       The next question is how to improve the permeability of membrane to obtain practical value?

       In 1956, in addition to the Hasler research group, the research group of Professor Samuel yuster also carried out membrane desalination research with the support of OSW. Srinivasa sourirajan, 33, an Indian scientist, was first involved in the study. Although they are not aware of the research being carried out by xiaoruide research group, they have the same ideas and adopt a similar pressure driven research route. In the summer of 1958, Sidney Loeb, 41, a Jewish scientist, joined the group.

       Solirakin and Loeb's first work was also to screen commercial films. In the process, they found that a commercial cellulose acetate ultrafiltration membrane could be desalted by heat treatment. They also found unexpectedly that the orientation of the membrane in the test was crucial, and the effect of one side facing the feed liquid was significantly better than that of the other side.

       The salt rejection rate of heat-treated cellulose acetate membrane is 92%, and the water permeability coefficient is 0.00095m3/m2 & middot; d· ATM, much higher than other films. More importantly, they realized that the asymmetry of the membrane structure has a great impact on the performance of the membrane, and reducing the effective thickness of the membrane is the key. In order to further improve the performance of the membrane, the two scientists decided to make their own membrane.

       In 1959, Loeb and solirakin made a series of explorations, using cellulose acetate acetone water magnesium perchlorate as raw materials to prepare membrane casting solution at the ratio of 22.2:66.7:10.0:1.1, and optimized the temperature, evaporation time, heat treatment and other factors to prepare the synthetic reverse osmosis membrane with asymmetric structure for the first time. The so-called asymmetric structure simply means that a membrane is composed of two parts, the support layer is loose in structure, and the separation layer is dense in structure. This membrane was later called L-S membrane.

       The salt rejection rate of lop and soliragin asymmetric membrane is 99%, and the water permeability coefficient is 0.0048 m3 / m2 & middot; d· ATM, which is five times as much as ultrafiltration heat treatment membrane, is almost the same order of magnitude as modern commercial reverse osmosis membrane. The membrane also has good mechanical stability. This breakthrough provides the most important technical basis for the reverse osmosis technology to eventually move towards large-scale engineering application. Since then, reverse osmosis membrane technology has entered a period of rapid development, and gradually into commercial application.

       In 1965, the world's first commercial reverse osmosis plant was built in the small town of Coalinga, California, with Lobb's participation and guidance, producing 5000 gallons of water per day. This indicates that the dream of large-scale production of drinking water from seawater at an acceptable cost has become a reality. Soon, new pilot lines appeared in many places of California, which promoted the rapid development of the technology.

PART 3

Successful commercialization

       The L-S membrane invented by Loeb and solirakin in 1959 is a flat membrane, so the early membrane module directly borrowed the plate and frame structure of industrial filtration equipment. Loeb et al. Also developed tubular reverse osmosis membranes with a diameter of 1-3cm and applied them to the coringa plant. However, both the plate and frame type and the tube type have some defects, such as complex assembly, small membrane area per unit volume and so on.

       Around 1965, Dow Chemical and DuPont invested in the development of hollow fiber reverse osmosis membrane, which may be related to their familiarity with the textile industry.

       In 1966, H. I. Mahon of Dow Chemical designed the first set of hollow fiber membrane spinning system, developed hollow fiber reverse osmosis membrane based on cellulose triacetate material, and applied for the first patent (us3228877). They use concentric capillary spinneret, the inner diameter of outer hole is 400 μ m, the outer diameter of inner hole is 200 μ m, and the inner diameter of inner hole is 100 μ M.

       In 1971, DuPont applied for the patent of hollow fiber reverse osmosis membrane module based on polyamide material (us3567632). In 1979, another company with textile background was also developing hollow fiber reverse osmosis membrane modules, which was Toyobo.

       Hollow fiber reverse osmosis membrane module has a high packing density, but it is not the mainstream of reverse osmosis membrane module because of its fine wire diameter, uncontrollable hydraulic state and easy to produce fouling. This is also the reason why Dow Chemical later turned to roll up membrane. Toyo spinning is the only one that still keeps cellulose acetate hollow fiber reverse osmosis membrane production line.

       If 1959 was a milestone year in reverse osmosis technology, 1963 was a year in which reverse osmosis successfully sowed seeds in commercialization.

       In 1963, the North Star Research Institute in Minneapolis, Minnesota, also carried out desalination technology research under the support of OSW. In 1967, John E. Cadotte of Polaris Institute invented microporous polysulfone support membrane. In the following years, he developed a variety of non cellulose acetate composite membranes. But his passion for reverse osmosis is not limited to research.

       In 1977, cardot and three others founded filmtec. In 1979, cardot applied for the patent of the first reverse osmosis membrane prepared by interfacial polymerization in the world (us4277344). Interfacial polymerization makes the support layer and separation layer of reverse osmosis membrane can be optimized respectively in the preparation process, so as to further improve the performance of the membrane, which is called thin-layer composite membrane (TFC). Interfacial polymerization has also become the standard preparation process of modern commercial reverse osmosis membrane.

       In 1985, Dow Chemical gave up the hollow fiber reverse osmosis membrane and wholly acquired filmtec company. This is the origin of the famous Dow membrane. Today, Dow reverse osmosis membrane products still use the filmtec trademark. In 2017, Dow Chemical, which once cherished each other on hollow fiber reverse osmosis membrane, merged with DuPont.

       It was around 1963 that Donald T. Bray, a 41 year old World War II veteran, began to study reverse osmosis membranes. He joined general atomics five years ago. In 1965, Bray applied for the world's first multi diaphragm coiled reverse osmosis membrane module patent (us3417870), which established the basic structure of the current universal coiled reverse osmosis membrane module.

       Ge atomic's reverse osmosis membrane business later evolved into fluid systems. In 1998, fluid systems was acquired by Koch membrane systems, which is the origin of Koch membrane.

       But the story of Bray is not over. In 1967, he left general atomics and founded desalination systems. Desalination systems company has done a lot of work in membrane production and membrane module rolling machine, and become a well-known reverse osmosis membrane manufacturer in the industry. Its products also include nanofiltration membrane with unique multilayer structure.

       Also in 1963, Dean Spatz, a sophomore at Dartmouth College, was busy with his engineering project. They wanted to design a proper treatment method for the poor drinking water of South Dakota residents, and he decided to use the new reverse osmosis technology and successfully built a prototype.

       Spatz became interested in reverse osmosis technology and took it as the subject of his undergraduate and master's theses. In 1965, Spatz was funded by OSW. It is said that during his master's degree, Spatz also invited solirakin as a consultant.

       In 1968, Ms. Spatz joined a Miami based company and was sent to Minneapolis to develop reverse osmosis business. In 1969, Spatz set up his own company because of the lack of funds promised by the company. This is the birth of Osmonics.

       In 1996, Bray, 84, sold desalting systems to Osmonics. In 2002, Ge acquired Osmonics at a price of 250 million US dollars, which is the origin of Ge membrane. Now we know where the famous Ge nanofiltration membrane comes from. In 2017, GE's reverse osmosis membrane business was sold to Suez water with Ge water treatment at a price of US $3.4 billion.

       In 1963, it became another well-known company in the field of reverse osmosis membrane. Hydranaulics was also established in California. In 1970, heidneng company officially entered the field of reverse osmosis membrane. According to the public information, heidneng and filmtec have also forged a dispute over cadot's interface aggregation patent. In 1987, heidneng was officially acquired by Nitto denko.

       In Japan, another company has been focusing on reverse osmosis technology for a long time, and this is Toray. In 1968, Toray began to study cellulose acetate reverse osmosis membrane. In 1978, its first low-pressure RO membrane product was launched. In 1991, its seawater RO membrane components were put on the market. In 2009, tbmc joint venture was established in Beijing.

       In addition to these old manufacturers from 1960's or 1970's, backwaves in the field of reverse osmosis membrane also emerge one after another.

       In 1990, a subsidiary of SamSung group in South Korea began to study reverse osmosis membrane technology. In 1995, its household reverse osmosis membrane began to export. In 1997, the company changed its name to the Saehan group. In 2001, its desalination membrane with high desalination rate was put on the market. In 2008, the company changed its name to Woongjin chemical. Xiongjin chemical's reverse osmosis membrane product is commonly known as Shinan membrane. In early 2020, Toray acquired a 56.2% stake in Xiongjin chemical.

       In 2005, nanoh2o company was founded in Los Angeles, California. In 2014, South Korea's LG Chemical acquired nanoh2o with us $200 million. In recent years, the company has gradually stepped into the ranks of mainstream RO membrane suppliers.

       So far, several of the most famous reverse osmosis membrane manufacturers in the world have appeared. According to the statistics of global water information (GWI), during 2012-2017, 76% of RO membranes in large-scale reverse osmosis systems with a capacity of more than 50000 tons / day came from Toray, Dow, heidneng and LG Chemical, accounting for 28%, 21%, 17% and 10% respectively.

       It can be seen from the above that the 1960s and 1970s were the time when the key technologies of reverse osmosis abroad were concentrated and made breakthroughs. At that time, the research foundation in China was weak, and it was in a special historical period, so the research of reverse osmosis technology in the same period was significantly backward. But through timely technology introduction and independent research and development, we have accumulated rich application experience and preliminary technical achievements, which has laid a very important technical and talent foundation for the comprehensive progress of reverse osmosis membrane technology and even water treatment technology in China.

       In 1966, the Department of chemistry of Shandong Ocean University, the first Institute of State Oceanic Administration, Qingdao Institute of Oceanology, Chinese Academy of Sciences and other units began to study reverse osmosis technology and develop asymmetric cellulose acetate membrane. In 1967, the State Science and Technology Commission and the State Oceanic Administration organized a national sea water desalination battle. Qingdao and Beijing mainly carried out the research on reverse osmosis. Some of the participants in the battle later gathered in the second Institute of the ocean administration and set up the desalination research laboratory. In 1975, the second Institute of ocean administration and other units developed a disc plate cellulose acetate reverse osmosis device with a daily fresh water output of 1.7 tons. The desalination Research Laboratory of the second Institute of ocean administration has gradually developed into today's Hangzhou water treatment technology center.

       Lanzhou Institute of glaciers, permafrost and deserts, Chinese Academy of Sciences, located in the northwest brackish water area, is one of the earliest research units engaged in reverse osmosis technology in China. In 1974, they developed a cellulose acetate casing type reverse osmosis unit with a daily output of 10 tons. Lanzhou Institute of membrane technology team has gradually developed into today's Gansu Academy of membrane science and technology.

       In December 1974, in order to solve the problem of serious water shortage in Tianjin and other places, the national science and technology leading group organized and held a national conference on desalination science and technology in Beijing, and formulated the national desalination science and technology development plan for 1975-1985. The second Institute of ocean administration, Lanzhou Institute of glacial permafrost desert, Beijing Institute of environmental protection, Tianjin Institute of synthetic materials, Institute of Oceanography, Chinese Academy of Sciences and other units participated in the research of reverse osmosis technology.

       In the middle and late 1970s, some domestic units followed the international technology development trend, carried out the research on hollow fiber and roll reverse osmosis components, and realized the preliminary industrialization in the 1980s. In the mid-1980s, the development of composite membrane was started again. After the successful pilot scale of the seventh and eighth five year plan, the reverse osmosis membrane technology in China began to move from laboratory research to industrial scale application.

       China began to apply reverse osmosis technology in the late 1980s, and its application scale has increased rapidly since then. In 1988, 600 pieces of 8-inch films were sold in the Chinese market. In 1990, Daya Bay nuclear power station built the first reverse osmosis desalination plant in China, with a daily fresh water output of 200 tons. In 1999, Dalian built the first 1000 t / D reverse osmosis desalination plant. In 2005, Qingdao built the first set of 10000 t / D reverse osmosis desalination plant. In 2009, Tianjin built its first 100000 t / D RO desalination plant.

       By the end of 2018, 121 reverse osmosis desalination projects have been completed in China, with a desalination capacity of 825641 tons / day. However, more reverse osmosis membranes and systems are used in power generation, petrochemical, coal chemical and other industrial users in China. In 2014, 1.8 million reverse osmosis membranes were used in factories in China, and the water production reached 27 million tons / day.

       In the past 20 years, the domestic capacity of reverse osmosis membrane in China has been constantly improving. In 2000, China's first domestic reverse osmosis membrane Manufacturer & mdash& mdash; Huitong source was established in the South Huitong science and technology park. In 2002, Huitong fountainhead began mass production and sales of polyamide composite reverse osmosis membrane components. In 2006, Huitong source changed its name to Guiyang times Huitong; In 2010, it was renamed time Wharton Technology Co., Ltd.

       In addition to time Wharton and blue star Toray, many domestic reverse osmosis membrane manufacturers, such as Hunan Qinsen and Shandong Jiuzhang membrane, have also appeared one after another.

       The invention and large-scale application of reverse osmosis technology is a great scientific achievement in human history. The initial impetus of this invention came from the human dream of asking for water from the sea. The nearly 70 years of development history of reverse osmosis technology perfectly tells the story of human beings using science and technology to turn this dream into reality. Looking back on this period of history, it should be said that the U.S. government's special funding program has played a great role in promoting the early development of reverse osmosis technology, and to a large extent established the U.S. leading edge in reverse osmosis technology. From the perspective of innovation chain, Hasler, Reid and other pioneers put forward correct ideas and established the right research direction of reverse osmosis technology; Loeb and solirakin's pioneering work filled the biggest technical gap between the concept and practice of reverse osmosis; Cardot, Bray, Spatz and others have both the qualities of scientists and entrepreneurship, and have made great contributions in promoting reverse osmosis to realize the leap from technology to product.

       From the perspective of R & D, the research work of Lobb and solirakin in the synthesis of the first asymmetric reverse osmosis membrane is excellent, but not magical. Loeb reviewed the experience in detail in 1980. They start from verifying the concept and finding the gap, then analyze the reason and put forward the hypothesis, finally they succeed. There are not only the factors of luck and inspiration, but also the inspiration from the literature, and the helpful suggestions from colleagues, just like the stories around us.

       In recent years, the application of reverse osmosis technology is more and more extended to the field of industrial water treatment, especially in the field of industrial wastewater reuse and zero discharge treatment. On the one hand, it puts forward higher requirements for RO membrane in anti pollution and anti cleaning, on the other hand, it also puts forward higher expectations for the concentration capacity of ro. Disc tube reverse osmosis (DTRO), high pressure reverse osmosis (hpro), high salt reverse osmosis (hsro) and other new reverse osmosis membrane products and processes came into being.

       Looking forward to the future, reverse osmosis technology will continue to expand its application fields and scale, and may even overturn the technical framework established 40 years ago. With the accumulation of technology, talents and experience, the technical barriers between domestic reverse osmosis membrane and imported brands are disappearing, and it is only a matter of time before domestic membrane completely replaces imported membrane. In addition, China is the world's most important industrial wastewater recycling and zero discharge market, which provides favorable conditions for domestic reverse osmosis membrane technology to surpass technology in the future.

Data sources：E20 Network Solid waste network, MYM Space