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“The birth of a technology lies not in its discovery, but in its realization.”
I. From Laboratory Phenomena to Engineering Challenges (Late 19th–Mid 20th Century)
Since the mid-20th century, scientists and engineers around the world have explored the potential of synthetic membranes for seawater desalination and water purification.
Over the past six to seven decades, reverse osmosis (RO) and nanofiltration (NF) technologies have evolved from a niche laboratory concept into the dominant global solutions for liquid filtration and molecular separation.
In the previous chapter, we traced the path from Nollet’s 1748 pig bladder osmosis experiment to the 19th-century establishment of osmotic pressure theory.
That period marked humanity’s leap from observing natural osmosis to understanding the physics behind it.
Entering the 20th century, a new question emerged:
“Could this selective permeability exist not only in nature—but also in materials we create ourselves?”
After World War II, the United States faced growing freshwater shortages. Policymakers and scientists began to advocate for the large-scale development of seawater desalination technologies.
Under this initiative, the University of California, Los Angeles (UCLA) launched one of the world’s first desalination research programs, aiming to develop synthetic membranes capable of reverse osmosis under high-salinity conditions.
By the early 1950s, UCLA formally began its research into artificial semipermeable membranes for seawater desalination—marking the beginning of RO’s transformation from theory to engineering reality.
II. 1950s–1960s: From Concept to Feasibility — The Foundational Breakthroughs
1959: The Birth of Modern Reverse Osmosis
In 1959, C.E. Reid and E.J. Breton first reported the preparation of RO membranes using cellulose acetate (CA) polymers.[1]
Their membranes achieved a NaCl rejection rate of 98%, but exhibited extremely low water flux (<0.03 LMH/bar). This demonstrated that reverse osmosis was theoretically possible—yet still far from practical application.
That same year, two UCLA engineering graduate students, Sidney Loeb and Srinivasa Sourirajan, developed the first asymmetric (integrally-skinned) RO membrane using cellulose acetate.[2]
This structure—featuring a thin dense selective layer atop a porous support layer—achieved both high salt rejection (~99%) and greatly improved water permeability (~0.14 LMH/bar).
Their work, patented as U.S. Patent 3,133,132, marked the true birth of modern RO technology.
The UCLA team continued to optimize membrane structures, culminating in June 4, 1965, when the first large-scale RO demonstration plant was launched in Coalinga, California’s Central Valley.[3]
Operated by UCLA for several years, the facility proved the engineering feasibility of reverse osmosis for municipal water treatment.
This milestone not only brought seawater desalination into practical reality but also established the core design principle that remains foundational today:
“A thin dense selective skin supported by a porous sublayer.”
III. 1960s–1970s: Material Innovation and Industrial Expansion
1. The Rise and Limitations of Cellulose Acetate Membranes
Following the success at Coalinga, cellulose acetate (CA) membranes became widely adopted in seawater desalination and industrial water systems throughout the 1960s and 1970s.
However, these membranes had limited physical and chemical stability—operable only within pH 4–7 and below 35°C, requiring 350–450 psi operating pressure.
These constraints drove the search for more chemically robust and thermally stable alternatives.
2. 1971: The Emergence of Hollow Fiber Membranes
In 1971, Richter and Hoehn developed aromatic polyamide (PA) hollow-fiber membranes, offering significant advancements:
Improved chemical and biological stability;
Comparable NaCl rejection (~99%);
Greatly increased membrane area per module, enabling compact designs.
Although permeability remained modest, this innovation paved the way for large-scale RO module configurations.
3. Late 1970s: The Thin-Film Composite (TFC) Revolution
In 1979, John E. Cadotte of the North Star Research Institute—now regarded as one of the founding figures of modern commercial membrane technology—achieved another historic leap with the invention of the Thin-Film Composite (TFC) membrane.
Using interfacial polymerization (IP), he formed a polyamide active layer via the reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on a microporous polysulfone substrate reinforced by nonwoven polyester fabric.
The TFC design offered:
Higher water permeability ;
Superior salt rejection;
Exceptional chemical and thermal stability.
TFC membranes established the modern three-layer RO structure still used today:
Nonwoven polyester backing layer;
Polysulfone support layer;
Polyamide selective layer.
This architecture represented one of the greatest technological advances in desalination and water treatment—enabling scalable manufacturing and widespread commercial deployment.
Between 1950 and 1979, in less than three decades, reverse osmosis evolved from an experimental concept to a mature industrial technology.Each breakthrough was not merely a scientific achievement—but a step in humanity’s pursuit of making clean water more accessible.
The next phase would see RO technology soar further.As materials science, spiral-wound element design, and automation systems converged, reverse osmosis became the backbone of global desalination, industrial reuse, and residential purification.
Today, RO accounts for over 60% of the world’s installed desalination capacity.Scientists continued to drive material and process innovation—while industry turned those innovations into scalable, reliable water solutions.
In the next chapter, we will explore the commercialization and industrialization of RO, and how it transformed from an engineering breakthrough into a global water resource solution.
Information from：
[1] Reid C E, Breton E J. Water and ion flow across cellulosic membranes[J]. Journal of applied polymer science, 1959, 1(2): 133-143.
[2] Loeb S, Sourirajan S. Saline Water Conversion—II[J]. Advances in chemistry series, 1963, 38: 117.
[3] Reverse Osmosis: A History and Explanation of the Technology and How It Became So Important for Desalination
https://pmc.ncbi.nlm.nih.gov/articles/PMC11677704/?utm_source=chatgpt.com#B24-membranes-14-00259