Researchersat the UCLA Henry Samueli School of Engineering and Applied Science todayannounced they have developed a new reverse osmosis (RO) membrane that promisesto reduce the cost of seawater desalination and wastewater reclamation.
Reverseosmosis desalination uses extremely high pressure to force saline or pollutedwaters through the pores of a semi-permeable membrane. Water molecules underpressure pass through these pores, but salt ions and other impurities cannot,resulting in highly purified water.
Thenew membrane, developed by civil and environmental engineering assistantprofessor Eric Hoek and his research team, uses a uniquely cross-linked matrixof polymers and engineered nanoparticles designed to draw in water ions butrepel nearly all contaminants. These new membranes are structured at thenanoscale (the width of human hair is approximately 100,000 nanometers) tocreate molecular tunnels through which water flows more easily thancontaminants.
Unlikethe current class of commercial RO membranes, which simply filter water througha dense polymer film, Hoek's membrane contains specially synthesizednanoparticles dispersed throughout the polymer— known as a nanocompositematerial.
"Thenanoparticles are designed to attract water and are highly porous, soaking upwater like a sponge, while repelling dissolved salts and other impurities,"Hoek said. "The water-loving nanoparticles embedded in our membrane also repelorganics and bacteria, which tend to clog up conventional membranes over time."
Withthese improvements, less energy is needed to pump water through themembranes. Because they repel particlesthat might ordinarily stick to the surface, the new membranes foul more slowlythan conventional ones. The result is a water purification process that is justas effective as current methods but more energy efficient and potentially muchless expensive. Initial tests suggest the new membranes have up to twice theproductivity — or consume 50 percent less energy — reducing the total expenseof desalinated water by as much as 25 percent.
"Theneed for a sustainable, affordable supply of clean water is a key priority forour nation's future and especially for that of
Acritical limitation of current RO membranes is that they are easily fouled —bacteria and other particles build up on the surface and clog it. This foulingresults in higher energy demands on the pumping system and leads to costlycleanup and replacement of membranes. Viable alternative desalinationtechnologies are few, though population growth, over-consumption and pollutionof the available fresh water supply make desalination and water reuse ever moreattractive alternatives.
Withhis new membrane, Hoek hopes to address the key challenges that limit morewidespread use of RO membrane technology by making the process more robust andefficient.
"Ithink the biggest mistake we can make in the field of water treatment is toassume that reverse osmosis technology is mature and that there is nothing moreto be gained from fundamental research," Hoek said. "We still have a long wayto go to fully explore and develop this technology, especially with theexciting new materials that can be created through nanotechnology.
Hoekis working with NanoH2O, LLP, an early-stage partnership, todevelop his patent-pending nanocomposite membrane technology into a new classof low-energy, fouling-resistant membranes for desalination and water reuse. Heanticipates the new membranes will be commercially available within the nextyear or two.
"Weas a nation thought we had enough water, so a decision was made in the 1970s tostop funding desalination research," Hoek said. "Now, 30 years later, there isrenewed interest because we realize that not only are we running out of freshwater, but the current technology is limited, we lack implementation experienceand we are running out of time. I hope the discovery of new nanotechnologieslike our membrane will continue to generate interest in desalination researchat both fundamental and applied levels."
Establishedin 1945, the UCLA Henry Samueli School of Engineering and Applied Scienceoffers 28 academic and professional degree programs, including aninterdepartmental graduate degree program in biomedical engineering. Rankedamong the top 10 engineering schools at public universities nationwide, theschool is home to six multimillion-dollar interdisciplinary research centers inspace exploration, wireless sensor systems, nanotechnology, nanomanufacturingand nanoelectronics, all funded by federal and private agencies.
Thefirst viable reverse osmosis membrane was developed and patented by UCLAEngineering researchers in the 1960s.
Theschool also is home to the