Another Way to Desalinate Water Is Discovered
Chemical engineer Kamalesh Sirkar, PhD, a professor at New Jersey Institute of Technology (NJIT) and an expert in membrane separation technology, is leading a team of researchers to develop a breakthrough method to desalinate water. Sirkar, who holds more than 20 patents in the field of membrane separation, says that using his technology, engineers will be able to recover water from brines with the highest salt concentrations. The Bureau of Reclamation in the Department of Interior is funding the project.
“Our process will work especially well with brines holding salt concentrations above 5.5 percent,” Sirkar says. Currently, 5.5 percent is the highest percentage of salt in brine that can be treated using reverse osmosis.
“We especially like our new process because we can fuel it with low grade, inexpensive waste heat,” Sirkar says. “Cheap heat costs less, but can heat brine efficiently.”
The science behind Sirkar's membrane distillation process is simple. The inexpensive fuel heats the water, forcing it to evaporate from the salt solution. The cleansed vapor then travels through nano-sized pores in the membrane to wind up condensed in the cold water on the membrane's other side.
“The basic principles of membrane separation have been known for a long time,” says Sirkar. “Intestines in animals and humans are semi-permeable membranes. Early experiments to study the process of separation were performed by chemists using samples of animal membranes.”
Today, membrane separation processes depend on the design of the membrane and the membrane module. The size of the pores often is key to determining which molecular components in either a liquid or gas form will pass through the membrane. Typically, molecules flow from a region of high to low concentration. Pressure or concentration differences on both sides of the membrane cause the actual separation to occur. As pore size decreases, the membrane's efficiency and selectivity increases. Membrane separation processes are used in biomedical, biotechnology, chemical, food, petrochemical, pharmaceutical and water treatment industries to separate/purify/concentrate liquid solutions or cellular suspensions or gaseous mixtures.
Typically, Sirkar works with miniscule membranes, smaller in size than nanometers - a nanometer is one billionth of a meter.
Sirkar has been leading the effort in membrane separations and biotechnology at NJIT since 1992. He is the director for the Center for Membrane Technologies at NJIT and is the Foundation Professor of Membrane Separations.
Although Sirkar has no crystal ball, he envisions many future applications for his process. “Desalinating seawater to stimulate economic development and create potable water always has an attentive audience,” he says.