A TEAM from Cornell University has developed a cheaper, more efficient sugar-based water filter that strains contaminants and rids rivers and lakes of estrogen, bisphenol A (BPA), a toxic byproduct from plastics, and other pollutants.
This technology could conceivably rid Laguna de Bay, the country’s biggest lake at 94,900 hectares, of pesky urine-derived estrogen that feminizes male tilapia, carp and other fish species, and clean it of BPA, lead and mercury.
Results of the research conducted by Dr. Michelle Grace Paraso of the University of the Philippines at Los Baños and published by the Southeast Asian Regional Center for Graduate Study and Research in Agriculture confirmed the feminization of fish in the lake, which threatens tilapia breeders who want more male tilapia that grow bigger and faster, unless people living around the lakeshore stop using Laguna de Bay as a septic tank.
Laguna de Bay supplies the entire National Capital Region of 70 percent of its fish demand, with much of the fish contaminated with lead and mercury as confimed by a study conducted by Dr. Victorio Molina of the UP College of Public Health in 2011.
In an abstract published by Nature magazine on December 21, Dr. William R. Dichtel, lead author; Alaaeddin Alsbaiee, Brian J. Smith, Leilei Xiao,Yuhan Ling and Damian E. Helbling said, “The global occurrence in water resources of organic micropollutants, such as pesticides and pharmaceuticals, has raised concerns about potential negative effects on aquatic ecosystems and human health. Activated carbons are the most widespread adsorbent materials used to remove organic pollutants from water, but they have several deficiencies, including slow pollutant uptake and poor removal of many relatively hydrophilic micropollutants.”
Dichtel said they worked on insoluble polymers of -cyclodextrin, an inexpensive, sustainably produced macrocycle of glucose from sugar that are known to encapsulate pollutants.
“Here we crosslink-cyclodextrin with rigid aromatic groups, providing a high-surface-area, mesoporous polymer of -cyclodextrin. It rapidly sequesters a variety of organic micropollutants with adsorption rate constants 15 to 200 times greater than those of activated carbons and nonporous -cyclodextrin adsorbent materials. In addition, the polymer can be regenerated several times using a mild washing procedure with no loss in performance. Finally, the polymer outperformed a leading activated carbon for the rapid removal of a complex mixture of organic micropollutants at environmentally relevant concentrations,” Dichtel said.
“These findings demonstrate the promise of porous cyclodextrin-based polymers for rapid, flow-through water treatment,” he said.
The material is comprised of the -cyclodextrin polymer that has long strands of repeating molecules and a six-carbon ring called tetrafluoroterephthalonitrile.
“Cyclodextrins are sugar molecules arranged in a ring such that the sugar’s hydroxyl groups are perpendicular to the plane of the ring. Their binding power has been exploited before, for example, to trap smelly molecules in the odor-neutralizing spray known as Febreeze,” David Schultz of Science on December 23 wrote.
The team heated the two components in a solution of potassium carbonate and tetrahydrofuran to link the two types of molecules together in stiff chains and create a porous 3D lattice.
Testing their product, Dichtel said the porous cyclodextrin polymers reached 95 percent of their adsorption capacity in just 10 seconds, compared to at least 30 minutes for other materials.
It is 200 percent more efficient than other water filters, he noted.
A competing rival only adsorbed 53 percent of its capacity in the first 10 seconds, making the β-cyclodextrin the fastest BPA remover ever discovered.
“We knew that water filtering would be a likely application if we were successful,” Dichtel noted. “We were definitely pleasantly surprised with just how good the performance is.”
“The difference between our material and activated carbons is that the cyclodextrins are actually much better for binding pollutants,” he added.
Moreover, the material can be regenerated by simply washing the filter in methanol at room temperature compared to activated charcoal, which must be heated to anywhere from 500 degrees Fahrenheit to 900 degrees to get rid of the contaminants.
The manufacturing cost of the β-cyclodextrin polymers may go down to as low as $5 per kilo to a high of $25, Dichtel said.
Once manufactured commercially, the technology can be a boon to Philippine aquaculture as much as water purification for the benefit of the entire population.
