Paper Recycling Method Could Benefit Forests
3 Aug 2000
An ink-removal technique developed by University of Florida researchers opens the door for paper plants to save trees and enhance profits by recycling more types of paper more cheaply than possible with current methods.
The technique removes inks, pigments and dyes from many types of paper - newsprint, glossy magazines, even tissue --while increasing the amount of recycled paper that plants can use to produce new paper. Current methods typically result in a finished product that is inferior to the original -- newspaper stock, for example, often gets recycled into cardboard -- while the UF technique produces paper nearly the same quality as the virgin stock.
'From an ecological perspective, there is considerable need both to conserve forests and preserve landfill space, but recycling paper is usually more expensive than producing new paper from wood,' said Hassan El-Shall, associate director for research at UF's Engineering Research Center for Particle Science and Technology. 'By making the process more economical and effective, our method may provide a solution.'
The first step in the conventional paper recycling process is to mix the original paper with water to produce paper pulp, said El-Shall and co-inventor Brij Moudgil, professor of materials science and engineering and director of the engineering research centre.
Recycling plants next increase the alkalinity of the mixture and add a class of chemicals known as surfactants, which absorb the ink particles. They transfer the pulp into a flotation machine, where an impeller stirs the mixture and draws in air to create bubbles.
Sometimes augmented with compressed air, the surfactant-coated ink particles attach to the bubbles and rise to the top of the tank. In many cases, the plant operator adds other surfactants to turn the bubbles into foam. The final step in the process is for the foam-carrying ink to be skimmed off and the resulting white pulp transformed into paper.
The technique developed by El-Shall and Moudgil replaces the surfactants, which are costly, with a blend of cheaper chemicals. The chemicals mix with the paper fibre and create their own air bubbles -- eliminating the need for compressed air -- which release the ink from the paper and carry it to the surface to be skimmed off.
El-Shall and Moudgil said although the technique has not yet been tested in the industrial setting of a pilot recycling plant, the results of laboratory tests are very promising. The blend of chemicals is not only more effective with a broader variety of paper stocks than the surfactants, it also nearly doubles the amount of recycled paper that can be used to produce new product for the same cost, El-Shall said.
Moudgil said with current methods, paper plants have little economic incentive to recycle because of the cost of the process. By lowering the cost, the UF technique could enhance the recycling incentive, he said.
The benefits of increased paper recycling would extend beyond corporate profits to protecting the environment and reducing energy use, he added. A ton of paper from recycled pulp saves at least 14 trees, 3 cubic feet of landfill space and 7,000 gallons of water, according to the Environmental Protection Agency and other government sources.
'This technique could provide a win-win solution for both business and the environment,' Moudgil said.
The Engineering Research Center provided about $100,000 for the research. Moudgil and El-Shall have applied for a patent on the process, and several companies have made inquiries about licensing the technology, the researchers said.
On the web at www.napa.ufl.edu
