Nanomaterials : Adding nanofibers to paper more than doubles the number of times it can be recycled
Splitting Hairs- Micrometers-wide cellulose fibers derived from wood pulp are used to make paper. Nanofibers made by splitting apart such fibers can make stronger paper when added to the mix.
Adding cellulose nanofibers to paper pulp creates paper that can be recycled more than twice as many times as regular paper (Environ. Sci. Technol. 2015, DOI: 10.1021/acs.est.5b02676). Depending on how the nanofibers are produced, this should reduce paper’s environmental impact, researchers say.
Paper is a jumbled mat of micrometers-wide cellulose fibers. In the past few years, researchers have been interested in making paper with nanometers-wide cellulose fibers in addition to regular fibers. The high surface area of such nanofibers lets them form more bonds with adjacent fibers, resulting in tougher paper.
Marc Delgado-Aguilar of the University of Girona and his colleagues wanted to analyze the environmental impact of adding nanofibers to paper. They recycled standard paper several times by using either conventional mechanical recycling techniques or by adding 3 % by weight of cellulose nanofibers to the paper pulp at each cycle. They tested the paper’s mechanical strength after every cycle.
Conventional recycling made the sheets unusable for writing after three cycles, whereas the nanofiber-treated paper could be recycled seven times.
The drawback of cellulose nanofibers is that they are made today by treating wood pulp with strong acids and oxidants, followed by mechanical division of cellulose fibers into their nanoscale subunits. To eliminate the need for chemical processing, the researchers used a purely mechanical method to separate the nanofibers, which costs 1/100 th that of the conventional process.
They also performed a preliminary life-cycle assessment of the environmental impact of the two techniques, taking into account factors such as water and energy use, effects on human health, and waste generation. The two recycling techniques had a similar environmental impact, even including the greater number of recycling cycles for nanofiber paper. However, says Delgado-Aguilar, improvements in nanofiber production technology should lower its energy use and yield even better nanofibers that could increase the number of possible recycling cycles even further. This should eventually give paper with less environmental impact than today’s recycled paper. »
Article by Prachi Patel
Chemical & Engineering News- Department Science & Technology
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