Effect of Recycling Number on the Fluorescence Reduction of Fluorescent Whitening Agents in White Wastepapers
Fig. 10. H-FWA distribution in the cross section of the paper surface-sized with 10% H-FWA be- fore (left), and after (right) three rounds of recycling.
The distribution changes in T-FWA and H-FWA can be explained by re-adsorption. When T-FWA and H-FWA were extracted from the paper that had been surface-sized with them, the FWAs stayed soluble in the stock. As the contact time between FWAs and the cellulosic fibers increased, some of the detached FWAs re-adsorbed on the cellulosic fibers because of the sulfonic acids pres- ent on a FWA molecule.
chemical bonds formed between T-FWA or H-FWA, and the cellulosic fibers. Therefore, the D-FWA was possibly not extracted from paper be- cause it was attached to the cellulose fibers more strongly than T-FWA and H-FWA. Finally, we concluded that surface-treating FWAs can be detached easily compared with inter- nal FWA and some of the detached FWAs re-ad- sorbed on the cellulosic fibers during the recycling process.
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D-FWA exhibited a much lower fluorescence re- duction than T-FWA and H-FWA. The CIE white- ness and ISO brightness of the paper containing D-FWA decreased by less than those of the papers containing T-FWA and H-FWA reagents when the number of recycling processes increased. The D-FWA was distributed evenly in the cross section of the paper before recycling, and the ini- tial distribution of D-FWA was maintained until four rounds of recycling. However, T-FWA and H-FWA were significantly detached from the pa- pers but showed a similar distribution as that of D-FWA when the recycling process was carried out because of re-adsorption. The D-FWA adsorbed on the cellulosic fibers via hydrogen bonding. However, T-FWA and H-FWA were delivered to the surface of the paper by starch or other carrier chemicals, and there were no
This work was supported by a grant from the National Research Foundation of Korea (NRF) funded by the Korean government (MSIP; No. NRF-2015R1A2 A2A01006463).
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1. Ahn, J. H. and Seo, Y. B., Recycling of waste- paper as countermeasure of climate change, Journal of Korea TAPPI 49(4):104-122 (2017). 2. Lee, J. Y., Kim, E. H., and Sung, Y. J., Im- provement in the retention and strength of paper made from white-grade wastepaper, BioResources 11(2):4718-4726 (2016). 3. Kiviranta, A., Paperboard grades, In Paper and Board Grades, TAPPI Press, Papermaking
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펄프·종이기술 51(2) 2019
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