Environmental Science and Pollution Research
cellulose fibres fro m waste paper include disintegration using sodiu m hydroxide (NaOH), followed by coarse screen- ing of m echanical i m purities and a deinking process involv- ing flotation and washing. Flotation enables the re m oval of fillers and inks, while washing eli m inates residual m icro- particles fro m the suspension. These procedures m ay be m odified through enzy m atic treat m ent (Singh et al. 2020) and ther m o m echanical dispersion. However, when re m ov- ing fillers, especially precipitated calciu m carbonate (PCC), flotation m ay not be sufficiently effective. PCC particles are typically s m aller than 5 μ m , which is below the opti m al sep- aration range of flotation. In addition, PCC is hydrophilic and therefore poorly adheres to air bubbles; this li m itation, however, can be overco m e with the use of collectors (Hubbe And Gill 2016). The choice of che m ical reagent depends on the intended application of the cellulose fibres. Strong acids such as hydrochloric acid (HCl) cause hydrolysis of glycosidic bonds within cellulose, leading to fibre shortening and reduced crystallinity, particularly in a m orphous regions (Habibi et al. 2010). In contrast, low concentrations of ace- tic acid do not affect the crystalline structure of cellulose, nor do they result in acetylation (Hu et al. 2018). Acetic acid was therefore selected for its gentle effect on the fibres and its selective reactivity with PCC. The reaction yields soluble calciu m acetate, which can be easily re m oved by washing. This approach m ini m izes both the risk of cellulose degra- dation and the technological and environ m ental concerns associated with the use of aggressive m ineral acids. In addition to the standard recycling of waste paper, the subject of interest is increasing its value in the for m of new products, such as the production of cellulose nanocrystals (CNs). Many reactive che m ical groups are present on the surface of CNs, allowing physical adsorption, surface m odi- fication, and che m ical vapour deposition. This ensures the use of CNs in a wide range of applications, both in their original state and based on other che m ical m odifications (Rashid et al. 2023). These properties m ake it possible for the m to be applied extensively in the industry, including construction, cuisine, teleco mm unications, the auto m otive industry, m edication, the cos m etic industry, and the produc- tion of carbon nanotubes, representing another rod-shaped nano m aterial with excellent m echanical and electrical con- ductivity perfor m ance (Yang et al. 2022; Moha mm ad Fir- m an et al. 2023). In the environ m ent, CNs are used as the hybrid bio-sponge sorbent with m agnetic bi m etallic Fe 3 O 4 @ TiO 2 for coloured water treat m ent and oil–water separation (Assanvo et al. 2023). Moreover, CNs and CNFs have been widely investigated for wastewater re m ediation due to their high surface area and the possibility of changing the surface che m istry. Functionalized nanocellulose has shown excel- lent sorption capacity for heavy m etals (e.g. Pb 2+ , Cr 6+ , and Cd 2+ ), dyes, pesticides, and oil residues. For m s such
EH
Environ m ental hazards
EuPIA
European Printing Ink Association Globally Har m onized Syste m of Classification and Labelling of Che m icals
GHS
HH
Health hazards
I Irritant KODAFLEX TXIB 2,2,4-Tri m ethyl-1,3-pentanediol diisobutyrate OP Office paper PAC Polyalu m iniu m chloride PCC Precipitated calciu m carbonate PES Polyester PPCs Plant fibre/plastic co m posites STD Standard deviation stickies Organic sticky conta m inants US EPA United States Environ m ental Protec- tion Agency UV Ultraviolet
Introduction
In the Czech Republic, 40–50 kg of waste paper is produced per person/year. According to Milbrandt et al. (2024), the largest share of the waste paper is achieved by cardboard (44%); co m postable paper, food-soiled paper products, towels, and napkins (21%); other papers, books and aseptic containers (18%); newspapers (6%); high-grade office paper (6%); and journals (5%). Increasing paper consu m ption pro- duces m ore waste paper. Thus, the extraction of pulp fro m paper waste can reduce negative i m pacts on forest ecosys- te m s (Hanafiah et al. 2019). Waste paper is a significant raw m aterial whose value can be efficiently increased according to the rules of the circular econo m y. While the largest pro- portion of recycled cellulose fibres is still used for paper pro- duction and products (for exa m ple, pressed fibres), a sharp increase has been seen m ainly in biodegradable food trans- port packaging (Andrade et al. 2022) based on plant fibre/ plastic co m posites (PPCs). The potential safety risk of plant fibres is the crucial distinction between PPCs and co mm on plastic m aterials (Zhang And Weng 2021). Despite the rapid develop m ent of technologies for processing cellulose fibres and cellulose nanocrystals (CNs) in the packaging industry, there are so m e doubts about the safety of these products m ade fro m waste cellulose fibres in connection with releas- ing volatile m igrants fro m packaging or printing (An et al. 2024). However, syste m atic research on m igration m ethods and safety assess m ent is still insufficient, and further studies are needed regarding the m ain safety risks and m igration patterns. For further utilization of cellulose fibres, their quality is a deter m ining factor. Standard technologies for recovering
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