Environmental Science and Pollution Research
Results
pri m arily fro m the addition of coating binders during pro- duction, but m ay also co m e fro m recycled paper contain- ing printing inks, such as styrene-butadiene rubber and polyvinyl acrylate. Odorous co m pounds can arise during both the technological processing of paper and its ageing. The paper m aking process occurs in a m oist and te m perature-sufficient environ m ent rich in nutrients. The increased use of recycled paper contributes to these conditions, pro m oting m icrobial develop m ent. Recy- cled fibres often contain residues fro m sizing agents, coatings, starches, poly m ers, and adhesives, all of which are nutrient- rich (Czerny And Buettner 2009). Anaerobic deco m position of these co m pounds leads to the for m ation of volatile fatty acids, which are m ajor contributors to unpleasant odours. To suppress m icrobial growth and m itigate odour, biocidal agents are introduced, including essential oils that not only provide fragrance but also possess antibacterial properties. Odour-inducing co m pounds m ay be released as a result of m icrobial degradation of lignin and the autooxidation of cardboard. These include odour-active aldehydes such as hexanal, heptanal, octanal, and nonanal (Czerny And Buettner 2009). Paper degradation caused by natural ageing leads to the for m ation of low m olecular weight co m pounds, including, a m ong others, for m ic, acetic, lactic, propionic, and levulinic acids (Jablonsky et al. 2012), which also con- tribute to odour e m issions. Another source of odour precur- sors m ay be unsaturated lipids present in cardboard used for food packaging. Ultraviolet (UV) curable inks containing photoinitiators are co mm only applied in the printing of cel- lulose-based packaging m aterials (Pugh And Guthrie 2000), influencing the rate and extent of lipid oxidation. Fragrances are incorporated to prevent the spread of unpleasant odours associated with paper ageing, food stor- age, or during the m anufacturing of scented paper products. Scent can be added by e m bedding solid or liquid fragrances during the paper m aking process, by introducing fragrance- loaded nano/ m icrospheres directly into the pulp, or through m icroencapsulation, whereby encapsulated co m pounds are adsorbed onto the paper surface (Rungwasantisuk And Rai- bhu 2020). Co mm on encapsulated fragrance agents include lavender essential oil, vanillin, citronella oil, and orange oil. These are delivered using carriers such as chitosan, carboxy m ethylcellulose, or the triblock copoly m er poly- ethylene oxide–polypropylene glycol–polyethylene oxide (PEO–PPO–PEO). Recently, encapsulated fragrances with antibacterial properties have also been introduced into paper products (Perinelli et al. 2020).
Paper composition
A wide variety of che m icals are used in paper production, selected to opti m ize paper properties and m axi m ize pro- duction efficiency while co m plying with environ m ental regulations. The specific grade of paper being produced also influences che m ical selection. One strategy for pro- m oting environ m ental sustainability in the paper industry involves creating a novel co m posite m aterial by co m bining paper with polyester, including the potential use of waste products (Sheeju Selva Roji et al. 2024). The incorporation of short-cut polyester fibres (polyethylene terephthalate) enhances the wet strength of the paper, enabling its use in high-hu m idity environ m ents without disintegration. This polyester addition facilitates the production of fibre- reinforced paper, co mm only used in cardboard boxes and paper bags. In order to i m prove adhesion between cellu- lose and synthetic fibres, a vinyl-acrylic binder is applied. Further m ore, when paper is used as a packaging m aterial, its hydrophobic properties are of particular i m portance. These can be achieved through surface treat m ent with silane- m odified starch (Manoharan et al. 2021; Majka et al. 2023). The properties of paper are also influenced by the presence of residual extractives and adhesive substances known as “stickies.” In addition to the pri m ary co m po- nents—he m icellulose, cellulose, and lignin—wood con- tains a range of extractives. The proportion of these m ajor co m ponents varies depending on the paper type. For office paper, cellulose ranges fro m 61.8% to 79.2%, he m icellu- lose fro m 3.5% to 12.6%, and lignin fro m 2.0% to 9.2% (De Oliveira et al. 2023). In cardboard, the cellulose content is lower (56.9%), while lignin is higher, up to 17.8%, and he m icellulose accounts for approxi m ately 10.7% (Vukoje and Rožić 2018). Extractives typically represent 2–5% of softwood co m position and include waxes, fats, terpenes and terpenoids, fatty acids (e.g. pal m itic and stearic acids), m onosaccharides, alkaloids, and phenolic co m pounds such as si m ple phenols, lignans, flavonoids, tannins, and stil- benes (N’Guessan et al. 2023). The presence of extrac- tives is known to di m inish pulp quality. These co m pounds are soluble in various neutral solvents. Depending on the pulping technology used, up to 85% of extractives m ay be re m oved during processing (Lehr et al. 2021). Organic sticky conta m inants affect both the paper m ak- ing process and the quality of the final paper product. These conta m inants—including polyvinyl acetate poly- m ers, styrene-butadiene rubber, polya m ines, and paraffin waxes derived fro m wood extractives—vary depending on the paper grade (Wang et al. 2023). They originate
Fillers
The m ost co mm on fillers in paper production are m inerals, either of natural origin or produced synthetically. Calcite is
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