Browsing by Author "Lappalainen, Timo"
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- Capturing colloidal nano- and microplastics with plant-based nanocellulose networks
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-04-05) Leppänen, Ilona; Lappalainen, Timo; Lohtander, Tia; Jonkergouw, Christopher; Arola, Suvi; Tammelin, TeklaMicroplastics accumulate in various aquatic organisms causing serious health issues, and have raised concerns about human health by entering our food chain. The recovery techniques for the most challenging colloidal fraction are limited, even for analytical purposes. Here we show how a hygroscopic nanocellulose network acts as an ideal capturing material even for the tiniest nanoplastic particles. We reveal that the entrapment of particles from aqueous environment is primarily a result of the network’s hygroscopic nature - a feature which is further intensified with the high surface area of nanocellulose. We broaden the understanding of the mechanism for particle capture by investigating the influence of pH and ionic strength on the adsorption behaviour. We determine the nanoplastic binding mechanisms using surface sensitive methods, and interpret the results with the random sequential adsorption (RSA) model. These findings hold potential for the explicit quantification of the colloidal nano- and microplastics from different aqueous environments, and eventually, provide solutions to collect them directly on-site where they are produced. - Foam Processing of Fibers As a Sustainable Alternative to Wet-Laying : Fiber Web Properties and Cause-Effect Relations
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2018-09-23) Xiang, Wenchao; Filpponen, Ilari; Saharinen, Erkki; Lappalainen, Timo; Salminen, Kristian; Rojas, Orlando J.Wet-laying is a mature technology that is applied in large scale for the manufacture of nonwovens, including paper products. However, it usually uses large volumes of water and is energy-intensive. Here we used foam-laying to substantially diminish the volume of water consumed in the formation of fiber networks (5-fold reduction) and to reduce the water content of the nonwovens produced before drying, achieving a reduced energy demand. The prospects of foam-laying were evaluated by comparing foam-laid and wet-laid webs of two types of wood fibers: stiff (lignin-containing) or flexible (lignin-free). Also, the effect of foaming agent type (anionic, cationic, nonionic, and amphoteric) was elucidated. Reference webs were produced by conventional wet-laying, with or without surfactants. Foam-laying was effective in producing a more uniform areal mass distribution (better formation) after wet-pressing. This effect was more evident for the webs synthesized with the flexible fibers. Unlike the layered network structures that were obtained by wet-laying, foam-laid webs exhibited a more felted network, with fibers positioned in the out-of-plane direction. As a result, higher air permeability, web porosity, and light scattering coefficients were measured for the foam-laid webs. The enhanced porosity (lower density) was related to the effect of bubbles during foam-laying and the reduction in surface tension of the foamed-fiber dispersion. The resistance to delamination of low-density webs obtained by foam-laying in the out-of-plane direction was preserved. However, the reduction in tensile strength and modulus of foam-laid webs were determined, owing to the reduced density of the formed structures. Notably, the type of foaming agent used played a minor role as far as the resultant properties of the webs, making the process flexible in terms of the selection of environmentally friendly alternatives. Overall, we compared the physico-mechanical properties of fiber networks formed by web- and foam-laying, depending on fiber type and foaming agent, yielding a property space that is useful in the design of lightweight structures (nonwovens, including paper). The prospects of water and energy savings by foam-laying are the major benefits in the sustainable use of fibers for the assembly of porous materials, such as lightweight nonwoven and paper products. - Vuodon paikannus optisella lämpötila-anturilla kaukolämpöjohtorakenteessa
Helsinki University of Technology | Master's thesis(1999) Lappalainen, Timo - Tuloksensäätelyn mittausmenetelmien vertailu suomalaisella tilinpäätösaineistolla vuosina 1992-2001
School of Business | Master's thesis(2003) Lappalainen, Timo