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Plastic flexible films are increasingly used in many applications due to their lightness and versatility. In 2014, the amount of plastic films represented 34% of total plastic packaging produced in UK. The flexible film waste generation rises according to the increase in number of applications. Currently, in developed countries, about 50% of plastics in domestic waste are films. Moreover, about 615,000 tonnes of agricultural flexible waste are generated in the EU every year. A review of plastic films recycling has been conducted in order to detect the shortcomings and establish guidelines for future research. This paper reviews plastic films waste management technologies from two different sources: post-industrial and post-consumer. Clean and homogeneous post-industrial waste is recycled through closed-loop or open-loop mechanical processes. The main differences between these methods are the quality and the application of the recycled materials. Further research should be focused on closing the loops to obtain the highest environmental benefits of recycling. This could be accomplished through minimizing the material degradation during mechanical processes. Regarding post-consumer waste, flexible films from agricultural and packaging sectors have been assessed. The agricultural films and commercial and industrial flexible packaging are recycled through open-loop mechanical recycling due to existing selective waste collection routes. Nevertheless, the contamination from the use phase adversely affects the quality of recycled plastics. Therefore, upgrading of current washing lines is required. On the other hand, household flexible packaging shows the lowest recycling rates mainly because of inefficient sorting technologies. Delamination and compatibilization methods should be further developed to ensure the recycling of multilayer films. Finally, Life Cycle Assessment (LCA) studies on waste management have been reviewed. A lack of thorough LCA on plastic films waste ma

Plastic flexible films are increasingly used in many applications due to their lightness and versatility. In 2014, the amount of plastic films represented 34% of total plastic packaging produced in UK. The flexible film waste generation rises according to the increase in number of applications. Currently, in developed countries, about 50% of plastics in domestic waste are films. Moreover, about 615,000 tonnes of agricultural flexible waste are generated in the EU every year. A review of plastic films recycling has been conducted in order to detect the shortcomings and establish guidelines for future research. This paper reviews plastic films waste management technologies from two different sources: post-industrial and post-consumer. Clean and homogeneous post-industrial waste is recycled through closed-loop or open-loop mechanical processes. The main differences between these methods are the quality and the application of the recycled materials. Further research should be focused on closing the loops to obtain the highest environmental benefits of recycling. This could be accomplished through minimizing the material degradation during mechanical processes. Regarding post-consumer waste, flexible films from agricultural and packaging sectors have been assessed. The agricultural films and commercial and industrial flexible packaging are recycled through open-loop mechanical recycling due to existing selective waste collection routes. Nevertheless, the contamination from the use phase adversely affects the quality of recycled plastics. Therefore, upgrading of current washing lines is required. On the other hand, household flexible packaging shows the lowest recycling rates mainly because of inefficient sorting technologies. Delamination and compatibilization methods should be further developed to ensure the recycling of multilayer films. Finally, Life Cycle Assessment (LCA) studies on waste management have been reviewed. A lack of thorough LCA on plastic films waste ma

The aim of the deinking process is to produce deinked pulp from recovered papers (RCPs) with sufficient brightness and cleanliness to fulfil the quality requirements set by the paper grade to be produced. Due to the excessive production costs and material losses of modern deinking processes, there is a need to simplify deinking lines. A prerequisite for this action is that ink content bound to fibres, dirt content and ink fragmentation are minimised in the pulping stage. Thus, it is important to recognise the factors affecting ink behaviour in pulping, to search for new ways to improve ink detachment from RCPs in pulping and to search pulping methods that could efficiently process RCPs printed with various inks. The aim of this thesis was to obtain new information on how the environmental conditions that prevail during the storage and transportation of RCPs affect ink behaviour in subsequent pulping and to find out whether there is further potential to decrease ink content bound to fibres, not only by treating recovered papers chemically before the actual pulping process, but also by removing the detached ink particles during the pulping process. The results show that if some RCPs are very moist and exposed to high temperatures for a reasonable time before the pulping process, the problems in releasing ink from the fibres in pulping become more pronounced and the pulp is dirtier compared to pulp from RCPs that are thermally aged but dry. Properly wetting some RCPs with conventional alkaline deinking chemicals in suitable conditions ahead of the pulping process reduces the ink content that remains bound to the fibres after the pulping process. The efficiency of the pre-wetting treatment in aiding ink detachment from fibres in subsequent pulping is highly dependent on the alkalinity, temperature and duration of the treatment. Semi-continuous ink removal during the pulping process offers the possibility to continue defibering, ink detachment from fibres and di, Tiivistelmä Siistausprosessin tavoitteena on tuottaa keräyspapereista valmistettua vaaleaa ja puhdasta massaa, jota voidaan käyttää uusien paperituotteiden valmistamiseen. Siistausprosesseja pyritään yksinkertaistamaan nykyisten monimutkaisten prosessien korkeiden tuotantokustannusten ja materiaalitappioiden vuoksi. Eräs edellytys siistausprosessien yksinkertaistamiselle on, että kuiduissa kiinni olevan musteen pitoisuus, massan likapitoisuus ja musteen liiallinen pilkkoutuminen minimoidaan siistausprosessin ensimmäisessä vaiheessa, pulpperoinnissa. Täten on tärkeää tunnistaa musteen käyttäytymiseen pulpperoinnissa vaikuttavat tekijät, etsiä uusia mahdollisuuksia parantaa musteen irrotusta keräyspapereista sekä kehittää pulpperointimenetelmiä, joilla voitaisiin prosessoida tehokkaasti eri painomenetelmillä painettuja papereita. Tämän työn tavoitteena oli saada uutta tietoa siitä miten ympäristöolosuhteet, joille keräyspaperit voivat altistua varastoinnin ja kuljetuksen aikana, vaikuttavat musteen käyttäytymiseen pulpperoinnissa. Lisäksi tavoitteena oli selvittää voitaisiinko kuituihin kiinni jääneen musteen pitoisuutta vähentää esiliottamalla keräyspapereita sopivissa kemiallisissa olosuhteissa ennen pulpperointia ja poistamalla irronneet mustepartikkelit massan seasta pulpperoinnin aikana. Tulokset osoittavat, että jos tietyt keräyspaperit ovat erittäin kosteita ja altistuvat korkealle lämpötilalle riittävän pitkän ajan ennen pulpperointia, tulee musteen irrottaminen kuiduista pulpperoinnissa vaikeammaksi ja tuotettu massa likaisemmaksi, kuin sellaisista keräyspapereista, jotka ovat altistuneet kuivina korkealle lämpötilalle. Kuituihin kiinnittyneen musteen pitoisuutta voidaan vähentää esiliottamalla tiettyjä keräyspapereita alkalisilla siistauskemikaaleilla sopivissa olosuhteissa ennen pulpperointia. Esiliotuksen kyky parantaa musteen irrotusta kuiduista pulpperoinnissa riippuu voimakkaasti esiliotusvaiheen alkalisuudesta, lämpötilasta ja kestosta. Kun irronneet m

Paper recycling is an ecological strategy for disposing of waste paper, but more importantly, recovered paper is an important source of raw material in the paper and board industry. Deinked pulp production from recovered paper has proved economically viable by comparison with virgin fibre pulp manufacturing, but this viability is now threatened by increasing waste disposal costs, as up to 25% of the raw material available for deinked pulp production can end up in the reject streams, which then have to be disposed of. The most common practice at present is incineration and disposal of the resulting ash in landfills, but tightening legislation has meant that landfills have become very expensive and are likely to be completely banned in the near future. Thus new ways have to be sought for managing the waste problem in deinked pulp production in order to ensure that the recycled paper production remain both economically and environmentally feasible. The aim of this thesis was to study means of improving the material efficiency of a deinked pulp mill without excessively detracting from end product quality or the performance of the combined sludge dewatering stage. First, an analytical procedure was developed for determining the utilisation potential of reject streams, and a considerable potential for material recovery from these streams was identified. The results presented here show that 80% of the most valuable long fibres from the fine-screening rejects and 15% of the fine material from the flotation froth reject can be recovered. Altogether, with the simultaneous recovery of both categories of reject, it would be possible to improve the material efficiency at the deinked pulp mill by a total of about 5 percentage units, which can be considered significant for process efficiency. Moreover, this would enable the fibre content of the combined sludge to be kept above a certain limit, so that the combined sludge dewatering properties would not be affected. Conseq, Tiivistelmä Paperin kierrätys uusiksi paperituotteiksi on ympäristöystävällinen tapa jätepaperin käsittelemiseksi. Uusiomassan valmistus on myös taloudellisesti kannattavaa verrattuna paperimassan valmistukseen neitseellisistä raaka-aineista. Taloudellinen kannattavuus on kuitenkin vaarassa jätemaksujen alati kasvaessa, sillä siistausmassan valmistuksessa jopa 25 % kierrätyspaperiraaka-aineesta päätyy jätejakeisiin, jotka hävitetään yleisesti polttamalla ja läjittämällä syntynyt tuhka kaatopaikalle. Lainsäädäntö on rajoittanut kaatopaikkasijoittamista ja se on nykyään hyvin kallista. Tulevaisuudessa jätteiden kaatopaikkasijoittaminen voi olla jopa täysin kiellettyä. Jäteongelman ratkaisemiseen tarvitaan siis uusia menetelmiä, jotta kierrätyspaperin valmistus säilyisi sekä taloudellisista että ympäristöllisistä näkökulmista kannattavana toimintana. Tämän väitöskirjatyön tavoitteena oli etsiä keinoja parantaa siistausmassan valmistuksen resurssitehokkuutta palauttamalla käyttökelpoisia materiaaleja jätevirroista takaisin prosessiin siten, ettei heikennetä lopputuotteen laatua eikä lietteidenkäsittelyprosessin toimintaa. Väitöstyön alussa kehitettiin analyysiproseduuri rejektivirtojen hyötykäyttöpotentiaalin arvioimiseksi ja siistamon rejektijakeissa havaittiin merkittävästi hyödynnettävää materiaalia. Tulokset osoittavat, että 80 % hienolajittelun rejekteissä poistuneista arvokkaista pitkistä kuiduista voidaan palauttaa takaisin prosessiin. Lisäksi flotaation vaahtorejektistä voidaan palauttaa 15 % hienoainetta. Palauttamalla yhtäaikaisesti sekä kuituja hienolajittelun rejekteistä että hienoainetta flotaation vaahtorejektistä, voidaan siistausmassan valmistuksen materiaalitehokkuutta parantaa yhteensä noin 5 prosenttiyksikköä, mikä on merkittävä parannus prosessitehokkuuteen. Kuitujen ja hienoaineen samanaikainen palauttaminen pitää lisäksi lietteiden käsittelyssä seoslietteen kuitupitoisuuden tarpeeksi korkeana, jotta sen vedenerotusominaisuudet säilyv

The use of enzymes has been suggested as an environmentally-friendly alternative to complement conventional chemical deinking in the recycling of recovered paper. This study compares the use of carbohydrate hydrolases versus laccase-mediator system for deinking printed fibers from newspapers and magazines. For this purpose, two commercial enzyme preparations with endoglucanase and endoxylanase activities (Viscozyme Wheat from Aspergillus oryzae and Ultraflo L from Humicola insolens) and a commercial laccase NS51002 from Trametes villosa), the latter in the presence of synthetic or natural (lignin related) mediators, were evaluated. The enzymatic treatments were studied at laboratory scale, using a standard chemical deinking sequence consisting of pulping, alkaline deinking and peroxide bleaching stages. Then, handsheets were prepared and their brightness, residual ink concentration, and strength properties were measured. Among the different enzymatic treatments assayed, both carbohydrate hydrolases were found to deink the secondary fibers more efficiently. Brightness increased up to 3-4% ISO on newspaper fibers, being Ultraflo 20% more efficient in the ink removal. Up to 2.5% ISO brightness increase was obtained when magazine fibers were used, being Viscozyme 9% more efficient in the ink removal. As regards laccase-mediator system, alone or combined with carbohydrate hydrolases, it was ineffective deinking both newspaper and magazine fibers, resulting in pulps with worse brightness and residual ink concentration values. However, pulp deinking by laccase-mediator system was displayed when secondary fibers rich in lignin, i.e. printed cardboard, were used, obtaining up to 3% ISO brightness increase and lower residual ink concentrations., Depto. de Ingeniería Química y de Materiales, Fac. de Ciencias Químicas, TRUE, pub

The amount of printing ink in a pulp suspension produced from recovered paper and its impact on overall brightness is commonly estimated from the reflectance-based ink content measured at a wavelength of 700 nm or 950 nm. The method uses a light scattering coefficient that can be measured from a slightly translucent test medium, i.e. of an opacity less than 97%. This is the case with machine-made papers in most instances. Alternatively, suitable opacity can be achieved by preparing a standard low-grammage sheet on a wire screen, but this results in poor retention of fibre fines, mineral fillers and printing inks, which is especially detrimental to ink measurement when the pulp suspension contains substantial amounts of printing inks. Hence opaque pads are often prepared on filter paper to achieve high retention. Unfortunately their high opacity prevents measurement of the light scattering coefficient, and thus a constant coefficient must be used for the determination of ink content. The aim of this thesis was to clarify the effects of retention and fine material changes on the light scattering coefficient in ink content measurement. The results showed that the light scattering properties of pulp in the wavelength region used for ink content analysis do not remain constant when the fine material content varies. The grade of the recovered paper, hyperwashing and flotation alter the fine material content and thus affect the light scattering. Printing ink also affects light scattering, but its practical impact is smaller than that of fibre fines and mineral fillers. The light scattering coefficient used for each ink content measurement needs to be representative, otherwise a systematic bias in ink content measurements may result from changes in the nature of the fine material and in its content. It is recommended that the light scattering coefficient should be measured in order to avoid this. The measurement should preferably be performed from a low-grammage sh, Tiivistelmä Mustepitoisuusmittaus perustuu hajaheijastukseen joko 700 nm tai 950 nm aallonpituudella ja sitä käytetään usein arvioitaessa keräyspaperista valmistetun massasuspension soveltuvuutta painopaperien valmistukseen ja painomusteen vaikutusta massan vaaleuteen. Mustepitoisuuden mittauksessa käytetään valonsirontakerrointa, joka voidaan mitata hieman läpikuultavasta näytteestä eli näytteen opasiteetin on oltava pienempi kuin 97 %. Tämä opasiteettiraja toteutuu useimmiten paperikoneella tehdyille painotuotteille. Riittävän alhainen opasiteetti saavutetaan myös valmistamalla standardin mukainen matalaneliömassainen arkki viiralle, mutta tämä johtaa kuitumaisten hienoaineiden, mineraalisten täyteaineiden ja painomusteiden alhaiseen retentioon. Matala retentio on erityisen haitallinen piirre mustemittauksen kannalta massoilla, jotka sisältävät huomattavia määriä painomusteita. Siten usein valmistetaan läpikuultamattomia arkkeja suodatinpaperin päälle, joiden retentio on korkea. Korkeasta opasiteetista johtuen näistä arkeista ei voida määrittää valonsirontakerrointa, jolloin mustepitoisuuden määritys perustuu vakiokertoimeen. Tämän väitöskirjan tavoitteena oli selvittää retention ja hienoaineiden muutoksien vaikutuksia valonsirontakertoimeen ja mustemittaustulokseen. Tutkimuksen tulokset osoittivat että valonsirontakerroin, joka mitataan mustepitoisuuden yhteydessä, ei pysy vakiona hienoainepitoisuuden muuttuessa. Hienoainepitoisuuteen ja siten valonsirontakertoimeen vaikuttavat keräyspaperin laji, hyperpesu ja vaahdotus. Myös painomuste vaikuttaa valonsirontakertoimeen, mutta käytännössä vaikutuksen suurusluokka on pienempi kuin hieno- ja täyteaineilla. Mustepitoisuuden määrityksessä käytetyn valonsirontakertoimen on oltava edustava, muutoin arvot voivat olla systemaattisesti virheellisiä hienoainemäärän tai laadun muuttuessa. Virheen välttämiseksi olisi suositeltavaa määrittää valonsirontakerroin mustepitoisuusanalyysin yhteydessä. Tämä olisi mahdollista tehdä s

The influence of storage conditions on the ink detachment efficiency of water-based flexographic ink printed onto model cellulose surfaces and handsheets was investigated. It was shown that UV light, elevated temperatures, longer storage time, increasing surface roughness, and increasing surface hydrophobicity all had a negative effect on ink detachment. It was also shown that the ink's chemical and structural characteristics changed when stored at elevated temperatures. No chemical or structural changes could be observed for the ink when stored under UV light., QC 20100525

The atomic force microscope has been used to investigate normal surface forces and lateral friction forces at different concentrations of sodium oleate, a frequently used fatty acid in the deinking process. The measurements have been performed using the colloidal probe technique with bead materials consisting of cellulose and silica. Cellulose was used together with a printing ink alkyd resin and mica, whereas silica was used with a hydrophobized silica wafer. The cellulose-alkyd resin system showed stronger double layer repulsion and the friction was reduced with increasing surfactant concentration. The adhesive interaction disappeared immediately on addition of sodium oleate. The normal Surface forces for cellulose-mica indicated no apparent adsorption of the sodium oleate however, the friction coefficient increased on addition of sodium oleate, which we ascribe to some limited adsorption increasing the effective surface roughness. The silica-hydrophobic silica system showed a completely different surface force behavior at the different concentrations. An attractive hydrophobic interaction was evident since the surfaces jumped into adhesive contact at a longer distance than the van der Waals forces would predict. The strong adhesion was reflected in the friction forces as a nonlinear relationship between load and friction and a large friction response at zero applied load. Indirect evidence of adsorption to the hydrophilic silica surface was also observed in this case, and QCM studies were performed to confirm the adsorption of material to both surfaces., QC 20100915. Uppdaterad från Submitted till Published (20100915)

Katedra dřeva, celulózy a papíru, Dokončená práce s úspěšnou obhajobou

Ink-cellulose interactions were evaluated using a new technique in which the adhesion properties between ink and cellulose were directly measured using a Micro-Adhesion Measurement Apparatus (MAMA). The adhesion properties determined with MAMA were used to estimate the total energy release upon separating ink from cellulose in water. The total energy release was calculated from interfacial energies determined via contact angle measurements and the Lifshitz-van der Waals/acid-base approach. Both methods indicated spontaneous ink release from model cellulose surfaces, although the absolute values differed because of differences in measuring techniques and different ways of evaluation. MAMA measured the dry adhesion between ink and cellulose, whereas the interfacial energies were determined for wet surfaces. The total energy release was linked to ink detachment from model cellulose surfaces, determined using the impinging jet cell. The influences of surface energy and surface roughness were also investigated. Increasing the surface roughness or decreasing the surface energy decreased the ink detachment due to differences in the molecular contact area and differences in the adhesiom properties., QC 20100525

The influence of UV-Iight, temperature, atmospheric environment and storage time on the ink detachment of water-based flexographic ink printed on model cellulose surfaces was investigated using an impinging jet cell equipment. The printed surfaces were deinked using a NaOH solution (pH = 10) and the deinking process was monitored using a microscope equipped with a CCD camera. Images were collected at different time intervals during the detachment process and image analysis was used to quantify the ink detachment from the surface. Hand sheets, (the same pulp as used for model surface preparation) were also printed and stored under the same conditions, after which they were reslushed and deinked. The deinking efficiency of the recycled sheets was evaluated using brightness and ERIC (Effective Residual Ink Concentration) values. It was shown that UV-Iight had a negative effect on ink detachment both from the model cellulose surfaces and from the hand sheets. At storage temperatures of 55degreesC, (dark conditions were used) a large negative effect was observed for the cellulose surfaces while only a small effect on the ink detachment could be seen for the hand sheets. Ink detachment from the hand sheets became more difficult when increasing the storage temperature above 55degreesC, as detected as a decrease in brightness of the recycled and deinked sheets. A farther increase in the storage temperature to 105degreesC gave poorer ink detachment efficiency than storage under UV-Iight for the hand sheets. Air had a more negative effect on ink detachment than nitrogen., QC 20100525

The influence of UV-light, temperature, atmospheric environment and storage time on the ink detachment of water-based flexographic ink printed on model cellulose surfaces was investigated using an impinging jet cell equipment. The printed surfaces were deinked using a NaOH solution (pH = 10) and the deinking process was monitored using a microscope equipped with a CCD camera. Images were collected at different time intervals during the detachment process and image analysis was used to quantify the ink detachment from the surface. Hand sheets, (the same pulp as used for model surface preparation) were also printed and stored under the same conditions, after which they were reslushed and deinked. The deinking efficiency of the recycled sheets was evaluated using brightness and ERIC (Effective Residual Ink Concentration) values. It was shown that UV-light had a negative effect on ink detachment both from the model cellulose surfaces and from the hand sheets. At storage temperatures of 55°C, (dark conditions were used) a large negative effect was observed for the cellulose surfaces while only a small effect on the ink detachment could be seen for the hand sheets. Ink detachment from the hand sheets became more difficult when increasing the storage temperature above 55°C, as detected as a decrease in brightness of the recycled and deinked sheets. A further increase in the storage temperature to 105°C gave poorer ink detachment efficiency than storage under UV-light for the hand sheets. Air had a more negative effect on ink detachment than nitrogen.

The influence of UV-light, temperature, atmospheric environment and storage time on the ink detachment of water-based flexographic ink printed on model cellulose surfaces was investigated using an impinging jet cell equipment. The printed surfaces were deinked using a NaOH solution (pH = 10) and the deinking process was monitored using a microscope equipped with a CCD camera. Images were collected at different time intervals during the detachment process and image analysis was used to quantify the ink detachment from the surface. Hand sheets, (the same pulp as used for model surface preparation) were also printed and stored under the same conditions, after which they were reslushed and deinked. The deinking efficiency of the recycled sheets was evaluated using brightness and ERIC (Effective Residual Ink Concentration) values. It was shown that UV-light had a negative effect on ink detachment both from the model cellulose surfaces and from the hand sheets. At storage temperatures of 55°C, (dark conditions were used) a large negative effect was observed for the cellulose surfaces while only a small effect on the ink detachment could be seen for the hand sheets. Ink detachment from the hand sheets became more difficult when increasing the storage temperature above 55°C, as detected as a decrease in brightness of the recycled and deinked sheets. A further increase in the storage temperature to 105°C gave poorer ink detachment efficiency than storage under UV-light for the hand sheets. Air had a more negative effect on ink detachment than nitrogen.

The influence of UV-light, temperature, atmospheric environment and storage time on the ink detachment of water-based flexographic ink printed on model cellulose surfaces was investigated using an impinging jet cell equipment. The printed surfaces were deinked using a NaOH solution (pH = 10) and the deinking process was monitored using a microscope equipped with a CCD camera. Images were collected at different time intervals during the detachment process and image analysis was used to quantify the ink detachment from the surface. Hand sheets, (the same pulp as used for model surface preparation) were also printed and stored under the same conditions, after which they were reslushed and deinked. The deinking efficiency of the recycled sheets was evaluated using brightness and ERIC (Effective Residual Ink Concentration) values. It was shown that UV-light had a negative effect on ink detachment both from the model cellulose surfaces and from the hand sheets. At storage temperatures of 55°C, (dark conditions were used) a large negative effect was observed for the cellulose surfaces while only a small effect on the ink detachment could be seen for the hand sheets. Ink detachment from the hand sheets became more difficult when increasing the storage temperature above 55°C, as detected as a decrease in brightness of the recycled and deinked sheets. A further increase in the storage temperature to 105°C gave poorer ink detachment efficiency than storage under UV-light for the hand sheets. Air had a more negative effect on ink detachment than nitrogen.

The influence of UV-light, temperature, atmospheric environment and storage time on the ink detachment of water-based flexographic ink printed on model cellulose surfaces was investigated using an impinging jet cell equipment. The printed surfaces were deinked using a NaOH solution (pH = 10) and the deinking process was monitored using a microscope equipped with a CCD camera. Images were collected at different time intervals during the detachment process and image analysis was used to quantify the ink detachment from the surface. Hand sheets, (the same pulp as used for model surface preparation) were also printed and stored under the same conditions, after which they were reslushed and deinked. The deinking efficiency of the recycled sheets was evaluated using brightness and ERIC (Effective Residual Ink Concentration) values. It was shown that UV-light had a negative effect on ink detachment both from the model cellulose surfaces and from the hand sheets. At storage temperatures of 55°C, (dark conditions were used) a large negative effect was observed for the cellulose surfaces while only a small effect on the ink detachment could be seen for the hand sheets. Ink detachment from the hand sheets became more difficult when increasing the storage temperature above 55°C, as detected as a decrease in brightness of the recycled and deinked sheets. A further increase in the storage temperature to 105°C gave poorer ink detachment efficiency than storage under UV-light for the hand sheets. Air had a more negative effect on ink detachment than nitrogen.

The influence of UV-light, temperature, atmospheric environment and storage time on the ink detachment of water-based flexographic ink printed on model cellulose surfaces was investigated using an impinging jet cell equipment. The printed surfaces were deinked using a NaOH solution (pH = 10) and the deinking process was monitored using a microscope equipped with a CCD camera. Images were collected at different time intervals during the detachment process and image analysis was used to quantify the ink detachment from the surface. Hand sheets, (the same pulp as used for model surface preparation) were also printed and stored under the same conditions, after which they were reslushed and deinked. The deinking efficiency of the recycled sheets was evaluated using brightness and ERIC (Effective Residual Ink Concentration) values. It was shown that UV-light had a negative effect on ink detachment both from the model cellulose surfaces and from the hand sheets. At storage temperatures of 55°C, (dark conditions were used) a large negative effect was observed for the cellulose surfaces while only a small effect on the ink detachment could be seen for the hand sheets. Ink detachment from the hand sheets became more difficult when increasing the storage temperature above 55°C, as detected as a decrease in brightness of the recycled and deinked sheets. A further increase in the storage temperature to 105°C gave poorer ink detachment efficiency than storage under UV-light for the hand sheets. Air had a more negative effect on ink detachment than nitrogen.