Due to growing concerns about the environmental effects of detergents, research has shifted toward eco-friendly cleaning methods, including the use of purified water. This study aims to increase our understanding of how the properties of purified water can be used to achieve effective washing with minimal surfactant use. We investigated the removal of common soils, such as olive oil, from hydrophilic and hydrophobic surfaces and examined interactions among olive oil, water, and fabric. To further examine the broader impact of purified water, bacterial viability after treatment with different purified grades was investigated.

For hydrophilic surfaces, thin vaseline and thick oil films were washed at varying temperatures and washing cycles. Quartz Crystal Microbalance with Dissipation Monitoring data showed that most thin films were removed within two cycles, while higher temperatures improved efficiency. For thicker films, we were able to divide the washing process into two regimes (exponential and linear), where each one is governed by different washing mechanisms and stability principles. For hydrophobic surfaces, two approaches were tested. First, the pH of purified water was increased with traces of NaOH, and second, small amounts of lipase were added. Both methods significantly enhance cleaning efficiency. The pH-adjusted pure water promotes deprotonation of fatty acids in olive oil and facilitates oil removal from surfaces through roll-up and interfacial tension reduction mechanisms. The added lipase can hydrolyse olive oil into more water-soluble products, which can act as natural surfactants. For interactions between cotton, olive oil, and water, spatially resolved SAXS data revealed that water and oil interact with cotton at different length scales, and that washing partially redistributes and removes oil. Finally, we showed that isothermal calorimetry is an excellent method for assessing bacterial viability and that multiple washing cycles and prolonged incubation can reduce bacterial survival.

På grund av ökande oro för tvättmedels miljöpåverkan har forskningen skiftat mot mer miljövänliga rengöringsmetoder, inklusive användningen av renat vatten. Syftet med denna studie är att öka förståelsen för hur renat vattens egenskaper kan utnyttjas för effektiv tvättning med minimal användning av tensider. Vi undersökte borttagning av vanliga föroreningar såsom olivolja från hydrofila och hydrofoba ytor samt analyserade interaktionerna mellan olivolja, vatten och textilier. För att ytterligare studera renat vattens bredare påverkan utvärderades även bakteriers livskraft efter inkubation i olika renhetsgrader.

För hydrofila ytor tvättades tunna vaselin- och oljefilmer vid varierande temperaturer och tvättcykler. Vi visade att de flesta tunna filmer avlägsnades inom två cykler, medan högre temperaturer förbättrade effektiviteten. För tjockare filmer kunde tvättprocessen delas in i två kategorier (exponentiell och linjär), där varje kategori styrs av olika tvättmekanismer och stabilitetsprinciper. För hydrofoba ytor testades två metoder: först att öka pH i renat vatten med spårmängder av NaOH och sedan att tillsätta små mängder lipas. Båda metoderna förbättrade rengöringseffektiviteten avsevärt. Det pH-justerade rena vattnet främjar deprotonering av fettsyror i olivolja och underlättar borttagning via "roll-up"-mekanismer och minskad gränsytspänning. Det tillsatta lipaset kan hydrolysera olivoljan till mer vattenlösliga produkter som fungerar som naturliga tensider. När det gäller interaktionen mellan bomull, olivolja och vatten visade data att vatten och olja interagerar med bomull på olika längdskalor, och att tvättning delvis omfördelar och avlägsnar olja. Slutligen kunde vi visa att isoterm kalorimetri är en utmärkt metod för att studera bakteriers livskraft, och resultaten visade att flera tvättcykler och långvarig inkubation kan minska bakteriers överlevnad.

Due to growing concerns about the environmental impact of detergents, there has been a notable shift towards researching eco-friendly washing methods, such as using purified water for washing and cleaning. It has been shown that purified water can remove olive oil from hydrophilic surfaces but removing it from hydrophobic surfaces is still a challenge. In this work we studied the removal of olive oil from hydrophobic and hydrophilic surfaces using different water alkalinity, different salt solutions, multiple washing cycles and temperatures. For the hydrophobic surface, gravimetric analysis data demonstrated that non-purified water grades can outperform purified ones, but this effect is due to slight variations of pH. Increasing the pH of purified water by addition of tiny amounts of NaOH (that would not have any environmental impact) significantly enhances cleaning efficiency. For the hydrophilic surfaces, water with increased alkalinity completely removes the oil from the surface in most cases. The study reveals that adjusted pH of otherwise pure water promotes deprotonation of fatty acids in olive oil and facilitates oil removal from surfaces through roll up and interfacial tension reduction mechanisms. Increased temperatures further improve cleaning efficiency. These findings highlight the potential of pH-adjusted purified water as an effective and eco-friendly alternative to conventional cleaning methods. Future research should explore similar techniques on complex materials such as textiles.

The cotton fabric consists of cellulose arranged in a complex structure with multiple levels of organization at different length scales. Understanding this structure and its interactions with water and oil is essential for developing efficient and environmentally friendly methods of cotton washing. In this study, the structure of raw cotton fabric cellulose and the effects of water and oil were examined across a broad range of length scales using spatially resolved synchrotron small-angle X-ray scattering (SAXS) and auxiliary techniques.

Water was observed to penetrate the cotton fabric and interact across nearly all length scales. Although a certain amount of the material was not affected by water as seen by intact distance between microfibrils, fractal analysis of the scattering data indicated a loosening of the microfibril arrangement after contact with water. This process was hindered if the material had been pre-treated with oil and was not seen after subsequent washing with water or surfactant solution. Analyzing spatially resolved SAXS data using a bi-sinusoidal model and 2D maps of the oil-to-cotton ratio facilitates understanding the structure of the material and its interactions with oil on the molecular, nano and macrolevels.

To decrease the negative impact of surfactants, the idea of using purified water in washing has been proposed. Previous studies showed that purified water facilitates the roll-up mechanism by promoting electrostatic interactions between the surface and the soil. However, washing mech-anisms can be dependent on the amount of remaining soil.In this work we studied the removal of thin Vaseline films and thicker oil films from hydro-philic surfaces using multiple washing cycles at different temperatures. The Quartz Crystal Mi-crobalance with Dissipation monitoring (QCM-D) and gravimetric analysis were used for thin and thick films respectively. In QCM-D experiments most of the thin film was removed during the first two cycles, while following cycles did not substantially affect washing efficiency; increased temperature facilitated the washing process. Gravimetric analysis showed that the washing of thicker films can be divided into two regimes. During the first, exponential, regime the amount of oil on the surface is high and surface mechanisms, such as roll-up, dominate. Oil droplets are kinetically stabilized in purified water by electrostatic interactions. As the amount of oil on the surface decreases, the second, linear, regime is introduced. The removal of oil occurs by equi-librium bulk mechanisms, where electrostatic interactions are less important.

Hypothesis: Detergents used in everyday life for cleaning and washing are a source of water pollution and can have a negative effect on human health and the environment. To reduce their negative impact, a new trend of using only purified water for washing and cleaning applications is emerging. A scientific basis of this method needs to be established, as its mechanisms and the efficiency should be better understood. Experiments: In this work, we investigate the effect of water purity on the removal of hydrophobic films from solid surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D) and gravimetric experiments. We compared the cleaning efficiency of TAP water, two grades of purified water, NaCl solution and SDS solution. Findings: The QCM-D results show that both grades of purified water remove more than 90% of Vaseline deposited of the surface while tap water only 75%. SDS solution fully removes the deposited layer. Gravimetric experiments with removal of olive oil from hydrophilic and hydrophobic surfaces also indicate higher efficiency of purified water grades. Contact angle experiments show that pure water facilitates roll-up mechanism of cleaning. We suggest that due to lower ionic strength, purified water increases electrostatic repulsion and promotes the cleaning process.