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Purpose – This paper aims to introduce two methods for immobilisation of TiO2 nanoparticles on a glass plate by means of silicon resin as a medium. Then, to ensure the effectiveness of these stabilisation methods, the photocatalytic degradation and mineralisation of the dye C.I. Reactive Blue 21 (RB21), as a model organic pollutant, were compared using these immobilised systems and the suspended one utilizing UV and sunlight irradiations individually. Design/methodology/approach – TiO2 nanoparticles were supported onto a glass support by silicon resin as an adhesion agent by spraying of TiO2 nanoparticles on the resin surface, which covered the glass plate or brushing the mixture of TiO2 and the resin onto the glass. The characteristics of the applied nano-TiO2 were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer– Emmett–Teller. Photocatalytic degradation and mineralisation of C.I. Reactive Blue 21 (RB21) by two immobilised systems were compared with suspended system in a batch mode under UV and sunlight irradiations after 2 h of treatment. Findings – The results showed that these immobilised modes had efficiencies, including 82-87 per cent degradation of RB21 and 52-58 per cent decrease in chemical oxygen demand (COD) for the operational time of 120 min, comparable to that of the suspended mode (91 per cent degradation of RB21 and, consequently, COD is decreased by 65 per cent). Comparison between photocatalytic efficiencies of two immobilised systems revealed that coating by spraying method performed better than brushing one due to more available surface area of TiO2. Finally, the results obtained from the mentioned supported systems under sunlight indicated the efficiencies about 87 to 89 per cent in comparison of the suspension system regardless of the reaction time enhancement up to 15 h compared to the UV irradiation. Research limitations/implications – In this research, the fixation of TiO2 nanoparticles on a substrate such as normal glass by an easy, inexpensive, durable, repairable and repeatable technique for wastewater treatment was introduced. Due to the simplicity and cheapness of these stabilisation methods and as these stabilisation methods are applicable on other substrates such as concrete, ceramics, etc., you can use these methods in major scales for purification of contaminated water, for example for stabilisation of TiO2 nanoparticles on wall pool utilized for water purification can be used. Originality/value – Two introduced immobilisation methods in this study are novel. The photocatalytic efficiency of these immobilised systems in degradation of water contaminants was investigated by using these systems in degradation and mineralisation of the dye C.I. Reactive Blue 21 (RB21), as a model organic pollutant compared with same TiO2 nanoparticles in an aqueous suspension system under UV light. Furthermore, this paper investigated replacing of inexpensive sources of UV light instead of UV lamps, and then the same photocatalytic reactions were carried out under sunlight as a UV source and degradation efficiencies by two UV sources were compared. [ABSTRACT FROM AUTHOR]

Purpose – This paper aims to study the Improvements in self-cleaning property of the white acrylic water-based paint by addition of different percentages of three commercially available titanium dioxide (TiO2) nanoparticles as additives. Then, due to the risk of destruction of polymeric materials in the presence of nanoparticles, degradation of dry paint film samples was investigated for 15 days using two important chalking and yellowing factors. Finally, the TiO2-modified paint sample with the best performance and optimum percentage of TiO2 nanoparticles that produced desired self-cleaning and dry film properties was introduced. Design/methodology/approach – Self-cleaning and dry film properties of white acrylic water-based paint were investigated by addition of three various types of commercial available TiO2 nanoparticles (SSP-25, STA-100 and KA-100). X-ray diffraction, transmission electron microscopy and Brunauer–Emmett–Teller were used for characterization of TiO2 samples. Colorimetric tests in decolourization of C.I. Basic Red 46 (BR46) were used for determination of self-cleaning properties of TiO2-modified paints in comparison with unmodified paint sample. Also, paints defects such as chalking and yellowing were tested along two weeks. Findings – The results indicated that, in all types of TiO2 nanoparticles, by increasing the amount of TiO2 in modified paint, self-cleaning property of the samples was enhanced. The paint containing SSP-25 indicated better self-cleaning properties than others due to its larger surface area. However, its usage above 3.5 weight per cent caused yellowing and chalking defects in dried paint film. Practical implications – In this research, TiO2-modified paint sample with the best performance in both self-cleaning and mechanical properties was selected among the nine sets of prepared paint samples. All the materials used in this research such as acrylic resin and three types of TiO2 nanoparticles are of industrial grade. Therefore, the introduced TiO2-modified paint sample has the potential for the commercial production as a building exterior paint. Originality/value – In the present study, an attempt at introducing a self-cleaning paint sample with acceptable mechanical properties using three types of commercially available TiO2 nanoparticles as additives and industrial grade of acrylic resin which is the most commonly used water-based resin in building paints, as binder. As far as it was searched in the literatures, the parallel study of the self-cleaning and mechanical properties of paints has not been reported as noteworthy. Self-cleaning property of the acrylic water-based paint samples was investigated by adding three types of the commercially available TiO2 nanoparticles. Also considering the possible detrimental effects of TiO2 nanoparticles on polymeric materials and consequently on physical properties of the paint, chalking and yellowing factors in dried paint samples were evaluated. [ABSTRACT FROM AUTHOR]