Self-cleaning Photocatalytic Paints: Efficiency Under Indoor Lighting Systems

The awareness of a healthy living environment is increasing in recent years and it concerns either outdoor or indoor spaces. Recently, buildings and indoor living spaces have often been objects of dedicated studies aiming to optimise the energy demand in relation to heating and ventilating systems, as well as Indoor Air Quality (IAQ) management [1]. Designers and architects tend to limit the air mass exchanges with outdoor environment in order to minimise the energy demand for air conditioning, thus preferring the recycling of indoor air. This involves the gradual increase in indoor pollutants and the decay in IAQ. The pollutants content in indoor spaces often reaches a concentration higher than outdoor, thus requiring the introduction of adequate control and remediation systems in order to maintain a suitable air quality. Several remediation systems are available and indoor pollutant removal takes currently advantage of various technologies. Air filtration through filtering and/or adsorbing cartridges is often used, but they involve continuous maintenance operations (i.e. increased costs). An alternative and low-cost VOCs remediation system is based on the Advanced Oxidation Processes (AOPs). Thanks to the employment of suitable photocatalytic self-cleaning wall paints, VOC can be removed from air while organic dirty stains are removed from the surface. Both pollutant typology are completely mineralised towards carbon dioxide and water. Dedicated scientific papers have taken into account the performance of the photocatalysts themselves, but rarely the photocatalytic paint formulations have been characterised nor their performances accurately assessed in real or simulated indoor conditions [2, 3]. The paint components, indeed, can significantly affect and modify the performance of the active photocatalytic compounds. The self-cleaning photocatalytic paints can be designed for specific applications such as outdoor or indoor environments. In the latter case, the paint formulation should consider different light sources with respect to the outdoor one (i.e. the sun), with very different energy content for the activation of the photocatalytic compounds. The aim of the present contribution is to assess the performances in different conditions of three commercial indoor self-cleaning photocatalytic paints (SCP-1, SCP-2, SCP-3) with respect to their composition and experimental parameters.