A sustainable replacement for TiO2 in photocatalyst construction materials: Hydroxyapatite-based photocatalytic additives, made from the valorisation of food wastes of marine origin

authors	Saeli, M; Piccirillo, C; Tobaldi, DM; Binions, R; Castro, PML; Pullar, RC
nationality	International
journal	JOURNAL OF CLEANER PRODUCTION
author keywords	Sustainable material; Photocatalysis; Hydroxyapatite; Waste valorisation; Construction material; NHL mortar
keywords	LIFE-CYCLE ASSESSMENT; PHOSPHATE-BASED MATERIALS; TITANIUM-DIOXIDE; VISIBLE-LIGHT; CEMENTITIOUS MATERIALS; AGRICULTURAL WASTES; BUILDING-MATERIALS; NANO-TITANIA; DEGRADATION; CONCRETE
abstract	The use of waste materials and by-products in building materials is of increasing importance to improve sustainability in construction, as is the incorporation of photocatalytic materials to both combat atmospheric pollution and protect the structures and fa ades. This work reports the innovative use of photocatalytic hydroxyapatite (HAp) based powders, derived from Atlantic codfish bone wastes, as an additive to natural hydraulic lime mortars. HAp is the main component of bone, and hence is non-toxic and biocompatible. This is the first time that such a calcium phosphate-based photocatalyst, or indeed any fish/marine derived wastes, have been added to building materials. A key factor is that this HApbased photocatalyst contains only 1 wt% TiO2, the material usually used as a photocatalyst in construction materials. As we only add 1-5 wt% of our total HAp-based material to the mortar, this means our photocatalytic mortars only contain 0.01-0.05 wt% titania (100-500 ppm), two orders of magnitude less than the quantities of 2-10 wt% TiO2 which are usually needed. Our photocatalyst is made from a sustainable waste stream by simple solution and thermal processing, and thus with a much smaller impact on the environment. Specimens were made by either traditional intermixing techniques, or by a post -curing coating procedure. All showed gas-phase photocatalytic activity for abatement of NO pollutants under solar light. With intermixing, NOx abatement of 6.3-8.3% was observed. However, for coated mortars, superior NOx conversion rates were achieved of 7.1% and 23.8%, with 1 and 5 wt% additions, respectively. These results show the potential of this naturally-derived photocatalyst for applications in the construction industry, leading to lower atmospheric pollution and the creation of more durable/lower maintenance building fa ades, and environmentally sustainable materials for the preservation of cultural heritage. (C) 2018 Elsevier Ltd. All rights reserved.
publisher	ELSEVIER SCI LTD
issn	0959-6526
year published	2018
volume	193
beginning page	115
ending page	127
digital object identifier (doi)	10.1016/j.jclepro.2018.05.030
web of science category	GREEN & SUSTAINABLE SCIENCE & TECHNOLOGY; Engineering, Environmental; Environmental Sciences
subject category	Science & Technology - Other Topics; Engineering; Environmental Sciences & Ecology
unique article identifier	WOS:000437997200009