Browsing by Author "Pullar, Robert C."
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- Calcium phosphate-based materials of natural origin showing photocatalytic activityPublication . Piccirillo, Clara; Dunnill, Charles W.; Pullar, Robert C.; Tobaldi, David M.; Labrincha, João A.; Parkin, Ivan P.; Pintado, Manuela M.; Castro, Paula M. L.Calcium phosphate based materials of natural origin with photocatalytic properties were produced. Bones of Atlantic cod fish were treated in appropriate solutions (either Ca- or Ti-containing salts) and successively annealed. Results showed multiphasic materials (hydroxyapatite, beta-tricalcium phosphate and anatase titania) with excellent photocatalytic performance under both UV and visible light, with an anatase concentration of only about 2 mol%. Results with such a low amount of anatase have never been reported before for a calcium phosphate-based material; this is attributed to the presence of anatase being mainly on the surface. Single-phase hydroxyapatite (Ca-10(PO4)(6)(OH)(2) or HAp) also showed some photocatalytic properties and antibacterial activity.
- Exploring the potential of a waste-derived bone char for pharmaceuticals adsorption in saline-based wastewaterPublication . Miranda, Catarina; Scalera, Francesca; Piancastelli, Andreana; Pullar, Robert C.; Tiritan, Maria Elizabeth; Piccirillo, Clara; Castro, Paula M. L.; Amorim, Catarina L.In this study, the effect of salinity in wastewater on the adsorption capacity of a bone char material prepared through pyrolysis of tuna bones at 1000 °C was investigated for two pharmaceuticals, tramadol (TRA) and venlafaxine (VNF), both contaminants of emerging concern. This is the first time that the adsorption efficiency of a bone char-type material was tested in such conditions. The Tuna Bone Char (TBC) was composed of calcium phosphate (hydroxyapatite), and graphitic carbon. The TBC is a nanostructured material (particle size 30–60 nm), with a surface area of 100.67 m2/g (higher than other waste-derived type materials), and a total pore volume of 575.2 mm3/g. TBC capacity to adsorb TRA and VNF, individually or combined, was evaluated in batch experiments using different aqueous matrices: water, non-saline wastewater, and wastewaters with different salinity levels (7.5 and 12 g/L). For individual pharmaceuticals, the TBC had a higher affinity for TRA than VNF. The presence of salts in wastewaters led to a decrease in the TBC adsorption capacity but it was still effective for pharmaceuticals adsorption. Indeed, for the individual pharmaceuticals, the TBC adsorption capacity (qt) was 0.72–2.14 and 0.77–1.70 mg/g for TRA and VNF respectively, depending on the aqueous matrix. With both pharmaceuticals present, lower qt values were experimentally obtained for TRA and VNF. The potential of the TBC, a material derived from a by-product of the fish industry, to be used for environmental remediation in different environments, such as saline wastewaters was demonstrated, widening the range of its potential applications.
- Extraction and characterisation of cellulose nanocrystals from pineapple peelPublication . Madureira, Ana Raquel; Atatoprak, Tugba; Çabuk, Duygu; Sousa, Flávia; Pullar, Robert C.; Pintado, ManuelaThe potential of pineapple peel as a source of cellulose nanocrystals was evaluated. Peels skin from fresh-cut fruit was used as raw material. These residues were puri ed to remove pigments, lipids and hemicellulose, and a bleaching process for deligni cation was carried out for 4-6 h. All resulting products were characterised for their lignin, hemicellulose, cellulose and ash contents using standard techniques. Dry matter at the end was low (ca. 50%) compared with the raw material (ca. 90%). The process applied resulted in ca. 20% (m/m) of puri ed cellulose (ca. 80% purity), with ineligible levels of lignin and hemicellulose present, especially when using 6h of bleaching. The puri ed cellulose was subject to acid hydrolysis for nanocrystal extraction with two testing times, 30 and 60 minutes. These cellulose nanocrystals had small sizes (< 1000 nm), with high variability and negative zeta potential values. The time of extraction did not a ect the nanocrystals' chemical and physical properties. The use of 6 h of bleaching treatment during puri cation was shown to be more e ective than 4 h. Pineapple peel was demonstrated to be a good source of cellulose for the production of cellulose nanocrystals.
- Films of chitosan and natural modified hydroxyapatite as effective UV-protecting, biocompatible and antibacterial wound dressingsPublication . Cunha, Carla S.; Castro, Pedro J.; Sousa, Sérgio C.; Pullar, Robert C.; Tobaldi, David M.; Piccirillo, Clara; Pintado, Maria M.Chitosan is a natural polysaccharide widely used in biomedicine, for instance for wound dressing. Hydroxyapatite is a very bioactive calcium phosphate which, if modified with an appropriate element (iron Fe), can also have UV-absorbing properties. In this work, we report the study of films of chitosan incorporated with iron-modified hydroxyapatite of natural origin (from cod fish bones); this combination led to an innovative chitosan-based material with excellent and advanced functional properties. The films showed very high UV absorption (Ultraviolet Protection Factor (UPF) value higher than 50). This is the first time that a chitosan-based material has shown such high UV protection properties. The films also showed to be non-cytotoxic, and possessed antimicrobial activity towards both Gram-positive and negative strains. Their mechanical properties, optimised with an experimental design approach, confirmed their potential use as multifunctional wound dressing, capable of reducing bacterial infections and, at the same time, protecting from UV light.
- Methyl cellulose films containing natural extracts: antibacterial propertiesPublication . Campos, Débora; Piccirillo, Clara; Pullar, Robert C.; Castro, Paula M. L.; Pintado, Manuela E.
- A sustainable replacement for TiO2 in photocatalyst construction materials: Hydroxyapatite-based photocatalytic additives, made from the valorisation of food wastes of marine originPublication . Saeli, Manfredi; Piccirillo, Clara; Tobaldi, David M.; Binions, Russell; Castro, Paula M. L.; Pullar, Robert C.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 façades. 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 1e5 wt% of our total HAp-based material to the mortar, this means our photocatalytic mortars only contain 0.01e0.05 wt% titania (100e500 ppm), two orders of magnitude less than the quantities of 2e10 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 NOx pollutants under solar light. With intermixing, NOx abatement of 6.3e8.3% 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 façades, and environmentally sustainable materials for the preservation of cultural heritage.