Examinando por Autor "Jurado-Contreras, Sofía"
Mostrando 1 - 3 de 3
- Resultados por página
- Opciones de ordenación
Ítem Characterization of Cellulosic Pulps Isolated from Two Widespread AgriculturalWastes: Cotton and Sunflower Stalks(MDPI, 2024-06-04) la-Rubia, María Dolores; Jurado-Contreras, Sofía; Navas-Martos, Francisco; García-Ruiz, Ángeles; Morillas-Gutiérrez, Francisca; Moya-López, Alberto José; Mateo, Soledad; Rodríguez-Liébana, José AntonioGlobally, huge amounts of cotton and sunflower stalks are generated annually. These wastes are being underutilized since they are mostly burned in the fields. So, in this work, we proposed a three-step method consisting of acid pre-treatment, alkaline hydrolysis, and bleaching for the extraction of cellulose pulps. These pulps were characterized to assess their morpho-structural and thermal properties. The design of experiments and response surface methodology were used for the optimization of the acid pre-treatment in order to achieve maximum removal of non-cellulosic compounds and obtain pulps enriched in cellulose. For cotton stalks, optimal conditions were identified as a reaction time of 190 min, a reaction temperature of 96.2 ◦C, and an acid (nitric acid) concentration of 6.3%. For sunflower stalks, the optimized time, temperature, and acid concentration were 130 min, 73.8 ◦C, and 8.7%, respectively. The pulps obtained after bleaching contained more than 90% cellulose. However, special care must be taken during the process, especially in the acid pre-treatment, as it causes the solubilization of a great amount of material. The characterization revealed that the extraction process led to cellulose pulps with around 69–70% crystallinity and thermal stability in the range of 340–350 ◦C, ready to be used for their conversion into derivatives for industrial applications.Ítem Manufacture and characterisation of PLA biocomposites with high purity cellulose 1 isolated from olive pruning waste(Sage Journal, 2023-03-06) Rodríguez-Liébana, José A.; Navas-Martos, Francisco J.; Jurado-Contreras, Sofía; Morillas-Gutiérrez, Francisca; Mateo, Soledad; Moya, Alberto J.; La Rubia, M.DoloresA two-step chemical process was carried out on olive pruning residues according to an optimised sequence that led to the isolation of natural fibre with a high cellulose content. Reaction time, temperature and HNO3 concentration in the acid hydrolysis stage were optimised by means of the Response Surface Methodology to achieve the highest removal of hemicellulose and lignin and the highest crystallinity index, minimising cellulose hydrolysis. Subsequent hydrolysis with NaOH allowed to obtain a pulp enriched in cellulose (83.28 wt.%). Analysis revealed that the cellulose isolated had a high crystallinity index (70.06%) and thermal stability (Tmax = 357°C). The cellulose obtained was finally used for the manufacture of polymer biocomposites and to evaluate its viability as a filler for polymeric materials. The selected polymer matrix used was polylactic acid (PLA) and the amount of filler was 5 and 15% by weight, respectively. In general, the fibres did not improve the mechanical properties of PLA, and maintained unchanged its melting temperature. Microscopic analysis revealed that PLA/fibre adhesion was stronger for treated fibres. Contradictorily, the composites with untreated fibres presented slightly higher thermal stability. Water uptake increased with the concentration of fibres, being higher in those materials with untreated fibre.Ítem Synthesis and characterization of alkali-activated materials containing biomass fly ash and metakaolin: effect of the soluble salt content of the residue(Springernature, 2022-05-07) Jurado-Contreras, Sofía; Bonet-Martínez, Eduardo; Sánchez-Soto, Pedro José; Gencel, Osman; Eliche-Quesada, DoloresThe present study investigates the production and characterization of alkali-activated bricks prepared with mixing metakaolin (MK) and biomass fly ash from the combustion of a mix of pine pruning, forest residues and energy crops (BFA). To use this low cost and high availability waste, different specimens were prepared by mixing MK with different proportions of BFA (25, 50 and 75 wt%). Specimens containing only metakaolin and biomass fly ash were produced for the purpose of comparison. Effects of the alkali content of biomass fly ash, after a washing pretreatment (WBFA), as well as the concentration of NaOH solution on the physical, mechanical and microstructural properties of the alkali-activated bricks were studied. It was observed that up to 50 wt% addition of the residue increases compressive strength of alkali-activated bricks. Alkalinity and soluble salts in fly ash have a positive effect, leading materials with the improved mechanical properties. Concentration of NaOH 8 M or higher is required to obtain optimum mechanical properties. The compressive strength increases from 23.0 MPa for the control bricks to 44.0 and 37.2 MPa with the addition of 50 wt% BFA and WBFA, respectively, indicating an increase of more than 60%. Therefore, the use of biomass fly ash provides additional alkali (K) sources that could improve the dissolution of MK resulting in high polycondensation. However, to obtain optimum mechanical properties, the amount of BFA cannot be above 50 wt%.