Matheus de Carvalho Dias

The growing demand for more sustainable construction materials has driven the development of composites incorporating industrial and agricultural residues, contributing to the reduction in virgin raw material consumption and the valorisation of by-products. In this context, the present study investigated the influence of incorporating rice husk subjected to different chemical treatments and the partial replacement of commercial gypsum with recycled gypsum on the flexural strength, compressive strength and microstructural characteristics of gypsum-based composites. Initially, formulations containing 5 wt.% and 10 wt.% rice husk in three different conditions, untreated, treated with calcium hydroxide, and treated with acetic acid, were produced and evaluated in terms of compressive strength and flexural strength. The formulation containing 5 wt.% rice husk treated with acetic acid exhibited the best overall performance and was therefore selected for the subsequent stage of the study. In the second phase, mixtures incorporating 20 wt.%, 30 wt.% and 40 wt.% recycled gypsum, with and without the addition of 5 wt.% treated rice husk, were investigated. Furthermore, particle size distribution, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) analyses were performed. The results demonstrated that the acetic acid treatment resulted in higher flexural and compressive strength compared with the other treatment conditions evaluated. Partial replacement with recycled gypsum also yielded promising results, with the formulation containing 70 wt.% commercial gypsum and 30 wt.% recycled gypsum exhibiting the highest mechanical strength among the composites without lignocellulosic reinforcement. Microstructural characterisation revealed the preservation of the principal mineralogical phases following the recycling process, and SEM micrographs showed the incorporation of rice husk within the gypsum matrix. Overall, the combination of 30 wt.% recycled gypsum and 5 wt.% rice husk treated with acetic acid represents a technically viable alternative for the development of gypsum composites intended for non-structural applications in the construction industry, while promoting the beneficial utilisation of waste materials.

The contamination of water resources by heavy metals poses a serious environmental risk, and conventional treatment methods face significant limitations. This review addresses the issue by presenting a critical analysis of the development of sustainable biosorbent and biopolymeric materials for heavy metal adsorption, highlighting advances, challenges, and future perspectives. To this end, a systematic bibliometric analysis of 120 documents was conducted, extracted from the Scopus and Web of Science databases, covering the period from 2003 to 2025. The results indicate exponential growth in scientific interest in biopolymers such as cellulose, chitosan, lignin, and alginate, especially in the form of aerogels, which demonstrate high adsorptive capacity through mechanisms such as complexation, chelation, and ion exchange. The analysis also reveals the main factors influencing process efficiency, such as pH, temperature, and contact time. It is concluded that, although these sustainable materials are highly promising, challenges related to scalability, selectivity in complex effluents, and regenerability still need to be overcome to enable their large-scale industrial application, in line with the principles of the circular economy.

A pesquisa explora a incorporação de resíduos (pó de pedra e casca de arroz) em compósitos de argamassas, com objetivo de desenvolver placas para revestimento interno para habitações de interesse social. A casca de arroz recebeu tratamento prévio para melhorar a compatibilidade química na matriz cimentícia. Foi analisada a resistência mecânica, com substituição parcial de agregado miúdo pelo pó de pedra nos teores de 50 e 75%, além da adição cominada de 1% e 2% de casca de arroz. Os resultados indicam que a substituição do agregado miúdo pelo pó de pedra com adição de 1% de casca de arroz, apresentaram bom comportamento mecânico com classificação, de acordo com a ABNT NBR 13281-1, igual a R3 e, para a adição de 2% classificação R2. A partir dos resultados, é possível identificar o potencial de aproveitamento destes resíduos, justificando sua funcionalidade frente a grande extração de agregados naturais.