No abstract

Este trabalho avaliou a utilização da casca de abacaxi (Ananas comosus) como adsorvente para remoção do corante catiônico azul de metileno presente em solução aquosa. O adsorvente foi obtido através da secagem e trituração das cascas da fruta. A granulometria do material foi < 0.2 mm. Os ensaios de adsorção foram realizados em batelada, sob rotação de 150 rpm e à temperatura de 30 e 40°C. O efeito da quantidade de adsorvente (0,1g-0,5g) e concentração inicial de adsorbato (60ppm-100ppm) no percentual de remoção (%R) e na capacidade de adsorção unitária (qe) foram avaliados. Os modelos de isoterma de Langmuir e Freundlich foram utilizados na descrição matemática do sistema. A casca de abacaxi apresentou remoção de até 81 % do corante azul de metileno. O aumento da massa de adsorvente proporcionou um aumento na percentagem de remoção do corante e diminuição da capacidade de adsorção unitária (qe). O aumento da concentração inicial do adsorbato em solução aquosa provocou uma redução na percentagem de remoção e um aumento na capacidade de adsorção unitária (qe). O modelo de isoterma de Freundlich foi o que melhor se ajustou aos dados experimentais. O ajuste do modelo de Langmuir aos dados experimentais revelou a capacidade de adsorção unitária máxima para a casca de abacaxi como sendo de 17,12 mgg-1 e 10,06 mgg-1 à 30C e 40°C, respectivamente. O caráter da reação de adsorção foi exotérmico pois a elevação da temperatura desfavoreceu a remoção do corante. Os resultados apontam que esse resíduo agroindustrial tem potencial para ser utilizado como um adsorvente econômico para a remoção de azul de metileno.

Avaliação das propriedades físicas, químicas e mineralógicas da fraçãofina (<150 µm) do agregado reciclado de RCD (Evaluation of the physical, chemical and mineralogical properties of the fine fraction (<150 µm) of the recycled CDW aggregate) ResumoFatores como o alto consumo de recursos naturais e os elevados volumes de resíduos produzidos pela indústria da construção civil alertam sobre a importância de reutilizar e reciclar os materiais. Assim, este trabalho objetivou determinar e avaliar as características físicas, químicas e mineralógicas dos finos do agregado reciclado (FAR), comparando-os com finos dos agregados naturais (FAN). Para tanto, determinaram-se a distribuição granulométrica, área específica, formato e textura superficial, índice de atividade pozolânica, óxidos presentes, teor de argamassa aderida e fases minerais. Os resultados mostraram que os FAR apresentam características que se destacam em relação aos FAN, dentre elas o formato mais irregular e superfície porosa. Entretanto, os FAR possuem melhor distribuição granulométrica, o que pode favorecer a compacidade das misturas. Em termos de desempenho pozolânico, os FAR não podem ser considerados como materiais pozolânicos, embora se faça necessário avaliá-los em finura requerida por norma. Palavras-chave: reciclagem, atividade pozolânica, construção civil, fração fina do agregado reciclado. AbstractFactors such as high consumption of natural resources and high volumes of waste produced by the construction industry warn the importance of reusing and recycling materials. Thus, this work aimed to determine and evaluate the physical, chemical and mineralogical characteristics of the fines of recycled aggregate (FRA), comparing them with fine natural aggregates (FNA). For that, particle size, specific area, shape and surface texture, pozzolanic activity index, oxides present, content of adhered mortar and mineral phases were determined. The results showed that the FRA have characteristics that stand out in relation to the FNA, among them the more irregular shape and porous surface. However, the FRA has a better particle size distribution, which may favor the compactness of the blends. In terms of pozzolanic performance, the FRA can not be considered as pozzolanic material, although it is necessary to evaluate them in the fineness required by standard.

This study investigated the physical-mechanical effects of cement-lime mortars containing recycled aggregate of construction and demolition waste (CDW). The natural aggregate (NA) was replaced by volume at 25%, 50%, 75% and 100% by mixed recycled aggregate (MRA) obtained from the CDW crushing. Five types of mortars were prepared with a volumetric ratio of 1:1:6 (cement, lime and aggregate) and water/binder ratio based on the fixed consistency of 260 mm. The effects of MRA on fresh and hardened mortars’ properties were analyzed. The results were analyzed using a one-way ANOVA. MRA incorporation improved most of the physical-mechanical properties of mortars tested, except for hardened bulk density, water absorption and porosity. In the long-run, mechanical strengths significantly increased in all compositions, especially those with higher percentages of MRA. The results obtained showed that the use of MRA in masonry mortars is an alternative to reduce the generation of waste and consumption of natural resources.

No abstract

Obtained natural sands can present different particle size distributions (PSD), although they have the same mineralogical origin. These differences directly influence the physical and mechanical behavior of mortars and, therefore, the performance of mortar and ceramic renderings. Standardizing the particle size of sands based on pre-established requirements in normative standards (NBR 7214 or ASTM C778) is one way to minimize these effects. However, these standards do not consider the optimization of the granular skeleton through the analysis of bulk density and PSD, which may be insufficient to obtain satisfactory results. Therefore, this paper analyzes the effects of using different particle size ranges on the physical and mechanical behavior of cement and hydrated lime mortars. The properties of consistency index, bulk density, air content, capillary water absorption, water absorption by immersion, flexural strength, compressive strength, and dynamic modulus of elasticity were evaluated. For this purpose, standardized sands of the same mineralogical origin were made with different particle size ranges, being: (i) standardized sand constituted by 25% of coarse and fine fractions (S25-control), (ii) standardized sand constituted by 30% of coarse fraction and 20% of fine fraction (S30-20), and (iii) standardized sand composed by 40% of coarse fraction, and 10% of fine fraction (S40-10), respectively. The results indicated that variations in the particle size composition of the standardized sands are necessary to obtain mixtures with higher compactness and, therefore, mortars with better physical and mechanical performance. Thus, the dosage of the particle size fractions of standardized sand should consider the optimization of the granular skeleton, being the unit mass and the granulometric composition as important parameters to meet this premise.

No abstract

In this work, the natural and modified carnauba powder from the addition of bentonite was evaluated for the adsorption of Cu(II) ions in synthetic solution. The results showed that the carnauba powder treated with bentonite (CPTB) showed a better percentage of removal of Cu(II) ions when compared to natural carnauba powder (NCP). The best results for both adsorbents were obtained with pH 5. The adsorption kinetics was governed by the pseudo-second order model for both bioadsorbents studied. While the isothermal behavior was governed by the Langmuir model and showed that the adsorption capacity of the CPTB for Cu(II) was 21.98 mg·g−1. The interaction of the metal and CPTB was also investigated by means of thermodynamic parameters showing that the adsorption process is not spontaneous, although the values of ΔG° decrease with the increase in temperature from 20 to 40 °C and endothermic causing an increase in the degree of disorder at the solid/liquid interface. The results showed that the CPTB is a material with potential adsorbent for the removal of copper ions.