To date, great strides have been made in elucidating the role of thermochemical pretreatments in the chemical and structural features of plant cell walls; however, there is no clear picture of the plant recalcitrance and its relationship to deconstruction. Previous studies precluded full answers due to the challenge of multiscale features of plant cell wall organization. Complementing the previous efforts, we undertook a systematic, multiscale, and integrated approach to track the effect of microwave-assisted H2SO4 and NaOH treatments on the hierarchical structure of plants, i.e., from a nano- to micrometer scale. We focused on the investigation of the highly recalcitrant sclerenchyma cell walls from sugarcane bagasse. Through atomic force microscopy and X-ray diffraction analyses, remarkable details of the assembly of cellulose microfibrils not previously seen were revealed. Following the H2SO4 treatment, we observed that cellulose microfibrils were almost double the width of the alkali pretreated sample at the temperature of 160 °C. Such enlargement led to a greater contact between cellulose chains, with a subsequent molecule alignment, as indicated by the X-ray diffraction (XRD) results with the conspicuous expansion of the average crystallite size. The delignification process had little effect on the local nanometer-sized arrangement of cellulose molecules. However, the rigidity and parallel alignment of cellulose microfibrils were partially degraded. The XRD analysis also agrees with these findings as evidenced by large momentum transfer vectors (q > 20 nm−1), interpreted as indicators of the long-range order of cell wall components, which were similar for all the studied samples except with application of the NaOH treatment at 160 °C. These changes were followed by the eventual swelling of the fiber cell walls. Based on an integrated approach, we presented multidimensional architectural models of cell wall deconstruction resulting from microwave-assisted pretreatments. We provided direct evidence supporting the idea that hemicellulose is the main barrier for the swelling of cellulose microfibrils, whereas lignin adds rigidity to cell walls. Our findings shed light on the design of more efficient strategies, not only for the conversion of biomass to fuels but also for the production of nanocellulose, which has great potential for several applications such as composites, rheology modifiers, and pharmaceuticals.

Self-reducing briquettes made with waste (silica fume, iron ore and charcoal fines) from the FeSi75 industry were studied. The objective was to determine if these briquettes could be used as a complementary load in submerged arc furnaces (SAF). Characterization of this waste was performed and the briquettes were produced without and with binders (Portland cement, hydrated lime, and sodium silicate), in accordance with the proportion of binder (2.50%; 5.00%; 7.50% and 10.00%). These self-reducing briquettes were tested for apparent density, porosity, shatter strength and resistance to hot degradation. To select the best briquettes, pre-established set points were used based on the scientific literature. Within this framework, only two treatments—out of a total of 52—met all the requirements of eligibility. In the two types of briquettes, the binder of solid silicate (5.00 and 7.50%) was produced with 15.00% of water. The briquettes have the following characteristics: apparent density: 1165 kg/m³ and 1247 kg/m³ respectively, porosity: 46.2% and 46.0%; shatter strength (1.50 m): 99.3% and 98.8%; and resistance to thermal degradation: 81.2% and 82.5%. Reduction tests to investigate the self-reducing character, under different heating temperatures (1750, 1800, 1850 and 2000 °C) were performed on these two treatments. The metallic phases that were identified by SEM/EDS analyses were Si, FeSi, FeSi₂, thus obtaining the production of FeSi50 and FeSi75, in addition to the formation of the SiC and slag. It was found that the values for SiO gas formation are in the same range as in the industrial FeSi furnace. From the results, it is possible to verify the potential for carbothermal reduction of these residues, but it is punctuated by the need for more research aimed at optimizing the mass percentage in the formulation.

Purpose: To evaluate the production of concrete from the partial replacement of Portland cement with petroleum catalyst residue (RC), generated in large quantities by the petrochemical industries, and the addition of polyethylene glycol 400 (PEG 400), with an emphasis on investigating its mechanical properties and durability, considering the technological, scientific and environmental aspects. Theoretical framework: Oil catalyst waste is generated in significant quantities and is classified as non-inert due to its metal ion content, so there is a need to investigate new disposal methods. The use of RC as partial substitute for Portland cement, with the addition of PEG 400 (self-curing agent), was investigated for the production of non-conventional concrete. The waste has pozzolanic activity, enabling improvements in mechanical properties when added to the cement matrix. PEG 400 has properties that can make concrete more effective in terms of water absorption, hydration heat and workability. The search for sustainability leads to research into new construction materials in order to preserve natural resources and reduce environmental impact. The concrete developed can be lower cost and more durable, without any loss of structural strength. Method/design/approach: The use of RC was investigated with partial substitutions of 2%, 5%, 10% and 20% in relation to the total mass of Portland cement for the manufacture of concrete and the addition of polyethylene glycol (PEG 400) as a self-curing agent. The void ratio, water absorption by capillarity and immersion, specific masses and pozzolanicity index of the waste were investigated. Mechanical and morphological characterization tests were also carried out on the concretes developed. Results and conclution: The compressive strength of concrete produced with 2% RC in relation to the total mass of cement and 1.5% PEG 400 increased by 18.3% compared to conventional concrete. An increase in the amount of residue caused a reduction in concrete strength. The sample with 1.5% PEG 400 obtained better workability in the fresh state, which may be due to the polymer acting as a self-healing agent. The images obtained by scanning electron microscopy showed that the samples containing 2% added RC had lower porosity. The study showed that the waste can be used satisfactorily in civil construction and the implementation of this new process can reduce global warming and the scarcity of mineral resources, taking sustainability into account. Research implications: This work contributes to a sustainable circular economy with a new process for using petroleum catalyst waste, with pozzolanic characteristics, in cementitious materials. Originality/value: The results will be promising for the use of petroleum catalyst waste and polyethylene glycol in the production of environmentally sustainable concrete.

The mining sector has a fundamental financial and economical role in the country where it practices these activities. In addition to employment creation and social-cultural development, the mining sector brings economic growth to the country. However, the sector is facing challenges due to COVID-19, incidents involving tailings dam facilities, rising energy costs, low grade ore deposits, restrictions in mining regulations and access to the available resources. Currently sensor-based sorting (SBS) is well known and applied worldwide in the food, recycling, grain separation industries, and processing of metals, such as diamond, gold, platinum, and feldspar. In the mining industry, ore sorting technology can result in significant improvement in ore quality by removing gangue, uplifting grades, reducing cost reduction and recovering minerals. In this article, we discuss the ore sorting test work and modeled cost-benefit analysis (CBA) for refractory gold ore at Córrego do Sítio Mineração, based on the test results and operating parameters.