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The annual worldwide production of coffee exceeds 10 million tons, and more than 90% of this production is waste, including the husk. On the other hand, plastic consumption increases every year, and sustainable alternatives are necessary to decrease it. This work arises to solve these two problems, and seeks to produce products at an industrial level from polyethylene/coffee husk eco-composites. Both Low Density Polyethylene and High Density Polyethylene were used, and the amounts of coffee husk added as filler were 20 and 40 wt%. The composites were characterized by different morphological, thermal and mechanical techniques. Scanning Electron Microscopy images showed husk particles embedded in the polymer matrix, but with some gaps between the polymer and the filler, because no compatibilizer agent was used. The addition of large amounts of natural filler negatively affected the tensile strength and elongation at break, but increases eco-composites crystallinity, and hence, their Young modulus and hardness. The industrial applicability of the eco-composites was verified through the production of five different consumer products by extrusion and injection processes, using mixtures with 40 wt% coffee husks. All products were obtained without significant defects. If only 3.25 wt% of the polyethylene products produced each year in Colombia did so with the eco-composites developed in this work, all the coffee husk produced in the country would be used, and the emission of about 5.390 million m3 of greenhouse gases would be avoided.

Currently, in the literature, there are no general guidelines for the optimal hydraulic design of Archimedean screw turbines (AST) used in hydrokinetic applications. Therefore, this study is aiming at selecting the most significant geometric factors, such as the diameter ratio between the inner (𝐷𝑖 ) and the outer (𝐷𝑜) diameters (i.e., 𝐷𝑖/𝐷𝑜), the axle length (𝐿) and the blade stride (𝑝), influencing the AST performance by using a central composite face-centered (CCF) experimental design combined with the response surface methodology (RSM). The statistical analysis of variance (ANOVA) test identified with a significance level of 0.05 that the most significant variables on the performance of the turbine were 𝑝 and 𝐷𝑖/𝐷𝑜. The AST efficiency was evaluated by means of the power coefficient (𝐶𝑃), which was calculated by means of computational fluid dynamics (CFD) methods coupled with the 6-degrees of freedom (6-DoF) approach. The second-order polynomial model was used to predict the 𝐶𝑃 and the coefficient of determination (𝑅 2 ) was found to be 97.4%.

The ability to design the porosity of silicas, both their pore size and their wall surface, is a concern of industrial interest. Pore structure is an important parameter that determines the performance of several processes, where the surface and accessibility are vital. In this work, a MCM-41–SBA-15 mixed-phase silica (MPS) with trimodal mesoporous system and thick pore wall was synthesized by a two-step template route. For this purpose, the gel solution of a bimodal MCM-41 silica was modified by the addition of a SBA-15 template before aging stage. Low-angle XRD results confirmed that the mixed-phase silica contained a combination of both MCM-41 and SBA-15 pore structures. TEM images showed that SBA-15 structure seemed to be located on the outside of MPS particles, while MCM-41 channels were located inside. Through this synthesis route not only the wall thickness of the starting silicas was increased, but also their pores sizes were preserved in the mixed-phase silica. MPS silica was further evaluated as support for the co-catalyzed ethylene polymerization under slurry phase. The trimodal pore system and thick pore wall provided a higher catalytic activity than the individual SBA-15 and MCM-41, demonstrating the advantage of the two-step synthesis strategy conducted herein.

This paper reports on the photocatalytic activity showed by nanocomposites of TiO2 with low density polyethylene (LDPE) and high density polyethylene (HDPE) (10, 20 wt%) for the degradation of methyl orange in aqueous medium under visible light irradiation. TiO2 was synthetized by sol-gel process, and the polymers were incorporated by impregnation. Both the pure TiO2 and the nanocomposites were characterized using different physico-chemical techniques including specific surface area analysis, X-ray diffraction analysis, transmission electron microscopy, ultraviolet-visible and photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. All the prepared nanocomposites showed an absorption edge in the visible region. TiO2(90)/LDPE photocatalyst showed the best degradation efficiency after 180 minutes of reaction, without notorious decrease of degradation efficiency after three consecutive uses. Photoluminescence and X-ray photoelectron spectroscopy analyses suggested the presence of vacancies in the TiO2 structure promoted by a Ti–O–C interaction being responsible for the photocatalytic activity enhancement under visible light irradiation.

The use of fossil fuels such as coal, oil, and natural gas has allowed a fast and unprecedented development of human society. However, this has led to a continuous increase in anthropogenic CO2 emissions, which affect human life and the ecological environment through global warming and climate changes. There are various strategies to mitigate the atmospheric concentration of CO2, such as capture, separation, and utilization. Among them, CO2 hydrogenation to obtain different products through catalytic processes is a strategy of great interest. Thus, the catalytic combination of CO2 and hydrogen not only mitigates anthropogenic emissions into Earth’s atmosphere, but it also produces carbon compounds that can be used as fuel or precursors for the production of different chemicals.

Biopolymers as polylactic acid (PLA) have some drawbacks in processing and the final product is characterized by a high permeability to steam/gases and low thermal and mechanical resistance. The addition of reinforcement materials in the biopolymer matrix provides opportunities to minimize these disadvantages. Thus, this research focuses on the inclusion of non-wooden lignocellulosic fillers from bamboo Guadua angustifolia in a polymer matrix obtained from PLA. Three types of fillers were applied: sawdust, fiber from a Kraft process, and fiber with low lignin content. The blends of PLA reinforced with 5% organic fillers were performed on a torque rheometer at temperatures between 170 to 200℃ with the addition of glycerol as plasticizer and viscosity reducer of the system and maleic anhydride as compatibilizer. The evaluation on rheological, thermal, mechanical and morphological properties were investigated by rotational rheometry, differential scanning calorimetry (DSC), universal testing machine, wide angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). The results showed that the inclusion of the lignocellulosic material generated a positive response in obtaining polymeric biocomposite. The use of fibers subjected to a process of delignification with bleaching sequences OQPoPWa resulted in a greater influence on the mechanical strength, an adequate distribution of the fibers in the PLA matrix and the viscosity of the mixture.

In this work, the evaluation of a post-industrial residue of coffee industry (coffee husk) as organic filler in functionalised linear low-density polyethylene matrix was investigated. The properties of these composites were compared with more widely used inorganic fillers, such as calcium carbonate and SiO2. All the composites were prepared by grafting of linear low-density polyethylene maleic anhydride and then by melt mixing of fillers. The rheological behaviour of the compounds during processing was established to evaluate the effects of a nanosized (SiO2), micron sized calcium carbonate and coffee husk fillers. Additionally, thermal, morphological and mechanical properties of the polymer composites were evaluated. The results indicated an increase in tensile modulus and tensile strength resulting from incorporation of fillers in the polymer matrix. Some relevant modifications of melting temperature and crystallinity degree for coffee husk composites were observed, but not observed for inorganic fillers composites. The properties of the composites prepared with coffee husk were comparable to those obtained with inorganic fillers, demonstrating that this coffee residue can be used as filler for obtaining composites for many possible applications.

The design of high-performance porous adsorbents active for CO2 capture is imperative to mitigate the global climate problems arising from the accumulation of anthropogenic emissions. This work evaluates the CO2 adsorption behavior of a series of amine-functionalized silicas with different pore structures: SBA-15 (2D hexagonal), SBA-11 (3D cubic), and SiO2 (d) (disordered). The materials were synthesized using Rice Husk Ash (RHA) as a silica source and then functionalized with polyethyleneimine (PEI) by wet impregnation. CO2 adsorption performance was found to be quite sensitive to the pore features of the silica supports and the impregnated amount of PEI. Among the prepared adsorbents, the PEI/SBA-15 exhibited the highest amine utilization (0.38 mol CO2/mol N, at 20 wt.% PEI) and CO2 adsorption capacity (61.6 mg CO2/g ads., at 40 wt.% PEI) under mild conditions (40 °C and ambient pressure). The outstanding performance of this adsorbent was attributed to its uniform 2D hexagonal arrangement of cylindrical mesopores that decreases the CO2 mass transfer resistance and favors the PEI distribution through the pore network, enhancing the interaction with the CO2 stream. Further evaluation of the adsorption kinetics indicated that the CO2 capture was influenced by kinetic and thermodynamic regimes to different extents depending on the adsorption temperature.

Ordered mesoporous silicas were synthesized via cooperative self-assembly by using rice husk ash as silica source and P123 as main pore structure-directing agent. The incorporation of CTAB and BRIJ C10 as co-surfactant templates by different methods was investigated. Silicas with different pore size and mono-, bi- and trimodal porosity were obtained as a function of the co-surfactant used and the hydrolysis step performed. Low-angle XRD and TEM results confirmed the well-ordered pore structure of the synthesized silicas.

espanolEste trabajo presenta una revision de las rutas de obtencion de silice sintetica, clasificadas como de tipo termico (tambien conocido como pirogenico) y liquido, las cuales dan lugar a diferentes referencias con diversas propiedades dependiendo, no solo de las condiciones del proceso sino tambien de las caracteristicas de la materia prima. Con base en lo anterior, se hace un simil con la ceniza cascarilla de arroz (CCA) obtenida a partir de la combustion de la cascarilla de arroz, y se resaltan las principales propiedades fisico-quimicas para su utilizacion como reforzante en el sector de polimeros. En este sentido, este trabajo muestra una amplia revision de la composicion quimica, area superficial, estructura molecular y tamano de particulas de diferentes CCA encontradas en la literatura. Finalmente, se describe el desempeno mecanico de materiales termoplasticos y elastomeros reforzados con CCA reportados en la literatura y comparados con compuestos reforzados con algunas silices comerciales. EnglishThis work presents a literature review of the synthetic silica production pathways which are classified in thermal (also known as pyrogenic) and wet. They lead to different commercial references with different properties depending not only on the process conditions but also on the raw material characteristics. Based on the aforementioned, a simile is made with the rice husk ash (RHA) obtained from rice husk combustion, and its main physical-chemical properties required for its use in polymer sector are also shown. In this sense, this work shows a wide review of chemical composition, surface area, molecular structure (amorphous or crystalline) and particle size of different RHA found in literature. Finally, the mechanical performance of both thermoplastics and elastomers reinforced with RHA reported in literature is also described and compared with those composites reinforced with some commercial silica.

Nanostructured silica materials with different morphologies and adjustable pore size have been studied by researches worldwide for several applications such as catalysis, separation, adsorption, and templates for new materials. The main interest in the development of these materials is to obtain a structure with a specific combination of pore sizes for a particular application. The morphology and textural properties of pores can be easily changed with the modification of the synthesis parameters, among these, the choice of surfactant or structure directing agent (SDA).Accordingly, in this work, three types of nanostructured silica with different mesoporosity were synthesized by using of CTAB and Pluronic 123 as structure directing agents: SBA-15 and MCM-41 unimodal mesoporous silica and SBA-15/MCM-41 bimodal mesoporous silica.To evaluate the effect of surfactant on the morphology and textural properties of pores, the materials were characterized by scanning electron microscopy (SEM), X-ray Diffraction (XRD) and nitrogen sorption (BET).

In this work there was studied the effect of nano-Mg/Al hydrotalcite (NHT) as filler on maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA). NHT was synthesized by the coprecipitation method with a ratio of Mg/Al=6 and nanocomposites were prepared using 1, 3 and 5 %wt of filler via melt-blending.Morphological and structural analysis of NHT were performed and for nanocomposites, tensile tests and thermal properties were measured. Results showed that filler was well dispersed in the LLDPE matrix, mechanical properties were enhanced in most of the cases and thermal stability improvements were achieved in the nanocomposites.