A comprehensive review on nanocatalysts and nanobiocatalysts for biodiesel production in Indonesia, Malaysia, Brazil and USA.

Biodiesel is an alternative to fossil-derived diesel with similar properties and several environmental benefits. Biodiesel production using conventional catalysts such as homogeneous, heterogeneous, or enzymatic catalysts faces a problem regarding catalysts deactivation after repeated reaction cycles. Heterogeneous nanocatalysts and nanobiocatalysts (enzymes) have shown better advantages due to higher activity, recyclability, larger surface area, and improved active sites. Despite a large number of studies on this subject, there are still challenges regarding its stability, recyclability, and scale-up processes for biodiesel production. Therefore, the purpose of this study is to review current modifications and role of nanocatalysts and nanobiocatalysts and also to observe effect of various parameters on biodiesel production. Nanocatalysts and nanobiocatalysts demonstrate long-term stability due to strong Brønsted-Lewis acidity, larger active spots and better accessibility leading to enhancethe biodiesel production. Incorporation of metal supporting positively contributes to shorten the reaction time and enhance the longer reusability. Furthermore, proper operating parameters play a vital role to optimize the biodiesel productivity in the commercial scale process due to higher conversion, yield and selectivity with the lower process cost. This article also analyses the relationship between different types of feedstocks towards the quality and quantity of biodiesel production. Crude palm oil is convinced as the most prospective and promising feedstock due to massive production, low cost, and easily available. It also evaluates key factors and technologies for biodiesel production in Indonesia, Malaysia, Brazil, and the USA as the biggest biodiesel production supply.

Effluent treatment using activated carbon adsorbents: a bibliometric analysis of recent literature.

Agricultural practices and industrial and human discharges play an important role in the generation of highly contaminated effluents, which becomes a threat to the environment. The persistence of many of these compounds to conventional treatments in recent years has meant that numerous efforts have been devoted to the proposal of new selective materials that allow the removal of these contaminants by adsorption. In addition, bibliometric studies have grown as powerful tools to indicate trends in innovation. In this way, the present study consisted of evaluating the potential interest to use activated carbon as adsorbent through a prospection study in scientific and technological databases. The number of records obtained for the use of activated carbon in effluent remediation processes is equivalent to 4898, which corresponds to approximately 2.5% of the total documents (articles/patents) found for the use of carbon with no defined purpose. A total of 2275 works that used the adsorptive property of activated carbon were recovered. According to the data recovered, Brazil is the leader in scientific publications among Latin American countries and the 12th worldwide, according to the SciELO and Scopus databases, respectively. In general, a significant number of patents have been recovered for this theme, in the Derwent database, 1167 documents were recovered. The results obtained in this work evidenced the growing interest in developing technologies in this area.

Mg-Fe layered double hydroxide with chloride intercalated: synthesis, characterization and application for efficient nitrate removal.

Mg-Fe layered double hydroxide intercalated with chloride (Mg-Fe-Cl LDH) was synthetized, characterized, and evaluated as adsorbent to remove nitrate from aqueous solution. The pH, initial nitrate concentration, adsorbent dosage, and particle size were investigated. Kinetic data was best represented by pseudo-second order model indicating that the rate limiting step was chemisorption. Intraparticle diffusion model indicates that adsorption kinetic is limited by external and intraparticle diffusion. Sips model was selected, based on R2, ARE, and AIC, to adequately represent the adsorption isotherms, which permits to affirm that the adsorption occurs in heterogeneous surface, obtaining the maximum adsorption capacity of 18.17 mg.g-1 at 30 oC. Thermodynamics parameters indicate that the adsorption was spontaneous, exothermic, and with structural modification. These findings come up with Mg-Fe-Cl LDH as a suitable adsorbent for nitrate and could contribute to its removal from the water and wastewater.

Syagrus oleracea-activated carbon prepared by vacuum pyrolysis for methylene blue adsorption.

This work aims to produce activated carbon from the endocarp of Syagrus oleracea by vacuum pyrolysis and evaluate its potential as an adsorbent. The effects of pyrolysis temperature (400 °C, 500 °C, 600 °C, and 700 °C), particle diameter (0.467 mm, 0.267 mm, and lower than 0.234 mm), and activation agent (H2SO4, H2PO3, and KOH) on the potential for methylene blue adsorption were investigated. In addition, kinetics and adsorption equilibrium were evaluated. The best condition found was particle diameter < 0.234 mm, final pyrolysis temperature of 700 °C, and using KOH. Adsorption kinetics followed pseudo-second order, with equilibrium reached within 20 min. Isotherms followed the Freundlich model. Values of adsorption capacity were in the order of 30 mg/g. Thermodynamic parameters indicated that adsorption occurred spontaneously with a reduction in the heterogeneity of the solid interface/solution. The results obtained demonstrate the great adsorption capacity of the activated carbon prepared from endocarp of Syagrus oleracea via vacuum pyrolysis for the removal of up to 98% methylene blue from aqueous solutions.