Biodegradation of poly(lactic acid)—cassava bagasse composites produced by injection molding

Neat poly (lactic acid) (PLA) and PLA/cassava bagasse (CB) composites were used to produce seedling tubes by extrusion and injection molding. The tubes were buried in simulated soil, and their biodegradation was investigated by weight loss, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). After 180 days, the composites' biodegradation was higher than neat PLA material, and the higher the CB content, the higher the biodegradation, which caused fissures and voids in the material. The biodegradation of PLA/CB composites increased the phosphorus content in the soil after 180 days. Composites of PLA with CB, an abundant agro-industrial residue in Brazil, are promising because they can reduce the environmental impact due to CB's proper destination, and the composites' costs and biodegradation are faster than pure PLA material. Both the faster biodegradation of the tube and the higher P content are advantageous for seedling tubes.     

Kinetic,thermodynamic parameters and in vitro digestion of tannase from Aspergillus tamarii URM 7115

Tannase is an enzyme used in various industries and produced by a large number of microorganisms. The aim of this study was to evaluate tannase production to determine the biochemical, kinetic, and thermodynamic properties and to simulate tannase in vitro digestion. The tannase-producing fungal strain was isolated from “jamun” leaves and identified as Aspergillus tamarii. Temperature at 26°C for 67?h was the best combination for maximum tannase activity (6.35-fold; initial activity in Plackett–Burman design—15.53?U/mL and average final activity in Doehlert design—98.68?U/mL). The crude extract of tannase was optimally active at 40°C, pH 5.5 and 6.5. Moreover, tannase was stimulated by Na⁺, Ca²⁺, Mg²⁺, and Mn²⁺. The half-life at 40°C lasted 247.55?min. The free energy of Gibbs, enthalpy, and entropy, at 40°C, was 81.47, 16.85, and ?0.21?kJ/mol?·?K, respectively. After total digestion, 123.95% of the original activity was retained. Results suggested that tannase from A. tamarii URM 7115 is an enzyme of interest for industrial applications, such as gallic acid production, additive for feed industry, and for beverage manufacturing, due to its catalytic and thermodynamic properties.     

Effect of rheology and humic acids on the transport of environmental fluids: Potential implications for soil remediation revealed through microfluidics

This study investigated the potential effect of shear rheology and humic acids (HA) on the subsurface transport of polymeric fluids used for the remediation of contaminants. Polymeric fluids were prepared with guar, scleroglucan, and carboxymethyl cellulose (CMC). Guar fluids can be used to suspend reactive particles for contaminant degradation. Fluids prepared with 2.5 g/L of guar in water were viscous, and the crosslinker borax (1 g/L) made them viscoelastic. Microfluidics experiments showed that the increase in elasticity blocked the flow of guar in 350 μm channels. Guar, CMC, or scleroglucan fluids containing sodium thiosulfate can be used to trap toxic Cr(VI) in the subsurface and reduce it to harmless Cr(III). Trapping of Cr(VI) is achieved by the gelation of the fluids upon contact with chromium. Before mixing with chromium, HA did not affect the flow of CMC, guar, and scleroglucan in microfluidic channels. Quartz-crystal microbalance with dissipation monitoring experiments indicates that HA reduced sorption of guar onto silica, potentially promoting the transport of guar fluids in sandy aquifers. While HA slightly decreased the rate of gelation of CMC and scleroglucan upon contact with chromium, it did not affect the fast gelation rate of guar. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48465.     

Environmental-barrier coating ceramics for resistance against attack by molten calcia-magnesia-aluminosilicate (CMAS) glass: Part I,YAlO3 and γ-Y2Si2O7

The high-temperature (1500?°C) interactions of two promising dense, polycrystalline EBC ceramics, YAlO₃ (YAP) and γ-Y₂Si₂O₇, with a calcia-magnesia-aluminosilicate (CMAS) glass have been explored as part of a model study. Despite the fact that the optical basicities of both the EBC ceramics and the CMAS are similar, they both react with the CMAS. In the case of the Si-free YAlO₃, the reaction zone is small and it comprises three regions of reaction-crystallization products, including Y-Ca-Si apatite solid-solution (ss) and Y₃Al₅O₁₂ (YAG)(ss). In contrast, only Y-Ca-Si apatite(ss) forms in the case of Si-containing γ-Y₂Si₂O₇, and the reaction zone is an order-of-magnitude thicker. These CMAS interactions are analyzed in detail, and are found to be strikingly different than those observed in Y-free EBC ceramics (β-Yb₂Si₂O₇ and β-Sc₂Si₂O₇) in the accompanying Part II paper. This is attributed to the presence of the Y in the YAlO₃ and γ-Y₂Si₂O₇ EBC ceramics.     

Evaluation of Transport Phenomena for Removing Vanadium from Petrochemical Industry Solid Waste

Transport phenomena are investigated which are involved in the electrokinetic remediation process used for removing vanadium from deactivated catalysts from oil catalytic cracking that are currently allotted to cement plants and class-I landfills. Variables such as the concentration of electrolyte, electric potential, and applied electric current were evaluated in order to determine the effects produced by electroosmosis, diffusion, hydraulic gradient, and electromigration on the removal of vanadium from the catalyst. It was observed that migration is the most relevant phenomenon in the remediation tests, and for the best remediation condition, the migratory flow accounted for about 87 % of the vanadium removal.     

Manganese oxides treated with organic compounds as catalysts for water oxidation reaction

Manganese oxides of different crystalline structures: α-MnO₂, δ-MnO₂, α,γ-MnO₂ and Mn₂O₃; were treated with the organic compounds picolinic acid, ethylenediamine and pyridine; and were applied as catalysts in the chemical water oxidation reaction using Ce(IV) ammonium nitrate as sacrificial oxidant. The treatment led to modifications in the oxides properties, such as reduction of the particle size, increase of surface area and partial reduction of Mn⁴⁺ to Mn³⁺ for the Mn(IV) oxides, or of Mn³⁺ to Mn²⁺ for Mn₂O₃, because of favored interactions of the organic molecules with the lattice planes with higher d spacing. Oxygen evolution reaction (OER) tests showed the superior catalytic activity of the treated Mn(IV) oxides, for instance α,γ-MnO₂-en presented TOF five times higher than pure α,γ-MnO₂. The increase in surface area as well as the higher Mn³⁺ content caused by the treatment of the Mn(IV) oxides were correlated with the improvement in the OER catalytic activity.