Ultrasound Assisted Pretreatments Applied to Cupuaçu Husk (Theobroma grandiflorum) from Brazilian Legal Amazon for Biorefinery Concept

Cupuaçu husk (CH) is the waste of a common fruit from a native species of the Brazilian Legal Amazon. The current study investigated the influence of ultrasound (US) combined with aqueous, acid, alkaline, and ionic liquid (IL) pretreatments on the chemical and physical aspects of CH and the yield of chemical platforms production, 5-hydroxymethylfurfural (HMF) and furfural (FF), using IL. Scanning electron microscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy were used to feature the raw and pretreated biomass. The highest levels of glucose (9.90 g L-1) were observed in the liquid fraction resulting from the acid + US pretreatment followed by acid hydrolysis. The IL + US pretreatment recorded the best performance in removing lignin. Based on XRD analyses, ultrasound increased crystallinity of all pretreated samples as a result of the removal of cellulose’s amorphous fraction. However, it promoted accessibility to adopted reagents by increasing biomass exposure due to cavitation. The best yields of HMF and FF were recorded from hydrolysis of the solid fraction resulting from the acid + US (12.94%) and alkaline + US (48.84%) pretreatment, respectively. These results indicate satisfactory performance of ultrasound assisted pretreatments to the simplified and economic conversion of biomass into value-added products.

Modified Starch Highly Porous Materials

A technique for starch modification by graft polymerization of acrylamide has been developed. The obtained copolymer is soluble in a wide range of pH 2 - 12. The modification of starch made it possible to freely combine it with aqueous acid solutions of chitosan, in order to achieve a synergistic effect of their properties. A porous material based on modified starch and its mixtures with chitosan, which has high sorption characteristics, has been developed. The resulting material is promising as a sorbent of heavy metal ions and packing materials for transportation and storage.

Electrochemical And DFT Investigations of Anticorrosive Potentials of Selected Sulphonamides Based On Adsorption At Aluminium/Aqueous Acid Interface

The anticorrosive properties of six (6) selected sulphonamide derivatives on the aluminium surface were investigated in order to reveal their mechanism and mode of adsorption on Al/HCl interface, as well as the strength of the interactions between the inhibitor and Al surface. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques were utilised to evaluate the inhibition efficiencies of the selected compounds, while scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy techniques were utilised to understand the surface morphology of Al and adsorption sites of the sulphonamides. Density functional theory (DFT) calculations were utilised to investigate the strength of interactions between the inhibitor molecules and Al. Corrosive electrolyte of 1 M hydrochloric acid was employed in the study. All the studied sulphonamides showed excellent corrosion inhibition efficiencies with maximum values of up to 95%-97% at the optimum concentrations (4 × 10-5 M - 4 × 10-5 M), based on EIS measurements. The EIS parameters further revealed adsorbed film of the sulphonamides on the Al surface with capacitive-inductive characters. All the six sulphonamides reduced the corrosion current densities for both anodic and cathodic half-reactions and shifted the corrosion potentials to some anodically nobler values as revealed by the PDP data. Adsorption of the sulphonamides at the Al/HCl interface was described by the Langmuir isotherm model. Surface protection properties of the sulphonamides were further confirmed by SEM plates that showed less damaged surface of Al for the inhibited process compared to the uninhibited one. DFT results suggest that the binding energy for the inhibitors on the Al surface results in an energy that is less than 30 kJ/mol, which is an indication that the interactions are van der Waal type of interaction, suggesting physisorption mechanism.

Kinetic and Mechanism of Uncatalytic Oxidation of Dl-Threonine by Cerium (Iv) in Aqueous Acid Medium

Kinetic of uncatalyzed oxidation of DL-Threonine has been studied by Ce (IV) in acidic medium has been investigatigated by spectrophotometer technique. The rate of reaction determined at three different temperatures ranging from 298 K to 318 K at the interval of 10 K. The reaction has been found to be a first order reaction in presence or in absence of KCl, CTAB, and SDS. The rate constant, decreases with increasing the concentration of [HSO4-] and [H+] ion. The various thermodynamic parameters were calculated at 298 K, 308 K and 318 K. The proposed mechanism and results is discussed.

Extraction of Aluminum and Iron from Bauxite: A Unique Closed-Loop Ore Refining Process Utilizing Oxalate Chemistry

The Bayer process holds an exclusive status for alumina extraction, but a massive amount of caustic “red mud” waste is generated. In this work, three oxalate reagents: potassium hydrogen oxalate (KHCO), potassium tetraoxalate (KHCO·HCO), and oxalic acid (HCO) were investigated for the Al and Fe extraction process from NIST SRM 600 – Australian Darling range bauxite ore. More than 90% of Al and Fe was extracted into the aqueous phase in less than 2 h with 0.50 M CO for all three reagents. The Fe and Al can be selectively precipitated by hydrolyzing the aqueous phase. By acidifying the Al and Fe free filtrate, 80% of the CO can be precipitated as KHCO·HCO. Greater than 90% of the aqueous acid can also be recycled using a cation exchange resin. The proposed closed-loop process is an energy-efficient, cost-effective, environmentally-friendly route for extracting Al and Fe from bauxite ore.

Towards a Practical, Non-enzymatic Process for Molnupiravir from Cytidine

A scalable four step synthesis of molnupiravir from cytidine is described herein. The attractiveness of this approach is its fully chemical nature involving inexpensive reagents and more environmentally friendly solvents such as water, isopropanol, acetonitrile and acetone. Isolation and purification procedures are improved in comparison to our earlier report, as all intermediates can be isolated via aqueous acid treatment and recrystallization. The key steps in the synthesis, namely ester formation, hydroxamination and deprotection were done on multigram scale to afford molnupiravir in 36-41% yield with average purity of 98 wt% by q-NMR and 99 area % by HPLC

Towards a Practical, Non-enzymatic Process for Molnupiravir from Cytidine

A scalable four step synthesis of molnupiravir from cytidine is described herein. The attractiveness of this approach is its fully chemical nature involving inexpensive reagents and more environmentally friendly solvents such as water, isopropanol, acetonitrile and acetone. Isolation and purification procedures are improved in comparison to our earlier report, as all intermediates can be isolated via aqueous acid treatment and recrystallization. The key steps in the synthesis, namely ester formation, hydroxamination and deprotection were done on multigram scale to afford molnupiravir in 36-41% yield with average purity of 98 wt% by q-NMR and 99 area % by HPLC