Chemically Dual-Modified Biochar for the Effective Removal of Cr(VI) in Solution

Here, a dual-modification strategy using KMnO4 (potassium permanganate) and AlCl3·6H2O (aluminum chloride, hexahydrate) as co-modifiers to improve the Cr(VI) removal capacity of K2CO3 activated biochar is introduced. As a result, the dual-modified biochar with KMnO4 and AlCl3·6H2O has the calculated adsorption energy of −0.52 eV and −1.64 eV for HCrO4−, and −0.21 eV and −2.01 eV for Cr2O72−. The Al2O3 (aluminum oxide) and MnO (manganese oxide) embedded on the surface of dual-modified biochar bring more Cr(VI) absorption sites comparing to single-modified biochar, resulting in a maximum Cr(VI) saturated adsorption capacity of 152.86 mg g−1. The excellent removal performance is due to the synthetic effect of electrostatic attraction, reduction reaction, complexation reaction, and physical adsorption. The experimental results also indicated that the spontaneous adsorption process agreed well with the pseudo-second order and Langmuir models. This dual-modification strategy is not limited to the treatment of Cr(VI) with biochar, and may also be incorporated with the treatment of other heavy metals in aqueous environment.

Functionalized Porous Nanoscale Fe3O4 Particles Supported Biochar From Peanut Shell For Pb(II) Ions Removal From Landscape Wastewater

The large amounts of heavy metal from landscape wastewater have become serious problems of environmental pollution and risks for human health. It affects the growth of plant and aquatic, and leads to the destruction of landscape. Therefore, the development of efficient novel adsorbent is a very important for treatment of heavy metal. A low-cost and easily obtained agricultural waste (Peanut Shell) was modified by nanoscale Fe3O4 particles. Then, the functionalized porous nanoscale Fe3O4 particles supported biochar from peanut shell (PS-Fe3O4) for removal of Pb(II) ions from aqueous solution was investigated. The characterization of PS-Fe3O4 composites showed that PS from peanut shell was successfully coated with porous nanoscale Fe3O4 particles. The pseudo second-order kinetic model and Langmuir model were more fitted for describing the adsorption process of Pb(II) ions in solution. The maximum adsorption capacity of Pb(II) ions removal in solution by PS-Fe3O4 composites could reach 188.68 mg/g. The adsorption process of Pb(II) ions removal by PS-Fe3O4 composites was a spontaneous and endothermic process. The adsorption mechanisms of Pb(II) ions by PS-Fe3O4 composites were mainly controlled by the chemical adsorption process. They included Fe-O coordination reaction, co-precipitation, complexation reaction and ion exchange. PS-Fe3O4 composites were thought as a low-cost, good regeneration performance and high efficiency adsorption material for removal of Pb(II) ions in solution.

SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS

Complexation in M (II) – Rut systems (M(II) = Co, Cu) was studied by electron absorption spectroscopy and pH-metric titration in water-ethanol solutions depending on the metal: ligand ratio (1: 1; 2: 1) and the pH of the medium. It was shown that the structure and stoichiometric composition of the complexation reaction products are influenced by such basic parameters as L:M and the pH value of the medium. Depending on the pH value, chelation involves certain binding sites, which primarily is associated with the redistribution of the electron density in the flavonoid molecule. In a weakly acidic or neutral medium, regardless of the M(II): Rut ratio, the formation of monoligand complexes of rutin with 3-d metals occurs with the participation of 5-OH and 4-C=O fragments of the A and C rings, and in an alkaline medium, chelation proceeds on the catecholic fragment of ring B rutin. Biligand complexes are formed with the participation of the gydroxo groups of the catechol fragment of each rutin molecule, and the formation of compounds with a ratio of 2:1 occurs both due to 5-OH and 4C=O and due to 3 ', 4'-OH groups. The calculated values of the stability constants of the complexes showed that the stability of the Co (II) complexes is several orders of magnitude lower than the stability of the corresponding Cu (II) complexes.

A Comprehensive Numerical Model for One-Dimensional Pit Growth of 316L SS under a Salt Film

A comprehensive mathematical model, including electrode kinetics, hydrolysis and complexation reactions, salt film precipitation and pit interface movement, was developed to investigate pit growth of stainless steels 316L under a salt film. The new mathematical framework incorporates activity coefficients into the hydrolysis and complexation reaction calculations for the first time, using experimental results to parametrize the electrode kinetics in a saturated pit solution. The model was validated by 1D pit experiments and results documented in the literature. It can successfully estimate the transition potentials, salt film thickness, pit stability product, saturated pit concentration, and the pH at the pit base during pit propagation under the presence of a salt film. Moreover, the model can predict the Cr enrichment and Fe depletion in the saturated solution at the pit base, attributed to the higher diffusion coefficient of Fe and the lower Cr diffusivity.

One-Dimensional Bis(dipyrrinato)zinc(II)-Linked Porphyrinatozinc(II) Polymer: Synthesis, Exfoliation Into Single Wires, and Photofunctionality

One-dimensional bis(dipyrrinato)zinc(II)-linked porphyrinatozinc(II) polymer, 2 were synthesized by facile metal complexation reaction between 5,15-bis(3,5-dioctyloxyphenyl)-10,20-bis(dipyrrinato)porphyrinatozinc(II),1 and zinc(II) acetate. The bulky substituents on the porphyrin units allows 2 to be exfoliated into single molecular wires with a 2.8 nm height and 1.4 Om length. 2 exhibited promising photofunctionality derived from electronic interaction between bis(dipyrrinato)zinc and porphyrinatozinc(II) moieties, which can be engaged in energy transfer system such as photonic molecular wires.

DETERMINATION OF THE CONTENT OF POLYPHENOL COMPONENTS, ANTIOXIDANT AND ANTIRADICAL ACTIVITY OF ETHANOL EXTRACTS OF THE PLANT KOENIGIA WEYRICHII GROWING ON THE KOLA PENIN-SULA

Flavonoids are valuable polyphenolic compounds that accumulate in plants and have various biological activities. Koenigia Weyrichii (F. Schmidt) T.M. Schust. et Reveal is one of the plants with high flavonoid content in aerial parts. The aim of this work is to compare the total content of polyphenols, flavonoids, the total antioxidant and antiradical activity of ethanol extracts obtained from different parts of the K. Weyrichii plant growing in the Arctic zone of Russia, to compare the efficiency of ultrasonic extraction and maceration, and to determine the optimal extraction conditions. The determination of the total content of polyphenolic components was carried out using the Folin-Chocalteu reagent, the total content of flavonoids - using the complexation reaction with aluminum chloride, the total antioxidant activity - using the phosphomolybdate method, and the free radical scavenging - in the reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH). An increased yield of flavonoids is observed when maceration is used. According to the data on the total content of flavonoids, the optimal conditions for maceration (time and ratio of the components of the water-ethanol mixture) were determined. K. Weyrichii can be considered as a promising source of flavonoids and cultivated in the Arctic for further use.

SEASONAL VARIATION OF PHENOLS AND FLAVONOIDS IN NON-GALLED AND GALLED LEAVES OF CARYOCAR BRASILIENSE (CARYOCARACEAE)

Introduction: Galling insects manipulate the development of their host plants. Galls are rich in secondary metabolites, such as phenolic compounds and terpenes. Caryocar brasiliense acts as a host of galling insects. Few studies report the impacts of this plant-insect interaction on the species' morphology, physiology, and secondary metabolism. Objective: The purpose of this study was to verify if there is a correlation between the levels of total phenols and flavonoids in C. brasiliense leaf extracts and environmental variables, such as temperature and precipitation, throughout the year, and to evaluate how galling insects can interfere in this seasonality. Methods: Ethanol extracts from leaves were obtained by soxhlet extraction. The main classes of secondary metabolites were detected by phytochemical prospecting. The levels of total phenols and flavonoids were quantified by the Folin-Dennis tests and complexation reaction with aluminum chloride, respectively. Pearson 's correlation coefficient shows that the levels of phenols and flavonoids were correlated with the average monthly maximum temperatures and precipitation accumulation, respectively, recorded in Gurupi - Tocantins. Results and Discussion: Phytochemical prospecting indicated flavonoids, saponins, tannins, triterpenes, steroids, and alkaloids in both extracts. In C. brasiliense, the samples of healthy leaves suffered a greater variation in the levels of phenols (68.39±2.3 to 279.34±3.1 mg GAE g-1 extract) and flavonoids (164.06± 3.0 at 269.03±3.6 mg QE g-1 extract) compared to leaf samples with galls. A strong positive correlation was found between the contents of total phenols and maximum temperatures and a strong negative correlation with precipitation through Pearson's correlation. Conclusions: The variations observed in the levels of phenols and flavonoids in the extracts of C. brasiliense seem to be related to abiotic factors and the herbivory promoted by the galling insect.

Spectral, Crystalline, Thermal, Morphological characterization and Catalytic Performance of Ruthenium(III) Complexes of Natural Biopolymer Based on Schiff base Ligands

Aims: The aim of this study is to achieve catalytic performance for oxidation of alcohols using Ruthenium(III) metal complexes as a catalyst. Background: The chitosan is a potential candidate which enables synthesis of transition metal complexes from its corresponding bidentate ligands. Method: The chemical modification was performed on chitosan molecule with suitable aldehydes. The oxidation of alcohols was performed using ruthenium metal complexes as catalysts with Pyridinium chlorochromate (PCC) as oxidant and dichloro methane as solvent. To a solution of alcohol (2mmol) in dichloromethane (25mmol), Pyridinium chlorochromate (3 mmol) and Ruthenium(III) complexes (0.01mmol) were added. The solution was stirred for 12 h at room temperature. At the required time, the aldehyde / ketone was extracted with n-hexane. Then hexane was analyzed by GC. Results: The ruthenium(III) complexes derived from modified chitosan Schiff bidentate ligands resulted in good catalytic performance for oxidation of alcohols under optimized conditions. Conclusion: The enhanced catalytic activities of ruthenium(III) complexes were due to the presence of electron donating groups in the Schiff base ligand. : Ruthenium(III) complexes [Ru(CS)4hy3mbd)(H2O)2Cl2] and [Ru(CS)2hybd)(H2O)2Cl2] have been synthesized and characterized by FT-IR, X-ray diffraction, Thermo-gravimetric analysis and SEM with EDX. The ruthenium complexes were derived from chitosan biopolymer based Schiff base ligands. The N and O donor atoms of chitosan Schiff base ligands were involved in complexation reaction with Ruthenium metal ion to form stable coordination complex. This synthesized Ruthenium(III) complexes acted as active catalyst for the oxidation of primary and secondary alcohols which has converted to corresponding aldehydes and ketones at suitable reaction conditions. The oxidation of alcohols was performed using ruthenium metal complexes as catalyst with Pyridinium chlorochromate (PCC) as oxidant and dichloro methane as solvent.