Peculiarities of chromium electrodeposition from water − dimethylformamide solutions

Journal of Solid State Electrochemistry - Electrodeposition of chromium from both CrCl2- and CrCl3-containing dimethylformamide (DMF)–water solutions is studied. It is found that the process...     

Removal of organic micro-pollutants from water by β-cyclodextrin triazine polymers

β-Cyclodextrin (CD) polymers were synthesized by nucleophilic substitutions between β-CD with cyanuric chloride. Insoluble polymers were obtained. Polymers were characterized by DSC, TGA, FTIR, SS-¹³CNMR. Polymers and activated carbon (AC-Darco) were used to remove model micro-pollutants of bisphenol-A (BPA), 2-naphthol, 2-cholor-biphenyl (PCBNO1), benzene and dibutyl phthalate from water. The results showed that β-CD-triazine polymers showed better performance to adsorb BPA compared with activated carbon; β-CD-triazine polymer showed similar performance to activated carbon on removing benzene from water; however, it showed worse performance for removing 2-naphthol, PCBNO1 and dibutylphthalate by comparison with activated carbon. β-CD-triazine polymers with varying ratio of β-CD to cyanuric chloride were synthesized and their performance on model micro-pollutants were evaluated. Removal efficiency of micro-pollutants from water for β-CD-triazine polymers correlated with their CD concentration except for removing benzene which showed similar performance.     

Removal of high concentrations of NO3− from nuclear industrial wastewater by using a fixed-bed bioreactor

In this work, a down-flow fixed bed anaerobic biofilm reactor filled by biological ceramsites were prepared to remove the high concentration of NO₃^? (>?20 g/L) from nuclear industry wastewaters. The effects of hydraulic retention time, the concentration of NO₃^?, the molar ratio of C/N and temperature on the removal efficiencies of NO₃^? were investigated. The results showed that the removal rate of NO₃^? with the initial concentration of 6 g/L can reach 99% or more by controlling the hydraulic retention time at 0.75 h, the molar ratio of C/N at 1.5 and the temperature over 18 °C. In the process, the NO₂^? was not accumulated, and the autotrophic denitrifying bacteria grow well in anaerobic biofilm reactors, proving a usable method for removing the high concentration NO₃^? from nuclear industrial wastewaters.

     

Correction to: Peculiarities of chromium electrodeposition from water − dimethylformamide solutions

Journal of Solid State Electrochemistry - This original article contained a mistake. The page numbers of reference Kuznetsov et al. 2000 are incorrect, “853–858” should be...     

Polyethylene glycol (PEG) mediated synthesis of pyrrolo-[2,3-d]isoxazoles by using NaOCl reagent – a green chemistry approach

Abstract

Polyethylene glycol (PEG) is found to be an inexpensive, non-toxic, environmentally friendly reaction media for the synthesis of pyrrolo[2,3-d] isoxazoles by using NaOCl reagent in excellent yields under mild conditions.

1     

Solid-phase synthesis of γ-AApeptides using a submonomeric approach

The solid-phase synthesis of γ-AApeptides using a novel submonomeric approach that utilizes an allyl protection is reported. The strategy successfully circumvents the necessity of preparing γ-AApeptide building blocks in order to prepare γ-AApeptide sequences. This method will maximize the potential of developing chemically diverse γ-AApeptide libraries and thereby facilitate the biological applications of γ-AApeptides in the future.     

In situ evaluation of chromium–DNA damage using a DNA-electrochemical biosensor

The in situ evaluation of the direct interaction of chromium species with double-stranded DNA (dsDNA) was studied using differential pulse voltammetry at a glassy carbon electrode. The DNA damage was electrochemically detected following the changes in the oxidation peaks of guanosine and adenosine bases. The results obtained revealed the interaction with dsDNA of the Cr(IV) and Cr(V) reactive intermediates of Cr(III) oxidation by O₂ dissolved in the solution bound to dsDNA. This interaction leads to different modifications and causes oxidative damage in the B-DNA structure. Using polyhomonucleotides of guanine and adenine, it was shown that the interaction between reactive intermediates Cr(IV) and Cr(V)–DNA causes oxidative damage and preferentially takes place at guanine-rich segments, leading to the formation of 8-oxoguanine, the oxidation product of guanine residues and a biomarker of DNA oxidative damage. The interaction of Cr(VI) with dsDNA causes breaking of hydrogen bonds, conformational changes, and unfolding of the double helix, which enables easier access of other oxidative agents to interact with DNA, and the occurrence of oxidative damage to DNA.     

Photocatalysis applied to organic synthesis – A green chemistry approach

1. Download : Download high-res image (147KB)
2. Download : Download full-size image

     

Synthesis of amine-phenol ligands in water – a simple demonstration of a hydrophobic effect

Abstract

The synthesis in water of a series of tetradentate amine-phenol ligands derived from formaldehyde, 2,4-disubstituted phenols and amines is presented. These molecules, which are used in catalyst development, include 4,6-di-alkyl-2-bis(2-methoxyethyl)aminomethylphenols and 4,6-di-tert-amyl-2-bis(3-(dimethylamino)propyl)aminomethylphenols. Yields were generally greater than reactions performed in methanol and near quantitative for hydrophobic phenols.     

Enthalpies of glycylglycinate ion transfer from water to a water–ethanol solvent

The heat effects of mixing a sodium glycylglycinate water solution with a solvent containing from 0.0 to 0.8 mole fraction of ethanol are measured by means of calorimetry at 298.15 K. The enthalpies of sodium glycylglycinate and glycylglycinate ion transfer from water to water–ethanol solutions of different compositions are calculated. The increase of the concentration of nonaqueous component in solution leads to higher endothermicity of glycylglycinate ion transfer, resulting in weaker solvation. The contribution from the enthalpy of glycylglycinate ion resolvation to the heat effects of its complexation reactions with transition metal ions is assessed.     

Brönsted acid hydrotrope combined catalysis in water: a green approach for the synthesis of indoloquinoxalines and bis-tetronic acids

The present work describes the applications of Brönsted acid hydrotrope combined catalyst (BAHC) as a mild, efficient and reusable catalyst for synthesis of indoloquinoxalines and bis-tetronic acids in water. Using BAHC, we synthesized many indoloquinoxaline derivatives from isatins and o-phenylene diamine using 10 mol% PTSA in 40% aqueous hydrotropic (NaPTS) solution at room temperature with 83–90% yields. On the other hand, the reaction of tetronic acid with the aldehydes/isatins forms bis-tetronic acids with 83–88% yields through Knoevengel condensation-Michael addition pathway in same BHAC. Moreover, the BAHC can be recycled upto 5th cycles with slight decrease in product yields. The extremely simple operational methodology, green solvent, ambient reaction conditions and high yields render this approach extremely appealing for the synthesis of different heterocyclic compounds.

     

Speciation of chromium in water samples using dispersive liquid–liquid microextraction and flame atomic absorption spectrometry

A novel method for preconcentration is described for chromium speciation at microgram per liter to sub-microgram per liter levels. It is based on selective complex formation of both Cr(VI) and Cr(III) followed by dispersive liquid–liquid microextraction and determination by microsample introduction-flame atomic absorption spectrometry. Effects influencing complex formation and extraction (such as pH, temperature, time, solvent, salinity and the amount of chelating agent) have been optimized. Enrichment factors up to 275 and 262 were obtained for Cr(VI) and total Cr, respectively. The calibration graph is linear from 0.3 to 20 µg L^?1, and detection limits are 0.07 and 0.08 µg L^?1 for Cr(VI) and total Cr, respectively. Relative standard deviations (RSDs) were obtained to be 2.0% for Cr(VI) and 2.6% for total Cr (n?=?7).     

Treatment feasibility of highly alkaline and highly radioactive liquid waste—a novel approach

Journal of Radioanalytical and Nuclear Chemistry - Typical Radioactive liquid waste with high alkalinity, high concentration of solvent degradation products along with high 134+137Cs content was...     

COD reduction of waste water streams of active pharmaceutical ingredient – Atenolol manufacturing unit by advanced oxidation-Fenton process

Active pharmaceutical intermediates (API) in waste waters have adverse effects on aquatic life and environment. The API have high COD value and low BOD₃ and hence difficult to treat biologically. In this study, advanced oxidation processes (AOPs) utilizing the H₂O₂/Fe⁺², Fenton reactions were investigated in lab-scale experiments for the degradation of Atenolol containing waste water streams. The experimental results showed that the Fenton process using H₂O₂/Fe⁺² was the most effective treatment process. With Fenton processes, COD reduction of wastewater can be achieved successfully. It is suggested that Fenton processes are viable techniques for the degradation of Atenolol from the waste water stream with relatively low toxic by-products in the effluent which can be easily biodegraded in the activated sludge process. Hence, the Fenton process with H₂O₂/Fe⁺² is considered a suitable pretreatment method to degrade the active pharmaceutical molecules and to improve the biodegradability of waste water.     

Removal of permethrin pesticide from water by chitosan–zinc oxide nanoparticles composite as an adsorbent

Synthesis of chitosan–ZnO nanoparticles (CS–ZnONPs) composite beads was performed by a polymer-based method. The resulting bionanocomposite was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) spectroscopy and infrared spectroscopy (FT-IR). Adsorption applications for removal of pesticide pollutants were conducted. The optimum conditions, including adsorbent dose, agitating time, initial concentration of pesticide and pH on the adsorption of pesticide by chitosan loaded with zinc oxide nanoparticles beads were investigated. Results showed that 0.5 g of the bionanocomposite, in room temperature and pH 7, could remove 99% of the pesticide from permethrin solution (25 ml, 0.1 mg L⁻¹), using UV spectrophotometer at 272 nm. Then, the application of the adsorbent for pesticide removal was studied in the on-line column. The column was regenerated with NaOH solution (0.1 M) completely, and then reused for adsorption application. The CS–ZnONPs composite beads appear to be the new promising material in water treatment application with 56% regeneration after 3 cycles.     

Removal of 2,4-dichlorophenol from wasterwater by vacuum membrane distillation using hydrophobic PPESK hollow hiber membrane

2,4-Dichlorophenol was removed from wasterwater using a new hydrophobic poly(phthalazinone ether sulfone ketone) (PPESK) hollow fiber membrane by vacuum membrane distillation(VMD).     

Monitoring three typical phenol endocrine disrupting compounds in drinking water of Suzhou urban area – from raw water to tap water

In this work, three typical phenol endocrine-disrupting compounds (EDCs), namely Bisphenol A (BPA), 4-nonylphenol (4-NP) and 4-tert-octyphenol (4-t-OP), were detected in water samples from the whole drinking water supply chain of seven water plants at three hydrographic periods in Suzhou, China. Almost all of the drinking water in urban area of Suzhou city is provided by the seven water plants. Every link of drinking water supply, including raw water, finished water and tap water were monitored. The results indicated that BPA and 4-NP were detected in all samples with the concentration of 0.067–0.118 μg L^?1 and 0.111–0.350 μg L^?1, respectively, while 4-t-OP could be detected in only a few raw water samples with the concentration lower than its limit of quantitation (LOQ). The levels of BPA and 4-NP in raw water were significantly different among three hydrographic periods and the highest concentration can be observed in dry period. The difference in removal efficiency of BPA and 4-NP in seven water plants was also observed among three hydrographic periods, e.g. relative higher in dry period for BPA and in flow period for 4-NP. Potential risk assessment hinted that BPA and 4-NP in raw water showed a low to medium and a medium to high risk respectively to aquatic environment, while in tap water, the health risk from BPA and 4-NP could be ignored on human.     

Correction to: Brönsted acid hydrotrope combined catalysis in water: a green approach for the synthesis of indoloquinoxalines and bis-tetronic acids

Research on Chemical Intermediates - A correction to this paper has been published: https://doi.org/10.1007/s11164-021-04495-7     

Microwave-assisted ammonium formate-mediated synthesis of Hanstzch dihydropyridines under solvent-free conditions – a green protocol

Abstract

Microwave-assisted ammonium formate-mediated eco-friendly synthesis of structurally varied Hantzsch dihydropyridines under solvent-free conditions has been successfully accomplished with good yield, minimization of toxic reagents and organic solvents in the process. The elimination of the inorganic support decreased the disposal problem and the extremely small reaction time minimized energy dissipation.