Removal of Brilliant Green from wastewater using conventional and ultrasonically prepared poly(acrylic acid) hydrogel loaded with kaolin clay: A comparative study

The present work deals with the removal of Brilliant Green dye from wastewater using a poly(acrylic acid) hydrogel composite (PAA-K hydrogel) prepared by incorporation of kaoline clay. The composite has been synthesized using ultrasound assisted polymerization process as well as the conventional process, with an objective of showing the better effectiveness of ultrasound assisted synthesis. It has been observed that the hydrogel prepared by ultrasound assisted polymerization process showed better results. The optimum conditions for the removal of dye are pH of 7, temperature of 35 °C, initial dye concentration of 30 mg/L and hydrogel loading of 1 g. The extent of removal of dye increased with an increase in the contact time and initial dye concentration. A pseudo-second-order kinetic model has been developed to explain the adsorption kinetics of dye on the PAA-K hydrogel. Thermodynamic and kinetic parameters indicate that the adsorption process is spontaneous in nature and the PAA-K hydrogel prepared by ultrasound process is a promising adsorbent compared to conventional process. The obtained adsorption data has also been fitted into commonly used adsorption isotherms and it has been found that Freundlich as well as Langmuir adsorption isotherm models fits well to the experimental results.     

Synthesis of N‐lactosylated thiourea and benzothiazolyl thiourea

Several N‐lactosylated aryl thioureas and benzothiazolyl thioureas have been prepared by the condensation of hepta‐O‐acetyl‐β‐D ‐lactosyl isothiocyanate with aryl amines and 2‐aminobenzothiazole/substituted benzothiazoles. Hepta‐O‐acetyl‐β‐D ‐lactosyl isothiocyanate was prepared by the interaction of hepta‐O‐acetyl‐α‐D ‐lactosyl bromide and lead thiocyanate. The structures of these new N‐lactosides have been established on the basis of IR, NMR, and mass spectral studies. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:306–309, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20207     

Syntheses and antimicrobial activities of 4‐aryl‐5‐phenylimino‐3‐S‐(hepta‐O‐acetyl lactosyl)‐1,2,4‐thiadiazolines

A series of 4‐aryl‐5‐phenylimino‐3‐S‐(hepta‐O‐acetyl lactosyl)‐1,2,4‐thiadiazolines have been synthesized by the interaction of S‐(hepta‐O‐acetyl lactosyl)‐1‐arylisothiocarbamides and S‐chloro‐N‐phenyl isothiocarbamoyl chloride. The title compounds were characterized on the basis of elemental analysis and IR, NMR, mass spectral studies. The title compounds exhibited comparable antimicrobial activities against pathogens such as E. coli, S. aureus, P. vulgaris, S. typhi, A. niger, and Candida guilliermondii. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:390–392, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20310     

Synthesis of pyrrolo[2,1-f][1,2,4]triazine congeners of nucleic acid purines via the N-amination of 2-substituted pyrroles

The synthesis of several new 4-mono- and 2,4-disubstituted pyrrolo[2,1-f][1,2,4]triazines is described. Key 1-aminopyrrole-2-carbonitrile intermediates 3 and 15 were obtained by N-amination of the corresponding pyrrole-2-carboxaldehyde followed by CHO → CN conversion with either hydroxylamine-O-sulfonic acid for 3 or O-mesitylenesulfonylhydroxylamine for 15. Cyclization of 3 or 15 with a variety of amidine reagents or, after conversion of 3 to its corresponding amide, base-catalyzed annulation completed the synthesis of the title products.     

Influence of supercoiling on the disruption of dsDNA

We propose that supercoiling energizes double-stranded DNA (dsDNA) so as to facilitate thermal fluctuations to an unzipped state. We support this with a model of two elastic rods coupled via forces that represent base-pair interactions. Supercoiling is shown to lead to a distention of base pairs over a short span of dsDNA. This enhances the thermal probability for their disruption. The localized region of distention is analogous to a soliton. Our theory permits the development of an analogy between the unzipping transition and a second-order phase transition, for which the possibility of a new set of critical exponents is identified.     

Pt-CeO2/SiO2催化剂用于室温湿空气中CO氧化反应

开发室温CO氧化催化剂的主要挑战是CO自中毒和慢的表面动力学,同时湿气的存在也可导致催化剂失活.本文开发了高活性CeO2促进的Pt基催化剂4%Pt-12%CeO2/SiO2,用于室温湿气(湿度10%?90%,25°C)中CO氧化反应,在低CO浓度(<500 ppm)和高CO浓度(>2500 ppm)时,CO转化率高于99%.优化了催化剂制备变量,如Pt和CeO2负载量、CeO2沉积方法、CeO2和Pt前驱体的干燥和焙烧条件.采用CO/H2化学吸附、O2-H2滴定、X射线衍射和BET比表面积测定表征了催化剂的表面特性,并将其与催化剂活性相关联.结果表明,CeO2沉积方法对催化剂活性影响显著,当用浸渍法沉积CeO2时,所得催化剂的反应速率(5.77μmol/g/s)比用沉积沉淀法(1.96μmol g?1 s?1)或CeO2嫁接法(1.31μmol g?1 s?1)制得催化剂的高3倍.O2-H2滴定结果表明,当用浸渍法沉积CeO2时,CeO2和Pt的紧密结合导致了催化剂的高活性.催化剂载体的选择也非常重要,硅胶负载的催化剂活性(5.77μmol g?1 s?1)是氧化铝负载的(1.05μmol g?1 s?1)5倍.当反应受内扩散控制时,催化剂载体的粒径和孔结构影响非常大.另外,CeO2和Pt前驱体的干燥和焙烧条件对催化剂活性的影响至关重要.当Pt和CeO2含量分别大于2.5和15 wt%时,所得催化剂在室温条件下活性高(TOF>0.02 s?1),稳定性好(反应15 h,CO转化率≥99%).     

Chain elongation of diacylphosphatidylcholine induces fully bilayer interdigitation under atmospheric pressure

The phase transitions of dibehenoylphosphatidylcholine (C22PC) bilayer membrane were observed by differential scanning calorimetry under atmospheric pressure and light-transmittance measurements under high pressure. The constructed temperature-pressure phase diagram suggests that the gel phase at low temperatures is the interdigitated gel phase. To confirm the phase state, we performed small-angle neutron scattering and fluorescence measurements using a polarity-sensitive probe Prodan for the C22PC bilayer membrane under atmospheric pressure. The peaks obtained in both measurements clearly showed the characteristic patterns of the fully interdigitated gel phase. Taking into account of previous studies on the gel phase for long-chain PC bilayers under atmospheric pressure and our studies on the pressure-induced bilayer interdigitaion of diacyl-PCs, it turned out that the interdigitation of diacyl-PC bilayer membranes occurs when the carbon number of acyl chain reaches at least 22. The present study revealed that the interdigitation of PC bilayer membranes occurs not only by weakening the attractive force of polar head groups but also by strengthening the cohesive force of acyl chains. When dominating the force of acyl chains, the interdigitation can be induced even in a diacyl-PC bilayer membrane by only hydration under atmospheric pressure.     

Enthalpies of complex formation of dibutyl and tributyl amines with isomeric butanols

Enthalpies of complex formation (ΔH _c) of dibutyl and tributyl amines with the four isomeric butanols were determined at 30°C. The present data were compared with the previous data on isomeric butanols with monobutyl amine complexes. The ΔH _c in the case ofn-alcohol has been found to decrease by about 4·0±0·4 kJ/mole on replacement of each hydrogen atom of the NH₂ group. The branching of the butyl chain, also, decreases the strength of the complex due to steric hindrance. NCL Communication No. 3864.     

Fate of CS2 in viscose process: a chemistry perspective

Cellulose dissolution in the viscose process has been facilitated through derivatization by carbon disulphide (CS₂) at xanthation stage by converting alkali cellulose (AC) to cellulose xanthate (CX). CX formation has been always accompanied with sulphur based byproducts formation as dictated by the mechanism published in earlier study (Gondhalekar et al. (Cellulose 26 3 1595–1604, 2019)). The sulphur byproducts formed during viscose synthesis are sodium sulphide (Na₂S), sodium trithiocarbonate (Na₂CS₃: TTC) and other minor sulphur compounds. These byproducts continue to form during ripening process as dictated by time and temperature coupled with concentration of free caustic and CS₂ present in the system. These byproducts get converted into sodium sulphate (Na₂SO₄), hydrogen sulphide (H₂S), CS₂ and other sulphurous compounds during spinning. Overall, uncontrolled ripening without parametric optimization adversely impacts raw material (RM) consumption and creates sustainability challenges. Overall optimization based on viscose process fundamental insights presented in this study will effectively help in achieving operational excellence by reducing rate of undesired reactions to improve RM specific consumption and will compliment overall sustainability efforts in viscose industry.