Influence of processing parameters on regeneration kinetics and morphology of porous cellulose from cellulose–NaOH–water solutions

The kinetics of cellulose regeneration in acetic acid bath from cellulose–8% NaOH–water solutions and gels is studied as a function of gelation conditions, acid concentration and bath temperature. The diffusion coefficient of NaOH from cellulose solution or gel into regenerating bath was calculated. It does not depend either on gelation mode or on acid concentration. On the contrary, cellulose regeneration from non-gelled solutions is slower than from a gel. The increase in bath temperature induces diffusion coefficient increase obeying Arrhenius law. Scanning electron microscopy images of regenerated swollen-in-water freeze-dried cellulose and of the same samples dried in supercritical CO₂ show highly porous morphology. CEMEF is a Member of the European Polysaccharide Network of Excellence (EPNOE), .     

Experimental and predictive study on the performance and energy consumption characteristics for the regeneration of activated alumina assisted by ultrasound

Activated alumina used in dehumidification should be regenerated at more than 110 °C temperature, resulting in excessive energy consumption. Comparative experiments were conducted to study the feasibility and performance of ultrasonic assisted regeneration so as to lower the regeneration temperature and raise the efficiency. The mean regeneration speed, regeneration degree, and enhanced rate were used to evaluate the contribution of ultrasound in regeneration. The effective moisture diffusivity and desorption apparent activation energy were calculated by theoretical models, revealed the enhanced mechanism caused by ultrasound. Also, we proposed some specific indexes such as unit energy consumption and energy-saving ratio to assess the energy-saving characteristics of this process. The unit energy consumption was predicted by artificial neural network (ANN), and the recovered moisture adsorption of activated alumina was measured by the dynamic adsorption test. Our analysis illustrates that the introduction of power ultrasound in the process of regeneration can reduce the unit energy consumption and improve the recovered moisture adsorption, the unit energy consumption was decreased by 68.69% and the recovered moisture adsorption was improved by 16.7% under 180 W power ultrasound compared with non-ultrasonic assisted regeneration at 70 °C when initial moisture adsorption was 30%. Meanwhile, an optimal regeneration condition around the turning point could be obtained according to the predictive results of ANN, which can minimize the unit energy consumption. Moreover, it was found that a larger specific surface area of activated alumina induced by ultrasound contributed to a better recovered moisture adsorption.     

Mccrearamycins A–D,Geldanamycin‐Derived Cyclopentenone Macrolactams from an Eastern Kentucky Abandoned Coal Mine Microbe

Four cyclopentenone‐containing ansamycin polyketides (mccrearamycins A–D), and six new geldanamycins (Gdms B–G, including new linear and mycothiol conjugates), were characterized as metabolites of Streptomyces sp. AD‐23‐14 isolated from the Rock Creek underground coal mine acid drainage site. Biomimetic chemical conversion studies using both simple synthetic models and Gdm D confirmed that the mccrearamycin cyclopentenone derives from benzilic acid rearrangement of 19‐hydroxy Gdm, and thereby provides a new synthetic derivatization strategy and implicates a potential unique biocatalyst in mccrearamycin cyclopentenone formation. In addition to standard Hsp90α binding and cell line cytotoxicity assays, this study also highlights the first assessment of Hsp90α modulators in a new axolotl embryo tail regeneration (ETR) assay as a potential new whole animal assay for Hsp90 modulator discovery.     

Regeneration of a silica monolithic rod column using harsh methods followed by firm thermodynamic and kinetic validation

In this study, a numerical tool is introduced—based on thermodynamic and kinetic separation theory—for validating the regeneration of monolithic rod columns after cutting their inlet sections. A long‐used RP‐18e monolithic column was deemed to be unfit for further coffee analysis because of poor separation performance. The columns brownish inlet section was physically removed with a lathe, leaving a clean white inlet section. The original and regenerated columns were extensively analyzed and compared using numerical tools for processing adsorption data. The perturbation peak method was used to measure the adsorption isotherm of phenol on the original and regenerated monolith and the adsorption energy distributions were calculated for identifying any change in the degree of heterogeneity. Although peak shapes improved considerably after regeneration, no significant differences were found in the detailed characterization of the processed adsorption data between the original column and the regenerated one. This indicates that the removal of a section of the monolithic bed can be undertaken without damaging the column and columns in which their inlet head sections are contaminated may still function with normal adsorption behavior. In addition, the combined thermodynamic and kinetic methodology could accurately be used to evaluate any regeneration method of columns.     

[Hydroxy(tosyloxy)iodo]benzene-mediated regeneration of carbonyl compounds by cleavage of carbon nitrogen double bonds

[Hydroxy(tosyloxy)iodo]benzene (HTIB)-mediated regeneration of carbonyl compounds from various derivatives of carbonyl compounds of aryl and heteroaryl hydrazines containing adjacent nitrogen atoms is reported. These types of hydrazones cleaved oxidatively, giving back carbonyl compounds with HTIB, while cyclisation occurred with iodobenzene diacetate (IBD).     

Recent advancements in graphene adsorbents for wastewater treatment: Current status and challenges

From emerging pollutants to emerged threat, researchers are continuously looking for promising technologies for wastewater treatment. Adsorption has been identified as the most convenient approach for treating wastewater at low-cost and with high-efficiency. Recently, graphene and its derivatives have gained heightened attention as novel adsorbents because of their unique molecular structure and outstanding physicochemical properties. Heavy metals, dyes, polycyclic aromatic hydrocarbons (PAHs) and other pollutants, which are widely concerned recently, all show different adsorption behaviors. Numerous functional groups, resonating and delocalized π-electron system of graphene derivatives lead to the formation of various adsorptive interactions i.e., π-π interactions, electrostatic interactions, H-bonding, etc. with these venomous pollutants, and quarantine them in solution. The pristine form of graphene subsidiaries tends to exhibit low sorption efficiency due to high propensity of agglomeration, lack of selectivity, hydrophobicity and difficulty in phase separation after treatment. Therefore, designing of efficient graphene composites through the surface modification with numerous functional groups, polymers or nanoparticles is an ongoing challenge. Complex graphene composites are increasingly reported, but the fate of pollutants and adsorption mechanisms are still far to be fully clarified. This review summarizes the recent progresses in the application of graphene-based adsorbents for eliminating a wide range of organic and inorganic pollutants from wastewater. A critical explanation is provided on the synthesis of graphene adsorbents, systematic adsorption and desorption mechanisms along with their pollutant removal performances under different experimental conditions. A brief perspective on upcoming research needs and challenges involved in the designing of high-quality graphene-based adsorbents are highlighted.     

Role of clay-based membrane for removal of copper from aqueous solution

The present study focuses on the fabrication of polysulfone (PSf)-clay minerals impregnated hybrid membrane for treatment of Cu (II) ions. Blending and phase inversion methods have been employed to develop clay-based membranes by the mixing of bentonite, sepiolite and zeolite in the matrix of PSf. Moreover, characterization of fabricated membranes was carried out using SEM, FTIR, zeta potential, pore size and water contact angle measurement. Adsorption and filtration experiments were conducted to evaluate the permeation performance of the membrane. Obtained results of permeation study reveal that the presence of clay minerals in the matrix of modified membrane not only increases the adsorption and rejection efficiency for Cu (II) but, it also improves the flux of pure water. Among all developed membranes, the membrane prepared by the mixing of zeolite demonstrates the highest adsorption (2.82 mg/g) and rejection value (97%) towards Cu (II) at low pressure (0.5 bar). Regeneration performance results confirm the reusability of membrane up to 3–5 cycles along with 82.5–90% metal recovery. Based on significant metal recovery, clay-based low-cost zeolite/PSf membrane could be used to remove Cu (II) from water at low pressure to replace current conventional membrane.     

Preparation of mesoporous alumina electro-generated by electrocoagulation in NaCl electrolyte and application in fluoride removal with consistent regenerations

The fluoride adsorption by Electro-Generated Adsorbents (EGA) was briefly and recently shown. In this paper, the preparation of a particular EGA and its characteristics are presented. For the first time, the fluoride adsorption of one EGA was deeply investigated showing that the regeneration of this material leads to an efficient process which was better than an electrocoagulation one. The investigated adsorbent called EGA_NaCl was prepared by electrolysis in NaCl electrolyte with aluminum electrodes and was characterized by X-ray Diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), FTIR and BET studies. The physical analyses showed that EGA_NaCl was a mesoporous mixture of AlOOH and three Al(OH)₃ which contain the chlorine element and registered the surface area of 114.31 m² g⁻¹. The presence of chlorine explains the pH increase observed during the electrolysis. The fluoride adsorption as a function of pH, initial fluoride concentration, EGA_NaCl dose, temperature, co-ions and cycles of regeneration was studied using batch methods. Among the kinetic models, the pseudo – second – order model was superior to others and among the adsorption isotherms, Langmuir model fits well as compared to that of Freundlich model based on the regression coefficient values. Determination of thermodynamic parameters such as ΔH and ΔG respectively revealed the nature of endothermic and temperature – driven nature of the fluoride sorption process. The maximum adsorption capacity of EGA_NaCl was found to be 16.33 mg g⁻¹ at 27 °C and a maximum fluoride removal occurred at pH 6.55. The spent adsorbent showed the defluoridation efficiency of 95.53% up to fifth regeneration with diluted NaOH. Factorial design matrix and analysis of variance using JMP model have also been extensively discussed in this paper.     

对数伽玛与负对数伽玛分布的再生性

本文研究了随机利率的再生性问题 ,把对数正态分布具有的再生性扩展到对数伽玛分布和负对数伽玛分布上 ,同时还得到其它一些与再生性、准再生性相关的结果 .     

Reversible immobilization of proteins with streptavidin affinity tags on a surface plasmon resonance biosensor chip

Dissociation of biotin from streptavidin is very difficult due to their high binding affinity. The re-use of streptavidin-modified surfaces is therefore almost impossible, making devices containing them (e.g. surface plasmon resonance (SPR) sensor chips) expensive. This paper describes a new protocol for reversible and site-directed immobilization of proteins with streptavidin affinity tags on the streptavidin-coated SPR biosensor chip (SA chip). Two streptavidin affinity tags, nano-tag and streptavidin-binding peptide (SBP tag), were applied. They both can specifically interact with streptavidin but have weaker binding force compared to the biotin–streptavidin system, thus allowing association and dissociation under controlled conditions. The SA chip surface could be regenerated repeatedly without loss of activity by injection of 50 mM NaOH solution. The fusion construct of a SBP tag and a single-chain antibody to mature bovine prion protein (scFv-Z186-SBP) interacts with the SA chip, resulting in a single-chain-antibody-modified surface. The chip showed kinetic response to the prion antigen with equilibrium dissociation constant K _D≈4.01×10⁻⁷. All results indicated that the capture activity of the SA chip has no irreversible loss after repeated immobilization and regeneration cycles. The method should be of great benefit to various biosensors, biochips and immunoassay applications based on the streptavidin capture surface.