Effect of speciation transformation on the coagulation behavior of Al13 and Al13 aggregates

2009 ◽  
Vol 59 (4) ◽  
pp. 815-822 ◽  
Author(s):  
Xiaohong Wu ◽  
Changqing Ye ◽  
Dongsheng Wang ◽  
Xiaopeng Ge ◽  
Hongxiao Tang
Keyword(s):  
Dominant Species ◽  
Chemical Interaction ◽  
Surface Adsorption ◽  
Surface Precipitation ◽  
Floc Size ◽  
Species Transformation ◽  
Wide Ph Range ◽  
Ph Range

Flocculation of kaolin suspension with aluminium fractal polycations was investigated as a function of aluminium concentration and pH. Aluminium flocculants included Al13 and Al13 aggregates with OH/Al ratio of 2.6 and 2.8, respectively. The flocculation kinetics and floc size distribution were monitored by light scattering. The characterization of flocculants showed that the tridecatmer Al13 and bridged [Al13]n with out-sphere structure were the dominant species for all flocculants in a wide pH range. The coagulation results indicated that the pre and in situ-formed [Al13]n play a key role in removing particles. With the increasing concentration of [Al13]n, coagulation mechanisms were transformed from charge-neutralization, electro-patch coagulation to bridge-aggregation. Moreover, sweep-flocculation was involved at higher dosage besides other three mechanisms when amorphous aluminium oxides formed. Hence, chemical interaction between particles and flocculants evolved from surface adsorption to surface precipitation for aluminium polycations by virtue of species transformation.

Enhanced electrocatalytic activity of in situ carbon encapsulated molybdenum phosphide derived from a hybrid POM for the HER over a wide pH range

2022 ◽  
Author(s):  
Balasingh Thangadurai Jebaslinhepzybai ◽  
Elavarasan Samaraj ◽  
Thangaian Kesavan ◽  
Manickam Sasidharan ◽  
J. Arockia Selvi
Keyword(s):  
Electrocatalytic Activity ◽  
Molybdenum Phosphide ◽  
Wide Ph Range ◽  
Ph Range

Hybrid polyoxometalate derived in situ carbon encapsulated molybdenum phosphide (HPOM-MoP/C) exhibits excellent HER activity in a wide pH range.

scholarly journals Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 202
Author(s):  
Miranda Martinez ◽  
Anil R. Chourasia
Keyword(s):  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Chemical Interaction ◽  
Photoelectron Spectra ◽  
X Ray ◽  
Increasing Trend ◽  
Substrate Temperatures ◽  
Beam Technique

The Ti/SnO2 interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO2 substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO2 and the titanium overlayer at the interface. The SnO2 was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO2 to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO2, elemental titanium, TiO2, and Ti-suboxide. The relative percentages of the constituents at the interface have been estimated by curve fitting the spectral data with the corresponding elemental and the oxide spectra. In the 200 °C samples, thermal diffusion of the titanium overlayer was observed. This resulted in the complete oxidation of the titanium overlayer to TiO2 upto a thickness of 0.9 nm of the overlayer. Elemental titanium resulting from the unreacted overlayer was observed to be more in the room temperature samples. The room temperature samples showed variation around 20% for the Ti-suboxide while an increasing trend was observed in the 200 °C samples.

The characterization of an SCS6/Ti–6Al–4V MMC interphase

1989 ◽  
Vol 4 (2) ◽  
pp. 327-335 ◽  
Author(s):  
C. Jones ◽  
C. J. Kiely ◽  
S. S. Wang
Keyword(s):  
Metal Matrix ◽  
Chemical Interaction ◽  
Auger Spectroscopy ◽  
Carbon Layer ◽  
Convergent Beam Electron Diffraction ◽  
Interphase Region ◽  
The Matrix ◽  
Convergent Beam

Using TEM, Auger spectroscopy, EDX, and convergent beam electron diffraction, a thorough characterization of the interphase region between SCS6 fibers and Ti–6Al–4V matrix in a metal matrix composite has been performed. The interphase region is shown to be very complex, consisting of numerous layers of varying compositions and thicknesses. The chemical interaction of the fiber and matrix results in a 0.5–1.5 μm thick TiC layer. Evidence for the existence of a Tix Siy (C) layer is also presented. The SCS6 overlayer on the fibers has inhibited any chemical interaction between the matrix and the SiC filament itself, 60% of the interphase region originating from the SCS6 protective coating. In situ fracture experiments (in an Auger spectrometer) reveal that fracture takes place between the TiC and an amorphous carbon layer.

scholarly journals Biochemical Characterization of a New β-Agarase from Cellulophaga Algicola

2019 ◽  
Vol 20 (9) ◽  
pp. 2143 ◽  
Author(s):  
Han ◽  
Zhang ◽  
Yang
Keyword(s):  
Structural Model ◽  
Biochemical Characterization ◽  
Maximum Activity ◽  
Optimal Temperature ◽  
Salt Tolerant ◽  
Wide Ph Range ◽  
Specific Activities ◽  
Ph Range ◽  
Layer Chromatography

Cellulophaga algicola DSM 14237, isolated from the Eastern Antarctic coastal zone, was found to be able to hydrolyze several types of polysaccharide materials. In this study, a predicted β-agarase (CaAga1) from C. algicola was heterologously expressed in Escherichia coli. The purified recombinant CaAga1 showed specific activities of 29.39, 20.20, 14.12, and 8.99 U/mg toward agarose, pure agar, and crude agars from Gracilaria lemaneiformis and Porphyra haitanensis, respectively. CaAga1 exhibited an optimal temperature and pH of 40 oC and 7, respectively. CaAga1 was stable over a wide pH range from 4 to 11. The recombinant enzyme showed an unusual thermostability, that is, it was stable at temperature below or equal to 40oC and around 70 oC, but was thermolabile at about 50 oC. With the agarose as the substrate, the Km and Vmax values for CaAga1 were 1.19 mg/mL and 36.21 U/mg, respectively. The reducing reagent (dithiothreitol) enhanced the activity of CaAga1 by more than one fold. In addition, CaAga1 was salt-tolerant given that it retained approximately 70% of the maximum activity in the presence of 2 M NaCl. The thin layer chromatography results indicated that CaAga1 is an endo-type β-agarase and efficiently hydrolyzed agarose into neoagarotetraose (NA4) and neoagarohexaose (NA6). A structural model of CaAga1 in complex with neoagarooctaose (NA8) was built by homology modeling and explained the hydrolysis pattern of CaAga1.

scholarly journals A Minimally Invasive Microsensor Specially Designed for Simultaneous Dissolved Oxygen and pH Biofilm Profiling

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4747 ◽  
Author(s):  
Xavier Guimerà ◽  
Ana Moya ◽  
Antonio David Dorado ◽  
Xavi Illa ◽  
Rosa Villa ◽  
...  
Keyword(s):  
Minimally Invasive ◽  
Dissolved Oxygen ◽  
Ph Monitoring ◽  
Ph Sensing ◽  
Wide Ph Range ◽  
Ph Range ◽  
Biofilm Structure ◽  
Parallel Arrays ◽  
Ph Electrodes

A novel sensing device for simultaneous dissolved oxygen (DO) and pH monitoring specially designed for biofilm profiling is presented in this work. This device enabled the recording of instantaneous DO and pH dynamic profiles within biofilms, improving the tools available for the study and the characterization of biological systems. The microsensor consisted of two parallel arrays of microelectrodes. Microelectrodes used for DO sensing were bare gold electrodes, while microelectrodes used for pH sensing were platinum-based electrodes modified using electrodeposited iridium oxide. The device was fabricated with a polyimide (Kapton®) film of 127 µm as a substrate for minimizing the damage caused on the biofilm structure during its insertion. The electrodes were covered with a Nafion® layer to increase sensor stability and repeatability and to avoid electrode surface fouling. DO microelectrodes showed a linear response in the range 0–8 mg L−1, a detection limit of 0.05 mg L−1, and a sensitivity of 2.06 nA L mg−1. pH electrodes showed a linear super-Nernstian response (74.2 ± 0.7 mV/pH unit) in a wide pH range (pH 4−9). The multi-analyte sensor array was validated in a flat plate bioreactor where simultaneous and instantaneous pH and DO profiles within a sulfide oxidizing biofilm were recorded. The electrodes spatial resolution, the monitoring sensitivity, and the minimally invasive features exhibited by the proposed microsensor improved biofilm monitoring performance, enabling the quantification of mass transfer resistances and the assessment of biological activity.

scholarly journals Synthesis of Chitosan-Functionalized Fibrous Membrane for Immobilization of Horseradish Peroxidase: Interfacial Property and Application for Catalytic Oxidation of P-Nitrophenol

2018 ◽  
Vol 13 (2) ◽  
pp. 155892501801300
Author(s):  
Cuie Wang ◽  
Xinhua Liu
Keyword(s):  
Catalytic Oxidation ◽  
Enzyme Catalysis ◽  
Fibrous Membrane ◽  
Interfacial Property ◽  
Mass Loading ◽  
Hydrophobic Polymer ◽  
Immobilization Of Enzymes ◽  
Wide Ph Range ◽  
Ph Range

A hydrophilic fibrous membrane consisting of a network of a non-crystalline hydrophobic polymer and an in situ crosslinked hydrophilic chitosan polymer is studied. This chitosan-functionalized membrane can be employed as a support for immobilization of horseradish peroxidases (HRPs). The immobilized HRPs (mass loading ~110 mg /g) show high stabilities over a wide pH range of 4~10 and temperature range of 25~60°C. In addition, the immobilized HRPs can function as a recyclable biocatalyst for catalytic oxidation of p-nitrophenol (PNP). After 10 cycles, the PNP removal efficiency is 70 percent. The results demonstrate that the chitosan-functionalized fibrous membrane is a promising support for immobilization of enzymes and has applications related to enzyme catalysis.

scholarly journals Characterization of an Alkaline Alginate Lyase with pH-Stable and Thermo-Tolerance Property

Marine Drugs ◽  
2019 ◽  
Vol 17 (5) ◽  
pp. 308 ◽  
Author(s):  
Yanan Wang ◽  
Xuehong Chen ◽  
Xiaolin Bi ◽  
Yining Ren ◽  
Qi Han ◽  
...  
Keyword(s):  
Marine Bacterium ◽  
Specific Activity ◽  
Alginate Lyase ◽  
Initial Activity ◽  
Alginate Oligosaccharides ◽  
Wide Ph Range ◽  
Encoding Gene ◽  
Ph Range ◽  
Alginate Lyases

Alginate oligosaccharides (AOS) show versatile bioactivities. Although various alginate lyases have been characterized, enzymes with special characteristics are still rare. In this study, a polysaccharide lyase family 7 (PL7) alginate lyase-encoding gene, aly08, was cloned from the marine bacterium Vibrio sp. SY01 and expressed in Escherichia coli. The purified alginate lyase Aly08, with a molecular weight of 35 kDa, showed a specific activity of 841 U/mg at its optimal pH (pH 8.35) and temperature (45 °C). Aly08 showed good pH-stability, as it remained more than 80% of its initial activity in a wide pH range (4.0–10.0). Aly08 was also a thermo-tolerant enzyme that recovered 70.8% of its initial activity following heat shock treatment for 5 min. This study also demonstrated that Aly08 is a polyG-preferred enzyme. Furthermore, Aly08 degraded alginates into disaccharides and trisaccharides in an endo-manner. Its thermo-tolerance and pH-stable properties make Aly08 a good candidate for further applications.

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