Electrokinetic Properties and Their Effect on Thermal Conductivity of Nanofluids

2008 ◽  
Author(s):  
S. M. Sohel Murshed ◽  
Kai Choong Leong ◽  
Chun Yang
Keyword(s):  
Thermal Conductivity ◽  
Zeta Potential ◽  
Effective Thermal Conductivity ◽  
Electrolyte Concentration ◽  
Ph Value ◽  
Deionized Water ◽  
Ph Values ◽  
Nacl Concentration ◽  
Effects Of Ph ◽  
Similar Decrease

This paper presents the effects of pH value, surfactant, and electrolyte concentration on zeta potential and effective thermal conductivity of nanofluids. The zeta potential of TiO2 (15 nm) nanoparticles in deionized water of different pH values was measured and the iso-electrical point was found to be between 4.9 and 5.2. The results show that the higher the electrolyte concentration, the smaller the particle zeta potential, which results in increased agglomeration of particles. The enhanced thermal conductivity of TiO2/deionized water-based nanofluids was found to decrease with increasing pH value or electrolyte concentration. For example, for 0.2 volume %, the thermal conductivity of this nanofluid was found to decrease from 5.5% to 2.5% when the pH value was increased from 3.4 to 9. A similar decrease (≈ 2%) in thermal conductivity was observed when NaCl concentration was increased from 0.01 mM to 10 mM. The presence of a surfactant showed considerably larger enhancement of the effective thermal conductivity compared to that of nanofluids without surfactant.

Characterization of Electrokinetic Properties of Nanofluids

2008 ◽  
Vol 8 (11) ◽  
pp. 5966-5971 ◽  
Author(s):  
S. M. Sohel Murshed ◽  
Kai Choong Leong ◽  
Chun Yang
Keyword(s):  
Thermal Conductivity ◽  
Zeta Potential ◽  
Base Fluid ◽  
Electrolyte Concentration ◽  
Ph Value ◽  
Deionized Water ◽  
Hydrodynamic Diameter ◽  
Volume Percentage ◽  
Effects Of Ph

The effects of pH value, surfactant, and electrolyte concentration on zeta potential, particle agglomeration, and thermal conductivity of nanofluids are investigated. The zeta potential of TiO2 (15 nm) nanoparticles in deionized water of different pH values was measured and the iso-electric point was found to be between 4.9 and 5.2. Addition of surfactant in the base fluid increases the zeta potential and thus increases the effective thermal conductivity of nanofluids. The results show that the higher the electrolyte concentration, the smaller the particle zeta potential, which results in increased agglomeration of particles. The enhanced thermal conductivity of TiO2/deionized water-based nanofluids was found to decrease with increasing pH value or electrolyte concentration. At 0.2 volume percentage of TiO2 nanoparticles, the decrease of thermal conductivity of nanofluids was within 2% when the pH value or electrolyte concentration was increased from 3.4 to 9 or 0.01 mM to 10 mM, respectively. The hydrodynamic diameter of agglomerated nanoparticles in base fluid was also measured and found to increase with increasing electrolyte concentration.

Adsorption of Organic Compounds on Refined Latvian Clay

2018 ◽  
Vol 788 ◽  
pp. 83-88
Author(s):  
Oskars Leščinskis ◽  
Ruta Švinka ◽  
Visvaldis Švinka
Keyword(s):  
Methyl Orange ◽  
Zeta Potential ◽  
Adsorption Capacity ◽  
Clay Minerals ◽  
Organic Compounds ◽  
Clay Mineral ◽  
Rhodamine B ◽  
Ph Value ◽  
Ftir Spectra ◽  
Ph Values

Clays are materials consisting of clay minerals and non-clay minerals. Clay mineral fraction is considered to be a nanofraction. Clay minerals can be used for water purification and treatment. Description and characterization of 3 different Latvian clay nanosized minerals from 3 different geological periods (clay Liepa from Devonian period, clay Vadakste from Triassic period and clay Apriki from Quaternary period) as well as their adsorption capacity concerning organic compounds such as methyl orange and rhodamine B are summarized. Nanosized clay mineral particles were obtained using sedimentation method. Particle size distribution, zeta potential and FTIR spectra is given. The adsorption tests of above mentioned organic compounds were carried out in water solutions at 3 different pH values. The adsorption values were determined by means of UV-spectrophotometric technique. Zeta potential values for clay minerals Apriki, Liepa and Vadakste are -40.9 mV, -49.6 mV and -43.0 mV, respectively. FTIR spectra show similar tendencies for all 3 clay minerals. The best adsorption capacity concerning methyl orange and rhodamine B were in solutions with a pH value of 2, whereas at neutral and alkaline pH values adsorption in 24 hours was not observed.

Effect of pH and Chemical Surfactant on Thermal Conductivity Enhancement of Cu-H2O Nanofluids

2008 ◽  
Author(s):  
Xinfang Li ◽  
Dongsheng Zhu ◽  
Xianju Wang ◽  
Nan Wang ◽  
Zhengdong Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Ph Value ◽  
Combined Treatment ◽  
Weight Fraction ◽  
Effect Of Ph ◽  
Conductivity Enhancement ◽  
Practical Applications ◽  
Heat Transfer Fluids ◽  
Ph Values ◽  
Thermal Constants

Nanofluids have been attractive for the last few years with the enormous potential to improve the efficiency of heat transfer fluids. This work focuses on the effect of pH and sodium dodecylbenzenesulfonate (SDBS) surfactant on the thermal conductivity of nanofluids.The thermal conductivity was measured by a Hot Disk Thermal Constants Anlyser. The results showed that the thermal conductivity enhancements of Cu–H2O nanofluids are highly dependent on the weight fraction of nanoparticle, pH values and SDBS surfactant concentration of nano-suspensions. The Cu–H2O nanofluids with an ounce of Cu have noticeably higher thermal conductivity than the base fluid without nanoparticles, For Cu nanoparticles at a weight fraction of 0.001 (0.1 wt %), thermal conductivity was enhanced by up to 10.7%, with an optimal pH value and SDBS concentration for the highest thermal conductivity. Therefore, the combined treatment with both the pH and chemical surfactant is recommended to improve the thermal conductivity for practical applications of nanofluid.

scholarly journals Influence of pH and ionic strength on the aggregation behaviors of xylan rich hemicelluloses with alkaline lignins

BioResources ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. 7608-7622
Author(s):  
Guichun Hu ◽  
Jinguang Hu ◽  
Honglei Chen ◽  
Shunxi Song ◽  
Fuqiang Chu
Keyword(s):  
Particle Size ◽  
Self Assembly ◽  
Main Chain ◽  
Ph Value ◽  
Low Ph ◽  
Ph Values ◽  
Wide Range ◽  
Nacl Concentration ◽  
Aggregation Behaviors ◽  
Influence Of Ph

The evolution of xylan-rich hemicelluloses (XH) aggregation behaviors in the presence of alkaline lignins (AL) under a wide range of pH values and NaCl concentration were investigated via dynamic light scattering and turbidity measurements. XH isolated from wheat straw contain a xylose backbone with arabinose side chains and a small amount of phenol groups. XH tend to aggregate in solution due to their low ratio of arabinose to xylose and hydrophobic phenol groups. AL interact with XH through the phenol groups bonded to the hemicellulose main chain to form an AL-XH complex. As the pH value decreases, the particle size and turbidity of AL, XH and their bonded complex all increase. The size of the AL-XH complex agglomerate is greater than the size of a XH at the same pH value, which indicates that the self-assembly of lignin molecules initiate the aggregation of XH. The particle size and turbidity of XH and AL-XH complexes increase as the XH concentration increase. At low pH values, e.g., 6.0, the particle size of the AL-XH complex more obviously increases compared to the XH particles. The size and turbidity of the AL, XH, and AL-XH complex agglomerates increased as the NaCl concentration increased.

Effects of pH Values on the Structure, Composition and Luminescence of CaWO4:Tb3+ Thin Films

2012 ◽  
Vol 531-532 ◽  
pp. 204-207
Author(s):  
Lian Ping Chen ◽  
Yuan Hong Gao
Keyword(s):  
Thin Films ◽  
Ph Value ◽  
Electrochemical Techniques ◽  
Luminescent Properties ◽  
X Ray Diffraction ◽  
Step Method ◽  
X Ray ◽  
Ph Values ◽  
Effects Of Ph ◽  
Rare Earth Doped

It is hardly possible to obtain rare earth doped CaWO4thin films directly through electrochemical techniques. A two-step method has been proposed to synthesize Tb3+-doped CaWO4thin films. X-ray diffraction, energy dispersive X-ray analysis, spectrophotometer were used to characterize their phase, composition and luminescent properties. Results reveal that Tb3+-doped CaWO4films have a tetragonal phase. The ratio of n(Tb)/[n(Ca)+n(Tb)+n(Na)] decreases with the increase of pH value of TbCl3solutions. When the pH value (adjusted by NaOH) is higher than 5, Na element has been detected in CaWO4:Tb3+thin films. Based on the analysis on the composition and luminescence, it can be concluded that the pH value of TbCl3solutions must be no higher than 9.1, otherwise, no Tb3+-doped CaWO4thin films can be obtained. Under the excitation of 237 nm, sharp emission peaks at 543 and 489 nm have been observed for Tb3+-doped CaWO4:Tb3+thin films.

scholarly journals Effects of pH and Magnetic Material on Immunomagnetic Separation of Cryptosporidium Oocysts from Concentrated Water Samples

2002 ◽  
Vol 68 (4) ◽  
pp. 2066-2070 ◽  
Author(s):  
Ryan C. Kuhn ◽  
Channah M. Rock ◽  
Kevin H. Oshima
Keyword(s):  
Magnetic Material ◽  
Water Samples ◽  
Environmental Water ◽  
Immunomagnetic Separation ◽  
Deionized Water ◽  
Ph Values ◽  
Cryptosporidium Oocysts ◽  
Optimum Ph ◽  
Effects Of Ph ◽  
Optimal Ph

ABSTRACT In this study, we examined the effect that magnetic materials and pH have on the recoveries of Cryptosporidium oocysts by immunomagnetic separation (IMS). We determined that particles that were concentrated on a magnet during bead separation have no influence on oocyst recovery; however, removal of these particles did influence pH values. The optimal pH of the IMS was determined to be 7.0. The numbers of oocysts recovered from deionized water at pH 7.0 were 26.3% higher than those recovered from samples that were not at optimal pH. The results indicate that the buffers in the IMS kit did not adequately maintain an optimum pH in some water samples. By adjusting the pH of concentrated environmental water samples to 7.0, recoveries of oocysts increased by 26.4% compared to recoveries from samples where the pH was not adjusted.

scholarly journals Zinc adsorption in highly weathered soils

2008 ◽  
Vol 43 (1) ◽  
pp. 131-139 ◽  
Author(s):  
José Carlos Casagrande ◽  
Marcio Roberto Soares ◽  
Ernesto Rinaldi Mouta
Keyword(s):  
Ionic Strength ◽  
Ph Value ◽  
Batch Adsorption ◽  
Adsorption Mechanisms ◽  
Ionic Strength Effect ◽  
Ph Values ◽  
Effects Of Ph ◽  
Ph Range ◽  
Highly Weathered Soils ◽  
Zinc Adsorption

The objective of this work was to assess the effects of pH and ionic strength upon zinc adsorption, in three highly weathered variable charge soils. Adsorption isotherms were elaborated from batch adsorption experiments, with increasing Zn concentrations (0-80 mg L-1), and adsorption envelopes were constructed through soil samples reactions with 0.01, 0.1 and 1 mol L-1 Ca(NO3)2 solutions containing 5 mg L-1 of Zn, with an increasing pH value from 3 to 8. Driving force of reaction was quantified by Gibbs free energy and separation factor. Isotherms were C-, H- and L-type and experimental results were fitted to nonlinear Langmuir model. Maximum adsorption ranged from 59-810 mg kg-1, and Zn affinity was greater in subsoil (0.13-0.81 L kg-1) than in the topsoil samples (0.01-0.34 L kg-1). Zinc adsorption was favorable and spontaneous, and showed sharply increase (20-90%) in the 4-6 pH range. No effect of ionic strength was observed at pH values below 5, because specific adsorption mechanisms predominated in the 3-5 pH range. Above pH 5, and in subsoil samples, Zn was adsorbed by electrostatic mechanisms, since ionic strength effect was observed. Despite depth and ionic strength effects, Zn adsorption depends mainly on the pH.

scholarly journals Effect of Chitosan/BSA Addition on the Physical Stability of Sunflower Oil Emulsions

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Fengyan Zhou ◽  
Guo Li ◽  
Jianying Huang
Keyword(s):  
Particle Size ◽  
Bovine Serum Albumin ◽  
Zeta Potential ◽  
Sunflower Oil ◽  
Storage Stability ◽  
Emulsion Stability ◽  
Ph Value ◽  
Physical Stability ◽  
Ph Values ◽  
Oil Emulsions

Proteins and polysaccharides are important ingredients and additives in food field. The aim of this study was to study the effect of chitosan and bovine serum albumin (BSA) solution on the physical stability of sunflower oil emulsions at different pH values, temperatures, and BSA/chitosan ratios during 20-day storage in terms of their storage stability, zeta potential, particle size, and microstructure. The results showed that pH, protein/polysaccharide ratio, and temperature significantly influenced the physical stability of emulsions at lower pH. The emulsion stability decreased as the test temperatures increased, and the storage stability of BSA/chitosan coated oil emulsions was obtained when the ratio was from 8 : 1 to 1 : 1 under 4°C for 20-day storage when pH values were 3.0 and 4.0. Droplet flocculation happened with the increase of chitosan addition and pH value.

Characteristics of wood-silica composites influenced by the pH value of silica sols

Holzforschung ◽  
2018 ◽  
Vol 72 (4) ◽  
pp. 311-319 ◽  
Author(s):  
Jun Jiang ◽  
Jinzhen Cao ◽  
Wang Wang
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Dimensional Stability ◽  
Colloidal Particle ◽  
Ph Value ◽  
Surface Hardness ◽  
X Ray ◽  
Ph Values ◽  
First Case ◽  
Silica Sols

AbstractSouthern pine (Pinusspp.) sapwood samples were impregnated with silica sols with known zeta potential and particle size distribution at various pH values (3, 5, 7, 9, 11 and 13) to produce wood-silica composites (WSiCs). The morphological and chemical properties of the composites were evaluated by scanning electron microscopy-energy dispersive X-ray (SEM-EDXA) and Fourier transform infrared (FTIR) spectroscopy. The overall performance of the composites was characterized by X-ray diffraction (XRD) and thermogravimetric (TG) analysis, and dynamic wettability tests, and their dimensional stability and surface hardness were also investigated as well. The pH value of the sols had a remarkable effect on the distribution of zeta potential and colloidal particle size, and on their penetration and distribution in the wood. The composites produced at pH 5 and pH 11 show relatively better impregnability and overall properties. In the first case the compatibility with the wood pH (ca. 5) is relevant, and at these pH values are the sol’s particle sizes low. Sols with pH around 13 resulted in inferior properties, such as increased water absorption, high thermal degradation and poor dimensional stability. This could be ascribed to wood degradation under high alkaline conditions. The results were discussed in view of the colloidal particle redistribution and the interaction between silica sol and wood.

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