Mechanism of negative surface charge formation on biochar and its effect on the fixation of soil Cd

2020 ◽  
Vol 384 ◽  
pp. 121370 ◽  
Author(s):  
Zhongxin Tan ◽  
Shengnan Yuan ◽  
Mengfan Hong ◽  
Limei Zhang ◽  
Qiaoyun Huang
Keyword(s):  
Surface Charge ◽  
Charge Formation ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Soil Cd

Surface charge and extracellular polymer of sludge in the anaerobic degradation process

1996 ◽  
Vol 34 (5-6) ◽  
pp. 309-316 ◽  
Author(s):  
X. S. Jia ◽  
Herbert H. P. Fang ◽  
H. Furumai
Keyword(s):  
Surface Charge ◽  
Growth Phase ◽  
Anaerobic Degradation ◽  
Degradation Process ◽  
Anaerobic Sludge ◽  
Batch Experiments ◽  
High Substrate Concentration ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Extracellular Polymer

Changes of surface charge and extracellular polymer (ECP) content were investigated in batch experiments for three anaerobic sludges, each of which had been enriched at 35°C and pH 639-7.3 for more than 40 batches using propionate, butyrate and glucose, individually, as the sole substrate. Results showed that both ECP and the negative surface charge were dependent on the growth phase of microorganisms. They increased at the beginning of all batches when the microorganisms were in the prolific-growth phase, having high substrate concentration and food-to-microorganisms ratio. Both later gradually returned to their initial levels when the microorganisms were in the declined-growth phase, as the substrate became depleted. The negative surface charge increased linearly with the total-ECP content in all series with slopes of 0.0187, 0.0212 and 0.0157 meq/mg-total-ECP for sludge degrading propionate, butyrate and glucose, respectively. The change of surface charge for the first two sludges was mainly due to the increase of proteinaceous fraction of ECP; but, for glucose-degrading sludge, that could be due to the increases of both proteinaceous and carbohydrate fractions of ECP. The negative-charged nature of anaerobic sludge implies that cations should be able to promote granulation of anaerobic sludge.

scholarly journals Nanoemulsions for the Encapsulation of Hydrophobic Actives

Cosmetics ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 45
Author(s):  
Eduardo Guzmán ◽  
Laura Fernández-Peña ◽  
Lorenzo Rossi ◽  
Mathieu Bouvier ◽  
Francisco Ortega ◽  
...  
Keyword(s):  
Surface Charge ◽  
Long Term Stability ◽  
Promising Tool ◽  
Oil In Water ◽  
Nanometric Range ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Highly Hydrophobic ◽  
Technological Interest

This work analyzes the dispersion of two highly hydrophobic actives, (9Z)-N-(1,3-dihydroxyoctadecan-2-yl)octadec-9-enamide (ceramidelike molecule) and 2,6-diamino-4-(piperidin-1-yl)pyrimidine 1-oxide (minoxidil), using oil-in-water nanoemulsions with the aim of preparing stable and safe aqueous-based formulations that can be exploited for enhancing the penetration of active compounds through cosmetic substrates. Stable nanoemulsions with a droplet size in the nanometric range (around 200 nm) and a negative surface charge were prepared. It was possible to prepare formulations containing up to 2 w/w% of ceramide-like molecules and more than 10 w/w% of minoxidil incorporated within the oil droplets. This emulsions evidenced a good long-term stability, without any apparent modification for several weeks. Despite the fact that this work is limited to optimize the incorporation of the actives within the nanoemulsion-like formulations, it demonstrated that nanoemulsions should be considered as a very promising tool for enhancing the distribution and availability of hydrophobic molecules with technological interest.

SURFACE-CHARGE-ENABLED PHOTOLYTIC HYDROGEN GENERATION IN V2O5·H2O/Au NANOCONJUGATES

MRS Advances ◽  
2016 ◽  
Vol 1 (46) ◽  
pp. 3121-3126
Author(s):  
Sunith Varghese ◽  
Charuksha Walgama ◽  
Mark Wilkins ◽  
Sadagopan Krishnan ◽  
Kaan Kalkan
Keyword(s):  
Surface Charge ◽  
Hydrogen Generation ◽  
Hydrogen Reduction ◽  
Energy Levels ◽  
Sol Gel ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Current Voltage ◽  
Negative Surface ◽  
Negative Surface Charge

ABSTRACTThe present work investigates sol-gel synthesized vanadium oxyhydrate (V2O5·H2O) nanowires decorated with Au nanoparticles as potential photolytic H2 generators. As determined by UV photoelectron and optical spectroscopies, the conduction band edge of V2O5·H2O lies 0.6 eV below standard H+ reduction potential, implying no H2 can be generated. On the contrary, as measured by gas chromatography, our nanoconjugates yield reproducible light-to-hydrogen conversion efficiency of 5.3%, for the first hour of photolysis under 470 nm excitation. To explain the observed hydrogen reduction, we have hypothesized the vanadia electron energy levels are raised by some negative surface charge. With the objective of validating this hypothesis, we have performed cyclic current-voltage measurements. The derived conduction and valence band edge energies are not only consistent with the optical band gaps, but also validate the hypothesized energy increase by 1.6 eV, respectively. The negative surface charge is also corroborated by the ζ-potential. Based on the measured pH of 2.4, we attribute the negative surface charge to Lewis acid nature of the nanowires, establishing dative bonding with OH−. The present work establishes the importance of surface charge in photoelectrochemical reactions, where it can be instrumental and enabling in photolytic fuel production.

Effect of arsenate on adsorption of Zn(II) by three variable charge soils

Soil Research ◽  
2007 ◽  
Vol 45 (6) ◽  
pp. 465 ◽  
Author(s):  
Jing Liang ◽  
Ren-kou Xu ◽  
Diwakar Tiwari ◽  
An-zhen Zhao
Keyword(s):  
Zeta Potential ◽  
Surface Charge ◽  
Iron Oxides ◽  
Initial Concentration ◽  
Variable Charge ◽  
Study Results ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Enhanced Adsorption ◽  
Variable Charge Soils

The effect of arsenate on adsorption of Zn(II) in 3 variable charge soils (Hyper-Rhodic Ferralsol, Rhodic Ferralsol, and Haplic Acrisol) and the desorption of pre-adsorbed Zn(II) in the presence of arsenate were investigated in this study. Results showed that the presence of arsenate led to an increase in both the adsorption and desorption of Zn(II) in these variable charge soils. It was also suggested that the enhanced Zn(II) adsorption by arsenate was mainly due to the increase in negative surface charge of the soils induced by the specific adsorption of arsenate, and the increase in electrostatically adsorbed Zn(II) was responsible for the increase in the desorption of Zn(II). The effect of arsenate on Zn(II) adsorption primarily depends on the initial concentration of arsenate and Zn(II), the system pH, and the nature of soils. The enhanced adsorption of Zn(II) increased with the increase in the initial concentration of arsenate and the amount of arsenate adsorbed by the soils. The presence of arsenate decreased the zeta potential of soil suspensions and soil IEP and thus shifted the adsorption edge of Zn(II) to a lower pH region. The effect of arsenate on Zn(II) adsorption in these 3 soils followed the order Hyper-Rhodic Ferralsol > Rhodic Ferralsol > Haplic Acrisol, which was consistent to the contents of iron oxides in these soils and the amount of arsenate adsorbed by the soils.

Surface charge on kaolinites in aqueous suspension

Soil Research ◽  
1976 ◽  
Vol 14 (2) ◽  
pp. 197 ◽  
Author(s):  
MDA Bolland ◽  
AM Posner ◽  
JP Quirk
Keyword(s):  
Surface Charge ◽  
Positive Charge ◽  
Aqueous Suspension ◽  
Isomorphous Substitution ◽  
Ph Values ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Decreasing Ph ◽  
Ph Range ◽  
Exchange Technique

The surface charge of several natural kaolinites was measured in the pH range 3-10 using an exchange technique. The positive charge was found to increase with decreasing pH and sometimes to increase with increasing ionic strength; it occurred on the kaolinites at pH values as high as 9 and 10 and was particularly evident at high ionic strengths. The positive surface charge on kaolinites is thought to be due to exposed alumina such as is found on oxide surfaces. Aluminium was found to dissolve from kaolinite at pH values beiow about 6.5. Aluminium dissolution increased with decreasing pH and time. When the proportion of dissolved aluminium ions balancing negative surface charge was taken into account, the negative and net negative surface charge on kaolinite was concluded to be largely due to pH independent charge resulting from isomorphous substitution, together with some pH dependent charge due to exposed SiOH sites. If Na+ was the index cation, dissolved aluminium ions from the clay replaced some of the Na+ balancing the negative surface charge. However, when Cs+ was the index cation, less Cs+ balancing the negative surface charge on the clay was replaced by dissolved aluminium. As the concentration of either Na+ or Cs+ was increased, less dissolved aluminium replaced the index cation as a counteraction to the negative surface charge.

The effect of neuraminidase- and ribonuclease-susceptible surface anionic groups on the aggregation of embryonic chick neural retina cells

1981 ◽  
Vol 51 (1) ◽  
pp. 229-240
Author(s):  
D.E. Maslow ◽  
J.P. Harlos
Keyword(s):  
Cell Surface ◽  
Surface Charge ◽  
Neural Retina ◽  
Heart Cells ◽  
Cellular Interactions ◽  
Embryonic Chick ◽  
Contact Behaviour ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Anionic Groups

The role of cell surface charge in cellular interactions has been the subject of conflicting reports. The major contribution to the net cell surface negativity of all mammalian cells studied is made by the sialic acid moieties of the surface glycoproteins, while ribonuclease-susceptible sites have been shown to contribute to the lesser extent on some cell types. Experiments were done to determine whether these anionic groups at the cell periphery affect the aggregation and sorting behaviour of embryonic chick neural retina cells when cultured alone or in combination with embryonic heart cells. The net negative surface charge density, as determined by cell electrophoretic mobility, of neuraminidase- or ribonuclease-treated cells was significantly decreased immediately after incubation with the enzymes, and the treatment with neuraminidase resulted in a reduction in the binding of colloidal iron hydroxide particles at the cell surface. Both enzymes caused reduced aggregate size in gyratory shaker cultures of neural retina and mixed cell suspensions, and fewer neural retina cells adherent to microtest plate surfaces, but no differences were seen in their histological appearance or sorting pattern in mixed shaker culture. The results indicate that the neuraminidase- and ribonuclease-susceptible groups at the periphery of embryonic neural retina cells play a role in some aspects of cell contact behaviour in ways other than reduction in net negative surface charge.

Algal cells and coagulation, flocculation and sedimentation processes

1997 ◽  
Vol 36 (4) ◽  
pp. 111-118 ◽  
Author(s):  
A. J. H. Pieterse ◽  
A. Cloot
Keyword(s):  
Surface Charge ◽  
Van Der Waals ◽  
Morphological Characteristics ◽  
Van Der Waals Forces ◽  
Metabolic Processes ◽  
Interaction Mechanisms ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Photosynthesis And Respiration ◽  
Sedimentation Processes

Flocculation generally removes two classes of suspended particles during adsorption-coagulation, namely colloids (inorganic in nature) and bacterial and algal cells, colonies, and filaments (organic in nature). Different interaction mechanisms, i.e. hydrodynamic, electrical and electromagnetic, play important roles in the removal of algal and colloidal entities. Algal entities, however, show morphological characteristics (such as elongated shapes, arranged in cells, colonies and filaments, containing spines or able to change shape or to move with flagella) not shared by colloids, that will affect the flocculation of the algal cells. If algal cells are globally in equilibrium with themselves, it is possible that the negative surface charge of algal cells will be restored after charge neutralisation. In addition to Van der Waals forces, affecting the coagulation of colloidal and algal entities, the flocculation of algal entities may also be affected by gravitation forces (because of larger sized algal entities) and forces created in the immediate vicinity of the cells by metabolic processes such as photosynthesis and respiration.

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