Heteroaggregation of micro-polystyrene in the presence of amorphous iron hydroxide (ferrihydrite)

2020 ◽  
Author(s):  
Johanna Schmidtmann ◽  
Georg Papastavrou ◽  
Nicolas Helfricht ◽  
Stefan Peiffer
Keyword(s):  
Ionic Strength ◽  
Zeta Potential ◽  
Iron Hydroxide ◽  
Hydrodynamic Diameter ◽  
Plastic Pollution ◽  
Sem Images ◽  
Ph Values ◽  
Neutral Ph ◽  
Monovalent Ions ◽  
Repulsive Forces

<p>Plastic pollution in the marine and terrestrial environments is ubiquitous and a widespread problem. While the occurrence of plastics and microplastics, as well as their effects on marine and freshwater organisms, have already been investigated in numerous studies, so far only little attention has been paid to the fate, transport, and transformation processes of microplastics in the environment. In this work, the aggregation behavior of polystyrene (PS) microplastics in the presence of ferrihydrite, a natural inorganic colloid, was studied using zeta potential and hydrodynamic diameter measurements, as well as scanning electron microscope (SEM) techniques, considering the influence of pH and ionic strength. An increase of pH led to a more negative surface charge of PS. Furthermore, increasing concentrations of NaCl and CaCl<sub>2</sub> showed that mono- and divalent cations influence the zeta potential in a different way. Divalent ions compress the electric double layer more efficiently compared to monovalent ions, which resulted in a decrease of repulsive forces. Studies on the heteroaggregation between PS and ferrihydrite showed that the highest aggregation took place at neutral pH values. Aggregate sizes in samples with neutral pH increased significantly compared to more acidic and alkaline pH values. Furthermore, the results indicated that at neutral pH values, ferrihydrite completely covers the PS surface. SEM images and hydrodynamic diameter measurements revealed that the heteroaggregation between PS and ferrihydrite increased with ionic strength. Our results demonstrate that the fate of microplastic particles in aquatic systems can be strongly influenced by natural colloidal water constituents, such as iron hydroxides.</p>

scholarly journals Influence of concentration, ionic strength and pH on zeta potential and mean hydrodynamic diameter of edible polysaccharide solutions envisaged for multinanolayered films production

2011 ◽  
Vol 85 (3) ◽  
pp. 522-528 ◽  
Author(s):  
Maria G. Carneiro-da-Cunha ◽  
Miguel A. Cerqueira ◽  
Bartolomeu W.S. Souza ◽  
José A. Teixeira ◽  
António A. Vicente
Keyword(s):  
Ionic Strength ◽  
Zeta Potential ◽  
Hydrodynamic Diameter

scholarly journals Self-Assembly of Rice Bran Globulin Fibrils in Electrostatic Screening: Nanostructure and Gels

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Lihua Huang ◽  
Yehui Zhang ◽  
Haibin Li
Keyword(s):  
Ionic Strength ◽  
Rice Bran ◽  
Self Assembly ◽  
Gel Properties ◽  
Sem Images ◽  
Force Microscopy ◽  
Atomic Force ◽  
Repulsive Forces ◽  
Low Ionic Strength ◽  
Kinetics Of

The effects of various ionic strengths and protein concentrations on the fibrils structure and gel properties of rice bran globulin (RBG) at pH 2.0 were investigated using atomic force microscopy (AFM), rheometer, and scanning electron microscope (SEM). AFM images showed the morphology of assembling RBG fibrils from strand beads to becoming branch clustered, when electrostatic repulsive forces attenuated gradually with increasing ionic strength. NaCl seems to accelerate the kinetics of fibrils formation, resulting in a significant increase in Th T fluorescence intensity. The increased ionic strengths promote particle size increasing and zeta potential decreasing synchronously. The percolation modelG'~C-Cpnbe used to calculate theoretical RBG gels concentration at various ionic strengths (0–500 mM), which decreased from 15.17 ± 0.63 to 2.26 ± 0.27 wt%. SEM images exhibited a granular mesh-like gel structure. A more homogenous structure occurred in low ionic strength. This study elucidates properties of RBG fibrils and gels as a bioactive material.

A comparative antimicrobial activity study of Moringa Oleifera extracts encapsulated within ALg nanoparticles

2020 ◽  
Vol 10 ◽  
Author(s):  
Asmaa S. El-Houssiny ◽  
Ehab A. Fouad ◽  
Ahmed G. Hegazi
Keyword(s):  
Antimicrobial Activity ◽  
Zeta Potential ◽  
Pathogenic Bacteria ◽  
Moringa Oleifera ◽  
Ultrastructural Changes ◽  
Diffusion Method ◽  
Hydrodynamic Diameter ◽  
Bacterial Cells ◽  
Sem Images ◽  
Wide Range

Introduction: The encapsulations of phytochemical compounds within nanoparticles are attracting interest as a novel effective strategy to induce bacterial damage regardless of antibiotic sensitivity. Objective: The purpose of this study is to evaluate the antibacterial activities of different extracts of Moringa Oleifera combined with alginate nanoparticles (ALg NPs) against different pathogenic bacteria. Methods : The Moringa-ALg NPs were characterized by dynamic light scattering, zeta potential, and FTIR. In addition to that, the antimicrobial activities were assessed by using the agar well diffusion method. Moreover, the scanning electron microscope (SEM) was utilized to examine the ultrastructural changes induced in bacteria by Moringa-ALg NPs. In this study, the Moringa-ALg NPs have a hydrodynamic diameter of 12 nm and zeta potential of -56 mV. Results: The FTIR results indicate the successful encapsulation of Moringa within ALg NPs. On the other hand, the Moringa-ALg NPs exhibited excellent antimicrobial activity against all examined pathogens as compared to pure Moringa extracts. Furthermore, the SEM images revealed that the bacterial cells exposed to Moringa-ALg NPs had an irregular and wrinkled appearance. Conclusion: In summary, these results suggest that the Moringa-ALg NPs could be used as a powerful antibacterial agent against a wide range of microbes.

Structure of Al-humic flocs and their removal at slightly acidic and neutral pH

2002 ◽  
Vol 2 (2) ◽  
pp. 99-106 ◽  
Author(s):  
X.C. Wang ◽  
P.K. Jin ◽  
J. Gregory
Keyword(s):  
Image Analysis ◽  
Fractal Dimension ◽  
Zeta Potential ◽  
Humic Substances ◽  
Main Mechanism ◽  
Optical Monitoring ◽  
Uv Absorbance ◽  
Monitoring Techniques ◽  
Ph Values ◽  
Neutral Ph

Using microscopic and optical monitoring techniques, the process of coagulation of humic substances was studied paying attention to the structure of flocs and their settleability and filterability with information from image analysis, and HPLC, zeta potential, TOC and UV absorbance measurements. The results show that Al-humic flocs formed at pH 5.0 appear more compact with higher fractal dimension while those formed at pH 7.0 are looser with lower fractal dimension. During growth, Al-humic flocs also undergo a decrease in their fractal dimension. The attainable removal of TOC is about 40-50% at both pH values, but the optimum Al dose at pH 7.0 is about 5 times of that at pH 5.0. Charge neutralization is believed to be the main mechanism of coagulation at pH 5.0 and sweep coagulation plays an important role at pH 7.0 as well as at pH 5.0 under an overdosing condition.

scholarly journals Diamond Nanoparticles-Porphyrin mTHPP Conjugate as Photosensitizing Platform: Cytotoxicity and Antibacterial Activity

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1393
Author(s):  
Carolina Ramos Hurtado ◽  
Gabriela Ramos Hurtado ◽  
Gabrielle Lupeti de Cena ◽  
Rafaela Campos Queiroz ◽  
Alexandre Vieira Silva ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Aqueous Suspension ◽  
Membrane Damage ◽  
Covalent Bond ◽  
Bacterial Suspension ◽  
Hydrodynamic Diameter ◽  
Sem Images ◽  
Murine Embryonic Fibroblast ◽  
Diamond Nanoparticles ◽  
Bacterial Growth Inhibition

Conjugation of photosensitizers (PS) with nanoparticles has been largely used as a strategy to stabilize PS in the biological medium resulting in photosensitizing nanoparticles of enhanced photoactivity. Herein, (Meso-5, 10, 15, 20-tetrakis (3-hydroxyphenyl) phorphyryn (mTHPP) was conjugated with diamond nanoparticles (ND) by covalent bond. Nanoconjugate ND-mTHPP showed suitable stability in aqueous suspension with 58 nm of hydrodynamic diameter and Zeta potential of −23 mV. The antibacterial activity of ND-mTHPP was evaluated against Escherichia coli for different incubation times (0–24 h). The optimal activity was observed after 2 h of incubation and irradiation (660 nm; 51 J/cm2) performed right after the addition of ND-mTHPP (100 μg/mL) to the bacterial suspension. The inhibitory activity was 56% whereas ampicillin at the same conditions provided only 14% of bacterial growth inhibition. SEM images showed agglomerate of ND-mTHPP adsorbed on the bacterial cell wall, suggesting that the antimicrobial activity of ND-mTHPP was afforded by inducing membrane damage. Cytotoxicity against murine embryonic fibroblast cells (MEF) was also evaluated and ND-mTHPP was shown to be noncytotoxic since viability of cells cultured for 24 h in the presence of the nanoconjugate (100 μg/mL) was 78%. Considering the enhanced antibacterial activity and the absence of cytotoxic effect, it is possible to consider the ND-mTHPP nanoconjugate as promising platform for application in antimicrobial photodynamic therapy (aPDT).

scholarly journals Investigation of the Behavior and Mechanism of Action of Ether-Based Polycarboxylate Superplasticizers Absorption on Large Bibulous Stone Powder

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2736
Author(s):  
Zuiliang Deng ◽  
Guimin Lu ◽  
Lefeng Fu ◽  
Weishan Wang ◽  
Baicun Zheng
Keyword(s):  
Infrared Spectroscopy ◽  
Thermogravimetric Analysis ◽  
Zeta Potential ◽  
Mechanism Of Action ◽  
Water Consumption ◽  
Pore Volume ◽  
High Water ◽  
Hydrodynamic Diameter ◽  
Coarse Aggregates ◽  
Polycarboxylate Superplasticizer

The aim of this paper is to study the adsorption behavior of polycarboxylate superplasticizers (PCE) on coarse aggregates with a property of high water consumption (above 2%). The coarse aggregates were ground into a powder to create large bibulous stone powder, and it was observed that significant amounts of the ether-based PCE were absorbed onto large bibulous stone powder. The adsorption rate immediately reached a maximum after 5 min and then gradually decreased until an equilibrium absorption was established after 30 min. Zeta potential, infrared spectroscopy, and thermogravimetric analysis (TGA) measurements confirmed that the polycarboxylate superplasticizer adsorbed on the surface of the stone powder. Hydrodynamic diameter measurements showed that the polycarboxylate superplasticizer molecules were smaller than pore size, and the surface area and pore volume were reduced by the polymer incorporation in the pores.

Effects of pH and ionic strength on the cation exchange capacity of soils with variable charge

Soil Research ◽  
1981 ◽  
Vol 19 (1) ◽  
pp. 93 ◽  
Author(s):  
GP Gillman
Keyword(s):  
Ionic Strength ◽  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Exchange Capacity ◽  
Surface Soils ◽  
Ph Values ◽  
Variable Charge ◽  
Effects Of Ph ◽  
Variable Charge Soils

The cation exchange capacity of six surface soils from north Queensland and Hawaii has been measured over a range of pH values (4-6) and ionic strength values (0.003-0.05). The results show that for variable charge soils, modest changes in electrolyte ionic strength are as important in their effect on caton exchange capacity as are changes in pH values.

Formulation, Physical and Chemical Stability of Ocimum gratissimum L. Leaf Oil Nanoemulsion

2021 ◽  
Vol 901 ◽  
pp. 117-122
Author(s):  
Netnapa Ontao ◽  
Sirivan Athikomkulchai ◽  
Sarin Tadtong ◽  
Phuriwat Leesawat ◽  
Chuda Chittasupho
Keyword(s):  
Essential Oil ◽  
Zeta Potential ◽  
Chemical Stability ◽  
Polydispersity Index ◽  
Hydrodynamic Diameter ◽  
Potential Value ◽  
Yellow Color ◽  
Leaf Oil ◽  
The Stability ◽  
Physical And Chemical

Ocimum gratissimum L. leaf oil exhibited many pharmacological properties. This study aimed to formulate and evaluate the physical and chemical stability of O.gratissimum leaf oil nanoemulsion. O.gratissimum leaf oil was extracted by hydrodistillation. The major component of the essential oil eugenol, was analyzed by UV-Vis spectrophotometry. Nanoemulsions of O.gratissimum leaf oil were formulated using polysorbate 80, hyaluronic acid, poloxamer 188, and deionized water by phase inversion composition method. The hydrodynamic diameter, polydispersity index, and zeta potential value of O.gratissimum leaf oil nanoemulsion was evaluated by a dynamic light scattering technique. The %remaining of eugenol in the nanoemulsion was analyzed by UV-Vis spectrophotometry. The essential oil extracted from of O. gratissimum leaf oil was a clear, pale yellow color. The %yield of the essential oil was 0.15 ± 0.03% v/w. The size of the nanoemulsion was less than 106 nm. The polydispersity index of the nanoemulsion was ranging from 0.303 - 0.586 and the zeta potential value of the nanoemulsion was closely to zero, depending on the formulation component. O. gratissimum leaf oil at concentrations ranging from 0.002 - 0.012% v/v contained 35 - 41% of eugenol. The size of nanoemulsion was significantly decreased after storage at 4 °C, while significantly increased upon storage at 45 °C. The size of nanoemulsion stored at 30 °C did not significantly change. The %remaining of eugenol in the nanoemulsion was more than 90% after storage at 4 °C and 30 °C for 28 days. The percentage of eugenol remaining in the nanoemulsion stored at 45 °C was more than 85 - 90%, suggesting that the temperature affected the stability of eugenol in the nanoemulsion.

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