Different Surface Charged Plastic Particles Have Different Cotransport Behaviors with Kaolinite Particles in Porous Media

2021 ◽  
Author(s):  
Meng Li ◽  
Lei He ◽  
Xiangwei Zhang ◽  
Haifeng Rong ◽  
Meiping Tong
Keyword(s):  
Porous Media ◽  
Ionic Strength ◽  
Surface Charge ◽  
Fate And Transport ◽  
Natural Environments ◽  
Charge Heterogeneity ◽  
Clay Particles ◽  
Highly Correlated ◽  
Ubiquitous Presence ◽  
Positively Charged

<p>The wide utilization of plastic related products leads to the ubiquitous presence of plastic particles in natural environments. Plastic particles could interact with kaolinite (one type of typical clay particles abundant in environment) and form plastic-kaolinite heteroaggregates. The fate and transport of both plastic particles and kaolinite particles thus might be altered. The cotransport and deposition behaviors of micron-sized plastic particles (MPs) with different surface charge (both negative and positive surface charge) with kaolinite in porous media in both 5 and 25 mM NaCl solutions were investigated in present study. Both types of MPs (negatively charged carboxylate-modified MPs (CMPs) and positively charged amine-modified MPs (AMPs)) formed heteroaggregates with kaolinite particles under both solution conditions examined, however, CMPs and AMPs exhibited different cotransport behaviors with kaolinite. Specifically, the transport of both CMPs and kaolinite was increased under both ionic strength conditions when kaolinite and CMPs were copresent in suspensions. While, when kaolinite and positively charged AMPs were copresent in suspensions, negligible transport of both kaolinite and AMPs were observed under examined salt solution conditions. The competition deposition sites by kaolinite (the portion suspending in solution) with CMPs-kaolinite heteroaggregates led to the increased transport both CMPs and kaolinite when both types of colloids were copresent. In contrast, the formation of larger sized AMPs-kaolinite heteroaggregates with surface charge heterogeneity led to the negligible transport of both kaolinite and AMPs when they were copresent in suspensions. The results of this study show that when plastic particles and kaolinite particles are copresent in natural environments, their interaction with each other will affect their transport behaviors in porous media. The alteration in the transport of MPs or kaolinite (either increased or decreased transport) is highly correlated with the surface charge of MPs.</p>

Transport and retention of nanoplastic particles in saturated columns packed with iron oxyhydroxide-coated sand

2020 ◽  
Author(s):  
Taotao Lu ◽  
Benjamin S. Gilfedder ◽  
Sven Frei
Keyword(s):  
Porous Media ◽  
Surface Charge ◽  
Energy Barrier ◽  
Dlvo Theory ◽  
Breakthrough Curves ◽  
Solution Chemistry ◽  
Iron Oxyhydroxide ◽  
Charge Heterogeneity ◽  
Sand Surface ◽  
Coated Sand

<p>With the increasing use of nanoplastic products in our daily life, these particles will invariably enter into the subsurface environment. It is, therefore, vital to understand the transport and retention of nanoplastic particles in groundwater systems. Surface charge heterogeneity is one of the basic chemical-physical characteristics of aquifer materials, but little research has been conducted on this topic. This study aimed to understand how the interaction between the porous media, solution chemistry, and NP surface charge influences the transport and retention of PS-NPs in the subsurface. 25 mg/L polystyrene nanoplastic particles (PS-NPs) were injected into columns packed with iron oxyhydroxide-coated sand. In addition, factors such as the content of iron oxyhydroxide-coated sand (λ), pH, ionic strength (IS), and cation valence were systematically studied. DLVO theory was used to evaluate the interactions between PS-NP and the porous media. By comparing the breakthrough curves (BTCs) of PS-NPs, it was clear that all these variables exerted a significant influence on the mobility of PS-NPs in the columns. These effects could be explained by the following: Firstly, by applying the DLVO theory, it was possible to model the electrostatic interaction between quartz sand and PS-NPs. For instance, at different IS (NaCl), the maximum energy barrier (<em>Φ</em><sub>max</sub>) decreased with an increase in IS, which meant PS-NPs could more easily overcome the energy barrier to deposited on the sand surface at higher IS. Secondly, the positively charged iron oxyhydroxide coating provided additional favorable deposition sites for negatively charged PS-NPs. However, when the pH of the solution exceeded the iron oxyhydroxide pH<sub>pzc</sub> (~pH 9), the iron coating became negative and increased the mobility of PS-NPs. Finally, bridging agents, such as Ca<sup>2+</sup> and Ba<sup>2+</sup>, resulted in the significant deposition of PS-NPs on the sand due to the bridging effect connecting the porous media and PS-NPs through the O-containing functional groups on both plastic and mineral surfaces. This study provides a better understanding of how the charge heterogeneity on aquifer materials and groundwater hydrochemistry affect the transport of PS-NPs in aquifers.</p>

Effect of Polyphosphate on Removal of Endocrine-Disrupting Chemicals of Nonylphenol and Bisphenol-A by Activated Carbons

2005 ◽  
Vol 40 (4) ◽  
pp. 484-490 ◽  
Author(s):  
Keun J. Choi ◽  
Sang G. Kim ◽  
Chang W. Kim ◽  
Seung H. Kim
Keyword(s):  
Activated Carbon ◽  
Bisphenol A ◽  
Surface Charge ◽  
Activated Carbons ◽  
Endocrine Disrupting Chemicals ◽  
Dipole Interaction ◽  
High Affinity ◽  
Calcium Polyphosphate ◽  
Endocrine Disrupting ◽  
Positively Charged

Abstract This study examined the effect of polyphosphate on removal of endocrine-disrupting chemicals (EDCs) such as nonylphenol and bisphenol-A by activated carbons. It was found that polyphosphate aided in the removal of nonylphenol and bisphenol- A. Polyphosphate reacted with nonylphenol, likely through dipole-dipole interaction, which then improved the nonylphenol removal. Calcium interfered with this reaction by causing competition. It was found that polyphosphate could accumulate on carbon while treating a river. The accumulated polyphosphate then aided nonylphenol removal. The extent of accumulation was dependent on the type of carbon. The accumulation occurred more extensively with the wood-based used carbon than with the coal-based used carbon due to the surface charge of the carbon. The negatively charged wood-based carbon attracted the positively charged calcium-polyphosphate complex more strongly than the uncharged coal-based carbon. The polyphosphate-coated activated carbon was also effective in nonylphenol removal. The effect was different depending on the type of carbon. Polyphosphate readily attached onto the wood-based carbon due to its high affinity for polyphosphate. The attached polyphosphate then improved the nonylphenol removal. However, the coating failed to attach polyphosphate onto the coal-based carbon. The nonylphenol removal performance of the coal-based carbon remained unchanged after the polyphosphate coating.

scholarly journals Surface charge modulation of rifampicin-loaded PLA nanoparticles to improve antibiotic delivery in Staphylococcus aureus biofilms

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
David Da Costa ◽  
Chloé Exbrayat-Héritier ◽  
Basile Rambaud ◽  
Simon Megy ◽  
Raphaël Terreux ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Surface Charge ◽  
Treatment Efficacy ◽  
Particle Migration ◽  
Bacterial Biofilm ◽  
Poly Lactic Acid ◽  
Retention Capacity ◽  
The Impact ◽  
Positively Charged ◽  
Antibiotic Delivery

Abstract Background After the golden age of antibiotic discovery, bacterial infections still represent a major challenge for public health worldwide. The biofilm mode of growth is mostly responsible for chronic infections that current therapeutics fail to cure and it is well-established that novel strategies must be investigated. Particulate drug delivery systems are considered as a promising strategy to face issues related to antibiotic treatments in a biofilm context. Particularly, poly-lactic acid (PLA) nanoparticles present a great interest due to their ability to migrate into biofilms thanks to their submicronic size. However, questions still remain unresolved about their mode of action in biofilms depending on their surface properties. In the current study, we have investigated the impact of their surface charge, firstly on their behavior within a bacterial biofilm, and secondly on the antibiotic delivery and the treatment efficacy. Results Rifampicin-loaded PLA nanoparticles were synthetized by nanoprecipitation and characterized. A high and superficial loading of rifampicin, confirmed by an in silico simulation, enabled to deliver effective antibiotic doses with a two-phase release, appropriate for biofilm-associated treatments. These nanoparticles were functionalized with poly-l-lysine, a cationic peptide, by surface coating inducing charge reversal without altering the other physicochemical properties of these particles. Positively charged nanoparticles were able to interact stronger than negative ones with Staphylococcus aureus, under planktonic and biofilm modes of growth, leading to a slowed particle migration in the biofilm thickness and to an improved retention of these cationic particles in biofilms. While rifampicin was totally ineffective in biofilms after washing, the increased retention capacity of poly-l-lysine-coated rifampicin-loaded PLA nanoparticles has been associated with a better antibiotic efficacy than uncoated negatively charged ones. Conclusions Correlating the carrier retention capacity in biofilms with the treatment efficacy, positively charged rifampicin-loaded PLA nanoparticles are therefore proposed as an adapted and promising approach to improve antibiotic delivery in S. aureus biofilms.

scholarly journals Gain-of-Function Mutations in the Phospholipid Flippase MprF Confer Specific Daptomycin Resistance

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Christoph M. Ernst ◽  
Christoph J. Slavetinsky ◽  
Sebastian Kuhn ◽  
Janna N. Hauser ◽  
Mulugeta Nega ◽  
...  
Keyword(s):  
Surface Charge ◽  
Bacterial Resistance ◽  
Resistance Mechanism ◽  
Point Mutations ◽  
Content Type ◽  
Calcium Dependent ◽  
Lipopeptide Antibiotics ◽  
Lipopeptide Antibiotic ◽  
Positively Charged ◽  
Phospholipid Flippase

ABSTRACTDaptomycin, a calcium-dependent lipopeptide antibiotic whose full mode of action is still not entirely understood, has become a standard-of-care agent for treating methicillin-resistantStaphylococcus aureus(MRSA) infections. Daptomycin-resistant (DAP-R)S. aureusmutants emerge during therapy, featuring isolates which in most cases possess point mutations in themprFgene. MprF is a bifunctional bacterial resistance protein that synthesizes the positively charged lipid lysyl-phosphatidylglycerol (LysPG) and translocates it subsequently from the inner membrane leaflet to the outer membrane leaflet. This process leads to increased positiveS. aureussurface charge and reduces susceptibility to cationic antimicrobial peptides and cationic antibiotics. We characterized the most commonly reported MprF mutations in DAP-RS. aureusstrains in a defined genetic background and found that only certain mutations, including the frequently reported T345A single nucleotide polymorphism (SNP), can reproducibly cause daptomycin resistance. Surprisingly, T345A did not alter LysPG synthesis, LysPG translocation, or theS. aureuscell surface charge. MprF-mediated DAP-R relied on a functional flippase domain and was restricted to daptomycin and a related cyclic lipopeptide antibiotic, friulimicin B, suggesting that the mutations modulate specific interactions with these two antibiotics. Notably, the T345A mutation led to weakened intramolecular domain interactions of MprF, suggesting that daptomycin and friulimicin resistance-conferring mutations may alter the substrate range of the MprF flippase to directly translocate these lipopeptide antibiotics or other membrane components with crucial roles in the activity of these antimicrobials. Our study points to a new mechanism used byS. aureusto resist calcium-dependent lipopeptide antibiotics and increases our understanding of the bacterial phospholipid flippase MprF.IMPORTANCEEver since daptomycin was introduced to the clinic, daptomycin-resistant isolates have been reported. In most cases, the resistant isolates harbor point mutations in MprF, which produces and flips the positively charged phospholipid LysPG. This has led to the assumption that the resistance mechanism relies on the overproduction of LysPG, given that increased LysPG production may lead to increased electrostatic repulsion of positively charged antimicrobial compounds, including daptomycin. Here we show that the resistance mechanism is highly specific and relies on a different process that involves a functional MprF flippase, suggesting that the resistance-conferring mutations may enable the flippase to accommodate daptomycin or an unknown component that is crucial for its activity. Our report provides a new perspective on the mechanism of resistance to a major antibiotic.

scholarly journals Bulk and Surface Aqueous Speciation of Calcite: Implications for Low-Salinity Waterflooding of Carbonate Reservoirs

SPE Journal ◽  
2017 ◽  
Vol 23 (01) ◽  
pp. 84-101 ◽  
Author(s):  
Maxim P. Yutkin ◽  
Himanshu Mishra ◽  
Tadeusz W. Patzek ◽  
John Lee ◽  
Clayton J. Radke
Keyword(s):  
Ionic Strength ◽  
Ion Exchange ◽  
Crude Oil ◽  
Surface Charge ◽  
Double Layer ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Diffuse Double Layer ◽  
Low Salinity ◽  
Low Salinity Waterflooding

Summary Low-salinity waterflooding (LSW) is ineffective when reservoir rock is strongly water-wet or when crude oil is not asphaltenic. Success of LSW relies heavily on the ability of injected brine to alter surface chemistry of reservoir crude-oil brine/rock (COBR) interfaces. Implementation of LSW in carbonate reservoirs is especially challenging because of high reservoir-brine salinity and, more importantly, because of high reactivity of the rock minerals. Both features complicate understanding of the COBR surface chemistries pertinent to successful LSW. Here, we tackle the complex physicochemical processes in chemically active carbonates flooded with diluted brine that is saturated with atmospheric carbon dioxide (CO2) and possibly supplemented with additional ionic species, such as sulfates or phosphates. When waterflooding carbonate reservoirs, rock equilibrates with the injected brine over short distances. Injected-brine ion speciation is shifted substantially in the presence of reactive carbonate rock. Our new calculations demonstrate that rock-equilibrated aqueous pH is slightly alkaline quite independent of injected-brine pH. We establish, for the first time, that CO2 content of a carbonate reservoir, originating from CO2-rich crude oil and gas, plays a dominant role in setting aqueous pH and rock-surface speciation. A simple ion-complexing model predicts the calcite-surface charge as a function of composition of reservoir brine. The surface charge of calcite may be positive or negative, depending on speciation of reservoir brine in contact with the calcite. There is no single point of zero charge; all dissolved aqueous species are charge determining. Rock-equilibrated aqueous composition controls the calcite-surface ion-exchange behavior, not the injected-brine composition. At high ionic strength, the electrical double layer collapses and is no longer diffuse. All surface charges are located directly in the inner and outer Helmholtz planes. Our evaluation of calcite bulk and surface equilibria draws several important inferences about the proposed LSW oil-recovery mechanisms. Diffuse double-layer expansion (DLE) is impossible for brine ionic strength greater than 0.1 molar. Because of rapid rock/brine equilibration, the dissolution mechanism for releasing adhered oil is eliminated. Also, fines mobilization and concomitant oil release cannot occur because there are few loose fines and clays in a majority of carbonates. LSW cannot be a low-interfacial-tension alkaline flood because carbonate dissolution exhausts all injected base near the wellbore and lowers pH to that set by the rock and by formation CO2. In spite of diffuse double-layer collapse in carbonate reservoirs, surface ion-exchange oil release remains feasible, but unproved.

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