Delineating the Relationship between Nanoparticle Attachment Efficiency and Fluid Flow Velocity

Abstract

The ability to fundamentally describe nanoparticle (NP) transport in the subsurface underpins environmental risk assessment and successful material applications, including advanced remediation and sensing technologies. Despite considerable progress, our understanding of NP deposition behavior remains incomplete as there are conflicting reports regarding the effect of fluid flow velocity on attachment efficiency. To directly address this and more accurately describe NP attachment behavior, we have developed a novel protocol using a quartz crystal microbalance with dissipation monitoring (QCM-D) to separate and individually observe deposition mechanisms (diffusion and sedimentation), providing in situ, real-time information about particle diffusion (from the bulk liquid to solid surface). Through this technique, we have verified that the approaching velocity of NPs via diffusion increases (0.8–6.7 μm/s) with increasing flow velocity (6.1–106.0 μm/s), leading to an increased NP kinetic energy, thus affecting deposition processes. Further, in the presence of a secondary energy minimum associated with organic surface coatings, secondary minimum deposition decreases and primary minimum deposition increases with the flow velocity. NPs deposited at the primary minimum are relatively more resistant to hydrodynamic energies (including detachment associated energies), resulting in an increase of observed attachment efficiencies. Taken together, this work not only describes a novel method to delineate and quantify physical processes underpinning particle behavior but also provides direct measurements regarding key factors defining the relationship(s) of flow velocity and particle attachment. Such insight is valuable for next-generation fate and transport model accuracy, especially under unfavorable attachment regimes, which is a current and critical need for subsurface material applications and implication paradigms.

Important Role of Concave Surfaces in Deposition of Colloids under Favorable Conditions as Revealed by Microscale Visualization

“…The microparticles are hydrophilic and positively charged. The density of the microparticles is 1.055 g/cm 3 according to the manufacturer. The stock colloid suspensions were diluted in NaCl solutions at different solution ISs (1, 10, 100, and 200 mM) to prepare influent suspensions with a concentration of 10 mg/L for column transport experiments.…”

“…The porosities (f) of all packed sand and glass bead beds were consistently maintained to be 0.41 and 0.36, respectively. The porosities of the packed beds were calculated using the expression f = 1 − m/ρV, where ρ is collector density (2.65 and 2.5 g/cm 3 for sand and glass beads, respectively), m is dry mass of a packed bed, and V is column volume.…”

“…Investigation of transport of colloids including nanoparticles in porous media has received much attention for several decades due to a variety of environmental concerns. − For example, microplastic particles have been found to be widely present in subsurface environments such as soil porous media. , The potential risks of microplastics and microplastic-associated pollutants to groundwater are highly related to their fate and transport behavior in soil. In addition, nanomaterials such as nanoscale zerovalent iron (nZVI) have been shown to have the advantage for wastewater treatment due to their high efficiency for contaminant removal. − Understanding the transport of nZVI in soil is important for extending the application of nZVI to in situ soil remediation because the efficiency of remediation highly depends on the mobility of the nanomaterials to the contaminant sites. , …”

Ultrasmall Luminescent Metal Nanoparticles: Surface Engineering Strategies for Biological Targeting and Imaging

“…With the sharp shrinking size from PMNPs to ULMNPs, the contributions from the surface increase significantly, [ 52 ] which brings both opportunities and challenges for surface engineering. [ 53–56 ] Specifically, ULMNPs with the advantages of ultrasmall size scale provide distinctive building blocks for self‐assembly into uniform nanostructures with controllable size and shape, [ 57–59 ] rendering new properties and functions for advanced biological applications ranging from multimodal imaging to nanomedicine. A slight change in the surface chemistry (e.g., surface coverage, charge, and hydrophobicity) of ULMNPs can significantly affect their optical properties (e.g., absorption and emission) and biological behaviors (e.g., cellular interaction, organ distribution and excretion pathways), [ 60–64 ] which indicates great opportunities in the application‐driven surface engineering of ULMNPs for advanced biological applications.…”

Quartz Crystal Microbalance with Dissipation: A New Approach of Examining Corrosion of New Copper Surfaces in Drinking Water

“…Quartz (SiO 2 ) crystal microbalance with dissipation (QCMD) monitoring can continuously capture the in situ nanoscale changes resulting from interfacial interactions and chemical reactions over surfaces via monitoring the change of resonating frequency and energy dissipation of a piezoelectric quartz crystal disk with a reasonable time resolution (usually within a few hours). − The QCMD has been widely applied in diverse fields, and some of the specific areas include studying cell adhesion and spreading, , membrane permeability, nanoparticle deposition mechanisms under different flowing conditions, detergent efficiency, and biological materials and bioengineered surfaces. , However, QCMD studies on Cu corrosion in drinking water chemistry are still lacking. Choi first used QCMD to examine the etching or dissolution rate of Cu exposed to deionized water at pH 2.0–10.0, which does not represent the typical drinking water chemistry .…”