Aqueous Particles Research Articles

Evaporation of mixed citric acid/(NH4)2SO4/H2O particles: Volatility of organic aerosol by using optical tweezers.

The condensation and evaporation processes of semi-volatile organic compounds (SVOCs) in atmospheric aerosols can induce significant evolutions of their chemical and physical properties. Hence, for interpreting and predicting composition changes of atmospheric aerosols, it is indispensable to provide insight into the partitioning behaviors of SVOCs between condensed and gas phases. In this research, optical tweezers coupled with cavity-enhanced Raman spectroscopy were employed to observe the volatility of internally mixed citric acid (CA)/(NH4)2SO4 (AS) particles, and the effect of AS on the gas/particle partitioning behaviors of atmospheric organic acids was investigated. The radii and refractive indexes of the levitated droplets were determined in real time from the wavelength positions of simulated Raman spectra and the effective vapor pressures of CA at different relative humidities (RHs) were obtained according to Maxwell equation. For the CA/AS particle with organic to inorganic mole ratio (OIR) of 1:1, the effective vapor pressure of CA decreased with the decreasing of RH. When the RH decreased from 67% to 8.2%, the effective vapor pressure of CA decreased from (1.35±0.508)×10-4Pa to (3.0±1.0)×10-6Pa. Meanwhile, the CA/AS particles with OIR of 3:1, 1:3 were also studied, and the results show the same phenomenon compared to the particles with OIR of 1:1. When under constant RHs, the effective vapor pressures of CA decreased with the increasing of AS contents, suggesting that the presence of AS suppressed the partitioning of CA to aqueous particles. In addition, the mass transfer processes of water in CA and CA/AS/H2O systems were further studied. The characteristic time ratio between the droplet radius and RH was used to describe the water mass transfer difference dependent on RH. Compared to the characteristic time ratio of pure CA, the characteristic time ratio of CA/AS particles apparently increased. For CA/AS particles under the same RH steps, the characteristic time ratio increased with the AS content increase. According to the differential isotherm, the diffusion coefficients of citric acid and citric acid/ammonium sulfate at low RHs (RH ≈7%-1%, RH≈1%-7%) were calculated respectively. Generally, the key aspect of the current work was to deeply explore the relationship between the evaporation rates of SVOCs and water transport process.

Aqueous Carbon Quantum Dot-Embedded PC60-PC61BM Nanospheres for Ecological Fluorescent Printing: Contrasting Fluorescence Resonance Energy-Transfer Signals between Watermelon-like and Random Morphologies.

To go beyond the PC60 surfactant structure, the double-layer micelle morphology in water motivates exploration of altered protocols to produce new morphologies. Furthermore, the low photoluminescence quantum yield of aqueous fullerene-based particles encourages high fluorescence to create a light-emitting display. With this in mind, we established new hybrid n-type nanospheres with carbon quantum dot (CQD)-embedded PC60-PC61BM particles, processed using two different protocols. The homogenizer-assisted PC60-CQD-PC61BM resulted in a watermelon-shaped spherical particle, whereas a circular morphology with randomly embedded CQDs was observed in the microwave-treated hybrids. More surprisingly, the watermelon-shaped colloid induced efficient fluorescence resonance energy transfer (FRET) between the CQD and C60 molecules of PC61BM, and the FRET-mediated emission signature diminished gradually as the stripe patterns collapsed. This phenomenon allowed different fluorescent colors in the colloidal printing film. We thereby provided the new carrier dynamics of the particle photonic activities of the developed aqueous PC60-based colloids with the possibility of ecological utilization.

Production of Singlet Oxygen (1O2) during the Photochemistry of Aqueous Pyruvic Acid: The Effects of pH and Photon Flux under Steady-State O2(aq) Concentration

The photochemistry of pyruvic acid (PA) in aqueous atmospheric particles contributes to the production of secondary organic aerosols. This work investigates the fate of ketyl and acetyl radicals produced during the photolysis (λ ≥ 305 nm) of 5-100 mM PA under steady state [O2(aq)] = 260 μM (1.0 ≤ pH ≤ 4.5) for photon fluxes between 1 and 10 suns. The radicals diffuse quickly into the water/air interface of microbubbles and react with dissolved O2 to produce singlet oxygen (1O2*). Furfuryl alcohol is used to trap and bracket the steady-state production of 2 × 10-12 ≤ [1O2*] ≤ 1 × 10-11 M. Ion chromatography mass spectrometry shows that 2,3-dimethyltartaric acid (DMTA), 2-(3-oxobutan-2-yloxy)-2-hydroxypropanoic acid (oxo-C7 product), and 2-(1-carboxy-1-hydroxyethoxy)-2-methyl-3-oxobutanoic acid (oxo-C8 product) are formed under all conditions investigated. The sigmoidal dependence of initial reaction rates with pH resembles the dissociation curve of PA. For increasing photon fluxes, the branching ratio of products shifts away from the radical recombination that favors DMTA toward multistep radical chemistry forming more complex oxocarboxylic acids (oxo-C7 + oxo-C8). The large steady-state production of 1O2 indicates that PA in aerosols can be a significant source of atmospheric oxidants on par with natural organic matter.

Insights into the Rheological Behavior of Aqueous Dispersions of Synthetic Saponite: Effects of Saponite Composition and Sodium Polyacrylate

Synthetic saponite (Sap) easily delaminates in water to form a transparent sol and hydrogel with excellent rheological performance and is thus widely used in paints, cosmetics, and nanomaterials. The thixotropic property of Sap hydrogels is heavily dependent on the nature of Sap and the external electrolyte and polyelectrolyte; yet, details on the relationship between rheological behaviors of saponite hydrogels and Sap composition and polyelectrolyte remain unclear. In this work, thixotropic rheological behaviors of a series of synthetic Sap hydrogels, with and without added sodium polyacrylate polyelectrolyte (NaPA), were investigated. The Sap samples, with a Si/Al molar ratio from 5 to 25, were successfully synthesized using hydrothermal methods and characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The rheological performances of aqueous Sap dispersions and particle sizes and ζ-potentials of Sap were measured. The results showed that the crystallinity of the Sap increased with an increasing Si/Al molar ratio. All Sap samples, with the exception of the Sap with a Si/Al molar ratio of 5, dispersed well in water (3 wt %) to form hydrogels. The rheological behaviors of the hydrogels were related to the chemical composition and the layer charge of the Sap. The Sap with a Si/Al molar ratio of 25 had higher viscosity due to improved delamination. The addition of the NaPA, an anionic polyelectrolyte, into the hydrogels decreased the viscosity and altered the thixotropic properties such that the hydrogel becomes a sol. The addition of NaPA facilitated the dispersion and delamination of Sap, because under the electric field of negatively charged Sap particles in the hydrogel, the anionic NaPA was instantaneously polarized and thereby entered the hydration layer of the Sap particles.

Chamber-based insights into the factors controlling epoxydiol (IEPOX) secondary organic aerosol (SOA) yield, composition, and volatility

Abstract. We present measurements utilizing the Filter Inlet for Gases and Aerosols (FIGAERO) applied to chamber measurements of isoprene-derived epoxydiol (IEPOX) reactive uptake to aqueous acidic particles and associated secondary organic aerosol (SOA) formation. Similar to recent field observations with the same instrument, we detect two molecular components desorbing from the IEPOX SOA in high abundance: C5H12O4 and C5H10O3. The thermal desorption signal of the former, presumably 2-methyltetrols, exhibits two distinct maxima, suggesting it arises from at least two different SOA components with significantly different effective volatilities. Isothermal evaporation experiments illustrate that the most abundant component giving rise to C5H12O4 is semi-volatile, undergoing nearly complete evaporation within 1 h while the second, less volatile component remains unperturbed and even increases in abundance. We thus confirm, using controlled laboratory studies, recent analyses of ambient SOA measurements showing that IEPOX SOA is of very low volatility and commonly measured IEPOX SOA tracers such as C5H12O4 and C5H10O3, presumably 2-methyltetrols and C5-alkene triols or 3-MeTHF-3,4-diols, result predominantly from thermal decomposition in the FIGAERO-CIMS. We infer that other measurement techniques using thermal desorption or prolonged heating for analysis of SOA components may also lead to reported 2-methyltetrols and C5-alkene triols or 3-MeTHF-3,4-diol structures. We further show that IEPOX SOA volatility continues to evolve via acidity-enhanced accretion chemistry on the timescale of hours, potentially involving both 2-methyltetrols and organosulfates.

Production of dasatinib encapsulated spray-dried poly (lactic-co-glycolic acid) particles

Fibrotic scarring of the retina, termed proliferative vitreoretinopathy (PVR), can cause permanent visual impairment and blindness following corrective surgery for retinal detachment and/or ocular trauma. We have previously shown that multiple intravitreal injections of dasatinib prevent PVR in an animal model. The aim of this research was to develop injectable sustained release systems for dasatinib, which would be preferred for clinical use over multiple ocular injections. To accomplish this, dasatinib was encapsulated in Poly (lactic-co-glycolic acid) [PLGA] particles via a benchtop spray-drying process. Spray drying parameters were optimized using a taguchi statistical approach to obtain particle size between 0.5 and 1.5 μm. Characterization of two different sets of particles, sub-micron and >1.0 μm in average diameter, respectively, showed that dasatinib release from sub-micron particles lasts 15 days while release from particles with diameters >1.0 μm lasts up to 55 days. Zeta potential measurement of aqueous buffer suspended particles suggests sub-micron particles to be more stable in aqueous environment compared to >1.0 μm particles. Dasatinib released from these particles maintained therapeutic efficacy, as dasatinib incorporated PLGA particles significantly inhibited the contraction of collagen matrices compared to PLGA (control) particles when tested on an in vitro scar contraction assay.

Linear and Core-Crosslinked Glycopolymer-Gadolinium Conjugates: Preparation and Their Behaviors as Nanoscale Magnetic Resonance Imaging Contrast Agents.

In this study, a linear glycopolymer-gadolinium conjugate (pGAEMA-DOTA-Gd) was prepared via the reversible addition fragmentation chain transfer (RAFT) polymerization. In addition, a crosslinked polymer-gadolinium conjugate (Crosslinked pGAEMA-DOTA-Gd) was prepared via a two-step RAFT polymerization approach, and its core was composed of the biodegradable oligopeptide GFLG. The features of the two glycopolymer-gadolinium conjugates as highly efficient and safe nanoscale contrast agents were discussed. These two glycopolymer-DOTA-Gd conjugates have aqueous dynamic particle sizes of 4.8 nm and 21.3 nm with neutral charges. Longitudinal relaxivity (r1) of these two glycopolymer-gadolinium conjugates were three to four times higher than that of clinical agent DTPA-Gd. Animal studies showed that pGAEMA-DOTA-Gd and Crosslinked pGAEMA-DOTA-Gd demonstrated higher signal intensity and the relative change in T1 value (ΔT1) in mouse liver and kidney, and prolonged blood circulation time compared to DTPA-Gd. Notably, the performance of the core-crosslinked glycopolymer conjugate was better than that of the linear polymer. Inductively coupled plasma mass spectrometry (ICP-MS) results showed that polymeric contrast agents, especially the crosslinked one, showed higher aggregation in mouse liver and kidney, and were mainly excreted through renal routes eventually. In vitro and in vivo toxicity studies in healthy mice including cytotoxicity, blood compatibility and systemic toxicity indicated the absence of significant toxicity. Therefore, the prepared glycopolymer-DOTA-Gd conjugates may have significant potential as highly efficient and safe nanoscale MRI contrast agents.

Phase-Transfer and Stabilization of Highly Monodisperse Ferrite Nanoparticles into Polar Solvents by Ligand Exchange Synthesis.

Cobalt ferrite nanoparticles with controlled particle size are transferred from nonpolar into polar solvent by exchange of the as-synthesized oleic acid ligand shell with polyacrylic acid (PAA). The nanoparticles are highly monodisperse (σlog < 6%), and the ligand exchange synthesis has no measurable effect on particle size, shape, or size distribution. The stability of the aqueous particle dispersion without significant interparticle correlations as observed using small-angle X-ray scattering confirms the successful phase-transfer.

Occurrence, distribution, bioaccumulation, and ecological risk of bisphenol analogues, parabens and their metabolites in the Pearl River Estuary, South China

Bisphenol analogues and alkyl esters of p-hydroxybenzoic (parabens) can be defined as emerging endocrine-disrupting compounds (EDCs) due to their similar characteristics. This study analyzed eight bisphenol analogues, six parabens, and five paraben metabolites in seawater (including aqueous and suspended particle matter (SPM)), as well as organism samples from the Pearl River Estuary, in order to determine their occurrence, distribution, bioaccumulation, and ecological and human health risk in South China's marine environment. The aggregation concentrations of bisphenol analogues, parabens, and paraben metabolites were 106 ng/L, 4.53 ng/L, and 231 ng/L in aqueous samples, 868 ng/g, 173 ng/g, and 9320 ng/g in SPM samples, 41.6 ng/g, 6.46 ng/g, and 460 ng/g in marine organisms, respectively. This study identified significantly higher concentrations of paraben metabolites than their parent parabens in the marine environment, which has not yet been reported in previous studies. These findings call for greater attention on the contamination of paraben metabolites in marine environments. Moreover, the median values of the logarithm of bioaccumulation factors (BAF) for the detected 20 target compounds ranged from 0.11 to 5.07. Bisphenol analogues including bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), bisphenol B (BPB), bisphenol P (BPP), and Fluornen-9-bisphenol (BPFL) (3.3 < lg BAF < 3.7), and three paraben metabolites including 4-hydroxybenzoic acid (4-HB) (3.3 < lg BAF < 3.7), methyl protocatechuate (OH-MeP), and ethyl protocatechuate (OH-EtP) (Log BAF > 3.7), exhibited varying degrees of potential bioaccumulation effect in the majority of organism samples. Furthermore, all tested chemicals in this study were at low risk quotient (RQ) levels for acute and chronic toxicity in seawater. However, the target hazard quotient (THQ) values of two paraben metabolites, 4-HB and benzoic acid (BA), were higher than 1, which indicates that paraben metabolites have the potential to adsorb into organisms, and their associated human health risks should be of great concern. Overall, the study results suggest that the occurrence and risks of emerging EDCs in coastal waters are deserving of further studies, especially in densely populated regions of the world.

Rheological and electrical properties of polystyrene nanocomposites via incorporation of polymer-wrapped carbon nanotubes

Carbon nanotubes (CNTs) are used as nanofillers in polymer nanocomposites to improve the properties of a matrix polymer because of their excellent properties. However, CNTs tend to aggregate due to the strong van der Waals force between CNTs. To solve the problem, surface-modified CNTs with hydrophilic polymers, such as polyvinyl pyrrolidone (PVP) and polystyrene sulfonate (PSS), were employed. Polystyrene (PS)/CNT nanocomposites were fabricated by latex technology, which is a suitable method for dispersing nanofillers in aqueous particle suspension. The effect of the incorporation of the modified CNT was significant, thereby resulting in increased modulus at lower frequencies when compared to that of neat PS. Electrical percolation thresholds of PS/PSS-wrapped CNT and PS/PVP-wrapped CNT nanocomposites corresponded to 0.39 and 0.52 wt.%, respectively. The PS/PSS-CNT nanocomposites exhibited higher rheological and electrical properties than the PS/PVP-CNT counterparts due to the hydrophilic nature of PSS with strong negative charge groups.

Semibatch emulsion polymerisation modelling: polybutyl acrylate case study

ABSTRACTA comprehensive mathematical model is developed for emulsion polymerisation of butyl acrylate to polybutyl acrylate in a semi batch reactor. The mathematical framework is based on the population balance approach. The model includes such mechanistic details as: (i) particle generation from radicals entering micelles, (ii) coupling of the radical concentration in the aqueous phase and particle phase, (iii) determination of the particle phase radical concentration by radical entry into, exit from and termination inside the particle, (iv) thermodynamic equilibrium between the monomer concentration in the aqueous phase and the particle phase. The population balance equations are solved efficiently using orthogonal collocation. Dynamic simulations are compared to the experimental data taken from the literature. The predictions for the various average diameters of the particle size distribution, polydispersity index, standard deviation and full particle size distribution are also given.

To Be or Not To Be a Molecular Ion: The Role of the Solvent in Photoionization of Arginine.

Application of photoionization mass spectroscopy, a technique capable of assessing protonation states in complex molecules in the gas phase, is challenging for arginine due to its fragility. We report photoionization efficiencies in the valence region of aqueous aerosol particles produced from arginine solutions under various pH and vaporization conditions. By using ab initio calculations, we investigate the stability of different conformers. Our results show that neutral arginine fragments upon ionization in the gas phase but solvation stabilizes the molecular ion, resulting in different photoionization dynamics. We also report the valence-band photoelectron spectra of the aerosol solutions obtained at different pH values.

Optimization of Low-Carbon Footprint Quaternary and Quinary (37% Fly Ash) Cementitious Nanocomposites with Polycarboxylate or Aqueous Nanosilica Particles

The dispersion medium of nano-SiO2 (nS) particles can have a significant effect on the properties of nanoparticles themselves and consequently on the cement binders it will be added to. In this paper, nS particles dispersed in (a) polycarboxylate or (b) water were added to a low-carbon footprint reference binder containing 43% Portland cement (PC), 20% limestone powder (LS), and 37% fly ash (FA) by mass of binder. Eight quaternary binders containing nS, PC, LS, and FA and eight quinary binders comprising nS, PC, LS, FA, and silica fume (μS) were investigated. nS was added at 0.1%, 0.2%, 0.5%, or 1.0% by mass of binder as a replacement of LS for the quaternary binders and at 0.5% or 1.0% for the quinary binders. The nanoparticles were examined via transmission and X-ray scanning electron microscopy (TEM/SEM/EDX). For the pastes, compressive strength tests and thermal gravimetric analyses (TGAs) were performed at days 1, 7, 28, and 56, all testified to additional pozzolanic activity and additional C–S–H production. X-ray diffraction analyses and backscattered scanning electron imaging carried out on specific formulations also confirmed this finding at days 1, 28, and 56. Notwithstanding the additional pozzolanic reactivity, nS particles could not mitigate the delayed hydration of the reference paste in the early ages. In such complex formulations, the hydration products seem to create a wrapping around the FA particles delaying their activation at early ages. At later ages, the 0.5% nS addition provided strength, microstructural, and hydration improvements. The polycarboxylate/nS particles provided more pronounced strength improvements at 0.5% addition, possibly due to their superplasticizing effect. Lastly, a tabulated literature review on the thermal decomposition ranges of the hydration products of cementitious nanocomposites is also presented.

The Effects of Reactant Concentration and Air Flow Rate in the Consumption of Dissolved O₂ during the Photochemistry of Aqueous Pyruvic Acid.

The sunlight photochemistry of the organic chromophore pyruvic acid (PA) in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is highly sensitive to dissolved oxygen content, [O2(aq)], among other environmental conditions. Thus, herein we investigate the photolysis (λ ≥ 305 nm) of 10–200 mM PA at pH 1.0 in water covering the relevant range 0 ≤ [O2(aq)] ≤ 1.3 mM. The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is monitored in real time with a dissolved oxygen electrode. In addition, the rate of O2(aq) consumption is studied at air flow rates from 30.0 to 900.0 mL min−1. For the range of [PA]0 covered under air saturated conditions and 30 mL min−1 flow of air in this setup, the estimated half-lives of O2(aq) consumed by the photolytic radicals fall within the interval from 22 to 3 min. Therefore, the corresponding depths of penetration of O2(g) into water (x = 4.3 and 1.6 µm) are determined, suggesting that accumulation and small coarse mode aqueous particles should not be O2-depleted in the presence of sunlight photons impinging this kind of chromophore. These photochemical results are of major tropospheric relevance for understanding the formation and growth of secondary organic aerosol.

Indirect optical trapping using light driven micro-rotors for reconfigurable hydrodynamic manipulation

Optical tweezers are a highly versatile tool for exploration of the mesoscopic world, permitting non-contact manipulation of nanoscale objects. However, direct illumination with intense lasers restricts their use with live biological specimens, and limits the types of materials that can be trapped. Here we demonstrate an indirect optical trapping platform which circumvents these limitations by using hydrodynamic forces to exert nanoscale-precision control over aqueous particles, without directly illuminating them. Our concept is based on optically actuated micro-robotics: closed-loop control enables highly localised flow-fields to be sculpted by precisely piloting the motion of optically-trapped micro-rotors. We demonstrate 2D trapping of absorbing particles which cannot be directly optically trapped, stabilise the position and orientation of yeast cells, and demonstrate independent control over multiple objects simultaneously. Our work expands the capabilities of optical tweezers platforms, and represents a new paradigm for manipulation of aqueous mesoscopic systems.

Photoemission of Iodide from Aqueous Aerosol Particle Surfaces.

The photoemission of iodide from aqueous aerosol particle surfaces measures the surface concentration of iodide in predominantly supersaturated NaCl aerosol particles. Using the Langmuir model to describe the adsorption to the surface of aqueous iodide anions, the standard Gibbs free energy of adsorption is -15 kJ/mol in these systems. The presence of charged surfactants on the particle surfaces changes the adsorption behavior of iodide. The addition of sodium docecylsulfate (SDS) reduces the coverage of iodide, consistent with a competitive adsorption scenario. For surfaces coated with C12-, C14-, or C16-trimethylammonium chloride, the addition of iodide results in the formation of iodide-surfactant ion pairs at the surface with enhanced photoemission. The adsorption free energy for iodide in these systems is -21 kJ/mol. The results demonstrate the surface enhancement of iodide in supersaturated, atmospherically relevant conditions and demonstrate important differences between single-salt solutions and mixtures in the limit of high concentration.

Nanoparticle Emissions From Metal-Assisted Chemical Etching of Silicon Nanowires for Lithium Ion Batteries

As one of the most promising anode materials for high-capacity lithium ion batteries (LIBs), silicon nanowires (SiNWs) have been studied extensively. The metal-assisted chemical etching (MACE) is a low-cost and scalable method for SiNW synthesis. Nanoparticle emissions from the MACE process, however, are of grave concerns due to their hazardous effects on both occupational and public health. In this study, both airborne and aqueous nanoparticle emissions from the MACE process for SiNWs with three sizes of 90 nm, 120 nm, and 140 nm are experimentally investigated. The prepared SiNWs are used as anodes of LIB coin cells, and the experimental results reveal that the initial discharge and charge capacities of LIB electrodes are 3636 and 2721 mAh g−1 with 90 nm SiNWs, 3779 and 2712 mAh g−1 with 120 nm SiNWs, and 3611 and 2539 mAh g−1 with 140 nm SiNWs. It is found that for 1 kW h of LIB electrodes, the MACE process for 140 nm SiNWs produces a high concentration of airborne nanoparticle emissions of 2.48 × 109 particles/cm3; the process for 120 nm SiNWs produces a high mass concentration of aqueous particle emissions, with a value of 9.95 × 105 mg/L. The findings in this study can provide experimental data of nanoparticle emissions from the MACE process for SiNWs for LIB applications and can help the environmental impact assessment and life cycle assessment of the technology in the future.

A Comparison of the Microbial Community and Functional Genes Present in Free-Living and Soil Particle-Attached Bacteria from an Aerobic Bioslurry Reactor Treating High-Molecular-Weight PAHs

High-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) contaminate a wide range of ecosystems, including soils, groundwater, rivers and harbor sediments. The effective removal of HMW PAHs is a difficult challenge if a rapid remediation time and low economic cost are required. Bioremediation provides a cheap and eco-friendly cleanup strategy for the removal of HMW PAHs. Previous studies have focused on removal efficiency during PAHs bioremediation. In such studies, only limited research has targeted the bacterial communities and functional genes present in such bioremediation systems, specifically those of free-living (aqueous) bacteria and soil particle-attached bacteria present. In this study, a high-level of HMW PAH (1992 mg/kg pyrene) was bioremediated in an aerobic bioslurry reactor (ABR) for 42 days. The results showed a pseudo first order constant rate for pyrene biodegradation of 0.0696 day−1. The microbial communities forming free-living bacteria and soil-attached bacteria in the ABR were found to be different. An analysis of the aqueous samples identified free-living Mycobacterium spp., Pseudomonas putida, Rhodanobacter spp. and Burkholderia spp.; these organisms would seem to be involved in pyrene biodegradation. Various biointermediates, including phenanthrene, catechol, dibenzothiophene, 4,4′-bipyrimidine and cyclopentaphenanthrene, were identified and measured in the aqueous samples. When a similar approach was taken with the soil particle samples, most of the attached bacterial species did not seem to be involved in pyrene biodegradation. Furthermore, community level physiological profiling resulted in significantly different results for the aqueous and soil particle samples. Nevertheless, these two bacterial populations both showed positive signals for the presence of various dioxygenases, including PAHs-RHDα dioxygenases, riesk iron-sulfur motif dioxygenases and catechol 2,3-dioxygenases. The present findings provide a foundation that should help environmental engineers when designing future HMW PAH bioremediation systems that use the ABR approach.

Electric-field enhanced reactivity and migration of iron nanoparticles with implications for groundwater treatment technologies: Proof of concept

The extensive use of nanoscale zero-valent iron (nZVI) particles for groundwater treatment has been limited, in part, because of their non-selective reactivity and low mobility in aquatic environments. Herein, we describe and explore progressive changes in the reactivity and migration of aqueous dispersed nZVI particles under an applied DC electric field. Due to the applied electric field with an intensity of about 1 V cm−1, the solution oxidation-reduction potential (ORP) remained as low as −200 mV for at least 32 days, which was in agreement with the persistence of the reduced iron species (mainly Fe(II)), and led to substantially prolonged reactivity of the original nZVI. The treatment of chlorinated ethenes (DCE > PCE > TCE) was markedly faster, individual CHC compounds were eliminated with the same kinetics and no lesser-chlorinated intermediates were accumulated, following thus the direct dechlorination scheme. When nZVI-dispersion flows towards the anode through vertical laboratory columns filled with quartz sand, significant enhancement of nZVI migration was recorded because of lower extent of nanoparticle aggregation and increased repulsion forces between the nanoparticles and the surface of silica dioxide. The results of this study have significant consequences for groundwater remediation, mainly for the treatment of slowly degradable DCE in real CHC contaminated groundwater, where it could improve the reactivity, the longevity and the migration of nZVI particles.

Use of anchoring amphiphilic diblock copolymers for encapsulation of hydrophilic actives in polymeric microcapsules: methodology and encapsulation efficiency

Aqueous core-shell particles based on polystyrene, poly(methyl methacrylate) or polycaprolactone have been formulated using a facile double emulsion-based solvent evaporation method. The size distr ...