Polystyrene Water Research Articles

Investigation of the photolysis process of benzo(a)anthracene (BaA) on polyvinyl chloride (PVC) and polystyrene (PS) microplastics: Plastics aging effect, transformation products and toxicity assessment

Microplastics (MPs) and persistent pollutants (POPs) are new pollutants that are extensively studied worldwide. To fill the gaps that the degradation processes and mechanisms of polycyclic aromatic hydrocarbons (PAHs) on the surface of most MPs are still unclear, the photochemical transformation of benzo(a)anthracene (BaA) on polyvinyl chloride (PVC) MPs and polystyrene (PS) MPs in water were investigated and compared. The photolysis of BaA on the surface of PS in water proceeded easier than that on PVC within the 48 h irradiation period, with the pseudo-first-order rate constant of 0.0489 min−1 and 0.0181 min−1, respectively, which can be ascribed to the smaller particle size and more OH production of PS MPs. Due to the light competition between the chromophore and BaA as well as the light-shielding effect, aged MPs showed an inhibitory effect on the degradation of BaA compared with pristine MPs. For BaA/PVC MPs system, the degradation of BaA in real water was not significantly affected by coexisting ions and humic acid (HA) (p < 0.05), while slight inhibitory effect on the degradation of BaA appeared for PS MPs in different water matrices (UP: 86.97 %, YR: 84.47 %, PR: 81.42 % and HR: 83.21 %). According to the electron paramagnetic resonance (EPR) test, quenching experiment and probe experiment, the relative contribution of direct photolysis (PVC: 82.02 %; PS: 69.54 %) and indirect photolysis (PVC: 17.98 %; PS: 30.46 %) was confirmed. A total of 14 products were identified, and the product types were not affected by plastics aging. The results of the toxicity assessment indicated that although some intermediate products remained toxic to aquatic organisms, the toxicity of most products was lower than that of BaA. This study provides new insights into the environmental fate of PAHs and the role of MPs in the photolysis process of contaminants in surface water.

Assessing the photodegradation potential of compounds derived from the photoinduced weathering of polystyrene in water

Benzoate (Bz−) and acetophenone (AcPh) are aromatic compounds known to be produced by sunlight irradiation of polystyrene aqueous suspensions. Here we show that these molecules could react with •OH (Bz−) and •OH + CO3•- (AcPh) in sunlit natural waters, while other photochemical processes (direct photolysis and reaction with singlet oxygen, or with the excited triplet states of chromophoric dissolved organic matter) are unlikely to be important. Steady-state irradiation experiments were carried out using lamps, and the time evolution of the two substrates was monitored by liquid chromatography. Photodegradation kinetics in environmental waters were assessed by a photochemical model (APEX: Aqueous Photochemistry of Environmentally-occurring Xenobiotics). In the case of AcPh, a competitive process to aqueous-phase photodegradation would be volatilisation followed by reaction with gas-phase •OH. As far as Bz− is concerned, elevated dissolved organic carbon (DOC) levels could be important in protecting this compound from aqueous-phase photodegradation. Limited reactivity of the studied compounds with the dibromide radical (Br2•-, studied by laser flash photolysis) suggests that •OH scavenging by bromide, which yields Br2•-, would be poorly offset by Br2•--induced degradation. Therefore, photodegradation kinetics of Bz− and AcPh should be slower in seawater (containing [Br−] ~ 1 mM) compared to freshwaters. The present findings suggest that photochemistry would play an important role in both formation and degradation of water-soluble organic compounds produced by weathering of plastic particles.

Degradation and fragmentation behavior of polypropylene and polystyrene in water

The polystyrene (PS) retrieved from the beach exhibited no change in surface texture. In contrast to it, the retrieved polypropylene (PP) had a rumpled surface texture. Highly reactive sulfate radical generated by K2S2O8 was employed as degradation initiator of PP and PS, and their degradation behavior was studied in water. The PS carbonyl index value gradually went up down, and its molecular weight (MW) curve discontinuously shifted to a lower MW with the increase of the degradation time unlike the PP. It was found that the PP microplastic production rate was approximately three time higher than the PS from weight ratio dependence on degradation time. The higher microplastic production rate of PP arose from its crystallizability. The voids were produced by change in specific volume occurring by chemi-crystallization and then provoked the cracks leading to quick fragmentation. The SEM photographs suggested that the PP microplastic size facilely reached nm order by the cracking around lamella.

Elasticity of single flexible polymer chains in good and poor solvents

Force versus extension curves measure entropic elasticity of single polymer chain in force spectroscopy experiments. A Worm-like Chain model is used to describe force extension experiments with an intrinsic chain parameter called persistence length, which is a measure of local bending flexibility. For flexible polymers, there is a discrepancy in estimates of persistence length in various force regimes. For instance, Atomic Force Microscopy (AFM) based pulling experiments report anomaly low values which are also inconsistent with magnetic tweezers experiments. To understand this, we investigate the role of coupling between microscopic force probe and intrinsic elasticity of polyethylene glycol chain in AFM-based experiments. We perform experiments using oscillatory rheology by providing an external excitation of fixed frequency to the probe. We show that a proper quantification of elastic response measured directly by oscillatory technique deviates significantly from conventional force-extension curves. The persistence length obtained by fitting WLC to stiffness extension data matches well with equilibrium tweezers experiments. In addition, for polystyrene chain in poor solvent no deviation in elastic response is observed between oscillatory and constant velocity pulling experiments. However, such deviation is seen for polystyrene in good solvent. We attribute this to hydrophobic interaction between monomers of polystyrene in water. Our results suggest that oscillatory rheology on single polymer chains provide quantitative estimate of its elastic response. The consistency in values of persistence length using magnetic tweezers experiments in low force regime and the AFM experiments in high force regime suggests that WLC is successful in describing the polymer elasticity in the force range typically probed in AFM experiments.

Off-line analytical pyrolysis GC–MS to study the accumulation of polystyrene microparticles in exposed mussels

An analytical procedure based on off-line analytical pyrolysis was utilized to study the bioaccumulation of polystyrene microspheres with different size (3 μm and 45 μm) by gills and digestive glands of Mytilus galloprovincialis exposed for 4 days at different concentrations of the polymer (3 μm: 0.015–1.5 μg L−1; 45 μm: 5−500 μg L−1). The mussel tissues were treated with 10 % KOH at 90 °C with good digestion efficiency (97 ± 1 %) and extracted with toluene. After evaporation the residue was pyrolysed at 500 °C with a resistively heated platinum filament. Pyrolysis products were trapped onto a charcoal cartridge, eluted with toluene and analysed by GC–MS under selected ion monitoring. Polystyrene concentrations were determined by the internal standard method from the peak areas of styrene. The procedure provided information on the effect of particle size, exposure level and tissue type on the bioaccumulation of polystyrene particles in terms of mass concentrations. Accumulation was observed in digestive glands, not in gills. The accumulation of larger particles in digestive glands increased with increasing concentrations of polystyrene in water and peaked at 14 ± 4 μg g−1. The reduction of lysosome membrane stability was observed for both particles size at a water concentration of 10,000 particles per litre, that corresponded to a lower mass concentration for the smaller particles. This study confirmed the capability of analytical pyrolysis to provide microplastic concentrations in terms of mass concentration in complex matrices.

Effects of polymer aging on sorption of 2,2′,4,4′-tetrabromodiphenyl ether by polystyrene microplastics

The sorption behavior of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) on aged polystyrene (PS) microplastics via seawater soaking, ultraviolet (UV) irradiation, seawater soaking and UV irradiation together was investigated. The effects of environmental factors including salinity, pH, and dissolved organic matter (DOM) on sorption of BDE-47 by the aged PS microplastics were analyzed. The equilibrium sorption capacity of BDE-47 by virgin PS, aged PS with seawater soaking, aged PS with UV irradiation and aged PS with seawater soaking and UV irradiation was 6.16, 4.96, 3.53, and 3.75 ng/g, respectively. The decrease in sorption capacity was related to the increase of surface crystallinity and the appearance of surface oxygen-containing functional groups. The kinetic and isotherm models suggested that aging did not change the sorption mechanism of BDE-47 on PS microplastics. pH had negligible impacts on BDE-47 sorption by virgin and aged PS. Sorption capacity of BDE-47 on aged PS in water with high salinity was lower than that on virgin PS, and DOM has less effect on the sorption of BDE-47 on aged PS.

Analytical approximation to the complex refractive index of nanofluids with extended applicability.

Currently, there are available a few simple analytical approximations to the complex effective refractive index that may be used for nanofluids. Namely, the Maxwell Garnett mixing formula with scattering corrections, the Maxell Garnett Mie approximation, the Foldy-Lax approximation and the small particle limit of the quasi-crystalline approximation. These approximations are valid either for very small nanoparticles (below a few nanometers in radius) or for very dilute nanofluids (below about 1% in particles' volume fractions) and therefore, do not cover the whole domain of particle suspensions referred to as nanofluids. Here we propose a new simple analytical approximation based on local field corrections to the Foldy-Lax approximation. The new mixing formula coincides with the mentioned approximations when they are expected to be valid and provides physically sound predictions when the mentioned approximations are no longer valid, within the realm of nanofluids. We compare predictions of the analytical approximations considered in this work with experimental data published earlier for nanofluids of polystyrene in water.

Sorption of non-ionic organic compounds by polystyrene in water

Polystyrene (PS) is a plastic material that is well known for its use in many different applications, e.g. as shock sensitive packaging. With its prevalence across society, PS contributes significantly to the overall plastic load in aqueous systems. Sorption of organic compounds by the plastics, especially micrometer-sized particles, in the environment has become a concern in the past years. The aim of this study was to improve the understanding of sorption properties of PS, one of the major plastic pollutants in the aqueous environment. Batch experiments with PS film (29 μm thickness) were performed for 4 days using a diverse set of 24 sorbates to account for varying molecular properties like polarity or molecular volume. Isotherms were evaluated using different sorption models to elucidate the sorption process of PS. Sorption to PS film was non-linear and absorption into the bulk material was the dominant sorption mode. A clear discrimination between the specific and non-specific interactions in the aqueous environment could be shown. The non-linear sorption to PS was shown to be controlled by the molar volume but also by the polarizability/dipolarity parameter (S) of the ppLFER model. The latter is influenced by the aromatic π-π-interactions of PS with the sorbate. Similar to other plastics like polyethylene, sorption to PS is driven by hydrophobic interactions but phase descriptors of pristine PS were significantly different than descriptors for other environmental relevant plastics.

Characterisation of the hydrophobic collapse of polystyrene in water using free energy techniques

We characterise the hydrophobic collapse of single polystyrene chains in water using molecular dynamics simulations. Specifically, we calculate the potential of mean force for the collapse of a single polystyrene chain in water using metadynamics, comparing the results between all atomistic with coarse-grained (CG) molecular simulation. We next explore the scaling behaviour of the collapsed globular shape at the minimum energy configuration, characterised by the radius of gyration, as a function of chain length. The exponent is close to one third, consistent with that predicted for a polymer chain in bad solvent. We also explore the scaling behaviour of the solvent accessible surface area (SASA) as a function of chain length, finding a similar exponent for both all atomistic and CG simulations. Furthermore, calculation of the local water density as a function of chain length near the minimum energy configuration suggests that intermediate chain lengths are more likely to form dewetted states, as compared to shorter or longer chain lengths.

THE DETERMINATION OF COMPLEX SHEAR MODULUS OF DEIONIZED WATER USING KRAMER-KRONIG RELATION (KKR) METHOD

Complex Shear Modulus (CSM) contains fruitful information about mechanical properties,especially in microrheologystudies. CSM calculation depends onComplex Response Function (CRF) of an object motion. The aim of this paper is to provide guidance on the determination of the CSM by using Kramer-Kronig Relation (KKR) method. The procedure takes advantage of Brownian Motion (BM) of a micron-sized polystyrene in water. The BM occurs when the particle were responseto the thermal force in fluids medium. We use Laplace Transform(LT) algorithm to analyze the BMand to find CRF and CSM.The result will be displayedas Radial Frequencies Function.

Surface Effects on Photoluminescence and Optical Nonlinearity of CdS Quantum Dots Stabilized by Sulfonated Polystyrene in Water

A simple aqueous method has been used for the direct synthesis of water-soluble sulfonated polystyrene (SPS) encapsulated CdS quantum dots (QDs). The aqueous solution of the QDs, stabilized by two SPSs of different sulfonation level, shows a blue shift in ultraviolet–visible (UV–vis) absorption and band edge emission. High resolution transmission electron microscope (HR-TEM) establishes the presence of quantum confined CdS particles. The sulfonation level of SPS influences the size of QDs and strongly affects the photoluminescence (PL). The CdS QDs passivated by SPS with less sulfonation level exhibit only band edge emission (463 nm), while QDs in aqueous solution of SPS with high sulfonic acid content emits predominantly defect state emission (610 nm) against the band edge emission (463 nm). The PL of the SPS-CdS nanocomposites demonstrates an interesting variation in emission spectra and quantum yield via the change in sulfonation level, the change in pH and on keeping in aqueous solution. In addition, the z-scan measurements show negative nonlinear refraction coefficient, indicating self-defocusing phenomena. The absolute value of the third order nonlinear refractive index and nonlinear absorption are decided by the CdS QDs surface chemistry.

The Manipulation and Combustion of Carbon-Based Micro Particles by Optical Tweezers

This article presents the manipulation and combustion of carbon-based micro particles (polystyrene, active carbon) by optical tweezers. Trap, ignition, and combustion of micro particles are well demonstrated. For polystyrene in water, polystyrene micro particles of 2.9 µm are trapped with increasing laser power. The polystyrene takes reaction and combusts as the laser power of 520 mW. For active carbon in air, both single active carbon and active carbon bundle can be trapped, dragged, oxidized, ignited, and combusted. The drag speed and burning rate of single active carbon of 7.0 µm are 103.7 µm/s and 14.0 µm/s as the minimum ignition power of 3.2 mW. Combustions of single active carbon and bundle are flameless at minimum ignition power. As the power is further enhanced, strenuous oxidation and combustion flame can be observed. For active carbon bundle of 215.7 µm, combustion process sustains 0.72 s as the laser power of 90 mW.

Synthesis of Nano‐structured Poly(2,6‐dimethyl‐1,4‐phenylene‐oxide)/Polystyrene in Water

AbstractFor the first time, poly(2,6‐dimethyl‐1,4‐phenylene‐oxide)/polystyrene (PPO/PS) nanocomposite particles have been successfully synthesized using fusion of recently developed green technologies, the oxidative polymerization in water. The emulsion polymerization of styrene and oxidative polymerization of DMP using water as a solvent in one pot was found to produce nano sized PPO/PS nanocomposite particles with higher thermal stability property than that of PPO polymer as well as PS nanoparticles.

Novel thermophoretic particle separators: Numerical analysis and simulation

In this paper, it is shown that thermophoresis is a viable method for precise particle separation (sieving) and manipulation in microchannels. To do so, thermophoresis force acting on particles suspended in air and water flowing in a microchannel heated from below are simulated and relative magnitude and difference of thermophoresis force acting on a particle in a gas and liquid is discussed, discerned and elucidated. To show the potential of thermophoresis to serve as a sieve, transport equations for suspension of polystyrene in water and gold particles in air are solved numerically, both in the absence and presence of gravity. In simulations, particles are considered as a discrete phase and their trajectories are tracked using a Lagrangian approach. It is shown that thermophoresis can be used to separate macromolecules and particles from a water stream in a microchannel with one inlet and two outlets. Also, it is demonstrated that thermophoresis can be used as a means to separate multiple particle streams with different characteristics such as size and density from a gas flowing in a microchannel. Two microchannel geometries were numerically analyzed and it is shown that in both cases particles with different sizes are forced to exit through a different outlets. This effect can be used to separate, concentrate, manipulate, trap, target and transfer macromolecules such as bio-molecules and DNA in a microchannel. The correct application of thermophoresis theory in a gas and liquid is elucidated throughout the simulations.

Pearl-Necklace-Like Chain Conformation of Hydrophobic Polyelectrolyte: a SANS Study of Partially Sulfonated Polystyrene in Water

The form factor of partially sulfonated polystyrene PSSNa (degree of sulfonation f =1, 0.72, 0.64 and 0.36), at polymer concentration 0.17M and 0.34M, without or with added salt (0 M, 0.34M, & 0.68M), is measured by Small Angle Neutron Scattering using the Zero Average Contrast method. The total scattering function is also measured, allowing extracting the distinct interchain function and an apparent structure factor. The main result is the behavior of the form factor which shows contributions of spherical entities as well as extended chain parts. This is striking for 0.64, while for f = 0.36 the sphere contribution is more dominant. The conformation does not depend on polymer concentration. When salt is added, the sphere sizes do not vary, but the contribution attributed to the stretched parts does vary very much like for fully sulfonated PSSNa. Discussion of the interchain contribution establishes that chains are interpenetrated for f= 0.64, and at the overlap limit for f=0.36. The pearl necklace model appears very suitable. Comparisons are made with analytical calculation and simulation data. While the roles of Rayleigh transition, heterogeneous architecture, and strong hydrophobicity of non sulfonated PS monomers remain to discuss, data give an accurate 3 d image of the pearl necklace.

Liquid chromatography and differential scanning calorimetry studies on the states of water in polystyrene–divinylbenzene copolymer gels

The thermal phase transition behavior of water incorporated in crosslinked polystyrene–divinylbenzene copolymer (PS–DVB) gel packings for liquid chromatography was investigated by differential scanning calorimetry. Free or bulk water, freezable bound or intermediate water, and nonfreezing water were observed for TSKgel Styrene-250 samples, while only free water and nonfreezing water were observed for TSKgel Styrene-60 samples. Freezable bound water and nonfreezing water in these gel samples were considered to be water confined in pores of the polymer gels. A liquid chromatographic method for determination of the amounts of stationary phase water was applied to the characterization of water in the PS–DVB beads in the columns and it was found out that any water in the PS–DVB gels did not function as the stationary phase contrary to the water sorbed in hydrophilic polymer gels; not only freezable bound water but also nonfreezing water in hydrophobic PS–DVB gels are similar to bulk water with respect to the affinity to the solute compounds.

Microgravity laser-photophoresis of high density microparticles in water

Abstract Laser-photophoresis is a new technique, which can be used to characterize and separate microparticles in liquids. The photophoretic migration of high density solid particles in water has been observed experimentally for the first time by experiments under microgravity conditions. The photophoretic velocity was measured under microgravity conditions, in order to minimize the effects of density difference and convection. Furthermore, by using an optical cylindrical cell, we could observe the precise photophoretic velocities without the wall-induced drag effect. The apparatus consisted of a cw Nd:YAG laser (532 nm), a microscope, a CCD system, and a remote controlled sample stage and was set in a capsule which was used for a free-fall experiment. All the experimental operations were made externally by using a personal computer. The photophoretic velocities for the particles of carbon, stainless steel, gold plated nickel, and polystyrene in water were determined under microgravity. It was found that the photophoretic efficiencies of the photo-absorbing carbon particles and the photo-reflecting metal particles were much larger than those of transparent particles. The order of magnitude of the observed photophoretic efficiency was carbon>stainless steel>gold plated nickel>polystyrene. The photophoretic efficiencies were compared with those calculated by a Mie scattering theory. It was proved that the Mie scattering theory was useful for the prediction of the photophoretic efficiency of various kinds of particles in water.

Characterization of concentrated colloidal suspensions using time-dependent photon migration measurements

A method is presented to characterize concentrated suspensions of particles using frequency-domain photon migration in order to demonstrate its potential for on-line monitoring in the pharmaceutical and chemical based industries. In this study, the isotropic scattering coefficient was determined from FDPM measurements conducted at wavelengths between 448 and 835 nm using surfactant stabilized polystyrene latices of 195–335 nm mean diameter, 7–19% polydispersity and concentrations between 1 and 40% by volume. Upon using the Percus–Yevick model for static structure of monodisperse spheres to account for hindered scattering in the inverse solution, determination of the volume fraction and mean particle diameter were considerably improved size at solids volume fractions of 10% or greater. Owing to (i) the relative refractive index of polystyrene in water, (ii) the inaccuracy of the first order particle interaction model for suspensions with polydispersity >8%, and (iii) the minimal number of wavelengths used, it was difficult to recover the variance of the unimodal particle size distributions. Nonetheless, this work demonstrates the use of time-dependent measurements of multiply scattered light to characterize suspensions with solids volume fractions greater than 10%.

Synthesis of Alumina Balloons Using a Microcapsulation Method

The synthesis of alumina balloons using the microcapsulation method has been investigated, and was successful in producing a transparent balloon with a diameter of 50-80μm and a wall thickness of less than 1μm. The process is as follows. 10mass% solution of polystyrene in toluene and boehmite sots of approximately 1mol/kg concentration are mixed by a homogenizer. The resultant W/O emulsion is redispersed in water to obtain a (W/O) W emulsion which produces boehmite sols encapsulated by polystyrene in water. After keeping it for 2 days at 40°C, the products are filtered, dried and then the polystyrene crust is dissolved by toluene. The resultant balloon precursors of boehmite sols are dried, fired and then the alumina balloons are obtained. In this paper, the effects of the concentration of polystyrene or boehmite sots and the addition of ethylene glycol or tricresyl phosphate on the formation of alumina balloons were discussed in detail.

Polyelectrolyte conductivity

Using the de Gennes scaling model for the configuration of a polyelectrolyte chain in semidilute solution, we construct a simple model of AC conductivity for semidilute solutions of strongly charged polyelectrolytes without added salt. We compare the predictions of this model with literature data and new data on two polyelectrolytes with very different affinities for water. The sodium salt of sulfonated polystyrene in water is a hydrophobic polyelectrolyte (the uncharged monomer does not dissolve in water), where the chain is locally collapsed. The sodium salt of poly(2-acrylamido-2-methylpropanesulfonate), is a much more hydrophilic polyelectrolyte, making the chain quite expanded locally. The model describes the conductivity of both cases reasonably for concentrations below 10−2 M (mol of monomer per liter). Deviations between experiment and theory at higher concentrations lead us to conclude that counterion condensation decreases as concentration is increased. This is qualitatively consistent with the experimental observation that the dielectric constant of the polyelectrolyte solution increases as polyelectrolyte is added. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2951–2960, 1997