Dicarboxylic Polyethylene Glycol Research Articles

Degradation of polyethylene glycols and polypropylene glycols in microcosms simulating a spill of produced water in shallow groundwater.

Polyethylene glycols (PEGs) and polypropylene glycols (PPGs) are frequently used in hydraulic fracturing fluids and have been detected in water returning to the surface from hydraulically fractured oil and gas wells in multiple basins. We identified degradation pathways and kinetics for PEGs and PPGs under conditions simulating a spill of produced water to shallow groundwater. Sediment-groundwater microcosm experiments were conducted using four produced water samples from two Denver-Julesburg Basin wells at early and late production. High-resolution mass spectrometry was used to identify the formation of mono- and di-carboxylated PEGs and mono-carboxylated PPGs, which are products of PEG and PPG biodegradation, respectively. Under oxic conditions, first-order half-lives were more rapid for PEGs (<0.4-1.1 d) compared to PPGs (2.5-14 d). PEG and PPG degradation corresponded to increased relative abundance of primary alcohol dehydrogenase genes predicted from metagenome analysis of the 16S rRNA gene. Further degradation was not observed under anoxic conditions. Our results provide insight into the differences between the degradation rates and pathways of PEGs and PPGs, which may be utilized to better characterize shallow groundwater contamination following a release of produced water.

Production of mono- and di-carboxylated polyethylene glycols as a factor obstacle to the successful ozonation-assisted biodegradation of ethoxylated compounds

Ozonation is believed to improve the biodegradability of organic compounds. In the present study, degradation of nonylphenol ethoxylates (NPEOs) was monitored in hybrid treatment systems consisting of ozonation and microbial degradation processes. We found that ozonation of NPEOs decreased, rather than increased, the biodegradability under certain conditions. The timing of ozonation was a definitive factor in determining whether ozonation increased or decreased the biodegradation rates of NPEOs. Initial ozonation of NPEOs prior to biodegradation reduced the rate of dissolved organic carbon (DOC) removal during the subsequent 14d of biodegradation, whereas intermediate ozonation at the 9th day of biodegradation improved subsequent DOC removal during 14d of NPEO biodegradation. Furthermore, reduction of DOC removal was also observed, when initial ozonation prior to biodegradation was subjected to cetyl alcohol ethoxylates. The production of less biodegradable intermediates, such as mono- and dicarboxylated polyethylene glycols (MCPEGs and DCPEGs), was responsible for the negative effect of ozonation on biodegradability of NPEOs. DCPEGs and MCPEGs were produced by biodegradation of polyethylene glycols (PEGs) that were ozonolysis products of the NPEOs, and the biodegradability of DCPEGs and MCPEGs was less than that of the precursor PEGs. The results indicate that, if the target chemicals contain ethoxy chains, production of PEGs may be one of the important factors when ozonation is considered.

Degradation of the nonionic surfactant Triton™ X-45 with HO[rad] and [formula omitted] – Based advanced oxidation processes

In the present study the nonionic surfactant Triton™ X-45 (TX-45), an octylphenol polyethoxylate, was treated by persulfate (S2O82-)/UV-C process involving the intermediacy of sulfate radicals and the relatively well-known hydrogen peroxide (H2O2)/UV-C process. TX-45 removal occurred rapidly via both advanced oxidation processes. Complete oxidation was also achieved under the studied reaction conditions, however required extended treatment periods (>30min) and high oxidant concentrations (⩾2.5mM). Several degradation products could be qualified via GC–MS and HPLC analyses. Inspection of the identified degradation products indicated that the reaction mechanism of TX-45 was a combination of various pathways; (i) progressive shortening of the exhoxylate chain leading to relatively short-chain TX-45 and ultimately octylphenol, (ii) ω-carboxylation of the terminal alcoholic groups yielding octylphenol ethoxy carboxylates (OPECs) and (iii) central fission of the ethoxy chain resulting in the formation of polyethylene glycols (PEGs). Continued oxidation of the primary degradation products resulted in mono- and di-carboxylated PEGs. Degradation products bearing a smaller number of ethylene oxide units (⩽3) were generated during H2O2/UV-C treatment, whereas OPECs was only detected during S2O82-/UV-C treatment of TX-45. Acetic and succinic acids were quantitatively identified during S2O82-/UV-C treatment, whereas oxalic and fumaric acids were additionaly detected during H2O2/UV-C oxidation. Product identification suggested similar reaction pathways for the treatment of TX-45 by SO4-- and HO-driven oxidation processes.

Synthesis and characterization of stable dicarboxylic pegylated magnetite nanoparticles

The coating of implantable nano- or micro-objects with polyethylene glycol (PEG) enhances its biocompatibility and biodistribution. Herein, we describe a new protocol that enhances and maintains MNPs stability in biological media, simulating multiple conditions to which they would be subjected in the human body. Magnetite nanoparticles (MNPs) prepared via a facile way at room temperature by co-precipitation reaction, were coated with dicarboxylic polyethylene glycol (DCPEG) via covalent bonds. The surface of the nanoparticles was first coated with 3-aminopropyl trimethoxysilane by a silanization reaction and then linked with DCPEG of different molecular weight (Mw=5000, 10,000 and 20,000gmol−1). The uncoated magnetite nanoparticles, with an average size of 20nm, exhibited superparamagnetism, high saturation magnetization and a negative surface charge (with a zeta potential value of −40mV). Increase of Mw enhances the colloidal stability of MNPs and makes them more suitable to tolerate high salt concentrations (1MNaCl) and wide pH (from 5.5 to 12) and temperature ranges (24°C to 46°C). The results indicate that magnetite nanoparticles coated with DCPEG with Mw=20,000 have improved properties over their counterparts, making them our best choice for biomedical studies.

Formation of [M-H]- and [M-2H]2- ions in the electrospray ionization mass spectra of dicarboxylated polyethylene glycols.

The negative-ion electrospray mass spectrometric behavior of dicarboxylated polyethylene glycols (CPEGCs) is discussed. Both [M-H](-) and [M-2H](2-) ions were observed. It was found that the ratio [M-2H](2-)/[M-H](-) is affected by oxyethylene chain length, solvent polarity, analyte concentration and applied cone voltage.

Mass spectrometric behaviour of carboxylated polyethylene glycols and carboxylated octylphenol ethoxylates.

Mass spectrometric behaviour of mono- and di-carboxylated polyethylene glycols (PEGCs and CPEGCs) and carboxylated octylphenol ethoxylates (OPECs) are discussed. The tendency for ionisation (deprotonation, protonation and cationisation by alkali metal cations) of carboxylated PEGs was compared with that of non-carboxylated correspondents by using both secondary ion mass spectrometry (SIMS) and electrospray ionisation (ESI). The fragmentation of the PEGCs and CPEGCs is discussed and also compared with their neutral correspondents, PEGs. The B/E mass spectra were recorded, using secondary ion mass spectrometry as a method for generation, for deprotonated and protonated molecules and molecules cationised by alkali metal cations. The fragmentation behaviour of PEGs is found to be different from that of CPEGCs, The presence of carboxylic groups may be confirmed not only by the determination of molecular weights of the ethoxylates studied, but also on the basis of the fragment ions formed. The metastable decomposition of the [OPEC-H](-) ions proceed through the cleavage of the bond between the octylphenol moiety and the ethoxylene chain leading to the octylphenoxy anions. It permits determination of the mass of the hydrophobic moiety of the studied carboxylated alkylphenol ethoxylate. ESI mass spectra recorded in the negative ion mode were found to be more suitable for the determination of the average molecular weight of carboxylated ethoxylates than SI mass spectra.

The stability of non-ionic surfactants and linear alkylbenzene sulfonates in a water matrix and on solid-phase extraction cartridges.

The stability of nonylphenol ethoxylates (NPEO), alcohol ethoxylates (AEO), coconut diethanol amides (CDEA) and linear alkylbenzene sulfonates (LAS) in a water matrix and preconcentrated on SPE cartridges was studied. A stability study was carried out in a water matrix (spiked ground water and real-world waste water) comparing different pretreatment procedures (addition of sulfuric acid to pH = 3, preservation with 1% and 3% of formaldehyde). When stored in a water matrix serious qualitative and quantitative changes occurred in waste water during the period of time studied (30 days). The losses of C12-C14 alcohol ethoxylates ranged from 72% to 88% when the sample was preserved with acid and from 17% to 86% when the sample was preserved with formaldehyde (3%). Simultaneously, an enrichment of the shorter alkyl chain homologues (C7EO and C10EO) was observed. The losses of NPEO were from 45% (sample preserved by acidification or by addition of 3% of formaldehyde) to 85% (sample preserved with 1% of formaldehyde). Additionally, an increase in concentration of polyethylene glycols (PEGs) and formation of different acidic forms, such as monocarboxylated (MCPEGs) and dicarboxylated polyethylene glycols (DCPEGs) were observed. The stability of surfactants preconcentrated on SPE cartridges was studied as a function of storage time and storage conditions (room temperature, 4 degrees C and -20 degrees C). The results indicate that disposable SPE cartridges can be recommended for the stabilization of non-ionic surfactants and LAS. Storage at -20 degrees C is feasible for long periods (up to 3 months for ground water and up to 2 months for waste water), while storage at 4 C can be recommended for a maximum of 1 month. When cartridges were kept at -20 degrees C the losses of AEOs (n = 12, 13 and 14), preconcentrated from waste water, ranged from 17 to 29% (after 60 days) and other compounds suffered small losses (maximum of 14% for C13LAS). At room temperature, after 7 days, the losses were less than 11%, indicating that shipping of samples by mail can be done without any special requirements.