Factors affecting microplastic retention and emission by a wastewater treatment plant on the southern coast of Caspian Sea.

Understanding how wastewater treatment plants (WWTPs) process microplastics (MPs) will help informing management practices to reduce MP emissions to the environment. We show that composite 24 h samples taken at three replications from the outflow of the grit chamber, primary settling tank and clarifier of the WWTP of Sari City, on the southern coast of the Caspian Sea, contained 12667 ± 668, 3514 ± 543 and 423 ± 44.9 MP/m3, respectively. Fibers accounted for 94.9%, 89.9% and 77.5% of the total number of MPs, respectively. The MP removal efficiency was 96.7%. MP shape (fiber, particle), size and structure were the most important factors determining their removal in different steps of the wastewater treatment process. The structure of microfibers (polyester, acrylic and nylon) and the consequent higher density than water explained their high removal (72.3%) in the primary settling tank. However, size was more important in microparticle removal with particles ≥500 µm being removed in the primary settling tank and <500 µm in the clarifier unit. The smallest particles (37-300 µm) showed the lowest removal efficiency. The predominant types of fibers and particles were polyester and polyethylene, respectively, which are likely to originate from the washing of synthetic textiles and from microbeads in toothpaste and cosmetics. Despite the efficiency of the Sari WWTP in removing MPs, it remains a major emission source of MPs to the Caspian Sea due to its high daily discharge load.

Quantifying and identifying microplastics in the effluent of advanced wastewater treatment systems using Raman microspectroscopy.

Microplastics in wastewater treatment plant (WWTP) effluent have been identified and quantified, but few studies have examined the microplastics in advanced treatment systems. A new method for isolating, quantifying, and determining the polymer type of microplastics was developed that included chemical digestion coupled with Raman microspectroscopy to investigate microplastics in the effluent of reverse osmosis nanofiltration and activated carbon filtration systems. This method allows for the removal of organics and the quantification and identification of all microplastics present in the sample. A large number of microplastics, the majority of which were smaller than 10 µm, were identified in the effluent of the advanced filtration systems with polyethylene the most common polymer identified. This study not only reports a new method for microplastic identification and quantification but also shows the importance of measuring the smallest fraction of microplastics, those smaller than 20 µm, which have previously been understudied.

Gas chromatography-Mass Spectra analysis and deleterious potential of fungal based polythene-degradation products.

Polythene-degradation products (PE-DPs) produced due to two most efficient polythene degrading fungal isolates (Aspergillus terreus strain MANF1/WL and Aspergillus sydowii strain PNPF15/TS) after 60 days of incubation at ambient temperature with continuous shaking were analyzed by employing GC-MS method. Total 24 PE-DPs were recorded in total 4 samples i) control (pH 3.5), ii) Treatment of Aspergillus terreus strain MANF1/WL (pH 3.5), iii) control (pH 9.5) and iv) Treatment of Aspergillus sydowii strain PNP15/TS (pH 9.5). To check the deleterious status of PE-DPs using both the elite fungal isolates at in vitro level, two living systems (Sorghum and Tiger shark) were used. The percent germination rate of sorghum seeds were found unaffected with PE-DPs of both elite fungi. PE-DPs of both the fungal isolates exhibited maximum germination index at 50%. Whereas, highest elongation inhibition rate (34.75 ± 7.10) was reported with PE-DPs of Aspergillus terreus strain MANF1/WL. In case of animals system, no mortality of the Tiger sharks was documented after fifteen days of the treatment.

[Isolation of polyethylene microbeads in cosmetics by double-density separation].

OBJECTIVE: To develop a stable method for isolation and quantitation of polyethylene microbeads in cosmetics and to observe its morphology and size. METHODS: Polyethylene microbeads were isolated by using the difference of relative density between polyethylene and two kinds of separation solutions( sodium chloride solution and acetonitrile). The contents of polyethylene microbeads in cosmetics were determined by gravimetric method. The morphology and particle size were observed by microscope. RESULTS: A stable method was developed by optimizing experimental method. The recoveries were from 93. 2% to 98. 2%, and the relative standard deviations varied in the range from 0. 16% to 2. 81%. Samples labeled containing microbeads could be isolated polyethylene microbeads, and the contents were from 0. 11% to 7. 76%, and size ranged from 100 µm to 200 µm. The morphology of isolated polyethylene microbeads were mostly regular, and color were mainly blue and white. CONCLUSION: The developed method is simple, repeatable and reliable that can be used for isolation and quantitation of polyethylene microbeads with a density lower than 1 g/cm in cosmetics.

Separating effective high density polyethylene segments from olefin block copolymers using high temperature liquid chromatography with a preloaded discrete adsorption promoting solvent barrier.

Recent advances in catalyst technology have enabled the synthesis of olefin block copolymers (OBC). One type is a "hard-soft" OBC with a high density polyethylene (HDPE) block and a relatively low density polyethylene (VLDPE) block targeted as thermoplastic elastomers. Presently, one of the major challenges is to fractionate HDPE segments from the other components in an experimental OBC sample (block copolymers and VLDPE segments). Interactive high temperature liquid chromatography (HTLC) is ineffective for OBC separation as the HDPE segments and block copolymer chains experience nearly identical enthalpic interactions with the stationary phase and co-elute. In this work we have overcome this challenge by using liquid chromatography under the limiting conditions of desorption (LC LCD). A solvent plug (discrete barrier) is introduced in front of the sample which specifically promotes the adsorption of HDPE segments on the stationary phase (porous graphitic carbon). Under selected thermodynamic conditions, VLDPE segments and block copolymer chains crossed the barrier while HDPE segments followed the pore-included barrier solvent and thus enabled separation. The barrier solvent composition was optimized and the chemical composition of fractionated polymer chains was investigated as a function of barrier solvent strength using an online Fourier-transform infrared (FTIR) detector. Our study revealed that both the HDPE segments as well as asymmetric block copolymer chains (HDPE block length≫VLDPE block length) are retained in the separation and the barrier strength can be tailored to retain a particular composition. At the optimum barrier solvent composition, this method can be applied to separate effective HDPE segments from the other components, which has been demonstrated using an experimental OBC sample.

Estimation of critical conditions of polymers based on monitoring the polymer recovery.

Liquid chromatography at critical conditions (LCCC) is a very attractive chromatographic technique on the border between the size exclusion and liquid adsorption mode of the liquid chromatography. The strong interest in LCCC arises from the fact that it is well suited to analyze the block lengths in segmented copolymers or the heterogeneities with regard to end groups present, for example, in functionalized polymers e.g., telechelics. In this paper a new method for identification of the critical conditions of synthetic polymers is proposed, which requires only one polymer sample with higher molar mass. The method is based on monitoring the recovery of the polymer sample from a column. The composition of the mobile phase is modified until the polymer sample is fully recovered from the column. The corresponding composition of the mobile phase is composition corresponding to LCCC. This new method was applied for the determination of critical conditions for polyethylene, syndiotactic polypropylene and isotactic polypropylene. The results of the new method will be compared to those of classical approaches and advantages will be pointed out.

Separation of bimodal high density polyethylene using multidimensional high temperature liquid chromatography.

High-temperature two-dimensional liquid chromatography (HT 2D-LC) using HT-HPLC as first dimension and HT-SEC as second dimension holds enormous potential to investigate the distribution according to molar mass and chemical composition of bimodal high density polyethylene (BiHDPE), as it avoids drawbacks of crystallization-based techniques. In this study, we have stepwise optimized the chromatographic parameters of 1D, comprising gradient slope and temperature, using model homo- and copolymers of ethylene with the aim to minimize the impact of molar mass on the compositional separation. Then the HT-HPLC was hyphenated to HT-SEC and optimum conditions for the volume of the sample transfer loop were probed with regard to the resolution of BiHDPE into the individual constituents HDPE and LLDPE. A particular important aspect was the use of infrared (IR) detection, and the demands it puts on the chromatographic aspects: We have shown that IR detection can be successfully applied in HT 2D-LC of BiHDPE, which is broadly distributed with regard to short chain branching and molar mass, only when the separation in 2D is optimized with regard to chromatographic resolution. As final result a bimodality is evident in the contour and the 3D surface plots as well as in both HPLC and SEC projections generated from HT 2D-LC.

Use of cortical neuronal networks for in vitro material biocompatibility testing.

Neural interfaces aim to restore neurological function lost during disease or injury. Novel implantable neural interfaces increasingly capitalize on novel materials to achieve microscale coupling with the nervous system. Like any biomedical device, neural interfaces should consist of materials that exhibit biocompatibility in accordance with the international standard ISO10993-5, which describes in vitro testing involving fibroblasts where cytotoxicity serves as the main endpoint. In the present study, we examine the utility of living neuronal networks as functional assays for in vitro material biocompatibility, particularly for materials that comprise implantable neural interfaces. Embryonic mouse cortical tissue was cultured to form functional networks where spontaneous action potentials, or spikes, can be monitored non-invasively using a substrate-integrated microelectrode array. Taking advantage of such a platform, we exposed established positive and negative control materials to the neuronal networks in a consistent method with ISO 10993-5 guidance. Exposure to the negative controls, gold and polyethylene, did not significantly change the neuronal activity whereas the positive controls, copper and polyvinyl chloride (PVC), resulted in reduction of network spike rate. We also compared the functional assay with an established cytotoxicity measure using L929 fibroblast cells. Our findings indicate that neuronal networks exhibit enhanced sensitivity to positive control materials. In addition, we assessed functional neurotoxicity of tungsten, a common microelectrode material, and two conducting polymer formulations that have been used to modify microelectrode properties for in vivo recording and stimulation. These data suggest that cultured neuronal networks are a useful platform for evaluating the functional toxicity of materials intended for implantation in the nervous system.

Melt grafting of metal salts onto LLDPE backbone--an FTIR study.

The melt graft functionalization of metal di(meth)acrylates onto linear low density poly(ethylene) (LLDPE) at 160 degrees C under inert atmosphere is reported here. The post melt grafting FTIR-RI method was used to find out the % grafting of metal salts onto LLDPE backbone. Further, DSC, TGA and HRTEM techniques were introduced to explain the results. A plausible reaction mechanism was proposed.

Selective removal of polyethylene or polypropylene from their blends based on difference in their adsorption behaviour.

The adsorption of polyethylene and polypropylene on zeolites depends on the nature of zeolite, the solvent as well as the molar mass of the polymer sample. For example, linear polyethylene is strongly retained on zeolite SH-300 from decalin, while isotactic, syndiotactic or atactic polypropylene is fully eluted in this system. On the other hand, polypropylene is retained on zeolite CBV-780 from diphenylether, while linear polyethylene is eluted. These differences in the elution behaviour have been utilised for selective removal of either linear polyethylene or polypropylene from blends of both polymers. The desorption of the retained polymer is difficult, or at times impossible. However, the selected adsorption systems have complimentary character, i.e. either one or second component is eluted or fully retained. Thus these sorbent/solvent systems, identified herein, are the first isocratic chromatographic systems, which enable selectively to remove polyethylene or polypropylene from their mixture. Moreover, decalin/SH-300 enables the removal of both linear and branched polyethylene from mixtures with random ethylene/propylene copolymers (polyethylene fully retained, ethylene/propylene copolymers eluted).

Characteristics of polyethylene wear particles isolated from synovial fluid after mobile-bearing and posterior-stabilized total knee arthroplasties.

The size, shape, and number of polyethylene wear particles found in synovial fluids of patients 1 year after implantation of 22 well-functioning total knee prostheses (11 contemporary mobile-bearing type, 11 posterior-stabilized type) were determined. Polyethylene wear particles were isolated from synovial fluids and examined by scanning electron microscopy. Particle size (equivalent circle diameter) was 0.81 +/- 0.12 microm (mean +/- standard error) in mobile-bearing types and 0.78 +/- 0.08 microm in posterior-stabilized types. Particle shape (aspect ratio) was 1.94 +/- 0.13 in mobile-bearing types and 2.30 +/- 0.22 in posterior-stabilized types. Total numbers of particles were (1.75 +/- 1.02) x 10(8) in mobile-bearing and (1.16 +/- 0.57) x 10(8) in posterior-stabilized types. The differences in these parameters between the two groups were not statistically significant. In the early stages after surgery, contemporary mobile-bearing types were comparable to posterior-stabilized types in terms of polyethylene wear-particle generation. The present results do not support the proposition that has been put forward in the literature; namely, that the contemporary mobile-bearing design has an advantage, in terms of the polyethylene wear rate. These data suggest that the advantage of complete conformity in the femoro-tibial articulating surface of contemporary mobile-bearing design may be offset by wear of the mobile undersurface and slot, apart from the articulating surface.

Foreign body reactions in lymph nodes of oncology patients with joint prostheses--light-, electron microscopic and immunohistological investigations.

Foreign body reactions in lymph nodes caused by wear particles from joint prostheses can mimic different lymphadenopathies, including metastatic cancer. The knowledge of these alterations is particularly important for pathologists performing frozen section diagnosis for oncology patients. As recent investigations of pseudocapsules have revealed that most of the wear particles are submicron-sized, transmission electron microscopic investigations were additionally performed. The histological investigation of the pelvic lymph nodes of 22 oncology patients with joint prostheses showed that the bone cement wear prevailed. At least small amounts of polyethylene wear particles were also found in all cases. Metallic wear particles were detected in 90% of the cases. The wear particles induce a macrophage-rich foreign body reaction that can cause an architectural effacement of the lymph nodes. The electron microscopic investigations showed that submicron-sized wear particles prevail. Some of them form conglomerates in size ranges detectable by light microscopy. The immunohistochemical studies showed that the foreign body reactions comprised mature CD163- and PGM1-positive macrophages and few lymphocytes, predominantly T-lymphocytes. The knowledge of the characteristic alterations of regional lymph nodes seems important in order to avoid misinterpretations. Therefore, in particular the detection of intracytoplasmatic wear particles is helpful in this respect.

A new method for isolation of polyethylene wear debris from tissue and synovial fluid.

Sub-micron-sized ultrahigh molecular-weight polyethylene (PE) debris is generated in the joint space as a result of articulation and cyclic loading of an orthopaedic implant. Its characterization requires isolation and subsequent analysis by ultra-structural methods. An innovative method based on the digestion of paraffin-embedded tissue samples was proposed. Tissue slices were digested with sodium hypochlorite directly on polycarbonate filter. The same procedure could be applied also to fresh synovial fluid. Plastic particles were not lost or damaged during treatment. Chemical identification of particles was done by micro-Raman spectroscopy that confirmed purity of retrieved PE particles. Size and shape of PE particles were characterised using scanning electron microscopy and were comparable in number and morphology to the retrieval by other authors. Equivalent diameter ranged from 0.48 to 0.95microm and particle number ranged from 9 to 23x10(9)/cm(3).

Predictive functional control (PFC) and its application in chlorinated polyethylene process.

The main principle and the characteristic of Predictive Functional Control (PFC) strategy are presented in this paper and the corresponding control system aid design software APC-PFC is also introduced. For a chlorinated polyethylene (CPE) process, a design scheme of cascade predictive functional control system is described and the control performance is improved obviously.

Comparison of three joint simulator wear debris isolation techniques: acid digestion, base digestion, and enzyme cleavage.

Quantification of ultrahigh molecular weight polyethylene (UHMWPE) wear debris remains a challenging task in orthopedic device analysis. Currently, the weight loss method is the only accepted practice for quantifying the amount of wear generated from a PE component. This technique utilizes loaded soak controls and weight differences to account for polymeric material lost through wear mechanisms. This method enables the determination of the amount of wear in the orthopedic device, but it provides no information about debris particulate size distribution. In order to shed light on wear mechanisms, information about the wear debris and its size distribution is necessary. To date, particulate isolation has been performed using the base digestion technique. The method uses a strong base, ultracentrifugation, and filtration to digest serum constituents and to isolate PE debris from sera. It should be noted that particulate isolation methods provide valuable information about particulate size distribution and may elucidate the mechanisms of wear associated with polymeric orthopedic implants; however, these techniques do not yet provide a direct measure of the amount of wear. The aim of this study is to present alternative approaches to wear particle isolation for analysis of polymer wear in total joint replacements without recourse to ultracentrifugation. Three polymer wear debris isolation techniques (the base method, an acid treatment, and an enzymatic digestion technique) are compared for effectiveness in simulator studies. A requirement of each technique is that the wear particulate must be completely devoid of serum proteins in order to effectively image and count these particles. In all methods the isolation is performed through filtration and chemical treatment. Subsequently, the isolated polymer particles are imaged using scanning electron microscopy and quantified with digital image analysis. The results from this study clearly show that isolation can be performed without the use of ultracentrifugation and that these methods provide a viable option for wear debris analysis.