Plastic pollution has become one of the most pressing environmental issues. Recycling is a potential means of reducing plastic pollution in the environment. However, plastic fragments are still ...likely released to the aquatic environment during mechanical recycling processes. Here, we examined the plastic inputs and effluent outputs of three mechanical recycling facilities in Vietnam dealing with electronic, bottle, and household plastic waste, and we found that large quantities of microplastics (plastics <5 mm in length) are generated and released to the aquatic environment during mechanical recycling without proper treatment. Comparisons with literature data for microplastics in wastewater treatment plant effluents and surface water indicated that mechanical recycling of plastic waste is likely a major point source of microplastics pollution. Although there is a mismatch between the size of the microplastics examined in the present study and the predicted no-effect concentration reported, it is still possible that microplastics generated at facilities pose risks to the aquatic environment because there might be many plastic particulates smaller than 315 μm, as suggested by our obtained size distributions. With mechanical recycling likely to increase as we move to a circular plastics economy, greater microplastics emissions can be expected. It is therefore an urgent need to fully understand not only the scale of microplastic generation and release from plastic mechanical recycling but also the environmental risk posed by microplastics in the aquatic environment.
Display omitted
•Mechanical recycling without wastewater treatment was at least a source of microplastic.•Effluent microplastic concentrations were from 1.1 × 105–2.0 × 108 MP particulates/m3.•Annual microplastic emissions from these facilities were from 0.014 to 5.8 t/year.
Nanoplastics are likely ubiquitous in the environment, and their potential toxic effects are a concern. However, quantitative information about the distribution of nanoplastics is still lacking, and ...toxicity tests are limited to a few select polymers because of the lack of appropriate standard materials, which should be nanoscale particles with standardizable morphologies, properties comparable to those of commercial polymers, and no impurities. Here, a precipitation‐based method for preparing spherical nanoscale particles without the introduction of impurities is developed. The similarity of the molecular weight distributions, crystallinities, and thermal properties of five major polymers prepared using this method—low‐density polyethylene, high‐density polyethylene, polypropylene, polyvinyl chloride, and polystyrene—to those of commercial polymers indicate their potential for use as standard nanoplastic particles. This study provides a fundamental approach for the synthesis of standard nanoplastic particles that will facilitate quantification of the concentrations of nanoplastics in the environment and tests of their toxicity, which are required to assess the risks associated with exposure to them.
This paper reports precipitation‐based methods for preparing spherical nanoscale particles of five major polymers—low‐density polyethylene, high‐density polyethylene, polypropylene, polyvinyl chloride, and polystyrene—without the introduction of impurities. Subsequent analysis reveals their potential for use as standard nanoplastic particles that could facilitate quantification of the concentrations of nanoplastics in the environment and determination of their toxicity.
Wastes containing short-chain chlorinated paraffins (SCCPs) at concentrations above the Basel Convention low persistent organic pollutant content (LPC) values must be destroyed or irreversibly ...transformed in an environmentally-sound manner. Here, we developed a novel liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–ESI-MSMS) method for determining the concentrations of SCCPs in mixed plastic wastes. Major SCCP homologues were identified with good separation and peak width by using a low-hydrophobicity cyano-propyl column and a mobile phase consisting of water and methanol containing ammonium acetate. Precursor ion peaks corresponding to the formation of stable SCCP homologue–adducts were observed, followed by two intense product ion peaks corresponding to separation of the adduct into acetate and the homologue. The formulation of a novel calibration standard with known SCCP homologue percentage composition supported the development of our novel mass spectrometric technique. The results obtained with the LC–ESI-MSMS system were quantitatively and qualitatively comparable with those obtained with a high-resolution mass spectrometry (HRMS) coupled to gas chromatography (GC) system. Homologue concentrations determined by LC–ESI-MSMS were significantly correlated with those determined by GC–HRMS in samples of commercial chlorinated paraffin mixture and mixed plastic waste, respectively. As a complementary technique to the highly accurate, but less versatile GC–HRMS approaches, the SCCP analysis by LC–ESI-MSMS is a practical way to identify mixed plastic wastes containing SCCPs at concentrations higher than the Basel Convention’s LPC value.
•Novel mass spectrometric method to quantify SCCPs in plastic wastes was developed.•Major SCCP homologues were identified with good separation and peak width.•Present data were in good agreement with high-resolution mass spectrometry data.•Plastic wastes containing SCCPs above Basel Convention limits can be identified.
•Grease trap waste (GTW) addition was employed to co-digest with food waste (FW).•The lipid loading lower than 1.61 g/(L·d) did not result in digester failure.•GTW addition could increase methane ...yield up to 68% compared to mono-digestion.•Palmitic acid dominated the residual long chain fatty acids, accounting for 73.7%.•The acetoclastic methanogenic activity was promoted by increased GTW addition.
In order to boost the economics of biogas utilization in those small facilities for food waste (FW) digestion, proximate grease trap waste (GTW) was employed to co-digest with FW. A bench-scale continuous stirred tank reactor was set up and operated at mesophilic temperature to investigate the co-digestion limit and lipid/long chain fatty acid (LCFA) conversion by increasing lipid loading stepwise. Mixing FW and GTW at lipid/total solids (TS) 55%, where the lipid loading was 1.61 g/(L·d), was proved to be appropriate, and the maximum methane yield reached 68% higher than the mono-digestion of FW, with a similar lipid reduction at approximately 90%. In addition, since acetic acid accumulation above 100 mg HAc/L had been observed under the optimal loading, the threshold value for anaerobic co-digestion of FW and GTW was confined to the lipid loading around 1.61 g/(L·d). The rapid recovery strategy of mixing the inhibited sludge with fresh inoculum at 1:4 (V/V) took effect after process failure resulted from further increasing lipid/TS to 70%. Lipid/LCFA concentrations in the effluent rose with the increased lipid loading, while palmitic acid accounted for the most percentage among the residual LCFAs, as high as 73.7% at lipid/TS 55%. Acetoclastic methanogens played an important role in accelerating process conversion, due to the fact that raising GTW addition led to the increased methanogenic activity, with a value of 26.9 mL-CH4/(g-VS·d) at the optimal loading.
The transesterification of various triglycerides was considered in terms of the activation energy obtained from quantum computational chemistry. According to these values, the effect upon the ...reactivity of the structure of the triglyceride is not particularly large. Moreover, the transesterification reaction is completed via a transition state, in which ring formation consisting of the carbon of the carboxyl and alkoxy groups appears, even if a long-chain alcohol is used as a reactant. Finally, an ideal reaction pathway, in which the ester bond at the center of the triglyceride is transesterified before peripheral ester bonds, was shown by an activation energy analysis and electrostatic potential (ESP) distribution.
Display omitted
•Oil content was extracted from grease trap waste (GTW) by heat-treatment.•A high purity oil equivalent to an A-grade fuel oil with 81–93wt% of efficiency.•Anaerobic digestion of ...post-extracted residue was inhibited by long-chain fatty acid.•Ca-added digester achieved stable semi-continuous operation over one year.
An effective way for restaurant grease trap waste (GTW) treatment to generate fuel oil and methane by the combination of physiological and biological processes was investigated. The heat-driven extraction could provide a high purity oil equivalent to an A-grade fuel oil of Japanese industrial standard with 81–93wt% of extraction efficiency. A post-extracted residue was treated as an anaerobic digestion feedstock, and however, an inhibitory effect of long chain fatty acid (LCFA) was still a barrier for high-rate digestion. From the semi-continuous experiment fed with the residual sludge as a single substrate, it can be concluded that the continuous addition of calcium into the reactor contributed to reducing LCFA inhibition, resulting in the long-term stable operation over one year. Furthermore, the anaerobic reactor performed well with 70–80% of COD reduction and methane productivity under an organic loading rate up to 5.3g-COD/L/d.
Oily organic waste is a promising feedstock for anaerobic co-digestion. Free long-chain fatty acids (LCFAs) produced from lipids can inhibit methanogenic consortia, so optimal control of LCFA ...concentration is the key to successful operation of co-digestion. Most LCFAs are present in the solid phase, making them difficult to be detected and monitored. This study proposes a simple and easy method for detecting LCFAs in both the liquid and solid phases of anaerobic digestate by combining liquid–liquid extraction followed by solid-phase extraction (SPE) and spectrophotometric analysis. The extraction procedure successfully removed impurities that interfere with the absorbance spectrum and ensured high recovery rates of LCFAs. The utility of the pretreatment used for the extraction was discussed using thermodynamic analysis and calculations of phase equilibrium for the solvent extraction system. The absorbance spectrum shift of pyridinium N-phenolate betaine (PNPB) dye-stained solution showed a good correlation with LCFA concentration and enabled highly sensitive measurements. Good quantification was demonstrated in experiments using various digestate samples obtained from the laboratory, pilot, and full-scale reactors.
In recent years, concern about the release of anthropogenic organic micropollutants referred to as contaminants of emerging concern (CECs) has been growing. The objective of this study was to find ...potential CECs by means of an analytical screening method referred to as comprehensive target analysis with an automated identification and quantification system (CTA-AIQS), which uses gas and liquid chromatography combined with mass spectrometry (GC-MS and LC-QTOF-MS). We used CTA-AIQS to analyze samples from a sediment core collected in Beppu Bay, Japan. With this method, we detected 80 compounds in the samples and CTA-AIQA could work to useful tool to find CECs in environmental media. Among the detected chemicals, three PAHs (anthracene, chrysene, and fluoranthene) and tris(isopropylphenyl)phosphate (TIPPP) isomers were found to increase in concentration with decreasing sediment depth. We quantified TIPPP isomers in the samples by means of targeted analysis using LC-MS/MS for confirmation. The concentration profiles, combined with previous reports indicating persistent, bioaccumulative, and toxic properties, suggest that these chemicals can be categorized as potential CECs in marine environments.
Display omitted
•Comprehensive analysis method (AIQS) were used for sediment core from Japan.•We try to find potential contaminants of emerging concern (CECs).•AIQA could work as useful tool to find CECs in environment.•TIPPPs, anthracene, chrysene, and fluoranthene were potential CECs.
To study solute distribution at the solid–liquid (S–L) interface during melt crystallization, we examined the applicability of the interfacial solute distribution factor proposed based on a kinetic ...model involving both mass and heat balances at the interface. The factor derived from the model was compared with the experimental results obtained by employing a binary melt with the different species and concentrations of fatty acids as biodiesel related mixtures. As a result, we were able to reveal the empirical relation between the purity of the crystal and the solidification conditions of the melt. Based on the model, we also numerically calculated the transient changes in the interfacial solute distribution factor as well as the temperature of the S–L interface in the solidification process of the melt. The minimization of the factor was confirmed when the melt was supercooled at the S–L interface after starting solidification.
•Melt crystallization of fatty acids as biodiesel related mixtures.•Solute distribution at the solid–liquid (S–L) interface.•Interfacial solute distribution factor.•Relationship between the purity of the crystal and the solidification conditions.•Numerical calculation of the interfacial solute distribution factor.
