Chemiluminescence sensing for Hg2+ in environment water using carbon materials from PVC dechlorination as signal initiator

Carbon-based materials from waste PVC/iron chips dechlorination as peroxidase mimics for total antioxidant capacity biosensing

The monitoring of antioxidant capacity is very important to evaluate the quality of antioxidant foods or drugs for market regulation. Herein, dechlorination treatment of waste PVC/scrap irons were conducted in subcritical water to obtain carbon-based Fe composites (CM-Fe-dPVC) with peroxidase-like activity. The electron bonding of C 2p and Fe 3d orbital led to strong electron migration ability. CM-Fe-dPVC exhibited excellent activity of simulated peroxidase. Vitamin C (VC) and CM-Fe-dPVC had competitive behaviors on •OH generation in TMB oxidation reaction. A portable paper based colorimetric test kit was developed for monitoring total antioxidant capacity of beverages and pharmaceuticals on the market (with the detection limit of 0.1 μM for Vc). The results of life cycle assessment (LCA) revealed that the proposed strategy had low global warming potential. This research could provide important reference for high value recycling of organic solid wastes.

A low-temperature co-treatment of diethylhexyl phthalate-rich polyvinyl chloride and waste copper catalyst by subcritical water (hydrothermal treatment): Dechlorination, recovery of diethylhexyl phthalate and copper

As one of the most widespread plastics in the world, the recycling of diethylhexyl phthalate-rich polyvinyl chloride (DEHP-rich PVC) faces great challenges because of the high levels of Cl and plasticizers. On the other hand, waste copper catalyst (WCC) discharged from various industrial processes is not effectively recycled. In this study, a significant synergistic effect between the DEHP-rich PVC and WCC was found in a subcritical water (SubCW) medium, and a co-treatment of the DEHP-rich PVC and WCC was developed by the SubCW process. The introduction of WCC significantly improved the dechlorination efficiency of the DEHP-rich PVC to 96.03 % at a low temperature of 250 °C. Under the optimal conditions, the leaching of copper from WCC reached a maximum of 81.08 %. Oil products included DEHP (55.7 %, GC peak area%), 3-methyl-3-heptene (37.3 %, GC peak area%), and 2-ethyl-1-hexanol (7.0 %, GC peak area%). The dechlorination pathways of the DEHP-rich PVC included hydroxyl substitution and direct dechlorination. HCl released from the DEHP-rich PVC led to a decrease in the pH of the system and significant copper leaching from the WCC. DEHP was decomposed by hydrolysis, dehydration, and rearrangement reaction by the SubCW co-treatment process. The enhancement mechanism of the WCC for the dechlorination of the DEHP-rich PVC was based on that the conversion of copper species in the SubCW promoted the formation of hydroxyl radicals and the hydroxyl substitution for chlorine in PVC molecular chain. The proposed SubCW low-temperature co-treatment could be a prospective strategy for the low-energy and synchronous recovery of the two different wastes of the DEHP-rich PVC and WCC.

An ingenious chemiluminescence sensing strategy for recalcitrant triphenyl phosphate based on oxidant-free UV-activated MIL-100(Fe) gel system

BACKGROUND

Organophosphate flame retardants (OPFRs) are notorious emerging contaminants threatening the environment and human health. Triphenyl phosphate (TPHP), which has an extremely serious biotoxicity, is a typical harmful OPFR. Due to its wide use, TPHP has been discovered in various environmental mediums. Moreover, it is pretty recalcitrant to the removal process, resulting in the need for a technique to understand it better. Hence, accurate and quick discrimination of TPHP in the environment is critical to further evaluate its potential effect on ecosystems and human health.

RESULTS

An ingenious oxidant-free chemiluminescence (CL) sensor based on the oxidant-free UV/MIL-100(Fe) gel system was established for TPHP detection. The oxidation of luminol in the UV-activated MIL-100(Fe) gel has resulted in remarkable CL emission, which is contributed by reactive oxygen species (ROS) generated by it. Notably, the CL intensity was inhibited significantly after introducing TPHP. An investigation into the mechanism underlying the effect of CL suppression demonstrated that TPHP competed with luminol to consume ROS from UV-activated MIL-100(Fe) gel, contributing to CL inhibition. The subsequent sensing performance experiments demonstrated the advantages of environmentally friendly, economic efficiency, user-friendly operation, rapid determination, potential for compact size, high selectivity, and sensitivity. Additionally, these investigations confirmed the low limit of detection (210 ng L-1) and wide linear range (10-1000 μg L-1).

SIGNIFICANCE

In this paper, a green, economical, and oxidant-free CL sensing strategy for TPHP has been established. It has the advantage of being rapid, having the potential for compact size, high selectivity, and sensitivity. This ingenious method has promising applications in real-time and online environmental monitoring, and it paves the way for the rapid and environmentally friendly identification of emerging contaminants that are structurally stable and recalcitrant to remove.

Controlled electrocatalysis of the dechlorination and detoxification of chlorinated ethylenes to avoid production of highly toxic intermediates

In this study, electrochemical dechlorination and detoxification of a mixture of chlorinated ethylenes was investigated under various conditions using a double monoatomic synergistic metal catalytic cathode. Electrocatalytic degradation of mixed chlorinated with stepwise voltage and alternating current exhibited excellent dechlorination efficiency. The removal ratios of 1,2-dichloroethylene (1,2-DCE), trichloroethylene (TCE), and tetrachloroethylene (PCE) reached 78.79 %, 79.27 %, and 93.44 % in 10 min, and 98.14 %, 97.56 %, and 98.70 % in 30 min, respectively. The toxicity was evaluated using a quantitative structure-activity relationship model. The cumulative toxicity was reduced to 8.00 % of the initial cumulative toxicity in 30 min. An electrochemical dechlorination strategy for selective degradation and detoxification of mixtures of chlorinated pollutants is proposed. Controlled dechlorination and detoxification under low-voltage control avoided the accumulation of toxic intermediates. Cumulative toxicity was reduced by strategies of selective dechlorination, and segmented and alternating current decreased the energy consumption. The strategy provides a basis for alternating current electrocatalytic dechlorination associated with mixed chlorinated pollutants treatment.

Upcycling of waste disposable medical masks to high value-added gasoline fuel and surfactants products by sub/supercritical water degradation and partial oxidation

The amount of waste disposable medical masks (DMMs) and the potential environmental risk increased significantly due to the huge demand of disposable medical surgical masks. In this study, two effective and environmentally friendly processes, supercritical water degradation (SCWD) and subcritical water partial oxidation (SubCWPO), were proposed for the upcycling of DMMs. The optimal conditions for the SCWD process (conversion ratio>98 %) were 410 ℃, 15 min, and 1:5 g/mL. The oil products obtained from the SCWD process were mainly small molecule hydrocarbons (C7-C12) with a content of 86 % and could be recycled as fuel feedstock for gasoline. Alkyl radicals in the SCWD reaction formed double bonds and ring structures through hydrogen capture reactions, β-scission, and dehydrogenation reactions, and aromatic hydrocarbons were formed by olefin cyclization and cycloalkane dehydrogenation. The introduction of an oxidant (H2O2) to the reaction system could significantly reduce the reaction temperature and shorten the reaction time. At 350 ℃, 15 min, 1:20 g/mL, V(H2O2): V (H2O) of 1:1, the conversion ratio of the SubCWPO process was 88 %, which was higher than that of the SCWD process at 400 ℃ (71.49 %). Oil products produced from the SubCWPO process were rich in alcohols and esters, which could be used as raw materials for nonionic surfactant of polyol and fatty acid ester. The abundant hydroxyl radical in the SubCWPO system trapped hydrogen atoms on PP and reacted with the resulting alkyl radical to form alkanols, which was oxidized to form acids. The esterification of acids and alkanols formed high level of esters. The SCWD and SubCWPO processes proposed in this study are believed to be promising strategies for DMMs degradation and the recovery of high value-added hydrocarbons.

Novel approach for green synthesis of stable gold nanoparticles with dried turmeric root extract: investigations on sensor and catalytic applications

In this study, we present the synthesis of gold nanoparticles (AuNPs) using a completely green synthesis method without the use of any additional functionalizing agent, except dried turmeric root extract. The significant synthesis parameters were optimized, and the applicability of AuNPs was investigated in areas such as plasmonic and fluorescent sensing of aluminum (Al3⁺) and chromium (Cr3⁺) ions, reduction of 4-nitrophenol (4-NP), and degradation of methylene blue (MB) and methyl orange (MO) dyes. Characterization studies were performed using UV-Vis spectroscopy, TEM, FTIR, and XRD, revealing that the AuNPs predominantly had a spherical morphology and a very small particle size of 8.5 nm, with stability maintained up to 120 days. The developed AuNP-based plasmonic sensors relied on aggregation-induced decreases in absorption, along with a red shift in the spectra. Fluorescence sensing demonstrated a linear increase in intensity with increasing concentrations of Al3⁺ and Cr3⁺, with detection limits of 0.83 and 1.19 nM, respectively. The catalytic activities of AuNPs were tested in reducing 4-NP and degradations of MB and MO dyes (binary system) in tap water and wastewater, with the reactions following pseudo-first-order kinetics. This study highlights the potential of AuNPs synthesized from turmeric roots for various environmental and sensing applications.

Low-cost and sensitive chemiluminescence detection of phthalates in environment by signal sensing of carbon-based materials from PVC/coal gangue dechlorination

BACKGROUND

The detection of plasticizers in the environment is important to prevent environmental risks and people's health hazards. Improving recycling efficiency of waste PVC still faced challenges.

RESULTS

In this work, it was found that solid products from waste PVC/coal gangue dechlorination in subcritical water (dPVC) had strong catalysis activity for luminol-H2O2 chemiluminescence (CL) reaction. Phthalates, common plasticizers, could bond and adsorb on dPVC, which greatly inhibited the luminol-H2O2-dPVC CL reaction. Based on this, a low-cost CL analysis was constructed for the detection of phthalates combinations (PACs) and di-(2-ethylhexyl) phthalate (DEHP) in the environment. The detection limit for PACs and DEHP was 0.048 ng/L and 0.13 ng/L, respectively. Compared with HPLC standard method, the dPVC CL analysis had accuracy and reliability for the detection of phthalates in actual environmental samples. Besides, the results of life cycle assessment (LCA) revealed that dPVC for CL sensing materials had significantly small global warming potential (GWP).

SIGNIFICANCE

The use of dPVC for CL sensing not only improved the recycling efficiency of PVC, but also reduced carbon emissions of obtaining CL sensing materials.

Low-temperature subcritical water dechlorination composites of waste PVC/coal fly ash with powerful sensing activity for chemiluminescent detection of acetamiprid and imidacloprid

Pesticide residues in agricultural products are serious threat to people's health. Real-time monitoring of pesticides residues in the environment and agricultural products posed challenges to sustainable methods with high analytical performance for pesticide detection. Herein, waste PVC/coal fly ash (the mass ratio of PVC and coal fly ash was 4:1) was dechlorinated in subcritical water at low temperature to achieve nearly 100 % dechlorination of PVC and obtain carbon-based composite materials (CM-Fe/Al/Si-dPVC) with strong sening activity. For CM-Fe/Al/Si-dPVC, CFe bonding resulted in strong electron migration, and nano/μm SiO2 and Al2O3 doping in the layered polyene C matrix provided large specific surface area, and silicon hydroxyl created good heterogeneous catalytic interfaces. CM-Fe/Al/Si-dPVC could strongly trigger luminol chemiluminescence (CL) reaction and produce intense CL signals. Neonicotinoid pesticides (acetamiprid and imidacloprid) bonded with CM-Fe/Al/Si-dPVC through coordination chelation and hydrogen bonding, which shielded the catalytic active site and increased the Fermi level of system, thus quenching CL reaction. Inspired by these, a cheap CL assay was constructed for detecting neonicotinoids combinations of acetamiprid and imidacloprid (NICs). The detection limits of NICs were 0.7 ng/L. Satisfactory recoveries were obtained for real agricultural products and environmental samples. The results of life cycle evaluation (LCA) revealed that the strategy had significantly small global warming potential (GWP). This work presented a sustainable method with environmental benefits for the detection of neonicotinoids, and also opened up new way for the recycling of organic solid wastes.

Hydrothermal dechlorination strategy for high-quality oil recovery from polyvinyl chloride

The global production of PVC is around 3.5 million tons each year. Unfortunately, the disposal of PVC waste releases toxic substances such as hydrochloric acid, polychlorinated dioxins, and furans, which can harm the environment. Therefore, there is an urgent need for a safe and environmentally friendly thermochemical treatment method that reduces the damage caused by HCl gas produced during PVC pyrolysis and improves the quality of pyrolysis oil. Hydrothermal treatment technology is one of the potential dechlorination strategies for PVC. However, its efficiency is reduced in the supercritical region, while the additives used result in secondary pollution and increased operating costs. This study is pioneering in its approach, aiming to produce high-quality oil with reduced chlorine through low-temperature hydrothermal treatment of PVC, all without additives. The results are promising, indicating that by administering steam at 250 °C with a 2.0-3.0 g-steam/g-feed ratio, we can significantly reduce chlorine content to 0.13 % while achieving an oil yield of up to 14.9 % from PVC. The hydrothermal process can reduce CO2 emissions by 15-43 % compared to pyrolysis methods, providing a simultaneous opportunity for carbon neutrality and resource recovery.

Upcycling of PVC waste to high-value sorbent with KOH-activation for efficient removal of organic dyes

Polyvinyl chloride (PVC), known for its chemical stability and flame-retardant qualities, has many uses in various fields, such as pipes, electric wires, and cable insulation. Research has established its potential recovery as a fluidic fuel through pyrolysis, but the use of PVC pyrolysis oil, which is tainted by chlorine, is constrained by its low heat value and harmful environmental effects. This study engineered a layered double hydroxide (LDH) to tackle these challenges. The LDH facilitated dechlorination during PVC pyrolysis and bolstered thermal stability via cross-linking. During pyrolysis with LDH, PVC was transformed into carbon-rich precursors to sorbents. Chemical activation of these residues using KOH created sorbents with a specific surface area of 1495.4 m2 g⁻1, rendering them hydrophilic. These resulting sorbents displayed impressive adsorption capabilities, removing up to 486.79 mg g⁻1 of methylene blue and exhibiting the simultaneous removal of cations and anions.

A novel subcritical water synergistic co-treatment of brominated epoxy resin and copper-based spent catalysts: debromination, phenol production, and copper recovery

In this study, a high-efficiency co-treatment strategy for brominated epoxy resin (BER) and copper-based spent catalyst (CBSC) was developed by using subcritical water (SubCW) process. Multivalent species of copper released from CBSC could accelerate the electron transfer of the SubCW system and efficiently catalyze radical reactions to promote the debromination and decomposition of BER, and had an effect on the capture and binding of bromine species. Meanwhile, the formation of HBr by the BER debromination resulted in a decrease in the system pH and markedly enhanced the leaching/recovery of Cu from CBSC. The optimal conditions of the SubCW co-treatment process were as follows: reaction temperature of 350 °C, solid-to-liquid ratio of 1:30 g/mL, BER-to-CBSC mass ratio of 10:1 g/g, and reaction time of 60 min. Under the optimal conditions, 97.12 % of the Br could be removed from BER by the SubCW co-treatment process and a high-purity phenol (64.09 %) could be obtained in the oil phase product, and 86.44 % of Cu in the CBSC could be leached and recovered. The introduction of CBSC significantly changed the decomposition path of BER. Compared to the SubCW process without CBSC, bromine-free oils products could be obtained by the co-treatment process of BER and CBSC at low-temperature. This study provided a novel understanding of resource conversion mechanism of BER and CBSC in subcritical water medium via the synergistic effect between the two different waste streams to improve treatment efficiency and synchronously recover high-value products.

Highly selective detection of deoxyribonucleic acid in living cells using RecA-green fluorescent protein-single-stranded deoxyribonucleic acid filament fluorescence resonance energy transfer probe

A fluorescence resonance energy transfer (FRET) method was developed for double-stranded deoxyribonucleic acid (dsDNA) detection in living cells using the RecA-GFP (green fluorescent protein) fusion protein filament. In brief, the thiol-modified single-stranded DNA (ssDNA) was attached to gold nanoparticles (AuNPs); on the contrary, the prepared RecA-GFP fusion protein interacted with ssDNA. Due to the FRET between AuNPs and RecA-GFP, fluorescence of RecA-GFP fusion protein was quenched. In the presence of homologous dsDNA, homologous recombination occurred to release RecA-GFP fusion protein. Thus, the fluorescence of RecA-GFP was recovered. The dsDNA concentration was detected using fluorescence intensity of RecA-GFP. Under optimal conditions, this method could detect dsDNA activity as low as 0.015 optical density (OD) Escherichia coli cells, with a wide linear range from 0.05 to 0.9 OD cells, and the regression equation was ΔF = 342.7c + 78.9, with a linear relationship coefficient of 0.9920. Therefore, it provided a promising approach for the selective detection of dsDNA in living cells for early clinical diagnosis of genetic diseases.

Pyrolysis of municipal plastic waste: Chlorine distribution and formation of organic chlorinated compounds

The release of chlorine during the pyrolysis of actual municipal plastic waste (MPW) was studied. Firstly, thermogravimetry-Fourier transform infrared (TG-FTIR) was analyzed to investigate the chlorine release behavior. Then, the effect of temperature on chlorine migrations was investigated by fast pyrolysis experiments in a fixed bed reactor. Results showed that chlorine released mainly between 241 and 353 °C in the form of HCl or chloroesters during MPW pyrolysis. After pyrolysis, chlorine was mainly distributed in the pyrolytic gas (74.34-82.89 %) and char (10.17-21.29 %). However, the release of chlorine was inhibited due to the melting behavior of MPW at <350 °C. Besides, the relative contents and types of organic chlorinated compounds in liquid products were both decreased with temperature. It was observed that polyethylene terephthalate (PET) was the greatest contributor to the formation of organic chlorinated compounds during MPW pyrolysis. Meanwhile, the pyrolysis of PET was significantly promoted by the HCl released from polyvinyl chloride (PVC). Subsequently, the pathways for the formation of organic chlorinated compounds through the co-pyrolysis of PVC and PET were proposed, including the initial degradation and subsequent chlorination of PET. These findings provided new insights into the release and regulation of chlorine-containing pollutants during actual MPW pyrolysis.