Pyrolysis-catalysis upcycling of waste plastic using a multilayer stainless-steel catalyst toward a circular economy.

Current un-sustainable plastic management is exacerbating plastic pollution, an urgent shift is thus needed to create a recycling society. Such recovering carbon (C) and hydrogen (H) from waste plastic has been considered as one practical route to achieve a circular economy. Here, we performed a simple pyrolysis-catalysis deconstruction of waste plastic via a monolithic multilayer stainless-steel mesh catalyst to produce multiwalled carbon nanotubes (MWCNTs) and H2, which are important carbon material and energy carrier to achieve sustainable development. Results revealed that the C and H recovery efficiencies were as high as 86% and 70%, respectively. The unique oxidation-reduction process and improvement of surface roughness led to efficient exposure of active sites, which increased MWCNTs by suppressing macromolecule hydrocarbons. The C recovery efficiency declined by only 5% after 10 cycles, proving the long-term employment of the catalyst. This catalyst can efficiently convert aromatics to MWCNTs by the vapor-solid-solid mechanism and demonstrate good universality in processing different kinds of waste plastics. The produced MWCNTs showed potential in applications of lithium-ion batteries and telecommunication. Owing to the economic profits and environmental benefits of the developed route, we highlighted its potential as a promising alternative to conventional incineration, simultaneously achieving the waste-to-resource strategy and circular economy.

Carbon nanotubes production from real-world waste plastics and the pyrolysis behaviour.

The investigation of the pyrolysis behaviour of real-world waste plastics (RWWP) and using them as the feedstock to produce carbon nanotubes (CNTs) could serve as an effective solution to address the global waste plastics catastrophe. This research aimed to characterize the pyrolysis behaviour of RWWP via thermogravimetric analysis (TG) and fast pyrolysis-TG/mass spectrometry (Py-TG/MS) analyses. Activation energies (131.04 kJ mol-1 -171.04 kJ mol-1) for RWWP pyrolysis were calculated by three methods: Flynn-Wall-Ozawa (FWO) method, Kissinger-Akahira-Sunose (KAS) method, and Starink method. Py-TG/MS results indicated that the RWWP could be identified as polystyrene (RWWP-1), polyethylene (RWWP-2), polyethylene terephthalate (RWWP-3, 4), and polypropylene (RWWP-5, 6). In addition, RWWP-1, 2, 5, 6 outperform RWWP-3 and 4 as sources of carbon for producing CNTs. The results showed a high carbon yield of 32.21 wt% and a high degree of CNT purity at 93.04%.

Integrated CO2 capture and reverse water-gas shift reaction over CeO2-CaO dual functional materials.

Achieving carbon neutrality is one of the most important tasks to meet the environmental challenges due to excessive CO2 emissions. Integrated CO2 capture and utilization (ICCU) represents an effective process for direct utilization of CO2-contained exhaust gas (e.g. flue gas), in which converting the captured CO2 into CO via reverse water-gas shift (RWGS) reaction is a promising route. The dual functional materials (DFMs), containing CO2 adsorbents and catalysts, are widely applied to achieve ICCU. The conventional active metals (Ni, Fe, etc.)-based DFMs and non-transition metal DFMs (e.g. CaO) are restricted by low CO selectivity, catalytic efficiency or CO generation in the CO2 capture step. To address the above obstructs in the application of DFMs, the metal oxides-based DFMs, MOx-CaO (M = Al, Ce, Ti or Zr), are synthesized and evaluated. The CeO2-CaO outperformed the other metal oxides-based DFMs and possessed significantly improved catalytic performance. It is found that 33% CeO2-CaO DFM displayed approximately 49% CO2 conversion and approximately 100% CO selectivity in integrated CO2 capture and reverse water-gas shift reaction (ICCU-RWGS) at 650°C, while CaO-alone only achieved approximately 20% CO2 conversion at the same condition. The surface basicity of CeO2 is revealed to contribute to the improved catalytic performance by enhancing CO2 chemisorption and activation in the hydrogenation step. Furthermore, CeO2-CaO material possessed excellent cycle stability in 20 cycles ICCU-RWGS, achieving a sustainable and high-efficient performance in CO2 conversion and CO selectivity.

Removal of antimonite (Sb(III)) from aqueous solution using a magnetic iron-modified carbon nanotubes (CNTs) composite: Experimental observations and governing mechanisms.

In this study, a novel nanoscale iron oxide (FeOx) modified carbon nanotubes composite (FeOx@CNTs) was synthesized through a combined ball milling-hydrothermal two-step method and tested for aqueous Sb(III) removal efficiency and mechanisms. FeOx nanoparticles was successfully loaded on the surface of CNTs through functional groups such as hydroxyl (-OH), C-H, and C-O to enhance the removal efficiency of Sb(III) through adsorption and surface complexation. At a dosage of 0.02 g, a FeCl3·6H2O-to-CNTs mass ratio of 3:1, and an initial solution pH of 6.3, the amount of Sb(III) removed by the prepared FeOx@CNTs reached 172 mg/g, which was 42.9 times higher than that of the pristine CNTs (4.01 mg/g). Chemical adsorption and oxidation were the main removal mechanisms. At the equilibrium Sb(III) concentration of 6.08 mg/L, 6.56% of initial Sb(III) was adsorbed onto the surface of FeOx@CNTs, and 81.3% of initial Sb(III) was oxidized to Sb(V) with lower toxicity. The pseudo-second-order kinetic model could better describe the adsorption of Sb(III) onto the FeOx@CNTs composite, indicating that adsorption was mainly controlled by chemical sorption. In the adsorption isotherm equation, the Redlich-Peterson model provided a better fit of Sb(III) adsorption onto the FeOx@CNTs composite than the Langmuir and Freundlich models, which further indicated that the adsorption process was a hybrid removal process dominated by chemical sorption. The presence of CO32- slightly promoted the removal of Sb(III) from aqueous solution. The synthesized composite was magnetic and could be easily separated from the solution by an external magnetic field at the end of the sorption experiment. Based on these findings, the FeOx@CNTs nanocomposite is expected to provide an environmentally-friendly adsorbent with a strong sorption capacity for remediating Sb(III) in water environments.

Combination BET Family Protein and HDAC Inhibition Synergistically Elicits Chondrosarcoma Cell Apoptosis Through RAD51-Related DNA Damage Repair.

BACKGROUND: Chondrosarcoma is the second-most common type of bone tumor and has inherent resistance to conventional chemotherapy. Present study aimed to explore the therapeutic effect and specific mechanism(s) of combination BET family protein and HDAC inhibition in chondrosarcoma. METHODS: Two chondrosarcoma cells were treated with BET family protein inhibitor (JQ1) and histone deacetylase inhibitors (HDACIs) (vorinostat/SAHA or panobinostat/PANO) separately or in combination; then, the cell viability was determined by Cell Counting Kit-8 (CCK-8) assay, and the combination index (CI) was calculated by the Chou method; cell proliferation was evaluated by 5-ethynyl-2'-deoxyuridine (EdU) incorporation and colony formation assay; cell apoptosis and reactive oxygen species (ROS) level were determined by flow cytometry; protein expressions of caspase-3, Bcl-XL, Bcl-2, γ-H2AX, and RAD51 were examined by Immunoblotting; DNA damage was determined by comet assay; RAD51 and γ-H2AX foci were observed by immunofluorescence. RESULTS: Combined treatment with JQ1 and SAHA or PANO synergistically suppressed the growth and colony formation ability of the chondrosarcoma cells. Combined BET and HDAC inhibition also significantly elevated the ROS level, followed by the activation of cleaved-caspase-3, and the downregulation of Bcl-2 and Bcl-XL. Mechanistically, combination treatment with JQ1 and SAHA caused numerous DNA double-strand breaks (DSBs), as evidenced by the comet assay. The increase in γ-H2AX expression and foci formation also consistently indicated the accumulation of DNA damage upon cotreatment with JQ1 and SAHA. Furthermore, RAD51, a key protein of homologous recombination (HR) DNA repair, was found to be profoundly suppressed. In contrast, ectopic expression of RAD51 partially rescued SW 1353 cell apoptosis by inhibiting the expression of cleaved-caspase-3. CONCLUSION: Taken together, our results disclose that BET and HDAC inhibition synergistically inhibit cell growth and induce cell apoptosis through a mechanism that involves the suppression of RAD51-related HR DNA repair in chondrosarcoma cells.

Pyrolysis-catalysis of waste plastic using a nickel-stainless-steel mesh catalyst for high-value carbon products.

A stainless-steel mesh loaded with nickel catalyst was produced and used for the pyrolysis-catalysis of waste high-density polyethylene with the aim of producing high-value carbon products, including carbon nanotubes (CNTs). The catalysis temperature and plastic-to-catalyst ratio were investigated to determine the influence on the formation of different types of carbon deposited on the nickel-stainless-steel mesh catalyst. Increasing temperature from 700 to 900°C resulted in an increase in the carbon deposited on the nickel-loaded stainless-steel mesh catalyst from 32.5 to 38.0 wt%. The increase in sample-to-catalyst ratio reduced the amount of carbon deposited on the mesh catalyst in terms of g carbon g-1 plastic. The carbons were found to be largely composed of filamentous carbons, with negligible disordered (amorphous) carbons. Transmission electron microscopy analysis of the filamentous carbons revealed them to be composed of a large proportion (estimated at ∼40%) multi-walled carbon nanotubes (MWCNTs). The optimum process conditions for CNT production, in terms of yield and graphitic nature, determined by Raman spectroscopy, was catalysis temperature of 800°C and plastic-to-catalyst ratio of 1:2, where a mass of 334 mg of filamentous/MWCNTs g-1 plastic was produced.