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.

Effect of type of activating agent on properties of activated carbon prepared from digested solid waste.

Anaerobic digestion has been proved to be a widely used and effective technology. The main challenge for the sustainable biogas industry is to find ways to efficiently recycle and utilize the anaerobic digestate. The conversion of digestion products into activated carbon seems to be an attractive way. Therefore, the present study focused on assessing the potential of digested solids as a promising source of activated carbon using a range of activators including KOH, ZnCl2 and H3PO4. The activated carbon prepared from digested solids was subjected to an activation process to investigate the physicochemical and surface properties of the resulting activated carbon. The results showed that KOH appeared to be the best activator for producing activated carbon from high silica precursors such as digested solids. The effectiveness of KOH activation can be attributed to the ability of K to readily form poorly layered compounds with carbon, as well as a significant increase in the number of porosities during KOH activation due to the violent reaction of KOH with C and the volatilization of the inorganic minerals in the digested char. The KOH activated sample had the lowest La and Lc, which means it had the theoretically largest specific surface area. This study provides experimental basis and theoretical guidance for the conversion of digested solids into high value-added activated carbon.

Thermodynamic modelling of integrated carbon capture and utilisation process with CaO-based sorbents in a fixed-bed reactor.

The global emission of CO2 through fossil fuel combustion is still increasing, which is a major challenge for the international community. An integrated carbon capture and utilisation (ICCU) process with a CaO-based sorbent is a promising alternative to effectively reduce emissions. In this work, a comparative thermodynamic analysis of two CaO-based sorbents (commercial and sol-gel CaO) was performed for one cycle of ICCU. In addition, the influence of temperature was investigated from 600 to 750 °C in terms of the degree of CO2 conversion. Thermodynamic calculations were based on the actual gas composition and developed model, where heat consumption and entropy generation were calculated. The results indicate that the degree of CO2 conversion decreased from 84.6 to 41.2% and from 84.1 to 62.4% for the sol-gel and commercial material, respectively, as the temperatures increased. Furthermore, the total heat consumption during one cycle decreased with higher temperatures. The total amount of consumed heat decreased from 19.1 to 5.9 kJ/g and from 24.7 to 5.4 kJ/g for sol-gel and commercial CaO, respectively. Although commercial CaO always requires more heat during one cycle. Moreover, for both materials, the lowest generation of entropy was calculated at 650 °C with values of 9.5 and 10.1 J/g·K for the sol-gel and the commercial CaO, respectively. At all temperatures, the commercial CaO generated a greater entropy.

Light Triggered Pore Size Tuning in Photoswitching Covalent Triazine Frameworks for Low Energy CO2 Capture.

Recently, photo switching porous materials have been widely reported for low energy costed CO2 capture and release via simply remoted light controlling method. However, most reported photo responsive CO2 adsorbents relied on metal organic framework (MOFs) functionalisation with photochromic moieties, and MOF adsorbents still suffered from chemically and thermally unstable issues. Thus, further metal free and highly stable organic photoresponsive adsorbents are necessary to be developed. CTFs, because of their high porosity and stability, have attracted great attention for CO2 capture. Considering the high CO2 uptake capacity and structural tunability of CTFs, it suggests high potential to fabricate the photoswitching CTF materials by the same functionalisation method as MOFs. Herein, the first series of photo switching CTFs were developed for low energy CO2 capture and release. Apart from that, the CO2 switching efficiency could be doubled either through the azobenzene numbers adjusting method or through the previously reported structural alleviation strategy. Furthermore, the pore size distribution of azobenzene functionalised PCTFs also could be tuned under UV exposure, which may contribute to the UV light induced decrease of CO2 uptake capacity. These photoswitching CTFs represented a new kind of porous polymers for low energy costed CO2 capture.

Autothermal CaO Looping Biomass Gasification for Renewable Syngas Production.

Biomass gasification is regarded as a promising alternative to fossil fuels for producing sustainable and clean value-added products. However, the challenges including low energy efficiency, CO2 emission, and ash agglomeration significantly delay the deployment of the technology. Herein, we first proposed a novel autothermal CaO looping biomass gasification (Auto-CaL-Gas) technology, in which CaO-based materials react with flue gas with a high concentration of CO2 (>30 vol %) to produce heat inside the gasifier, simultaneously providing energy for low-temperature biomass gasification using CO2 as a gasification agent. Upon use of this concept the syngas production exhibited a significant increase from 0.21 kg/h to 0.90 kg/h in the Aspen simulation results and more than 3-fold improvement in the experimental results.

One-Step Reforming of CO2 and CH4 into High-Value Liquid Chemicals and Fuels at Room Temperature by Plasma-Driven Catalysis.

The conversion of CO2 with CH4 into liquid fuels and chemicals in a single-step catalytic process that bypasses the production of syngas remains a challenge. In this study, liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one-step process from CO2 and CH4 at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50-60 %, with acetic acid being the major component at 40.2 % selectivity, the highest value reported for acetic acid thus far. Interestingly, the direct plasma synthesis of acetic acid from CH4 and CO2 is an ideal reaction with 100 % atom economy, but it is almost impossible by thermal catalysis owing to the significant thermodynamic barrier. The combination of plasma and catalyst in this process shows great potential for manipulating the distribution of liquid chemical products in a given process.

Processing real-world waste plastics by pyrolysis-reforming for hydrogen and high-value carbon nanotubes.

Producing both hydrogen and high-value carbon nanotubes (CNTs) derived from waste plastics is reported here using a pyrolysis-reforming technology comprising a two-stage reaction system, in the presence of steam and a Ni-Mn-Al catalyst. The waste plastics consisted of plastics from a motor oil container (MOC), commercial waste high density polyethylene (HDPE) and regranulated HDPE waste containing polyvinyl chloride (PVC). The results show that hydrogen can be produced from the pyrolysis-reforming process, but also carbon nanotubes are formed on the catalyst. However, the content of 0.3 wt.% polyvinyl chloride in the waste HDPE (HDPE/PVC) has been shown to poison the catalyst and significantly reduce the quantity and purity of CNTs. The presence of sulfur has shown less influence on the production of CNTs in terms of quantity and CNT morphologies. Around 94.4 mmol H2 g(-1) plastic was obtained for the pyrolysis-reforming of HDPE waste in the presence of the Ni-Mn-Al catalyst and steam at a reforming temperature of 800 °C. The addition of steam in the process results in an increase of hydrogen production and reduction of carbon yield; in addition, the defects of CNTs, for example, edge dislocations were found to be increased with the introduction of steam (from Raman analysis).

Plastic wastes-derived N-doped carbon nanotubes for efficient removal of sulfamethoxazole in high salinity wastewater via nonradical peroxymonosulfate activation.

Peroxymonosulfate (PMS) catalytic activation is effective to eliminate organic pollutants from water, thus the development of low-cost and efficient catalysts is significant in applications. The resource conversion of plastic wastes (PWs) into carbon nanotubes (CNTs) is a promising candidate for PMS-based advanced oxidation processes (AOPs), and also a sustainable strategy to realize plastic management and reutilization. Herein, cost-effective PWs-derived N-doped CNTs (N-pCNTs) were synthesized, which displayed efficient activity for PMS activation through an electron transfer pathway (ETP) for sulfamethoxazole (SMX) degradation in high salinity water. The pyrrolic N induced the positively charged surface of N-pCNTs, favoring the electrostatic adsorption of PMS and subsequent generation of active PMS* . A galvanic oxidation process was developed to prove the electron-shuttle dominated ETP for SMX oxidation. Combined with theoretical calculations, the efficiency of ETP was determined by the potential difference between HOMO of SMX and LUMO of N-pCNTs. Such oxidation produced low-toxicity intermediates and resulted in selective degradation of specific sulfonamide antibiotics. This work reveals the feasibility of low-cost N-pCNTs catalysts from PWs serving as an appealing candidate for PMS-AOPs in water remediation, providing a new solution to alleviate environmental issues caused by PWs and also advances the understanding of ETP during PMS activation.

Tuning the electronic metal-carbon interactions in Lignin-based carbon-supported ruthenium-based electrocatalysts for enhanced hydrogen evolution reactions.

Ruthenium (Ru) nanoparticles dispersed on carbon support are promising electrocatalysts for hydrogen evolution reaction (HER) due to strong electronic metal-carbon interactions (EMCIs). Defects engineering in carbon supports is an effective strategy to adjust EMCIs. We prepared nitrogen/sulfur co-doped carbon supported Ru nanoparticles (Ru@N/S-LC) using sodium lignosulfonate and urea as feedstocks. Intrinsic S dopants from sodium lignosulfonate create rich S defects, thus enhancing the EMCIs within Ru@N/S-LC, leading a faster electron transfer between Ru nanoparticles and N/S-LC compared with N-doped carbon supported Ru nanoparticles (Ru@N-CC). The resulting Ru@N/S-LC exhibits an enhanced work function and a down-shifted d-band center, inducing stronger electron capturing ability and weaker hydrogen desorption energy than Ru@N-CC. Ru@N/S-LC requires only 7 and 94 mV overpotential in acidic medium and alkaline medium to achieve a current density of 10 mA cm-2. Density Functional Theory (DFT) calculations were utilized to clarify the impact of sulfur (S) doping and the mechanism underlying the notable catalytic activity of Ru@N/S-LC. This study offers a perspective for utilizing the natural dopants of biomass to adjust the EMCIs for electrocatalysts.

Potassium-Promoted Limestone for Preferential Direct Hydrogenation of Carbonates in Integrated CO2 Capture and Utilization.

Integrated CO2 capture and utilization (ICCU) via the reverse water-gas shift (RWGS) reaction offers a particularly promising route for converting diluted CO2 into CO using renewable H2. Current ICCU-RWGS processes typically involve a gas-gas catalytic reaction whose efficiency is inherently limited by the Le Chatelier principle and side reactions. Here, we show a highly efficient ICCU process based on gas-solid carbonate hydrogenation using K promoted CaO (K-CaO) as a dual functional sorbent and catalyst. Importantly, this material allows ∼100% CO2 capture efficiency during carbonation and bypasses the thermodynamic limitations of conventional gas-phase catalytic processes in hydrogenation of ICCU, achieving >95% CO2-to-CO conversion with ∼100% selectivity. We showed that the excellent functionalities of the K-CaO materials arose from the formation of K2Ca(CO3)2 bicarbonates with septal K2CO3 and CaCO3 layers, which preferentially undergo a direct gas-solid phase carbonates hydrogenation leading to the formation of CO, K2CO3 CaO and H2O. This work highlights the immediate potential of K-CaO as a class of dual-functional material for highly efficient ICCU and provides a new rationale for designing functional materials that could benefit the real-life application of ICCU processes.

Phosphorus Removal from Dirty Farmyard Water by Activated Anaerobic-Digestion-Derived Biochar.

The management of anaerobic digestate is important to realize the value of the waste and enhance the whole system sustainability of anaerobic digestion. In this study, the phosphorus treatment of dirty irrigation water by biochar samples derived from digestate of anaerobic digestion were investigated. The biochars were further activated by steam activation with different duration time and KOH activation with different introducing ratios; the textural properties of biochars were optimized after activation from the aspect of biochar characterization. Notably, AD-N2 demonstrates a remarkable adsorption effect of phosphorus, with an adsorption efficiency of 8.99 mg g-1. Besides the effect of biochar dosage on phosphorus removal, adsorption kinetics and thermodynamic isotherms are studied. According to the adsorption kinetics, the adsorption of phosphorus from dirty water fits the Elovich equation (R2 = 0.95). Furthermore, the thermodynamic isotherm results illustrate the process of phosphorus removal by biochar is endothermic (ΔH0 = 17.93 kJ mol-1) and spontaneous (ΔS = 96.24 J mol-1 K-1). Therefore, this work suggests a promising solution to phosphorus-related environmental challenges in industry and agriculture.

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.

The Application of Biochar for CO2 Capture: Influence of Biochar Preparation and CO2 Capture Reactors.

This work investigates three types of biochar (bamboo charcoal, wood pellet, and coconut shell) for postcombustion carbon capture. Each biochar is structurally modified through physical (H2O, CO2) and chemical (ZnCl2, KOH, H3PO4) activation to improve carbon capture performance. Three methods (CO2 adsorption isotherms, CO2 fixed-bed adsorption, and thermogravimetric analysis) are used to determine the CO2 adsorption capacity. The results show that a more than 2.35 mmol·g-1 (1 bar, 298 K) CO2 capture capacity was achieved using the activated biochar samples. It is also demonstrated that the CO2 capture performance by biochar depends on multiple surface and textural properties. A high surface area and pore volume of biochar resulted in an enhanced CO2 capture capacity. Furthermore, the O*/C ratio and pore width show a negative correlation with the CO2 capture capacity of biochars.

Efficient microwave-assisted mineralization of oxytetracycline driven by persulfate and hypochlorite over Cu-biochar catalyst.

Microwave (MW)-assisted catalytic degradation of organic pollutants draws increasing attention owing to its high efficiency in wastewater treatment. This work developed Cu-loaded biochar (CuBC) catalysts for time-efficient mineralization of refractory and high-concentration oxytetracycline (OTC). With only 1 min at 80 °C, Na2S2O8 achieved 100% total organic carbon (TOC) removal over the Cu5BC, while NaClO mineralized 73.3% TOC over the metal-free BC, in contrast to a relatively low mineralization efficiency (< 35%) achieved by H2O2. The high efficiency in MW-assisted oxidation systems could be ascribed to reactive oxidizing species (•SO4- or •ClO), which otherwise were barely detectable in a conventional heating system. The interactions between CuBC and MW were revealed by correlating the physiochemical characteristics to the MW absorption ability. The proposed catalytic systems can contribute to the development of a high-throughput and low-carbon wastewater treatment technology.

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%.

General approach to surface-accessible plasmonic Pickering emulsions for SERS sensing and interfacial catalysis.

Pickering emulsions represent an important class of functional materials with potential applications in sustainability and healthcare. Currently, the synthesis of Pickering emulsions relies heavily on the use of strongly adsorbing molecular modifiers to tune the surface chemistry of the nanoparticle constituents. This approach is inconvenient and potentially a dead-end for many applications since the adsorbed modifiers prevent interactions between the functional nanosurface and its surroundings. Here, we demonstrate a general modifier-free approach to construct Pickering emulsions by using a combination of stabilizer particles, which stabilize the emulsion droplet, and a second population of unmodified functional particles that sit alongside the stabilizers at the interface. Freeing Pickering emulsions from chemical modifiers unlocks their potential across a range of applications including plasmonic sensing and interfacial catalysis that have previously been challenging to achieve. More broadly, this strategy provides an approach to the development of surface-accessible nanomaterials with enhanced and/or additional properties from a wide range of nano-building blocks including organic nanocrystals, carbonaceous materials, metals and oxides.

The improvement of agronomic performances in the cold weather conditions for perennial wheatgrass by crossing Thinopyrum intermedium with wheat-Th. intermedium partial amphiploids.

Thinopyrum intermedium (2n=6x=42, StStJrJrJvsJvs) is resistant or tolerant to biotic and abiotic stresses, making it suitable for developing perennial crops and forage. Through five cycles of selection, we developed 24 perennial wheatgrass lines, designated 19HSC-Q and 20HSC-Z, by crossing wheat-Th. intermedium partial amphiploids with Th. intermedium. The cold resistance, morphological performance, chromosome composition, and yield components of these perennial lines were investigated from 2019 to 2022. Six lines of 19HSC-Q had higher 1,000-kernel weight, grains per spike, and tiller number than Th. intermedium, as well as surviving -30°C in winter. Lines 19HSC-Q14, 19HSC-Q18, and 19HSC-Q20 had the best performances for grain number per spike and 1,000-kernel weight. The 20HSC-Z lines, 20HSC-Z1, 20HSC-Z2, and 20HSC-Z3, were able to survive in the cold winter in Harbin and had been grown for two years. Sequential multicolor GISH analysis revealed that the Jvs subgenome of Th. intermedium were divided into two karyotypes, three pairs of type-I Jvs chromosomes and four pairs of type-II Jvs chromosomes. Both Th. intermedium and the 24 advanced perennial wheatgrass lines had similar chromosome compositions, but the translocations among subgenome chromosomes were detected in some lines with prominent agronomic traits, such as 19HSC-Q11, 19HSC-Q14, 19HSC-Q18, 19HSC-Q20, and the three 20HSC-Z lines. The chromosome aberrations were distinguished into two types: the large fragment translocation with St-Jr, Jvs-St, Jr-IIJvs, and Jvs-Jr and the small fragment introgression of Jr-St, St-IJvs, and Jvs-Jr. These chromosomal variations can be used to further analyze the relationship between the subgenomes and phenotypes of Th. intermedium. The results of this study provide valuable materials for the next selection cycle of cold-resistant perennial wheatgrass.

Application of Carbon Nanotubes from Waste Plastics As Filler to Epoxy Resin Composite.

Carbon nanotubes (CNTs) are promising nanofillers to enhance the mechanical performance of polymers. Through catalytic conversion, waste plastics can be converted into CNTs, which could be an alternative to commercial CNTs (cCNTs). Exploring a practical application of waste-plastic-derived CNTs will largely promote the technology development related to waste plastic management and CNT production. In this work, CNTs produced from plastics, named pCNTs, were applied as fillers to epoxy resin (EP), while commercial CNTs (cCNTs) were used as a reference. The carboxyl groups were effectively inserted on the CNT skeleton by a facile purification and modification. After ultrasonic dispersion, the modified pCNTs (M-pCNTs) were uniformly dispersed and loaded in the EP matrix. Better mechanical properties than EP were attained with a Young's modulus of 3776.9 MPa, a tensile strength of 37.3 MPa, a fracture strain of 6.32%, and a fracture strength of 111.7 MPa with 2 wt % M-pCNT loading. Thus, pCNTs enhanced the toughness of the EP composites and simultaneously retained the stiffness. It was suggested that CNT pull-out and bridging were predominant toughening mechanisms for pCNT/EP composites. Notably, the coated film developed between residual metal in M-pCNTs and EP built a strong interfacial interaction and reinforced the EP composites.

[Efficacy of percutaneous short segment fixation in the treatment of Magerl A3 thoracolumbar fractures with low bone mineral density:a retrospective study].

OBJECTIVE: To explore the clinical efficacy of percutaneous pedicle screw short segment internal fixation with or without the intermediate screw in the treatment of Magerl A3 thoracolumbar fractures with low bone mineral density. METHODS: Patients with Magerl A3 thoracolumbar fracture underwent percutaneous pedicle screw short segment internal fixation from January 2017 to July 2020 were retrospectively analyzed, 93 cases met the diagnosis and inclusion criteria, 9 cases were excluded according to the exclusion criteria, and the remaining 84 cases obtained complete imaging follow-up data. There were 38 males and 46 females, the age ranged from 56 to 73 years old with an average of (64.78±7.12) years old, bone mineral density (BMD) ranged from 0.61 to 0.89 g/cm3 with an average of (0.73±0.14) g/cm3, the follow-up time was 11 to 25 months with an average of (17.58±6.12) months. There were 45 cases in group A with intermediate screw and 39 cases in group B without intermediate screw. The operation time and intraoperative blood loss were recorded, Oswestry Disability Index (ODI) and visual analogue scale (VAS) were used for clinical evaluation. The Cobb angle, vertebral wedge angle (VWA) and anterior vertebral body height (AVBH) were measured by X-ray after the operation. The corrected loss of the above parameters was calculated. RESULTS: There were 5 cases of screw loosening in 84 patients (2 cases in group A and 3 cases in group B, P>0.05). There were significant differences in operation time and intraoperative blood loss between two groups(P<0.01). Clinical effects of two groups were good, postoperative VAS and ODI after operation obviously improved, there was no significant difference between two groups during all follow-up periods (3 days, 1 month after operation and the final follow-up) (P>0.05). Three days after the operation, the image evaluations (Cobb angle, VWA and AVBH) were significantly improved (P<0.05), but significant reduction loss was observed in both groups at 1 month after the operation and at the final follow-up (P<0.05). At the final follow-up, the loss of Cobb angle, VWA and AVBH in group A were (5.26±4.18) °, (4.63±3.80) ° and (9.54±8.71)%, respectively;group B was (6.01±4.34) °, (6.55±6.21) ° and (11.67± 9.95)%, respectively;however, there was no significant difference in reduction loss between the two groups(P>0.05). CONCLUSION: Although the curative effect of the patients is satisfactory, the stability of the patients can not be improved by increasing the middle injured vertebra screw placement, the two groups of percutaneous short segment internal fixation can not resist the reduction loss of Magerl-A3 thoracolumbar fracture with low bone mineral density. Because the injured vertebra screw increases the operation time and intraoperative blood loss, it is not significant to use the intermediate screw for the elderly Magerl A3 thoracolumbar fractures with low bone mineral density.