Flash Recycling of Graphite Anodes.

The ever-increasing production of commercial lithium-ion batteries (LIBs) will result in a staggering accumulation of waste when they reach their end of life. A closed-loop solution, with effective recycling of spent LIBs, will lessen both the environmental impacts and economic cost of their use. Presently, <5% of spent LIBs are recycled and the regeneration of graphite anodes has, unfortunately, been mostly overlooked despite the considerable cost of battery-grade graphite. Here, an ultrafast flash recycling method to regenerate the graphite anode is developed and valuable battery metal resources are recovered. Selective Joule heating is applied for only seconds to efficiently decompose the resistive impurities. The generated inorganic salts, including lithium, cobalt, nickel, and manganese, can be easily recollected from the flashed anode waste using diluted acid, specifically 0.1 m HCl. The flash-recycled anode preserves the graphite structure and is coated with a solid-electrolyte-interphase-derived carbon shell, contributing to high initial specific capacity, superior rate performance, and cycling stability, when compared to anode materials recycled using a high-temperature-calcination method. Life-cycle-analysis relative to current graphite production and recycling methods indicate that flash recycling can significantly reduce the total energy consumption and greenhouse gas emission while turning anode recycling into an economically advantageous process.

Holey and Wrinkled Flash Graphene from Mixed Plastic Waste.

High surface area varieties of graphene have captured significant attention, allowing for improved performance in a variety of applications. However, there are challenges facing the use of graphene in these applications since it is expensive and difficult to synthesize in bulk. Here, we leverage the capabilities of flash Joule heating to synthesize holey and wrinkled flash graphene (HWFG) in seconds from mixed plastic waste feedstocks, using in situ salt decomposition to produce and stabilize pore formation during the reaction. Surface areas as high as 874 m2 g-1 are obtained, with characteristics of micro-, meso-, and macroporosities. Raman spectroscopy confirms the wrinkled and turbostratic nature of the HWFG. We demonstrate HWFG applications in its use as a metal-free hydrogen evolution reaction electrocatalyst, with excellent stability, competitive overpotential, and Tafel slope; in a Li-metal battery anode allowing for stable and high discharge rates; and in a material with high gas adsorption. This represents an upcycle of mixed plastic waste, thereby affording a valuable route to address this pressing environmental pollutant concern.

Plastic Waste Product Captures Carbon Dioxide in Nanometer Pores.

Plastic waste (PW) and increasing atmospheric carbon dioxide (CO2) levels are among the top environmental concerns presently facing humankind. With an ambitious 2050 zero-CO2 emissions goal, there is a demand for economical CO2 capture routes. Here we show that the thermal treatment of PW in the presence of potassium acetate yields an effective carbon sorbent with pores width of 0.7-1.4 nm for CO2 capture. The PW to carbon sorbent process works with single or mixed streams of polyolefin plastics. The CO2 capacity of the sorbent at 25 °C is 17.0 ± 1.1 wt % (3.80 ± 0.25 mmol g-1) at 1 bar and 5.0 ± 0.6 wt % (1.13 ± 0.13 mmol g-1) at 0.15 bar, and it regenerates upon reaching 75 ± 5 °C. The CO2 capture cost from flue gas via this technology is estimated to be <$21 ton-1 CO2, much lower than competing CO2 capture technologies. Hence, this PW-derived carbon material should find utility in the capture of CO2 from point sources of high CO2 emissions while providing a use for otherwise deleterious PW.

Flash Graphene from Plastic Waste.

In this work, an approach to upcycling plastic waste (PW) products is presented. The method relies on flash Joule heating (FJH) to convert PW into flash graphene (FG). In addition to FG, the process results in the formation of carbon oligomers, hydrogen, and light hydrocarbons. In order to make high-quality graphene, a sequential alternating current (AC) and direct current (DC) flash is used. The FJH process requires no catalyst and works for PW mixtures, which makes the process suitable for handling landfill PW. The energy required to convert PW to FG is ∼23 kJ/g or ∼$125 in electricity per ton of PW, potentially making this process economically attractive for scale-up. The FG was characterized by Raman spectroscopy and had an I2D/IG peak ratio up to 6 with a low-intensity D band. Moreover, transmission electron microscopy and X-ray diffraction analysis show that the FG is turbostratic with an interlayer spacing of 3.45 Å. The large interlayer spacing will facilitate its dispersion in liquids and composites. Analysis of FG dispersions in 1% Pluronic aqueous solution shows that concentrations up to 1.2 mg/mL can be achieved. The carbon oligomers that distilled from the process were characterized by Fourier transform infrared spectroscopy and have chemical structures similar to the starting PW. Initial analysis of gas-phase products shows the formation of considerable amounts of hydrogen along with other light hydrocarbons. As graphene is naturally occurring and shows a low toxicity profile, this could be an environmentally beneficial method to upcycle PW.

A critical analysis of the literature regarding surgical approach and outcome for adult low-grade isthmic spondylolisthesis.

OBJECTIVE: A systematic review of the radiographic and clinical outcomes of adult patients undergoing surgery for low-grade isthmic spondylolisthesis was performed to determine whether conclusions could be made regarding the optimal choice of surgically managing adult low-grade isthmic spondylolisthesis. METHODS: We tabulated the radiographic and clinical outcomes of patients who underwent a posterior procedure alone, an anterior procedure alone, or a combined anterior and posterior procedure. We also evaluated the influence of covariates such as laminectomy, spinal internal fixation, smoking, and secondary gain issues on these outcomes. Patients were pooled, and a chi analysis was performed to determine the relationship between surgical approach and patient outcome. A covariate analysis was performed to determine the influence of a laminectomy, spinal fixation, smoking, and secondary gain issues on these outcomes. RESULTS: The available literature consisted primarily of retrospective case series, with only 4 of 34 reports being prospective randomized controlled studies. Patients with combined anterior and posterior procedures were most likely to achieve a solid fusion and a successful clinical outcome. The use of spinal fixation also increased the chance of fusion and successful clinical outcome. CONCLUSIONS: A pooling of the surgical literature on adult low-grade spondylolisthesis indicates that a combined anterior and posterior procedure most reliably achieves fusion and a successful clinical outcome. The literature, however, is primarily retrospective and heterogeneous with respect to indications for surgery and methods of evaluating outcome, providing a compelling rationale for a prospective randomized controlled trial of the various surgical approaches to this problem.

Transforaminal lumbar interbody fusion: the effect of various instrumentation techniques on the flexibility of the lumbar spine.

STUDY DESIGN: In vitro comparison of four reconstruction techniques following transforaminal lumbar interbody fusion in a human cadaveric model. INTRODUCTION: Transforaminal lumbar interbody fusion (TLIF) is a relatively new technique that avoids the morbidity of an anterior approach and the nerve root manipulation of a posterior interbody fusion. This study measured the effects of a TLIF on the overall and segmental flexibility of the lumbar spine using four different spinal implant configurations. SUMMARY OF BACKGROUND DATA: Anterior lumbar interbody fusion, posterior lumbar interbody fusion, and combined anterior-posterior spinal procedures are gaining wide acceptance for the treatment of selected patients with segmental spinal instability and spondylolisthesis with associated degenerative changes. Each fusion technique may have different effects on the overall flexibility of the lumbar spine. The unilateral TLIF procedure with adjunctive pedicular fixation is one variation of an interbody fusion technique that requires less bony and soft tissue dissection and minimizes nerve root manipulation compared with other interbody fusion methods. METHODS: Five fresh-frozen, human lumbar spines were nondestructively subjected to flexion, extension, lateral bending, and axial rotation moments using a previously validated spine flexibility tester, and displacements were measured. Testing the intact lumbar spine was followed by testing of a unilateral L4-L5 TLIF using a single ramp carbon fiber cage without adjunctive internal fixation. The single carbon fiber (Brantigan) cage was inserted obliquely in a posterolateral to anteromedial position in the L4-L5 disc space. Following testing of the cage alone, three different adjunctive stabilization techniques were tested. Posterior stabilization involved one of the following: a contralateral translaminar facet screw, single side/ipsilateral nonsegmental pedicle screw fixation, and bilateral nonsegmental pedicle screw fixation. The overall flexibility of each lumbar spine was calculated from load-displacement curves for each axis of rotation. The flexibility of the L4-L5 segment of each spine was computed from kinematic motion data acquired via attached LED sensors to the L4 and L5 vertebral bodies. Statistical testing was performed with paired t tests. RESULTS: The flexibility of the entire (T12-S1) destabilized spine after TLIF with interbody cage alone and with all three reconstructive techniques was comparable with the intact spine. However, the motion at the L4-L5 segment was significantly increased for the TLIF with interbody cage alone in axial rotation (299% of intact, P < 0.01), with no significant change in flexion-extension (79% of intact, P = 0.22) or lateral bending (87% of intact, P = 0.39). With the addition of a contralateral translaminar facet screw, the motion at the L4-L5 segment remained significantly more flexible in axial rotation (250% of intact, P = 0.06) although less than with the cage alone. With the unilateral pedicle screw construct, the L4-L5 segment remained more flexible in axial rotation (182% of intact, P = 0.07) although significantly less than with the facet screw construct (P < 0.05). The addition of bilateral pedicle screws most closely reapproximated the flexibility of the intact spine with no significant difference in axial rotation (91% of intact, P = 0.30), flexion-extension (93% of intact, P = 0.19), or lateral bending (99% of intact, P = 0.47). The motion at the L4-L5 segment with bilateral pedicle screws was not significantly different than for the intact specimen in axial rotation (144% of intact, P = 0.17), flexion-extension (81% of intact, P = 0.21), or lateral bending (86% of intact, P = 0.27). CONCLUSIONS: TLIF reconstruction with a solitary cage did not increase overall spine flexibility from the intact condition but significantly increased segmental flexibility at L4-L5 in axial rotation. A unilateral translaminar facet screw had minimal stabilizing effect at L4-L5. Unilateral pedicle screws frews further increased stiffness at the L4-L5 segment. However, TLIF with bilateral pedicle screws most closely approximated the L4-L5 segmental flexibility of the intact spine.