Low-temperature Pyrolysis Process Research Articles

3D-printed indium oxide monoliths for PFAS removal

More efficient removal methods for per- and polyfluoroalkyl substances (PFAS), anthropogenic compounds with high persistence in the environment, are urgently needed due to their significant adverse health effects. Current technologies for PFAS removal in water are limited by incomplete degradation or practical concerns about the use of slurry-based adsorbents. In this study, self-supported indium oxide (In2O3) monoliths were produced via extrusion-based 3D printing and used for the removal of perfluorooctanoic acid (PFOA) via adsorption in a recirculating flow system. A detailed study of the sintering temperature, monolith geometry, and flow rate allowed maximising PFOA adsorption due to the improvement of PFOA diffusion and the increased number of active sites on the monolith, resulting in 53 % of PFOA removal with fast adsorption kinetics in 3 h. Additionally, a low-temperature pyrolysis process at 500 °C effectively regenerated the In2O3 monoliths, allowing reusing the monoliths for three adsorption cycles, while also improving the PFOA removal to 75 % in 3 h. The regenerated In2O3 monoliths not only have a high adsorption capacity (0.16 mg g−1), but also required a much shorter time to reach the adsorption equilibrium compared with other adsorbents reported in the literature. The effectiveness, robustness and reusability of the 3D printed In2O3 monoliths highlight their potential as an efficient and sustainable adsorbent for PFAS removal. The approach presented here represents an effective strategy for the fabrication of complex adsorbents, which are reusable and can be easily handled, eliminating the expensive downstream removal required for slurries while offering a clear route for scale-up towards industrial use.

Preparation of Al-doped carbon materials derived from artificial potassium humate prepared from waste cotton cloth and their excellent Cr(VI) adsorption performance

Millions of tons of cotton textile waste are generated annually worldwide, and most of it enters the municipal solid waste (MSW) stream for landfill or incineration disposal, resulting in a significant waste of resources and environmental pollution. This article developed an innovative low-temperature pyrolysis process for producing artificial humic acid (HA) from waste cotton textiles. Subsequently, Al3+ was introduced for a secondary pyrolysis to prepare an Al-doped biochar (Al/BC) with superior adsorption properties. The experimental results show that the presence of Al3+ has an important influence on the pyrolysis process of cotton fabric and the formation and structure of Al/BC. This is the first time to synthesize low-cost adsorbent by pyrolysis and aluminum mixing process of waste cotton cloth and explains the mechanism. This increased in defects (ID/IG = 0.76 to ID/IG = 0.92), a larger specific surface area (6.47 m2/g to 566.94 m2/g), and an increase in oxygen-containing functional groups (from none to C-O-C, OC-O, etc.) when compared to the undoped Al3+ biochar. The optimum Al3+-doped biochar (Al/BC-15) prepared with HA as a precursor exhibited a superior adsorption capacity for Cr(VI) of up to 176.23 mg/g, surpassing the results reported for similar materials in the literature. The adsorption mechanism of Cr(VI) is primarily based on physical adsorption, with some chemical adsorption. At a lower pH, the Al/BC-15 surface exhibits a high positive charge (46 mV). The Al3+-O-Cr(VI) association group is formed through rapid electrostatic attraction between C-Al and Cr(VI). Due to the strong positive electronegativity of Al3+ and the negative electronegativity of C in the vicinity of Al, Cr(VI) is further reduced to Cr(III) by C-Al. Therefore, the method proposed in this paper for preparing Al-doped carbon materials from waste cotton fabric offers a new approach and potential application for the production of high-performance adsorbent materials from waste cotton fabric.

Teak leaf biochar production for sustainable forest waste management at low temperatures

This study investigates the possibilities of producing biochar from teak leaves as an environmentally beneficial approach to managing forest waste in a sustainable manner. Teak leaves, a readily available forest by-product, were converted into biochar through a low-temperature pyrolysis process using a top-lit updraft mechanism. The results demonstrate the efficiency of this approach, yielding a substantial biochar output of 37.4 wt%, with its thermal field modelled perfectly via Levenberg-Marquardt algorithm in ANN topology. Elemental analysis of the teak leaf biochar revealed a high carbon content of 64.40%, positioning it as a valuable carbon-rich material suitable for various applications. Textural properties analysis indicated a significant surface area of 371.78 m2/g and a total pore volume of 0.175 cm³/g, enhancing its potential for various applications. Scanning Electron Microscopy (SEM) investigations showed a diverse network of pores and a rough surface structure, reinforcing the biochar’s versatility. This study shows the environmental benefits of low-temperature teak leaf biochar production, because it provides a carbon-content-preserving, sustainable alternative for handling forest wastes.

Kapok fiber composites minimizing secondary waste and disposal costs for large-scale radioactive liquid treatment

Conventional liquid treatments for large-scale, low-level radioactive wastewater, such as ion exchange and waste solidification, face challenges due to the large amounts of secondary waste and high disposal costs. A new large-scale decontamination method is proposed that uses kapok fiber composites for rapid radionuclide adsorption and high volume reduction to minimize secondary waste. The composite consists of natural zeolite and kapok holocellulose, which has high water-soaking ability and low-temperature pyrolysis. The kapok composites, fabricated using a commercial wet-laid nonwoven manufacturing process, absorbs 99% of low-level radioactive cesium in 20 min, reducing the volume by 98% and the weight by 47% at 300 °C. The low-temperature pyrolysis process below 300 °C prevents cesium desorption and gasification by avoiding zeolite destruction. The mass-producible kapok composites can be used for adsorbing various radionuclides in large-scale wastewater by attaching specific adsorbents for target isotopes to the composites.

Using a Low-Temperature Pyrolysis Device for Polymeric Waste to Implement a Distributed Energy System

Due to global changes, the international community is paying attention to the application of innovative energy technologies to meet the sustainable development of ecology and the environment. As a result, the concept of “waste-to-energy” has been developed. This study proposes a modular device for low-temperature pyrolysis (less than 300 °C) of polymers as a verifiable framework for a decentralized energy supply. Experiments with various plastics as waste feedstocks for conversion into fuel products were carefully analyzed. Mixed plastics (petrochemical polymers) and natural materials (organic polymers) were further subjected to energy conversion efficiency evaluation. The feasibility of continuous implementation was verified, converting 4000 kg of waste plastics with chemical potential into 3188 L of waste polymer oil (WPO), and generating 6031 kWh of electricity. Integrated electromechanical control realizes a low-temperature microwave pyrolysis process with low pollution emissions. The new technology harvests energy from troublesome garbage, reduces waste disposal volume by 55~88%, and produces cleaner, low-toxicity residual, easy-to-store fuel that can be used in general internal combustion engines. Standardized modular equipment provides an effective solution for resilient energy systems, and its easy scalability can reduce the load on the basic grid and improve the stability and dispatchability of energy supply. This research will realize on-site waste treatment, reduce transportation energy consumption, meet regional energy demands, and apply it to coastal, remote villages, offshore platforms, and emergency scenarios.

Preliminary Studies on the Purification of Bleaching Earth from Slack Wax Residues in the Adsorption Refining by Low-Temperature Pyrolysis Process

Abstract The essence of the low-temperature pyrolysis process presented below is the processing of contaminated bleaching earth, resulting in a purified bleaching earth, high calorific oil with an average level of 45.5 MJ / kg and synthesis gas that can be used to heat the reactor. For research purposes, a proprietary low-pressure reactor with a system of direct cooling of hydrocarbon vapors was used. The main advantages of the presented method are the limitation of technological processes to a minimum and the ease of automation by reducing the entire cycle to one device.

A new sensor for the rapid electrochemical detection of ractopamine in meats with high sensitivity

In this research, g-C3N4/Cu@CoO/NC, which contained graphitic phase carbon nitride (g-C3N4) with a binary nanostructure and Cu@CoO/NC with a bimetallic MOF precursor, was constructed by a low-temperature pyrolysis process. The g-C3N4/Cu@CoO/NC was characterised by several techniques, including X-ray diffraction, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy. Further, it was used to prepare an electrochemical sensor for the detection of ractopamine (RAC) in meat samples. The sensor showed excellent electrochemical oxidation characteristics for RAC detection, with a wide linear range (0.005 μmol/L to 32.73 μmol/L) and low detection limit (1.53 nmol/L). Meanwhile, the reproducibility, stability and interference of the g-C3N4/Cu@CoO/NC/GCE sensor were found to be excellent. Besides, the g-C3N4/Cu@CoO/NC/GCE sensor was well-used for the detection of RAC in pork, pig liver and lamb samples with recovery rates ranging from 96.5 % to 102.2 %.

The Release and Reduction of Mercury from Solid Fuels through Thermal Treatment Prior to Combustion

The main source of mercury (Hg) anthropogenic emissions is the combustion of hard and lignite coal in power plants. Reduction of Hg emissions from coal-based power production systems involves Hg removal from the fuel before combustion/gasification by thermal treatment (i.e., low-temperature pyrolysis). Herein, we present the results of laboratory and bench-scale studies on Hg removal from coal via thermal fuel treatment. The influence of the process temperature and coal residence time in the reaction zone on Hg removal efficiency and fuel parameters is studied. The properties of the process products are analyzed as follows: proximate and ultimate analysis for solids as well as H2, N2, CO, CO2, CH4, organic compounds C2–C5, density, and HHV for gaseous. The results show a substantial reduction of Hg in the fuel using a low-temperature pyrolysis process. At moderate pyrolysis temperature provided Hg removal efficiencies of up to 50% for hard coal and over 90% for lignite, with a moderate decrease in the chemical enthalpy of the fuel.

Changes in caking properties of caking bituminous coals during low-temperature pyrolysis process

We proposed a low-temperature pyrolysis treatment (LTPT) to destroy the caking properties of a fat coal (FC) and a 1/3 coking coal (CC). To reveal the factors affecting caking property, the changes in the chemical properties of pyrolysis products were analyzed using Fourier transform infrared spectrometry, X-ray diffractometer, and gas chromatograph/mass spectrometer (GC/MS). The in situ morphological changes in the liquid crystals produced by the two coal samples during LTPT process were also recorded using a hot-stage microscope. Of particular interest was a microscopic description of the factors affecting caking property. The results showed that the caking index (G) of FC decreased with increasing temperature and became zero at about 500 °C. Hot-stage microscope showed FC produced liquid crystals at 395 °C, the size of which continuously increased, with an accompanying of the generation of new liquid crystals. GC/MS showed large amounts of aliphatic hydrocarbons with the number of carbon of 6–25 (AlHsc6-25) and aromatic hydrocarbons with 2–4 rings (ArHsr2-4) were removed from FC. The aromaticity (fa) of FC increased only substantially from 395 to 494 °C. Meanwhile, the G of FC decreased only significantly in the same temperature range. A similar result was observed for CC. The removal of AlHsc6-25 leads to insufficient supply of hydrogen radicals; therefore, relatively high-molecular weight aromatics quickly cross-linked into semicoke. Additionally, the evolution of ArHsr2-4 and the increase in fa restrain the originating of crystal liquids. As a result, the loss of G was observed.

Capturing approach for the toxic bromides generated in low-temperature pyrolysis of brominated resin

In order to avoid secondary pollution during recovery of brominated resin, additives had been proposed for capturing bromine in high-temperature (700 °C) pyrolysis of brominated resin. However, the capture capacity and mechanism of CaCO3 and activated carbon to the generated micromolecule bromides was still unknown in the low-temperature (300 °C) pyrolysis process, in which brominated resin could realize debromination. This paper accurately analyzed the capture capacity and mechanism of CaCO3 and activated carbon to bromides by quantum chemistry calculation and wet experiments. CH3Br was considered as the main bromide in the low-temperature pyrolysis. The capture process of CaCO3 to CH3Br turned to be physisorption, and one CaCO3 particle with the size of 0.5 μm could captured 4.53 × 10−22 mol CH3Br. The capture capacity of CaCO3 to CH3Br is only 2.37 × 10−9 mol/g. Furthermore, the capture capacity of activated carbon to CH3Br was 8.50 × 10−5 mol/g. The mass of activated carbon needed to capture 4.03 × 10−4 mol CH3Br generated of 1 g brominated resin in low-temperature pyrolysis was 3.68 g. This paper contributes scientific information and approach to the safe resource recovery of waste brominated resin.

Life Cycle Assessment of Biochar Preparation of Chinese Traditional Medicine Residue by Low-temperature Pyrolysis

This study aimed to evaluate the environmental impacts of the biochar production process through low-temperature pyrolysis of Chinese medicine residue via life cycle assessment (LCA). An LCA model consisting of biomass pretreatment, pyrolysis, separation and cooling was developed. The results indicated that the low-temperature pyrolysis process has the highest environmental impact on AP and GWP. The consumption and direct emission of pyrolysis process were the primary sources of environmental impact. In addition, by comparing to the traditional landfill process of Chinese medicine residue, it turns out that the low-temperature pyrolysis process has improved environmental protection performance.

Synthetic Effects and Economic Accounting of Low-temperature Pyrolysis Process of Typical Medical Waste based on Kinetics Analysis

The thermogravimetric (TG) analysis was adopted to study the pyrolysis characteristics of two typical medical wastes at different heating rates (10, 20, and 50 °C/min), and the kinetic parameters were analyzed by the Coats-Redfern method. Finally, the economic evaluation of the technology was carried out. The results showed that the two typical medical wastes both have only one weight loss peak. The syringes and bamboo sticks pyrolysis ranged from 264.80 to 554.07 °C and from 205.66 to 487.05 °C, respectively. With the increase of the heating rate, the initial, final and peak temperatures of the two raw materials shifted to higher values. The pyrolysis reaction mechanisms of the syringes and bamboo sticks were summarized as the nucleation growth model (A2.5) and the second-order model (F2). The total investment of medical waste pyrolysis project is 59 million yuan, and the annual net gain is 11.85 million yuan. The investment recovery period of the project takes five years.

Carbon quantum dots in hard carbon: An approach to achieving PIB anodes with high potassium adsorption

Potassium ion batteries have become one of the most promising candidates for Lithium batteries replacement. Here we report a carbon quantum dots@hard carbon (CQDHC) composite electrode material for PIBs that was fabricated by a one-step low-temperature pyrolysis process for the first time. Without complicated post-processing steps, the as-obtained CQDHC can be directly used as a negative potassium electrode. The oxygen-rich carbon quantum dots (CQDs) were in-situ synthesized and randomly located in the hard carbon matrix, enhancing the disorder of CQDHC and promoting potassium adsorption. As a result, the initial charge capacity reaches 361 mAhg−1 and maintains a capacity of 237 mAhg−1 (75.7%) after 150 cycles at 100 m A g−1. The CQDHC electrode also shows long-term stable charge-discharge reproducibility and high columbic efficiency (97%). Even though with low surface area, the CQDHC electrode still offers better rate performance than most of hard carbon materials owing to the synergy effect of carbon quantum dots. The detailed, quantitative analysis of the K+ storage process reveals the dual-mechanism in carbon quantum dots@hard carbon. The present study sheds light on using carbon quantum dots to enhance the performance of carbon electrodes in potassium ion batteries.

Fabrication of Ni2O3–NiCx core–shell nanoparticles on fluorine-doped tin oxide electrodes via oxygen feeding from SnO2 under hydrogen conditions and their electrochemical performance as supercapacitors

The successful synthesis of Ni2O3–NiCx on SnO2/glass electrodes by a combined liquid/liquid interfacial reaction and low-temperature pyrolysis process under hydrogen gas conditions, is reported. The prepared samples were analyzed by various characterization tools. To evaluate the performances of the Ni2O3–NiCx on SnO2/glass electrodes as supercapacitors, cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), cycle stability and electrochemical impedance spectroscopy (EIS) were also carried out the Ni2O3–NiCx core-shell-structured electrode displayed supercapacitive behavior in 1.0 M KOH with a high specific capacitance value of 796 F g−1 and a relatively good rate capability at high current densities. Moreover, it also exhibited remarkable cycle stability, this research provides a valuable and effective approach to enhance the performance of materials applied as supercapacitors.

Upgrading of sewage sludge by low temperature pyrolysis: Biochar fuel properties and combustion behavior

The co-incineration of sewage sludge (SS) in thermal power plants offers a promising method of sustainable waste handling for China due to its large-scale capacity and high compliance with pollutant emission control regulations. However, conventional co-incineration treatment of SS has unstable combustion performance and a lower blending ratio due to the high moisture content and complex components of SS. To overcome this drawback, the low-temperature pyrolysis (LTP) process has been used to upgrade the fuel properties of SS. In this study, different pyrolysis temperatures (300–500 °C) were employed to convert SS to clean solid fuel and the biochar properties and combustion behaviors were evaluated. The results showed that when the pyrolysis temperature was <400 °C, 50–60% of the energy in the raw sludge (RS) was converted into biochar. Analysis of the fuel properties showed that the fuel ratio of the biochar was significantly increased to 0.54 and the H/C and O/C atomic ratios reduced to 0.76 and 0.33 by prolonging the pyrolysis process. Moreover, around 70% nitrogen and sulfur were removed. The thermogravimetric analysis showed that the combustion decomposition was altered from devolatilization and combustion for RS to char combustion for biochar. The combustion reaction of RS and biochar were best fitted to the first-order. The combustion behaviors of biochar were less violent and more stable than those of RS due to the lower activation energy and frequency factor in the pyrolysis temperature range of 300–350 °C.

TiN nanoparticles hybridized with Fe, N co-doped carbon nanosheets composites as highly efficient electrocatalyst for oxygen reduction reaction

Titanium nitride (TiN) nanoparticles hybridized with Fe and N co-doped carbon nanosheets (Fe-N-CNS) composite is constructed by a facile in-situ self-template strategy. During the low-temperature pyrolysis process, uniformly TiO2 nanoparticles were formed and anchored into Fe-doped carbon nitride nanosheets. After further high-temperature pyrolysis, Fe-doped carbon nitride nanosheets as self-template could decompose to form Fe-N co-doped carbon nanosheets and TiO2 nanoparticles were transferred into TiN nanoparticles during the high-temperature nitriding treatment. As a result, TiN nanoparticles hybridized with Fe-N-CNS composites (TiN/Fe-N-CNS) exhibit excellent ORR activity with more positive half-wave potential (0.87 V) and large limiting current density (4.43 mA cm−2) as well as high selectivity (electron transfer number around 4) for ORR in alkaline media. Moreover, it also shows higher stability and better methanol tolerance than those of commercial Pt/C catalyst in both alkaline and acidic media. This excellent ORR performance is attributed to the enhanced specific surface area and synergistically promotion effect of uniformly dispersed TiN on Fe-N-CNS.

Processing of Ce0.8Gd0.2O2-δ barrier layers for solid oxide cells: The effect of preparation method and thickness on the interdiffusion and electrochemical performance

Ce0.8Gd0.2O1.9 (CGO) barrier layers are required to mitigate the chemical reactions between Sr-containing oxygen electrode materials and Zr-based oxygen ion conductors in high-temperature solid oxide cells. Barrier layers produced by different methods were studied in this work. As a reference, a cell with no barrier layer was measured. The application of the powder-processed barrier layers, considerably increases the performance. For further comparison, thin and dense CGO layers were produced by a low-temperature spray pyrolysis process. Three different thicknesses were evaluated: ∼300 nm, ∼700 nm and ∼1500 nm. The best performance was found for the ∼700 nm thick CGO barrier layer. It showed low ohmic and polarisation resistances. The low thickness and high density of the CGO barrier layer were found to be the important factors. The cells with the ∼700 nm CGO barrier layers were also evaluated for their electrolysis performance as well as fuel cell durability.

Mechanistic insight into the role of N-doped carbon matrix in electrospun binder-free Si@C composite anode for lithium-ion batteries

To improve the long cyclic stability and rate capability of Si-based anode, we demonstrate a core-shell structural Si@NC composite decorates with N-doped carbon network using a low-cost, a simple process of electrospinning and low-temperature pyrolysis. Si@PVP/Urea fabric composite spun on the copper foil was directly carbonized and then was cut into wafers used as the electrode plates without extra conductive agent and binder. The enhanced rate capability and cyclic stability of special structural Si@NC is mainly ascribable to N-doped carbon matrix providing numerous active sites, which attract Li to those points in an efficient way, and the core-shell structures supply high mechanical strength for Si@NC composite. Importantly, almost 3-fold improvement in the capacity retention rate of the Si@NC has been observed at high current densities of 1.6 and 3.2 A g−1. Meanwhile, DFT calculations confirm that Li will be easily adsorbed by N-active sites in N-doped carbon model to strengthen chemical absorption ability, which could have more chance to grab the quickly moving Li in a brief period. It is significant for theoretical guidance of subsequent studies. The findings should make an important contribution providing a great possibility for the mass production and application to the field of lithium-ion battery.

Directional preparation of naphthalene oil-rich tar from Beisu low-rank coal by low-temperature catalytic pyrolysis

Low-rank coal (LRC) can be converted to high value-added naphthalene and its alkylated derivatives through low-temperature catalytic pyrolysis. In this paper, the catalytic pyrolysis of Beisu LRC in a fixed-bed at low temperature was investigated. And the catalytic effects of HZSM-5, low-temperature carbocoal (LtC), and LtC-HZSM-5 on the content and yield of naphthalene oil were examined. The results showed that the generation of naphthalene oil in low-temperature LRC pyrolysis (LT-LP) process could be improved when LtC (prepared at 550 °C) or HZSM-5 was individually used as a catalyst. Compared with sole pyrolysis of raw LRC, the addition of the LtC-HZSM-5 catalyst increased the content of naphthalene oil from 11.19 wt.% to 31.49 wt%. And the yield of naphthalene oil was increased from 1.07 wt% to 5.31 wt%. The reactions of micromolecular hydrogen-containing radicals (·MHCR) were optimized by LtC. ·MHCR could be captured in relatively low-temperature region (200–400 °C) and released at high temperature by LtC. The generation of phenolics was inhibited by HZSM-5. As a result, the naphthalene oil-rich tar was obtained through low-temperature LtC-HZSM-5 catalytic pyrolysis of Beisu LRC.

In-Plane Highly Dispersed Cu2O Nanoparticles for Seeded Lithium Deposition.

Uncontrollable dendrite growth is one of the major problems that hinders the application of lithium (Li) metal anode in rechargeable Li batteries. Achieving uniform Li deposition is the key to tackle this intractable problem. Herein, we report the highly dispersed Cu2O nanoparticles (NPs) in situ anchored on partially reduced graphene oxide via a low-temperature pyrolysis process could serve as seeds for the Li metal deposition. The lithiophilic nature of Cu2O NPs reduces the overpotential of Li nucleation and relieves the electrode polarization, enabling uniform Li nucleation and smooth plating, thus effectively eliminating dendritic and dead Li. As a result, the resulted Li metal electrodes deliver a high Coulombic efficiency of 95.6% after 140 cycles at a current density of 2 mA cm-2 and a prolonged lifespan (800 h at 1 mA cm-2) for the symmetrical cell.