Effect of pre-oxidation temperature and heating rate on the microstructure of lignin carbon fibers

Synergistic effects enabled efficient photocatalytic removal of ofloxacin antibiotic in wastewater by layered double hydroxides loaded lignin-derived carbon fibers

The environmental problems caused by the abuse of antibiotics are raising serious attention, and the removal of antibiotics in wastewater is meaningful yet challenging. In this work, lignin-derived carbon fibers loaded layered double hydroxides (LDH@LCF) has been prepared for the removal of ofloxacin (OFX) from wastewater via photocatalysis, which exhibit a high degradation efficiency of 96 % under visible light and maintained 90 % after five reuses. The effects of Zn2+/Fe3+ in the samples and other parameters affecting the photocatalytic efficiency of OFX have been systematically investigated. Results demonstrated that the enhanced photocatalytic efficiency is derived from the synergistic effect of the Zn2+ and Fe3+ in the LDH with a reduced band gap of the catalyst, higher number of oxygen and metal unsaturated coordination sites, and rapid removal of photogenerated electrons. The working mechanism and degradation pathways for OFX by LDH@LCF are also elucidated in detail.

Alginate-derived biomass carbon‑molybdenum disulfide heterogeneous materials: Vertically grown/uniformly dispersed molybdenum disulfide nanosheets/nanoflowers for wastewater treatment

In order to improve the dispersion of molybdenum disulfide (MoS2) and enhance the performance of MoS2, two alginate-derived biomass carbon-MoS2 (BC-MoS2) composites: CMB/CMS, were prepared by introducing BC during the synthesis of MoS2 by hydrothermal. The effects of different gels, times and temperatures of the synthesized BC-MoS2 were investigated, and the adsorption capacity for methylene blue (MB), basic fuchsin (BF) and copper ions (Cu2+) was tested. The results indicated that the vertical growth of MoS2 on the BC surface could be realized when using xero-gel, while the BC and MoS2 were mixed uniformly when using wet-gel. Compared with MoS2, the hydrophilicity and water dispersibility of BC-MoS2 were greatly improved, and BC-MoS2 had better adsorption capacity for MB/BF/Cu2+ (99.61/86.83/60 mg/g). The adsorption mechanism exhibits that the adsorption force of BC-MoS2 on MB/BF is mainly based on the electrostatic force, and the adsorption on Cu2+ comes from the electrostatic force and the Lewis soft-soft interaction. This study dramatically enriches the application of transition metal chalcogenides and provides a meaningful reference for wastewater treatment.

Recovery of energy and carbon fibre from wind turbine blades waste (carbon fibre/unsaturated polyester resin) using pyrolysis process and its life-cycle assessment

Recovery of carbon fibres and resin from wind turbine blade waste (WTB) composed of carbon fibres (CF)-reinforced unsaturated polyester resin (UPR) has been environmentally challenging due to its complex structure that is not biodegradable and that is rich in highly toxic styrene (main component of UPR). Within this framework, this paper aims to liberate CF and UPR from WTB using a pyrolysis process. The treatment was performed on commercial WTB (CF/UPR) up to 600 °C using a 250 g reactor. The UPR fraction was decomposed into liquid and gaseous phases, while CF remained as a residue. The composition of gaseous phase was monitored during the entire treatment using a digital gas analyser, while gas chromatography-mass spectrometry (GC-MS) was used to characterize the collected liquid phase. CF fraction was collected and exposed to additional oxidation process after treatment at 450 °C for purification propose, then it was analysed using FTIR and SEM-EDX. Finally, the life cycle assessment (LCA) of the CF/UPR pyrolysis was studied using SimaPro software and the results were compared with landfill disposal practices. The pyrolysis results manifested that 500 °C was sufficient for UPR decomposition into styrene-rich oil and gaseous products with yields of 15.23 wt% and 6.83 wt%, respectively, accompanied by 77.93 wt% solid residue including CF. The LCA results showed that pyrolysis with oxidation process has high environmental potential in WTB recycling with significant reduction in several impact categories compared to landfill. However, the pyrolysis scenario revealed several additional environmental burdens related to ecosystems, acidification, Ozone formation, and fine particulate matter formation that must be overcome before upscaling.

Comparison of Oil-Seed Shell Biomass-Based Biochar for the Removal of Anionic Dyes-Characterization and Adsorption Efficiency Studies

This research investigated the synthesis of biochar through the direct pyrolysis of pre-roasted sunflower seed shells (SFS) and peanut shells (PNS) and compared their application for the effective removal of textile dyes from wastewater. Biochar prepared at 900 °C (SFS900 and PNS900) showed the highest adsorption capacity, which can be attributed to the presence of higher nitrogen content and graphite-like structures. CHNS analysis revealed that PNS900 exhibited an 11.4% higher carbon content than SFS900, which enhanced the environmental stability of PNS biochar. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses of the produced biochar indicated the degradation of cellulosic and lignin moieties. X-ray photoelectron spectroscopy (XPS) revealed a 13.8% and 22.6% increase in C-C/C=C mass concentrations in the SFS900 and PNS900, respectively, and could be attributed to the condensation of polyaromatic structures. Batch experiments for dye removal demonstrated that irrespective of dye species, PNS900 exhibited superior dye removal efficiency compared to SFS900 at similar dosages. In addition to H-bonding and electrostatic interactions, the presence of pyridinic-N and graphitic-N can play a vital role in enhancing Lewis acid-base and π-π EDA interactions. The results can provide valuable insights into the biochar-dye interaction mechanisms.

Improved photocatalytic property of lignin-derived carbon nanofibers through catalyst synergy

Converting lignin into high value-added products is essential to reduce our dependence on petroleum resources and protect our environment. In this work, TiO₂ and g-C₃N₄ are loaded in the lignin-derived carbon nanofibers (LCNFs) and an efficient LCNFs-based photocatalytic material (TiO₂/g-C₃N₄@LCNFs) is developed. The spinnability of lignin solution, the chemical structure and morphology of the LCNFs, and the catalytic degradation property of the TiO₂/g-C₃N₄@LCNFs for Rhodamine B (RhB) are systematically investigated. The TiO₂/g-C₃N₄@LCNFs achieve a 92.76 % degradation rate of RhB under UV-vis irradiation, which is close to or higher than most reported carbon fiber-based photocatalysts. The excellent degradation property of the photocatalysts can be ascribed to the synergy of TiO₂ and g-C₃N₄, which improves the excitation efficiency of electron and hole, and prolongs the lifetime of electron-hole pairs. We envision that our work will provide some guidance for the development of efficient photocatalysts based on biomass-derived fiber materials.

Lignin-based carbon fibers: Insight into structural evolution from lignin pretreatment, fiber forming, to pre-oxidation and carbonization

Lignin remains the second abundant source of renewable carbon with an aromatic structure. However, most of the lignin is burnt directly for power generation, with an effective utilization rate of <2 %, making value addition on lignin an urgent requirement. From this perspective, preparation of lignin-based carbon fibers has been widely studied as an effective way to increase value addition on lignin. However, lignin species are diverse and complex in structure, and the pathway that enables changes in lignin structure during pretreatment, fiber formation, stabilization, and carbonization is still uncertain. In this review, we condense the common structural evolution route from the previous studies, which can serve as a guide towards engineered lignin carbon fibers with high performance properties.

Recent advances in lignin-based carbon materials and their applications: A review

As the most abundant natural aromatic polymer, tens of million of tons of lignin produced in paper-making or biorefinery industry are used as fuel annually, which is a low-value utilization. Moreover, burning lignin results in large amounts of carbon dioxide and pollutants in the air. The potential of lignin is far from being fully exploited and the search for high value-added application of lignin is highly pursued. Because of the high carbon content of lignin, converting lignin into advanced carbon-based structural or functional materials is regarded as one of the most promising solutions for both environmental protection and utilization of renewable resources. Significant progresses in lignin-based carbon materials (LCMs) including porous carbon, activated carbon, carbon fiber, carbon aerogel, nanostructured carbon, etc., for various valued applications have been witnessed in recent years. Here, this review summarized the recent advances in LCMs from the perspectives of preparation, structure, and applications. In particular, this review attempts to figure out the intrinsic relationship between the structure and functionalities of LCMs from their recent applications. Hopefully, some thoughts and discussions on the structure-property relationship of LCMs can inspire researchers to stride over the present barriers in the preparation and applications of LCMs.