Frontiers in Chemical Engineering

Quaternized modified waste wood-derived porous carbon electrode for highly selective capacitive deionization denitrification

2026-03-19

Sumei Zheng, Qin Liu, Xiaomei Huang, Maochun Wei, Furong Tu, Haomei Liu, Meina Xie, Xiaoqing Zhang, Huiju Zhang

For tackling the critical challenge of poor selectivity in nitrate pollution control within industrialized recirculating aquaculture systems, this study develops a cetyltrimethylammonium bromide-modified self-supporting wood-derived porous carbon composite (CTA-3DPC) as a highly selective capacitive deionization electrode material. The CTA-3DPC features a vertically aligned hierarchical porous structure, which facilitates solution mass transfer during the electrosorption process. When employed as the anode in electrosorption, CTA-3DPC demonstrates strong selectivity for NO3− over competing anions such as Cl−, SO42‒, and H2PO4−. The adsorption capacity of CTA-3DPC for NO3− reaches 40.67 mg g-1, significantly surpassing those for Cl− (8.56 mg g-1), H2PO4− (18.1 mg g-1), and SO42‒ (23.07 mg g-1). Notably, CTA-3DPC achieves a NO3−/Cl− selectivity coefficient of 13.23, substantially exceeding previously reported values. This high selectivity is attributed to the electrostatic loading of CTAB onto the negatively charged wood-derived activated carbon surface, where the hydrophilic quaternary ammonium cations orient outward, forming a dense and stable positively charged layer at the carbon/electrolyte interface. This layer reduces the potential of zero charge on the material surface and favors the selective adsorption of NO3− due to its planar structure and weak solvation effects. This work provides a novel strategy for fabricating biomass-based electrodes with high nitrate selectivity.

The influence of nano-biochar on the mechanical and flame resistance of recycled PLA composites

2026-02-16

G. Anbuchezhiyan, A. Vivek Anand, S. Senthil Babu, S. Madhubalan, Vigneshwaran Shanmugam, Rhoda Afriyie Mensah

The growing accumulation of plastic and agricultural waste highlights the urgent need for sustainable material alternatives. This study investigates the incorporation of nano-biochar derived from cashew nut shell biomass to enhance the mechanical and thermal performance of recycled polylactic acid (rPLA). Nano-biochar produced via controlled pyrolysis and high-energy ball milling was incorporated into rPLA at 0–2 wt% loadings through melt compounding and injection moulding. The resulting composites were evaluated for tensile, flexural, impact, and interlaminar shear strength (ILSS), alongside UL-94 flammability testing. A one-way ANOVA followed by Tukey’s HSD post-hoc analysis confirmed statistically significant improvements (p < 0.05) across all mechanical properties. The tensile strength of virgin PLA (32.23 MPa) decreased to 25.92 MPa in recycled PLA due to polymer chain scission; however, the addition of 1.5 wt% nano-biochar increased tensile strength to 49.54 MPa and ILSS from 21.37 MPa to 36.31 MPa. Flexural and impact strengths also rose by 34.19% and 45.85%, respectively, compared to unfilled rPLA. In UL-94 testing, the rPLA1.5 composite achieved a V-0 rating with no dripping, indicating excellent flame retardancy. Overall, nano-biochar reinforcement not only restored but substantially enhanced the mechanical integrity and fire resistance of rPLA, with ANOVA validating the statistical robustness of these improvements. This work demonstrates a viable circular-economy pathway for converting biomass waste into functional nano-reinforcements for sustainable polymer composites. These composites are particularly suitable for automotive interiors, building materials, and consumer goods where improved flame resistance and mechanical durability are required.

Editorial: Hydrothermal liquefaction: aqueous phase treatment, product recovery, and downstream implications

2026-01-29

Xavier Fonoll Almansa, Belinda Sturm, Daniele Castello, Michael R. Thorson

A physically based rheological model for predicting the flow behavior of non-newtonian crude oil mixtures under cold climate conditions

2026-01-27

Alexander Nikolaev, Andrey Goluntsov, Kristina Plotnikova

Accurate prediction of the rheological behavior of heavy crude oil mixtures is essential for pipeline transport under cold climate conditions. This study presents a physically based non-Newtonian rheological model that incorporates the coupled effects of temperature and mixture composition through temperature- and concentration-dependent expressions for the consistency coefficient and flow behavior index. The model was calibrated and validated using 88 experimental rheological measurements on binary mixtures of heavy Severo-Komsomolskoye and light Vankor crudes over a temperature range of 5C–60 °C, heavy-oil concentrations of 0%–100%, and shear rates of 1–300 s-1. The proposed model predicts shear stress with a mean relative deviation of 8.7% and a root mean square error below 0.95 Pa, outperforming conventional Arrhenius, Refutas, and classical power-law correlations by a factor of 2–3. The model accurately captures the transition from non-Newtonian to near-Newtonian behavior with increasing temperature and dilution, providing a practical tool for hydraulic calculations and flow assurance design in cold-region pipeline systems.

Epoxidation of allyl alcohol to glycidol over TPAOH-treated titanium silicalite-1 extrudates

2026-01-16

Gideon Abaidoo Ocran, Bosong Zhang, Yi Zuo, Huali Tan, Gudan Li, Hong Yang, Chunshan Song, Xinwen Guo

The epoxidation of allyl alcohol with H2O2 over titanium silicalite-1 (TS-1) is an environmentally friendly route for producing glycidol. However, the catalytic activity and stability of TS-1 is not satisfactory. In this study, strip-shaped TS-1 was hydrothermally treated by TPAOH solution, change theTi coordination states and diffusion property, thereby enhancing its catalytic performance. The influences of TPAOH concentration and treating time on the physical chemical property and catalytic performance were studied systematically. It was found that the SiO2 agglomerant was dissolved and crystallized during the treatment, resulting in an increased Si content on the external surface. The tetrahedrally coordinated Ti was transformed to pentahedrally and octahedrally coordinated Ti, which possess higher catalytic activity for selective oxidation. The treatment also leads to the formation of cavities in the TS-1 crystals, which can shorten the diffusion pathway of substates and improve the diffusion property. Both the chemical property and microstructure enhance the catalytic activity for allyl alcohol epoxidation.

The crystal facet effect of ZnAl2O4 in the CO2 hydrogenation to methanol

2026-01-07

Yigong Hu, Qiang Liu, Zhiqun Wang, Xinle Zhang, Xiangkun Zhou, Guanghui Zhang, Xinwen Guo

Zinc aluminate (ZnAl2O4) is one of the most widely used catalysts in the hydrogenation of carbon dioxide to methanol. During the CO2 hydrogenation reaction, ZnAl2O4 undergoes surface reconstruction to form ZnO, creating a ZnO/ZnAl2O4 active interface that promotes methanol production. However, the active crystal facets on which this surface reconstruction occurs, as well as the intrinsic and extrinsic factors influencing the reconstruction process, remain unclear, posing challenges to understanding the structure of the real active sites and the structure-activity relationship. In this work, ZnAl2O4 with three morphologies—granular, rod-like and plate-like—were synthesized, primarily exposing the (222), (311) and (440) crystal facets, respectively. The granular ZnAl2O4 exhibited superior methanol synthesis performance compared to the rod-like and plate-like morphologies. This enhancement is attributed to the reaction-induced formation of highly active ZnO predominantly exposing the (002) facet on the surface of granular ZnAl2O4. Furthermore, the intrinsic and extrinsic factors affecting the surface reconstruction process were investigated. Increasing the reaction temperature, the gas hourly space velocity (GHSV) and the H2/CO2 ratio were found to promote the surface reconstruction rate and enhance the steady-state space-time yield (STY) of oxygenates (Oxy). The granular ZnAl2O4, with its (222) facet featuring a spatial hexagonal arrangement of adjacent Zn atoms, exhibits stronger H2 activation capability, thereby promoting the surface reconstruction of active ZnO. These findings provide important guidance for the design and synthesis of highly efficient zinc-based oxide catalysts.

4E comparative analysis of energy transition scenarios for the decarbonization of a chocolate factory utilities in Brazil

2025-12-17

Audrey Novelli Gonçalves, Francisco Mello Fonseca, Alexandre Persuhn Morawski, Pedro Rosseto de Faria, José Joaquim Conceição Soares Santos

The government of the state of Espírito Santo, Brazil, has established that minimizing emissions, by considering the natural gas as the best fossil fuel during the energy transition period, and energy efficiency are two of the four strategies for industries to competitively achieve the energy transition and decarbonization. In this framework, a major chocolate factory currently meets its chilled-water demand with electricity from the national grid and its hot-water demand with natural gas boilers. This study evaluates alternative configurations based on the integration of Organic Rankine Cycle (ORC) and/or Vapor Compression Refrigeration (VCR) systems, simultaneously generating electricity, chilled water and/or hot water. Three scenarios are proposed and comparatively evaluated using a 4E (energy, exergy, environmental, and economic) assessment. Thermodynamic and environmental modeling of the current and proposed scenarios was conducted using nominal and operational data, with simulations performed in EES software. Mass, energy, and exergy balances were carried out, along with associated CO2 emissions. The economic analysis considered both operational costs and capital investments, the latter estimated through parametric equations for equipment sizing and costing. Feasibility indicators were applied, such as payback, net present value (NPV), and internal rate of return (IRR). The results indicate the VCR configuration, without ORC, as the most advantageous performance. This scenario requires an investment of US$ 2,679,612.19, resulting a payback period of 2 years and 3 months, an IRR of 51.40% and achieving the lowest CO2 emissions (0.467 ton/h) due to the elimination of natural gas boilers, using total electrification of the process. Given the relatively low emission factors of the Brazilian interconnected electric grid and the competitive electricity tariffs, electrification of industrial utilities emerges as the most promising decarbonization pathway. Specifically, in this case, VCR simultaneously produces chilled and hot water with high efficiency and reduced environmental impact. Building on the conclusion that electrification is the most favorable option, new insights for research opportunities arise. Future studies could investigate the use of Photovoltaic Thermal (PVT) hybrid solar collectors for the simultaneous production of electricity and hot water, thereby reducing emissions, as well as the integration of energy storage systems to further enhance emission reductions.

Engineering an automated microbubble-assisted hybrid photobioreactor for CO2 capture and valorisation to polyhydroxybutyrate in indigenous algal biomass

2025-12-03

Saptarshi Dey, Abhishek Sahu, Vivek Dalvi, Biswajit Samir De, Anushree Malik

The integration of microalgal systems into carbon capture technologies offers a dual advantage; the mitigation of anthropogenic CO2 emissions and the sustainable production of high-value macromolecules. This study presents the engineering and pilot-scale operation of a 200 L microbubble-assisted hybrid photobioreactor for CO2 bio-fixation. Subsequent valorisation into lipids and biopolymers was obtained using an indigenous alga, Poterioochromonas malhamensis. A novel 3D-printed microbubble generator assembly (MBG) was retrofitted to a 1.2 m carbonation column (CC) and integrated with a 200 L high-rate algal pond (HRAP). Sequential high-speed bubble imaging at different column heights (H) under different liquid flow (QL) and gas flow (QG) regimes was processed and interpreted using a MATLAB based bubble analyser. A Gaussian distribution function was used to establish the most probable bubble diameter in the range 400–800 µm while achieving microbubble density of 61%–90% in the carbonation column to support efficient gas–liquid exchange. The hybrid reactor was further automated using a real-time pH feedback loop for CO2 dosing under photoautotrophic conditions with 5% (v/v) CO2 supplementation. The system maintained the culture media bicarbonate buffer in the optimal range (pH 7.2–8.5). The hybrid reactor yielded 0.423 gL−1 of biomass with a carbon content of 43.06% DCW, a CO2 bio-fixation rate of 44.05 mgL−1d−1, and polyhydroxybutyrate (PHB) content of 5.79% DCW. Our findings demonstrate the scalability, automation potential, and bioproduct yield enhancements of the hybrid system, making it a viable model for CCUS (carbon capture, utilization, and storage) through algal valorisation. The approach offers a technically sound, energy-efficient route for transforming inorganic carbon into commercially relevant algal macromolecules.