Search Results (4)

Alkaline delignification is a keystone pretreatment that governs carbohydrate accessibility, energy use, and yields across pulp and biorefinery value chains, yet its kinetic understanding remains fragmented and largely confined to bench-scale studies. This review provides an integrated assessment of the evolution and current state of kinetic approaches applied to alkaline delignification of lignocellulosic biomass, aiming to bridge academic research and industrial application. A systematic review following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta Analyses) guidelines identified 74 peer-reviewed articles and 359 patents published between 1995 and 2025. Kinetic models were classified into conventional (nth-order and pseudo-first-order) and emerging categories (Avrami/Š–B, diffusion-based, mechanistic multistep, isoconversional, and ML/statistical). The results show that pseudo-first-order kinetics and batch-scale studies dominate the literature, while pilot-scale validation and hybrid mechanistic data-driven frameworks remain limited. Patent analysis revealed technological convergence within D21C and C08B IPC domains, reflecting growing industrial interest in alkaline pulping and cellulose valorization. Unlike previous reviews, this work uniquely integrates conventional and emerging kinetic models with a patent-based technological perspective, providing a unified view of academic and industrial progress. The insights presented here provide a foundation for advancing future research, particularly by encouraging the development of standardized experimental protocols and the validation of kinetic models across multiple scales. Moreover, this review provides a consolidated reference for both academic researchers and industrial practitioners seeking to enhance delignification efficiency, reduce reagent consumption, and improve the sustainability of biorefinery processes. Full article

Expansive agents (CaO, MgO, C₄A₃Š) were incorporated into coal gangue-slag-fly ash based geopolymer (CSFG). The influence of expansive agents on the properties and microstructure of CSFG was investigated by macroscopic tests including setting time, compressive strength, and shrinkage values, along with microstructural tests including XRD, FTIR, SEM-EDS, and BET. Results showed that CaO and MgO added separately and their combination exhibited similar trends, with CaO added separately yielding the most favorable outcome. In comparison to the control group, the sample with 7% CaO reduced initial and final setting times by 43.6% and 52.8%, increased 28 d compressive strength by 12.6%, and decreased 28 d drying shrinkage and autogenous shrinkage values by 43.5% and 29.9%, respectively. Moderate MgO and CaO enhanced dissolution of precursors (e.g., coal gangue, fly ash), promoting formation of C-A-S-H gel, CaCO₃, and periclase. Incorporating 3% C₄A₃Š shortened initial and final setting times by 41.3% and 17.8%, improved 28 d compressive strength by 32.2%, but increased 28 d drying and autogenous shrinkage values by 58.3% and 12.8%. Exceeding 3% content significantly reduced 3 d strength. Excessive C₄A₃Š promoted rapid ettringite (AFt) formation, leading to microcracking. Correction prediction models for drying shrinkage strain and autogenous shrinkage strain of CSFG were developed, demonstrating good agreement between predictive and actual values. Full article

Calcium sulfoaluminate (CSA) cement has emerged as a low-carbon alternative to ordinary Portland cement (OPC), offering reduced CO₂ emissions and rapid strength development. However, the role of the ferrite phase in CSA systems remains underexplored. This study investigates the influence of ferrite-phase composition on CSA cement properties through targeted clinker design, hydration analysis, and macro–micro performance testing. Nine clinker formulations were synthesized by systematically increasing the ferrite content (10–30%) while adjusting belite (C₂S) proportions, using limestone, bauxite, and supplementary Fe₂O₃/SiO₂. Results reveal that the ferrite phase enhances the formation and stabilization of ye’elimite (C₄A₃Š) during clinkering and reduces low-activity transitional phase products. Increasing the iron-phase content appropriately improves early strength by promoting ettringite (AFt) formation and refines pore structures to enhance later strength development. The maximum strength improvement is achieved when the target ferrite-phase content is set to 15%, showing a 25.1% increase in 1 d strength and an 11.5% increase in 28 d strength. While ferrite phases and C₂S ensure long-term strength gains, excessive ferrite content reduces C₄A₃Š availability, limiting early AFt formation and compromising initial strength. These findings highlight the dual role of the ferrite phase in optimizing CSA cement performance and sustainability, providing a foundation for designing ferrite-rich, low-carbon binders. Full article

Low-carbon ecological cement composites are among the most promising construction materials. With low energy consumption, low carbon dioxide emissions, and high early strength, sulfoaluminate cement (SAC) is a low-carbon ecological building material. In addition, graphene nanoplates (GNPs) exhibit excellent performances. In this study, GNPs were dispersed by a combination of dispersant and ultrasonic treatment, and the dispersion effect of GNPs was characterized. The effect of GNPs on the hydration process and products of SAC was studied, revealing that GNPs accelerate SAC hydration. The hydration heat and ICP results showed that in the SAC hydrolysis stage, C₄A₃Š (ye’elimite) hydrolyzed and released Ca²⁺. GNPs absorbed the Ca²⁺, and the Ca²⁺ concentration around C₄A₃Š decreased, which would promote the hydrolysis of C₄A₃Š and release more Ca²⁺, accelerating the hydration of SAC and the nucleation effect of GNPs, and providing sites for the formation of hydration products. The analysis of XRD (X-Ray Diffraction) and TGA (Thermal Gravity Analysis) showed that GNPs promoted the hydration of SAC and formed more AFt (ettringite) and AH₃ (gibbsite). The generated hydration products fill the pores of the matrix and are closely connected to the GNPs to form a whole, which improves the cement matrix’s mechanical properties. Full article