Boqiang Wu,Xiaodong Wang,Shibin Zhu,Yuehong Zhang,Junhao Ye,Haibo Zhang,Songhui Liu
Magnesium slag (MS) is an alkaline waste residue from magnesium smelting processes. This study aimed to utilize the magnesium oxide in MS and adopt MgCl 2 as the calcium carbonate crystal modifier to prepare high length-to-diameter ratio aragonite whiskers via wet carbonation , which can achieve high-value recovery of MS while capturing CO 2 and enhancing cement as underground filling material . The effects of MgCl 2 concentration on the carbonation process , composition, microstructure, and morphology were systematically investigated. With increasing MgCl 2 concentration, more aragonite was obtained, reaching 94.9 % at 0.5 M MgCl 2 . Notably, at 0.1 M MgCl 2 , high length-to-diameter ratio aragonite whiskers with 16 were achieved. Introducing 1 wt% MS carbonated at optimal 0.1 M MgCl 2 into cement increased the 3 d and 28 d compressive strengths by 17.8 % and 22 %, respectively. Moreover, an excellent CO 2 sequestration capacity of up to 20.33 g CO 2 per 100 g MS was obtained for the carbonated MS. Therefore, wet carbonated MS with high content aragonite whiskers is a promising method for MS high-value utilization while reducing cement usage and CO 2 emission, as well as improving cement performance as underground filling material.
The study aims to evaluate the catalytic potential of a Ni-based catalyst supported by magnesium slag (MS) for catalytic reforming of pyrolysis volatiles from pine sawdust. The catalysts were prepared by a wet impregnation method. The effects of different parameters (Ni loading content, calcination/catalytic bed temperature and steam to carbon (S/C) ratio) on the catalytic performance were investigated. In addition, tar cracking capability and coke deposition resistance of Ni/MS catalyst and Ni/γ-Al 2 O 3 catalyst were explored under different calcination/catalytic bed temperatures. The catalysts were characterized by BET, XRD, SEM, TEM, TPO and Raman spectroscopy. The Ni/MS catalyst exhibited excellent catalytic reactivity as well as thermal stability. The best tar conversion (95.69%) and the highest hydrogen yield of 38.9 mmol/g biomass were obtained over Ni/MS catalyst under the conditions of Ni loading content = 3%, calcination/catalytic bed temperature = 800 °C, and S/C = 0.5. The interactions among Ni, Fe, Ca, and Mg formed multiple active centers (e.g., Ca 2 Fe 2 O 5 , (Ni, Mg) O solid solution and NiFe 2 O 4 ) in the catalyst to show synergistic catalysis effects, thereby jointly improving catalyst activity and coke deposition resistance. Furthermore, both amorphous carbon and graphitic carbon were formed on the used catalysts and the D/G ratio (the relative intensity ratio between the D and G bands) was positively correlated with the catalytic activity.
A novel magnesium slag (MS) supported nickel-based catalysts (Ni/MS) was prepared and tested in catalytic reforming of volatiles derived from the pyrolysis of biomass components (cellulose, hemicellulose and lignin) and two biomass feedstocks (pine and straw). The physical and chemical properties of catalysts were characterized by XRD, TPR, BET, TEM, TPO-TGA and Raman spectroscopy. Ni/MS catalyst showed a higher tar removal efficiency than conventional Ni/γ-Al 2 O 3 under the same Ni loading. The tar conversion of cellulose hemicellulose and lignin reached 94.8 %, 92.0 % and 89.4 %, respectively over Ni/MS catalyst. In addition, the lignin content of the biomass feedstock appreciably affected the yield and dew point of tar. The highest increment in gas and H 2 yield (increased by 39.0 % and 106.4 %, respectively) was observed in cellulose. The highest decrement in tar dew point (from 166.4 ℃ to 53.0 ℃) was observed in hemicellulose. The excellent tar removal of Ni/MS was attributed to the metallic Ni and Ni-Fe alloy on catalyst surface. Besides, the MgO and Fe 2 O 3 phases in the support can retard the carbon deposition during the reaction. The results of this study are expected to provide insightful guidance for the application of Ni/MS catalysts for pyrolysis/gasification of biomass.
Upgrading magnesium slag into value-added products provides a significant opportunity to address environmental waste pollution while promoting waste recycling. However, challenges such as the low catalytic activity of the resulting products and limited adsorption of macromolecular organic compounds at surface active sites remain critical engineering hurdles. In this paper, mesoporous g-C 3 N 4 /TiO 2 -MgAl 2 O 4 heterojunction photocatalysts were synthesized by a facile combustion method using magnesium slag, titanium dioxide, and carbamide as raw materials. Photocatalytic experiments on methylene blue solution under visible light irradiation at room temperature showed that the g-C 3 N 4 /TiO 2 -MgAl 2 O 4 heterojunction photocatalyst achieved a 25.6% higher degradation efficiency compared to traditional photocatalysts. This work provides a theoretical framework and practical experience for the value-added and low-cost preparation of photocatalytic materials derived from magnesium slag. Furthermore, a potential enhanced photocatalytic mechanism of g-C 3 N 4 /TiO 2 -MgAl 2 O 4 heterojunction photocatalysts is proposed.
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