Du Jingwei, Tian Lin, Qi Manfu, Zhang Chen, Di Hongfeng, Zhi Xiao, Zhu Jianping
School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 45400, Henan, China.
LB Group Co., Ltd, Jiaozuo 45411, Henan, China.
Sci Total Environ. 2023 Nov 1;897:166405. doi: 10.1016/j.scitotenv.2023.166405. Epub 2023 Aug 18.
Titanium gypsum (TG) is rarely used to produce α-hemihydrate gypsum (α-HH) because of its poor crystallinity and high impurity and moisture contents. Here, a method is proposed to prepare α - HH by adjusting the reaction temperature, CaCl solution concentration and maleic acid dosage based on acid leaching and heat-treated TG as raw material. The effect of maleic acid and Fe ions on the preparation of α-HH were systematically analyzed using density functional theory (DFT) and typical materials characterization methods, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Under the optimal conditions (CaCl concentration of 23 % and reaction temperature of 95 °C), the maleic acid is chemically adsorbed on the crystal surfaces of α-HH, the strongest adsorption is in the (111) surface. Increasing the maleic acid concentration from 0 to 0.15 % decreased the aspect ratio of the α-HH crystals from 8.26 to 0.96, respectively, where the optimal dosage was 0.1 %. The theoretical results proved that the substitution energy of Fe was greater than that of Ca, and Fe ions can spontaneously enter the α-HH lattice to replace Ca ions. Furthermore, the adsorption energy of maleic acid on the (111) surface increased after the substitution of Fe to generate a synergistic effect that hinders α-HH growth along the c-axis, resulting in the preferred morphology. The results of this study provide a new method for using waste TG to produce a high-value-added product.
钛石膏（TG）由于结晶度差、杂质和水分含量高，很少用于生产α-半水石膏（α-HH）。在此，提出了一种以酸浸和热处理后的TG为原料，通过调节反应温度、CaCl溶液浓度和马来酸用量来制备α-HH的方法。采用密度泛函理论（DFT）以及典型的材料表征方法，如X射线衍射（XRD）、扫描电子显微镜（SEM）和X射线光电子能谱（XPS），系统分析了马来酸和铁离子对α-HH制备的影响。在最佳条件下（CaCl浓度为23%，反应温度为95℃），马来酸化学吸附在α-HH的晶体表面，最强吸附发生在（111）面。将马来酸浓度从0提高到0.15%，α-HH晶体的长径比分别从8.26降至0.96，最佳用量为0.1%。理论结果证明，Fe的替代能大于Ca，Fe离子可自发进入α-HH晶格取代Ca离子。此外，Fe取代后马来酸在（111）面的吸附能增加，产生协同效应，阻碍α-HH沿c轴生长，从而形成择优形貌。本研究结果为利用废弃TG生产高附加值产品提供了一种新方法。
