Sasamoto Ryo, Kanda Yasuharu, Yamanaka Shinya
Department of Applied Sciences, Muroran Institute of Technology, 050-8585, Hokkaido, Japan.
Department of Applied Sciences, Muroran Institute of Technology, 050-8585, Hokkaido, Japan.
Chemosphere. 2022 Jun;297:134057. doi: 10.1016/j.chemosphere.2022.134057. Epub 2022 Feb 25.
Cadmium is adsorbed on calcium carbonate via chemisorption. All calcium carbonate polymorphs generate otavite (cadmium carbonate), indicating that the crystallographic differences in calcium carbonate should affect the chemisorption equilibrium and kinetics. This study investigates the influences of the polymorph and specific surface area on cadmium adsorption. Here, we synthesise two polymorphs of porous calcium carbonate: calcite and vaterite with a wide range of specific surface areas. Then the equilibrium of cadmium adsorption is evaluated using adsorption isotherm models. Based on the Langmuir model with linear regression analysis, the maximum adsorptions of porous calcite and vaterite particles are 287.8 mg/g and 883.5 mg/g, respectively. The kinetics of cadmium chemisorption show clear differences between polymorphs. The calculated rate constant of the porous calcite particles using a pseudo-second-order reaction and Elovich models are two orders larger than that of porous vaterite particles. Although the adsorbed amount is superior for porous vaterite particles, porous calcite particles exhibit a faster reaction and relatively high adsorbed capacity for cadmium ions.
镉通过化学吸附作用吸附在碳酸钙上。所有碳酸钙多晶型物都会生成菱镉矿（碳酸镉），这表明碳酸钙的晶体学差异会影响化学吸附平衡和动力学。本研究调查了多晶型和比表面积对镉吸附的影响。在此，我们合成了两种具有广泛比表面积的多孔碳酸钙多晶型物：方解石和球霰石。然后使用吸附等温线模型评估镉吸附的平衡。基于线性回归分析的朗缪尔模型，多孔方解石和球霰石颗粒的最大吸附量分别为287.8 mg/g和883.5 mg/g。镉化学吸附的动力学在多晶型物之间表现出明显差异。使用伪二级反应和埃洛维奇模型计算的多孔方解石颗粒的速率常数比多孔球霰石颗粒的速率常数大两个数量级。尽管多孔球霰石颗粒的吸附量更高，但多孔方解石颗粒对镉离子表现出更快的反应速度和相对较高的吸附容量。
