草酸对珊瑚砂的溶蚀作用及其机制研究

doi:10.19741/j.issn.1673-4831.2019.0229

摘要/Abstract

摘要： 营造热带吹填陆域的宜居生态环境，构建植被生态系统必不可少，其中，研究植被分泌小分子有机酸对岛礁母质珊瑚砂的风化作用对于岛礁生态建设至关重要。通过研究不同浓度草酸对珊瑚砂的溶蚀动力学，建立动力学模型，研究珊瑚砂溶蚀的主要影响因素，探讨草酸对珊瑚砂的溶蚀机制。结果表明，在不同草酸溶液中，反应初始阶段珊瑚砂中Ca²⁺、Mg²⁺迅速溶出，随后大量Ca²⁺被草酸固定生成草酸钙沉淀。随着草酸浓度的增加，溶液中Ca²⁺浓度逐渐降低，Mg²⁺浓度逐渐升高，c（Ca²⁺）最大值为0.65 mmol·L^-1，c（Mg²⁺）最大值为2.87 mmol·L^-1。通过Mg²⁺溶出动力学拟合发现其溶出动力学符合Stumm模型，主要受扩散过程的影响。此外，高浓度草酸会抑制珊瑚砂中Ca²⁺的溶解流失。XRD和SEM分析结果表明，高浓度草酸与珊瑚砂反应生成草酸钙沉淀相互胶连附着在珊瑚砂表面，且溶蚀过程中优先溶蚀珊瑚砂组分中镁方解石，其次是文石和方解石。

关键词: 珊瑚砂, 草酸, 溶蚀, 动力学, 草酸钙

Abstract: A vegetation ecosystem is essential to maintain a livable environment in a tropical reclamation land. In this paper, kinetics of coral corrosion in the presence of the different concentration of oxalic acid was studied. According to the kinetic model established, main factors affecting corrosion of coral sand were elucidated. The results show that Ca²⁺ and Mg²⁺ in the coral sand were rapidly dissolved during the beginning stage of the reaction, followed by the fixation of a large amount of Ca²⁺ by oxalate to form calcium oxalate precipitate. As the concentration of oxalic acid increased, the concentration of Ca²⁺ in the solution gradually decreased and the concentration of Mg²⁺ gradually increased. The maximum concentrations of Ca²⁺ and Mg²⁺ were 0.65 and 2.87 mmol·L^-1, respectively. The corrosion kinetics of Mg²⁺ was fitting with Stumm model, indicating this process was mainly governed by diffusion. In addition, dissolution and loss of Ca²⁺ in coral sand was inhibited at high concentration of oxalic acid. The results of XRD and SEM show that the calcium oxalate precipitates formed by the reaction of high concentration oxalic acid are attached onto the surface of coral sands, and magnesian calcite is preferentially dissolved, followed by aragonite and calcite.

Key words: coral sand, citric acid, dissolution, kinetics, calcium oxalate

中图分类号:

X13
P579

李越煊, 李鹏飞, 潘杰, 刘云, 王萍, 董元华. 草酸对珊瑚砂的溶蚀作用及其机制研究[J]. 生态与农村环境学报, 2020, 36(7): 905-913.

LI Yue-xuan, LI Peng-fei, PAN Jie, LIU Yun, WANG Ping, DONG Yuan-hua. Study on the Corrosion of Coral Sand by Oxalic Acid.[J]. Journal of Ecology and Rural Environment, 2020, 36(7): 905-913.

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