磷酸根在矿物表面的吸附-解吸特性研究进展

综述了磷酸根在一些常见土壤矿物表面吸附–解吸特性的研究进展。磷酸根在矿物表面的吸附特性受环境pH、离子强度、温度、反应时间、矿物类型等多种因素的共同影响。一般说来,矿物表面的磷吸附量随pH降低而增加,受离子强度的影响较小。磷酸根在矿物表面的吸附动力学过程可分为快速吸附过程和慢速吸附过程,且在弱结晶矿物中存在微孔扩散过程。磷酸根在矿物表面的解吸过程通常存在两个阶段(初始快速解吸和随后的缓慢解吸),在解吸反应后期甚至还会发生再吸附。此外,磷酸根的吸附特性也受共存阴离子配体或金属阳离子的影响。其中,共存阴离子通过位点竞争、静电作用和空间位阻效应等机制影响磷酸根的吸附。天然有机质(包括胡敏酸和富里酸)降低了磷酸根在矿物表面的吸附,特别是在低p H条件下。通常,富里酸比胡敏酸更能有效降低磷酸根在矿物表面的吸附。金属阳离子可通过表面静电效应、形成三元络合物以及形成表面沉淀等机制促进磷酸根和金属在矿物表面的共吸附。最后,展望了与磷酸根在矿物表面吸附特性有关的研究热点和方向。

Research Progresses on Sorption and Desorption Characteristics of Phosphate on Minerals

Phosphorus is an essential nutrient for plant growth and a key element in relation to the biological and abiotic effects of ecosystems. The adsorption, desorption and precipitation of phosphate on the surface of minerals affect and determine its speciation, migration, transformation and bioavailability in terrestrial and aquatic environments. The research progress of phosphate sorption and desorption on common soil minerals are reviewed. The sorption characteristics of phosphate on mineral surface are affected by pH, ionic strength, temperature, reaction time, mineral type, and so on. Generally, the amount of phosphate adsorbed on the surface of mineral increases with decreasing pH and is less affected by ionic strength. The sorption kinetics of phosphate on the mineral surface can be divided into rapid sorption and slow sorption processes, and microporous diffusion processes exist on weakly crystalline minerals. Phosphate desorption on mineral surface usually has two stages (initial rapid desorption and subsequent slow desorption), and even re-sorption occurs in the later stage of desorption reaction. In addition, coexistence of anions or metal cations in multiple systems also affects the sorption of phosphate on minerals. Coexisting anions (ligands) affect phosphate sorption through site competition, electrostatic interaction and steric hindrance. The sorption of phosphate on minerals?is decreased by the presence of natural organic matter (e.g., humic acid and fulvic acid), especially at low pH. In general, the effects of the fulvic acid are more effective than humic acid in reducing phosphate sorption on minerals. When metal cations coexist, the sorption of phosphate and metal on the mineral surface could be promoted by surface electrostatic effects, formation of ternary complexes, and formation of surface precipitates. Finally, hot spots are proposed for future researches related to the sorption of phosphate on mineral surfaces.