南湖新闻网讯（通讯员 张怡）近日，我校生物地质矿化研究课题组针对纳米尺度粘土界面上磷素的界面行为和物质循环这一课题开展系统深入的研究，相关成果分别以“Adsorption effects and mechanisms of phosphorus by nanosized laponite”和“Molecular mechanisms of phosphorus immobilization by nano-clay mediated by dissolved organic matter”为题发表在Chemosphere和Chemical Geology上。
Phosphorus (P), an important macroelement for crops, may be lost into water systems by human activities and subsequently cause serious environmental problems such as eutrophication. Thus, the recovery of P from wastewater is essential. P can be adsorbed and recovered from wastewater using many natural, environmentally friendly clay minerals, however the adsorption ability is limited. Here we applied a synthesis nanosized clay mineral, laponite, to evaluate the P adsorption ability and molecular mechanisms of the adsorption process. We apply X-ray Photoelectron Spectroscopy (XPS) to observe the adsorption of inorganic phosphate onto laponite, and then measure the adsorption content of phosphate by laponite via batch experiments in different solution conditions, including pH, ionic species and concentrations. Then the molecular mechanisms of adsorption are analyzed by Transmission Electron Microscopy (TEM) and molecular modeling using Density Functional Theory (DFT). The results show that phosphate adsorbs to the surface and interlayer of laponite via hydrogen bonding, and the adsorption energies of the interlayer are greater than those of the surface. These bulk solution and molecular-scale results in a model system may provide new insights into the recovery of phosphorus by nanosized clay, with possible environmental engineering applications for P-pollution control and sustainable utilization of P sources.
The adsorption of phosphorus (P) by minerals, particularly clay minerals, plays a crucial role in the biogeochemical cycling of P in geological environments such as soil and groundwater. However, the mechanisms underlying the immobilization and subsequent release of element P by nano-clay are still not well comprehended. This study delves into the mechanism of adsorption of inorganic phosphate and organic phytate onto laponite, serving as a representative nano-clay. This aspect has frequently been disregarded due to research method limitations; nevertheless, the substantial specific surface areas (SSA) are abundant in a multitude of potential adsorption sites. Batch experiments were conducted to evaluate surface reaction and adsorption capacity under varying solution conditions, including pH, ionic strength, and the presence of dissolved organic matter (DOM). The results demonstrate that the adsorption capacity of laponite decreases with increasing pH. Additionally, the adsorption capacity initially increases within the range of 10-50 mM NaCl and then decreases within 50-100 mM NaCl, while the presence of DOM significantly inhibits P adsorption. Complementary techniques such as X-ray photoelectron spectroscopy (XPS), zeta potential analysis, atomic force microscopy (AFM) were employed to gain further insights into the adsorption process. These analyses revealed that DOM obstructs P adsorption by occupying adsorption sites and promoting the aggregation of laponite nanoparticles. Furthermore, AFM-based dynamic force spectroscopy (DFS) provides molecular-scale thermodynamic support for the observed P adsorption phenomena on laponite under different conditions. The findings of this study contribute to a better understanding of the P adsorption mechanism of nano-clay and have valuable implications for the biogeochemical cycling of P in soil and groundwater.