Adsorption Characteristics of Ge(Ⅳ) by Root Cell Walls of Large-leaf Tea Plant
Germanium(Ge)-rich Large-leaf Tea has gained widespread attention due to its potential nutritional and health benefits.The root cell walls serve as the primary barrier for germanium uptake into the tea plant,making the study of its adsorption mechanism scientifically significant.In soil solution,germanium primarily exists in the form of Ge(Ⅳ).To better understand the germanium absorption mechanism in Large-leaf Tea roots and enhance its phytoavailability,this study investigates the kinetics and thermodynamics of Ge(Ⅳ)adsorption by tea root cell walls.The results indicated that the adsorption of Ge(Ⅳ)by the root cell walls follows a pseudo-second-order kinetic model(R2＞0.99),suggesting that chemisorption is the primary controlling step.Within the temperature range of 298 K to 313 K,the adsorption process showed a higher degree of conformity with the Langmuir model,indicating a monolayer adsorption characteristic,which may imply homogeneous adsorption.Thermodynamic analysis revealed that the adsorption process is spontaneous(△G0＜0),endothermic(△H0＞0),and entropy-driven(△S0＞0),with a maximum adsorption capacity exceeding 2 mg/g.Infrared spectroscopy analysis indicated that Ge(Ⅳ)likely forms complexes or chemical bonds with phenolic structures in lignin or aromatic compounds on the cell wall,and also chemically adsorbs with oxygen-containing functional groups in lignin,hemicellulose,and polysaccharides,forming Ge-O bonds.This study provides a theoretical basis for understanding the mechanism of Ge(Ⅳ)uptake by tea root systems and its application in the environment.It also offers theoretical support for enhancing the plant availability of Ge in large-leaf tea and for the development of Ge-rich tea research.
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