The Application of Adsorption Modeling and Fourier Transform Infrared Spectroscopy to the Comparison of Two Species of Plant Growth-Promoting Rhizobacteria as Biosorbents of Cadmium in Different pH Solutions

摘要

Batch experiments were performed to determine the cadmium absorption capacity of two plant growth-promoting rhizobacteria at different pH levels and in different cadmium concentrations. Comparison of the mean metal removal from two species of bacteria studied showed that Pseu-domonas florescence is the superior species for removing cadmium at all cadmium concentrations. The maximum cadmium absorption by P. florescence and P. putida were at 5 mg/L of cadmium concentration in pH 6 and 7, respectively. The applicability of the Langmuir and Freundlich isotherm models was surveyed. Comparison of two isotherm parameters (Q_m and a) further confirmed that P. fluorescence was better at binding cadmium ions (52.6 and 7.7 mg/g, respectively). Adsorption reaction also was considered by Fourier transform infrared (FTIR) spectroscopy. The FTIR analysis implied that the principal functional sites in the bacterial cell walls were phosphoryl and hy-droxyl, carboxyl, amide Ⅰ, amide Ⅱ, and amine groups.