Synthesis of glutamic acid-modified magnetic corn straw: equilibrium and kinetic studies on methylene blue adsorption

摘要

Magnetic corn straw (MCS) was prepared by glutaraldehyde cross-linking, and the resulting MCS was chemically modified with glutamic acid to synthesize glutamic acid-modified MCS (GMCS). GMCS was investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy, and potentiometric titration. The results reveal that nano-Fe_3O_4 was stably cross-linked with the corn straw, and the carboxyl on the MCS surface was modified. GMCS was used for the adsorption of methylene blue (MB). Several factors affecting MB adsorption on MCS and GMCS, namely, pH, contact time, initial MB concentration, and reaction temperature were investigated. The adsorption capability of GMCS for MB was observed to be superior to that of MCS. The maximum adsorption capacity of GMCS for MB (196.46 mg g~(-1)) was attained with an initial MB concentration of 300 mg L~(-1) at pH 6.0 and 60 ℃ for a contact time of 60 min. The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm equation. Desorption and regeneration experiments were conducted, and the recovery efficiencies were maintained between 90 and 70% using absolute ethanol as eluent.