Adsorption of methylene blue from aqueous solution by attapulgite clay
凹凸棒粘土对水中亚甲蓝的吸附性能

The purified attapulgite (ATP) was modified by hydrochloric acid and sodium pyrophosphate, which was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectra. The adsorbent was successfully used to remove cationic dye methylene blue (MB) from an aqueous solution. Operating variables studied were pH, initial dye concentrations, temperatures, contact time and ionic strength. The adsorption process was found to exothermic for MB in nature. The experimental data were described by Langmuir and Freundlich isotherms, and found that the data fitted well to the Langmuir model with maximum monolayer uptake capacity of 114.02 mg/g at 303 K. The adsorption process followed the pseudo-second-order kinetic model. Compared with other adsorbents reported, the attapulgite clay has a faster adsorption rate and a higher adsorption capacity. Consequently, ATP may be employed as low-cost alternative adsorbent to remove MB from aqueous solutions.