Evaluation of methylene blue removal by plasma activated palygorskites

Abstract

Clay minerals with fibrous morphology, such as palygorskite, have been applied as adsorbents to remove pollutants from the environment and reduce toxic compounds, such as dye, in aquatic media. Although natural palygorskite has good dye removal performance, chemical modification can improve its adsorption sites and desired properties. In this study, palygorskite was activated in H2/N2 plasma flow for 2, 4, and 6 h to produce new adsorbents for the removal of methylene blue (MB). The solids were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, scanning electron microscopy (SEM) coupled to dispersive energy X-ray spectrometry and nitrogen adsorption/desorption measurements. The plasma technique induced structural defects in the palygorskite by the removal of coordinated and zeolitic water molecules, which altered the palygorskite’s specific surface area and pore volume. The adsorption capacity of the activated plasma samples for the removal of MB increased from 35.66 in the natural palygorskite to 54.17 mg g−1 in the activated samples.