Enhanced adsorption of as(V) from aqueous solution by mesoporous goethite: Kinetics, isotherms, thermodynamics, and mechanism

Abstract

As(V) adsorption capacity on mesoporous goethite was investigated and compared to common goethite. The mesoporous goethite synthesized by a hydrothermal method possessed the larger pore size and mesopore volume than common goethite. The kinetics, isotherms, thermodynamics, and As(V) adsorption mechanism on the mesoporous goethite were thoroughly studied. The kinetics data of As(V) adsorption on mesoporous goethite fitted well the pseudo-second-order equation, and the isotherm data fitted better with the Langmuir model. The maximum As(V) adsorption capacity of mesoporous goethite derived from the Langmuir model is 41.19 mg/g at 25°C, which is much higher than those of natural or modified goethite. The thermodynamic parameter (ΔG° and ΔH°) showed that the As(V) adsorption process was spontaneous and exothermic. The Fouriertransform infrared spectroscopy, Raman and X-ray photoelectron spectroscopy results revealed that the As(V) removal mechanism can be due to the surface complexation of As(V) and mesoporous goethite. These results show that the mesoporous goethite is a promising efficient and easy to prepare adsorbent for removal of As(V) from water.