Synthesis and characterization of Cr-pillared clays: modelling using factorial design methodology

Abstract

Cr-pillared interlayered clays (Cr-PILCs) have been prepared from natural calcium bentonite originating from a Romanian deposit and the effect of some parameters on the chemical and textural properties have been investigated. The crude bentonite and the derived materials were characterized by nitrogen adsorption–desorption technique, X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and transmission electron microscopy. The specific surface area values, the pore size distribution, morphological characteristics and the basal spacing of the Cr-PILCs are strongly affected by the process parameters. The influence of three relevant factors (metal/clay ratio, calcination temperature and calcination duration) on the specific surface areas of the Romanian Cr-PILCs was investigated using a 33 factorial design methodology. The optimum conditions to obtain Cr-PILCs with a specific surface area of 183 m2/g (more than four times higher than the raw material) were as follows: metal/clay ratio of 10 mmols/g, calcination temperature 300 °C and calcination duration 60 min. The model developed in this paper predicts very well the experimental results. Due to the high porosity and adsorption properties, the prepared Cr-PILCs have great potential in remediation of industrial liquid effluents.