Influence of acid activation on the NH3-adsorption properties of a Turkish bentonite

Abstract

In this study, the adsorption of NH3 gas on a bentonite from Unye (Turkey) in its natural state and after acid treatments, was investigated experimentally at 298 K and up to 100 kPa. Bentonite was treated with HCl solutions of various concentrations (0.5-2.5 M) at 75 degrees C for 4 h. X-ray diffraction (XRD), X-ray fluorescence (XRF), N-2 adsorption and thermogravimetric/differential thermal analysis (TG/DTA) were used to characterize the bentonite before and after acid treatment. The quantitative XRD analysis demonstrated that the bentonite sample was composed predominantly of smectite (75%), with abundant feldspar (20%) and minor opal-CT, analcime and quartz (5%). Increasing gas adsorption values of acid-treated bentonites were analysed depending on the structural changes of the clay. The NH3 adsorption capacities of the bentonite samples (3.801-5.068 mmol g(-1)) were also compared with previously studied clay-based materials (0.828-4.000 mmol g(-1)) in terms of their textural and structural differences.