Preparation and characterization of modified bentonite nano composites for phosphorus removal

Abstract

Due to the restrictions of phosphorus uptake in commonly applied treatment systems such as biological treatment and precipitation, it has been focused to find improved removal technologies. The application of natural nanomaterials as adsorbents is favorable due to high adsorption capacity, low environmental impact and reasonable cost. Specially modified nanoclay presents an efficient and cheap alternative with good recovery abilities. However, the material has to be characterized in detail to understand its behavior. For the characterization, modified bentonite (BNT) was produced through exchanging the cations naturally bound to the bentonite surface with metal polycations. In this study, solutions containing hydroxy-polycations of aluminum (Al-BNT), iron (Fe-BNT), and a combination of aluminum and iron (Al-Fe-BNT) were used to prepare three samples of BNT for phosphorus adsorption. To obtain BNT in an accurate surface - volume ratio, it has to be grinded and sieved. To gain information on the influence of grinding on particle size of modified BNT, the samples were characterized through X-ray fluorescence (XRF), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). A clear determnation of particle size using SEM was difficult due to agglomeration of samples as a result of milling process. The need of ultrasonication or another separation method increases the production effort of nanosized modified BNT. As due to the improved surface - volume ratio, BNT with smaller mean particle size is expected to perform better, leading to a higher adsorption capacity and adsorption rate and therefore, this additional effort might pay off.