Adsorption of Reactive Brilliant Red X-3B in Aqueous Solutions on Clay-Biochar Composites from Bagasse and Natural Attapulgite

The study aims to determine the adsorption mechanism of reactive brilliant red X-3B (RBR) on a novel low-cost clay-biochar composite with different proportions of bagasse and natural attapulgite (ATP). Pure bagasse, pure ATP, and two mixtures with weight ratios of 1:5 and 1:3 were pyrolyzed at 700 degrees C for 4 h in a muffle furnace. Biochar samples were characterized with an element analyzer and by scanning electron microscopy, X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller method, and zeta potential measurement. Results of the batch and leaching experiments showed that the adsorption capacities followed the order of 1:3 clay-biochar > 1:5 clay-biochar > bagasse biochar > pure ATP. Furthermore, ATP and bagasse exerted a synergistic effect on the adsorption of RBR. The adsorption data showed good correlation with the Langmuir isotherm, and the kinetic data were fitted to the pseudo-second-order model. The adsorption of RBR on clay-biochar involved electrostatic interaction, hydrogen bond, - interactions, and surface participation. The modification of biochar by ATP improved the adsorption capacity by increasing functional groups and creating adsorption sites. Therefore, ATP-modified clay-biochar composites could be effective adsorbents for the removal of RBR from wastewater.