Green synthesis of lignocellulose/silica hybrid materials from rice husk and bagasse and their adsorption properties

Abstract

The mesoporous lignocellulose/silica hybrids from rice husk and bagasse were prepared using the sol-gel method. The surface area and pore volume of these mesoporous lignocellulose/silica hybrids were increased compared to the raw rice husk and bagasse. These lignocellulose/silica hybrid materials can potentially be used for the removal of Congo red dye from aqueous solutions. Based on the experimental observation of consistently high adsorption over a wide pH range, the predominant adsorption mechanism for Congo red on these mesoporous lignocellulose/silica hybrid adsorbents is likely a combination of physical entrapment, strong hydrophobic interactions and H-bonding. The results of the adsorption kinetics of Congo red showed that the pseudo-second order kinetic equation can well explain the kinetic behavior of the adsorption of Congo red. The equilibrium adsorption isotherms of Congo red on the lignocellulose/silica hybrids could be described by the Langmuir model. The lignocellulose/silica hybrid prepared from bagasse showed higher adsorption capacity (61.50 mg/g) than the lignocellulose/silica hybrid prepared from rice husk (58.82 mg/g). The thermodynamic analysis showed that the adsorption of Congo red on the adsorbent is spontaneous and endothermic. Furthermore, these adsorbents exhibit good recyclability and stability.