Development of a high efficiency rice husk based adsorbent for removal of dyes from wastewater: application to Everzol Black GR and Reactive Orange 113

Rice husk is a type of bio-waste that is easily available and provides a base for formation of an effective adsorbent along with chitosan. ZnO-coated chitosan carbonized rice husk (ZnO-CCRH) was prepared by blending Zn-loaded chitosan with rice husk. The adsorbent was then applied to remove color from wastewater. Different isothermal, kinetic and thermodynamic models were applied to evaluate adsorbent efficiency. Results showed that adsorption capacity for two dyes Everzol Black Gr (EBG) and Reactive Orange 113 (RO113) onto ZnO-CCRH was best described by the Langmuir model. Adsorption appeared to follow the mono layer adsorption mechanism, likely because the adsorbent (ZnO-CCRH) has heterogeneous surfaces. In case of adsorption kinetics,results indicated that the pseudo-second-order kinetic model best described the adsorption of EBG and RO 113 onto ZnO coated chitosan carbonize rice husk. Furthermore, thermodynamic studies also revealed exothermic adsorption process for the said dyes. The adsorbent was further characterized by FTIR, SEM and X-Ray diffraction. Results of the characterization indicated that the ZnO-CCRH adsorbent has a strong potential for color removal. Keywords: Carbonized rice husk; Adsorption modeling; Chitosan; Reactive dyes; Wastewater