An efficient Egeria najas-derived biochar supported nZVI composite for Cr(VI) removal: Characterization and mechanism investigation based on visual MINTEQ model

Egeria najas is a submerged aquatic plant, and the literatures on resourcification of submerged aquatic plant biochar remain limited. Until now, there has been no study on submerged aquatic plant biochar supported nZVI that is widely applied for removal of diversified contaminants in solution. In this study, an efficient approach to the preparation of Egeria najas-derived biochar supported nZVI composite is first developed for Cr(VI) removal in wastewater. The adsorption behavior and mechanism of Cr(VI) removal on the as-prepared Egeria najas-derived biochar/nZVI ([email protected]) composite were investigated. The results of FTIR and XPS indicate that the [email protected] surface had many functional groups such as R-COOH, R-OH, R-NH2 and R-C-O-C, etc, which could provide active sites during the adsorption process. The BET results showed that the [email protected] had large specific surface area and average pore, which were 142.49 m2/g and 9.85 nm, respectively. [email protected] demonstrated high reactivity for Cr(VI) removal. Compared with nZVI, Cr(VI) removal efficiency by [email protected] is 50% higher than that of nZVI within 0.5 h. Furthermore, the maximum adsorption capacity of Cr (VI) was 56.79 mg/g and the energy of activation (Ea) was 31.30 kJ/mol. The adsorption process was well described by the pseudo-second order model and Sips adsorption isotherm model. The reaction mechanism of Cr(VI) removal was a multi-step removal mechanism, involving adsorption, surface complex formation, reduction and ion exchange reaction.