Polyethylenimine functionalized Fe3O4/steam-exploded rice straw composite as an efficient adsorbent for Cr(VI) removal.

Polyethyleneimine functionalized Fe 3 O 4 /steam-exploded rice straw composite (Fe 3 O 4 -PEI-SERS), which combines magnetic separation with adsorption of PEI functionalized biosorbent, was successfully prepared via a simple glutaraldehyde crosslinking method. Its adsorption potential for the removal of Cr(VI) was systematically studied in batch mode. Results showed that Cr(VI) adsorption on Fe 3 O 4 -PEI-SESERS was highly pH-dependent, and the optimum pH was 2.0. The time to reach equilibrium was related to initial Cr(VI) concentration and was 1 and 6 h for 200 and 300 mg/L of Cr(VI), respectively. The adsorption system followed pseudo-second-order kinetic model and Langmuir isotherm. Its maximum adsorption capacity was 280.11, 317.46 and 338.98 mg/g at 25, 35 and 45 °C, respectively. The competitive uptake from coexisting ions (K + , Na + , Cu 2+ , Cl − and NO 3 − ) was insignificant except SO 4 2− . After six adsorption/desorption cycles, the adsorbent retained good adsorption capacity. The Cr(VI) removal involved its partial reduction into Cr(III). Due to the properties of high adsorption capacity, strong magnetic responsiveness, good reusability and Cr(VI) detoxification, the Fe 3 O 4 -PEI-SESERS has a potential application in Cr(VI) removal from wastewater. [ABSTRACT FROM AUTHOR]