▎ 摘　　要

Graphene oxide chitosan composite (GOCS) is recognized as an environmentally friendly composite adsorbent because of its stability and abundant functional groups to adsorb heavy metals, and Fe-Mn binary oxides (FMBO) have attracted increasing interest due to their high removal capacity of As(III). However, GOCS is often inefficient for heavy metal adsorption and FMBO suffers poor regeneration for As(III) removal. In this study, we have proposed a method of dopping FMBO into GOCS to obtain a recyclable granular adsorbent (Fe/Mn-GOCS) for achieving As(III) removal from aqueous solutions. Characterization of BET, SEM-EDS, XRD, FTIR, and XPS are carried out to confirm the formation of Fe/Mn-GOCS and As(III) removal mechanism. Batch experiments are conducted to investigate the effects of operational factors (pH, dosage, coexisting ions, etc.), as well as kinetic, isothermal, and thermodynamic processes. Results show that the removal efficiency (R-e) of As(III) by Fe/Mn-GOCS is about 96 %, which is much higher than those of FeGOCS (66 %), MnGOCS (42 %), and GOCS (8 %), and it increases slightly with the increasing molar ratio of Mn and Fe. This is because amorphous Fe (hydro) oxides (mainly in the form of ferrihydrite) complexation with As(III) is the major mechanism to remove As(III) from aqueous solutions, and it is accompanied by As(III) oxidation mediated by Mn oxides and the complexation of As(III) with oxygen-containing functional groups of GOCS. Charge interaction plays a weaker role in As(III) adsorption, therefore R-e is persistently high over a wide range of pH values of 3-10. But the coexisting PO43- can greatly decrease R-e by 24.11 %. As(III) adsorption on Fe/Mn-GOCS is endothermic and its kinetic process is controlled by pseudo-second-order with a determination coefficient of 0.95. Fitted by the Langmuir isotherm, the maximum adsorption capacity is 108.89 mg/g at 25 degrees C. After four times regeneration, there is only a slight decrease of <10 % for the R-e value. Column adsorption experiments show that Fe/Mn-GOCS can effectively reduce As(III) concentration from 10 mg/L to <10 mu g/L. This study provides new insights into binary polymer composite modified by binary metal oxides to efficiently remove heavy metals from aquatic environments.