Removal performance and adsorption behaviour on Mg-based adsorbents in As(III) and F simultaneous removal as in comparison with As(V)

Abstract

In this study, simultaneous removal tests, with fixed initial arsenic (As) concentration of 1 mg l −1 , for arsenite [As(III)] and fluoride (F) were performed using three types of Mg-based adsorbents. Their As(III) removal performance was of the order of MgCO 3 << Mg(OH) 2 < MgO. MgO met the environmental standards for As (0.01 mg l −1 ) at initial F concentrations ( C F0 ) of 15 and 30 mg l −1 . MgO and Mg(OH) 2 met the As effluent standard (0.1 mg l −1 ) even at C F0 = 60 mg l −1 . In contrast, MgCO 3 did not meet the effluent standards under the test conditions. The F removal performance of the Mg-based adsorbents followed the order of MgCO 3 < Mg(OH) 2 < MgO. MgO and Mg(OH) 2 met the environmental standard of F (0.8 mg l −1 ), whereas MgCO 3 met the effluent standards for F in non-marine areas (8 mg l −1 ) at C F0 = 15 and 30 mg l −1 , and in marine areas (15 mg l −1 ) even at C F0 = 60 mg l −1 . The As(III) adsorption data fit the Langmuir model for MgO and the Freundlich model for MgO and Mg(OH) 2 , but not MgCO 3 for either model. Notably, the As(III) adsorption behaviour of MgO was strongly influenced by C F0 . Meanwhile, the F adsorption data fit both the Langmuir and Freundlich models for all Mg-based adsorbents.