Potassium nickel(II) hexacyanoferrate(III)-functionalized biochar for selective separation of radiocesium from liquid wastes

Abstract

Biochar is a promising metal-immobilizing material, nevertheless the studies of its modification and application in the removal of radionuclides, especially 137 Cs from contaminated liquids remain rare. This research demonstrated that horticultural waste derived biochar (GWB) produced by slow pyrolysis process could be a suitable Cs adsorbent and also useful support to impregnate the potassium nickel(II) hexacyanoferrate(III) (KNi-HCF). Porous materials combining sorption properties of biochar carrier and KNi-HCF have been prepared using simple and efficient impregnation method. The obtained materials (GWB, KNi-HCF-GWB1, and KNi-HCF-GWB2) have been characterized using N 2 adsorption method, SEM-EDX, and FTIR analysis. Compared to GWB, both KNi-HCF biochars showed improved adsorption properties toward Cs + ions, e.g. rapid kinetics, high Cs adsorption capacities (140 ± 3 μmol g −1 for KNi-HCF-GWB1 and 290 ± 9 μmol g −1 for KNi-HCF-GWB2), and high K d values even in the presence of excess of monovalent (Na + + K + + NH 4 + ) and divalent (Ca 2+ + Mg 2+ + Sr 2+ ) cations. High adsorption capacities could be related to synergistic effects of Cs + ion-exchange with KNi[Fe(CN) 6 ] structure and other mechanisms described for unmodified GWB. Rapid adsorption kinetics and high Cs adsorption capacity indicate the suitability of KNi-HCF biochars to treat large volumes of 137 Cs contaminated liquids.