Incorporation of active phases of iron and bone char in clay ceramic monolith for arsenic removal from aqueous solutions

Abstract

Clay-based monoliths with incorporation of active phases derived from the waste of the metallurgical and livestock industries (powdered iron and bone meal) and composite with both raw materials were synthesized by the extrusion process and used as adsorbents in the As(V) removal from aqueous solutions. These monoliths exhibited excellent mechanical properties compared to commercial ceramic-based monoliths, with potential for their use in continuous systems due to ease of handling and extraction of the adsorption medium (i.e., packed bed) and having defined meso and macroporosity. Specifically, the clay-based monoliths were obtained along with (i) active iron phases (hematite and magnetite), (ii) bone char and (iii) a combination of both materials. They showed As(V) adsorption capacities of up to 0.56, 3.4 and 8.0 mg g−1 at neutral pH and room temperature conditions. The proposed adsorption mechanism was associated with ligand exchange between the As(V) species and the hydroxyl functional groups, in addition to the presence of inner-sphere bidentate unprotonated arsenate surface complexes that was reflected in the formation of new absorption bands in Fourier Transform Infrared Spectroscopy spectra related to the Metal-O interaction and changes in the bands associated with the -OH groups. The SIPS isotherm model fitted the experimental data obtained at equilibrium and was related to strong adsorbent/adsorbate interactions and high surface heterogeneity. Finally, the composite ceramic monolith synthesized in the present study exhibits capabilities comparable to those reported in the literature, highlighting the low cost of raw materials, as well as its excellent mechanical properties and well-defined porosity.