Lanthanum- and cerium-based functionalization of chars and activated carbons for the adsorption of fluoride and arsenic ions

Abstract

This manuscript reports the study of lanthanum- and cerium-based surface functionalization of activated carbons and chars, prepared from a lignocellulosic-based precursor, for facing the geogenic water pollution caused by fluoride and arsenic (V) ions. The incorporation of these rare elements on the adsorbents increased the adsorption capacities up to 2537% especially for arsenic (V). Chars and activated carbons functionalized with lanthanum and cerium showed adsorption capacities of 1.3–9.2 mg/g and 0.1–9.2 mg/g for fluoride and arsenic (V) ions, respectively. However, the adsorbents with lanthanum functional groups were the best for the removal of these hazardous water pollutants. A detailed physicochemical characterization of the adsorbents was utilized to explain their adsorption properties. Results showed that a ligand exchange of OH− from adsorbent surfaces and the presence of electrostatic forces could be associated to the adsorption mechanism of fluoride and arsenic (V) ions. Simultaneous adsorption of fluoride and arsenic (V) ions was antagonistic using lanthanum-modified adsorbents where fluoride ion reduced significantly the removal of arsenic (V) species. Therefore, new findings are reported for the tailoring of surface chemistry of chars and activated carbons for reducing the risks caused by geo-environmental hazardous chemicals dissolved in water.