Equilibrium modeling of As(III,V) sorption in the absence/presence of some groundwater occurring ions by iron(III)–cerium(IV) oxide nanoparticle agglomerates: A mechanistic approach of surface interaction

Abstract

Here, we aim to develop an efficient material by eco-friendly green synthetic route that was further characterized to be crystalline ranging in nano-dimension for filtering high arsenic content groundwater. The thermal stability of iron(III)–cerium(IV) mixed oxide nanoparticle agglomerates (NICMO) was well established from the consistent particle size at different temperature and also from differential thermal analysis. The bimetal mixed oxide contained agglomerated crystalline nano-particles of dimension 10–20nm held together by crystal packing forces, and its corresponding empirical composition was FeCe1.1O7.6. Appearance of a weak band at 534cm−1 in the spectrum of nano-structured iron(III)–cerium(IV) mixed oxide (NICMO) is presumed for the presence of hetero-metal bonding via oxygen linkage (i.e., Fe–O–Ce). Equilibrium sorption data described Langmuir and D-R isotherm equations fairly well particularly for As(III) with relatively high monolayer sorption capacity [55.513mgg−1 for As(V), 86.293mgg−1 for As(III)] in the absence of any foreign ions. Chemo-sorption is the actual nature of the reaction taking place in As(III) with the sorption process getting more favorable with the increase of temperature in contrast to As(V) in which the degree of interaction suggested physiosorption type reactions. Splitting of band in FTIR spectrum of As(V) suggested the dominance of mono protonated monodentate complex [S-OAsO2(OH)] on the oxide surface. As(III) sorption mechanism taking place over NICMO surface under sufficient time lag confirmed oxidation of surface adsorbed As(III) to As(V) in a thermodynamically controlled sorption reaction.