Removal of arsenate from drinking water with a natural manganese oxide in the presence of competing anions

Abstract

The efficiency of arsenic removal from drinking water in adsorption processes using natural oxides may be influenced by the presence of other adsorbable anions. The present paper focuses on the study of arsenate adsorption by a natural manganese oxide. The objective is to determine which of the anions usually present in drinking water may be adsorbed: hydrogen carbonate, sulfate, chloride, nitrate, phosphate and arsenate. A kinetic batch experiment was conducted with a natural drinking water, leading to a first qualitative selection: nitrate and chloride have little interaction with the adsorbent, sulfate and hydrogen carbonate are adsorbed while phosphate and arsenate are strongly adsorbed. Then column experiments were run with aqueous solutions containing either chloride, sulfate, etc. The previous trends were confirmed and the equilibrium isotherms of the adsorbable anions were built by integration of the breakthrough curves. The isotherms fitted with a Langmuir model showed that the capacitieswere low (a few μmol.g-1). The affinity order was determined from the isotherm initial slopes: arsenate ≫ phosphate > hydrogen carbonate ≌ sulfate. Given the strong affinity of the adsorbent for arsenate and the low arsenate concentration in drinking water, the process selectivity for As traces from drinking water is ensured.

Diffusion-Controlled Adsorption of Arsenate on a Natural Manganese Oxide

“…This shape showed that the system was not at equilibrium. As a matter of fact, arsenic adsorption is favorable; it is described by a Langmuir isotherm with a steep slope at the origin. Thus, the arsenic breakthrough curve at equilibrium should be stiff.…”

“…Parameters were estimated as follows: K L and q max were taken from previous measurements of adsorption isotherms, D L was obtained by tracing experiments, and D e was adjusted to reach a good fitting between experimental and computed arsenic breakthrough curves.…”

“…As(III) is oxidized at the oxide surface into As(V), and As(V) is adsorbed. − Previous studies showed their efficacy for the selective removal of traces of arsenic from drinking waters. Arsenate adsorption at equilibrium has been investigated . At the vicinity of neutrality, arsenate adsorption was highly favored and not disturbed by the major anions of drinking water, such as bicarbonate, sulfate, and chloride.…”

“…Arsenate adsorption at equilibrium has been investigated. 8 At the vicinity of neutrality, arsenate adsorption was highly favored and not disturbed by the major anions of drinking water, such as bicarbonate, sulfate, and chloride. However, the understanding of adsorption at equilibrium may not be sufficient to design a treatment process because of mass-transfer limitations may have a significant impact on the process efficacy.…”

Sono-sorption as a new method for the removal of lead ion from aqueous solution

“…There are several methods for removing lead contaminant from effluents such as ion exchange, chemical precipitation, oxidation and reduction, reverse osmosis and sorption methods [6][7][8][9][10][11][12]. In the last method, different sorbents have been used such as fly ash [13], activated carbon [14], natural surface coating [15], sea nodule [16], chitosan [17][18][19], zeolites [20][21][22], clay [23][24][25], natural oxide [26,27], industrial waste [28], iron-coated sand [29], and some biosorbents [30][31][32].…”