SELECTIVITE D'ADSORPTION DES FRACTIONS DE SRFA PAR LES BENTONITES ADSORPTION SELECTIVITY OF SRFA FRACTIONS BY BENTONITES

Abstract

This work aims to assess the adsorption selectivity of the organic matter fractions contained in Suwannee River Fulvic Acid (SRFA), on three Algerian clays. SRFA is a natural organic matter contain a large number of functional moieties such as carboxylic, phenolic and alcoholic groups that interact with surface groups as well as ions in solution. The selected clay minerals are phyllosilicates (2:1 family) namely "industrial load bentonite" (noted BCI), "drilling bentonite" (noted FB2) and "treated bentonite" (noted BT). After bringing SRFA into contact with the clays, characterizations by XRD, FTIR and TGA before and after contact were realized. The results showed a remarkable and distinguished affinity of the SRFA fractions toward the three clays and allowed us to establish the following order: BT > BCI > FB2. BT clay (rich in Na and Ca) adsorbs and retains almost of all SRFA fractions, whereas BCI clay adsorbs only a few fractions: alcohols, acids (O−H); aliphatic (C−H), phenol-acids and sugars (C−O); aromatic (C−H). However, for the FB2 clay, it only adsorbs the alcohol, acid (O−H) and aliphatic (C−H) fractions. The proposed mechanism is due to interactions (electrostatic, hydrophobic) and ligand exchange. The adsorption is favored according to the swelling nature of the clay, for the least negative zetapotential, for the lowest “natural” pH and the highest CEC. It can be concluded that BT can be considered as a reservoir of organic matter and that the BT/SRFA complex will contribute to the structure of the soil, the capacity of water retention and the reduction of oxidative reactions thus playing a major role in the cycle of various nutrients and pollutants.

Keywords

• adsorption
• clay mineral selectivity
• clay-organic matter interactions
• fractionation
• suwannee river fulvic acid