Uptake of As by 4-Na-Mica and their mechanical treated product

L. LORENZO; P. NARANJO; E. FARFAN TORRES; R. M. TORRES SÁNCHEZ

Zapokane, Poland

Conferencia; 4th Mid European Clay Conference; 2008

Mineralogical Soc. of Poland

Removal of As from water has been tested with materials of low cost, in which the presence of Fe and Al seems to be important. Synthetic 4-Na-mica obtained from kaolin, (high cationic exchange capacity) and their product of mechanical treatment (4-Na-micaMT) (where the alteration of the crystalline structure puts in evidence the structural Fe and Al ions) are postulated as competitive materials for As uptake. Materials characterization was obtained by XRD, SEM, specific surface and isoelectric point determination. As adsorption capacity was evaluated in both samples at pH 7.5, adsorptions kinetics and isotherms were also determined.  The results showed that As adsorption behavior was different for each material. The As adsorption by 4-Na-micaMT was higher than determines for its precursor, but it needs higher contact time (six days against 2 hours) to reach maximum removal capacity. This was assigned to a higher quantity of negatively charged edge sites in 4-Na-micaMT, which increase the solution pH by protons adsorption. Keeping in mind that at the experimental used pH the As species are negatively charged it was understandable that 4-Na-mica present a biggest As uptake for unit mass, at shorter times (<6 hours). The surface charge of 4-Na-micaMT decreases when the contact time increases and consequently the electrostatic repulsion also decreases, which allows it to adsorb a higher quantity of As species. The uptake capacities were 60.7% and 96.5% for 4-Na-mica and 4-Na-micaMT, respectively, showing their potentiality in the treatment of As polluted waters.