EDTA modified LDHs as Cu2+ scavengers: Removal kinetics and sorbent stability

RICARDO ROJAS; MARIA ROSARIO PEREZ; EUSTAQUIO M. ERRO; PATRICIA I. ORTIZ; MARIA ANGELES ULIBARRI; CARLA E. GIACOMELLI

JOURNAL OF COLLOID AND INTERFACE SCIENCE

Elsevier

Año: 2009 vol. 331 p. 425 - 431

0021-9797

EDTA modified layered double hydroxides (LDHs) were investigated as potential sorbents to remediate heavy metals pollution. The polidentate ligand was introduced by an exchange method in a Zn–Al-LDH, which takes place with partial erosion of the layers, causing the intercalation of [Zn(EDTA)]2− complex instead of the ligand. [Cu(H2O)6]2+ cation was selected as a model cation to study the uptake mechanism, exploring the elimination kinetics from the first minutes up to the steady state. A flow injection analysis system coupled to an amperometric detector (FIA-AM) was applied to perform fast and reliable [Cu(H2O)6]2+ determinations in monodisperse solid–aqueous solution systems. Furthermore, the sorbent stability was determined as a function of the pH and the nitrate concentration. The [Cu(H2O)6]2+ elimination is produced by an exchange reaction with [Zn(EDTA)]2− anions placed either in the solid interlayer or in the aqueous solution, this last being released from the sorbent. Additional [Cu(H2O)6]2+ removal is produced by Cu(OH)2 precipitation at high copper concentrations due to the LDHs high pH buffering capacity. The sorbent removes [Cu(H2O)6]2+ with high affinity in a wide concentration range. The elimination process reaches equilibrium in less than 30 min and leaves metal cation concentrations lower than 0.05 ppm in the supernatants.