TY - JOUR
TI - Chromium (VI) uptake by polyhexamethylene-guanidine-modified natural zeolitic materials
AU - Misaelides, P.
AU - Zamboulis, D.
AU - Sarridis, Pr.
AU - Warchoł, J.
AU - Godelitsas, A.
JO - Microporous and Mesoporous Materials
PY - 2008
VL - 108
TODO - 1-3
SP - 162-167
PB - 
SN - 1387-1811
TODO - 10.1016/j.micromeso.2007.03.041
TODO - Adsorption;  Chromates;  Concentration (process);  pH effects, Clinoptilolite;  Polyhexamethylene-guanidine, Zeolites, Adsorption;  Chromates;  Concentration (process);  pH effects;  Zeolites
TODO - The Cr(VI) uptake from aqueous solutions by polyhexamethylene-guanidine-modified natural zeolitic materials from Metaxades, Greece (PHMG-MTX) and Tedzami, Georgia (PHMG-TZ) was investigated using batch techniques. Spectrophotometry using 1,5-diphenylcarbazide for colour development was used for Cr determination. The Cr(VI)-solution concentration varied between 5 and 50 mg/L and the initial pH was adjusted to 3.0, 4.0 and 5.0. Additional experiments were conducted in the presence of competing anions (background electrolyte I = 0.1 M established by 0.1 M NaNO3 and 0.033 M Na2SO4) on solutions with unadjusted pH. For comparison, the Cr(VI) adsorption by Tedzami tuffs modified by octadecylpolyhexamethylene-guanidine-chloride (ODPHMG-TZ) was also investigated. All investigated materials adsorbed considerable amounts of Cr(VI)-oxyanions. It was shown that the Cr(VI)-uptake strongly depended on pH and the presence of competing anions. The Cr(VI)-oxyanion uptake by PHMG-TZ was slightly higher than that observed for ODPHMG-TZ, whereas the sorption capacity of PHMG-MTX was of the same order of magnitude as Metaxades tuffs modified by hexadecyl-trimethylammonium-bromide. The experimental data obtained for pHinit = 3.0 were selected for modeling the adsorption behavior of the materials using six isotherm equations (Freundlich (F), Langmuir (L), Langmuir-Freundlich (L-F), Dubinin-Radushkevich (D-R), Redlich-Peterson (R-P), Toth (T)). The obtained modeling results indicated that, although the three-parameter models, taking into account the surface heterogeneity, provided the closest approach to the measurement data, the parameters estimates could be highly biased. On the other hand, the two-parameter Langmuir isotherm was sufficient to describe the process equilibrium in terms of smallest number of adjustable parameters and approximation of the sorption capacity. © 2007 Elsevier Inc. All rights reserved.
ER -