Use of Modified Zeolites for the Remediation of Waters and Cultivated Soils from Cu(II)

The ability of iron oxides (goethite) and natural zeolite (clinoptilolite) to adsorb copper from its aqueous solutions was extensively studied in the past. In this paper, the production of modified zeolites (systems I and II) from raw materials of zeolite and goethite was investigated compared to the initial materials. These two systems presented higher adsorption than goethite or clinoptilolite. Comparing the two systems, system II presented higher adsorption than system I. Isotherm studies showed that the adsorption data from all materials were best described by Freundlich isotherm. According to thermodynamic study, the values of Delta G degrees became more negative with the increase of temperature, indicating that the adsorption process was more favorable to higher temperature. The positive values of Delta H degrees indicated endothermic nature of adsorption. The use of all adsorptive materials as soil improvements was also investigated. Goethite, zeolite, and systems I and II were mixed separately with three different soils (clay loam, sandy loam, and loamy sand). Lettuces were cultivated, and the combination of system II with the loamy sand soil led to the best morphological characteristics of lettuces with the minimum adsorption of copper. Consequently, modified zeolites could be considered as two satisfactory detergents of highly copper concentration in soil and water

Chitosan-Immobilized Pumice for the Removal of As(V) from Waters

A novel sorbent, chitosan-immobilized pumice, has been prepared for the sorption of As(V) from waters prior to its determination by hydride generation atomic absorption spectrometry. The success of the immobilization has been checked with such characterization techniques as scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. Points of zero charge of the sorbents were determined with potentiometric mass titration. Batch-type equilibration studies have shown that the novel sorbent can be employed at a wide pH range resulting in quantitative sorption (>90 %) at pH 3.0-7.0 and greater than 70 % sorption at pH >8.0. These results demonstrate the advantage of immobilizing chitosan onto pumice, because, under the same conditions, pumice displays <20 % sorption toward As(V), whereas chitosan gives approximately 90%sorption only at pH 3.0. The validity of the method was verified through the analysis of ultrapure, bottled drinking, and tap water samples spiked with arsenate; the respective sorption percentages of 93.2 (±0.7), 89.0 (±1.0), and 80.9 (±1.3) were obtained by batch-type equilibration. Arsenic sorption was also examined in the presence of common interfering ions resulting in competing effects of PO3- 4 and NO- 3on As(V) adsorption