Removal of chromate anions and immobilization using surfactant-modified zeolites

In this research surface modified zeolites, Linde Type A and clinoptilolite, were used for the chromate ions uptake from aqueous solutions as well as its encapsulation through a vitrification process. The surface chemistry of zeolites was modified using a cationic surfactant hexadecyltrimethylammonium (HDTMA) to promote the capability of anions uptake. The results of characterization by X-ray diffraction showed unique crystalline phases for each zeolite which remain unchanged after the incorporation of the surfactant. Evidence from Fouriertransform infrared spectroscopy studies revealed the effective bond of the HDTMA on the clinoptilolite surface. Results suggested that the presence of CH2- groups after the modification play a key role for the anion attraction. Kinetic studies revealed that surfactant-modified clinoptilolite was able to adsorb 9.83 mg/g of chromate and better fitted pseudo-second order model (R-2 = 0.957). The equilibrium was better represented by Freundlich model (R-2 = 0.993). Finally, the proposed vitrification process the spent zeolitic adsorbent was successful, avoiding leaching of chromate ions after two months at different pH values.