Photodecolorization of rhodamine under sunlight irradiation driven by chabazite

Abstract

Natural zeolite chabazite was studied for the discoloration of rhodamine 6G solutions in dark and under sunlight irradiation. The discoloration of rhodamine aqueous solutions containing chabazite was monitored by UV–vis absorption and photoluminescence spectroscopies and high-performance liquid chromatography measurements on aliquots of the rhodamine solutions. After the discoloration experiments the chabazite powders were collected, dried and analyzed by Fourier-Transform Infrared spectroscopy to obtain additional information about the discoloration process. The results show that chabazite produces the discoloration of the rhodamine solutions in both conditions, dark and under sunlight, with different discoloration mechanisms and rates. In dark, chabazite removes the rhodamine molecules from the solution by adsorption and cation exchange mechanisms. Under sunlight irradiation, additional photo induced mechanisms produce the degradation of the rhodamine molecules and a faster discoloration of the solution. The discoloration process followed a first order kinetics with rate constants of 4.9×10−3 and 1.2×10−2min−1 in dark and under sunlight conditions, respectively. It is proposed a mechanism for the photodegradation of rhodamine molecules under sunlight irradiation, where the role of chabazite is fundamental.