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Abstract
In this study, ZSM-11 zeolite was successfully prepared by direct hydrothermal synthesis using silica sol as silicon source and tetrabutylammonium hydroxide as organic structure directing agent. X-ray diffraction confirmed the prepared product was well-crystalline ZSM-11 zeolite. Scanning electron microscopy showed that a single particle of the prepared product had a mean size of approximately 2.5 μm × 6 μm. Batch adsorption experiments exhibited that solution pH, ZSM-11 dosage, and NaCl concentration had effects on PNP (p-nitrophenol) removal. A high adsorption capacity of 56.3 mg/g was obtained at pH 4, 25°C, ZSM-11 dosage of 0.3 g/L, and initial PNP concentration of 20 mg/L. The addition of NaCl (5.8–580 mg/L) exerted a positive impact on PNP adsorption. Results of desorption experiments showed that a desorption percentage of 78.9% could be obtained in 120 min using 1.44% NaOH solution as desorbent. The equilibrium adsorption data of PNP onto the as-prepared samples were well fitted by the Freundlich isothermal model in the temperature range 25–45°C. The adsorption kinetics was found to obey the pseudo-second-order model. Thermodynamically, it was found that the adsorption of PNP onto ZSM-11 was spontaneous and enthalpy-driven with ∆H° = −10.96 kJ/mol. The ZSM-11 samples were found to be effective adsorbent for the removal of PNP from wastewater.
Acknowledgments
This work has been funded by the National Natural Science Foundation of China (No. 51268018). The authors are grateful to National Engineering Research Center for Domestic and Building Ceramics (JCU) for the assistance in the analytical measurements.