Recovery of p -nitrotoluene by selective adsorption using MFI type zeolites

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Recovery of p-nitrotoluene by selective adsorption using MFI type zeolites Zhaobing Guo • Shanli Chen • Fengling Liu • Jinjin Wang • Xiaoyu Shen • Shourong Zheng

Received: 23 July 2014 / Revised: 16 December 2014 / Accepted: 13 January 2015 / Published online: 23 January 2015 Ó Springer Science+Business Media New York 2015

Abstract Silicalite-1 and HZSM-5 zeolites were used as the adsorbents for selective adsorption of p-nitrotoluene (p-NT) from simulated wastewater containing p-NT and o-nitrotoluene (o-NT). Results showed that adsorption behaviors of p-NT in the zeolites were different from o-NT. The maximum adsorption amounts of p-NT in the zeolites were found to be approximately 4 molecules per unit cell (mol./u.c.), irrespective of adsorption temperatures investigated, which were markedly higher than those of o-NT. In addition, the presence of acid sites led to an enhanced affinity of p-NT adsorption and to suppressed adsorption of o-NT in HZSM-5 zeolite compared with silicalite-1. Adsorption kinetic results showed that rate constants of p-NT were markedly higher than those of o-NT in silicalite-1 and HZSM-5 zeolite. For the separation of p-NT, enhanced selectivity of HZSM-5 zeolite for p-NT adsorption was observed compared with silicalite-1. Under our optimized conditions, p-NT with purity of 98.2 % could be recovered with HZSM-5 zeolite, which was ascribed to the marked differences in adsorption amounts and rate constants between p-NT and o-NT in the zeolite.

Z. Guo (&)  S. Chen  F. Liu  J. Wang  X. Shen School of Environmental Science & Engineering; School of Atmospheric Physics, Nanjing University of Information Science & Technology, Nanjing 210044, People’s Republic of China e-mail: [email protected] S. Chen Environmental Protection Department of Jiangsu Province, Nanjing 210036, People’s Republic of China S. Zheng State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, People’s Republic of China

Keywords p-nitrotoluene  HZSM-5 zeolite  Silicalite-1 zeolite  Selective adsorption

1 Introduction Pollution from chemical industry is believed to be one of the main reasons for the deterioration of aquatic environment. In general, most of artificially synthesized chemicals, which usually present in wastewater from chemical processes, are resistant to biodegradation. A variety of studies have demonstrated that the detoxification of wastewater containing these recalcitrant chemicals can be achieved using advanced oxidation processes (AOPs), such as photo-catalysis (Dunlop et al. 2014; Zhang et al. 2013a, b), Fenton oxidation (Liu et al. 2014, Sanchis et al. 2014), ultrasonication (Guo and Feng 2009) and gamma irradiation (Guo et al. 2012). It should be emphasized that the decomposition of these chemicals using AOPs inevitably results in a high treatment cost and waste of resource. Thus, there is a growing need to recover valuable chemicals from wastewater from the viewpoint of cleaner production (Khalili et al. 2014; Xu et al. 2003). Ad