The dealuminated zeolites via acid leaching and followed calcination method for removal of hydrophobic bisphenol A

Abstract

The commercial Hβ (25, 50), HY (11) and HZSM-5(50) were dealuminated by acid leaching and subsequent calcination to improve their hydrophobic nature for the removal of bisphenol A (BPA). The structure and properties of the raw zeolites and the modified ones (labelled as T-Hβ (25, 50), T-HY (11), T-HZSM-5(50)) have been investigated comparatively by XRD, BET, SEM, XRF and contact angle test (CA). The results indicated that HY (11) and T-HY (11) had poor adsorption capacity for hydrophobic BPA because of destroyed crystalline phase of T-HY (11) and hydrophilic nature of HY (11). HZSM-5(50) and T-HZSM-5(50) also had poor adsorption ability for BPA molecules because larger BPA molecules cannot enter smaller pores of HZSM-5(50) and T-HZSM-5(50). However, the T-Hβ (25, 50) zeolites exhibited significantly higher adsorption capacity for BPA because their larger pore size remained than molecule size of BPA and larger water contact angles and molar ratios of SiO2/Al2O3 of T-Hβ (25, 50) than Hβ (25, 50), respectively. BPA removal mechanism study showed that hydrophobic interaction force between BPA and T-Hβ (25, 50) should be a main driving force. The adsorption process conformed to pseudo-second order model and the three-parameter Redlich-Peterson model. The adsorption rate of BPA over T-Hβ (50) (0.01050 ​g ​mg−1 ​min−1) was 2.29 times faster than that over Hβ (50) (0.004581 ​g ​mg−1 min−1), and the maximum adsorption capacity of BPA on T-Hβ (50) (117.62 ​mg ​g−1) was 3.5 times than that on Hβ (50) (33.78 ​mg ​g−1). The acid treatment-calcination method is feasible and appropriate for modification of Hβ in order to remove hydrophobic organic pollutants.