Surface modification of zeolite by cationic surfactant and the application on adsorptive removal of azo dye Ponceau 4R

Abstract

The zeolite Permutit (Per) with the cubic crystal, 1.66 of the SiO2/Al2O3 ratio, 44.81 m2.g−1 of the specific surface area, 1.7 nm of the average pore radius, and the typical bonds of Si-OH, Si-O-Si, Si-O-Al, and O-Si-O-Si was investigated in the present study. The adsorptive removal efficiency of the azo dye PC4R was almost doubled from about 53.23% to 90.06% by Per surface modification with the cationic surfactant cetyltrimethylammonium bromide (CTAB) as an effective and high-performance adsorbent. The PC4R adsorptive removal was optimized at independent variables of pH 4, the ionic strength of 10 mM NaCl, the Per dosage of 6 mg.mL−1, and the short contact time of 15 min. Both the Langmuir and Freundlich models were reasonable to describe the PC4R adsorption isotherms on the CTAB@Per while the PC4R chemisorption kinetics were well accorded with the pseudo-second-order model. The PC4R multilayer adsorption capacity achieved an extrapolated maxima of 15.470 mg.g−1. The PC4R adsorption mechanisms were demonstrated by the FT-IR measurement to be primarily the electrostatic attractions between the CTAB and the PC4R, dipole-ion interactions, and hydrogen bondings between the PC4R molecules.