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

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.