Carboxylation kapok fiber as a low-cost, environmentally friendly adsorbent with remarkably enhanced adsorption capacity for cationic dyes

A new surface dicarboxylatic kapok fiber (DC-KF) was prepared by surface modification. During the sorbent preparation, the response surface methodology based on the experimental design of central composite design was employed to select the optimum conditions. Fourier transform infrared, scanning electron microscopy, X-ray diffraction, thermogravimetry, and X-ray photoelectron spectroscopy were employed to investigate the structures of raw, wax removed, and surface DC-KF. As a novel sorbent, it was used in removing cationic dyes of natural red, methylene blue, and rhodamine 6G. The influences of contact time, pH, dye concentration, and ionic strength on dye removal were studied. The adsorption kinetics and isotherms were analyzed. Results showed that the dyes adsorbed onto DC-KF could reach the equilibrium within 1 h. The maximum adsorption capacities calculated from the Langmuir model were 816.4, 524.4, and 613.4 mg/g for NR, MB, and Rh-6G, respectively. The pH and ionic strength had a significant effect on dye removal. Excellent regeneration property demonstrated that DC-KF had the potential of actual applications. For its high adsorption capacity, excellent regeneration, low cost, simple preparation, and complete environmental friendliness, DC-KF will be an excellent candidate for treating cationic dye polluted water.