Synthesis and adsorption properties of amphoteric adsorbent HAx/CMC-yAl

Abstract

Novel amphoteric microspheres adsorbents (HAx/CMC-yAl), based on carboxymethyl cellulose (CMC) modified with various amount of humic acid (HA) and cross-linker aluminum nitrate (Al(NO3)3), were synthesized facilely under mild conditions. Its adsorption properties toward representative cationic and anionic dyes were studied. The optimized adsorbent HA1.0/CMC-3Al was characterized and analyzed by fourier transform infrared spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, thermogravimetric analysis and Zeta potentials. The effects of types of dye substrates, contact time, initial dye concentration, pH of the solution, and adsorbent dosage, on cationic methylene blue (MB) and anionic orange II (ORII) removal were systematically investigated. The HA1.0/CMC-3Al showed pH-sensitive and the maximum adsorption capacities toward MB and ORII were 76.92 and 71.43 mg g−1, respectively, within 300 min at pH 3 and 295 K. The swelling rate and the recylcing properties were also studied. The pseudo-second-order kinetic model and Langmuir isotherm provided better correlation with the experimental data for the adsorption of dyes onto HA1.0/CMC-3Al. The effects of coexistent NaCl and sodium dodecylbenzenesulfonate (SDBS) surfactant on a binary dye system (MB/ORII) were also investigated. The results indicated that the adsorption of dyes was inhibited by NaCl, while the adsorption of cationic dye was promoted by SDBS at given concentrations. In addition, the possible mechanism of adsorption process was proposed.