Cd(II) adsorption from aqueous solutions using modified attapulgite

Abstract

In order to obtain a high removal efficiency of Cd(II) in aqueous solution, natural attapulgite (ATP) was modified with hydrochloric acid (HCl), octadecyl trimethyl ammonium chloride, nitrilotriacetic acid (NTA), and ethanediamine (EDA) to develop an effective Cd(II) adsorbent. The characteristics of the modified adsorbents and the natural ATP were characterized using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The adsorption kinetics of Cd(II) in aqueous solution were well described by a pseudo-second-order kinetic equation, and the sorption isotherm most closely followed the Langmuir model. Complexation was determined to be the main adsorption mechanism. Among the four modified ATPs, EDA-ATP (ATP modified by EDA) showed the best adsorption capacity for Cd(II), reaching 10.55 mg g−1, which was 115 and 27 percentages higher than the capacity of the unmodified ATP and NTA-ATP (ATP modified by NTA), respectively. The ionic strength and pH of the initial solution had no significant impact on the adsorption capacities of Cd(II) onto EDA-ATP. The EDA-ATP loaded with Cd(II) could be regenerated easily by acid treatment. These results give an available choice for the effective and recyclable Cd(II) ions sorbents from water.