Efficient removal and highly selective adsorption of Hg2+ by polydopamine nanospheres with total recycle capacity

Abstract This study reported a new method for efficient removal of Hg 2+ from contaminated water using highly selective adsorptive polydopamine (PDA) nanospheres, which were uniform and had a small diameter (150–200 nm). The adsorption isotherms, kinetics, thermodynamics were investigated. Also, the effects of ionic strength, co-existing ions on removing ability of PDA nanospheres for Hg 2+ were studied. Adsorption of Hg 2+ was very fast and efficient as adsorption equilibrium was completed within 4 h and the maximum adsorption capacities were 1861.72 mg/g, 2037.22 mg/g, and 2076.81 mg/g at 298 K, 313 K, and 328 K respectively, increasing with increasing of temperature. The PDA nanospheres exhibited highly selective adsorption of Hg 2+ and had a total desorption capacity of 100% in hydrochloric acid solution, pH 1. The results showed that the structure of PDA nanospheres remained almost unchanged after recycling five times. Furthermore, X-ray photoelectron spectroscopy (XPS) was employed to determine the elements of PDA nanospheres before and after Hg 2+ adsorption. Considering their efficient and highly Hg 2+ selective adsorption, total recycle capacity, and high stability, PDA nanospheres will be feasible in a number of practical applications.