manganese dioxide nanoclusters as a potential nano-sorbent for the removal of silver ion from water

hydrous manganese dioxide nanoclusters are prepared by the oxidation of manganese (ii) ions with ammonium persulfate and used as a new sorbent for ag+ ion removal from aqueous medium. the synthesized compound is characterized using scanning electron microscopy, dynamic light scattering, energy dispersive analysis of x-rays, x-ray diffraction and bet surface measurements. scanning electron microscopy images showed that the synthesized hydrous manganese dioxide nanoclusters include cactus-shaped nanoclusters with uniform needles of average diameter of 36 nm and length of 1000 nm. x-ray diffraction data reveal that γ-mno2 is formed in this method. batch experiments are carried out to evaluate the ag+ adsorption capacity of hydrous manganese dioxide nanoclusters. the maximum adsorption capacity estimated by the langmuir model was 81.97  mg g-1 for ag+. silver ion adsorption on hydrous manganese dioxide nanoclusters is a fast process and the kinetics followed a pseudo-second-order rate equation. the removal efficiency of ag+ depends on hydrous manganese dioxide nanoclusters amount, ph and temperature of the solution. the presences of na+, ca2+ and mg2+ ions in the concentrations lower than 200 ppm have no significant influence on silver ion removal. the adsorbed ions can easily eluted by the small volume of a solution consisting thiourea and hydrochloric acid. finally, the experimental data show that the synthesized hydrous manganese dioxide nanoclusters can quantitatively remove silver ions from real water samples.