Walnut skin nanoparticles as a novel and fast nano-biosorbent for the fast removal of lead ions from polluted water

Walnut skin nanoparticles are prepared by an innovative vibratory ball mill (Spex). A suitable amount of walnut skin powder (approximate to 100 g) together with 200 hard chromium electroplated balls are filled into the tank of Spex, and vibrated by 1,200 rpm for 10 h. SEM and TEM images of the output powder of Spex show that the milled powder includes uniform nanoparticles with 65 nm average diameters. The prepared walnut nanopowder is used as a new nano-biosorbent for the fast removal of lead ions from polluted waters. The obtained experimental data show that the adsorption of lead ions on the surface of walnut skin nano-biosorbent (WSNBS) is acceptably fitted to the Langmuir isotherm model with a maximum adsorption capacity of 17.39 mg g(-1). The optimum conditions for the removal of lead ions from water include solution pH 4, sample volume 500 ml or less, WSNBS weight 50 mg or more, contact time less than 2 s at room temperature. The desorption step can be done by 1.5 ml 0.5 M HNO3. In operation conditions, preconcentration factor, RSD and the detection limit are obtained 200, 4.3% and 0.11 ppb, respectively. The interfering effects of some cations such as Cu2+, Ni2+, Fe2+, Zn2+, Mg2+ and Na+ on the removal efficiency of lead ions are investigated. The presented method is successfully applied for the removal and the determination of lead ions from real samples.