Adsorption of Copper Ions by Microwave Treated Bentonite

Abstract

Changes of bentonite surface structure under the influence of direct microwave irradiation during adsorpion of Cu2+ from concentrated solutions were investigated by X-ray and EDS analysis. The microwave treated bentonite (MTB) has been proved to have enhanced adsorption capacity for copper due to improved pore structure and some peculiarities of adsorption mechanism. The non-linear fitting of experimental data to the theoretical isotherms have demonstrated that the adsorption on natural bentonite fitted the Toth model, whilst microwave-treated bentonite fitted the Langmur-Freundlich model. The isotherm modeling allowed predicting the maximal adsorption capacities 44.8 mg/g. XRD and SEM analysis of MTB sample after adsorption indicated formation of microcrystals of individual copper compound. The adsorption on MTB sample takes place not only in pores or in monomolecular layer on the bentonite surface, but the prevalent mechanism is surface-induced co-precipitation of copper as microcrystals of individual copper compound.

Use of Microwaves to Activate Bentonite in the Processes of Sorption of Nickel Ions from Concentrated Aqueous Solutions

“…1 shows a graph of the dependence of adsorption of Nickel ions on their equilibrium concentration, obtained in the present series (dark markers). Near (light markers), a part of the results of the previous series of works [9] is depicted, where more dilute solutions and other sorbent activation procedure were used.…”

“…From this model solution a series of working solutions in the range of concentrations of Ni 2+ ions from 720 to 140 mg/dm 3 was obtained by stepwise dilution of it in 1,3 times. Such a distribution of concentrations is selected in order to have its lower values partially overlap with higher values of concentrations of working solutions in the previous series of studies [9]. This made it possible to compare the results obtained with the front series now and to deduce certain patterns.…”

“…In a series of specimens "DIR" (Direct Irradiation), the native sorbent was not washed with water, as in previous work [9], but immediately filled with a working solution of Nickel (II) chloride. The flask was shaken and placed with the suspension in a microwave oven.…”

“…As in previous works [6,9], as a source of microwave electromagnetic waves, an author-made generator was used, executed on a magnetron of the model M-10; the radiation range -2.45 GHz; output power -790 Watts.…”

“…Among other water pollutants, the object of the study also acted Nickel compounds. In particular, in the previous series of works, the authors investigated the effect of microwaves on the sorption of Nickel ions by bentonite from dilute aqueous solutions [9].…”