Improvement of Sorption Parameters of Nickel Ions on Bentonite in the Result of its Irradiation by Microwaves

Abstract

The adsorption isotherms of nickel ions from aqueous solutions on bentonite, a natural argillaceous material, previously prepared using ultrahigh-frequency electromagnetic waves ("microwaves") were researched in the article. The phase composition of the sorbent was studied by applying the X-ray powder method. Bentonite sample being pre-wetted and irradiated by microwaves shows 2.7 times better sorption properties than untreated (native) sample, which was shown on the example of adsorption process of nickel ions from model solutions in static conditions. The sorption parameters prepared by using the "microwaved" and the native samples of bentonite were calculated according to the Langmuir adsorption equations. The barrier density of nickel in the irradiated sorbent is 16.4 mg/g (0.28 mmol/g), whereas for native bentonite the value of the analogous parameter is 6.0 mg/g (0.10 mmol/g). The reason for such an increase in sorption properties may be the change in the crystalline structure and distribution of micropores on the surface of the sorbent under the action of "microwaves" in the aqueous medium. It is suggested that the joint action of two factors – microwave irradiation and hydrothermal destruction – affects the near-surface structure of the clay material, distribution of the macro- and micropores, activation of the absorbing surface, which, in turn, leads to a change in the sorption parameters. The determinants in the pre-preparation of sorbent by "microwaves" are ultimate power and time of irradiation. Keywords: water purification, sorbent, bentonite, nickel, activation, microwaves.