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 the untreated (native) sample, which was shown on the example of the 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. The determinants in the pre-preparation of sorbent by "microwaves" are the ultimate power and time of irradiation.

Adsorption of Copper Ions by Microwave Treated Bentonite

“…The maximal adsorption capacities represent the adsorbent affinity towards copper ions. The results of the present study and the data from our previous investigations have shown that direct irradiation to bentonite (DIR) [20,22,23] is more advantageous than the procedure for two-step activation of the sorbent (STIM) [19,21,24] because it does not require an additional stage of treatment of the sorbent (preliminary washing with double distillated water during irradiation). A smaller amount of technological operations simplify the process, reduce time and, accordingly, reduce the cost of water treatment.…”

“…Maximum adsorption capacity of heavy metal ions (mg/g) a Ni [19] b Ni [20] a Zn [21] b constant weight was reached. The content of Cu 2+ ions in solutions was determined by the atomic absorption method.…”

“…Two methods of sorbent microwave treatment without adding acids or other activators were described earlier [19][20][21][22][23][24]. In so called STIM-method [19,21,23,24] natural bentonite is washed by bidistilled water and simultaneously irradiated with microwaves, later the sorbent is exposed to contact with salt solutionsa twostep procedure for activating the sorbent (i.e. "stimulation").…”

“…In the DIR-method (direct irradiation) [20,22,23] samples of natural bentonite contacted with aqueous salt solutions under the microwaves irradiation. It is proved [19][20][21][22][23][24] that both methods of bentonite microwave treatment lead to a significant increase in its maximum adsorption capacity of heavy metal ions Ni [19,20], Zn [21,22], Pb [23], Cu [24]. The advantage of DIR-method is the intense spontaneous crystallization of a new phase on the surface of the sorbent [20,22,23].…”

Features of Extraction of Copper, Zinc and Nickel Ions From Aqueous Solutions by Natural Sorbents, Activated Microwaves

“…Автори уже повідомляли у своїх попередніх публікаціях [5][6][7][8][9][10][11] про результати вивчення сорбційних властивостей глинистого матеріалу бентоніту (Бнт), опроміненого мікрохвилями у поєднанні з гідротермальною активацією. Було з'ясовано, що здатність цього природного сорбенту вилучати з водних розчинів деякі ВМ (зокрема, йони свинцю, міді, цинку та нікелю) помітно зростає після такої комбінованої підготовки.…”