Gyrolite adsorption of Zn2+ ions in acidic and alkaline solutions
The influence of solution pH to gyrolite adsorption capacity of Zn2+ ions has been examined. Adsorption experiments were carried out in the thermostatic adsorber by stirring 1 g of gyrolite in 100 ml of Zn(NO3)2 solution containing 0.3 g/dm3 of Zn2+ ions. Duration of adsorption at 25 °C temperature was 120 min. It was found that adsorption process in alkaline solution proceed faster and more efficiently as in acidic because after 30 s 95 % of Zn2+ ions (28.50 mg Zn2+/g) intercalated in to gyrolite structure, whereas in acidic medium – 68 % of Zn2+ ions (20.43 mg Zn2+/g). Substitution reaction was found typical of gyrolite in the alkaline solution because 82 % zinc ions participated in ion exchange reaction and other part of these ions were present in gyrolite according to an addition interaction. Cation exchange mechanism proceeded differ in acidic solution because all zinc ions participated only in ion exchange reaction. The adsorption process in alkaline solution folowed by a pseudo-second order model and suggest that it is process of chemosorption. Gyrolite recrystallized in to gyrolite gel and C-S-H(I) when reaction medium is acidic and in alkaline medium intercalated zinc ions do not affect the structural properties of gyrolite.
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