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1 2009

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The sorption of copper ions by gyrolite in alkaline solution

Bankauskaite A., Baltakys K.

Materials Science Poland

2009

Vol. 27, No. 3

899--908

Sorption of copper ions by synthetic pure gyrolite (CaO/SiO2 = 0.66; 96 h; 200 °C) in alkaline solutions was examined. When the initial concentration of Cu2+ ions is 1 g/dm3, the cation exchange capacity of the gyrolite is 100 mg Cu2+/g after 360 min of sorption at 25 °C. It has been proved that the cation exchange capacity of gyrolite depends on the concentration of copper ions in the Cu(NO3)2 solution, because a fivefold increase of the concentration (from 1.0 to 5.0 g/dm3) reduces the duration of the ion exchange reaction by a factor of three (from 15 min to 5 min). In solutions with higher initial concentrations of Cu2+ ions (10.0 and 20.0 g/dm3), the sorption proceeds more intensively and all the copper ions are adsorbed in 1 min. It should be noted that the cation exchange reactions are reversible in alkaline solution, because nearly 90% of the copper ions are adsorbed in a physical process, while the remaining part of the cation exchange process takes place in a chemical reaction. Furthermore, the crystal structure of gyrolite is stable in alkaline solution. The products of sorption were characterized by X-ray diffraction, thermogravimetry-differential scanning calorimetry and Fourier-transform infrared spectroscopy methods.