Sorption of Pt(II) on inactive biomass of <i>Aspergillus Niger</i> O-5 treated with cetyltrimethylammonium bromide

Platinum-group cytostatic have been found in natural waters due to the current inefficiency of wastewaters treatment plants. This study was aimed to the assessment of inactive biomass of <i>Aspergillus niger</i> O-5 treated with cetyltrimethylammonium bromide as sorbent for solid phase extraction of [PtCl₄]^2-complex from aqueous dissolutions for the subsequent development of new water treatment technologies. Maximum sorption capacity of 54 mg·g⁻¹ was achieved at 25 °C under the following experimental conditions: pH of dissolution = 5, biomass mass = 10 mg, dissolution volume = 10 mL, Pt(II) mass = 0.5 mg and contact time = 30 min. The good fitting of the model of Ho and the increase of sorption capacity up to 102 mg·g⁻¹ with temperature suggested the chemisorption as predominant mechanism. The mean free energy of adsorption was higher than 8 kJ·mol⁻¹ for all temperatures, which also indicated the chemical character of the interaction. The absolute value of the standard molar Gibbs free energy of formation increased from 3.032 to 8.336 kJ· mol⁻¹ with temperature signifying that the sorption was thermodynamically favored, occurred spontaneously and the degree of spontaneity increased with temperature. The positive value (32.3 kJ·mol⁻¹) of the standard molar enthalpy qualified the sorption as an endothermic process, after which the adsorbent/sorbate system became more thermodynamically stable.