Enhanced Ni(II) removal using NaCl-treated zeolite for solid phase extraction
摘要
Nickel is a water contaminant. The maximum admissible concentration of Ni(II) in drinking water is below limit of detection of the more affordable instrumental techniques. The present study was aimed at the characterization and evaluation of the purified clinoptilolite type Cuban zeolite treated with NaCl solution as sorbent for the solid phase extraction of Ni(II) from aqueous solutions. The maximum sorption capacity (28.84 mg g−1) was achieved in static operation mode, 70 °C of temperature, pH 5 of the 5 mg L−1 Ni(ll) concentration solution, contact time 30 min and sorbent dose 1 g L−1. The quantitative desorption with 102 ± 8% recovery was reached using 2 mol L−1 ammonium chloride solution tested in aqueous solutions with 0.05 and 0.02 mg L−1 of Ni(II) concentration. The sorption at equilibrium and 30 °C was described by Langmuir isotherm, and by Freundlich isotherm at 50 °C and 70 °C, while Dubinin- Radushkevich isotherm fitted well for all temperatures. Chemical interaction was confirmed as principal mechanism (a) by fitting the kinetic model of Ho and (b) the mean adsorption energy that was greater than 8 kJ·mol−1. The sorption process was favoured for all temperatures with ∆Gθ < 0, being exothermic (∆Hθ < 0) for 30 °C and endothermic (∆Hθ > 0) for higher temperatures. The production of entropy (∆Sθ > 0) reflected the increase of the complexity of the system after sorption. The high potential of the Cuban clinoptilolite type zeolite treated with NaCl for its application in water decontamination and determination of Ni(II) at the low concentration of 0.02 mg L−1 was demonstrated.