Anita Štrkalj

THERMODYNAMIC AND KINETIC STUDY OF ADSORPTION OF Ni(II) IONS ON CARBON ANODE DUST

In this study the use of carbon anode dust (CAD), which is the solid residue from aluminum production, as a low-cost adsorbent for the removal of Ni(II) ions from wastewater was investigated. A mechanism of adsorption kinetics and thermodynamics was proposed. In order to investigate the adsorption process of nickel ions on CAD three kinetic models were used: Lagergrens pseudo-first-order model, pseudo-second-order model, and the intra-particle diffusion model. Various thermodynamic parameters, such as the energy of activation (Ea), activation enthalpy (ΔH*), activation entropy (ΔS*), and free energy of activation (ΔG*), were evaluated. Observation of the value of the energy of activation suggests that the process uptake of Ni(II) ions can be described as activated chemisorption. The positive values of enthalpy of activation and free energy of activation, as well as negative values of entropy of activation, mean that the process of removal of Ni(II) ions is endothermic, non-spontaneous, and without structural changes in the solid carbon anode dust particles.

Primjena spektrometrijskih metoda u analizi metalurških uzoraka

Izbor metode i instrumenata za određivanje kemijskog sastava kao i koncentracije pojedinih elemenata ovisi o nizu zahtjeva koji se postavljaju u istraživanju, ali i proizvodnji i kontroli gotovih proizvoda. Nove tehnologije proizvodnje postavljaju sve strože zahtjeve. Unazad nekoliko desetaka godina bilo je dovoljno odrediti nekoliko osnovnih parametara koji ukazuju na neka fizikalno-kemijska svojstava ispitivanog materijala. U suvremenoj tehnologiji nužno je određivanje većeg broja parametara, često i provjera/potvrđivanje rezultata na sličnim instrumentima kao i brzina i točnost analize. Vrlo je teško pronaći metodu i instrument koji će zadovoljiti sve tražene kriterije.1