Marija Mihajlović

Kinetics, thermodynamics, and structural investigations on the removal of Pb2+, Cd2+, and Zn2+ from multicomponent solutions onto natural and Fe(III)-modified zeolites

The adsorption of Pb2+, Cd2+, and Zn2+ from equimolar multicomponent solutions onto natural and Fe(III)-modified zeolites was studied by batch experiments in order to determine the influence of the competitive effect on the efficiency ions removal at different initial concentrations and different temperatures. Kinetic and equilibrium studies showed that affinity of both zeolites was the highest for Pb2+ and much lower for Zn2+ and Cd2+. The competitive effect was negligible at lower concentrations, while Zn2+ and especially Cd2+ ions adsorption was suppressed as the concentrations were increased. Affinity of natural zeolite toward the ions was lower than that of the modified zeolite, as was shown for adsorption from single-component solutions. External film diffusion was the rate-controlling step at lower concentrations and for ions of higher affinity for the adsorbent, while intraparticle diffusion was dominant at higher concentrations and for ions of lower affinity for the adsorbent. The increasing spontaneity of the adsorption process with increasing temperature and the positive values of enthalpy of adsorption indicated the endothermic nature of the adsorption process. Structural investigations of the adsorbents loaded with Pb2+, Cd2+, and Zn2+ ions by X-ray photoelectron spectroscopy (XPS) confirmed the higher content of the ions in the surface and subsurface regions of the Fe(III)-modified than of the natural zeolite. XPS depth profiles of the loaded Fe(III)-modified zeolite showed that surface mechanisms of adsorption were dominant in the case of lead and cadmium, while zinc loading on the zeolite sample was governed mainly by an ion-exchange process.

Fizičko-hemijske modifikacije otpadne biomase kao sredstvo poboljšanja sorpcionih svojstava materijala

The main constituents of ligno-cellulosic (LC) biomass are lignin, celluloses and hemicelluloses, complex polymers with many functional groups, which can be modified with the purpose to improve the sorption properties of the starting material. This paper presents several physical and chemical modifications applied to LC biomass of peach stones (Prunus persica L.), abundant waste from food industry. These stones were firstly mechanically activated in two mill types, and then by different chemicals. Sorption experiments were performed in batch reaction system with stirring. Cu(II) sorption kinetic was tested through three reaction kinetic models: pseudo-first order, pseudo-second order and Elovich equation. FTIR analyses of chemically modified samples is also presented and discussed.

Imobilisana ljuska kajsije kao bisorbent teških metala

U radu je ispitana mogucnosti finalne formulacije biosorbenata na bazi kostica kajsija (Prunus armeniaca L.) kombinovanjem sa Na-alginatom i bentonitom u obliku granula pogodnim za primenu u realnim efluentima. U eksperimentalnom radu ispitan je uticaj granulacije biomase na biosorpcioni kapacitet prema Cu(II), Zn(II) i Pb(II). Najsitnija granulacija, koja je pokazala najbolje biosorpcione osobine imobilisana je u Na-alginatu, dok je kao vezivno sredstvo dodat bentonit, sto je uticalo da se stepen uklanjanja Cu(II) i Zn(II) poveca za oko 35% i Pb(II) za oko 60%. Dobijene granule su ispitane u saržnom sistemu na realnom uzorku. Rezultati ukazuju da se kompozitni biosorbent može uspesno koristiti u tretmanu voda kontamiiranih teskim metalima.