Marin Ugrina

Characterization and environmental application of iron-modified zeolite from the Zlatokop deposit

AbstractIn this paper, characterization of iron-modified zeolite (IMZ) from the Zlatokop deposit and its potential environmental application has been described. The modification procedure includes treatment of natural zeolite (NZ) with Fe(NO3)3 in an acetate buffer at pH = 3.6 followed by treatment with NaOH and NaNO3. The properties of NZs and IMZs have been determined by analysis of their chemical composition, specific surface area and by X-ray powder diffraction method (XRPD), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDS), TG-DTG and FTIR analyses. The chemical behaviour of modified zeolite has been examined in the zeolite-ultrapure water system at adjusted initial pH values in the range of 1.71–5.08, and also by determining the zero-point charge. The NZ and IMZ samples have been tested relative to the uptake of zinc ions. The results have shown that the capacity of IMZ samples for zinc ions is three-to-four times higher compared to the NZs. The balance of exchangeable ions be...

A study of kinetics and successive sorption/desorption of Zn and Cd uptake onto iron-modified zeolite

Abstract The sorption properties of iron-modified zeolite (IMZ) and the kinetics of zinc and cadmium uptake by the IMZ were investigated by the batch method. Two kinetic stages were observed, fast uptake up to 240 min, followed by slow uptake up to equilibrium. Kinetic results were fitted to the reaction and diffusion kinetic models, which indicated that intra-particle diffusion was the rate-limiting step. The Vermeulen’s approximation model was used to predict the quantity of Zn and Cd ions removed per gram of IMZ. The results of the successive sorption and desorption of Zn and Cd ions, with different electrolyte solutions, showed the best desorption efficiency with sodium salt solutions. Four successive repetitions of the sorption/desorption cycles showed a small difference between the amount of sorbed and desorbed Zn and Cd ions from the second to the fourth cycle. This indicates excellent sorption/regeneration properties of the IMZ.

Optimization of Removal Efficiency and Minimum Contact Time for Cadmium and Zinc Removal onto Iron-modified Zeolite in a Two-stage Batch Sorption Reactor

In highly congested industrial sites where significant volumes of effluents have to be treated in the minimum contact time, the application of a multi-stage batch reactor is suggested. To achieve better balance between capacity utilization and cost efficiency in design optimization, a two-stage batch reactor is usually the optimal solution. Thus, in this paper, a two-stage batch sorption design approach was applied to the experimental data of cadmium and zinc uptake onto iron-modified zeolite. The optimization approach involves the application of the Vermeulen’s approximation model and mass balance equation to kinetic data. A design analysis method was developed to optimize the removal efficiency and minimum total contact time by combining the time required in the two-stages, in order to achieve the maximum percentage of cadmium and zinc removal using a fixed mass of zeolite. The benefits and limitations of the two-stage design approach have been investigated and discussed.