Abstract:Natural minerals from different localities in the Republic of Macedonia are selected for elimination of Cr(VI) ions from water resources. For that aim are selected: aksil (Kriva Palanka), trepel (Bitola), SiO 2 amorphous (Kozuf), pemza (Bojanciste). In this study, their adsorption capacity is analyzed using spectrophotometric method (UV/VIS Spectrophotometer). Results from the spectrophotometric analysis in all used examples gave us insight for the starting concentration of Cr(VI) before adsorption and concentration after adsorption. The physical, chemical and mineralogical characteristics of adsorbents are studied. XRD, TGA-DTA and FT-IR analysis are used for characterization of natural mineral materials. The surface area of the sorbents were measured by BET method. With aim to determine the optimum pH value for maximal removal of Cr(VI) ions, the point of zero charge, pH PZC , for investigated materials were obtained. The aim of the study is to select which adsorbent is more effi cient for elimination of Cr(VI) from water resources. According to obtained results all of them were successful in elimination of Cr(VI), but more effi cient and economic is trepel.

Abstract:The paper presents the results achieved during the process of nickel removal from aqueous solutions by adsorption on alumina (Aluminum oxide) in continuous conditions. The continuing experiments were conducted in a glass column with diameter of 16 mm and fi xed bed of adsorbent with quantity ranging from 30 to 115 g, adsorbent grains size from 1.0 to 2.0 mm, and retention time of 0.5 to 12 minutes. The quantity of nickel in the aqueous solutions was changed within the range of 0.045 up to 0.12 mg/l Ni. The analysis of the obtained experimental data defi ned the mutual affection of the retention time, the initial nickel concentration in the water, and the adsorbent quantity, i.e. the content of the adsorbent in the treated solution to the adsorbent capacity.According to the achieved results, logarithmic mathematical model showed best correlation between experimental and calculated values, also maximum nickel ions adsorption uptake onto the alumina were determined as 400 mg/g.

Removing hexavalent chromium from contaminated wastewater is very important because of toxicity to living organisms. Chromium is carcinogenic and mutagenic in very low concentration values (sub-ppm). The ability of the natural mineral (bentonite) for adsorption of hexavalent chromium, Cr(VI), from aqueous solutions was inve stigated. The infl uence of different physical and physicochemical parameters (pH, amount of adsorbent, adsorbate initial concentration) was examined. For characterization of adsorbent, classical chemical analysis thermogravimetric analysis (DTA/ TGA), XRD analysis, FTIR-analysis and determination of specifi c surface area by BET were performed. For quantitative monitoring of the dynamics of studied system for the presence of Cr(VI) ions in model solutions, the AAS and UV/ Vis analysis were used. The obtained experimental results were used for modeling of the equilibrium of the process through the application of software package MATLAB/Curve Fitting Toolbox., Following adsorption isotherms: Langmuir, Freundlich, Langmuir-Freundlich and Redlich-Peterson, are applied for analyzing the equilibrium of adsorbtion system Cr(VI) ions -bentonite.