Sorption purification of natural and waste water from Hg(II), Cd(II) and Pb(II) by natural zeolite of Hotynetskoe deposits

Abstract

The work’s theme is connected with the solution of the problem of leveling the waters pollution by soluble compounds of heavy metals by means of their sorption isolation and concentration.

The purpose was to systematically study the sorption of Hg(II), Pb(II) and Cd(II) by a natural zeolite and to develop a method for purifying natural and waste water contaminated with these metals.

The Hotinetskoe zeolite was used as a sorption material. The elemental composition of the mineral was judged from the data of energy-dispersive X-ray spectroscopy, the phase composition was studied by X-ray diffractometry. The concentration of mercury, lead and cadmium was monitored by atomic absorption spectrometry. Sorption was studied in static conditions by the method of limited volume with periodic mixing. Determined the optimal conditions of sorption (acidity of the medium and time), the sorption capacity of the material. Based on the data obtained, sorption isotherms were constructed. The proposed sorption chemistry was judged by IR spectroscopy, comparing the IR spectra of the zeolite before and after the sorption of each of the metals.

The chemical composition of the mineral under study is established in which aluminosilicates with a regular crystal structure predominate: montmorillonite, clinoptilolite, illite, and also cristobalite and quartz. The effect of the acidity of the medium and time on the degree of metals extraction from aqueous solutions was established: for Hg(II) and Cd(II)> 95%, for Pb(II) ~ 64% with acidity of the medium close to neutral; the time of establishment of sorption equilibrium is 45-55 minutes for lead and ~ 60 minutes for mercury and cadmium. The sorption capacity of the mineral for each of the metals are 0.06 mmol/g for mercury, 0.31 mmol/g for cadmium and 0.17 mmol/g for lead. For all the studied "zeolite-metal" systems, sorption isotherms have been constructed that have a convex shape with an outlet to saturation. On the basis of the comparison of the IR spectra of the mineral before and after the sorption of metals, an assumption is made about the probable chemistry of the proceeding process.

The data obtained form the basis of the method for purification of waters contaminated with mercury, lead and cadmium, and can be used in the practice of laboratories dealing with environmental technologies