DETERMINING THE INFLUENCE OF THE MEDIUM REACTION AND THE TECHNIQUE OF MAGNETITE MODIFICATION ON THE EFFECTIVENESS OF HEAVY METALS SORPTION

Development of reliable, environmentally safe and economically advantageous methods of water purification from heavy metals is the primary task for environmental protection. The effectiveness of sorption treatment and additional treatment of natural waters from ions of heavy metals with the use of modified magnetite was studied. The samples of magnetite obtained at the ratio of concentrations of iron (II) and iron (III) of 1:2; 1:1 and 2:1 and the samples modified by sodium sulfide were used as a sorbent. Experimental studies revealed that the sorption capacity of magnetite by ions of heavy metals increases at the increase in the ratio [Fe2+]/[Fe3+] from 1:2 to 2:1. The influence of pH of the medium on the effectiveness of sorption of heavy metal ions on magnetite was studied. It was shown that the sorption capacity of magnetite for ions of copper, zinc, nickel and cadmium increases at the increase in pH of the medium from 6.0 to 8.6 due to partial hydrolysis of heavy metal ions. An increase in sorption capacity of magnetite occurs when it is modified by guanidine, thiosemicarbazide and sodium sulfide, which makes it possible to reduce residual concentrations of heavy metals to μg/dm3. The use of magnetite modified by sodium sulfite, obtained at К=2, makes it possible to completely remove cadmium ions from water and reduce copper concentration to 1.2 μg/dm3. This proves the appropriateness of using these sorbents for additional treatment or deep purification of water from ions of heavy metals. It was shown that it is appropriate to use magnetite for extraction of heavy metal ions from water in the presence of hardness ions, which do not affect the selectivity of this sorbent for ions of heavy metals. Thus, based on the obtained results of sorption purification of water from ions of heavy metals while using magnetite, we proposed a fundamental technological circuit for treatment of wastewater of nuclear power plants at discharge to water bodie