ZEOLITE-BASED NANOCOMPOSITE MODIFIED WITH HYDRATED IRON OXIDE (III) FOR REMOVAL OF HEAVY METALS

Abstract

The theoretical approach, which allows us to control the formation of aggregates incorporated into porous matrixes has been developed and verified. It was established that the important parameter is the pH of a precipitator: the higher this value, the larger aggregates are formed. Based on the approach, a method of obtaining the composite based on naturalclinoptilolite-based zeolite containing nanoparticles of hydrated iron oxide has been developed. The porous structure of composite sorbents has been studied. The sorbents were investigated using XRD, TEM, SEM methods. Weakly basic precipitator has been recommended in order to obtain the nanosized aggregates of the modifier. During the synthesis, porous structure of the zeolite substrate is transformed. Acid activation promotes the development of the sorbent surface, which leads to the dissolution of the elements present in clinoptilolite. The increase in the surface of the modified sorbents is due to highly ordered pores in the range of 1-2 nm, as the microporosity decreases after acid activation. Impurities block ordered pores, and activation opens them. But after modification, these pores are partially blocked. This is probably caused by the precipitation of oxide dissolution products in alkaline media. Despite this fact, all the obtained samples of composite sorbents are mostly mesoporous. Sorption of di- and trivalent cations from multicomponent solution was studied. It was found that the presence of a nanoscale modifier accelerates ion absorption. The modified zeolite improves sorption of metals, which are not related to d-elements. The removal degree of Pb2+ ions reaches 97%. The isotherms of Pb2+sorption are fitted with Freundlich model. In addition to the lead extraction from aqueous solutions, the sorbent could be also recommended for water softening.