Preparação de um auxiliar de floculação inorgânico a partir da modificação de Zeólita com Fe(III)

Abstract

The increase in population and the expansion of industrialization demand high consumption of treated water. However, Water Treatment Plants can not meet this demand in an efficient and agile way, arising the need for alternative chemical applications for this purpose. Frequent difficulties in the flocculation process can occur by the formation of low settling precipitates or fragile flocs that are easily fragmented under hydraulic forces in decanters and sand filters. The flocculation aids favor flocculation, increasing the decantation speed and the stiffening of the flakes, making treatment effective and faster. Zeolites are negatively charged aluminosilicates and possess alkali metal cations as counter ions, thereby being able to act as ion exchangers. In this work, an inorganic flocculation aid was prepared from the natural zeolite of the type clinoptilolite modified with Fe3+. This product was tested in the treatment of water with different turbidities. The zeolite was modified with monovalent cations (Na+ and NH4 + ) to obtain the quasi-homoionic zeolite, and later the ion exchange with Fe3+ ions was done. The ion exchange capacity of zeolite modified with Fe3+ ions was evaluated by means of Atomic Absorption Spectroscopy, with efficient adsorption of iron ions to the zeolitic structure. The identification of Fe3 + ions in the zeolite material treated with iron (ZFe) was done through the Mössbauer Spectroscopy, and only the presence of Fe3+ on the surface was verified. Through the Zero Load Point (pHPCZ), the effect of pH on the surface charge of ZFe was evaluated, with values close to 8.0 being found. These values optimized the jar test, with considerable floc formation being observed. The crystalline structure of ZFe was analyzed by X-ray diffraction and was not conclusive for the presence of Fe3+ oxides. The determination of total iron in the modified material was performed by the 1,10- phenanthroline technique, and the determined iron amounts are in accordance with the values established by the potability standards of Ordinance 2914/11 of the Ministry of Health which is 0.3 mg L-1 . After characterization, ZFe was tested as a flocculation aid by jar test, through which a significant reduction of color (97.63%) and turbidity (97.25%) of the decanted water were identified, values more expressive than Presented in the results of the tests using only the application of aluminum sulphate coagulant, which presented 89.06% in the removal of color and 87.86% in the removal of turbidity. Therefore, the application of ZFe can significantly increase the efficiency of the flocculation process in surface water treatment.