Estudio preliminar de la síntesis de ferritas de cobalto con potencial aplicación para la oxidación catalítica de efluentes cianurados.

Abstract

Cobalt ferrites have become an innovative catalyst due to their high performance in oxidative processes. In this study, cobalt ferrite was synthesized by hydrothermal method with precursors of iron and cobalt chlorides and cetyltrimethylammonium bromide (CTAB) and was used as catalyst for cyanide oxidation. The cobalt ferrite samples were synthesized with CoCl2·6H2O and FeCl3·6H2O in a Fe/Co molar ratio of 2. Two precipitating agents were tested (NH4OH at pH 10 and NaOH at pH 9 and 12). The reaction time tested were 18 and 24 h, and the reaction temperaturas were 150 °C and 180 °C. The solid obtained was filtered, washed and dried. Additionally, some simples were synthesized with the addition of CTAB in a Fe/CTAB molar ratio of 10:1. The samples were characterized by XRD, demonstrating the cubic structure of the ferrite at conditions of pH 12, precipitating agent NaOH, 18 h and 180°C. The addition of CTAB caused a slight decrease in particle size from 18,6 to 16,6 nm. The synthesis of CoFe2O4 with CTAB at 150 °C affected the formation of pure cobalt ferrite. The specific surface area was 55 m2/g and the Fe/Co molar ratio was 2,09, which was explained by the presence of hematite in the synthesized material. With this last material, a cyanide ion oxidation of 38% was accomplished after 8 h of stirring and aeration, with a reaction constant of 0,054 h-1. The material was stable in the cyanide solution since negligible leaching of Co (0,07%) and Fe (0,01%) was measured.