Preparação e caracterização de compósitos obtidos de carvão ativado (borra oleosa) e óxido de ferro sintético visando aplicação em ambiente aquoso

Abstract

Composites were prepared with activated carbon (AC) of oily sludge impregnated with synthetic iron oxide in proportions 1:1 and 4:1, and temperatures of 400, 600 and 800 °C. Composites and CA were investigated and compared their capability to removal of organic (methylene blue, MB) and inorganic compounds (Cd2+ and Pb2+) in the aqueous system. These materials were characterized by analytical techniques of infrared spectroscopy, thermogravimetry, scanning electron microscopy, X-ray diffraction and Mössbauer spectroscopy (only iron oxide). Except CA, other materials showed varying degrees of magnetization in the presence of magnet hand. This characteristic was due to the presence of magnetite and/or maghemite and/or metallic iron confirmed by infrared spectroscopy and X-ray diffraction. Iron oxide it a stoichiometric and crystalline hematite confirmed mainly by Mössbauer spectroscopy. Composites and CA showed upper thermal stability to 300 °C. Tests removal capability of the MB, Cd2+, and Pb2+ were carried out at room temperature and pH~4.5. Adsorption capacity for MB for the CA was 141.6 mg g-1, this value was higher to that observed for the composites ranged between 128.8 (CP611) and 99.4 mg g-1 (CP811). The adsorption process for the MB showed better correlation values for the Langmuir isotherm, typical monolayer adsorption. The surface area was estimated indirectly by the maximum values of MB adsorption capacity of the studied materials, where AC of 273 m2 g-1 and the composites between 247 m2 g-1 (CP611) and 191 m2 g-1 (CP811). Composites showed excellent results for removal to Cd2+ ranged from 223 mg g-1 (CP411) to 503 mg g-1 (CP611), while Pb2+ ranged from 218 (CP841) to 486 mg g-1 (CP611) compared values found in the literature. Composites are also better represented by Langmuir. The CP611 composite showed higher adsorption affinity Cd2+ the higher presence magnetic phase while the CP811 had higher affinity for Pb2+ to having higher contribution of activated carbon in its composition. These materials are great for remediation of MB, Cd2+ and Pb2+.