Remoção do corante azóico Direct Blue 151 de meio aquoso usando biocarvão produzido a partir de borra de café como adsorvente

Abstract

Azo dyes are considered refractory and cumulative organic compounds, and may cause various environmental damages if the colored wastewater has not the appropriate treatment. In this work, the coffee grounds biochar (BBC) was used to remove the azo dye Direct Blue 151 (DB151) from aqueous solution. Biochars can be produced trough a thermochemichal conversion simple process like pyrolysis, BBC production was carried out by slow pyrolysis in a muffle furnace with a control rate of heating of 10 °C/min up to 600 °C, staying for 2 hours after reach that temperature. The physicochemical properties of BBC were analyzed trough infrared spectroscopy (FTIR), BET surface area and point of zero charge (PZC). The adsorbent mass, dye concentration, pH, temperature and contact time influence were evaluated. The results obtained in this study showed that BBC is a mesoporous material rich in OH- and CH2 functional groups. Futhermore, BBC had a great performance comparable to activated carbon, and pH and temperature variation did not affect significantly the adsorption process. Thus, biochar was extremely favorable to adsorption of DB151 and a potential adsorbent for azo dyes, it also can stimulate a circular economy in Brazil.