PreparaÃÃo de carvÃo ativado a partir de borra de cafÃ: uso como adsorvente e como suporte catalÃtico para a remoÃÃo de poluentes orgÃnicos em meio aquoso. / Activated carbon production by spent coffee grounds: use as adsorbent and catalytic support for organic pollutants removal from aqueous medium

CÃnthia Soares de Castro

In this work, the preparation of activated carbons (AC) using spent coffee grounds and three activating agents CO2 (AC CO2), water vapor (AC H2O) and K2CO3 (ACK) were evaluated. These AC showed microporous nature with high surface area, except for AC CO2. These materials, as well the commercial AC (ACC) were tested as adorvents for the organic contaminant models methylene blue (MB) and phenol showing high adsorption capacity. The activating agents led to AC with distinct surface properties that strongly affected the molecules adsorption process. Tests varying solutions pH of MB and phenol showed that adsorption process depends on both porosity and surface groups present on carbons. The AC with the highest surface area (ACK) as well the ACC were used as supports for iron impregnation for the production of the composites ACK/Fe and ACC/Fe, respectively with high iron oxide dispersion and stability. These materials were tested in the H2O2 decomposition and MB oxidation using H2O2 as oxidizing agent. They were also submitted to a reduction treatment with H2 aiming the iron oxide partially reduction (ACK/Fe reduced and ACC/Fe reduced). The catalytic tests showed high activity H2O2 decomposition and MB oxidation. Although the reduced materials presented higher H2O2 decomposition capacity a slightly reduction in the MB oxidation activity was verified. Moreover, the composites based on AC from coffee waste were more active in both H2O2 decomposition and on the dye oxidation, presenting higher MB removal and more oxidation intermediates formation.

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