Síntese de carvão ativado de resina fenólica por ativação físico-química com cobre e CO2

Abstract

Phenolic resins are plastics referred to as thermosets or thermorigid. Being rigid plastics, they are used in various industries. However, the waste generated cannot be recycled nor properly disposed of. Therefore, this study proposes the synthesis of phenolic resins for later use as raw material in the production of activated carbon, as they are resins with a high carbon content. The use of synthetic phenolic resin for this purpose aims to optimize reaction parameters for activation. The optimization discussed will serve for future implementations of recycling waste from Bakelite (phenolic resin) for the generation of activated carbon. The proposed work highlights the synthesis of activated carbons derived from synthetic phenolic resin, applying a new physicochemical activation method, based on the use of copper (Cu) and carbon dioxide (CO2). The carbons were characterized by FTIR, PXRF, Raman Microscopy, FE-SEM, and N2 Physisorption measurements. In this study, synthesis and activation parameters were optimized, resulting in the production of carbons with different proportions of Cu (CA; CA-Cu/0.2%; CA-Cu/0.4%; CA-Cu/0.8% and CA-Cu/2.5%). The results showed that lower Cu contents favored higher yields and lower activated carbon Burn-off. The findings further revealed that the specific surface area increases up to an optimal value (CA-Cu/0.4%), according to the methylene blue index (SAM). The FTIR and Raman Microscopy characterizations indicated few bands related to functional groups, and that the structure of the activated carbons is predominantly amorphous. The PXRF analysis was able to confirm the amount of Cu introduced into the activated carbons. Microscopic images showed that the higher the percentage of Cu introduced into the carbon, the greater the pore formation. Moreover, the N2 physisorption measurements indicated the formation of carbons with surface areas (SBET) of ~1700 m2 g−1, using physicochemical activation (Cu + CO2). Using the physical method (CO2), a surface area of 1117 m2 g−1 (CA) was obtained. Isothermal tests, using methylene blue (MB), showed that the adsorption of the materials follows the Langmuir model, presenting the highest qm value for CA-Cu/0.4% (815 mg g−1), compared to CA (205 mg g−1). The kinetic model that best describes the process was pseudo-second order. The removal of Cu from the carbonaceous structure of the CA-Cu/0.4% material shows that Cu plays an active role in the adsorption process. Additionally, regeneration tests of CA-Cu/0.4% showed that the material can be reused for up to three cycles. Therefore, the developed methodology demonstrates that Cu can contribute synergistically to the production of activated carbons with high surface area using CO2. Thus, it promotes the development of versatile, reusable materials with high added value. Furthermore, this study generated a patent that was filed with the National Institute of Industrial Property (INPI) and resulted in the production of a full article that characterizes the developed materials and shows their application.