Activation temperature dependence of Adonidia merrillii palm seed porous activated carbons textural properties. Adsorption of methylene blue in batch systems

Abstract

From a char of Palm seed (CSP), activated carbon at 973, 1073, and 1173 K was obtained (CASPs). These temperatures developed textural properties to favor the adsorptive properties. The CASPs percentage of burning decreased with the increase of the activation temperature from 76 to 26%. These products were obtained with a CO2 flow (as activating gas) and a short time of activation. The CASPs were characterized by mercury porosimetry, adsorption of N2, CO2, and methylene blue at 77, 273, and 298 K, respectively. Wide supermicropores were obtained for CASP1173 and narrow mesoporosity was achieved for CASP973 and CASP11073 (1.4–2.0 nm and 2.0–5.0 nm, respectively). Mercury porosimetry determined that the activated carbons have mesopores with diameters smaller than 50 nm and macropores with diameters greater than 50 nm. The use of Dubinin and Langmuir models showed that the adsorption occurred in the larger diameter micropores and smaller diameter mesopores of the highest and shortest diameters (above 3.85 mmol/g). The activated carbon at 973 K showed a higher methylene blue adsorption capacity (181.03 mg/g). The MB adsorption was determined by the diameters of the adsorbent pores. For this reason, a batch adsorption system to remove this contaminant was proposed.