Producing Efficient Adsorbents from Kraft Lignin for the Removal of Contaminants from Water-A Full Factorial Design

This work aimed at optimizing the preparation of activated carbon (AC) from Kraft lignin for the adsorption of methylene blue (MB) and amoxicillin (AMX) from water. A full factorial design of three factors (precursor:activating agent (H3PO4) ratio, pyrolysis temperature, and residence time) at two levels was used to optimize the AC production. Eight AC products were obtained and evaluated considering the following responses: product yield, specific surface area (SBET), energy consumption, and adsorptive removal of the contaminants under study. The produced AC presented satisfactory SBET, ranging between 750 and 1335 m2 g-1, and efficient adsorption of MB and AMX from water, achieving up to 99% removal under the studied experimental conditions (100 mg L-1 of MB and AMX solution and material dose of 1 g L-1). Statistical analysis showed that product yield and energy consumption for AC production were influenced by temperature and residence time. The determination of a desirability function indicated a precursor/H3PO4 ratio of 1:2, pyrolysis at 700 degrees C, and residence time of 60 min as the optimal production conditions. The optimized AC presented SBET 1335 m2 g-1 and maximum adsorption capacity of 210 and 280 mg g-1 for MB and AMX, respectively.