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

Abstract

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 °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.