Adsorption of Estradiol from aqueous solution by hydrothermally carbonized and steam activated palm kernel shells

Abstract In this study, Ethinylestradiol was removed from aqueous solution (maximum removal 83.1%) by hydrothermally carbonized and steam activated carbon adsorbent prepared from palm kernel shells. The effects of varying adsorbent mass, pH, temperature and concentration of Ethinylestradiol on adsorption were studied. It was found that pseudo second order kinetic model is able to describe well the adsorption of Ethinylestradiol. Thermodynamic studies showed that the adsorption process was mainly chemisorption as the calculated activation energy for adsorption was 60.4 KJmol−1. Adsorption was considered to take place between the functional groups on the adsorbent and those on the Ethinylestradiol molecule. The characterization showed that adsorbent was mesoporous with specific surface area of 320 m2g−1, it had several oxygen-containing functional groups, and defects in its graphitic structure (ID/IG ratio ∼ 2.2). Novelty statement: High carbonization temperatures (300°C - 600°C) followed by high-temperature steam activation (600°C - 1000°C) have been used to prepare carbon adsorbents over the past decades. In this work, the novelty lies on lower processing temperatures. Hydrothermal carbonization realized at 200°C and following steam activation at 500°C will produce an efficient carbon adsorbent, which is shown in this study. The lower carbonization-activation temperatures produce adsorbents with higher amount of functional groups beneficial to adsorption, and decreases energy costs of the production.