Surface interactions during the removal of emerging contaminants by hydrochar-based adsorbents
Funding: The work was partially funded by the FCT (Grant FRH/BD/82696/2011) with National (OE) and European Union (FEDER, program COMPETE of QREN) funds. The authors are also grateful to Junta de Extremadura and FEDER (Fondo Europeo de Desarrollo Regional "Una manera de hacer Europa"), for financial help by project IB16108, and also to the program "Ayudas a grupos de la Junta de Extremadura" GR18150. Acknowledgments: The authors are grateful for the SAIUEX (Servicios de Apoyo a la Investigación de la Universidad de Extremadura) for their help in textural and surface chemistry analysis of the hydrochars. ; The aim of this work was to test activated carbons derived from hydrochars produced from sunflower stem, olive stone and walnut shells, as adsorbents for emerging contaminants in aqueous solution, namely fluoxetine and nicotinic acid. The adsorption capacity was determined by the chemical nature of the adsorbents, namely the presence of specific functional groups and their positive or negative ionization in aqueous solutions and also by steric factors. The activated carbons produced by air showed a higher adsorption capacity of fluoxetine, whilst the samples produced by carbon dioxide activation were more useful to remove nicotinic acid. In general, surface acidity was advantageous for fluoxetine adsorption and detrimental for nicotinic acid removal. The adsorption mechanisms involved in each case were discussed and related to the adsorbents characteristics. The maximum adsorption capacity, Q0, given by the Langmuir model was 44.1 and 91.9 mg g-1 for fluoxetine and nicotinic acid adsorption, respectively. ; publishersversion ; published