Europium removal from aqueous solutions by oxidized biochar prepared from waste palm tree fronds
Efthalia Georgiou, Ioannis Ioannidis, Ioannis Pashalidis, Dang Duc Viet, Toshiki Tsubota, Dimitrios Kalderis
Abstract
Palm oil is a product of major economic importance worldwide however, palm tree cultivation generates large quantities of palm fronds as waste. In this work, the sorption of Eu3+ from aqueous solutions by oxidized biochar derived from palm tree fronds was studied at pH 3 by batch type experiments under ambient conditions. Following biochar production, the sample was oxidized using HNO3 to increase the oxygen-containing moieties on its surface. The oxidized biochar was characterized through surface and spectroscopic techniques. As indicated by the coefficient of determination value of 0.99, Eu3+ adsorption was best described by the Langmuir isotherm model. The optimum adsorption capacity was determined at qmax= 0.81 mol kg-1. Adsorption was an entropy-driven process and followed the 2nd order kinetics, reaching a plateau value of 50% relative adsorption within 60 min. Furthermore, Fourier Transform InfraRed spectroscopic data and the effect of ionic strength indicated that adsorption proceeded via the development of inner-sphere complexes between Eu3+ and the carboxylic groups on the biochar surface.