Experimental measurement and modeling of Hg(II) removal from aqueous solutions using Eucalyptus globulus bark: Effect of pH, salinity and biosorbent dosage

Abstract

Different experimental conditions were tested in order to optimize the Hg(II) removal by Eucalyptus globulus bark. Response surface methodology was applied to extract information about the significance of the factors and to obtain a model describing the sorption. The results were generated through the design of experiments by applying the methodology of a three-factor and three-level Box-Behnken design. The factors tested were pH (4.0, 6.5, and 9.0), salinity (0, 15, and 30), and biosorbent dosage (0.2, 0.5, and 0.8 g dm-3) to evaluate the Hg(II) removal using realistic conditions, such as contaminated natural waters with an initial Hg(II) concentration of 50 µg dm-3. The optimum response provided by the model was 81% of the metal removal under the optimal operating conditions: a pH value of 6.0, no salinity, and a biosorbent dosage of 0.55 g dm-3. Concerning the kinetic, the pseudo-second-order equation fitted better to the experimental results with R2 between 0.973 and 0.996. This work highlights the promising valorization of this biomass, which is an industrial byproduct and makes available information about the influence of the variables for Hg(II) removal in water treatment processes.