Adsorption Kinetics of Low Mercury Solution with Durian Shell and Activated Carbon

BACKGROUND The direct discharge of Hg(Ⅱ) is harmful to the environment. At present, activated carbon is used to remove it, but the production of activated carbon through high-temperature pyrolysis and activation is very expensive. OBJECTIVES To investigate the adsorption difference and mechanism on low-concentration Hg(Ⅱ) for durian shell, coconut shell activated carbon and activated carbon fiber under different conditions. METHODS The remaining Hg(Ⅱ) in the adsorption solution was determined by atomic fluorescence spectrometry. The adsorb kinetic parameters of different adsorbents were determined by Lagergren pseudo-second-order kinetic model. RESULTS In the Lagergren pseudo-second-order kinetic model, the maximum adsorption capacity (QM) of the three materials was as follows: activated carbon fiber (5.61μg/g)>durian shell (1.68μg/g)>coconut shell activated carbon (0.96μg/g). The adsorption test and thermodynamic equation showed that the adsorption of Hg(Ⅱ) by the three materials was spontaneous (ΔG < 0). The adsorption of Hg(Ⅱ) by coconut shell activated carbon was mainly physical adsorption (ΔH>0), while the adsorption of durian shell was an endothermic process (ΔH < 0). Due to the increase of temperature, the adsorption rate and adsorption capacity were improved. CONCLUSIONS Durian shell from a wide range of sources can be used as an effective adsorbent to treat wastewater containing Hg(Ⅱ).