Kinetics and Thermodynamics of Pb (Ⅱ) Absorption by Black Seed Coat Superfine Powder of Pepper
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Abstract:
The black seed coat powder of pepper was used as the biological adsorbent in this study. First, the adsorption effects of particle sizes black seed coat powder of pepper on Pb2+ were discussed, and then the adsorption mechanism of the black seed coat superfine powder of pepper, was studied. The adsorption isotherm, thermodynamics and kinetics during adsorption process were investigated. Results showed that the black seed coat superfine powder of pepper exhibited an effective adsorbability of Pb2+among the coarse powder and fine powder, and the maximum adsorption quantity was 15.54 mg/g. When the initial concentration of Pb2+ was 10~90 mg/L, the adsorption equilibrium could be described by the Langmuir isotherm, which indicated that the biosorption of Pb2+ by superfine powder was a monomolecular layer adsorption. The biosorption kinetics was described by the pseudosecond-order model, which could be affected by film diffusion and intra-particle diffusion, and the former was the rate-limiting step. When the temperature was in the range of 25~45 ℃, thermodynamic parameters including the changes of free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were less than 0, suggesting that the adsorption process was spontaneous, exothermic process and belonging to physical adsorption.
