花椒籽黑种皮超微粉吸附Pb2+的动力学及热力学研究

Kinetics and Thermodynamics of Pb (Ⅱ) Absorption by Black Seed Coat Superfine Powder of Pepper

摘要:

本文以花椒籽黑种皮粉为生物吸附剂，首先探讨了不同粒度花椒籽黑种皮粉对Pb2+的吸附特性影响，进而选择吸附性最强的花椒籽黑种皮超微粉探究其对Pb2+的吸附机理，系统研究了花椒籽黑种皮超微粉对Pb2+的吸附等温线、热力学及动力学特征。结果表明，花椒籽黑种皮超微粉对Pb2+具有最高的吸附效果，最高吸附量为15.54 mg/g。Pb2+初始质量浓度为10~90 mg/L时，花椒籽黑种皮超微粉对Pb2+的吸附效果符合Langmuir模型，说明该吸附为单分子层吸附。吸附动力学方程符合准二级速率方程，且受薄膜扩散和内扩散共同影响，其中薄膜扩散为主要速率控制步骤。吸附温度为25~45 ℃，吸附自由能变量（ΔG）、焓变量（ΔH）和熵变量（ΔS）均小于零，表明花椒籽黑种皮超微粉对Pb2+的吸附是自发的、放热的物理吸附。

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.