腐植酸与二价阳离子的相互作用

摘要

研究了水溶液中二价阳离子(Cu、Ni、Co和Zn)与商业化腐植酸(HAAl)和泥炭腐植酸(HAPs)的相互作用。研究采用修正的兰缪尔方程拟合了一系列吸附等温曲线。实验发现，HAAl对前述金属离子的最大吸附摩尔数分别为0.55±0.02 mmol/g，0.66±0.02 mmol/g，0.54±0.02 mmol/g，0.40±0.02 mmol/g，HAPs对它们的最大吸附摩尔数分别为：0.63±0.03 mmol/g，0.61±0.06 mmol/g，0.55±0.02 mmol/g，0.54±0.03 mmol/g。对于相同的序列，HAAl和HAPS之间的相互作用所吸收的热量值分别为2.4±1.0 mmol/g，8.4±0.9 mmol/g，18.3±0.9 mmol/g，10.6±0.9 kJ/mol，和18.4±1.2 mmol/g，15.9±1.4 kJ/mol，15.4±1.2 kJ/mol，15.0±1.2 kJ/mol。由于吉布斯自由能为负，离子络合作用过程必然伴随着熵的增加。%The adsorption behavior of divalent cations M2+(Cu, Ni, Co and Zn) with commercial humic acid (HAAl) and also withan extracted fraction of peat soil (HAPs) was followed in aqueous solution. The series of adsorption iso-therms were ifttedto a modiifed Langmuir equation. The maximum number of moles adsorbed gave:0.55 ± 0.02 mmol/g, 0.66 ± 0.02 mmol/g, 0.54 ± 0.02 mmol/g, 0.40 ± 0.02 mmol/g for HAAl and 0.63 ± 0.03 mmol/g, 0.61 ± 0.06 mmol/g, 0.55 ± 0.02 mmol/g, 0.54 ± 0.03 mmol/g for solid HAPs, for copper, nickel, zinc and cobalt, respectively. The same in-teraction followed calorimetrically gave endothermic values:2.4 ± 1.0 kJ/mol, 8.4 ± 0.9 kJ/mol, 18.3 ± 0.9 kJ/mol, 10.6 ± 0.9 kJ/mol and 18.4 ± 1.2 kJ/mol, 15.9 ± 1.4 kJ/mol, 15.4 ± 1.2 kJ/mol, 15.0 ± 1.2 kJ/mol for HAAl and HAPs, respec-tively, for the same sequence. Because all Gibbs free energies were negative. Complexation must beaccompanied by an increase in entropy.