摘要
用自行设计的动力学装置研究了酸性条件下Pb在红壤表面的反应动力学能量特征。结果表明,酸性条件下,Pb吸附分为快反应和慢反应。用一级动力学方程拟合的Pb最大吸附量,随酸度增加显著下降,随温度升高提前达到平衡。用扩散速率常数计算的活化能(△E*)随酸度的增加而增加,Pb扩散需克服的能障加大;△H值为正,温度升高可促进Pb的扩散;△S值均为负,说明吸附反应使体系有序度增加。原液pH为4.5和5.6时,流出液的pH急剧下降;pH3.8和3.3时流入液比流出液的pH高,是由于土壤的缓冲作用和土壤表面质子化;当溶液中H+超过一定数量后,反应初期的H+消耗是快反应过程,H+对矿物的溶蚀成为速率控制步骤。
Energy characteristics of the reaction kinetics of Pb on red soil surface under acidic conditions were investigated by using a home made dynamic device. The results showed that Pb adsorption could be divided into rapid and slow reactions. The maximal Pb adsorption fitted by the first order equation remarkably decreased with increase in acidity and reached equilibrium in advance with increase in temperature. Activation energy （△E^＊） of Pb diffusion was calculated by using b value of the rate constant of Parabolic Diffusion Low and increased with increase in acidity, which reflected that the energy barrier to be overcome by Pb diffusion would rise up and the rate of diffusion in Pb adsorption decrease accordingly. Enthalpy of activation（△H）was positive in value and rising temperature could contribute to Pb diffusion. Entropy of activation （△S） was negative in all cases, suggesting that system could improve its degree of order, pH of effluent drastically dropped when the influent solution was pH 4.5 and pH 5.6. There was the consumption process of H ion by using influent of pH 3.8 and 3.3, which was attributed to soil buffer mechanism. H^＋ consumption was rapid at the initial stage of the reaction. Since H^＋ dissolution of minerals became a controlling process.
出处
《生态环境》
CSCD
北大核心
2008年第5期1807-1811,共5页
Ecology and Environmnet
基金
土壤与农业可持续发展国家重点实验室的开放基金(0751010004)
国家杰出青年科学基金(40325001)
中科院知识创新领域前沿项目(ISSASIP0202)
河南农业大学博士基金(30200165)
关键词
土壤酸化
表面反应动力学
能量特征
铅离子
soil acidification
surface reaction
energy characteristics
lead ions
