硫酸中硫脲在纯铁上的吸附

AN INVESTIGATION INTO THE ADSORPTION OF THIOUREA ON PURE IRON IN SULPHURIC ACID

一、引言有机物在电极表面上的吸附过程,可提供吸附分子之间以及它们和电极表面相互作用的有用信息。实践上,它与腐蚀抑制、化学电源、电镀、有机电合成等直接相关。汞电极表面上的吸附行为已有大量报道。固体电极上的研究困难较多,文献报道只涉及为数不多的一些体系。本工作研究20～60℃温度区间,0.5～2.0mol·dm^(-3)H_2SO_4中硫脲(TU)在纯铁上的吸附行为,通过对实验结果的分析找出相应的吸附等温式,确定有关的热力学参数。

The adsorption behaviour of thiourea (TU) on pure iron was investigated in 0.5～2.0 mol·dm^(-3) H_2SO_4 over the temperature range of 20～60℃. The process was treated as a sabstitutional adsorption process. The degree of surface coverage increased with temperature and TU concentration. It was shown that at low TD concentrations the adsorption behaviour followed a Flory-Huggins isotherm with negligible lateral interaction. TU molecules were parallely adsorbed on the surface. At higher TU concentrations the molecules did not change their orientation, but the adsorption behaviour followed a Frumkin-type isotherm with strong lateral repulsion. The Gibbs energy, enthalpy and entropy of adsorption were calculated. The effect of temperature on the degree of surface coverage was at tributed to entropy, rather than enthalpy.