盐泥吸附剂对直接染料的平衡吸附行为和热力学性质研究

Adsorption and thermodynamics of direct dyes on salt sludge adsorbents

以染料废水处理用盐泥吸附剂的开发为目的，在静态吸附条件下，研究了含镁盐泥对直接大红、直接深蓝和直接黑3种直接染料的吸附行为，并对吸附过程的热力学进行了分析。结果表明，吸附平衡数据都能够较好地符合Lang-muir和Freundlich吸附等温方程，但Langmuir方程能够更好地描述吸附等温线。在25～30℃范围内，3种直接染料在盐泥上的吸附是一个吸热过程，同时伴随着熵值的增加，反应的吉布斯自由能变小。吸附是物理和化学吸附并存的吸附过程，主要推动力为化学键力（化学吸附），同时可能存在范德华力（物理吸附），吸附焓变在74．120～87．332kJ／mol之间。

A new type of adsorbent was prepared from salt sludge. Adsorptions of three direct dyes in aqueous solutions on the salt sludge adsorbent were studied under static conditions. The thermodynamic of the adsorptions were also analyzed. Equilibrium data fitted well with Langmuir and Freundlich model in the range of 200 600 mg/L. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The adsorption of the salt sludge was endothermic in nature and was accompanied with an increase in entropy and a decrease in gibbs energy in the range of 25 - 35℃. The numerical values of sorption gibbs energy （74. 120 - 87. 332 kJ/mol） suggested that the adsorption behavior may be dominated by chemical bond forces （chemical adsorption） , and accompanied with van der Waals forces （physical adsorption）.