The adsorption of Congo red onto titanium dioxide (TiO2) material has been investigated at batch conditions. The effects of contact time (0–60 min), initial pH (3–11), agitation speed (100–500 rpm), temperature (298–343 K), adsorbent dosage (0.5–2 g/L), and Congo red concentration (5–15 mg/L) on the Congo red adsorption by TiO2 have been studied. The kinetic parameters, rate constants, and equilibrium adsorption capacities were calculated and discussed for each kinetic model. The adsorption of Congo red onto TiO2 is well described by the pseudo-second order equation. The adsorption isotherm follows the Langmuir model, providing a better fit of the equilibrium data. The batch adsorption experiments were carried out to optimize the physical parameters on the Congo red removal efficiency. It has been found that 152 mg/g at 25 C is removed. The thermodynamic parameters indicate the spontaneous and endothermic nature of the adsorption process with activation energy (Ea) of 64.193 kJ/mol. The positive value of the entropy (ΔS ) clearly shows that the randomness is decreased at the solid–solution interface during the Congo red adsorption onto TiO2, indicating that some structural exchange may occur among the active sites of the adsorbent and the ions.

中文翻译：

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二氧化钛作为吸附剂从水溶液中去除刚果红 (CR) 的实验研究、平衡和动力学模型

已经在批量条件下研究了刚果红在二氧化钛 (TiO2) 材料上的吸附。接触时间（0-60 分钟）、初始 pH（3-11）、搅拌速度（100-500 rpm）、温度（298-343 K）、吸附剂用量（0.5-2 g/L）和刚果的影响已经研究了 TiO2 对刚果红吸附的红色浓度 (5-15 mg/L)。计算并讨论了每个动力学模型的动力学参数、速率常数和平衡吸附容量。准二阶方程很好地描述了刚果红在 TiO2 上的吸附。吸附等温线遵循朗缪尔模型，提供了更好的平衡数据拟合。进行批量吸附实验以优化刚果红去除效率的物理参数。已经发现在 25°C 下去除了 152mg/g。热力学参数表明吸附过程的自发和吸热性质，活化能 (Ea) 为 64.193 kJ/mol。熵（ΔS）的正值清楚地表明，在刚果红吸附到 TiO2 上时，固溶界面处的随机性降低，表明吸附剂的活性位点和离子之间可能发生一些结构交换。