原位固化黑荆树单宁对La^(3+)、Pr^(3+)、Nd^(3+)的吸附特性

Adsorption Property of in Situ Immobilized Black Wattle Tannin to La^(3+),Pr^(3+) and Nd^(3+)

以富含单宁的黑荆树树皮为原料,通过甲醛交联剂原位固化黑荆树单宁制备吸附材料,研究该吸附材料对轻稀土离子La3+、Pr3+、Nd3+(RE3+)的吸附特性。实验表明:该吸附材料对La3+的吸附最适宜的pH为5.0左右,对Pr3+、Nd3+的吸附最适宜的pH为5.5左右,此时pH升高或降低,吸附量有较大幅度下降。和pH因素的影响相比较,温度对平衡吸附量影响较小,反应温度为303K时,原位固化黑荆树单宁对RE3+的吸附效果最好。当RE3+溶液的初始浓度为5.0mmol·L-1时,在温度为303K和最适宜的pH条件下,吸附剂用量为0.10g,平衡吸附量可达到La3+为217.26mg·g-1,Pr3+为228.56mg·g-1,Nd3+为329.76mg·g-1,其吸附等温线符合Freundlich方程。这种吸附剂对RE3+的吸附动力学可用拟二级速率方程来描述,由拟二级速率方程计算所得到的平衡吸附量与实测值的偏差在7%以内,具有很好的一致性。

A new kind of adsorbent was prepared from the bark of black wattle being rich of tannin;furthermore,the cross-linking reaction of formaldehyde was used to immobilize tannin in situ to get the adsorbent.The adsorption property of this new adsorbent to ions of light rare earth such as La^3＋,Pr^3＋ and Nd^3＋（RE^3＋） in aqueous solution was investigated.Results show that the optimum pH value of this adsorbent to La^3＋ is about 5.0,while the optimum value of Pr^3＋ and Nd^3＋ is about 5.5.The equilibrium adsorption capacity will decline significantly when the pH value of reaction system is changed from the optimum pH value.Compared with the effect of pH value,the influence of the temperature on the equilibrium adsorption capacity is weaker,and at 303 K the equilibrium adsorption capacity of this adsorbent to RE^3＋ is optimal.At 303 K and the optimum pH value,when the initial concentration of RE^3＋ solution is 5.0 mmol·L-1 and the dosage of adsorbent is 0.10 g,the equilibrium adsorption capacity of this adsorbent to La^3＋,Pr^3＋ and Nd^3＋ are 217.26,228.56 and 329.76 mg·g-1,respectively.The adsorption isotherm can be described by the Freundlich equation.This adsorption kinetics data of this adsorbent to RE^3＋ is fitted with the pseudo-second-order rate model well and the equilibrium adsorption capacities calculated by the model are consistent with the experimental data with the warps in 7 %.