氧化锰改性活性炭的优化制备及其对Cd(Ⅱ)的吸附研究

PREPARATION OPTIMIZATION OF ACTIVATED CARBON MODIFIED BY MANGANESE OXIDE AND ITS ADSORPTION OF Cd(Ⅱ)

采用浸渍焙烧法制备了活性炭负载氧化锰的除镉(Cd(Ⅱ))吸附剂,通过L_9(3~4)正交试验确定最优制备条件如下:浸渍时间7 h,KMnO_4质量分数2.7%,焙烧温度470℃,焙烧时间2.5 h。通过BET、SEM、FTIR、XRD对改性活性炭(MOAC)进行表征,研究了pH值、吸附时间、初始浓度、吸附温度等对Cd(Ⅱ)吸附效果的影响。结果表明:MOAC表面烃基含氧官能团增多,氧化锰以MnO_2的形式负载到其表面;当MOAC的投加量为0.5 g/L,Cd(Ⅱ)的初始浓度为50 mg/L,溶液pH值为6.0,温度为298 K,吸附时间为12 h时,MOAC对Cd(Ⅱ)的吸附量高达84.15 mg/g,吸附过程符合准二级动力学方程和Langmuir等温吸附方程,热力学参数表明该吸附过程为放热、自发的过程。

Activated carbon, as the cadmium adsorbent, loaded with manganese oxide, was prepared by impregnated-roasting method. The optimal preparation conditions determined by orthogonal experiment were as follows： Impregnation time of 7 h, KMnO4 mass fraction of 2. 7% , roasting temperature of 470 ℃ , roasting time of 2.5 h. The modified activated carbon was characterized by BET, SEM, FTIR and XRD. The adsorption effect of Cd（Ⅱ） was researched as a function of various factors such as pH, adsorbent time, initial concentration and adsorbent temperature. The results indicated that the amount of oxygen- containing functional groups increased and MnO2 was loaded on modified activated carbon. The adsorption capacity of the MOAC could reach 84. 15 mg/g under the conditions of the adsorbent dosage of 0.5 g/L, the initial Cd（Ⅱ） concentration of 50 mg/L, pH of 6.0, adsorption temperature of 298 K, and the adsorption time of 12 h. The adsorption process fit the pseudo-second-order and Langmuir equation. Thermodynamic parameters revealed that the cadmium adsorption process was exothermic and spontaneous.