高比表面植物基活性炭吸附水中对硝基苯胺的性能及影响因素

以互花米草与棉秆为原料,以KOH为活化剂,制备了2种低成本高比表面微孔植物基活性炭SA-AC和CS-AC,通过静态实验研究了其对水溶液中对硝基苯胺的吸附特性,测定了溶液pH值、吸附剂剂量、溶液温度对吸附的影响,并探讨了等温吸附行为及其热力学性质.结果表明,在KOH与炭化料的质量比(剂料质量比)为3∶1、活化温度为800℃、活化时间为1.5 h条件下,活化制备的互花米草活性炭SA-AC和棉秆活性炭CS-AC的比表面积分别为2 825 m2.g-1和2 135 m2.g-1,微孔容积分别为1.192 cm3.g-1和1.011 cm3.g-1,对水溶液中对硝基苯胺的Langmuir最大吸附量分别为719和716 mg.g-1,远高于商业活性炭ST1300.溶液pH值和温度对吸附有较大影响,在低温及中性条件下有利于制备活性炭对水溶液中对硝基苯胺的吸附.Freundlich与Redlich-Peterson模型能很好地描述对硝基苯胺在2种活性炭上的吸附行为;热力学研究表明,吸附标准吉布斯自由能变ΔG0与标准焓变ΔH0均为负值,表明对硝基苯胺在这2种活性炭上的吸附属于自发的放热吸附过程;吸附标准熵变ΔS00,说明对硝基苯胺在活性炭表面上的迁移比在溶液中受到了更大的限制.

Adsorption Behavior and Influence Factors of p-Nitroaniline on High Surface Area Activated Carbons Prepared from Plant Stems

Low-cost and high surface area microporous activated carbons were prepared from Spartina alternilora and cotton stalk with KOH activation under the conditions of impregnation ratio of 3.0, activation temperature at 800 degrees C and activation time of 1.5 h. The adsorption behavior of p-nitroaniline on the activated carbons was investigated by batch sorption experiments. The influences of solution pH value, adsorbent dose and temperature were investigated. The adsorption isotherm and thermodynamic characteristics were also discussed. The Spartina alterniflora activated carbon (SA-AC) has a high surface area of 2825 m2 x g(-1) and a micropore volume of 1.192 cm3 x g(-1). The BET surface area and micropore volume of the cotton stalk activated carbon (CS-AC) are 2135 m2 x g(-1) and 1.011 cm3 x g(-1), respectively. The sorption experiments show that both the activated carbons have high sorption capacity for p-nitroaniline. The Langmuir maximum sorption amount was found to be 719 mg x g(-1) for SA-AC and 716 mg x g(-1) for CS-AC, respectively. The sorption was found to depend on solution pH, adsorbent dose, and temperature. The optimum pH for the removal of p-nitroaniline was found to be 7.0. The Freundlich model and Redlich-Peterson model can describe the experimental data effectively. The negative changes in free energy (delta G0) and enthalpy (delta H0) indicate that the sorption is a spontaneous and exothermic procedure. The negative values of the adsorption entropy delta S0 indicate that the mobility of p-nitroaniline on the carbon surface becomes more restricted as compared with that of those in solution.