Adsorption behavior of Cd ions onto pentaethylenehexamine modified activated carbon
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摘要: 以稻壳活性炭(AC)为基体,采用五乙烯六胺(PEHA)为改性剂,制备了改性AC-PEHA。研究了AC-PEHA对溶液中Cd离子的吸附动力学、等温吸附曲线、pH的影响等吸附行为,考察了不同HCl浓度对解吸率的影响,并通过SEM、FTIR、BET比表面积等手段,对AC和AC-PEHA吸附剂进行了表征。结果表明:AC-PEHA对Cd离子的吸附在反应时间为60 min处达到平衡,符合准二级吸附动力学模型。在初始Cd离子浓度为10~350 mgL-1,pH值为5.0的条件下,AC-PEHA对Cd离子的吸附量达53.58 mgg-1,显著高于AC的吸附量26.15 mgg-1。初始pH值为6~8的条件下,碱性环境更有利于AC-PEHA对Cd离子的吸附。采用30 gL-1的HCl时AC-PEHA对Cd离子的解吸率为83.8%。改性后,由于PEHA进入AC孔道,虽然使其孔容和孔径分别降低了21.6%和7.4%,但同时使AC表面负载了伯胺N—H吸附基团,提高了AC-PEHA对Cd离子的吸附能力。Abstract: In order to develop an effective adsorbent for Cd ions removal, activated carbon (AC) was prepared with rice husk and modified with pentaethylenehexamine (PEHA). The batch adsorption were studied for AC and AC-PEHA to determine the effect of contact time, initial Cd ions concentration and solution pH on the Cd ions ions uptake. The effect of HCl concentration on desorption efficiency for Cd ions was discussed as well. SEM, FTIR and BET surface area analysis were used to characterize the structure, morphology and properties of AC and AC-PEHA. The results show that the adsorption equilibrium are achieved for both AC and AC-PEHA at react time 60 min, and adsorption kinetics are well described by the pseudo-second-order model. Comparing with AC, The adsorption capacities of AC-PEHA for Cd ions increase from 26.15 mgg-1 to 53.58 mgg-1 at initial Cd ions concentration of 10-350 mgL-1 and pH of 5.0. The adsorption of Cd ions on AC-PEHA is more favourable under alkaline condition (pH=6-8). The maximum Cd ions desorption of 83.8% for AC-PEHA occurs with 30 gL-1 HCl. Although the total pore volume and average pore width of AC decrease by 21.6% and 7.4% respectively after PEHA modification, the modification add more primary amine groups to AC pores, and it significantly enhances the Cd ions adsorption capacity of AC.
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Key words:
- Cd ions /
- activated carbon /
- pentaethylenehexamine /
- adsorption /
- desorption
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