A comparison of microstructure and adsorption characteristics of activated carbons by CO2 and H3PO4 activation from date palm pits
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摘要: 由于具有很大的吸附容量，多孔炭材料是优良的吸附剂。笔者试图比较海枣核分别经CO2活化和磷酸活化所制活性炭的结构和吸附性能。活化过程和工艺条件对炭的物理化学性质影响较大，根据文献报道的结果选取了优化的工艺参数。基于氮气吸附等温线、SEM、FT-IR等分析结果，评估了活性炭的结构特征，吸附性能则由亚甲蓝吸附值表示。CO2活化得到了微孔活性炭，产率为44%、BET比表面积是666 m2 · g-1；磷酸活化得到了产率为14.8%的中孔活性炭，BET比表面积为725 m2 · g-1。CO2活化活性炭的平均孔径是 1.51 nm，磷酸活化活性炭的则为2.91 nm。活性炭的亚甲蓝吸附等温线分别用Langmuir等温线和Freundlich等温线进行了验证，在优化工艺条件下制备的CO2活化炭和磷酸活化炭的亚甲蓝w单分子吸附容量分别为110 mg · g-1和345 mg · g-1。然而，磷酸活化产生的亚甲蓝吸附值最高达455 mg · g-1。
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关键词:
- 活性炭 /
- 物理活化 /
- 化学活化 /
- Langmuir等温线 /
- Freundlich等温线
Abstract: This work attempts to compare the texture and the adsorption capacity of porous carbons prepared from date palm pits using CO2 and H3PO4 activation. The activation conditions were chosen based on the optimized parameters reported in the literature. The microstructure of the activated carbons was assessed based on nitrogen adsorption, SEM, and FT-IR, while the adsorption capacity was estimated using methylene blue (MB) adsorption. CO2 activation resulted in a microporous carbon with a yield of 44% and a BET surface area of 666 m2 · g-1, H3PO4 activation resulted in a mesoporous carbon with a yield of 14.8% and a BET surface area of 725 m2 · g-1. The average pore diameter of the activated carbons was estimated to be 1.51 and 2.91 nm for CO2 and H3PO4 activation respectively. The equilibrium adsorption isotherms for MB were fitted by the Langmuir and Freundlich models. The monolayer adsorption capacity of CO2 and H3PO4 activated carbons for MB from the Langmuir model were 110 and 345 mg · g-1 respectively under the optimized conditions. A highest MB adsorption capacity of 455 mg · g-1 was found for the H3PO4 activated carbon with a highest BET surface area.-
Key words:
- Activated carbon /
- Physical activation /
- Chemical activation /
- Langmuir isotherm /
- Freundlich isotherm
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