Abstract:

Biochar (BC) obtained from durian shell carbonization was mixed with silicium-calcium slag particles as adsorbent carrier material. The mixture of BC and silicium-calcium slag particles was impregnated with pentaethylenehexamine (PEHA) liquid and then mixed with wet flue gas desulfurized gypsum (FGDG) slags to prepare wet amine functionalized CO₂ solid adsorbents, which significantly improved adsorption activity than FGDG-free adsorbents. The adsorbents were characterized by FT-IR, TGA, SEM and N₂ adsorption-desorption. Effect of FGDG slag content, adsorption temperature and CO₂ concentration in flue gas on adsorption performance were studied in a fixed bed reactor. The results showed that moisture presence in FGDG slags changed reaction mechanisms between amino groups and CO₂. Adsorbent with 30% FGDG had a maximum adsorption capacity of 2.33 mmol/g at temperature of 85℃ and its adsorption capacity decreased slightly by only 4.2% after 12 cycles of regeneration and reuse, showing a favorable adsorption stability. The isosteric heat of CO₂ adsorption calculated with Clausius-Clapeyron equation was found between heats of physical and chemical adsorption, suggesting simultaneous occurrence of physical and chemical interactions in adsorption process. Fitting experimental data with kinetic models showed that pseudo-first-order and pseudo-second-order models did not fit accurately but Avrami model fitted well, which further indicated that CO₂ adsorption process on BC/SCS-PEHA-30%FGDG is not a simple physical or chemical adsorption process, but a combination of these two adsorption processes.

Key words: biochar, pentaethylenehexamine, adsorption, stability, kinetics model

摘要：

将榴莲壳碳化制备生物炭（BC），与硅钙渣混合作复合载体，在其表面浸渍负载五乙烯六胺（PEHA），并加入含水分的脱硫石膏（FGDG），得到胺功能化的含水CO₂固体吸附剂，与不含脱硫石膏的吸附剂相比吸附活性明显改善。通过FT-IR、TGA、SEM及N₂吸脱附等手段对吸附剂进行了表征，并在固定床反应器中考察了吸附剂脱硫石膏含量、吸附温度和CO₂浓度对吸附性能的影响。结果表明，脱硫石膏中水的存在改变了氨基与CO₂的相互作用机理。当脱硫石膏含量为30%、吸附温度为85℃时，CO₂最大吸附量为2.33 mmol/g。经12次循环再生后吸附量仅下降了4.2%，表现出良好的吸附稳定性。Clausius-Clapeyron方程计算的等量吸附热介于物理与化学吸附热之间，说明吸附过程中物理与化学作用同时进行。用多个动力学模型对实验数据进行拟合，pseudo-first-order与pseudo-second-order模型均不能准确拟合实验数据，而Avrami模型可较好地拟合整个吸附过程，进一步验证BC/SCS-PEHA-30% FGDG的CO₂吸附过程并非单纯的物理或化学吸附，而是两者同时发生。

关键词: 生物炭, 五乙烯六胺, 吸附, 稳定性, 动力学模型