Abstract:

Composite adsorbent MWCNT/MgCl₂ was prepared by grinding multi-walled carbon nanotubes (MWCNT) and anhydrous magnesium chloride (MgCl₂) with mass fraction of 30%, 40% and 50% respectively. Digital scanning electron microscope (SEM) was used to observe the structure appearance of the composite adsorbent. The thermal conductivity of the composite adsorbent was measured by Hot Disk thermal constant analyzer. Representative temperature and humidity were selected by constant temperature and humidity box to test the water vapor adsorption performance of the composite adsorbent under different working conditions. The pseudo-second order kinetic model was used to fit the experimental data under the condition of 25℃, 50% RH. And the isothermal and hygroscopic curves of three samples were tested by Autosorb-IQ automatic gas analyzer under 25℃. The experimental results show that, under the same temperature and humidity conditions, the adsorption capacity of the composite adsorbent improved with the increase of MgCl₂ mass ratios. The adsorption capacity of the composite adsorbent M1, M2 and M3 with the MgCl₂ content of 30%, 40% and 50% under the condition of 25℃ and 50% RH is 0.62, 0.79 and 0.94 g/g respectively. When the constant humidity is 50% RH and the temperature changes from 15℃ to 35℃, the adsorption capacity of the composite adsorbent is affected by the dual effects of temperature and saturated water vapor pressure, which first increases and then decreases. When the temperature was fixed at 25℃ and the relative humidity increased from 50% RH to 80% RH, the adsorption capacity of the composite adsorbent greatly increased. Also, the composite adsorbent showed good adsorption ability at low temperature and low humidity of 35℃, 25% RH. When the relative pressure P/P₀ was 0.3, the adsorption capacity of M1, M2 and M3 was 0.24, 0.25 and 0.30 g/g, respectively. With the increase of the adsorption relative pressure, the moisture adsorption capacity of the composite adsorbent also improved, reaching 3.54, 3.75 and 4.42 g/g, respectively. The preparation study of the composite adsorbent MWCNT/MgCl₂ provides a basis for the study of the properties of the adsorbent, and has potential significance for the study of solar absorption air water intake.

Key words: composite adsorbent, multi-walled carbon nanotubes, magnesium chloride, water vapor, adsorption performance

摘要：

通过研磨将多壁碳纳米管分别与质量分数为30%、40%和50%的无水氯化镁复合，制备了3种不同配比的复合吸附剂MWCNT/MgCl₂。采用数字化扫描电子显微镜（SEM）观察复合吸附剂表面材质的结构样貌，通过Hot Disk热常数分析仪测得复合吸附剂的热导率，使用恒温恒湿箱选取具有代表性的温湿度，测试复合吸附剂在不同工况下的水蒸气吸附性能，并采用准二级动力学模型对25℃、50% RH工况下的实验数据进行拟合，应用Autosorb-IQ全自动气体分析仪测试了三种样品在25℃下的等温吸湿曲线。实验结果表明，相同温湿度工况下，随着氯化镁含量增加，复合吸附剂的吸附量提高，25℃、50% RH下氯化镁含量为30%、40%和50%的复合吸附剂M1、M2和M3的吸附量分别为0.62、0.79和0.94 g/g；恒定湿度为50% RH，温度变化为15~35℃时，复合吸附剂吸附量受温度和饱和水蒸气分压力的双重影响，表现为先增加后减小；温度固定为25℃，相对湿度从50% RH增加到80% RH时，复合吸附剂吸附量均大大提升；复合吸附剂在35℃、25% RH中高温、低湿条件下仍表现出较好的吸附能力；在相对压力P/P₀为0.3时，M1、M2和M3的吸附量分别为0.24、0.25和0.30 g/g，随着吸附压力的增加，复合吸附剂的吸附量也不断提升，最大吸附量分别达到3.54、3.75和4.42 g/g。复合吸附剂MWCNT/MgCl₂的制备研究，为吸附剂的性能研究提供了基础，对太阳能吸附式空气取水的研究具有潜在意义。

关键词: 复合吸附剂, 多壁碳纳米管, 氯化镁, 水蒸气, 吸附性能