Simulation And Characterization Study Of Water Adsorption Behavior In The Confined Nanospaces

In recent years,adsorption and purification technology has been widely used to solve environmental problems such as air and water pollution.At present,there are many kinds of adsorbents available,among which carbon nanotubes have attracted extensive attention due to their high specific surface area and excellent physical and chemical properties.Water adsorption on carbon materials is common and related research is rich.And the research on water adsorption behavior in carbon materials has important theoretical guiding significance for chemical industry,environment,materials and other fields.In this work,the Grand Canonical Monte Carlo(GCMC)method is used to simulate the cylindrical pore-water adsorption system.The effects of pore length,pore size and adsorption temperature on the water adsorption behavior in single-walled carbon nanotube(SWCNT)and the adsorption behavior of water molecules in cylindrical pore with different surface strengths were systematically studied,via the characterization of isotherms,local density distribution and isosteric heat.For the Water-SWCNT system,the results show that: the water molecule packing manners are in the arrangement form of single chain,double helix chain and water clusters due to the pore size effects.When the pore length is in the range of 4-8 nm,the initial adsorption pressure increases as the pore length,but this effect rule gradually disappeared with increasing pore length to 10 nm.With the increase of adsorption temperature,the phase transition pressure of capillary condensation of water molecules in SWCNT increases gradually,while the saturated adsorption capacity of water molecules in tubular pores decreases gradually.In addition,the hysteresis of water absorption/desorption increases with the increase of adsorption temperature(273 K-323 K).The study of surface strength on water adsorption shows that: the initial pressure of water adsorption decreases with surface strength;and when surface strengths are 20,28,32 K,the capillary evaporation phase transitions completed instantaneously.While the surface strength increases to 40 K,the capillary evaporation phase transition is shown gradually desorbed steps.As surface strengths increased from 20 K to 40 K,the isosteric adsorption heat at the pressure points of capillary condensation phase transition is 127.47,117.98,84.04,59.16 kJ/mol,respectively.