Study On Dynamic Characteristics Of Dry Water Solidifying Gases

Dry Water?DW?,a kind of free-flowing powder,contains a lot of water with high dispersion degree by mixing water,hydrophobic silica particles,and air at high speeds.DW is actually a water-in-air emulsion,more correctly an inverse foam.In DW,water droplets are surrounded by hydrophobic silica particles.The network of silica particles prevents water droplets coalescence,and enhances the dispersion of water.As a result,the DW system possesses very high specific surface area.According to the structure,properties,and potential application of DW,this work focuses on preparation technology of DW consisting of different hydrophobic silica particles?GW100,D10,R202?.The microscopic morphologies of DW with different components are observed by optical microscope.The result showsthat the sizecomparison of hydrophobic silica particles is GW100<D10<R202.The optimum proportion of hydrophobic silica and deionized water is 5.5:94.5?mass ratio?,and the appropriate mixing time is about 90 s.The size distribution of DW is related to thehydrophobic properties of silica particles.The DW with smaller silica particles has higher transparent degree under microscope.Furthermore,the kinetics properties of DW solidifying carbon dioxide gas are investigated.A temperature gradient from 293 K to 273 K is designed for exploring the effect of temperature on DW solidifying carbon dioxide gas.The largest adsorption amount appears at about 278 K.At the optimal temperature,CO₂ uptake kinetics of DW with nanometer and micrometer silica shells are measured respectively,and both uptake rate and capacity show obvious size dependence of silica shell.The DW with micro-shell possesses larger uptake capacity,whereas the DW with nano-shell has faster uptake rate.By combining soluble NH₃ uptake kinetics with high and low initial pressures,the micrometer shell is identified to enhance the stability and the dispersion degree of DW,and the nanometer shell offers a shorter path for guest transiting into water core.Further,molecular dynamics simulation is introduced for illustrating size effect of silica shell on the initial step of gas uptake.It is found that the concentration of gas molecules close to the silica layers?region I?is higher than that in the bulk water region?region II?.With the increase of the size of silica spheres,the amount of CO₂ in the region I decreases,and the gas uptake is easier to reach steady state.Finally,sodium dodecyl sulfate?SDS?,alpha cyclodextrin??-CD?,and betacyclodextrin??-CD?are added into water core respectively for improving adsorption ability of DW.SDS is found to accelerate the adsorption rate but cannot enlarge adsorption capacity of DW.So SDS is considered as a catalyst or not adsorbent.Different from SDS,?-CD improves obviously adsorption capacity of DW,and the optimum adding amount is related to guest gas.For CO₂ and CH₄,the optimum values of added ?-CD are 6 g and 12 g in 100 g DW respectively.However,?-CD shows inhibiting effect on adsorption of DW.