Operating conditions, contradictory effects

The available transport models are not reliable enough for porous material with a complex pore structure and broad pore size distribution. As a result the values of the model par ameters may depend on the operating conditions. Many authors believe that the value of the effective diffusivity D, as determined in a Wicke-Kallenbach steady-state experiment, need not be equal to the value which characterizes the diffusive flux under reaction conditions. It is generally assumed that transient experiments provide more relevant data. One of the arguments is that dead-end pores, which do not influence steady state transport but which contribute under reaction conditions, are accounted for in dynamic experiments. Experimental data confirming or rejecting this opinion are scarce and contradictory [2]. Nevertheless, transient experiments provide important supplementary information and they are definitely required for bidisperse porous material where diffusion in micro- and macropores is described separately with different effective diffusivities. 

Due to inaccurate and contradictory results, care should be exercised when applying the existing minimum transport models to the design or optimisation of dilute-phase systems. Some test data should be used to confirm optimal operating conditions and any deposition effects. 

There are some contradictory results among the experiments conducted by different researchers, which may be attributed to the differences in the starting materials, working conditions, and post-processing treatments for purification and stabilization [7]. The mean size of nanopaiticles depends on various operating factors simultaneously. In the following subsections, the effects of various operating conditions on PNP size will be discussed. 

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