Chemical engineering

The probability density $E(t)$ of times spent in a flowing system. The surviving fraction of a first-order decaying solute is ${\int }_0^{\infty }E(t)e^{-\lambda t}dt$; it is generally not the exponential function evaluated at the mean residence time.

The time a material element spends in a system. In ideal plug flow it equals the volume divided by volumetric flow rate; in a mixed vessel that ratio is a mean and does not guarantee the age of every discharged element.

A continuous reactor with uniform contents. At steady state for first-order radioactive decay, $a_{\mathrm{out}}/a_{\mathrm{in}}=1/(1+\lambda V/Q)$; young material can leave before the mean residence time.

An ideal flow model in which all fluid elements have the same transit time. For first-order radioactive decay the outlet-to-inlet radioactive activity concentration ratio is $e^{-\lambda \tau }$.

A chemical engineer.^[ref]

A chemical engineer.^[ref]

A chemical engineer who has worked on separation processes. He is credited as publisher of the Hyper-TVT teaching site; that role does not establish authorship of its individual chapters.

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Transfer of constituents from a solid into a contacting liquid. A measured solution inventory can underestimate total solid alteration when secondary precipitation or sorption retains released constituents.

Reversible exchange of ions between a solution and an ion-bearing solid. Selectivity, competing dissolved ions and the solid exchange capacity control contaminant removal.

A polymeric ion exchanger with fixed charged sites and mobile counterions. Exhausted resin is a secondary waste; ion exchange is not an unrestricted removal method for neutral dissolved molecules.

Transfer of a solute between immiscible liquid phases according to its relative chemical affinities. complexation and oxidation state can change the distribution; selective back-extraction is often called stripping. Extraction efficiency alone does not establish separation from a second solute.