Lysine is an essential amino acid used in many applications, including animal and human foods and pharmaceuticals. A sulfonated poly(styrene-divinylbenzene) cation-exchange resin with an 8% degree of cross-linking is used to bind lysine at pH 6 from an aqueous solution at 25°C. At this pH, lysine diffuses in the resin in monovalent cationic form.

The resin particle diameter is 600 μm.

(a) Estimate the diffusivity of lysine in water, , and the ion diffusivity of monovalent lysine cations, ,in this resin.

(b) Estimate the time required to convert the resin particle to80% monovalent lysine form if the resin starts 100% saturated in NH₄⁺ form and is immersed in a large volume of a lysine solution.

(c) Estimate the time required to convert the resin particle to 80% NH₄⁺ form if the resin starts 100% saturated in monovalent lysine in and is immersed in a large volume of a NH₄Cl solution.

(d) Repeat the calculation in

(b) and (c)

neglecting electrostatic coupling of diffusion fluxes and assuming that the effective diffusivity is a constant equal to . The ion diffusivity of NH₄⁺

in this resin has been reported to be  = 0.18 × 10-7 cm²/s.

Transcribed Image Text:

Lys,W