The question is have three equations
1. dCR/dt = JS/V where dCR/dt is the change in concentration of the receiving side of the membrane. J is the flux across the membrane, S is the membrane area and V is the volume of receiving phase.
2. J = (D x change in concentration)/L. Where D is the diffusion coefficient and is the membrane thickness

3. Change in concentration in this case = CR(o)-CR(t). where CR(o) and CR(t) are the concentration in the receiving phase at t= 0 and t=t.

Combining equations 1-3 yields differential eqtn 4 if I am correct

4. Ddt =(LV/S)x dCR/(CR(o)-CR(t)

I am trying to find the answer if one integrates equation 4 of both terms.