Could someone be so kind and show be how equation (3) in integrated step by step to give (4) (please enlarge attached picture). I am stumped. Also equally frustrating is the fact that I cant even follow the step between (4) to give (5). I would love to hear back from someone to enlighten me.
Thanks very much in advance,
PS. important i think: Xr(t) represents the concentration of species (X) on resin (r) (physical adsorption beads) which are thrown into a solution at t=0. therefore I know that Xr(t) should be 0 at time equals 0. Hope this helps too.