It is because with low
concentrations the relationship between the active sites of surface and the molecules of dye in the solution
is raised, thus all the molecules will have been retained by biosorbent and eliminated completely from the
solution. However, at high concentrations, quantity of dye adsorbed per unit of mass of biosorbent, is
more significant, which causes a saturation of support and thus a quantity of the dye remains free in the
solution that causes low yield.