Question

Indicate whether you will need to adopt a kinetic or equilibrium approach for determining the mass balance in the following cases:

i) To determine the adsorption of an organic compound from water to activated carbon.

ii) To determine the concentration of a pollutant in a room due to continuous emission in indoor air.

iii) To determine the dissolution of oxygen in an aquatic system.

iv) To determine the phosphorus balance in a lake.

Answer 1

Kinetic method: it depends on data that changes with time such as concentration

Equilibrium approach: It depends on data that is obtained after the system reaches equilirbrium and there is no change with time

i) Equilibrium approach: The equilibrium data gives the amount of adsorbate, optimum operation conditions to operate the system such temperature, pressure, retention time in the column and so on

ii) Kinetic approach: SInce there is continuous emissions outside, there is continuous change of concentration of pollutant in room. This is a process which is unsteady and hence requires kinetic approach

iii) Equilibrium approach: The amount of dissolved oxygen in aquatic system depends on the maximum solubility or equilibrium conditions of the system. It changes with the composition of other components in the system

iv) Kinetic approach: Since this requires balance ie (mass of P in - mass of P out) = accumulation where accumulation of P depends on the time spent by P in the lake, it is kinetic approach