Adsorption of Congo red dye onto activated carbon from periwinkle shell was
carried out to see if the activated carbon from Periwinkle shell will provide a good alternative
for the commercial activated carbon in the adsorption of Congo red dye from polluted water.
Periwinkle shells carbonized at 400oC and activated with 0.1M HCl at 800oC in a furnace
was used as adsorbent to remove Congo red dye from aqueous solution. The effect of the
variables: contact time, temperature and initial Congo red concentration were studied
through single-factor classical method. The contact time range, 30 – 180min, temperature
range, 30 – 55oC and concentration range, 25 – 150mg/L were used to study the adsorption
efficiency, kinetic and thermodynamic studies of the process . The results show that
equilibrium is established after 120 minutes and that the percentage adsorption is highest at
initial concentration of 25mg/L. Again, the adsorption kinetic followed pseudo-second order
reaction, having rate constant, (K2) = 0.3661 g/mg.min, correlation coefficient, (R2) = 0.9999
and adsorption capacity, (Ade) = 2.3585 mg/g. The thermodynamic parameters obtained are:
free energy (?G) =  -6.71 and -8.20 KJ/mol at 303 and 328K respectively, enthalpy (?H) =
11.52KJ/mol and entropy, (?S) = 60.04J/mol.K. The surface area of the adsorbent was
obtained as 123.42m2/g. These results show that activated carbon from periwinkle shell is a
viable low-cost adsorbent for the removal of Congo red dye from aqueous solution.