Snail shell samples were washed and carbonized at 400oC, ground,
sieved and activated with 0.1M HCl at 800oC in a furnace. The
activated carbon prepared, were used as adsorbent to remove Congo red
from aqueous solution. Factors such as contact time, temperature and
initial concentration were studied through single-factor experiment,
while other factors are kept constant (at 30min, 30oC and 50mg/L) in
each. Adsorption isotherm, kinetic and thermodynamic studies were
carried out for the corresponding experiment. The isotherm results
show that, Freundlich isotherm has the best fit for the adsorption.
Again, the adsorption kinetic followed pseudo-second order reaction
with rate constant (K2) = 0.2667 g/mg.min, correlation coefficient, (R2)
= 0.9999 and adsorption capacity, (qe) = 2.2573 mg/g. Also, the
thermodynamic parameters, enthalpy (?H) = 23.93KJ/mol, entropy
(?S) = 84.64J/mol.K and negative values of free energy (?G)  were obtained. These results show that activated carbon from snail shell is agood low-cost adsorbent for the removal of Congo red from aqueous
solution.