Comparison of the experimental results with the Langmuir and Freundlich models for copper removal on limestone adsorbent

The purpose of this study was to investigate the possibility of the limestone as an adsorbed media and low-cost adsorbent. Batch adsorption studies were conducted to examine the effects of the parameters such as initial metal ion concentration C-0, particle size of limestone D-L, adsorbent dosage and equilibrium concentration of heavy metal C-e on the removal of the heavy metal (Cu) from synthetic water solution by limestone. The removal efficiency is increased with the increase in the volume of limestone (influenced by the media specific area). It has been noted that the limestone with diameter of 3.75 is the most effective size for removal of copper from synthetic solution. The adsorption data were analyzed by the Langmuir and Freundlich isotherm model. The average values of the empirical constant and adsorption constant (saturation coefficient) for the Langmuir equation were a = 0.022 mg/g and b = 1.46 l/mg, respectively. The average values of the Freundlich adsorption constant and empirical coefficient were K-f = 0.010 mg/g and n = 1.58 l/mg, respectively. It was observed that the Freundlich isotherm model described the adsorption process with high coefficient of determination R-2, better than the Langmuir isotherm model and for low initial concentration of heavy metal. Also, when the values of amount of heavy metal removal from solution are predicted by the Freundlich isotherm model, it showed best fits the batch study. It is clear from the results that heavy metal (Cu) removal with the limestone adsorbent appears to be technically feasible and with high efficiency.