Removal of heavy metals from wastewater by adsorption on coir pith activated carbon

The activated carbon prepared from coconut coir pith by potassium hydroxide activation was found to exhibit remarkable adsorption capacity for cadmium, copper, and zinc. Batch equilibrium tests showed that the extent of metal removal was found to be dependent on initial concentration, contact time, pH, and carbon dose. It was found that at pH values below 3, the adsorption of metal ions was very less and was effective above pH 6. The metal ion sorption was found to follow the Freundlich model. The kinetics of adsorption of metal ions followed 1st order. The agglomerated coir pith carbon was evaluated for the effect of flow rate and bed depth in column experiments. Linear relationships between bed depth and service time were obtained for all the metal ions by performing bed-depth service time (BDST) analysis. The adsorbed metal ions could be quantitatively recovered by using 1.0 M HCl, and the capacity of carbon remained unaffected when put to repeated use for the removal of metal ions from aqueous solutions. The efficiency of carbon when applied to industrial effluents was found to be superior in removal of metal ions compared with the commercial ones.