Pretreatment of green macroalga, caulerpa lentillifera, for heavy metal removal

Abstract

To investigate the adsorption of heavy metals (Cu, Cd, Zn and Pb) using the pretreated biosorbent derived from the biomass of marine algae, Caulerpa lentillifera. Twenty four pretreatment methods were examined based on their adsorption capacities. Only a few methods were found to have higher adsorption capacity than the untreated algae. These included: CaCO3 24 hours (29% enhancement in maximum adsorption capacity) and NaOH 1 hour (16%) for Cu, CaCO3 24 hours (78%) for Cd, and NaOH 1 hour (67%) for Pb. No improvement for Zn adsorption was found from all 24 methods. The optimal exposure time for the pretreatment by 0.5N NaOH was found with in the range of 0.5 to 1.0 hours. For the pretreatment by heating in 0.5N NaOH, the optimal heating time should be shorter than 5 minutes. The evaluation of functional group suggested that the possible functional groups for the adsorption of these heavy metals were a covalent bond with C-O, an electrostatic or ionicbond with a hydroxide (O-H), and a covalent or ionic bond with amine (N-H), amino, (N-H) and sulfonate (S-O) groups. Most of the pretreatment methods were found to decrease the quantity of potential functional groups. Appropriate pretreatment methods were those with low potential to change the appropriate functional groups