Biosorption Kinetics and Isotherm Studies of Cd(II) by Dried Enteromorpha compressa Macroalgae Cells from Aqueous Solutions

For the first time ever, Enteromorpha compressa macroalgae (ECM), which is commonly found in Turkey, has been used as biosorbent by us. This study aims to investigate the biosorption of Cd²⁺ from aqueous solutions in a batch system by using an alga of ECM in different concentrations, pH levels, agitation rates (90–150 rpm), and contact periods. The maximum biosorption capacity of the ECM was found to be 9.50 mg/g at pH 6, Cd²⁺ initial concentration of 10 mg/L and agitation rate 150 rpm. Cadmium removal efficiency was about 95%. The experimental isotherm data were analyzed using the Langmuir and Freundlich equations. Isotherm parameters for both equations were determined and discussed. The stated biosorption mechanism is explained by the Freundlich isotherm (r² = 0.998) theory. Two simplified kinetic models including a pseudo‐first‐ and second‐order equation were selected to follow the biosorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the biosorption of cadmium onto ECM could be described by the pseudo‐second‐order equation (r² > 0.99).