Removal of lead, cadmium, copper, and arsenic ions using biosorption: equilibrium and kinetic studies

Abstract

Biosorption of lead, cadmium, copper, and arsenic ions by using native algae was investigated. Experiments were carried out in a batch reactor to obtain equilibrium and kinetic data. Experimental parameters affecting the biosorption process such as pH, shaking time, initial metal concentrations, and temperature were studied. The optimum pH for removal was found to be 3, 5, 4, and 5 for Pb²⁺, Cd²⁺, Cu²⁺, and As³⁺, respectively. Biosorption of these metals is based on ion-exchange mechanism accompanied by release of light metals such as calcium, magnesium, potassium, and sodium. Experimental isotherms data well fitted an ion-exchange model and the affinity constant was calculated for each metal. The results showed the ion-exchange model was found suitable for describing the biosorption process. Fourier Transformation Infrared Spectroscopy analysis was used to find the effects of functional groups of algae in biosorption process. The results showed that Pb²⁺ had a greater difference in the peak values of absorbance bands than As³⁺ and Cu²⁺, while Cd²⁺ had the lowest. The experimental data showed that the kinetics of biosorption of four metals fitted well the pseudo-second-order model.

Keywords:

• Biosorption
• Algae
• Ion-exchange model
• Affinity constant
• Kinetics

Acknowledgment

We would like to express our sincere thanks and deep gratitude to the Iraq Ministry of Water Resources/Center for the Restoration of Iraqi Marshlands for supporting this work.