Biosorption efficacy of alginate-immobilized live and metal chloride-activated Azolla microphylla in Pb(II) removal from aqueous solution

Pb(II) biosorption of untreated (CA-UT), and treated or metal chloride-activated (CA-T) Azolla microphylla microencapsulated with calcium alginate were investigated for contact time, pH, and temperature in the present study. Pb(II) biosorption rate was recorded highest within the first hour at pH 4.5-5.0. Albeit, no significant difference at 25±2oC, and 40oC. The biosorption kinetics were further described by pseudo-first- and second-order and multi-linear intraparticle diffusion graphs. Results showed that R2 values was recorded at 0.4619 – 0.9912 in the pseudo-first-order model, while in the pseudo-second-order model, R2 values was recorded at 0.9936 – 1.000. These kinetic models indicated the biosorption process of Pb(II) is a complex mechanism and influenced by various factors predominantly the pH and time of exposure. Maximum lead removal efficiency for metal uptake was recorded at 2 mg of Pb(II) per gram of biosorbent at pH 4.5 – 5.0 at 25±2oC, and 40oC. The Pb(II) biosorption efficiency was generally increased from CA-UT < CA < CA-T. This study demonstrated the applicability and effectiveness of A. microphylla in lead abatement, which could be a potential approach in phytoremediation for sewage treatment plant.