Biosorption of Cu2+ by Eichhornia crassipes: Physicochemical characterization, biosorption modeling and mechanism

This work presents the biosorption potential Eichhornia crassipes biomass, collected from the Nile water, for removing Cu(II) ions. Physicochemical characteristics, proton and Cu2+ binding constants, and biosorption isotherms were studied. The biomass contains 43.3 mg g−1 protein, 40.76 mg g−1 carbohydrates and 16 types of amino acids. The biomass has large surface area (4.16 m2 g−1) and pore size (35.93 Å). Proton bindings (pKH1 = 1.8; pKH2 = 1.9; pKH3 = 2.0) and Cu2+ binding constants (pKM1 = 4.37; pKM2 = 4.24; pKM3 = 3.76) were calculated by Non-Ideal Competitive Absorption (NICA) model. FT-IR results suggested that OH, COOH and PO sites are mainly responsible for Cu2+ biosorption. Biosorption isotherms were successfully fitted by two Langmuir linearization models. The biosorption mechanism includes ionization and complexation stages. The biomass shows a breakthrough ability for Cu2+ biosorption (qmax = 27.7 mg g−1) and at pH 4.5.