Uranium sorption by native and nitrilotriacetate-modified Bangia atropurpurea biomass: kinetics and thermodynamics
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In this study, the red alga Bangia atropurpurea was modified with nitrilotriacetate (NTA) ligand and used for removal of U(VI) ions from aqueous solution using native form as a control system. The modification of B. atropurpurea biomass was realized by sequential treatment of algal biomass with glutaraldehyde and NTA ligand. Influence of U(VI) sorption parameters, such as contact time, adsorbent amount, medium pH and ionic strength, initial U(VI) ions concentration, and temperature on the removal performance of both algal biomasses were studied from aqueous solution. The hydroxyl, amino, carbonyl, and carboxyl groups were the main adsorptive groups of the biomasses as observed in FTIR data, and these groups can bind to U(VI) ions via electrostatic interactions. More than 78% of total sorption took place within 40 min, and equilibrium was established about 60 min. Maximum sorption capacities of the native and NTA-modified algal biomasses were found to be 190.2 and 328.8 mg g(-1), respectively, at pH 5.5 and at 30 A degrees C. The presence of other ionic species slightly decreased the U(VI) sorption capacity except that in Fe(III) ions. The sorption processes of U(VI) on the algal biomasses were described by the Langmuir and Temkin isotherms and pseudo-second-order kinetic models. The thermodynamic parameters, such as Delta HA degrees, Delta SA degrees, and Delta GA degrees, show that the process is exothermic and spontaneous. It should be stated that the NTA-modified algal biomass has a high potential for the removal of U(VI) ions from aqueous solution.