Adsorption isotherms and kinetic studies for the defluoridation from aqueous solution using eco-friendly raw marine green algae, Ulva lactuca.

The defluoridation from aquatic medium by raw marine algae, Ulva lactuca, was investigated. The element components and adsorbent's properties were determined. The influence of pH, contact period, and Ulva sp. weight on the deflouridation was achieved. The complete defluoridation of 10 mg F-/l solution was obtained within 10 min at definite pHs. Fourteen adsorption isotherms and four kinetic models (pseudo-first order and pseudo-second order, Elovich, and intraparticle diffusivity) were studied. The most adequate model was performed by using five error functions. The application of chi-squared test indicated that the nonlinear isotherm models (two and three parameters) were more applicable than the linear ones. The adsorption kinetic proceeded by pseudo-first-order model. The adsorption mechanism was very complex; thus, the solute distribution step was not the only dominant one during the process. The adsorption seemed to be a physical negative binding cooperative type with activation energy and free energy of 3.16 and - 1.672 kJ/mol, respectively. Thus, raw marine algae, Ulva lactuca, can be used as an adsorbent in solving the fluoridation problem in aquatic mediums throughout the world due to their fast procedure, high efficiency, low effort, and high economic value.