In this work, Taguchi L16 experimental design was applied to optimize biosorption of hydrazine by Sargassum ilicifolium in a batch system. Biosorption tests were performed with four factors concentration, pH, biosorbent dosage and agitation time at four different levels. Optimal experimental conditions were determined by calculated signal-to-noise ratios. The best conditions for biosorption of hydrazine were determined by the Taguchi method and desirability approach as initial hydrazine concentration of 135 mg/L, pH = 7.5, biosorbent dose of 0.1 g/L and time 90 min. Furthermore, thermodynamic, isotherm and kinetic studies were performed to explain the biosorption mechanism. The kinetic of hydrazine removal followed the pseudo-second-order model. A nonlinear regression was applied to fit the experimental data with several isotherm models. The Redlich-Peterson and Radke–Prausnitz isotherms showed the best concordance as equilibrium models. Nature of possible interactions between the functional groups of S. ilicifolium and hydrazine was confirmed by FT-IR spectra of raw and hydrazin-loaded alga.
