Reactive orange 16 dye adsorption from aqueous solutions by psyllium seed powder as a low-cost biosorbent: kinetic and equilibrium studies

Abstract The biosorption process using natural materials has found widespread applications than to their inexpensiveness, availability, and reusability. The aim of this research is to investigate the efficiency of psyllium seed powder in removal of reactive orange 16 dye. The impacts of various influential parameters such as initial pH, contact time, adsorbent dose, temperature and dye concentration were evaluated using a batch biosorption method. Data analysis was conducted by SPSS 19. The removal efficiency of reactive dye 16 using the natural adsorbent psyllium was obtained to be 94% in optimal conditions (pH 4, contact time = 40 min, and adsorbent dose = 2 g/L). Biosorption equilibrium experiments indicated that the best fit was achieved with Langmuir isotherm model. Maximum adsorption capacity was found to be 206.6 mg/g at 303 K. Kinetic analysis revealed that adsorption experimental data were best fitted by pseudo-second-order model. Free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were calculated to predict the nature of adsorption. Thermodynamic evaluation indicates that a spontaneous process has occurred. Inexpensive, locally available, and effective materials could be used for dye removal in wastewater treatment processes. Undoubtedly low-cost adsorbent benefits for commercial purposes in the future