Equilibrium and Kinetic Study of 4-Nitrophenol Removal by Modified Silk Waste

: In this research, silk waste was modified by H2SO4 and used as an adsorbent to remove of 4-nitrophenol from aqueous solutions. After preparing of adsorbent, the adsorption experiments were down in a batch system in an erlenmeyer flask under various conditions such as different initial concentrations of 4-nitrophenol (10, 20, 30, 40, 50 mg/L), pH (3, 7, 10), dosage of modified silk waste (0.5, 1, 1.5, 2, 2.5 g/50 mL), temperature (20, 30, 40 C) and contact time. Data revealed that adsorption of 4-nitrophenol onto modified silk waste was reached equilibrium at 40 min. Also, results have shown that, the removal of 4-nitrophenol decreased with increasing of pH and initial concentration of 4-nitrophenol and increased by increasing of modified silk waste dosage. Also, obtained data confirmed that the increasing of temperature has negative effect on adsorption of 4-nitrophenol onto modified silk waste. Pseudo-first-order and pseudo-second-order equations were used to determine the kinetics of adsorption process. The analysis of kinetics models showed that the pseudo-second-order adsorption mechanism is predominant. Langmuir, Freundlich and Temkin isotherm models were studied. The results indicated the adsorption of 4-nitrophenol onto modified silk waste could be well fitted with the Langmuir isotherm model.