Benzoic Compounds Removal from Aqueous Solutions by Acidic Silk: Equilibrium and Kinetic Study

Background Aims of the Study: p-Chloronitrobenzene is a benzoic compound that widely used in many chemical industrials. p-Chloronitrobenzene may be absorbed through the skin and is suspected to causing cancer. So, developing an easy method to remove of it from the environment is necessary. Equilibrium isotherms and adsorption kinetics of p-Chloronitrobenzene onto modified silk waste were studied experimentally. Materials and Methods: Silk waste was modified by HCl and used as an adsorbent to remove of p-Chloronitrobenzene from aqueous solutions. After preparing of adsorbent, the adsorption experiments were down in a batch system in an erlen mayer at different concentrations of p-Chloronitrobenzene (20, 40, 60, 80, 100 mg/L), pH (2, 4, 6), dosage of modified silk waste (1, 2, 3, 4, 5 g/250 mL), temperature (20, 30, 40 °C) and contact time. Results: Data revealed that the adsorption of p-Chloronitrobenzene on to modified silk waste was reached equilibrium after 20 min. The adsorption of p-Chloronitrobenzene decreased with the increasing of pH and the concentration of p-Chloronitrobenzene which is increased by increasing of modified silk waste dosage. Also, data confirmed that changing of temperature did not have significant p-Chloronitrobenzene removal efficiency. Pseudo-first-order and pseudo-second-order equations were used to determine the kinetics of removal process. It was found that the adsorption of p-Chloronitrobenzene onto modified silk waste was obeyed from pseudo-second-order kinetic model. Conclusion: The results indicated the adsorption of p-Chloronitrobenzene onto modified silk waste could be well fitted with the Freundlich isotherm and pseudo-second-order kinetic models.