عنوان مقاله [English]
Background and Objectives: Industrial wastewater and water contaminated with chemicals are released into the environment and, as a result, contamination of the soil is adsorbed and contaminated with limited resources, will produce harmful and unhealthy products for health. One of the best way to remove organic pollutants from contaminated water is by adsorption. In this study, the phenomenon of adsorption of phenol red as a model pollutant from aqueous solutions by magnetic nanoparticles of magnetite as adsorbent has been studied.
Materials and Methods: Magnetite nanoparticles were synthesized by the sedimentation method and simultaneously reconstructed Fe+3 / Fe+2 ions with a ratio of 2 to 1 with NaOH in aqueous solution under nitrogen atmosphere and identified by IR, SEM and XRD methods. To determine the maximum phenol red absorption wavelength concentration, the UV-VIS spectrophotometer was evaluated in the wavelength range of 400 to 800 nm, with a maximum phenol-red wavelength of 431 nm. The phenol red adsorption on Fe3O4 nanoparticles was evaluated in a discontinuous medium. The parameters studied in this study included the initial values of nanoparticles (0.015, 0.01, 0.015 and 0.02 g), phenol red primary concentrations (5, 10, 20 and 30 mg/l), primary pH (1 , 4, 7, 9 and 12), contact time (5 to 40 minutes), and nano-adsorbent desorption process. Langmuir two-parameter adsorption isotherm models, Freundlich and Temkin were studied. Experimental comparisons were studied with pseudo-first kinetic models, pseudo-second-order, and inter-particle influences. The effect of temperature on the adsorption process was investigated by investigating the thermodynamic constants of the adsorption process including Gibbs free energy (ΔG0), change in entropy (ΔS0) and enthalpy change (ΔH0) at temperatures of 293, 300, 305 and 310 K.
Results: By increasing and decreasing pH from 7, the phenol red removal rate was increased. Increasing the phenol red adsorption in low and high pHs relative to neutral pH is due to the conversion of pollutant to ion, which increases the adsorption of phenol red contamination on nano-adsorbent. The adsorption takes after 30 minutes to equilibrium. The maximum adsorption capacity occurs at 30 mg/L of the contaminant in the presence of 0.01 mg/l of the adsorbent and at 20 °C and at pH= 7. Due to the process heat-up, the increase in temperature increases the amount of adsorption. It is observed that when temperature increase it could be result to the increase in the amount of adsorption. The Freundlich isotherm is in better agreement with experimental data. The pseudo-second-order model with a correlation coefficient of 0.9999 and a speed constant of 0.0202 is the best kinetic model describing the adsorption process. The values of the thermodynamic constants ΔH0 and ΔS0 are 278.89 kj / mol and 288.38 j / k.mol, respectively that indicate that the adsorption process is endothermic and an increase in ambient temperature at the solid-liquid interface during absorption. The negative ΔG0 indicates that the adsorption process is spontaneous.
Conclusion: Magnetite nano-adsorbent can be used as an appropriate adsorbent to remove phenolic contaminants from polluted aqueous solutions and industrial wastewater before releasing them in the environment.