New magnetic/Biosilica/Sodium Alginate Composites for removal of Pb (II) ions from aqueous solutions: Kinetic and isotherm studies

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Lead is one of the heavy metals that have harmful effects on the human health and environment. In this study, a new magnetic/biosilica/sodium alginate adsorbent (MBSA) made by the coprecipitation method was used to remove lead from aqueous solutions. It was an experimental study conducted at laboratory scale. The properties of MBSA were analyzed by scanning electron microscope (SEM), XRD, and FTIR analyses. The influences of various parameters such as contact time (0–80 min), pH (3–11), initial lead concentration (10–80 mg/L), temperature (298–318 oK), and adsorbent dosage (0.5–4 g/L) on the sorption process were investigated. The equilibrium isotherm and kinetic models were used to evaluate the fitness of the experimental data. The results showed that lead removal using MBSA was obtained at an optimum pH of 11, contact time of 80 minutes, adsorbent dosage of 4 g/L, lead concentration of 10 mg/L (46.29 g/g), and temperature of 318 oK. Investigating the isotherm and kinetic equations showed that the experimental data of the lead adsorption process correlate with the Langmuir model (R2 = 973) and intraparticle diffusion kinetic model, respectively. The values of the thermodynamic parameters (ΔΗ°, ΔG°, ΔS°) indicated that the sorption of Pb (II) ions on MBSA was spontaneous and endothermic in nature. Due to the good removal efficiency, low cost of the process, and lack of production of harmful substances for the environment, this adsorbent can be used to remove lead from the industrial wastewater.