Application Of Diatomite For Sorption Of Pb, Cu, Cd And Zn From Aqueous Solutions: Kinetic, Thermodynamic Studies And Application Of Response Surface Methodology (Rsm)

Contamination of water and soil with toxic metals is a serious environmental issue. To study the Pb, Cu, Cd, and Zn sorption behavior by diatomite, batch experiments were carried out with increasing levels of initial concentration (0-200 mg/L) under different contact times (0-360 min) and temperatures (283, 293, 303, and 313 K). The effects of concentration (0-200 mg/L), pH (3-6), and ionic strength (0.01-0.06 mol/L) on the sorption were modeled using response surface methodology (RSM). Results showed that adsorption data were well-fitted by the Langmuir equation. The sorption of metals intensified by increasing initial concentration and pH but ionic strength had inverse effect. High value for R-2 (0.99) and adjusted R-2 (0.99) showed that the removal of ions can be described by response surface method. One-way ANOVA showed (p-value < 0.0001) that quadratic model is the best model for determining the interaction of variables. The values of the sorption energy parameter from Dubinin-Radushkevich model (E < 8 kJ K-1 mol(-1)) and negative values of increment G showed that the sorption of the metals was physical and spontaneous. The positive values of enthalpy (Delta H) indicated that the sorption reaction of metals was endothermic at 283-313 K.Practitioner pointsApplications of diatomite increased the sorption of Pb, Cd, Zn, and Cu from aqueous solutions.Diatomite, as low-cost adsorbent, had significant potential to sorption of ions.The sorption of heavy metals by adsorbent intensified by increasing initial concentration and pH but ionic strength had inverse effect.High value for R-2 (0.99) and adj-R-2 (0.99) showed that removal of metals can be described by response surface method (RSM) and the initial concentration of metal was the most significant factor.