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Adsorption of Pb Ions onto Natural and Modified Egyptian Rice Husk: Kinetic and Isotherm Equilibrium Studies

El-Shafey OI, Ammar NS, El-Shafey SE and El-Nabarawy TA

Getting rid of Pb(II) from wastewater by several low-cost abundant adsorbents was studied. The natural rice husk (RH), that modified with oxalic acid (RH-H+) and sodium hydroxide (RH-OH-), were used at various adsorbent/metal ion ratios. The impact of pH, contact time, adsorbent dose and initial Pb(II) concentration parameters were studied. The results showed that equilibrium time was obtained at 60 min. Three kinetic models were applied to the kinetic adsorption data; pseudo-first order model, pseudo-second order and intraparticle diffusion models. The obtained data are resembled the pseudo-second order kinetic as shown by their correlation coefficient, 0.998, 0.995 and 0.998 for RH, RH-H+ and RH-OH- respectively. The equilibrium adsorption data obey Langmuir and Freundlich isotherm models with maximum adsorption capacities of 10.78 mg/g, 12.5 mg/g and 51.54 mg/g for RH, RH-H+ and RH-OH- respectively. From the Dubinin-Radushkevich (D-R) isotherm model, the value of sorption energy obtained shows that the mechanism of reaction is physical adsorption. The surface adsorption process is verified as a surface phenomenon by performing X-ray diffraction (XRD) analysis.