Removal of lead from aqueous solution using low cost abundantly available adsorbents

Abstract

ABSTRACT:The removal of poisonous Pb (II) from wastewater by different low-cost abundant adsorbents was investigated. Rice husks, maize cobs and sawdust, were used at different adsorbent/metal ion ratios. The influence of pH, contact time, metal concentration, adsorbent concentration on the selectivity and sensitivity of the removal process was investigated. The adsorption efficiencies were found to be pH dependent, increasing by increasing the solution pH in the range from 2.5 to 6.5. The equilibrium time was attained after 120 min and the maximum removal percentage was achieved at an adsorbent loading weight of 1.5 gm. The equilibrium adsorption capacity of adsorbents used for lead were measured and extrapolated using linear Freundlich, Langmuir and Temkin isotherms and the experimental data were found to fit the Temkin isotherm model. Low-cost adsorbents, lead, adsorption, wastewater, Isotherms Key words: MATERIALS AND METHODSRice husk and maize cobs were collected from agricultural areas and sawdust was collected from a carpenter working shop. The adsorbent materials were washed, cut into small pieces then oven dried at 80 o C for 72 h and finally were grinded to suitable size. The untreated materials were used as adsorbents in the bench-scale studies. In each experiment, a 50 mL of the metal ion solution were mixed with a definite amount of the adsorbent. The mixture of the test solution and each of the adsorbents was shaken on a reciprocating shaker at 225 rpm. At the end of each experiment, adsorbents were separated from the solution and the remaining lead concentration was analyzed using a Perkin-Elmer Optima 2000 Inductively coupled plasma (ICP-OES). The adsorption experiments were carried out at room temperature. The pH of the suspension in the experiments was adjusted with Sodium hydroxide and HCl. IR analysis of the used adsorbents was performed using FTIR-8201PC (Shimadzu). RESULTSThe main parameters influencing metal sorption were investigated: contact time, initial metal ion N. T. Abdel-Ghani, et al. T % 1/cm 68 concentration,amount of adsorbent and pH value of solution. The results were expressed as the removal efficiency (E) of the adsorbent towards metal ions or the % removal, which was defined as:Where: C o and C f are the initial and equilibrium concentration (ppm) of metal ions in solution, respectively. IR-characterization of the adsorbentsIn order to gain better insight into the surface functional groups available on the surface of the different investigated adsorbents, their IR spectra were recorded as shown in Figs. 1-3. Rice husk IR spectrum (Fig. 1) showed four intense bands, at 3379.1, 2920, 1604 and 1076.2 cm -1 . The band at 3379.1 cm -1 was attributed to the surface hydroxyl groups and chemisorbed water. The bands at 2920 and 2850.6 were assigned to C-H stretches of methylene groups on the surface and to chelated H-bridges. Bands at 1604 and 1076.2 cm -1 can be assigned to C=O stretching frequencies, and to phosphate and silicate groups, respectively. Small peaks observed at...

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