Ultrasound-Assisted Biosorption Process For The Removal Of Lead And Iron On Landfill Leachate Using Pre-Treated Oil Palm Biomass
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Date
2015-02
Authors
HAFTKHANY, SHABNAM KHOSRAVI
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Abstract
Four oil palm-based biomasses which were oil palm frond (OPF), oil palm bark (OPB), oil palm leave (OPL) and empty fruit bunch (EFB) were examined in batch mode for removal of Pb (II) and Fe (III) from 3 different aqueous solutions (2 single metal solution and bimetal). The experiments were done in certain ranges of variables: pH (2-12), biosorbent size (200 μm-1400 μm), dosage (0.25 g/L-1.75 g/L) and contact time (5 min-80 min). Oil palm bark (OPB) showed the highest adsorption efficiency of 80 % and 78 % for lead and iron in bimetal solution, respectively, and 79 % for lead solution and 77 % for iron solution, because OPB had the higher surface area and pore volume in compare with other biosorbents. The Langmuir isotherm showed the best result for both metals in bimetal solution between the three biosorption isotherms investigated. The best fitted biosorption kinetic is pseudo-second-order model. The following experiments were done using OPF, because it is the more available agricultural waste compared to OPB. It was pretreated using NaCl and Na2SO4 with three different ratios, to form four different kinds of pretreated biosorbents with four different codes. The OPF pretreated in 1.0 molar NaCl was coded as CM1 and the OPF pretreated in 1.0 molar Na2SO4 was coded as SM1. The OPF pretreated in 0.5 molar with ratio 1:1 was coded SCM0.5 and combination of SM1 and CM1 with ratio 1:1 was coded SMCM1. SM1 biosorbent was found to be the best biosorbent for the removal of lead ions. The biosorption process occurred through ion exchange mechanism between lead ions and sodium ions that were present in the modified OPF. CM1 biosorbent was more
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selective to Fe (III) than Pb (II) and it was due to the present of chloride ions on its surface. Under optimum conditions (biosorbent dosage 1.25 g/L and contact time 20 min), SCM0.5 showed the highest adsorption efficiency of 98% and 92% for Pb (II) and Fe (III), respectively. The adsorption equilibrium data were fitted to three adsorption isotherm models for SCM0.5 and SMCM1. Langmuir isotherm showed the best result for ferric ions while Freundlich isotherm showed the best result for lead ions. The kinetics of the biosorption process was analyzed based on pseudo-first-order and pseudo-second-order models. The pseudo-second-order models showed a better fit for both metals. Ultrasonic-assisted biosorption process using the most suitable biosorbent (SCM0.5) was investigated on landfill leachate. Ultrasonic assisted biosorption process showed significant improvements for removal of Pb (II) and Fe (III) from landfill leachate comparing to conventional mixing method. Under optimum conditions (pH 5-6, biosorbent dosage 1.75 g/L and contact time 20 min), the biosorption of lead and iron using ultrasound increased from 78 % to 95 % and 62 % to 83 %, respectively comparing with conventional method. Ultrasonic-assisted biosorption process reached the highest heavy metal removal within 20 min comparing to 60 min for conventional method. The kinetics was also analyzed using pseudo-first-order and pseudo-second-order models and the latter model also showed a better fit for both metals. By employing response surface methodology in ultrasound assisted biosorption process, the optimum conditions were obtained at 6.07 for pH, 1.6 mg/L for biosorbent dosage, 16.30 min for the reaction time and 52.4 % of ultrasonic amplitude to give the best Pb and Fe removals of 94.1 % and 82.6 %, respectively.
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Ultrasound-Assisted Biosorption Process For The Removal Of Lead And Iron On Landfill Leachate , Using Pre-Treated Oil Palm Biomass