Waste to valuable by product - utilization of carbonised decanter cake from palm oil milling plant as an effective adsorbent for heavy metal ions in aqueous solution
Palm oil milling plant generates large amount of waste that was proven to cause environmental problems. About 40 kg decanter cake was generated from each ton of fresh fruit bunch processed. Previous studies suggested agricultural waste could be employed as heavy metal ion adsorbent. Due to the si...
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| Format: | Thesis |
| Language: | English |
| Published: |
2010
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| Subjects: | |
| Online Access: | http://umpir.ump.edu.my/id/eprint/2736/ http://umpir.ump.edu.my/id/eprint/2736/1/NUGROHO_DEWAYANTO.PDF |
| Summary: | Palm oil milling plant generates large amount of waste that was proven to cause
environmental problems. About 40 kg decanter cake was generated from each ton of
fresh fruit bunch processed. Previous studies suggested agricultural waste could be
employed as heavy metal ion adsorbent. Due to the similarity of decanter cake with
other agricultural waste we proposed to explore the use of decanter cake as an adsorbent
for heavy metal ion removal.
Utilization of decanter cake as an effective adsorbent for Cd 2 , Cu2 and Pb2 ion
removal from aqueous solution has been studied. The decanter cake was first dried at
105 °C and then carbonized at various temperatures. The resulting carbonized decanter
cake were tested for removing Cd2 , Cu 7+ and Pb2 ions. Proximate analysis using
thermogravimetry analysis of decanter cake carbonized at 500 °C indicated that the
adsorbent contained 4% moisture, 21% volatile,23% fixed carbon, and 52% ash.
Adsorption test were normally carried out by mixing 1.0 g of the decanter cake in 100
mL aqueous solution of the various ions. The concentration of metal ions in the
solutions used is in the range of 100 - 1000 mg/t.
The results of adsorption studies indicated that the removal of metal ions was
highest in the case of Pb2 when the carbonization temperature was 500 °C and 600 °C
in the case of Cd2 and Cu2 . Maximum removal of the Cd2 , Cu2 and Pb2 were also
observed to take place when the pH of the solution is in the range of 4 - 5. Langmuir
and Freundlich isotherm models were used to fit the isotherm experimental data. The
maximum uptakes of Cd2 , Cu2 and Pb2 onto the carbonized decanter cake in this
study were estimated to be 24, 23, and 97 mg/g respectively. Adsorbed metal ions can
be desorbed from adsorbent using dilute HC1 solution. The adsorption kinetics was
found to follow the pseudo-second-order kinetic model. Thermodynamic parameters
such as standard enthalpy (MI"), standard entropy (AS-) and Gibbs free energy (AG-)
were determined. Adsorption process was endothermic and had negative value of Gibbs
free energy changes. The competitive adsorption characteristics of binary and ternary
heavy metal ions Cd2 , Cu2 and Pb2 on PDC500 were investigated in batch systems.
Equilibrium adsorption data showed that PDC500 displays a high selectivity toward one
metal in two-component or a three-component system with an affinity order of Pb2>
Cu2 > Cd2 Chemical activation of decanter cake using ZnC12 increased the maximum
adsorption capacity for Cd2 , Cu2 and Pb2 significantly to 52, 44, and 159 mg/g
respectively. Kinetic and thermodynamic properties of adsorption were affected by
chemical activation.
Scale up of the batch process into industrial scale was explored using the
Langmuir parameter from experimental data. A three-stage continuous counter current
adsorption unit gave the best adsorption performance for Pb2 ion removal in term of
minimum adsorbent consumption. |
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