(108c) Insight Into the Application of Advanced Oxidative Method for Biosorbent Modification In Water Treatment Application

INSIGHT INTO THE APPLICATION OF ADVANCED
OXIDATIVE METHOD FOR BIOSORBENT MODIFICATION IN WATER TREATMENT APPLICATION

Ofomaja, A.E., Naidoo E.B., and DLADLA,
T.V.

Department of Chemistry, Vaal University
of Technology, X021, VanderbiljPark, 1900 South Africa.

INTRODUCTION

Adsorption using waste/dead
plant materials as adsorbent is receiving much attention in recent times due to
its low value, natural abundance in nature, ability to remove pollutants at low
concentrations e.t.c. Numerous research have been conducted to ascertain the
potentials and applicability of water and wastewater treatment to eliminate
pollutants such as heavy metals, colored compounds such as dyes, and organic
pollutants. The results have indicated the promising ability for these
materials to be applied as filters to replace or compliment several other
expensive and advanced technologies.

Plant materials are usually
made up cellulose, hemi-cellulose, lignin extractives, lipids, water, proteins,
simple sugars, hydrocarbons, and starch along with other organic components
(Ofomaja 2009). In their use as adsorbents, some plants materials are found to
cause discoloration of the treated wastewater leading to increased chemical
oxygen demand (COD), biological oxygen demand (BOD) and total organic carbon (TOC)
levels (Gaballah et al., 1997). Several methods have been applied in the activation
of these biomaterials to prevent leaching of colored organic pigments, some of
which are treatment with base solutions (sodium hydroxide, calcium hydroxide,
sodium carbonate) mineral and organic acid solutions (hydrochloric acid, nitric
acid, sulfuric acid), have been reported in literature.

Oxidative methods have been
applied in the removal of organic pollutants from aqueous solution and soils
with success, these methods include; Wet oxidation and Catalytic wet oxidation
(Deepak et al., 2002), Ozone based oxidation (Bila et
al., 2005), Electrochemical oxidation (Deng and Englehardt, 2007) and Fenton's
oxidation (San
Sebastian et al., 2003). These advanced
oxidative method as there are called are effective due to the role of a highly
reactive radical intermediate such as hydroxyl radical (?OH) as an oxidant. With
an oxidation potential (E⁰ ) of 2.80 mV, the ?OH radical can
rapidly degrade recalcitrant organics such as aromatic, chlorinated, and
phenolic compounds (Parsons and Williams, 2004). Once a reaction of the free radical is initiated by ozone or H₂O₂,
a series of oxidation reactions occurs in the solution and the radicals rapidly
react with most of the target compounds.

In this report the Fenton
oxidation is applied as a method for extracting organic colored components from
Pine cone powder in its application as adsorbent for lead(II)
from water.

METHODS:

Pine cone was collected from
local plantation in South Africa, washed crushed and sieved to size below 90 μm.
Fenton reagent was prepared at different ratios of Fe²⁺/H₂O₂
at room temperature and initial pH of 2.5. The effect of time and solid/liquid
ratio was also determined at optimum Fe²⁺/H₂O₂.

The reaction steps involved as
well as the optimum conditions for extraction with Fenton's reagent were
monitored by the oxidation/reduction potential (ORP) of the mixture, the
consumption of hydrogen ions (Δ pH) during reaction, acid value, surface
charge, and surface functional groups.   

RESULTS:

The results for the varying of Fe²⁺/H₂O₂
were conducted in two separate experiments. In the first experiment, Fe²⁺
concentration was fixed at 500 mg/L, while H₂O₂
concentration varied between 1000 to 140,000 mg/L. While in the second
experiment, H₂O₂ concentration was fixed at 100,000 mg/L
and Fe²⁺ concentration varied between 50 and 5000 mg/L. Figure 1
shows the results of both experiments.  

Fig. 1: Effect of varying (a)
H₂O₂ on a fixed amount of Fe²⁺and (b)Fe²⁺
at fixed H₂O₂.

The results reveal that both
Change in hydrogen ion consumption and ORP values changed as the Fe²⁺/H₂O₂ ratio changes reaching a maximum at
similar point in the plots. This point was found to correspond with acid number
determined the maximum value for surface charge and bulk density. The Fourier transform
infrared (FTIR) spectra of the samples at different Fe²⁺/H₂O₂ ratios revealed that the no new
chemical groups were formed, but an increase along with a slight shift in peaks
at 3342.65 and 1607.57 cm^-1 were observed. These observations along
with the Scanning electron microscope (SEM) analysis suggest that the
structural integrity of the samples were maintained after treatment. The
reduction in bulk density of the activated samples and the sharp drop in COD of
the treated water as compared to the raw pine cone indicates that extraction of
large amounts of the organics causing discoloration have been achieved. Finally,
higher lead(II) removal was achieved with the activated pine cone as compared
with the raw sample.  

DISCUSSION
& CONCLUSIONS:

Argun et al. (2008) showed that the ORP values of were consistent with
activation of pine cone. This study has also shown that both the ORP values and
the consumption of hydrogen ions during the formation of the hydroxyl radical
followed that same trend and can used to follow the activation process.

     (1)

According to Argun et al. (2008), increase in porosity of the activated
pine cones lead to increase in adsorption capacity. But in our study, it is
suggested that Fenton activation did not only destroy the organic and
increasing porosity, but oxidized the material producing additional acidic functional
groups as was observed from the increasing values of acid number and the functional
group determination. Varying the Fe²⁺/H₂O₂
increased these parameters to a maximum values at Fe²⁺/H₂O₂
= 0.01, and after this value these parameters were found to decrease.
Therefore, maximum lead(II) removal was due to increased acid functional groups
on the pine cone surface rather than increased porosity.     

REFERENCES:

Argun, M.E., Dursun, S., Karatas, M., Gürü, M. Activation of pine cone
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Deepak,  B.A., Suresh K.B.,
Irfan S., Jaidev P.
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for organic pollutant removal from paper and pulp industrial waste liquor . Applied Catalysis A:  236(2002)
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Gaballah,
I., Goy, D., Allain, E., Kilbertus, G., Thauront, J. Recovery of copper through
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Ofomaja
A.E. Removal of transition metals from
industrial wastewater using natural biosorbents. Doctoral Thesis submitted to
Vaal University of Technology (2009).

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in Advanced Oxidation Processes for Water and Wastewater Treatment, S. A.
Parsons, Ed., pp. 1?6, IWA Publishing, London, UK, 2004.

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Sebastian, N., Fernandez, J.F., Segura, X.F., Ferrer, A.S., Pre-oxidation of an
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