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THE USE OF IRON IN PEAT WATER FOR FENTON PROCESS
Mirna Apriani, Ali Masduqi
turbidity, Fe and Mn, but only Fe that meets the requirements as clean
water (Eri, 2009).
Conventional treatment of humic acids can be done using coagulation
process (Hendricks, 2005 and Wu et al., 2011), precipitation, filtration,
ion exchange, adsorption using activated carbon and biological
treatment (Wu et al, 2011). According Karbito (1999), coagulation to
reduce the color and turbidity require high doses so it is difficult to
apply at the household scale. According to Murray and Parsons (2004),
the higher the dose of coagulant will increase the organic matter
removal but sludge production will also increase which can cause new
problems in its processing.
According to the WEF (2008), Advanced Oxidation Process (AOP) is
the oxidation process that produces reactive oxidants (such as the
hydroxyl radical). According to Parsons (200 4), AOP is one of the
water and waste water treatment technology, which utilizes an oxidant
ability to process organic matter into a more simple form and harmless.
Examples of carbon processed into carbon dioxide, hydrogen into
water, nitrogen into nitrate and others. Processing using AOP has the
ability to form strong oxidizing hydroxyl radicals which can oxidize the
organic material is faster than using ozone. Oxidizing strength can be
seen from the oxidation potential value that can be seen in Table 1.
Table 1. Oxidation potential for various oxidator
Oxidator
Oxidation potential (V)
Flourine 3.03
Hydroxyl radical 2.80
Atomic oxygen 2.42
Ozone 2.07
Hydrogen peroxide 1.78
Permanganat 1.68
Chlorine 1.36
Processing using AOP can be processing using UV-light based
applications (UV/H 2 O 2 and VUV), ozone-based applications (O 3 /H 2 O 2 ,
O 3 /UV, O 3 /H 2 O 2 /UV danO 3 /H 2 O 2 /TiO 2 ), heterogenous photocatalysis
(TiO 2 /UV ), Fenton process, catalytic oxidation, electrochemical
oxidation and oxidation ultrasound ( Matilainen and Silanpää, 2011)
Fenton process is one of the AOP which the process using hydrogen
peroxide oxidizer and a catalyst (iron salt) to produce hydroxyl radicals
(OH*) (Parson, 2004; Jiang et al, 2010). Fenton process can be run
effectively at pH 2-4. Fenton process does not use toxic materials, does
not lead to residues and is simple technology (Parson, 2004). Fenton
process consists of oxidation and coagulation that can occur in a single
process through pH adjustment. Fenton process does not use toxic
materials, does not lead to residues and simple technology (Wu et al,
2010). Fenton process is the most inexpensive and easier compared to
other process in AOP (Alaton et al, 2008). In an acidic environment,
hydrogen peroxide and ferrous ion react in the following reaction:
Fe 2+ + H 2 O 2 OH* + OH - + Fe 3+ [1]
Organic + OH* H 2 O + products [2]
According to Wu et al (2011), OH* reacts with organic material and
oxidize Fe 2+ to Fe 3+ which can serve as a coagulant after the pH
adjustment into above 6. The increasing of pH, will stop the oxidation
process and continue to coagulation process.
MATERIALS AND METHODS
Peat water taken from Simpang Arja village, Rantau Badauh District of
South Kalimantan - Indonesia. Sampling would be done at rainy season
(April 2012). Using hydrogen peroxide solution (H 2 O 2 , 30%, w/w), the
experiments were conducted in batch reactor using 1 L beaker glass.
After hydrogen peroxide solution addition, the sample were stirred
using the jar test with 50 rpm (Murray and Parsons, 2004) for 150
minutes and measured iron and organic parameters every 30 minutes.
Based on the analysis of the peat water samples characteristics is
known that pH 3.4, the organic content of 63.2 mg / L and iron at 34
mg / L. The initial pH value of sample was acid so it does not need pH
adjustment. The iron concentration was used to determine the addition
of hydrogen peroxide for each ratio H 2 O 2 /Fe 2+ variation. The optimum
condition of H 2 O 2 /Fe 2+ to remove organic and iron is 3.5 – 4.5 (Wu et
al, 2011) and 5 (Rohmatun et al, 2007).
Analytical methods for initial characteristic and oxidation process using
permanganate value test for organic parameter and for iron using
spectrophotometric iron analysis.
RESULT AND DISCUSSION
The oxidation time was tested within the time interval range of 0 – 150
min to determine whether the iron in peat water can be used for fenton
process to oxidize the organic contaminant. The experiment used 34
mg/L (0.61 mM) iron mM and the addition of 73.32 mL hydrogen
peroxide (H 2 O 2 ) 2.14 mM, ratio H 2 O 2 /Fe 2+ is 3.5 for 1000 mL peat
water. After the H 2 O 2 addition, the sample was stirred for 50 rpm.
Analysing of iron and organic started after 30 minute stirring and
continued every 30 minute. Fig 1 showed after 30 minute stirring iron
and organic concentration is decrease. The percentage of iron
decreasing are 73,42% for 30 minute ; 57,98% for 60 minute ; 70,57%
for 90 and 120 minute ; 75,21% for 150 minute. The largest decreasing
of iron is 75,21% for 150 minute. The decreasing iron value is in line
with the decrease of organic. The percentage of organic decreasing are
60% for 30 and 150 minute ; 55% for 90 and 120 minute ; 72,5% for 60
minute. The largest decreasing of iron is 150 minute however the
decreasing of organic for 150 minute is only 60% which smaller than
for 60 minute (72,59%). So the optimum time for ratio H 2 O 2 /Fe 2+ 3.5
was taken for 60 minute.
Fig.1. The measurement of Fe and organic after the H 2 O 2 addition
(Ratio H 2 O 2 /Fe 2+ = 3.5); (Fe 2+ 0.61 mM; H 2 O 2 2.14 mM)
Fig 2 showed after 30 minute stirring, iron and organic concentration is
decrease. The largest decreasing of organic to 34.76 mg/L after 120
minute stirring and iron to 9.53 mg/L after 90 minute. For ratio
H 2 O 2 /Fe 2+ is 4, the addition of H 2 O 2 2.44 mM for 1000 mL peat water
is 83.80 mL. After the H 2 O 2 addition, the sample was stirred for 50
rpm. The percentage of iron decreasing are 59,42% for 30 minute ;
64,45% for 60 minute ; 71,98% for 90 minute ; 59,8% for 120 and 150
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