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Using Rice Husks in Water Purification in Brazil
Mendonça Vian, C. E.; Silveira Neto, J.W.; Mourad, Khaldoon
Published in:International Journal of Environmental Planning and Management
Published: 2016-07-27
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Citation for published version (APA):Mendonça Vian, C. E., Silveira Neto, J. W., & Mourad, K. A. (2016). Using Rice Husks in Water Purification inBrazil. International Journal of Environmental Planning and Management, 2(3), 15-19.
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International Journal of Environmental Planning and Management
Vol. 2, No. 3, 2016, pp. 15-19
http://www.aiscience.org/journal/ijepm
ISSN: 2381-7240 (Print); ISSN: 2381-7259 (Online)
* Corresponding author
E-mail address: [email protected] (K. A. Mourad)
Using Rice Husks in Water Purification in Brazil
Camila Emanuelle Mendonça Viana1, José Wilmar da Silveira Neto1, Khaldoon A. Mourad2, *
1Environmental Management, Ateneu University, Fortaleza, Brazil
2Center for Middle Eastern Studies, Lund University, Lund, Sweden
Abstract
Rice husk, which considered a waste, has a high level of silicon. This paper investigates the use of carbonized rice husk in
water purification. The carbonization was done using a handmade carbonizer. The preparation process starts with the
production of a precursor that is rich in carbon through the pyrolysis of the rice husk in an inert atmosphere. The results show
an important contribution of the use of carbonic materials, by giving a direct evidence of the permanence of sodium ion Na+ in
activated carbon. The results also show that the utilization of carbonized rice husks in the purification of water is quick,
efficient and economically viable.
Keywords
Silicon, Carbonized, Inert Atmosphere, Precursor
Received: June 22, 2016 / Accepted: July 5, 2016 / Published online: July 27, 2016
@ 2016 The Authors. Published by American Institute of Science. This Open Access article is under the CC BY license.
http://creativecommons.org/licenses/by/4.0/
1. Introduction
Brazil is in a privileged situation in relation to water
availability; however, about 70% of the country´s fresh water
is found in the Amazon region, which is inhabited by less
than 5% of the population. The idea of abundance served for
a long time as a support for the culture of wasting available
water, the devaluing of it as a resource and putting off of the
necessary investment for the optimizing of its use. The
problems of water scarcity in Brazil fundamentally come
from the combination of the exaggerated growth of localized
demands and the degradation of water quality. This picture is
the consequence of disordered urbanization processes,
industrialization and agricultural expansion [7].
Analyzing public water supply quality is very importance.
The main indicators of water quality are segmented in its
physical, chemical and biological characteristics. These
indicators determine the level of treatment needed to be
appropriate for consumption according to national standards.
The treatment of water, meanwhile, implies the use of
chemical substances which may affect the health of the
workers. These chemicals may pass through a series of
physical and chemical changes, including the combination
with other chemical compounds, being capable of
intensifying or diminishing the toxicity for human beings and
living organisms. Therefore, analyses are needed to
determine the ideal concentration of these products such as
the analyses of pH, conductivity, total dissolved solids, color,
turbidity, and hardness are carried out.
All surface water varies in quality throughout time and rain
regime. Every method of water treatment has a limited
efficiency since each method assures a percentage of the
reduction of existing pollution. The degree of pollution may,
however, make a determined type of treatment unsatisfactory.
One of the stages of water treatment is filtration by activated
carbon, which has the capacity to selectively collect gases,
liquids or impurities in the interior of its pores, presenting,
therefore, an excellent power in clarifying, deodorizing and
purifying liquids or gases. Activated carbon is obtained
16 Camila Emanuelle Mendonça Viana et al.: Using Rice Husks in Water Purification in Brazil
through the controlled burning with a low level of oxygen of
porous materials such as wood, corn cobs, coconut husks and
rice husks, the latter the objective of our work in water
treatment. According to [3], the husk and straw from rice are
basic materials of low cost, normally considered to be
difficult in reuse due to its negative characteristics, such as
abrasiveness, resistance to degradation, the great volume
occupied, low nutritive properties and high level of ash.
Agriculture cultivation in Brazil uses controlled irrigation
systems, where the culture is carried out in systematized
floodplains. Planting starts in dry soil with irrigation, until
the start of tilling, when it definitively enters the blocks.
Cultivation may also be carried out without irrigation control
in the humid floodplains. About 40% of the total area of
cultivated areas in Brazil gives about 60% of the national
production, which is due to its high level of productivity
(around 5.5 ton/ha). The environmental question, with the
necessity of minimizing the global emissions of CO2, is a
favorable point for the use of biomass, since when this is
burned, CO2 is released into the atmosphere; however, the
plants absorb this gas during their photosynthesis.
Brazilian agricultural production has a large production of
residues, and thus the reuse of these residues is presented as a
relevant question in the Brazilian scenario. These residues
have been studied to assess their potential in water treatment
in order to lessen the environmental impact of these residues.
Rice husks are used a filtration material after carbonization.
This paper studies the utilization of carbonized rice husks
(CRHs), which are rich in fixed carbon, like activated
charcoal that has the capacity to purify water. The
purification system and be done building a carbonizer to burn
rice husks and installing a filter for the filtration system. The
carbonized rice husks possess high-energy power, since they
are composed of organic material and silica, which in its part
eliminates color and odor, and removes dissolved organic
substances. The main objective of this paper is to verify the
viability of the energetic reuse of carbonized rice husks in
water purification.
Rice husk is a biomass material formed of polymers identical
to those of wood, whose abrasive hardness is a typical
characteristic of materials with a higher quantity of lignin.
This material possesses a quantity of inorganic material,
around 15-20% of the material´s mass, where SiO2 is
responsible for around 95% of this total. Some oxides are
also present in lesser quantities than 1% of the mass, such as
Al2O3, CaO, AgO, K2O, MnO, Na2O and P2O5 [2, 11]. Black
rice husk ash (BRHA) was used as an Adsorbent for
Purification of Water Basins Polluted with Diesel Fuel [1]. It
also has been used for the Purification of Oil-polluted Sea
Water [12].
The rice husks are carbonized and used as a substrate in beds
or recipients in the germination of seeds and formation of
cuttings from higher vegetables, permitting the penetration
and exchange of air at the base of the roots; and being
sufficiently firm and dense to fix the seed or stake; it has a
dark coloration, being opaque to the light at the base of the
stake; it is light and porous , permitting good aeration and
drainage; it has a constant volume whether dry or humid; it is
free of weeds, nematodes and pathogens; it does not need
chemical treatment for sterilization, the reason being that it
has been sterilized by the carbonization. The substrate of
carbonized rice husk presents the following physical and
chemical characteristics: dry density 150g/L, capacity for
water retention of 53.9%, capacity for exchange of cations of
5.5 meq/dL, pH in water of 7.4, level of soluble salts of 0.7
g/L, 0.7% of nitrogen, 0.2% of phosphorus and 0.32%
potassium [10]. The calorific power of rice husk is
approximately 16,720 kJ/kg. The physical and chemical
properties of the carbonized rice husk vary with the increase
in temperature; for example, on raising the temperature of the
process, it becomes more friable and less hygroscopic [4].
Carbonization is a thermal decomposition which occurs at a
temperature above 500ºC and which eliminates non-carbon
species, producing a fixed and porous mass of carbon,
generally in an inert atmosphere (with the presence of
nitrogen and the absence of oxygen) [9]. Activated carbon is
that which is treated with oxygen to open thousands of tiny
pores between the carbon atoms. “The use of special
techniques of fabrication results in highly porous carbons
with areas of from 300 to 2,000 m2 of surface per gram.
These so-called active or activated carbons are widely used
to adsorb odiferous or colored substances in gases or liquids”.
In adsorption, the molecules of one substance are fixed to the
surface of another substance. The enormous surface area of
activated carbon gives it various places for bonds. When
certain chemical substances pass near to the carbon surface,
they are united to this surface and imprisoned. The activated
carbon is good in imprisoning other impurities, which have
carbon as a base (chemical organic substances), as well as
substances such as chlorine. Many other chemical substances
are not attracted by carbon (sodium, nitrates, etc.), passing
directly by it. This means that a filter of active carbon will
remove certain impurities, but ignore others. Another manner
of approaching this description is as made by [5, 6], in
quoting that the activated carbon produced is known to be a
porous material of high specific superficial area, representing
one of the most important groups of adsorbents from the
industrial point of view. This type of material possesses
attractive adsorbent qualities which have been utilized for the
purification and elimination of toxic components in the liquid
and gaseous states, as well as used in reactions of catalysis.
Due to the progressive degradation of the environment, it is
International Journal of Environmental Planning and Management Vol. 2, No. 3, 2016, pp. 15-19 17
hoped that activated carbon comes to play an important role
in the reduction of pollutants.
2. Material and Methods
Rice husks produced in the city of Russas, CE, were used in
the research. For the carbonization of the husks, a carbonizer
was created using a 3-litter tin, a drilling machine with a
4mm drill and a carbon steel tube of approximately 0.5m
length and 1.5''. Using a can opener, the edge of the tin where
the lid rests is removed, and then a hole is made in the
bottom of the tin the size of the internal diameter of the tube,
which represents the chimney. Finally, using the drilling
machine, hundreds of holes are made in the can (Figure 1).
Figure 1. Carbonizer.
The carbonizer was allocated on top of cotton waste, which is
impregnated with kerosene, and fire is lit on the same. Soon
after, 2 kilos of rice husks were dumped on the carbonizer,
covering it in a way in which no cracks remained. After about
20 minutes, the carbonization began. Afterwards, the husks
were spread out to cool and stored in plastic bags. Figure 2
shows the rice husks during and after carbonization.
Figure 2. Rice husks before and after carbonization.
In the preparation of the filter, a local filter was bought. In
the middle of the same, a piece of 0.5'' flexible hose of
approximately 12cm was placed, going near to the bottom,
substituting the original filter. Two nipples or beaks were
threaded scaled in the entrance and the exit of the filter for
the placing of the hoses (0.5'' x 1.5mm). For safety, a clamp
was placed on each hose (Figure 3).
Figure 3. The preparation of the filter.
Then the filter was filled by sand (0.7-1.3mm) and
carbonized rice husks in 1:1 proportion, where 125mL (217g)
of fine sand (0.7 to 1.3mm) were mixed with 125mL (14g) of
carbonized rice husks and placed in the filter. This quantity
was sufficient for the flexible hose or the PVC tube to be in
contact with the filtering material (around 5 to 7cm). The
“exit” hose was connected to a water tap from untreated
source (well). Figure 4 shows the filtering system in
operation.
Figure 4. Filtration system.
18 Camila Emanuelle Mendonça Viana et al.: Using Rice Husks in Water Purification in Brazil
Waters coming from the well and from the filtration were
collected and stored in PET bottles and analyzed physically
and chemically in the laboratory. The parameters were
estimated and analyzed by the following methods:
PH: electrometric method;
Conductivity: electrometric method;
Total dissolved solids: electrometric method;
Color: spectrophotometric method;
Turbidity: spectrophotometric method;
Hardness: titrimetric method.
3. Results and Discussions
According to this research, it was clearly observed that the
removal of color and odor was directly after the passing
through the filtration bed (sand + carbonized rice husks).
Figure 5 shows the differences between water quality before
and after filtration.
Figure 5. Water quality before and after filtration.
More analyses were carried out immediately after passion
through the filtering bed. Analyses include physical and
chemical parameters of the well water before and after
filtration. Table 1 presents the main water parameters that
had been analyzed.
Table 1. Physical and chemical parameters of well’s water before and after
treatment.
Parameters Unit Before
filtration
After
filtration
National
standards
pH 6.99 7.01 6.0-9.0
Conductivity uS 780 793 1000
TDS ppm 476 479 1000
Color Pt/Co > 550 13 15
Turbidity NTU 391 4 5
Hardness mg/L 82 72 500
According to the national standards, the Brazilian Ministry of
Health [8], pH level has an acceptable level of water supply
(6.0 - 9.0). The pH of water before the treatment presented a
small variation due to the fact that pH in natural waters is
near to neutrality if there is no direct contamination. The
small increase in pH after treatment is due to the removal of
fulvic and humic acids, which have an intense color and can
be found in the soil. The electric conductivity of the water
shows a small increase after the treatment. This parameter
indicates the presence of salts dissolved in the water, which is
proved by the small increase in the total dissolved salts
parameters. As shown in Table 1, there was a considerable
reduction in color and turbidity of the well’s water after
treatment. The color in the water for human supply is
generally due to the presence of colored organic material in
the soils, which is principally composed of fulvic and humic
acids. Table 1 shows that a considerable reduction of water
color from 550 to 13 Pt/Co in the water treated by the filter.
Levels below 15 Pt/Co are generally acceptable by
consumers. The turbidity of the water is due to the presence
of particulate material in suspension in the water, such as
finely divided organic and inorganic material, phytoplankton
and other microscopic organisms, passing from 391 NTU to
4 NTU. Turbidity values around 4 NTU are generally
imperceptible visually. According to the national standards,
the turbidity of 5 NTU is acceptable to consumers. However,
according To WHO, 1 NTU is recommended.
To conclude, the treated well water by the carbonized rice
husks is acceptable for drinking purposes according to national
standards, the Brazilian Ministry of Health [8], Table 1.
4. Conclusion
In this paper, a new technique for using activated carbon that
is embedded in rice husks was created and used. The created
filter has shown good results regarding water purification
process. The filter was quite successful, with the visible
reduction of color and turbidity. It may be a substitute for
industrial activated carbon. The use of this technique creates
a possibility of offering a contribution to the current
investigations on the mechanism of the use of carbonaceous
materials. Moreover, the possible use of primary materials,
which considered residuals and wastes in the agricultural
industry, possesses implications of interest as much economic
as environmental since it is already evident that its
appropriate use will benefit the sustainability and the process
of environmental conservation. Consequently, it would be a
big mistake of a noble primary material to consider it a waste
instead of a source, since it may be used in various industrial
branches such as water purification.
Acknowledgements
We really acknowledge the efforts of Sister Brigida (Lucinda
Scott) during the preparation and the translation of some
needed documents for this work.
International Journal of Environmental Planning and Management Vol. 2, No. 3, 2016, pp. 15-19 19
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