International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 03, March 2019, pp. 331-340. Article ID: IJMET_10_03_034
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
K. Gouru Naidu
Department of Basic Science & Humanities (BS&H), GMR Institute of Technology, Rajam532127, A.P., India
K. Venkata Krishna
Department of Chemical Engineering, GMR Institute of Technology, Rajam-532127, A.P.,
K. Koteswara Rao
Department of Basic Science & Humanities (BS&H), GMR Institute of Technology, Rajam532127, A.P., India
A series of blends consisting of Red mud(RM) varying from 1.5 to 3 g and
Graphene oxide(GO) varying from 0 to 1.5 g to give a total of 3g were prepared. They
are used as adsorbents in the treatment of waste water samples from few industries,
for effective removal of phosphates, phenols, heavy metals and dyes. The best blend
compositions for removal of Phosphates, Heavy metals & Phenols, Dyes were 2.5:0.5;
2.75:0.25; 2.1:0.9 respectively. The percentage removal of Phosphates & Nickel was
100 % while the removal of Zn varied from 58 to 68 % for the refinery samples
studied. The contact time required for 95 % removal of phenols was just 4 hrs. In the
studied dyes, Congo red showed maximum adsorption of 10 mg/g.
Key words: Red Mud, Graphene Oxide, Phosphate, Heavy metals, Phenol, Dyes
Cite this Article K. Gouru Naidu, K. Venkata Krishna and K. Koteswara Rao, Red
Mud & Graphene Oxide Blend as an Effective Coagulant And Adsorbent For the
Treatment of Waste Water From Various Industries, International Journal of
Mechanical Engineering and Technology, 10(3), 2019, pp. 331-340.
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Red Mud & Graphene Oxide Blend as an Effective Coagulant and Adsorbent For the Treatment of
Waste Water From Various Industries
The industrial wastewatersusually have lot of variation in both their flow rates and the
intensity of pollution. So, it is almost impossible to assign any fixed values to their
constituents. In general, industrial wastewaters do contain some suspended, colloidal and
dissolved (mineral and organic) solids. Apart from being either excessively acidic or alkaline
sometimes they may even contain high or low concentrations ofcolored matter, inert organic
or toxic materials and possiblypathogenic bacteria [1]. These wastes may be discharged into
the sewage system,at times, and therefore necessitate pretreat before releasing it to the
municipal system or it isnecessary to a fully treat when the wastes are discharged directly to
surface orground waters.
The most significant environmental problem and threat to public health in both rural
andurban India is inadequate access to clean drinking water and sanitation facilities [2].
Almostall the surface water sources are contaminated to some extent by organic pollutants
andbacterial contamination and make them unfit for human consumption unless
disinfected[3].The urban India has become a massive and perhaps a frightening reality as far
as wastemanagement is concerned. This country can no longer afford to allow urban
areasconstituting cities and towns of varying magnitude to take care of them; they need the
fulland undivided attention of our planners and decision makers for protection of
environment,aquatic resources and ultimately for better management of health aspects[4].
An estimated 38354 millionlitres per day (MLD) sewage is generated in major cities of
India,but the sewage treatment capacity is only of 11786 MLD. Similarly, only 60% of
industrial wastewater, mostly large scale industries, is treated[5].In developing countries like
India, the problems associated with wastewater reuse arise fromits lack of treatment. The
challenge thus is to find such low-cost, low-tech, user friendlymethods, which on one hand
avoid threatening our substantial wastewater dependentlivelihoods and on the other hand
protect degradation of our valuable natural resources. Theuse of constructed wetlands is now
being recognized as an efficient technology forwastewater treatment. Compared to the
conventional treatment systems, constructed wetlandsneed lesser material and energy, are
easily operated, have no sludge disposal problems andcan be maintained by untrained
Red Mud (RM) is a residue of the aluminium industry rejected during the alkaline
extraction of alumina from bauxite by the Bayer or sintering process [7]. Many efforts are
being made globally to find suitable uses for red mud. Some researchers focused on the
application of red mud in wastewater treatment [8].Red mud is composed of a mixture of
solid and metallic oxides. The red colour arises from iron oxides, which comprise up to 60%
of the mass of the red mud [8]. The mud is highly basic with a pH ranging from 10 to 13. In
addition to iron, the other dominant components include silica, unleached residual aluminium,
and titanium oxide.Graphite oxides(GO) demonstrate considerable variations of properties
depending on degreeof oxidation and synthesis method.Due to Graphene oxide’s large
theoretical specific surface area and hydrophobic nature it canbe utilized for the adsorption of
organic pollutants to environmental pollution cleanup [9].
The coagulants produced from Red Mud with suitable treatment were used for heavy
metal and turbidity removal from industrial wastewaters [10]. Red Mud when activated by
acid treatment and neutralization, i.e. activated Red Mud (ARM) was found to have better
sorption of Cu than ferric chloride and polyaluminum chloride (PAC) in terms of cost and
solid waste volume [11]. On the other hand, Graphene Oxide (GO) is also used either alone or
in combination with other adsorbents for waste water treatment [12]. A blend of Red Mud &
Graphene Oxide is not reported till now in the waste water treatment. So in this work, we
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K. Gouru Naidu, K. Venkata Krishna and K. Koteswara Rao
have explored the application of RM & GO composite, especially for removal of Phosphates,
Heavy metals, Phenols and Dyes in the waste waters of two oil refineries, one pharmaceutical
industry and one Fertilizer industry.
In the experimental studies, a series of Red Mud and Graphene Oxide blends were taken to
study the efficiency of them for treating the wastewater samples obtained from different
industries. Initially the Red Mud has been activated by using a standard procedure[13].
Graphene Oxide fine particles have also been prepared by using another standard
(i) Activation of Red Mud: 100gms of Red Mud was taken into a beaker for the
activation.Activation of Red Mud was carried out by treating it with H2SO4(30%wt
solid/liquid, ratio 1:5) with a contact time of 9 hrs. After partial dissolution of RM at room
temperature of 250C, the resulting suspension was centrifuged and the leftover mud was
neutralized [15]. Then by slow mixing of NaOH to the solution, a pH of 8 is reached and we
get a gel like state.
(ii) Synthesis of Graphene Oxide: GO was prepared according to the modified Hummer
method. In detail, 10g ofgraphite and 5g of NaNO3 were mixed with 216mL H2SO4 and 24mL
H3PO4 and stirredin an ice bath for 10min[16]. Next, 30g of KMnO4 was slowly added so that
thetemperature of the mixture remained below 5°C. The suspension was then reacted for 2h
inan ice bath and stirred for 60min before again stirring it in a 40°C water bath for60min. The
temperature of the mixture was adjusted to a constant 98°C for 60min whilewater was added
continuously. Deionized water was further added so that the volume of thesuspension was
800mL. 30mL of H2O2 was added after 5min. The reaction product wascentrifuged and
washed with deionized water and 5% HCl solution repeatedly[17]. Finally,the product was
dried at 80°C.
Effluentswere collected from different industries (Refinery 1, Refinery 2, Pharmaceutical
industry, Fertilizer industry) which contain organic compounds, heavy metals, anions to test
the efficiency of Red Mud (RM) and Graphene-Oxide (GO) blend at different compositions.
This blend is also used to remove colour from different dye solutions (Congo Red, Methylene
Blue, Para rosaniline and malachite green).Treatment of effluent is done by the following
(iii) Effluent treatment: 100ml of effluent was taken in three conical flasks and mixed with
the blend of RM and GO having different compositions. The mixture was shaken at 200rpm
for 1hr. Then themixture was allowed for settling for 1hr, when the sludge got settled it was
removed. Theacquired solution was used for further treatment i.e. for extraction of metals,
phenols andphosphates.75ml of the above treated solution was taken for extraction of metals,
5ml is used forphenol test and 10ml for phosphate test[18 - 20]. The above procedure was
repeated for different effluents and also for different shaking times (2& 3hrs). After treating
the samples with the blends prepared, the filterate is analyzed for (i) phosphates by
spectrophotometry (ii) heavy metals by AAS (Atomic Absorption Spectroscopy) (iii) phenol
by spectrophotometry and (iv) dyes - congo red, methyleneblue, malachite green, pararosaniline, by spectrophotometry.
The activated Red Mud, prepared as per the procedure given above, is shown in Figure 1a and
appears brown in colour. The Graphene Oxide obtained by following the modified Hummer’s
method after final processing is shown in Figure 1b and is black in colour.
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Red Mud & Graphene Oxide Blend as an Effective Coagulant and Adsorbent For the Treatment of
Waste Water From Various Industries
Figure 1a
Figure 1b
The effluents were initially tested and then treated with RM & GO blend at different
compositions and their experimental results (RM-2.5 & GO-0.5) are tabulated as below.
Table 1: Characteristics of initial effluents from different industries:
Effluent Source
Turbidity before
Colour, Odour
Refinery 1
Refinery 2
Brown, traces of
Yellowish clear
Black, pungent
Greenish, with rotten
oil droplets, heavy
liquor with high
pungent smell
phosphate content
The pH of the effluents before and after treatment with RM-GO blends remained in the
range 6-7.2 except for the Fertilizer industry effluent whose initial pH was 2.31 and reached
7.0 after treatment with RM-GO blend. This could be understood as Red-Mud is originally
known to be basic and hence neutralizes the effluent to pH 7.0. However, the turbidity of all
the effluents reduced drastically after treatment with RM-GO blend.
3.1. Removal of phosphates:
Different blends of Red Mud &Graphene Oxide were used to test the adsorption efficiency
ofphosphates from fertilizer industry effluent. According to the experimental results the
blendof RM-2.5, GO-0.5 was proved to be the best ratio of adsorbents in the adsorption of
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K. Gouru Naidu, K. Venkata Krishna and K. Koteswara Rao
Figure 2
Shiao and Akashi et al [21] first reported an investigation of phosphate removal from
aqueous solution using ARM treated with hydrochloric acid. It was found that the ARM
exhibited higher adsorption capacity than raw red mud. Theratio of acid volume to red mud
weight influenced the adsorption capacity.
Huang et al [22] conducted an investigation of phosphate adsorption using red mud from
Australia. The red mud sample was treated by different methods such as acid treatment using
HNO3 and HCl (RM-HNO3 and RM-HCl) and combination of acid and heat treatment at 700
C (RM-HNO3-700 and RM-HCl-700).
Mohanty et al. (2004) [23] used sulfuric acid to treat red mud to adsorb phosphorus from
dilute aqueous solution. Experiments were carried out in aqueous as well as buffer media to
obtain optimum conditions like contact time, pH, adsorbent dose, adsorbate concentration,
andtemperature. The pH value of 4.5 was found to be optimum for maximum removal.
3.2. Removal of heavy metals:
Different blends of Graphene Oxide and Red Mud were used to test the adsorption efficiency
ofheavy metals from refinery, pharmaceutical effluents. Zinc and Nickel metals were
analyzedwith different blends of Graphene Oxide and Red Mud. According to the
experimental resultsthe blend of composition RM-2.75&GO-0.25, showed highest
percentage removalfor Zinc from the effluents of Refinery 1 & 2 (Table 2). In the removal of
Nickel, the same blend composition could remove upto 100 % from the effluents of Refinery
1 & 2 as well as from Pharmaceutical industry effluent (Table 3).
Table 2: Removal of Zinc
Effluent Source
Refinery 1
Refinery 2
RM- 3.0
GO- 0.0
RM- 2.75
GO- 0.25
RM- 2.50
GO- 0.50
RM- 3.0
GO- 0.0
RM- 2.75
GO- 0.25
RM- 2.50
GO- 0.50
Initial conc. of
metal (ppm)
Conc. of metal after
treatment (ppm)
% Removal
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Red Mud & Graphene Oxide Blend as an Effective Coagulant and Adsorbent For the Treatment of
Waste Water From Various Industries
Table 3: Removal of Nickel
Effluent Source
Refinery 1
Refinery 2
RM- 3.0
GO- 0.0
RM- 2.75
GO- 0.25
RM- 2.50
GO- 0.50
RM- 3.0
GO- 0.0
RM- 2.75
GO- 0.25
RM- 2.50
GO- 0.50
RM- 3.0
GO- 0.0
RM- 2.75
GO- 0.25
RM- 2.50
GO- 0.50
Initial conc. of
metal (ppm)
Conc. of metal after
treatment (ppm)
% Removal
Gupta and Sharma (2002)[24] also tested an ARM in batch and column operations for
theremoval of cadmium and zinc from aqueous solutions. The red mud was treated by H2O2
andthen heat-treated at 500 0C. The removal of Cd2+ and Zn2+ was almost complete at
lowconcentrations, while it was 60–65% at higher concentrations at optimum pH values of
4.0and 5.0, respectively, with 10 g of adsorbent in an 8–10 h equilibration time.
Santona et al.[25] (2006)reported an investigation of heavy metal adsorption (such as
Pb ,Cd2+ and Zn2+) on non-treated (RMn) and acid-treated red muds[26]. The results
showedthat the RMn adsorption capacity for the three heavy metals was Zn2+> Pb2+> Cd2+,
whichagrees with other research works. Acid treatment with HCl decreased the red mud’s
capacityto adsorb the heavy metals by 30%, which is quite different from other investigations.
Zoumis et al.[27] (2000)conducted an investigation of remediation of mine waters
containingheavy metals using industrial wastes (fly ash, red mud scale arrears), natural wastes
(e.g., treebark), and relatively cheap natural products (bentonite, zeolites) as active barrier
systems. Flyash and red mud presented the best results for the removal of Zn, Cd, Ni, and Mn.
3.3. Removal of Phenol:
Different blends of Red Mud and Graphene Oxide were used to test the adsorption efficiency
of phenols from refinery effluents. Refinery1 consisting of large amount of phenol traces are
found to have phenol (about 5 ppm) beyond the standard limits of around 0.2ppm. The
contact time was varied with different blends at different time intervals and the results were
predicted. According to the experimental results, at 4 hrs contact time the RM-2.75 gm &
GO-0.25 gm blend shows the optimum adsorption rate.
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K. Gouru Naidu, K. Venkata Krishna and K. Koteswara Rao
Rui Hu [28], studied the efficient removal of phenol and aniline from aqueous solutions
using graphene oxide/polypyrrole composites.
3.4. Removal of dyes:
Red Mud and Graphene Oxide blends were used for adsorption of different dyes (Congo red,
methylene blue, malachite green, para-rosaniline) by having the contact time of 10 mins
between the blend & dye (Figure 4a). The experimental results have shown that the blends
with composition RM-2.1 & GO-0.9 have maximum adsorption rate for the above dyes
(Figure 4b).
Figure 4a
Figure 4b
In the past years, several investigations have been carried out toexplore the applicability
of red mud for dye removal from wastewater. Namasivayam and Arasi[29] first reported an
investigation using red mud for dyeadsorption in aqueous solution. They investigated Congo
red (an anionic dye) adsorptionkinetics and isotherms and found that adsorption followed the
first-order rateexpression and that the equilibrium adsorption data obeyed both the Langmuir
and Freundlich isotherms. The adsorption capacity of the red mud for the dye was 4.05 mg/g.
Theyproposed that the mechanism of adsorption was mostly ion exchange.
Arias et al. [30] performed a study of methylene blue adsorption on red mud usingboth
batch and column techniques and observed two kinetic processes: first a rapid
processfollowed by a slow kinetic reaction. The maximum adsorption was 0.74 mg/gfor a
reaction time of 192 hours.
Gupta et al. [31] studied the removal of some basic dyes, Rhodamine B, fast green, and
methylene blue, from wastewater using H2O2-activated redmud. In the batch experiments, the
removal efficiencies of Rhodamine B, fast green, andmethylene blue on this adsorbent were
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Red Mud & Graphene Oxide Blend as an Effective Coagulant and Adsorbent For the Treatment of
Waste Water From Various Industries
92.5%, 94.0%, and 75.0%, respectively. Theadsorption was found to be exothermic for the
three dyes.
Wang et al. [32] investigated the heat and acid treatments of fly ash and red mud on
atypical basic dye removal, methylene blue, from aqueous solution. It was found that fly
ashgenerally showed higher adsorption capacity than red mud. The raw redmud showed
adsorption capacity of 7.8 – 10.6 mol/g and the adsorption was increased with increasing pH.
Heat and acid treatment reduced the adsorption capacity due to thereduction of some organics
and hydroxyl groups by thermal decomposition and neutralizationof hydroxide ions on the
basic surface of red mud.
For red mud, adsorption of methylene blue was an endothermic reaction with H of 10.8
kJ/mol. Recently, Tor and Cengelog lu [33] reported a study of removing Congo red, an
anionicdye, from water by using acid-activated red mud. It was found that sufficient time to
attainequilibrium was 90 min. The Langmuir isotherm was the best-fit adsorption isotherm
modelfor the experimental data.In the above investigations, red mud has been only applied to
remove two typesof dyes, anionic and basic dyes. The results indicate that physical and
chemical treatments ofred mud will significantly influence the adsorption capacity. Acid
treatment will result inenhancement of anionic dye adsorption but decrease the basic dye
The present work has identified that Red mud(RM) & Graphene oxide(GO) and blend is a
very effective adsorbent for the treatment of waste water as compared to the earlier reports for
removal of phosphates, phenols, heavy metals, dyes. Earlier methods require long time for
removal of the parameters under study while this method could effectively remove from a
minimum of 10 min (for Dyes) to maximum 4 hrs (for Phenols). The blend of RM-GO with
2.75:0.25 composition exhibited effective removal of phenols present in the effluent samples.
With regard to dyes, the maximum adsorption of Congo red was 4.05 mg/g in earlier literature
but in this study we have obtained an adsorption rate of 10 mg/g. Heavy metals like Zn & Ni
from both the refinery samples were removed upto 68 % and 100 % respectively, by using the
optimum RM-GO blend composition of 2.75:0.25. In conclusion, this coagulant is
comparatively cost effective (as one of it is a waste material) and is used to treat effluents
from various industries.
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