Metal Components (Fe, Al, and Ti) Recovery from …...International Journal of Emerging Technology...

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 2, February 2015)

25

Metal Components (Fe, Al, and Ti) Recovery from Red Mud by

Sulfuric Acid Leaching Assisted with Ultrasonic Waves Ki-hyuk Lim

1, Byung-hyun Shon

2

1,2Department Of Environmental Engineering, Hanseo University, Seosan-si, South Korea

Abstract—Nowadays the red mud generated from Bayer

alumina production process seriously threats the environment

and human safety. Therefore, reduction and recycling of red

mud is an urgent topic in aluminum industry. In this study,

the effects of various parameters, ultrasound power, reaction

temperature, leaching time, acid concentration, and solid to

liquid ratio on the leaching of Fe, Al, and Ti from red mud

have been investigated. The major parameters influencing

metal recovery efficiency from red mud were ultrasound

power, acid concentration, and reaction temperature. It was

found that the proper conditions for recovery of the metal

components present in the red mud are ultrasound power of

150W, sulfuric acid concentration of 6N, reaction temperature

of 70℃, solid to liquid ratio of 2%, and reaction time of 2

hours, etc. The characterization of the raw red mud, as well as

that of the leached residues was carried out by XRD, SEM-

EDX. The contents of Fe, Al, and Ti dissolved in the acid

leachate were analyzed with an ICP.

Keywords - Leaching, Metal, Red mud, Sulfuric acid,

Titanium, Ultrasonic waves.

I. INTRODUCTION

The red mud is sludge with high content of iron oxide as

a by-product generated during a process of extracting

aluminum hydroxide (Al2O3․xH2O) from bauxite. About

1.6~2.0 tons of red mud are generated by producing 1 ton

of alumina, so about 120 million tons of red mud are

generated annually in the whole world and about 200

thousand tons of red mud are generated annually in Korea.

Up to now, the accumulation amount of red mud in the

whole world is estimated to be about 2.7 billion tons, and is

expected to exceed about 3 billion tons in 2015 due to the

continuous development of the alumina industry [1]. The

red mud is composed of 14~21 kinds of mineral materials

such as 6 kinds of main components (Fe2O3, Al2O3, TiO2,

SiO2, Na2O, and CaO) and other trace elements. The red

mud is mostly treated via landfilling and ocean dumping,

but landfill can cause contamination to the soil and

underground water due to rainfalls and the dried red mud

can be scattered by winds to cause damage to the

surroundings [2].

So there have been researched various recycling

methods such as development of inorganic coagulants,

utilization for industrial waste water treatment, production

of bricks, and production of soil improving agents, etc.

using red mud, but the ratio of recycling is very low

compared to the generation amount [3]. Of the red mud

recycling methods, a research for extracting titanium, iron,

and aluminum components using an acidic solution and an

alkaline solution has been conducted a lot [4]. It should be

possible to recover many metals simultaneously from a

single process so that the process of recovering metallic

components may have economic feasibility. In addition,

more than 40% are iron components in the red mud, so iron

should be included in the recovered metallic components to

be efficient. However, the metal recovery technologies

developed so far are mostly the technologies to recover a

single component, and the trial to recovery 2 or more

metallic components simultaneously is recently under

active way, but it has a disadvantage of consuming much

cost and energy. The processes to recover titanium (Ti)

components include a thermo/electro-chemical process and

a hydrometallurgical process in general. The leaching

method using an acidic solution is mainly used to recover

the Ti component existing in the red mud, and is a method

of obtaining TiO2 finally by extracting the Ti component

eluted in an acidic solution using a selective solvent and

then sintering it [5]. The method of recovering iron (Fe)

components through a smelting process at a high

temperature reduction condition is the most researched

method. The easiest way to recover the Fe component is a

separation using a magnetic property, but the types of iron

existing in the red mud are mostly the hematite (α-Fe2O3)

and goethite (α-FeOOH) with a very weak magnetic

property, and there is a very small amount of magnetite

(Fe3O4) with a strong magnetic property. Therefore, a

process of converting it into a type of magnetite or element

iron with a strong magnetic property during a pre-treatment

process is necessary [6, 7]. In general, the aluminum (Al)

existing in the red mud was recovered in a sodium

aluminate hydrate (Na2O․Al2O3․5H2O) crystal form by

leaching a NaOH aqueous solution and then evaporating

the leachate.



26

However, recently a method of recovering Al by

leaching the red mud with water after going through a

sintering process in a reduction condition of high

temperature (800~1,000℃) is used.

The ultrasonic waves are used to promote a chemical

reaction in the sonochemistry field. Irradiating ultrasonic

waves on a liquid generate a fine airwave via cavitation to

affect the crushing, dispersion, emulsification, and

activation of reaction, etc. [8]. The ultrasonic waves

reaching the surface of a solid can cause fine cracks to

increase the diffusion coefficient of the substance. In

addition, a fine powder type of substance is also made by

crushing solid substances, so it is reported that the chemical

reactivity is enhanced by the ultrasonic waves due to an

increase in the surface area because of this effect [9].

So this study conducted an experimental research on

various variables to improve the recovery efficiency of

metallic components from red mud. This study aimed to

derive an optimal leaching condition by experimenting on

the effect of the strength of ultrasonic waves, the

concentration of sulfuric acid solutions, the temperature of

reactions, the time of leaching, and the ratio of solid to

liquid, etc. on the recovery of metallic components from

red mud.

II. EXPERIMENT

A. Characteristics of Red Mud

The red mud generated from aluminium Production

Company of Korea was used as received. Table 1 shows

the chemical compositions of red mud used in this study as

well as that of some other studies. As can be seen from the

Table 1, iron oxide, aluminium oxide, and titanium oxide

are the major constituents of the red mud, which has the

following compositions: Fe2O3 of 42.52 wt.%, Al2O3 of

18.34 wt.%, TiO2 of 7.05 wt.%, SiO2 of 6.04 wt.%, CaO of

9.13wt.%, Na2O of 7.07 wt.%, and loss on ignition of 9.55

wt.%. According to the XRD diagram (Fig. 1), the red mud

contains mainly hematite (Fe2O3), diaspore (AlO(OH)),

gibbsite (Al(OH)3), calcite (CaCO3), quartz (SiO2), anatase

(TiO2), and goethite (FeOOH). Fig. 2 shows the SEM

micrographs of the raw red mud used in this study. The

particles of the raw red mud were roughly crystallized and

the hematite was detected in the form of aggregates [10].

Table 1

Typical chemical compositions of red mud

Ref. & oxides This

study [10] [11] [12] [13]

Fe2O3 42.52 41.30 37.32 32.52 11.59

Al2O3 18.34 21.20 17.27 18.42 24.96

TiO2 7.05 7.10 4.81 6.75 6.12

SiO2 6.04 5.35 17.10 8.34 24.65

CaO 9.13 11.02 4.54 16.74 1.32

MgO - 0.25 0.40 - -

K2O - 0.15 0.29 - -

Na2O 7.07 2.15 7.13 3.59 17.67

Cr2O3 - 0.31 - - -

SO3 - 0.65 0.18 - -

LOI 9.55 10.50 10.22 - -

2¥È

10 20 30 40 50 60 70 80 90

Inte

nsi

ty

0

50

100

150

200

250

300A : Hematite (Fe

2O

3)

B : Geothite (FeO(OH))

C : Bohmite (AlO(OH))

D : Gibbsite (Al(OH)3)

E : Quartz (SiO2)

F : Anatase, Rutile (TiO2)

G : Calcite (CaCO3)

H : Sodalite (Na4Al

3Si

3O

12Cl)

I : Cancrinite

J : Diaspore (AlO(OH))

I

C

E

F

E

D

F

CB

J

GD

F

C

A

D

B

A

F

F

A

H

A

A

A

A

A

A

B

C J

Fig. 1. XRD diagrams of the raw red mud.

Fig. 2. SEM micrographs of the raw red mud.

B. Experimental Apparatus and Method

The experimental apparatus used for this study is largely

composed of a leaching reactor, an ultrasonic wave

generator with a temperature controller, an auxiliary heater,

and an agitator (Fig. 3).



27

A 1 liter quartz reactor was used to mix the sulfuric acid

and the red mud uniformly, and ultrasonic waves were

irradiated by using an ultrasonic wave generator of 0-150

W and 60 Hz with a temperature controller. In addition, the

temperature was able to be kept constant during the

experiment by using a digital heating device with a

temperature controller (DH-K5232, ± 0.1℃). The agitator

(MS-3040D, 0-3000 rpm) was coated with Teflon to

prevent corrosion due to the sulfuric acid solution, and the

stirring speed was kept constant as much as the red mud

particles may not precipitate and mix in the acid solution

during all the experiments.

For the proper reaction between the sulfuric acid

solution and the red mud, the red mud which contains

35~45% of moisture was dried for 24 hours and crushed,

and the uniform particle size was used for the experiment.

In this study, the experiment variables are the strength of

ultrasonic waves, the concentration of sulfuric acid, the

temperature of reaction, the time of leaching, and the ratio

of solid to liquid. The experiment conditions are shown in

Table 2.

Experimental procedure is as follows: the red mud and

sulfuric acid solution were loaded into the quartz reactor at

the desired mass ratio. At the end of the leaching

experiments, filtration was conducted using a vacuum

pump. When the filtration was complete, 20 ml of filtrate

was sampled and the contents of Fe, Al, and Ti dissolved in

the filtrate was analyzed with an ICP. Also the resulting

leached residues of red mud was washed, dried, and

weighed. The mineralogical analysis of the raw red mud

and the red mud leached residues was carried out using a

Siemens D5000 diffractometer. The morphology of sample

was examined by scanning electron microscopy (SEM)

using a Jeol 6380LV scanning electron microscope.

① Quartz reactor, ② Ultrasonic waves generator, ③ Heater, ④ Stirrer

Fig. 3. Experimental apparatus.

Table 2

Experimental conditions

Parameters Range

Ultrasonic waves (W) 0, 50, 150

Sulfuric acid concentration (N) 2, 4, 6

Reaction temperature (℃) 30, 60, 70, 80

Leaching time (hours) 1, 2, 4

Solid to liquid ratio (%) 2, 4

III. RESULTS AND DISCUSSIONS

A. Power of Ultrasonic Waves

The Fig. 4 shows the recovery efficiencies of 3 metal

elements (Fe, Al, and Ti) from the red mud at different

power of ultrasonic waves that is 0, 50, and 150W. The

other parameters are held constant at H2SO4 concentration

of 6N, reaction temperature of 70℃, leaching time of 2

hours, solid to liquid ratio of 2%. And all the experiments

were performed three times and the average value was

used.

As shown in Fig. 4, the average recovery efficiencies

(ARE) of Fe, Al, and Ti when ultrasonic waves are not

irradiated were 27.55%, 57.02%, and 73.54%, respectively.

However, the ARE of Fe, Al, and Ti when ultrasonic waves

of 50W and 150W are irradiated were 30.26% and 48.22%,

60.44% and 72.94%, and 76.33% and 88.95%,

respectively, to show that all the recovery efficiencies of 3

metallic components increased. The increasing rates of the

ARE for Fe, Al, and Ti depending on the increase in the

strength of ultrasonic waves from 0W to 50W were 0.0540

%point/W, 0.0684 %point/W, and 0.0558 %point/W, and

the increasing rates of the ARE for Fe, Al, and Ti due to the

increase in the strength of ultrasonic waves from 50W to

150W were 0.1796 %point/W, 0.1250 %point/W, and

0.1262 %point/W, respectively. Eventually, it shows that

the strength of ultrasonic waves should be at least 50W

because the increasing rates of the recovery efficiencies per

unit ultrasound power are far larger in 50W~150W than in

0W~50W.



28

Ultrasonic waves(W)

0 50 100 150

Reco

very

eff

icie

ncy

(%)

0

20

40

60

80

100

Iron

Aluminum

Titanium

Slope : 0.0540 %p/W

Slope : 0.0684 %p/W

Slope : 0.0558 %p/W

Slope : 0.1796 %p/W

Slope : 0.1250 %p/W

Slope : 0.1262 %p/W

Fig. 4. Effects of strength of ultrasonic waves on the recovery

efficiencies of three metallic element.

In the solid–fluid reaction systems such as the

hydrometallurgical processes, the shrinking core model was

used to determine the reaction rate [14, 15]. According to

their findings, the leaching process is controlled by the rate

of diffusion through the product layer much better than the

chemical reaction controlled. Therefore metal ions

movement from the surface of red mud into liquid phase is

limited by solid–liquid phase diffusion transfer, due to the

resistance of product layer and the insoluble impurities. An

ultrasound power can contribute to the reduction of

external mass transfer resistance through the product layer.

It is thought that this is because irradiating ultrasonic waves

can generate a cavitation phenomenon to crush the particles

of red mud more finely and can generate bubbles in the

sulfuric acid solution to increase the contact efficiency

between the sulfuric acid solution and the red mud to

increase the leaching of metallic components [14, 16].

The Fig. 5 shows the XRD diagram of raw red mud and

filtered sludge after the experiment. It shows that the

crystal phases in the filtered sludge disappeared a lot

because a lot of metals are leached in the sulfuric acid

solution no matter whether ultrasonic waves are irradiated

or not. In particular, it is judged that the gibbsite and

hematite components are easily eluted in the sulfuric acid

solution. The Fig. 6 shows the SEM photograph of red mud

sludge depending on whether ultrasonic waves are

irradiated or not. It shows that the surface of the red mud

filtered sludge on which ultrasonic waves are irradiated is

relatively more rough and smaller in particle sizes than the

surface of the filtered sludge on which ultrasonic waves are

not irradiated. It is judged that this is because irradiating

ultrasonic waves crushes the particle size of red mud more

finely due to a cavitation phenomenon [10, 16].

Inte

nsity

0

100

200

300

Inte

nsity

0

100

200

300

400

500

600

700

800

900

1000

2 Theta

10 20 30 40 50 60 70 80 90

Inte

nsity

0

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400

I

II II

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F

A : Hematite, B : Geothite, C : BohmiteD : Gibbsite, E : Quartz, F : AnataseG : Calcite, H : Sodalite, I : CancriniteJ : Diaspore

(a)

(b)

(c)

A

A

AA

A

A A

AA

C J

A

E

Fig. 5. X-ray diffraction patterns of red mud samples obtained in (a)

raw red mud, (b) ultrasonic waves are not irradiated, and (c)

ultrasonic waves of 100W are irradiated.

(a) (b)

Fig. 6. SEM micrographs of the red mud leached residue obtained in

(a) ultrasonic waves are not irradiated, and (b) ultrasonic waves are

irradiated

B. Concentration of Acid Solution

The recovery efficiency of metal elements (Fe, Al, and

Ti) in the red mud at different H2SO4 concentrations of 2,

4, and 6N are shown in Fig. 7. The other parameters are

held constant at ultrasound power of 150W, reaction

temperature of 70℃, leaching time of 2 hours, solid to

liquid ratio of 2%. And all the experiments were performed

three times and the average value was used.

As can be seen from the Fig. 7, when leaching the red

mud by using a 2N sulfuric acid solution while irradiating

ultrasonic waves of 150W, the average recovery

efficiencies of Fe, Al, and Ti were 17.33%, 61.05%, and

35.19%, respectively. In addition, as a result of leaching the

red mud by using a 4N and 6N sulfuric acid solution

respectively, the ARE for Fe, Al, and Ti were 25.73% and

48.21%, 67.66% and 72.98%, and 60.25% and 91.91%, so

the recovery efficiencies of three metallic components

increased in proportion to the increase in the concentration

of acidic solutions.



29

H2SO

4 concentration (N)

2 3 4 5 6

Re

cove

ry e

ffic

ien

cy(%

)

0

20

40

60

80

100

Iron

Aluminum

Titanium

Slope : 4.2 %p/N

Slope : 11.24 %p/NSlope : 1

2.53 %p/N

Slope : 15.83 %

p/N

Slope : 3.31 %p/N

Slope : 2.66 %p/N

Fig. 7. Effects of sulfuric acid concentrations on the recovery

efficiencies of three metallic element.

The increasing rates of the ARE for Fe, Al, and Ti when

the concentration of sulfuric acid solutions increased from

2N to 4N were 4.20 %point/N, 3.31 %point/N, and 12.53

%point/N, and the increasing rates of the ARE for of Fe,

Al, and Ti when the concentration of sulfuric acid solutions

increased from 4N to 6N were 11.24 %point/N, 2.66

%point/N, and 15.83 %point/N, respectively. As the

concentration of acidic solutions increased, all the recovery

efficiencies of three metallic components increased.

However, it can be seen that the increasing rate of the

recovery efficiencies of Al is not large even though the

concentration of sulfuric acid solutions increases, but the

increasing rates of the recovery efficiencies of Fe and Ti

increase very much as the concentration of sulfuric acid

solutions increases, so the concentration of sulfuric acid

solutions needs to be controlled depending on the kinds of

metals desired to be recovered. In addition, as the

concentration of sulfuric acid solutions increases, the

generation of acidic vapors increases and the corrosion of

devices happens, so it is judged that about 4N~6N

concentration of acidic solution is suitable like the results

by other researchers [9, 17].

The Fig. 8 shows the result of XRD analysis to investigate

the mineral facies existing in the red mud filtered sludge

depending on the sulfuric acid concentration. As shown from

the Fig. 8, a lot of hematite components were eluted and

removed, and the geothite, gibbsite, and diaspore components

were also eluted to reduce the crystal phases a lot. The Fig. 9

shows the SEM photographs to see the surface of the red mud

filtered sludge depending on the changes in sulfuric acid

concentrations. As can be seen in Fig. 9, the surface of red

mud using a 4N and 6N sulfuric acid solution is more rough

and the particles of fine sizes are concentrated more than the

surface of the sludge experimented with a 2N sulfuric acid

solution.

It is judged that the heavy metals can be efficiently

recovered due to an increase in elution of metallic components

on the surface as the concentration of sulfuric acids becomes

stronger due to this.

Inte

nsity

0

100

200

300

Inte

nsity

0

200

400

600

800

Inte

nsity

0

100

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2 Theta

10 20 30 40 50 60 70 80 90

Inte

nsity

0

100

200

300

400

I

II II

I I

I

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I

II

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C

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C

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CC

C

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E

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F

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F

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FF

D

D

D

B

B

B

B

B

B

B

B

H

H

H

G

A

H

H

H

H

AF

F

I


(a)

(b)

(c)

(d)

I

D

A

A

A

AA

A

A

A

A

A

A

A

A

A

A

A

E

C


raw red mud, (b) 2N H2SO4, (c) 4N H2SO4, (d) 6N H2SO4.

(a) (b)

(c )

Fig. 9. SEM micrographs of the red mud filtered sludge obtained in

(a) 2N H2SO4, (b) 4N H2SO4, and (c) 6N H2SO4.

C. Reaction Temperature

In order to see the recovery efficiencies of three metallic

components depending on the reaction temperatures, an

experiment was conducted while changing the temperature

between 30oC~80

oC.



30

The reaction temperatures used for extraction of metallic

components from the red mud were mostly around 60oC

[18], but this study aimed to check the difference in

recovery efficiencies at a temperature above 60oC. The Fig.

10 shows the changes in the average recovery efficiencies

of Fe, Al, and Ti depending on the reaction temperature. As

a result of experiments, the increasing rates of the ARE for

Fe, Al, and Ti when the temperature changed between 30oC

and 60oC were 0.843 %point/

oC, 0.590 %point/

oC, and

0.403 %point/oC, and those of Fe, Al, and Ti when the

temperature changed between 60oC and 70

oC were 0.821

%point/oC, 0.898 %point/

oC, and 0.841 %point/

oC,

respectively. In addition, those of Fe, Al, and Ti when the

temperature increased between 70oC and 80

oC were 0.412

%point/oC, 0.259 %point/

oC, and 0.043 %point/

oC,

respectively.

Reaction temperature(oC)

30 40 50 60 70 80

Reco

very

eff

icie

ncy

(%)

0

20

40

60

80

100

Slope : 0.843 %p/o C

Slope : 0.590 %p/oC

Slope : 0.403 %p/oC

Slope :

0.821 %p/o C

Slope :

0.898 %p/o C

Slope :

0.841 %p/o C

Iron

Alunimun

Titanium

Slope :

0.043 %p/oC

Slope :

0.259 %p/oC

Slope :

0.412 %p/oC

Fig. 10. Effects of reaction temperature on the recovery efficiencies of

three metallic element.

For three metallic components, there is a little difference

in the increasing rates of ARE depending on the

temperature increase, but they showed a similar trend. The

increasing rate of the recovery efficiency of Fe when the

temperature changed between 30oC and 70

oC increased

almost linearly, but the increasing rates of the recovery

efficiencies of Al and Ti were larger in 60oC~70

oC than in

30oC~60

oC. All the increasing rates of the AREs of three

metallic components in 70oC~80

oC slowed down a lot and

the generation of sulfuric acid vapors increased as the

temperature increased. Therefore, it is judged that about

reaction temperature of 70oC at the experiment condition in

this study will be suitable because the problems of

corrosion and safety in the device should be considered.

The Fig. 11 shows the XRD diagram of the filtered

sludge depending on the temperature changes. It is judged

that the hematite and diaspore are more easily eluted than

other components even at a low temperature. The Fig. 12

shows the SEM photograph of the surface of the filtered

sludge depending on the temperature changes.

The surface of the filtered sludge experimented at a 30oC

is relatively smooth and shows less pores, which is

considered to be because a small amount of metal

components have been eluted. On the other hand, the

surface of the filtered sludge at a 70oC and 80

oC condition

is very rough and shows relatively large pores, which is

judged to be because experimenting it at a high temperature

can reduce the attractive force between particles to elute a

lot of heavy metals via an reaction between the red mud

particles and the sulfuric acid.

Inte

nsity

0

100

200

300

Inte

nsity

0

100

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400

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nsity

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2 Theta

10 20 30 40 50 60 70 80 90

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nsity

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B

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H

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G

G

G

A

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AF

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(a)

(b)

(c)

(d)

A

A

A

A

AA

AA

A A

AA

A

A

A

A

A

A

A

A

JC


raw red mud, (b) 30℃, (c) 70℃, and (d) 80℃.

(a) (b)

(c)

Fig. 12. SEM micrographs of the red mud filtered sludge obtained in

(a) 30℃, (b) 70℃, and (c) 80℃.



31

D. Leaching Time and Solid to Liquid Ratio

The recovery efficiencies of three metal elements from

the red mud at different reaction times (1, 2, and 4 hours)

and solid to liquid ratio of 2% are shown in Fig. 13. The

other parameters are held constant at ultrasound power of

150W, reaction temperature of 70oC, and acid

concentration of 6N. And all the experiment was performed

three times and the average value was used.

Leaching time(hr) & solid/liquid ratio(%)

Reco

very

effic

iency

(%)

0

20

40

60

80

100

Iron

Aluminum

Titanium

2 hr, 2% 4 hr, 2%

2 hr, 4%1 hr, 2%

Fig. 13. Effect of reaction time on the recovery efficiencies of three

metallic component. (150 W, 6N, 70℃, 2%)

As can be seen in Fig. 13, the leaching time increased

from 1 to 4 hours, the ARE of Fe, Al, and Ti all showed an

increasing trend. When the reaction time increased from 1

hour to 2 hours, the increasing rates of the AREs for Fe, Al,

and Ti were 12.97 %point/hr, 10.8 %point/hr, and 11.67

%point/hr, but when the reaction time increased from 2

hours to 4 hours, the increasing rates of the AREs for Fe,

Al, and Ti were 0.42 %point/hr, 0.71 %point/hr, and 0.23

%point/hr, so enough leaching happened when the reaction

time was about 2 hours. As shown in Fig. 13, a decrease in

solid to liquid ratio enhances three metallic elements

recovery effectively when solid to liquid ratio of 2

compared to 4. If the quantity of sulfuric acid increases, the

viscosity of a mixture of sulfuric acid and red mud

decreases to provide smooth mixing to reduce the mass

transfer resistance to result in well leaching. And it is

judged that this is because if the solid to liquid ratio

increases, the stoichiometric ratio between solid and liquid

necessary for reactions becomes insufficient and dilute the

concentration of acidic solutions relatively [14].

E. Morphology of the Red Mud and Leached Residue

The SEM micrographs of raw red mud have a rough

surface, different shapes, and different particle sizes as

observed in Fig. 14(a) and (b).

The EDX analysis, for marked points (spectrum 4) in

Fig. 14(a), is shown in Fig. 14(c). The EDX mapping

corroborated the presence of Fe, Al, Ti, Si, and Ca. As

shown in Fig. 15(a) and (b), after the leaching, the sample

is distinguished by its smooth surface, due to cleanup

activity of the surface of solid by the ultrasonic radiation.

The EDX analysis, for marked points (spectrum 1) in Fig.

15(a), is shown in Fig. 15(c). From this phenomenon, it is

considered that the process of leaching has lowered the Fe,

Ai, and Ti content in the red mud filtered sludge.

(a) (b)

(c)

Fig. 14. SEM images (a, b) and EDX patterns (c) of raw red mud (the

(c) for spectrum 4 of (a)).

(a) (b)

(c)

Fig. 15. SEM images (a, b) and EDX patterns (c) of red mud filtered

sludge (the (c) for spectrum 1 of (a)).

IV. CONCLUSION

The experimental results by the acid solution extraction

combined with ultrasound to recover metal components

(Fe, Al, and Ti) in the red mud are summarized below.



32

1. The results indicate that recovery efficiencies of iron,

aluminum, and titanium increased with an increase of

ultrasound power, leaching temperature, and acidic

solutions, but decreased with the solid to liquid ratio.

The recovery efficiencies of iron, aluminum, and

titanium are 48.22%, 72.94%, and 88.95% respectively,

under the experimental conditions of in this study at

ultrasound power of 150 W, leaching temperature of

70oC, sulfuric acid concentration of 6N, leaching time 2

hours, and solid to liquid ratio of 2%.

2. As the strength of the ultrasonic waves increases, the

recovery efficiencies of three metallic components were

increased. The increasing rates of the average recovery

efficiencies of Fe, Al, and Ti depending on the increase

in the strength of ultrasonic waves from 0W to 50W

were 0.0540 %point/W, 0.0684 %point/W, and 0.0558

%point/W, and those of Fe, Al, and Ti from 50W to

150W were 0.1796 %point/W, 0.1250 %point/W, and

0.1262 %point/W, respectively.

3. The recovery efficiencies of three metallic components

increased in proportion to the increase in the

concentration of acidic solutions. The increasing rate of

the recovery efficiencies of Al is not large even though

the concentration of acidic solutions increases, but the

increasing rates of the recovery efficiencies of Fe and Ti

increase very much as the concentration of sulfuric acid

solutions increases.

4. There is a little difference in the increasing rates of

average recovery efficiency depending on the

temperature increase, but they showed a similar trend.

The increasing rates of the average recovery efficiencies

of three metallic components in 70oC∼80

oC slowed

down a lot, therefore, reaction temperature of 70℃ at the

experiment condition in this study will be suitable.

5. The recovery rates for 4 hours extraction were relatively

higher compared to 2 hours but did not show significant

difference. Therefore, experiments for 2 hours would be

more efficient than 4 hours considering the cost

consumed for the experiments.

Acknowledgment

This research was supported by the research foundation

from Hanseo University in 2012.

REFERENCES

[1] Wanchao Liu, Jiakuan Yang. Bo Xiao, “Review on treatment and utilization of bauxite residues in China” Int. J. Miner. Process. Vol.

93, 220–231, 2009.

[2] Edith Poulin, Jean-Francois Blais, Guy Mercier, “Transformation of

red mud from aluminum into a coagulant for wastewater treatment”, Hydrometallurgy, Vol. 82, 16-25, 2008.

[3] Dong-Young Jeong, Kyoung-Rae Choi, Moon-Hoon Kim and Chong-Hyun Hong, "An Experiment Study on Development of Eco-

Friendly Color Concrete Using Industrial Waste Red Mud", Journal

of Environmental Science International, Vol. 16, No. 8, 929-939, 2007.

[4] R. K. Paramguru, “Trends in Red Mud Utilization - A Review",

Mineral Processing & Extractive Metall. Rev., Vol. 26, 1-29, 2005.

[5] Shi Jinhui, Gu Guohua, Fu Xun, Wang Mingying, Hu Zhengshui,

“Extraction behavior of TOPO (or TRPO)–kerosene/Ti(IV)–H2SO4

systems and the preparation of TiO2 by predispersed-hydrolytic

method”, Colloids and Surfaces A: Physicochemical and

Engineering Aspects, Vo. 194, 207-212, 2001.

[6] E. Ercag, R. Apak, “Furnace smelting and extractive metallurgy of

red mud: recovery of TiO2, Al2O3, and pig iron", J. Chem. Technol. Biotechnol., Vol. 70, No. 3, 241-246, 1997.

[7] C. Klauber, M. Gräfe, G. Power, “Bauxite residue issues: II. Options

for residue utilization", Hydrometallurgy, Vol. 108, 11-32, 2011.

[8] Mason, T. J., “Practical sonochemistry", Mineral Processing &

Extractive Metall. Rev., Vol. 26, 1-29, 2005.

[9] Enes Sayan, Mahmut Bayramoglu, “Statistical modeling and

optimization of ultrasound-assisted sulfuric acid leaching of TiO2

from red mud”, Hydrometallurgy, Vol. 71, 397-401, 2004.

[10] S. Agatzini-Leonardou, P. Oustadakis, P.E. Tsakiridis, Ch.

Markopoulos, “Titanium leaching from red mud by diluted sulfuric acid at atmospheric pressure”, Journal of Hazardous Materials, Vol.

157, 579-586, 2008.

[11] Enes ayan, Mahmut Bayramolu, "Statistical modeling of sulfuric acid leaching of TiO2 from red mud", Hydrometallurgy, Vol. 57,

Issue 2, 181-186, 2000.

[12] Xiao-bin LI, Wei XIAO, Wei LIU, Gui-hua LIU, Zhi-hong PENG,

Qiu-sheng ZHOU, Tian-gui QI, "Recovery of alumina and ferric

oxide from Bayer red mud rich in iron by reduction sintering", Transactions of Nonferrous Metals Society of China, Vol. 19, No. 5,

1342-1347, 2009.

[13] Li Zhong, Yifei Zhang, Yi Zhang, "Extraction of alumina and sodium oxide from red mud by a mild hydro-chemical process",

Journal of Hazardous Materials, Vo. 172, 1629-1634, 2009.

[14] Xin Wang, C. Srinivasakannan, Xin-hui Duan, Jin-hui Peng, Da-jin

Yang, Shao-hua Ju, "Leaching kinetics of zinc residues augmented

with ultrasound", Separation and Purification Technology, Vol. 115, 66-72, 2013.

[15] S.M. He, J.K. Wang, J.F. Yan, “Pressure leaching of synthetic zinc

silicate in sulfuric acid medium”, Hydrometallurgy, Vol. 108, 171-

176, 2011.

[16] F.C. Xie, H.Y. Li, Y. Ma, C.C. Li, T.T. Cai, Z.Y. Huang, G.Q. Yuan, “The ultrasonically assisted metals recovery treatment of

printed circuit board waste sludge by leaching separation”, Journal

of Hazardous Materials, Vol. 170, 430-435, 2009.

[17] Enes Sayan, Mahmut Bayramoglu, “Statistical modeling of sulphuric

acid leaching of TiO2, Fe2O3 and Al2O3 from red mud”, Process Safety and Environmental Protection, Vol. 79, No. 5, 291-296, 2001.

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