Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.18 No.1 (March 2017) 57 - 69 

ISSN: 1997-4884 

 
 
 
 
 

Preparation Activated Carbon from Scrap Tires by Microwave 

Assisted KOH Activation for Removal Emulsified Oil  

 
Najwa Saber Majeed, Huda Adil Sabbar and Nawar O. A. Al-Musawi* 

Chemical Engineering Department-College of Engineering-University of Baghdad-Iraq  

*Civil Engineering Department-College of Engineering-University of Baghdad-Iraq    
 

Abstract 

In this paper activated carbon adsorbents produced from waste tires by chemical 

activation methods and application of microwave assisted KOH activation. The 

influence of radiation time, radiation power, and impregnation ratio on the yield and 

oil removal which is one of the major environmental issues nowadays and considered 

persistent environmental contaminants and many of them are suspected of being 

carcinogenic. Based on Box-Wilson central composite design, polynomial models 

were developed to correlate the process variables to the two responses. From the 

analysis of variance the significant variables on each response were identified.  

Optimum conditions of 4 min radiation time, 700 W radiation power and 0.5 g/g 

impregnation ratio gave 205.8749 mg/g oil removal and 35.19618 % yield. The 

characteristics of the AC were examined by pore structure analysis, and scanning 

electron microscopy (SEM).The BET surface area and total pore volume were 

identified to be 374.594 m²/g and 0.2039 m³/g, respectively. 

 

Key words: Waste tires, Activated Carbon, Activation, Microwave, Optimization, 

Adsorption. 

 

Introduction

One of the major environmental issues 

nowadays is the vast and widespread 

occurrence of oil in industrial 

wastewater and ground water. Oils 

(Both mineral and synthetic) are 

considered persistent environmental 

contaminants and many of them are 

suspected of being carcinogenic [1], 

the removal of oily pollutants from 

wastewater poses a problem, 

particularly when they are present in 

low concentrations, such as in 

industrial water. Reliability and its 

inexpensiveness, the adsorption 

technology is extensively used in oil 

removal. Traditionally, activated 

carbon has been widely used as an 

adsorbent for removing [2]. Activated 

carbon is a material that is produced 

from carbonaceous source materials, 

such as coal, coconuts, nutshells, 

peat, wood, and lignite. It has highly 

developed internal surface area and 

porosity, its pore volume typically 

ranges from 0.20 to 0.60 cm
3
/gm, and 

has been found to be as large as 

1cm
3
/gm. Its surface area ranges 

typically from 300 to 1500 m
2
/gm  [3]. 

A large capacity for adsorbing 

chemicals from gases and liquids. 

University of Baghdad 
College of Engineering 

Iraqi Journal of Chemical and 
Petroleum Engineering 

 

https://en.wikipedia.org/wiki/Peat
https://en.wikipedia.org/wiki/Wood
https://en.wikipedia.org/wiki/Lignite


Preparation Activated Carbon from Scrap Tires by Microwave Assisted KOH Activation for Removal 

Emulsified Oil 

  

  

58                                   IJCPE Vol.18 No.1 (March 2017)                 -Available online at: www.iasj.net 
 

Activated carbons are extremely 

versatile adsorbents of industrial 

significance and are used in a  wide 

range of applications which are 

concerned principally with removal of 

undesired species by adsorption from 

liquids or gases, in order to effect 

purification or the recovery of 

chemical constituents [3], the forms 

and characteristics of Activated carbon 

are highly dependent on the precursors 

and activation methods adopted for its 

production [5] it is used in many fields 

both in industry and daily life of every 

person. The usage of carbon 

adsorbents depend on their surface 

area, pore size distribution and 

chemical surface characteristics. The 

quality (surface area, pore size 

distribution and hence adsorptive 

properties) of it are directly related to 

the nature of starting material, the type 

of the production method and the 

temperature of production [6]. Waste 

tires are good starting materials for 

activated carbon production because of 

it containing a high fixed carbon 

content and cheap and available In 

addition to maintaining the 

environment from the risks of throwing 

tires [7].  

The preparation of AC involves of two 

stages, namely pyrolysis and activation 

[8]. Single step pyrolysis usually 

applied in the preparation of activated 

carbon using chemical activation 

method, which has low energy 

consumption, cheap shorter process 

duration and modest surface area and 

porosity. however, the conventional 

preparation of activated carbon using 

physical activation method was based 

on two step pyrolysis where 

carbonization and activation process 

takes place separately which has high 

energy consumption, expensive, longer 

process duration and high surface area 

and porosity. The product quality of 

two step pyrolysis is better compared 

to the single step pyrolysis [9]. The 

thermal process may need several 

hours, even up to a week to make the 

desired level of activation another 

trouble related to the furnace is that the 

surface heating does not ensure a 

regular temperature for various shapes 

and sizes of samples [10]. Therefore, it 

is necessary to find a rapid and easy 

route for the preparation of AC. 

Although microwave heating is today a 

mature technique which finds wide 

applications in the area of material 

science, food processing and analytical 

chemistry [11], The major advantage 

of using microwave heating is: Heat 

emitted from microwave be fast and 

uniform, Direct using of big-sized 

feedstock, Treatment of non-

homogeneous wastes, Minimize waste 

and material recovery, best production 

quality, Production of new materials 

and products .Total cost effectiveness, 

savings, and reduce dangers to humans 

and the environment [12]. In addition 

to use microwave heating in the 

production of char was found to 

produce desirable changes in its 

textural and chemical properties 

comparing to the char produced by 

conventional met hods. For instance, a 

cleaner porous structure has been 

reported by Miura et al., 2004 in the 

pyrolysis of wood, [13]. 

(RSM) approach. RSM has been found 

to be a useful tool to study the 

interaction of two or more factors [14]. 

A standard RSM design called Box-

Wilson central composite design is 

suitable for fitting a quadratic surface 

and it helps to optimize the effective 

parameters with a minimum number of 

experiments, as well as to analyze the 

interaction between the parameter [15]. 

RSM has just recently been used for 

the optimization of activated carbon 

production from rattan sawdust [14]. 

The aim of this work is to optimize the 

preparation conditions of AC from 

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scrape tires by chemical activation for 

the removal of emulsified oil from 

waste water. The effects of radiation 

time, radiation power and 

impregnation ratio are also studied 

simultaneously to obtain a high oil 

removal using the Box-Wilson central 

composite design.  

 

Materials and Method  

 

Materials  
Scrape tires were used as the precursor 

for the preparation of AC. waste tires 

were washed with water to get rid of 

impurities, then shredded using an 

electrical drill (BOSCH 305) adopted 

with crushing disk and sieved .Fraction 

with particle size of (1.18-2.36) mm 

was selected for the preparation. 

Potassium hydroxide (KOH), 

(purchased from Didactic company, 

Espuma) MW=56.10 of purity 99.9% 

was used as a chemical activator. Span 

85 and Tween-80 materials that 

increases the emulsifying. 

Cyclohexane (C6H12) which used as 

the extraction solvent, other chemical 

used such as hydrochloric acid were 

from analytical grades. 

. 

Preparation of Activated Carbon 

 A weighed amount (2g) of dried 

waste tires was mixed with 10 ml of 

KOH solution at various impregnation 

ratios (0.5 – 1.5 g/g) for 24 h at room 

temperature. The samples were next 

placed in an dryer (Model IH – 100, 

England) at 110 °C until completely 

dried then the dry samples were 

activated by using a quartz glass 

reactor in microwave at different 

radiation powers (400–700W) for 

different radiation times (4_12min), 

Samsung Mode (lMS23F301E), 

Malaisie, it can reach a maximum 

power of (800 watt) The upper surface 

of microwave  had a removable cover 

connected to a stainless steel pipe of 

5mm inside diameter from which 

pyrolysis gases were exit ,with quartz 

glass reactor 2.5 cm  diameter x 12.5 

cm length as  it is shown in Figure 1. 

After activation, the sample was 

withdrawn from the oven and allowed 

to cool. the sample was mixed with 

0.1M HCl solution at 10 mg/l solid to 

liquid ratio. The mixture was left 

overnight at room temperature, and 

then filtered and subsequently the 

sample was repeatedly washed with 

distilled water to remove residual 

organic matters and alkalis, until the 

pH of filtrate reached (6.5 – 7). After 

that, the sample was dried at 110Cº for 

24 h. and subsequently was weighed. 

Finally the sample was stored in tightly 

closed bottles. 

 

 
Fig. 1: photographic picture of microwave unit 

for preparation of Activated carbon 
 

Process Performance 

The performance of chemical 

activation process was determined by 

the product yield, along with its 

removal oil. 
  
Yield  
The yield is defined as the ratio of final 

weight of the obtained product after 

washing and drying to the weight of 

dried precursor initially used. The 

yield of AC was calculated based on 

the following equation: 
 

 Yield (%) =
  

  
                      …(1) 

 

Where Wf and Wo are the weight of 

final AC product (g) and the weight of 

scrape tires (g), respectively. 

 

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Preparation Activated Carbon from Scrap Tires by Microwave Assisted KOH Activation for Removal 

Emulsified Oil 

  

  

60                                   IJCPE Vol.18 No.1 (March 2017)                 -Available online at: www.iasj.net 
 

Removal of Oil 

A solution of oily water prepared by 

mixing 0.225g of the motor oil and 

0.025 of span85 and tween80 (which 

increase the stability of the emulsion) 

with 500 mL of water to prepared 500 

ppm. The mixture was then stabilized 

in laboratory homogenizer Disperser at 

10000 rpm speed for 30 second. The 

resultant solution was milky white, 

which exhibited the character of 

chemically stabilized solution Added 

0.5gram of activated carbon to 200 ml 

of the resulting mixture(500 ppm) and 

then stirred with a magnetic stirrer (400 

rpm) for 4 hour then the solution leaves 

a period of time and then be pulled 100 

ml from the central region to avoid 

impurities. A sample of (100 ml) of 

solution was placed in conical flasks of 

(250 ml) and added drops of (1M)of 

HCL  to neutralize the solution, and  to 

extract the oil (10 ml) of cyclohexane, 

then  it was shocked by  hand   for one 

minute  and pulled  a sample of the  

cyclohexane was added  accumulated  

in the upper region for examination  oil 

concentration by using TD500DTM Oil 

in Water Meter. The amount of 

adsorption at equilibrium, qe (mg/g), 

was found using Equation 2: 

 

  =
         

 
                                   …(2)  

 

Where C0 and Ce (mg/L) are the 

liquid-phase concentrations of oil at 

initial and equilibrium, respectively. V 

(L) is the volume of the solution and 

W (g) is the mass of activated carbon.  

Adsorption isotherms that were carried 

out in a set of 700 ml emulsion oil in 

water at 500ppm with different weights 

of activated carbon (0.35, 1.75, 3.5, 

5.25, and 7) gram were placed in these 

beakers, at 400rpm and pH equal 7. 

Similarly the concentration of oil in 

water was calculated at different time 

(10 min, 30 min, 60 min, 90 min, 120 

min, and 24 h) and by using Equation 2 

the amount of adsorption at 

equilibrium, qₑ (mg/g).  

 

Experimental Design  
In order to organize the experiments of 

AC preparation from scrap tires, a 

standard RSM design, known as Box- 

Wilson central composite design was 

adopted. This design can reduce the 

number of experimental trails needed 

to evaluate multiple parameters and 

their interactions [16]. Box-Wilson 

design consists of 2n factorial points, 

2n axial points, and one center point, 

where n is the numbers of variables. In 

order to design the experiments, the 

operating range of variables must be 

specified, thus: radiation power X1 

(400-700 W), radiation and 

impregnation ratio X2 (0.5-1.5 g/g) 

radiation time X3 (4-12 min). The total 

number of experiments N is computed 

according to the following equation: 

 

N=  +2n+1                                  …(3) 
 

The relationship between the coded 

variable and the corresponding real 

variable is as follows: 

 

       
               
            

 

               …(4) 

 

Characterization of Activated 

Carbon 
1. Total surface area 

Surface area is one of the key 

indicators attributed to the adsorptive 

properties of porous materials [17], it 

generally calculated by the BET 

method (Brunauer, Emmett and Teller 

1). This method works at the low-

pressure range of the adsorption 

isotherm of a molecule of known 

dimensions (commonly nitrogen). 

Nitrogen adsorption experiments were 

done to compute the specific surface 

area of the test samples using a 

Quantachrome Nova-1200 instrument 

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at 77k. The samples were out gassed 

overnight at 180 °C before the 

adsorption measurements. The BET 

model was used to be suitable for the 

nitrogen adsorption isotherms and 

estimate the specific surface area of the 

samples [18]. 

2. Pore size distribution 

Pores in different sizes are important to 

the adsorbents overall capacity in 

adsorption processes. The presence of 

micro- and mesopores in activated 

carbons enhance the adsorption of 

large adsorbates [7]. 

3. Capacity 

Capacity it is the amount which the 

adsorbent taken up from adsorbate by 

per adsorbent. It depends on the initial 

condition of the adsorbent, the fluid 

phase concentration and temperature. 

Adsorption capacity data are gathered 

at various adsorbate concentrations and 

a fixed temperature, and the data are 

plotted as an isotherm (loading versus 

concentration at constant temperature). 

4. Bulk Density 

Bulk density is defined as the ratio of 

the mass of the material to the total 

volume occupied by material. The total 

volume corresponds to the pore and 

inter-particle volume. Bulk density of 

the matter varies depending on it’s 

composition. 
 

Results and Discussion 
 

Model Fitting and Statistical 

Analysis for Chemical Activation 

Sample  

The response of experiments 

conducted according to Box – Wilson 

method, which represented by oil 

removal and activated carbon yield, is 

fitted to a second and third order 

polynomial mathematical model and 

the optimum response is calculated 

from this model, it determined the 

effect of each parameter. At first the 

predictions equation (Y=A+BX)   used 

which represent first order equation for 

independent studied variables (Power: 

X1, Ratio: X2, Time: X3, Responsible 

variables: Y and constant: A, so 

predictions equation become: 

 

Y=const+B1*X1+B2*X2+B3*X …(5) 

 

Then second order polynomial 

mathematical model applied which 

give had form for three variable more 

accurate. 

 

Y= Bₒ + B1 X1 + B2 X2 + B3 X3 + B4 

X1 X2 + B5 X1 X3 + B6 X2 X3+ B7 X1
2
+ 

B8 X2
2
 + B9 X3

2
                             …(6) 

 

Ʃ x1 / n = Ʃ x2 / n = Ʃ x3 / n = Ʃ x1 x2 / n 

= Ʃ x1 x3 / n = Ʃ x2 x3 / n = 0, and: 

 

Ʃ x1
2
 / n = Ʃ x2

2
/ n = Ʃ x3

2
/ n = 0.933 

 

The Equation 6 become: 

 

Y= y+ B1 X1 + B2 X2 + B3 X3 + B4 

X1 X2 + B5 X1 X3 + B6 X2 X3 + B7 

(X12 – 0.933) + B8 (X22 – 0.933) + 

B9 (X32 – 0.933)                          …(7) 

 

And third order 

 

Y=const+B1*X1+B2*X2+B3*X3+B4

*X1*X2+B5*X1*X3+B6*X2*X3+B7

*(X1**2-0.933)+B8*(X2**2-0.933) 

+B9*(X3**2-0.933)+B10*(X1**3)+ 

B11*(X2**3)+B12*(X3**3)+B13*X1

*X2*X3                                        …(8)   

 

It used above equations which get to 

the correlation factor nearer to one. 

The final form becomes: 
 

                           
                      
               
                         
                    
                         
                           
                        
                           
                                        …(9) 

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Preparation Activated Carbon from Scrap Tires by Microwave Assisted KOH Activation for Removal 

Emulsified Oil 

  

  

62                                   IJCPE Vol.18 No.1 (March 2017)                 -Available online at: www.iasj.net 
 

                              
                       
                       
                          
                    

                            
                          …(10) 
 

The Table 1 show values of the 

independent variables corresponding to 

the final form of the equation of yield 

and oil removal. 

 
Table 1: Values of the Independent Variables Corresponding to the Final Form of the Equation of 

Yield and Oil Removal 
 

Table 1a: Values of the Independent Variables Corresponding to the Final Form of the Equation of 

Yield and Oil Removal 
 

Coded  variables Real variables 

Yield (%) Oil removal (mg ∕g ) 

 

 

Y 

 

(coded variables) 

Y 

  (coded variables) 

no X1 X2 X3 X1 X2 X3 y Residuals y Residuals 

1 1 1 -1 463.4 0.71 5.7 88 86.11463788 1.885362 194.92 195.5772812 -0.65728 

2 -1 -1 1 636.6 0.71 5.7 52 50.11463588 1.885364 198.2 198.2947812 -0.09478 

3 1 -1 1 463.4 1.3 5.7 62 60.11463988 1.88536 185.2 185.2947812 -0.09478 

4 -1 1 1 636.6 1.3 5.7 48.7 46.81463788 1.885362 190.48 191.1372812 -0.65728 

5 1 1 1 463.4 0.71 10.3 54.2 52.31463788 1.885362 191.96 192.0547812 -0.09478 

6 -1.732 0 0 636.6 0.71 10.3 74 72.11463588 1.885364 187.56 188.2172812 -0.65728 

7 1.732 0 0 463.4 1.3 10.3 93.16 91.27463988 1.88536 195.8 196.4572812 -0.65728 

8 0 -1.732 0 636.6 1.3 10.3 31 29.11463788 1.885362 195.9 195.9947812 -0.09478 

9 0 1.732 0 400 1 8 65.9 68.41395525 -2.51396 194.52 194.0185477 0.501452 

10 0 0 -1.732 700 1 8 68 70.51395432 -2.51395 195.52 195.0185472 0.501453 

11 0 0 1.732 550 0.5 8 42.2 44.7139608 -2.51396 196 195.498549 0.501451 

12 0 0 0 550 1.5 8 55 57.51396396 -2.51396 192.52 192.0185472 0.501453 

13 1 1 -1 550 1 4 80 82.51395366 -2.51395 187.44 186.9385458 0.501454 

14 -1 -1 1 550 1 12 39.8 42.31395515 -2.51396 194.28 193.7785493 0.501451 

15 1 -1 1 550 1 8 63.6 63.59910988 0.00089 193.16 193.1601552 -0.00016 

        R=.992415272   R=.99321325  

Y: observed value         y: calculated value 
 

Table 1b: Values of the Independent Variables Corresponding to the Final Form of the Equation of 

Yield and Oil Removal 
 

Coded  variables Real variables 

Yield (%) 

(Real variables) 

Oil removal (mg ∕g) 

( real variables) 

no X1 X2 X3 X1 X2 X3 y Residuals y Residuals 

1 1 1 -1 463.4 0.71 5.7 87.0284781 0.971521903 195.05277 0.1327663 

2 -1 -1 1 636.6 0.71 5.7 52.44198703 -0.441987025 197.45902 -0.7409794 

3 1 -1 1 463.4 1.3 5.7 60.86207183 1.13792817 184.41962 -0.7803832 

4 -1 1 1 636.6 1.3 5.7 49.04515041 -0.345150407 190.08274 -0.3972646 

5 1 1 1 463.4 0.71 10.3 53.5071943 0.692805702 192.97879 1.0187855 

6 -1.732 0 0 636.6 0.71 10.3 74.81534444 -0.815344435 188.95471 1.3947126 

7 1.732 0 0 463.4 1.3 10.3 92.39491428 0.76508572 197.10518 1.3051821 

8 0 -1.732 0 636.6 1.3 10.3 31.71814296 -0.718142957 196.33797 0.4379737 

9 0 1.732 0 400 1 8 69.08168428 -3.181684283 193.75079 -0.7692064 

10 0 0 -1.732 700 1 8 73.81767748 -5.817677483 195.12248 -0.3975164 

11 0 0 1.732 550 0.5 8 46.42729498 -4.227294983 195.05562 -0.9443824 

12 0 0 0 550 1.5 8 59.25529498 -4.255294983 192.27897 -0.2410314 

13 1 1 -1 550 1 4 83.92604498 -3.926044983 188.57718 1.1371786 

14 -1 -1 1 550 1 12 44.41254498 -4.612544983 191.99552 -2.2844774 

15 1 -1 1 550 1 8 64.98529498 -1.385294983 193.10464 -0.0553614 

       R=0.99204284  R=0.99321325  

Y: observed value         y: calculated value 
 

Process Optimization  
At optimum conditions, the prepared 

AC should have a high yield and high 

removal oil. However, it is difficult to 

optimize both these responses under 

the same condition because the interest 

region of variables is different, when  

oil removal increases, carbon yield 

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decrease and vice versa. Therefore, the 

optimum conditions have been 

determined depending on achieving 

high removal oil. The optimum 

operating conditions has been 

determined by studying each 

independent variable alone [19]. Thus, 

the optimum conditions corresponding 

to a maximum removal oil are 4 min 

radiation time, 700 W radiation power, 

and 0.5 g/g impregnation ratio which 

determined by study every parameter 

with changing two other parameter as  

show in Table 2. At these conditions, 

205.8749 mg/g oil removal with 

35.19618 % yield were reported 

experimentally. 
 

Effect of Process Variables  
 

Effect of Radiation Time  

The effect of radiation time on yield 

and oil removal of prepared activated 

carbon at different radiation powers 

and different impregnation ratio is 

shown in Figure 2. Shows that the 

yield of AC decreases with increasing 

of radiation time at impregnation ratio 

(0.5, 0.75, 1, 1.25, and 1.5) g ∕g. 

At 400 w radiation power, the radiation 

time increasing from 4 to 12 min leads 

to decreases   in yield from 88 to 70 % 

when impregnation ratio equal 0.5 g ∕g. 

this is probably due to rapid evolution 

of volatile materials to form stable 

compounds, and this situation 

corresponds to the explanation by Foo 

and Hameed [20]. They showed that a 

steep decrease in yield occurs for 

production of AC from coconut husk 

by microwave KOH activation [3]. 
 

 
Fig. 2: Effect of radiation time on yield at 

different impregnation ratio (radiation 

power=400 w) 

The effects of radiation time on oil 

removal are demonstrated in Figure 3 

that show oil removal increase with 

increasing radiation time at higher 

impregnation ratio and it decrease with 

increase radiation time at low 

impregnation ratio. At radiation   

power 400 w, at impregnation ratio 

equal 1.5 g ∕g, oil removal is 

demonstrably increase from 170.28 to 

205.144 mg∕ g    while at impregnation 

ratio equal 0.5 g ∕g oil removal 

decrease from 199.5987 to 190.94 

mg/g with increase radiation time 4-12 

min .At higher impregnation ratio, 

prolonging radiation time promotes an 

acceleration of temperature or energy, 

which in turn increase the reaction 

rates , de volatilization and led to 

opening of micropores and mesopores 

which resulted in expansion of the 

average diameter thus developed the 

porosity and rudimentary of the pore 

structure. But in low impregnation 
ratios, oil removal decreased with 

increasing radiation time, probably due 

to turn mesopores to macropores  and  

sintering effect, which hugely crashed 

the pore walls between relative pores 

(Foo and Hameed, 2012) [20]. 

 

 
Fig. 3: Effect of radiation time on oil removal 

at variable impregnation ratio (radiation 

power=400 w) 

 

Effect of Radiation Power 

The effect of radiation power on yield 

and oil removal of prepared activated 

carbon at different radiation time is 

shown in Figures 4 and 5. Figure 4 

shows that the yield of AC decreases 

with increasing of radiation power at 

radiation time 4-12 min. 

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Preparation Activated Carbon from Scrap Tires by Microwave Assisted KOH Activation for Removal 

Emulsified Oil 

  

  

64                                   IJCPE Vol.18 No.1 (March 2017)                 -Available online at: www.iasj.net 
 

At impregnation ratio 0.5 g/g when 

radiation power change from 400 to 

700 w, yield decrease from 86 to 55%   

at radiation time equal to 4 min, it 

illustrated that loss of the volatile 

materials with increasing power. Then 

the lower rate of yield decrease was 

noticed where a stable structure is 

formed. However, at a high radiation 

power over-gasification might occur 

causing destruction of pore structures, 

thus the removal oil and carbon yield 

decreased gradually. The weight loss 
of carbon increased proportionally to 

the microwave power, mainly 

attributable to the robust reaction at 

higher thermal radiation which 

massive   devolatilization, dehydration 

and putridity [20]. 

 

 
Fig. 4: Effect of radiation power on yield at 

variable radiation time (impregnation ratio 

=0.5) 

 

The effects of radiation power on oil 

removal are demonstrated in Figure 5 

that show oil removal increase with 

increasing radiation power at low 

radiation time. But in high radiation 

time, oil removal decrease with 

increasing radiation power. 

At   impregnation ratio equal 0.5 g/g, 

oil removal increased from 199.5987 

to 205.87 mg/g at 4 min radiation time 

while oil removal decrease from 

190.949 to 177.8548 mg/g at 12 min 

radiation time with increases the 

radiation power from (400-700), at low 

radiation time, increasing the 

microwave power was to induced 

higher internal and volumetric heating 

leading to the development of new 

pores thereby enhancing the adsorption 

capacity and  possibly ascribed to the 

joint effect of internal and volumetric 

heating responsible for the expansion 

of the carbon structure creation of raise 

porosity and a bigger surface area [20]. 

But in high radiation time increase in 

power might be due to the sintering 

effect at high power, followed by 

shrinkage of the char, and realignment 

of the carbon structure which resulted 

in reduced pore areas as well as 

volume this situation corresponds to 

the explanation by Deng et al. [21] 

who reported for MB uptake on AC 

prepared from cotton stalk by 

microwave assisted KOH activation. 

 

 
Fig. 5: Effect of radiation power on oil 

removal at different radiation time 

(impregnation ratio =0.5) 

 

Effect of Impregnation Ratio 

The effect of impregnation ratio 

on yield and oil removal of prepared 

activated carbon at different radiation 

time and different radiation power is 

shown in Figures 6 and 7. 

Figure 6 shows that the yield of AC 

decreases with increasing of radiation 

ratio at radiation time 4 and 6 min at 

radiation power (400, 475, 550,636.6, 

and 700) watt. 

At 4 min radiation time yield  decrease 

from 91.3 to 61.6% when impregnation 

ratio increase  from  0.5 to 1.5 g/g at 

400 watt power radiation This decrease 

is due to the continuous removal of tar 

material from the pores.. This behavior 

agrees with results obtained by 

Sudaryanto [22] for AC production 

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from cassava peel by chemical 

activation with potassium hydroxide. 

This is the same in the case at radiation 

time 6 min with decrease in yield with 

increase radiation time. 

 

 
Fig. 6: Effect impregnation ratio on yield at 

different radiation power (radiation time 

=4min) 

 

The effects of impregnation ratio on oil 

removal are demonstrated in Figure 7 

that show oil removal increase with 

increase impregnation ratio at height 

radiation time, but at low radiation 

time it decrease with increase 

impregnation ratio. Figure 8, at 12 min 

radiation time and 400 w radiation 

power, removal oil increase from 
190.95 to 205.149 mg/g while oil 

removal decrease from 199.59 to 

170.2881 mg/g at 4 min radiation time. 

At height radiation time, the potassium 

compound created during the 

activation step would spread into the 

internal structure of tires matrix and 

expansion existing pores. Therefore, 

by rising the ratio of KOH to tires, the 
activation process would play a key 

role in pore modelling. The pore width 

was successively broadened and new 

micropores - mesopores were formed 

in the off-center pore walls, giving a 
self-sustaining increase in BET surface 

area and pore volume. 

Correspondingly, but in low radiation 

time, the  oil removal was  extra 

enhanced., increase KOH and metallic 

potassium  did not take enough time to 

gas left in the carbon surface caused 

blockage of the pores leading to carbon 

burn of and mutation of micropores-

mesopores into macropores lessening 

the oil removal [20]. 
 

 
Fig. 7: Effect impregnation ratio on oil 

removal at variable radiation power (radiation 

time =4min) 
 

 
Fig. 8: Effect impregnation ratio on oil 

removal at variable radiation power (radiation 

time =12min) 
 

Table 2: studying best variable that achieve 

maximums oil removal  
constant 

variable 

Best variables in constant 

certain variable 

Maxim oil 

removal(mg/
g) 

Effect of Radiation Time 

Radiation 

power 
(watt) 

impregnation 

ratio(g/g) 

Radiation 

time 
(min) 

Maxim oil 

removal 
(mg/g) 

400 1.5 12 205.144 

475 1.5 12 203.26 

550 1.5 12 202.04 

625 0.5 4 203.068 

700 0.5 4 205.87 

Effect of Radiation power 

impregnati

on 

ratio(g/g) 

impregnation 

time(min) 

radiation 

power 

(watt) 

Maxim oil 

removal 

(mg/g) 

0.5 4 700 205.87 

0.75 4 700 200 

1 12 400 197 

1.25 12 400 201 

1.5 12 400 205.14 

Effect of impregnation ratio 

impregnation 

time(min) 

radiation 

power 

(watt) 

impregnation 

ratio(g/g) 

Maxim oil 

removal 

(mg/g) 

4 700 0.5 205.87 

6 700 0.5 200.98 

8 400 0.5 198.09 

10 700 1.5 199.854 

12 400 1.5 205.144 

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Preparation Activated Carbon from Scrap Tires by Microwave Assisted KOH Activation for Removal 

Emulsified Oil 

  

  

66                                   IJCPE Vol.18 No.1 (March 2017)                 -Available online at: www.iasj.net 
 

Adsorption Isotherms of Emulsified 

Oil on Activated Carbon Prepared 

at Optimum Condition 

The adsorption isotherm is the most 

extensively employed method for 

representing the equilibrium states of 

an adsorption system. The adsorption 

isotherm gives useful information 

regarding the adsorbate, the adsorbent, 

and the adsorption process, the results 

of this fitting, as summarized in Table 

3 show that Sips isotherm has the 

highest R
2 

value as compared to that of 

both Langmuir and Freundlich 

isotherms. The Sips model correlates 

the equilibrium data with R
2
 values. 

 

 
Fig. 9: sips adsorption isotherm of oil on 

activated carbon at 25   
 

Table 3: Isotherm parameters for oil 

Adsorption onto activated carbon with the 

Correlation Coefficient 

Model Parameters Values 

Langmuir  

 
  

          
        

 

 

KL(l/mg) 
0.003054 

q,max(mg/g) 
230.5 

R
2
 0.993 

RL
 0.395 

Freundlich 

   
     

 
 ⁄  

 

Kf 
0.571428 

N 0.9639 

R
2 0.99 

Sips 

  

 
      

 
 ⁄

      
 

 ⁄
 

qm(mg/g) 265 

Ks((l/mg)
1/m

) 0.002155 

n 0.96445 

R
2 

0.997 

 

 
Fig. 10: adsorption isotherm for oil by 

activated carbon (  =500mg/l, temp=25 and 
dp= 1.18-2.36mm) 
 

Characterization of Activated 

Carbon  
 

BET Surface Area and Pore Volume  
The BET surface area, total pore 

volume of AC prepared at optimum 

conditions are found to be 374.594 

m²/g, 0.2039 m³/g These values higher 

than that reported by Skodras  et al 

[22] who show the BET surface area of 

activated carbon from tires by KOH 

activation were 358.5 m
2
/g AC. Table 

4 shows the Comparison on the 

application of microwave heating to 

the production of activated carbon 

from different material. 
 

Table 4: summary of previous works on 

preparation of activated carbons produced by 

waste tires [5] 
 

References 
 

Activating 

Agent 

 
Activation 

conditions 

BET 
surface 

Area 

(m2 / 
g) 

 

This study 

KOH Power=625w, 

Time=6min and 
Ratio=0.75 g/g 

374.59 

Skodras et 

al., 
(2007) 

Steam Temp=900 ,Time= 2 358.5 

Helleur et 

al., 

(2001) 

Steam 

CO2 

Temp=900 ,Time=3 

Temp=875 ,Time= 7 

272 

270 

Sainz-Diaz 

and 

Griffiths, 
(2000) 

CO2 Temp=1000 ,Time=5 

Temp=1000 ,Time=7 

431 

284 

Cunliffe and 

Williams, 

(1999) 

Steam 

 

Temp=935 

Time= - 

640 

Streat et al., 

(1995) 

- 

Steam Temp=800 ,Time= 24 

Temp=900 ,Time= 18 

346 

155 

Belgacem et 
al., 

2013 

phosphoric 
acid 

Temp=650 
Time= 2hand 30min 

400 

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Najwa Saber Majeed, Huda Adil Sabbar and Nawar O. A. Al-Musawi  

 

-Available online at: www.iasj.net                       IJCPE Vol.18 No.1 (March 2017)                        67 
 

Surface Morphology  
Figures 11a and b show SEM images 

of scrap tires and AC production by 

two ways: physical and chemical 

activation methods. It can be found 

that the surface of tires is free of any 

pores, constricted and blocked by 

deposited tray substance. However, the 

microwave irradiation sample 

demonstrated a well-developed and 

uniform surface, forming an orderly 

pore structure. The development of 

porosity is associated with gasification 

according to the following reduction 

reactions [23]: 

 

6KOH + 2C → 2K + 3H2 +2K2CO3  

 

K2CO3 was reduced by carbons to 

form K, K2O, CO and CO2 so that 

more pores were formed as follows: 

 

    K2CO3 +2C → 2K + 3CO 

    K2CO3→ K2O + CO2 

 
 

It was assumed that metallic 

potassium K formed during the 

gasification process would diffuse into 

the internal structure of carbon matrix 

widening the existing pores and 

created new porosities. Figure 11b also 

shows that the surface of prepared 

carbon contains some cavities which 

are resulted from the evaporation of 

impregnated KOH derived compounds, 

leaving the space previously occupied 

by the reagent. Theses cavities provide 

channels for the adsorbate molecules to 

access the micropores and mesopores 

inside a carbon particle. 

 

 
(a) 

 

 
(b) 

 

 
(c) 

 
Fig. 11: SEM micrographs (10 kx) of srape 

tires (A) and (50kx) AC by physcal method 

(B) AC  method (C) by chemicl 

 

Conclusion  
Activated carbons were prepared from 

scrape tires by microwave assisted 

KOH activation. 205.8749 mg/g 

removal oil with corresponding yield 

of 35.1961 % were obtained at 

optimum conditions of 4 min radiation 

time, 700 W radiation power, and 0.5 

g/g impregnation ratio. Also, the 

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Preparation Activated Carbon from Scrap Tires by Microwave Assisted KOH Activation for Removal 

Emulsified Oil 

  

  

68                                   IJCPE Vol.18 No.1 (March 2017)                 -Available online at: www.iasj.net 
 

surface area, pore volume of AC were 

374.59 m²/g, 0.2039 m³/g .Box-Wilson 

central composite design was adopted 

for arrangement of preparation 

experiment. Two second order 

polynomial models were successfully 

used to correlate the process variables 

to the two responses.   

 

Acknowledgement  
We gratefully acknowledge 

Department of Chemical Engineering 

and University of Baghdad for assist 

and support of this work. 

 

References 

1. Harvey, R. G. (1991). Polycyclic 
aromatic hydrocarbons: chemistry 

and carcinogenicity. Cambridge 

University Press,Cambridge, 

England.  

2. Simonović, B. R., Aranđelović, D., 
Jovanović, M., Kovačević, B., Pezo, 

L., & Jovanović, A. (2009). 

Removal of mineral oil and 

wastewater pollutants using hard 

coal. Chemical Industry and 

Chemical Engineering 

Quarterly, 15(2), 57-62.  

3. Kareem R.A. (2014)" Sustainable 
Production of Local Adsorbent 

Material from Waste Tires for 

Removal of Lead from Aqueous 

Solution". University of Baghdad. 

College of Engineering. M.Sc. 

Thesis. 

4. Manocha  S. M. (2003). Porous 
carbons. Sadhana, 28(1-2), 335-348.  

5. Abbas A.F. 2014," Preparation of 
activated carbon from date stones 

by K2CO3 activation for methylene 

blue dye adsorption", M.Sc. Thesis 

,College of engineering, Baghdad 

University. 

6. Yagsi N. U. (2004). Production and 
characterization of activated carbon 

from apricot stones (doctoral 

dissertation, Middle East technical 

university). 

7. Mui, E. L., Ko, D. C., & McKay, G. 
(2004). Production of active carbons 

from waste tyres––a review. Carbon 

8. T.H. Liou, (2010), Development of 
mesoporous structure and high 

adsorption capacity of biomass 

based activated carbon by 

phosphoric acid and zinc chloride 

activation, Chem. Eng. J. 158(2), 

129-142.  

9. Hameed, B. H., Tan, I. A.W. and 
Ahmed, A. L.( 2009) “Preparation 

of oil palm empty fruit bunch. 

Based activated carbon for removal 

of 2, 4, 6-

trichlorophenol:Optimization using 

response surface. 

10. Chaied M. A.(2015)" Microwave 
Assisted Preparation of Activated 

Carbon from Phragmites (Reed) for 

Antibiotics Adsorption" ,M.Sc. 

Thesis ,College of engineering, 

Baghdad University. 

11. M. Komorowska, G.D. 
Stefanidies, T. Van Gerven, A. L. 

Stankiewicz, (2009), Influence of 

microwave irradiation on a 

polyesterification reaction, Chem. 

Eng. J. 15 (3), 859-866. 

12. Fernández, Y., Arenillas, A., & 
Menéndez, J. Á. (2011). Microwave 

Heating Applied to Pyrolysis, 

Advances in Induction and 

Microwave   Heating of Mineral 

and Organic Materials, Stanisław 

Grundas (Ed.), ISBN: 978-953-307-

522-8, InTech. 

13. Miura, M., Kaga, H., Sakurai, A., 
Kakuchi, T. I. & Takahashi, K. I. 

2004. Rapid pyrolysis of wood 

block by microwave heating. 

Journal of Analytical and Applied 

Pyrolysis ,71, 187-199. 

14. A. A. Ahmad, B. H. Hameed, A. 
L. Ahmed, (2009), Removal of 

disperses dye from aqueous solution 

using waste derived activated 

carbon: optimization study, J. 

Hazard. Mater.170, 612-619. 

http://www.iasj.net/


Najwa Saber Majeed, Huda Adil Sabbar and Nawar O. A. Al-Musawi  

 

-Available online at: www.iasj.net                       IJCPE Vol.18 No.1 (March 2017)                        69 
 

15. A. M. M. Varagas , C. A. Garcia 
, E. M. Reis , E. Lenzi , W.F. Costa 

, V. C. Almeida , (2010), NaOH- 

activated carbon from flamboyant 

(Delonixregia) pods ; Optimization 

of preparation condition using 

central composit rotatable design , 

Chem. Eng. J. 162,43-50.  

16. Tan I. A. W., Ahmed A. L., 
Hameed B. H., (2008) , Preparation 

of activated carbon from coconut 

husk: Optimization study on 

removal of 2, 4, 6-trichlorophenol 

using response surface 

methodology, J. Hazard. Mater, 

153, 709-717. 

17. Mui, E. L., Ko, D. C., & McKay, 
G. (2004). Production of active 

carbons from waste tyres––a 

review. Carbon. 

18. Cleiton A. Nunes; Mário C. 
Guerreiro 2011"Estimation of 

surface area and pore volume of 

activated carbons by methylene blue 

and iodine numbers", Quím. 

Nova vol.34 no.3 São Paulo. 

19. Edger T. F., Himmelblau D. M, 
(2001), Optimization of chemical 

process, 2nd Ed, McGraw-Hill 

Chemical Engineering series. 

20. Foo. K. Y. & Hameed B. H. 
(2012). Microwave-assisted 

preparation and adsorption 

performance of activated carbon 

from biodiesel industry solid reside: 

influence of operational parameters. 

Bioresource technology, 103 (1), 

398-404. 

21. Deng, H., Li, G., Yang, H. and 
Tang, J. 2010a, “Preparation of 

activated carbon from Cotton stalk 

by microwave assisted KOH and 

K2CO3 activation”, Chem. Eng. J., 

163, 373-381. 

22. Sudarynto, Y., Hartono, S. B., 
Irawaty, W. and Ismadji, S. 2006, 

“High surface area activated carbon 

prepared from cassava peel by 

chemical activation”, Bioresour. 

Technol., 97, 734-739. 

23. D.W. McKee, (1983), 
Mechanisms of the alkali metal 

catalyzed gasification of carbon, 

Fuel, 62, 170-175.  

 
 

 

 

 

 

 

 
 

 

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