Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.14 No.2 (June 2013) 49- 55 

ISSN: 1997-4884 

 

 

 

 

Reverse Osmosis Polyamide Membrane for the Removal of Blue and 

Yellow Dye from Waste Water 

 
Nada Mustafa H. AL – Nakib 

Biochemical Engineering Department, AL-Khwarizmi College of Engineering _ University of 

Baghdad _ Iraq 

 

Abstract 

   The present work aims to study the removal of dyes from wastewater by reverse 

osmosis process. Two dyes were used direct blue 6, and direct yellow. Experiments 

were performed with feed concentration (75 – 450 ppm), operation temperature (30 – 

50 
o
C) and time (0.2 – 2.0 hr). The membrane used is thin film composite membrane 

(TFC). It was found that modal permeate concentration decreases with increasing feed 

concentration and time operating, while permeate concentration increases with 

increasing feed temperature. Also it was found that product rate increase with 

increasing temperature, but it decrease with increasing feed concentration and time. 

The concentration of reject solution showed an increase with increasing feed 

concentration of dyes and feed temperature, while decreases with increasing time 

operating of reverse osmosis unit. The maximum rejection for direct blue 6 and direct 

yellow are 98.89% and 98.30% respectively. The maximum recovery percentage for 

direct blue 6 and direct yellow are 17.84% and 18.20% respectively. The maximum 

concentration factor of direct blue 6 is 1.227 and for direct yellow is 1.272. 

 

Keywords: reverse osmosis,    Dyes (direct blue 6, direct yellow), Fouling, 

membranes 

 

Introduction 

   Large amounts of dyes are used for 

various industrial applications; 

especially in the textile industries for 

dyeing cotton Petrinic [1]. The textile 

industry is characterized by using huge 

quantity of water. In fact the 

wastewater from textile dyeing 

industry is ranked the most polluting 

among all industrial sectors when 

considering both volume and 

composition and is classified is non-

toxic although it contains a variable 

chemical composition of organic 

compounds such as synthetic dyes, 

surfactants, emulsifiers, cellulose and 

derivatives, starch, carbamide, nitrols 

and other organic substances 

Chokrabarti [2] and Manoskovn [3]. 

Dyes are mostly stable in light and 

heat. Also application of technologies 

which give more stability in the 

environment against sunlight, bleaches 

and oxidants, should be considered 

Gholami [4] and Bouy [5]. The classic 

and conventional treatment methods 

for these types of effluents are based 

on chemical precipitation, activated 

sludge, chloriation and adsorption of 

activated carbon and membrane 

process Allen [6] Albanis [7] and 

Mohamed [8]. In the recent years, 

Iraqi Journal of Chemical and 

Petroleum Engineering 

 

University of Baghdad 

College of Engineering 



Reverse Osmosis Polyamide Membrane for the Removal of Blue and Yellow Dye from Waste Water 

 

50                                           IJCPE Vol.14 No.2 (June 2013)            -Available online at: www.iasj.net 
 

several factors have led to the 

development of membrane separation 

technology. Membrane process are 

often chosen in water treatment 

technology since these  applications 

achieve high removals of constituents 

such as dissolved solids, organic 

carbon, inorganic ions. Membrane 

processes such as reverse osmosis 

(RO), microfiltration (MF), 

nanofiltration (NF) and ultrafiltration 

(UF) are used around the world for 

potable and ultra-pure water 

production, chemical process 

separations, as well as desalination of 

seawater. Microfiltration and 

ultrafiltration used as pretreatment for 

nanofiltration and reverse osmosis 

processes. Membrane separation 

processes are also used in food and 

diary industries, pharmaceutical and 

cosmetics production, water softening, 

ultra water production for electronic 

industries as well as treatment of 

municipal and industrial wastewater 

and agricultural drainage water. 

Reverse osmosis desalination has the 

advantage from the point of view of 

energy consumption, high product 

quality and flexible design and 

installation Cheryan [9]. 

   The reverse osmosis membrane 

separation process called 

hyperfiltration because it will be 

noticed that reverse osmosis bears 

some resemblance to filtration, in that 

both involve removing a liquid from a 

mixture by passing it through a device 

that holds back other substance Ulrich 

[10]. It is a general and widely 

applicable technique for the separation, 

concentration or fractionation of 

substances in fluid solutions. It 

consists in letting the fluid mixture 

flow under pressure through an 

appropriate porous membrane, and 

with drawing the membrane permeated 

product generally at atmospheric 

pressure and surrounding temperature; 

the product is enriched in one or more 

constituents of the mixture, leaving a 

concentrated solution of other 

constituents on the upstream side of 

the membrane Sourirajan [11]. 

   The choice of membrane material 

directly influences the separation 

efficiency. For obtaining a good 

efficiency, the membrane material 

must have high affinity for the solvent, 

and low affinity for the solute. The 

most common reverse osmosis 

membrane which attained the stage of 

economic application in water 

purification plants are made of 

cellulose acetate (CA) or polyamide 

(PA) Dan [12]. Membrane technology 

can reduce the volume, recover and 

recycle valuable component from the 

waste streams and /or remove recover 

the thermal energy in hot waste water 

Liv [13] and Koyuncu [14]. 

Reverse Osmosis performance can be 

expressed in terms of recovery and 

rejection: 

 

1- Recovery Factor (Y) is defined as 
the fraction of the feed flow that 

passes through the membrane    
 

  
  

  
*100                                   …(1) 

 

Where Qp is the permeate volumetric 

flowrate (m
3
 s

-1
) and Qf is the fead 

stream flowrate, Hasan [15]. 

 

2- Rejection Percentage (R)    
defined as the extent to which a 

solute is rejected by the membrane 
 

    
  

  
                                    …(2) 

 

Where Cp   is the permeate 

concentration [kg/m
3
] and Cf is the 

feed stream concentration [15]. 

 

3- Concentration Factor: 
The concentration factor (CF)   is 

the ratio of concentration of solute 

(dissolved species) in the 



Nada Mustafa H. AL – Nakib 

 

-Available online at: www.iasj.net                   IJCPE Vol.14 No.2 (June 2013)                                    51 
 

concentrate or reject stream to its 

concentration in the feed stream 
 

   
             

      
 
    

  
              …(3) 

 

4- Permeate Flux: The volumetric 
rate of flow through unit membrane. 

 

  
 

   
                                             ...(4)  

 

Where S is area of membrane, v is 

volume of permeate and t is time, 

Hasan [15]. 

Experimental Materials    

Two types of dyes were selected: 

1. Direct yellow 
2. Direct blue 6  
Characteristics of these dyes are 

presented in Table (1). Solution of 

dyes (1000 ppm) were prepared by 

dissolving 1 g of each dye in 1 litter of 

distilled water and then diluted with 

distilled water to the required 

concentration 450, 350, 250, 150, 75 

ppm

 

Table 1, chemical formula and wavelength at extinction measurement of the dyes examined 

Dyes Wave length (nm) Structure Mw 

Direct yellow 430 C30 H26N4Na208S2 680.66 

Direct blue 6 900 C32 H20N6Na4014S4 932.75 
 

Experimental Procedure 

   Reverse osmosis system was 

installed in the University of Baghdad 

– the chemical engineering department 

lab. It consists of a vessel for 

wastewater with dyes which is 

prepared by adding dyes to distilled 

water; also there is a micro filter which 

is used to remove suspended materials, 

if existed, which is considered as a 

protector for the reverse osmosis 

membranes. After the feed water is fed 

into the micro filter as pretreatment 

then introduced to the RO membrane 

which is a spiral-wound module. High 

pressure pump (maximum pressure 

120 psi) used to allow water pass 

through the thin film composite (TFC) 

membrane then into the product 

solution as shown in figure (1). This 

system is based on the concentration of 

dye solution as recycled back to the 

feed vessel to get the highest recovery 

percentage. 
 

 
Fig. 1, Reverse Osmosis Process 



Reverse Osmosis Polyamide Membrane for the Removal of Blue and Yellow Dye from Waste Water 

 

52                                           IJCPE Vol.14 No.2 (June 2013)            -Available online at: www.iasj.net 
 

   Spectrophotometer with suitable 

wave length for each dye as shown in 

table (1) was used to measure the 

product solution, feed solution and 

reject dye solution every 15minutes. 

All experiments were carried out in 

2hours to reach steady state conditions. 

   Water flux was calculated by 

dividing the permeate volumes by the 

membrane area and time (equation 4). 

At the end of the experiment solution 

was drained out and the system was 

washed by distilled water. 
 

Result and Discussion 

Effect of Feed Concentration 

   By increasing   dye feed 

concentration, this appears as a 

decrease of water flux through the 

membrane as shown in Figure 2. As 

the feed concentration increased the 

product rate decreased. According to 

the Equation 1, recovery is a function 

of product rate. The increase of 

product rate will increase the recovery 

for all parameters studied in the present 

work and vice versa. 

   Figure 3 shows the effect of feed 

concentration on permeate 

concentration and reject percentage for 

blue and yellow dyes respectively. The 

figure indicate that the permeate 

concentration increasing when the feed 

concentration increased. The decrease 

of permeate concentration will increase 

the rejection percentage and vice versa 

(Equation 2). The possibility of fouling 

inside the pores of membrane would be 

larger in case of the concentrated 

solution flowing. This fouling could be 

acting in two ways. First blockage a 

number of pore completely or partly, 

so the flow would be decreased, and 

the second decrease the voidage and 

that also would be decreased the 

product rate.  As shown in Figure 4 the  

effect  of  dye  feed concentration on 

concentration of reject and 

concentration factor, the dye 

concentrations increases, the reject 

concentration (or concentrate) will 

increase. The increasing of reject 

concentration will increase the 

concentration factor (Equation 3). 
 

 
Fig. 2, Effect of feed concentration on 

permeate flow (J) and recovery factor (Y %) 

 

 
Fig. 3, Effect of feed concentration on 

permeate concentration (Cp) and rejection 

percentage (R %) 

 

Fig. 4, Effect of feed concentration on reject 

concentration (Cret.) and concentration factor 

(CF) 



Nada Mustafa H. AL – Nakib 

 

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Effect of Operation Temperature 

   The inlet temperature effect on the 

product rate, increasing temperature 

will increase the permeate flux and 

recovery percentage as shown in 

Figure 5.   A change in operating 

temperature will change (i) the 

densities and viscosities of solutions 

which increase the relative flow of the 

pure water through the membrane, (ii) 

by increasing operating temperature, 

solute (dye) flux increase, this appears 

as an increase of solute concentration 

in the product, and the decreasing of 

rejection percentage. This is shown in 

Figure 6. The concentrate behavior is 

shown in Figure 7 as a variation of 

reject concentration and concentration 

factor increases with increasing 

temperature. The increasing of 

temperature means the decreasing of 

the reject flow rate, which led to an 

increase in the reject concentration. 
 

 
Fig. 5,   Effect of operating temperature on 

permeate flow (J) and recovery factor (Y %) 
 

Fig. 6, Effect of operating temperature on 

permeate concentration (Cp) and rejection 

percentage (R %) 

 
Fig. 7, Effect of operating temperature on 

reject concentration (Cret.) and concentration 

factor (CF) 

 
Effect of Operating Time 

   The flow rate from reverse osmosis 

unit decreases with increase in 

operating time. The product rate of a 

reverse osmosis system decrease as 

fouling occurs, because the foulants on 

the membrane surface retard the back 

diffusion of the dye into the bulk 

solution to cause concentration 

polarization at the membrane surface. 

   The increase in concentration 

polarization causes a decrease in the 

product rate that explain the decreasing 

of product rate with increase operating 

time As shown in Figure 8.  The water 

recovery and permeate flux decrease 

with increasing operating time 

according to equations 1 and 4. Figure 

9 shows the influence of operating time 

on rejection percentage. The increases 

in time cause an increase in fouling of 

membrane. This reason can be explain 

the increase dye concentration with 

increase in operating time which 

causes the decrease in rejection 

percentage. 

   Figure 10 shows the effect of 

operating time on concentration of 

reject and concentration factor for 

reverse osmosis unit. During the 

operation, water flux through the 

membrane decreases, for this reason 

the concentration of reject solution 

decrease. So, the reject concentration 



Reverse Osmosis Polyamide Membrane for the Removal of Blue and Yellow Dye from Waste Water 

 

54                                           IJCPE Vol.14 No.2 (June 2013)            -Available online at: www.iasj.net 
 

decreases with time increase. 

Concentration factor decreases 

according to Equation 3. 
 

 
Fig. 8, Effect of operating time on permeate 

flow (J) and recovery factor (Y %) 

 

 
Fig. 9, Effect of operation time on permeate 

concentration (Cp) and rejection percentage  

(R %) 

 

 
Fig. 10, effect of operating time on reject 

concentration (Cret.) and concentration factor 

(CF) 

Conclusion: 

 Reverse osmosis gives a high 
efficiency in separation dyes. The 

product rate in RO increases with 

increasing temperature, but it 

decreases with increasing feed 

concentration and operating time. 

 The increase in operating time, feed 
concentration and feed temperature 

will decrease the rejection 

percentage. The increase in feed 

concentration and operating time 

decrease concentration factor while 

increases in temperature increase it. 

 The maximum recovery of dye 
(direct yellow) is 18.32% and for 

direct blue 6 is 17.84%. The 

maximum rejection of dye (direct 

yellow) is 98.30% and for direct 

blue 6) is 98.89%. The maximum 

concentration factor of direct blue 6 

is 1.227 and for Direct yellow is 

1.272. 
 

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Nada Mustafa H. AL – Nakib 

 

-Available online at: www.iasj.net                   IJCPE Vol.14 No.2 (June 2013)                                    55 
 

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