Journal of Earth Sciences & Environmental Studies

ISSN: 2472-6397

Impact Factor: 0.865


Removal of Disperse Dyes Using Different Coagulants from Wastewater of Textile Industries


Muhammad Usman, Tokyo Institute of Technology, Japan

Prof Jeffrey S Cross, Tokyo Institute of Technology, Japan

Hafiz Muhammad Aamir, University of Gujrat, pakistan


Muhammad Usman, Removal of Disperse Dyes Using Different Coagulants from Wastewater of Textile Industries(2019)SDRP Journal of Earth Sciences & Environmental Studies 4(3)


Water contamination is a noteworthy subject of enthusiasm for the Ecologist and researchers nowadays. One of the Process industries that has been discovered responsible of obliterating the nature's blessing to humankind, water, is Textile industry. Researching further, demonstrates that it is the coloring procedure of this industry that is the real guilty party. Substantial amounts of water are spent in this procedure and this creates a major mass of waste water with high turbidity brought about by Dyes. In this examination venture evacuation of scatter colors, utilized for polyesters, has been contemplated utilizing Coagulants. The coagulants contemplated were Ferric Sulphate, Ferrous Sulphate and Alum. All these are shabby. The components that have been considered up here are the impacts of dose and coagulant type on expulsion of Ciba Blue scatter color. For the testing reason container tests were utilized and for investigation of clear water spectrophotometer was utilized. The outcomes were empowering for Alum and Ferric Sulphate, yet this was not so because of Ferrous Sulphate.

Keywords: Disperse Dyes, Decolourization, Coagulants, Flocculation, Wastewater, Water Effluents


The utilization of synthetic organic dyes in different modern procedures, including paper and pulp fabricating, plastics, coloring of material, calfskin treatment and printing has expanded significantly in the course of the most recent couple of years, bringing about the arrival of color containing mechanical effluents into the dirt and oceanic biological communities [1]. Since the greater part of these colors are poisonous in nature, their quality in mechanical effluents is of major ecological concern since they are generally extremely hard-headed to microbial debasement [2]. Now and again, the color arrangement can likewise experience anaerobic corruption to shape possibly cancer-causing aggravates that can finish up in the natural way of life [3]. Additionally, profoundly hued wastewaters can hinder the entrance of daylight and oxygen, basic for the survival of different amphibian structures [4] Textile businesses use considerable volumes of water and synthetic substances for wet-handling of materials. These synthetic substances, going from inorganic mixes and components to polymers and natural items are utilized for wanting, scouring, fading, coloring, printing, and completing [5]. There are in excess of 8,000 substance items related with the coloring procedure recorded in the Color Index, including a few auxiliary assortments of colors, for example, acidic, receptive, essential, scatter, azo, diazo, anthraquinone based and metal-complex colors [3]. The expulsion of shading from wastewaters is frequently more essential than the evacuation of the solvent dull natural substances, which for the most part add to the significant portion of the biochemical oxygen request (BOD). Strategies for the expulsion of BOD from most effluents are genuinely entrenched; colors, nonetheless, are increasingly hard to treat on the grounds that their engineered cause are basically mind boggling sweet-smelling sub-atomic structures, frequently orchestrated to oppose blurring on introduction to sweat, cleanser, water, lighter oxidizing specialists [1,6]. This renders them increasingly steady and less amiable to biodegradation [7,8]. Numerous methodologies, including physical or potentially compound procedures, have been utilized in the treatment of mechanical wastewater containing color however such strategies are regularly in all respects exorbitant and not earth safe [9,10]. Techniques using powdered initiated carbon and actuated bentonites have been usually utilized [11,12]. Not with standing, the expansive measure of ooze created and the low productivity of treatment as for certain colors have restricted their utilization [13]. Shading evacuation utilizing ozone is additionally typically viable and quick, however not every one of the techniques utilized give tasteful outcomes particularly for some scattered colors [1]. Another generally used treatment technique for hued effluents is the physical-concoction flocculation with metal hydroxides helped by polymer flocculants [14], while the utilization of pre-blended polyelectrolyte edifices made by the cooperation of fluid arrangements of polycation and polyanionic acknowledged as an increasingly useful strategy [15]. Such perplexing particles can tie scatter colors viably over expansive separations because of their size and structure by means of hydrophobic just as electrostatic cooperation powers [16]. Notwithstanding, because color atoms or their totals are especially littler than such inorganic particles, and now and again additionally uncharged, it is important to apply other flocculation standards.

Enthusiasm for the contamination capability of material colors has been principally provoked by worry over their conceivable lethality and cancer-causing nature. This is for the most part on the grounds that numerous colors are produced using referred to cancer-causing agents, for example, benzidine and other sweet-smelling intensifies, which might all be changed due to microbial digestion [6]. It has likewise been appeared azo-and nitro-mixes are decreased in residue [17] and in the intestinal condition [18], bringing about the recovery of the parent lethal amines. Some scatter colors have likewise been appeared to bio-aggregate [19], while overwhelming metal particles from material effluents have additionally been accounted for at high focuses in both green growth and higher plants presented to such effluents [20]. As of late, ventures have been looked with increasingly stringent emanating treatment guidelines and are required to bring down the shading content in their wastewater before release into the surface water [21]. This implies for most material businesses, creating nearby or in-plant offices to treat their very own effluents before release is quick moving toward reality. New flocculation components are in this way drawing in more consideration [22]. The expulsion of colors from wastewater exhibits a considerable test, as most colors are totally solvent in fluid arrangements [23]. Even though colors establish just a little bit of the all-out volume of waste release in material preparing, these mixes are not promptly expelled by common microbial based squander treatment forms [24]. In this study, the goal of this investigation was to assess the capacity of the Different Coagulants and Flocculation, to expel colors from material mechanical effluents.


Coagulation is the procedure by which colloidal units and exceptionally fine strong interruptions at first existing in a wastewater are consolidated into bigger agglomerates that can be isolated by means of sedimentation, flocculation, filtration, centrifugation or other detachment techniques. Coagulation is ordinarily accomplished by including diverse kinds of synthetic concoctions (coagulants) to the wastewater to advance destabilization (expulsion of charge) of the colloid scattering and agglomeration of the subsequent separate colloidal atoms. The expansion of some normal coagulants to a wastewater produces coagulation of colloids as well as regularly results in the precipitation of dis solvable mixes, for example, phosphates, that can be available in the wastewater[25].

Moreover, coagulation can likewise create the expulsion of particles bigger that colloidal particles because of the capture of such particles in the flocs shaped amid coagulation.

Effects of Coagulation Treatment on Wastewater

Primary Effect

Secondary Effects

Agglomeration and inevitable evacuation of colloids (basically in charge of wastewater turbidity)

Precipitation of approximately concoction species in arrangement. Agglomeration of bigger particles in the floc



A procedure of contact and bond whereby the destabilized particles present in scattering after expansion of coagulants structure bigger size bunches and afterward settle down whereby they could be evacuated or handled further. In this procedure a solute leaves arrangement as Floc or Flakes. This system is unique in relation to precipitation in this angle the solute leaving arrangement does as such at a focus by and large underneath its solvency limit in the fluid or the solute turning out structure a suspension does as such at a much fast rate. In the event that a specific change in grouping of a suspension without flocculation takes 2 or 3 days utilizing this system the equivalent or far better outcome could be accomplished in 8 to 16 hours[25].

After flocculation process has been completed the finished result is water (clear alcohol) and flocs. Amid this procedure the greater part of the turbidity is gathered into flocs that are shaped when pollutions meet up and structure a bunch. The floc will at that point settle out in the sedimentation bowl, with residual floc being evacuated in the channel. The best floc estimate is 0.1 to 3 mm. Bigger floc is progressively subject to separation in the flocculation bowl and littler floc may not settle. The common pollutants present in waste water are[25,26]:

  1. Organic materials
  2. Metal oxides
  3. Insoluble toxic compounds
  4. Stable emulsions
  5. Material producing turbidity (colored substances like dye)

Coagulation vs. Flocculation



demonstrates the procedure concluded which colloidal particles and exceptionally fine strong suspensions are destabilized so they can start to agglomerate if the circumstances are fitting.

alludes to the procedure by which subverted particles combination into bigger totals with the goal that they can be isolated from the wastewater.

Effects of Flocculation on Sedimentation

The inquiry emerges for what reason do we need such a mind-boggling procedure to expel particles from water? A few particles would settle out of the water alone, given enough time. Be that as it may, different particles would oppose agreeing to days or months because of little molecule estimate and to electrical charges between the particles. In this report substance process utilizing regular flocculants that can help settling is considered. Particles present in water can be one of the three blend types.

  1. Solutions

  2. Colloidal solutions

  3. Suspensions

Flocculation is not effective for particles present in form of solution.

Figure 1: Properties of Mixtures

Action of Coagulants & Flocculants

The science of coagulation and flocculation is principally founded on power; power is the conduct of negative and decidedly charged particles because of their fascination and shock. Same (like) charges repulse one another while inverse (not at all like) charges draw in figure 2.

Figure 2: Negatively charged particles repel each other

Figure 3: Attraction of positively charged coagulants & negatively charged particles

Most particles broke down in water have a negative charge, so they will in general repulse one another. Accordingly, they remain scattered and broke down or colloidal in the water, as indicated above.The motivation behind most coagulant synthetics is to kill the negative charges on the turbidity particles and thus keep those particles from repulsing one another. The measure of coagulant which ought to be added to the water will rely upon the zeta potential, an estimation of the greatness of electrical charge encompassing the colloidal particles. On the off chance that the zeta potential is expansive, at that point higher measurements of coagulants will be required. Coagulants will in general be emphatically charged. Because of their positive charge, they are pulled in to the negative units in the water, as appeared above figure 3. The blend of positive and negative charge outcomes in an impartial, or need, of charge. Subsequently, the particles never again repulse one another[25,26,27].

The following power which will influence the particles is known as van der Waal's powers. Van der Waal's powers allude to the inclination of particles in nature to draw in one another feebly in the event that they have no charge, figure 4.

Figure 4: Van der Waal attraction between neutral particles

Figure 5: Particles and coagulants join into floc.

When the particles in water are not repulsing one another, van der Waal's powers make the particles float toward one another and join into a gathering, figure 5. At the point when enough particles have consolidated, they progress toward becoming floc and will settle out of the water. Also, huge numbers of the flocculants, under fitting pH and different conditions, for example, temperature and saltiness, respond with water to frame insoluble hydroxides which, after accelerating, connect to shape long chains or networks, physically catching little particles into the bigger floc [25,26]

Mechanisms of Coagulation

There are two mechanisms which we have discussed below in table.

Peri kinetic flocculation

Orthokinetic flocculation

This type of flocculation is produced by the Brownian movement related with destabilized little colloidal particles. The Brownian movement adds to passage the particles nearby enough for agglomeration to happen.

This sort of flocculation system depends on the age of speed angles inside the wastewater to advance molecule association. For this situation a mellow fomentation advances the accumulation of the particles and subsequently flocculation.


Any shaded compound isn't a Dye or Dyestuff. A color is a shaded natural aggravate that assimilates light unequivocally in the noticeable locale and can immovably connect to the fiber by concoction and physical holding between gathering of the color and gathering on the fiber. To be of business significance a color ought to be quick to light, scouring and water. Colors might be arranged in two different ways. The natural scientist characterizes them as indicated by a typical parent structure, Synthetic Classification. The dyer, who is just keen on fixing the color to the fiber, arranges them as indicated by the Method of Application[27,28].

Classification according to chemical structure

Figure 6: Nitro Dyes

Figure 7: Azo Dyes (-N=N-)

Figure 8: Diphenylmethane Dyes

Figure 9: Triphenylmethane Dyes

Figure 10: Xanthene D

Figure 11: Indigoid and Thioindigoid Dyes

Why removal of Dyes is necessary?

In recent years textile industry has grown very much. Subsequently, the contamination brought about by material industry has additionally gone feed wire. A standout amongst the most vital and significant utility of material industry is water. This water is utilized for biting the dust, handling of fiber, washing and so forth thus there are a few polluting influences in the waste water. In coloring and completing procedures in the material businesses, significant measure of wastewater is created, and its organization differs in qualities. The organization of material modern wastewater relies upon mechanical activities, sorts of colors and crude materials being utilized. In the material ventures, diverse sorts of colors are utilized in a solitary day in coloring process. Along these lines, the wastewater produced likewise contains a blend of various kind of colors, in obscure and multifaceted nature in their concoction structure, which makes the material waste effluents hard to treat palatably. At the point when there is more than one color in an answer, it can't be anticipated the consequence of the treatment of colors. Being compound substances separating in water, the colors can respond artificially among themselves and giving another color. The decolorization is influenced by various sort of color structure. Changes of the pH of wastewater because of colors changes likewise make the wastewater hard to treat as the pH resistance of ordinary organic and concoction treatment frameworks is constrained[28,29,30].

The wastewater treatment is an imperative subject in contamination control because the dyestuffs are not just exceedingly organized polymer that are hard to break down naturally, it likewise comprises mix of solid shading and high disintegrated strong substance which lead to high turbidity of waste gushing. The high turbidity of the waste emanating likewise genuinely influences the photosynthetic movement of oceanic plants and makes aggravation the natural framework. Significant toxins of material mechanical wastewater incorporate high suspended solids (SS), synthetic oxygen request (COD), biochemical oxygen request (BOD), shading, causticity, basicity and other dissolvable substances. All contaminations except for shading can be diminished successfully by general concoction and physical techniques. Consequently, the principle issue of material enterprises wastewater is the shading which, is delivered by the leftover colors amid coloring and completing procedures. Moreover, the substance structure of engineered natural shades in colors makes them impervious to breakdown. Shading expulsion of material effluents has been giving incredible consideration as of late due to its poisonous quality and perceivability issues[28,29,30].


The experimental procedure to test and cure the waste water is known as jar testing. In the following text jar testing and its related procedures will be discussed in detail. Jar testing is the most common laboratory coagulation test. It consists of the following steps

  • Insertion a sample of the wastewater in a jar.
  • Swiftly adding the coagulant and deeply mixing the sample for a short time (coag (coagulation/destabilization phase).
  • Letting the floc to form below gentle mixing circumstances (flocculation phase).
  • Consenting the floc to residue in the dormant sample (settling).
  • Associating the turbidity of the sample with the initial turbidity.

Jar test apparatus

Jar test apparatus is relatively very simple. No high-tech instruments or equipment’s are needed. Only high-tech equipment required is for the analysis of the sample from jar testing. The apparatus is

  • Beakers
  • Pipette
  • Stirrer
  • Analytical balance
  • Stop watch
  • Spectrophotometer

During the experimentation two variables were studied

  • Dosage
  • Type of Coagulant

Care was taken that all other variables like mixing time, stirrer RPM, settling time and pH remain constant[7,8].

Chemicals used

  • Ciba blue dye 83962
  • Alum
  • Ferrous sulphate
  • Ferric sulphate

Experimental Procedure

Preparation of Sample

 As the purpose of this project was to study the removal of disperse dyes so instead of taking sample directly from a textile industry’s waste water, that will contain other pollutants as well, sample of disperse dye was prepared in the laboratory. It was prepared using Ciba Blue 83962 dye and its concentration was 500ppm. Tap water instead of distilled water was used to make the suspension because its pH value is in basic range. The sample was reserved enclosed at all time to avoid dirt scums. Furthermore, to get even concentration for each test sample was stimulated for 1 min automatically before carrying out the testing measures.

Coagulant Preparation

1% stock solutions of the coagulants were made. Alum is very soluble in water so it did not precipitate out after the solution was formed but the other two coagulants, that is, Ferrous Sulphate and Ferric Sulphate did precipitate out, therefore, before using them they were stirred to get the standardized, unvarying and homogenized concentration.

Jar Test

A conventional jar test apparatus was used in the experiments to coagulate 100ml of dye sample. It was carried out as a batch process. A total of eighteen, 100ml dye samples were tested using the three different coagulants. Each coagulant was used to produce flocs from 6 samples. The concentrations of stock solutions used were from 1ml to 6ml with an increment of 1ml of stock solution each time. After adding of coagulant each sample was stirred mechanically in an unbaffled bowl for 30 minutes at constant rpm using radially mixing steel propeller. After the mixing samples were left for settling of flocs for 24hrs.

 After 24hr period was passed clear water samples were taken from top of each beaker with care that none of the settled flocs were disturbed. This was done using pipette.

Stirring Machine

Figure 12: Experimental Setup

Analytical Analysis

To analyse the effects of the above procedure the dye sample of 500ppm, prepared initially was tested in a U.V. spectrophotometer. Furthermore, additional dye samples ranging from 50ppm to 450ppm with an increment of 50ppm were made in tap water to plot a calibration curve. This was done to find out the residual concentration of dye after coagulation or in simpler terms to check the effectiveness of each coagulant dose. After calibration was done the clearer samples were also tested using the same apparatus and absorbance values for a wavelength were noted.

Effect of type of coagulant

The effect of type of coagulant on floc formation was very straight forward and in accordance with the theoretical predictions and data quoted above in articles dealing with action of Aluminium and Iron salt base coagulants. The trend shown by all three of the coagulants is same. Initially, as quoted earlier for lower concentration of coagulants, there is little or no removal of dye. This effect is very prominent in case of Ferrous Sulphate. This can easily be attributed to less alkalinity of water because of which high dose of coagulant was needed to form the hydroxide which causes the flocculation.

The residual concentration curves of treated dye samples also show the same trend. Alum being the most effective of the three followed by ferric and then ferrous sulphates respectively.

Effect of Dosage

The second effect studied, was the effect of dosage on floc formation. For a coagulant there is a minimum threshold of concentration required for effective coagulation to start. The lower this threshold the more effective would be the coagulant. Once that threshold concentration of coagulant has been introduced there is no practical advantage of adding more coagulant. One interesting fact that could be seen in the graphs below is that instead of a continuous downwards trend in residual concentration curve, the curves go upwards which means that instead of cleaning the water coagulants make the water more impure. This is because of the minimum threshold concentration. If the concentration of coagulant is less than that prerequisite amount, then there is no floc formation and as an adverse effect the coagulant particles also get suspended in the water thus increasing its turbidity which is pointed by the graphs.

Figure 13: Calibration Curve


Table 1: Observations

Dosage (ml)

Absorbance (670.79nm)



Ferric Sulphate

Ferrous Sulphate

























Figure 14: Effect of Alum Dosage on Absorbance

Figure 15: Effect of Alum Dosage on Residual Dye Concentration

Figure 16: Change in sample color with increase in alum dosage from left to right

Figure 17: Effect of Ferric Sulphate dosage on Absorbance

Figure 18: Effect of dosage of Ferric Sulphate on Residual Dye Concentration

Figure 19: Change of Sample color with increase in concentration of Ferric Sulphate from left to right.

Figure 20: Effect of Ferrous Sulphate Dosage on Absorbance

Figure 21: Effect of Dosage of Ferrous Sulphate on Residual Dye Concentration

Figure 22: Change of Sample color with increase in Concentration of Ferrous Sulphate from left to right.

Figure 23: Comparison between The three Coagulants used


Conclusions & Recommendations

The results show that alum is the best of three coagulants used. Its required concentration for effective removal of dye is less than the other two. But the high effectiveness of alum comes with big baggage. Alum has been found to cause Alzheimer’s disease. Though it is cheap and effective, but this kind of risk cannot be taken in treatment of water, which eventually reaches humans through marine and plant life.

To overcome this negative effect of Alum we suggest the use of Ferric Sulphate. It is also not very expensive; its effectiveness is feasible for industrial process and there are no proven health hazards yet.

Future Research Recommendations

For future researchers, we recommend them to work on another coagulant called, Chitosan. Its effectiveness is better than as it needs much less residence (settling) time than alum and it is free from medical hazards.

Moreover, we recommend studying the variables like pH, mixing time, RPM of stirrer and settling time. Another important aspect to check in future could be the change in COD of the waste water after treatment. In modern days this has become very important variable to characterize water, so attention should be given to it[31,32].


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