280 | P a g e
Removal of textile dyes from aqueous solution using fly Ash
Ashima Satija
1, Dr. Mridula Bhatnagar
21Ph.d Student, 2Associate Professor, Environmental Research Lab, P.G. Department of Chemistry, Government Dungar College, Bikaner (India)
ABSTRACT
Fly ash, a waste from the thermal power plant, was investigated as a replacement for the current expensive methods of removing textile dyes (Methylene Blue(MB), Malachite Green (MG), Crystal Violet(CV), Rhodamine –B (RB) and Rosaniline Hydrochloride (RH) from aqueous solutions. Fly ash was collected from a local suratgarh thermal power plant. It was oven dried at 110ºC overnight and sieved to the desired particle size of 75 μm or smaller. The 50 mL plastic conical tubes containing solution and fly ash were shaken at room temperature (27±2ºC). The pH values of solutions were adjusted by addition of HNO3and NaOH. The percentage of colour removed increase with increase with increasing contact time, increasing adsorbent dosage, decreases with adsorbate concentration and varied with dye solution pH. While the removal efficiency decreased with increasing initial concentration, it increased with increasing adsorbent concentration. Optimum contact time for equilibrium to be achieved is found to be 3 hours (except 150 minutes for Malachite Green).
Optimum adsorbent dose for the dye is 1g/50ml (except 1.4g/50ml for Crystal Violet). The maximum percentage removal occurred at lowest concentration (5mg/L). The adsorption capacity of flyash for the five dyes (Methylene Blue, Malachite Green, Crystal Violet, Rhodamine-B and Rosaniline Hydrochloride) increased with temperature. Adsorption of these dyes onto fly ash was favourable sorption. Therefore, fly ash, the low-cost coal waste, is suitable for use as adsorbent.
Keywords : fly ash, adsorption, adsorbent
I. INTRODUCTION
Dyeing and Printing industry is one of the most important and rapidly developing industrial sectors in India. It has a great disadvantage in terms of its environmental impact because it consumes considerably high amount of processed water and produces highly polluted discharge water [1]. Dyeing effluents are of concern because they colour the drains and ultimately the water bodies when let into the surrounding without treatment and thereby affect the quality of water [2]. There are more than 100,000 commercially available dyes with over 7×105 tonnes of dyestuff are produced annually while an annual world production of 30 million tonnes of textile is reported [3].
The conventional wastewater treatments which rely on aerobic biodegradation, have low removal efficiency for reactive and other anionic soluble dyes. However, these processes are very expensive and cannot effectively be used to treat the wide range of dyes waste. Therefore, adsorption processes [4,5], a tertiary treatment, have received consideration for color removal while activated carbon [6], charcoal, aluminia, silica, flyash have been
281 | P a g e used as adsorbents. Coal flyash, which is a by-product of thermal power plants, has long been recede as an industrial pollutant occupying large tracts of land in rural and semi-urban areas. About 60 thermal power plants all over India produce about 30 million tons of flyash per year [7]..
The objective of the present study was to find out the adsorption capacity of the flyash, which is a waste product from thermal power plant:- a low cost adsorbent for the removal of dyes from aqueous solutions so as to facilitate comparison with other adsorbents and provide a sound basis for further modification of the adsorbent to improve its efficiency. The aim for this research is to study the utilization of fly ash as adsorbent for removal of five types of reactive dye:- METHYLENE BLUE (MB), MALACHITE GREEN (MG), CRYSTAL VIOLET (CV), RHODAMINE-B (RB) and ROSANILINE HYDROCHLORIDE (RH). The structures of these dyes are shown in Figures 1 (a), (b),(c),(d) and (e).The experiments were carried out in batches studying the effect of dye concentration, adsorbent concentration, contact time, pH and temperature. The results were validated by Langmuir and Freundlich Isotherm.
(a) (b)
(c) (d)
(e)
Figure 1. The structures of dye Methylene Blue (MB), Malachite Green (MG), Crystal Violet (CV), Rhodamine- B (RB) and Rosanilne Hydrochloride (RH).
II. MATERIALS AND METHODS
2.1 Preparation of adsorbate: Flyash was collected from Suratgarh Thermal Power Plant. Raw Sample was initially sieved from sieve size of 75μm, since the maximum particles was in the range of 30-75μm size as
282 | P a g e analysed by Particle Size Analysis (PSA). Flyash sample was washed thoroughly with double- deionised water (1000 ml),which was then chemical treated using 1M HCl and then oven dried for 12 h at 105ºC in a conventional oven . After treatment sample was stored inside desiccators [8].
2.2 Preparation of adsorbent: The dye solutions were prepared by adding 0.01g of dye into a small amount of deionized water in a 100ml Erlenmeyer flask and filling it to the mark with double distilled water. If 1 g is present in 1 L then solution is said to be 1000 ppm and when 0.01 g of dye is dissolved in 100 ml then it becomes 10 ppm. The flasks were covered with aluminium foil to avoid degradation by the laboratory fluorescent lights. Before the adsorption experiments could be performed, it was necessary to choose the appropriate concentration of dye solutions.
2.3 Equipments: A Hitachi V-500 UV/VIS double beam spectrophotometer was used for dye analysis. The pH measurements were obtained using a digital pH meter CP-901. An environmental orbital shaker was used for all adsorption experiments.
2.4 Adsorption of dyes on Flyash: Batch mode adsorption studies for individual dyes were carried out to investigate the effect of different parameters such as adsorbate concentration, adsorbent dose, agitation time, temperature and pH [9]. Solution containing adsorbate and adsorbent was taken in 250 mL capacity beakers and agitated at 150 rpm in a mechanical shaker at predetermined time intervals. The adsorbate was decanted and separated from the adsorbent using Whatman No.1 filter paper. To avoid the adsorption of adsorbate on the container walls, the containers were pretreated with the respective adsorbate for 24 hours.
2.4.1 Experiment 1: 50 ml of dye solution with dye concentration 5 mg/L for all dyes is to be pipette in a conical flask along with known amount of adsorbate (flyash) was kept inside the shaker. The dye concentration was measured after an interval of 15 minutes for all the dyes until equilibrium reaches. A graph is to be plotted with % Removal vs Contact Time after calculating the value of Qe.
% 𝑅𝑒𝑚𝑜𝑣𝑎𝑙 =𝐶𝑜−𝐶𝑒𝐶𝑜 ∗ 100 Eq. 1 Where,
Co = intial concentration of the dye(mg/l) Ce = equilibrium concentration of the dye(mg/l) V = volume of the dye solution(l)
m = weight of the adsorbent(g)
2.4.2 Experiment:. 50ml of dye solution was pipette out in different conical flask with dye concentration of 5mg/L along with adsorbate (flyash) was kept inside the shaker. The flyash concentration considered for the adsorbance was 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4 and 1.6 gm. A plot of % Removal vs Adsorbent Dose is taken as in Eq. 1.
2.4.3 Experiment 3: 50 ml of dye solution was pipette out in a Erlenmeyer flask along with adsorbate (flyash) was kept inside the shaker. The dye concentration selected for different dyes are 5mg/L, 7.5 mg/L, 10 mg/L, 12.5 mg/L and 15 mg/L. A plot of % Removal vs Adsorbent Dose is taken as in Eq. 1.
283 | P a g e 2.4.4 Experiment 4: 50 ml of dye solution with dye concentration 5mg/L is to be pipette in conical flask along with adsorbate (flyash) was kept inside the shaker. The dye concentration was measured at pH 4, 5, 6, 7, 8 for all the dyes. A plot of % Removal vs Adsorbent Dose is taken as in Eq. 1.
2.4.5 Experiment 5: 50 ml of dye solution with dye concentration 5mg/L is to be pipette in Erlenmeyer flask along with adsorbate (flyash) was put inside the incubator shaker. The pH, equilibrium time and the adsorbent dosage was kept constant, which varied according to the study undertaken for different dyes. The final dye concentration readings were taken at 10 oC, 20 oC, 30 oC, 40 oC, 50 oC. A plot of % Removal vs Adsorbent Dose is taken as in Eq. 1.
III. RESULT AND DISCUSSION
3.1 Effect of Contact Time: Figure 1 presents the results for the effect of contact time on the removal of Methylene Blue, Malachite Green, Crystal Violet, Rhodamine -B and Rosaniline Hydrochloride at an initial concentration of 5 mg/L. The graphs are single and smooth, indicating monolayer coverage of the adsorbent surface by the dye. It is clear that the extent of adsorption is rapid in the initial stages and becomes slow in later stages till saturation is allowed. The final dye concentration did not vary significantly after 180 min for all dyes except 150 min for malachite green from the start of adsorption process.
Figure 1. Effect of Contact Time on adsorption of Methylene Blue, Malachite Green, Crystal Violet, Rhodamine-B and Rosaniline Hydrochloride.(Initial dye concentration 5mg/L, pH = natural of pH of individual dye, Room Temperature (300C), Agitation Speed 150 rpm.)
3.2 Effect of Adsorbent Amount: From Figure 2 we see that the optimum dose for the Methylene Blue, Rhodamine –B and Rosaniline Hydrochloride is 1g/50ml, Malachite Green and Crystal Violet is 1.4g/50ml. As seen in the Figure with the increase in adsorbent amount the % Removal decreases. This implies that the number of adsorption sites in the samples with m= 1g (and 1.5 g for Malachite Green) is sufficient for the complete adsorption of dyes. In experiments with m > 1g (and 1.5g for Malachite Green) no expected increase in adsorption of dyes was observed. Evidently, in these experiments the content of dyes in the solid and liquid phases achieved equilibrium concentrations [10].
0 10 20 30 40 50 60 70 80 90 100
0 50 100 150 200 250 300 350
% Removal
Contact Time(minutes)
MB MG CV RB RH
284 | P a g e
Figure 2 Effect of Adsorbent Amount on adsorption of Methylene Blue, Malachite Green, Crystal Violet, Rhodamine-B and Rosaniline Hydrochloride.(Initial dye concentration 5mg/L,
pH = natural of pH of individual dye, Room Temperature (30
0C), Agitation Speed 150 rpm.)
3.3 Effect of Adsorbate Concentration: Percentage removal of Methylene Blue, Malachite Green, CrystalViolet, Rhodamine -B and Rosaniline Hydrochloride decreased from 87.26 to 82.22 %, 74.18 to 67.27%, 91.07 to 81.76 %, 91.16 to 76.89 % and 71.94 to 59.86% respectively with increase in concentration as shown in Figure 3. the removal percentage decreases and the extent of adsorption increase with increasing initial dye concentration. This is obvious from the fact that the initial dye concentration provides an important driving force to overcome all of mass transfer resistance. It is because of that at lower concentration, the ratio of the initial number of dye molecules to the available surface area is low subsequently the fractional adsorption becomes independent of initial concentration[11]. However, at high concentration the available sites of adsorption becomes fewer and hence the percentage removal of dye is dependent upon initial concentration [12].
Figure 3 Effect of Adsorbate Concentration on adsorption of Methylene Blue, Malachite Green, Crystal Violet, Rhodamine-B and Rosaniline Hydrochloride. (pH = natural of pH of individual
dye, Room Temperature (30
0C), Agitation Speed 150 rpm.)
40.0050.00 60.00 70.00 80.00 90.00 100.00
0 0.5 1 1.5 2
% Removal
Flyash Amount (g/50ml)
MB MG CV RB RH
40.00 50.00 60.00 70.00 80.00 90.00 100.00
0 5 10 15 20
% Removal
Dye Concentration (mg/L)
MB MG CV RB RH
285 | P a g e 3.4 Effect of pH: The effects of initial pH on dye solution of five dyes removal were investigated by varying the pH from 4 to 8 are shown in Fig 4. Methylene Blue showed maximum removal at pH 6 and for Malachite Green at pH = 5 . In case of Crystal Violet higher the pH, greater was removal by adsorption and was maximum at 7 and become constant after that .For Rhodamine –B there is no significant increase in amount adsorbed after pH 6 whereas for Rosaniline Hydrochloride after pH 5 the adsorption become constant. In the present study the pH was maintained at 7, since the dyes showed the maximum adsorbance at pH 5 to pH 7. Infact adsorption found to decrease with increase in pH of solution. The adsorption of these positively charged dye groups on the adsorbent surface is primarily influenced by the surface charge on the adsorbent which in turn is influenced by the solution pH. The result showed that availability of negatively charged groups at the adsorbent surface is necessary for the adsorption of basic dyes to proceed which we see at pH -4 is almost unlikely as there is a net positive charge in the adsorption system due to the presence of H30+ . Thereafter, it should be negatively charged. Thus as the pH increased, more negatively charged surface was available thus facilitating greater dye removal.
Figure 4 Effect of Intial pH on adsorption of Methylene Blue, Malachite Green, Crystal Violet, Rhodamine-B and Rosaniline Hydrochloride. (Initial dye concentration 5mg/L, Room
Temperature (30
0C), Agitation Speed 150 rpm.)
3.4 Effect of Temperature: Temperature has important effects on the adsorption process. With the increase in temperature, rate of diffusion of adsorbate molecules across the external boundary layer and internal pores of the adsorbent particle increases [13]. Changing the temperature will change the equilibrium capacity of the adsorbent for particular adsorbate [14]. The effect of temperature on adsorption of dye solution with initial concentration of 5mg/L at temperatures 10oC, 20 oC, 30 oC, 40 oC, 50 oC on has been determined. The result of studies for the adsorption of the five dyes reveals that the percentage removal of Methylene Blue, Malachite Green, Crystal Violet, Rhodamine - B and Rosaniline Hydrochloride at different temperature increased from 77.69% - 89.14%, 67.24% - 79.28%, 79.52% - 92.52%, 77.30% - 91.91% and 59.42% - 79.63% as shown in the Figure 5 below.
40.00 50.00 60.00 70.00 80.00 90.00 100.00
3 4 5 6 7 8 9
% Removal
pH
MB MG CV RB RH
286 | P a g e
Figure 5 Effect of Temperature on adsorption of Methylene Blue, Malachite Green, Crystal Violet, Rhodamine-B and Rosaniline Hydrochloride. (Initial dye concentration 5mg/L, pH =
natural of pH of individual dye, Agitation Speed 150 rpm.)
REFRENCES
[1.] D. Singh , V. Singh and A. K. Agnihotri, Study of textile effluent in and around Ludhiana district in Punjab, India, International Journal of Environmental Sciences, 3(4), 2013, 1271-1278.
[2.] A. Dae-Hee, C. Won-Seok and Y. Tai-Il , Dyestuff wastewater treatment using chemical oxidation, physical adsorption and fixed bed bio film process, Process Biochemistry, 34,1999, 429–439.
[3.] R. Abraham, Dyes Environmental Chemistry: Encyclopaedia of Chemical Technology, Wiley, NY., 8, 1993, 672-783.
[4.] T. Robinson , G. McMullan , R. Marchant and P. Nigam , Remediation of dyes in textile effluent: A critical review on current treatment technologies with a proposed alternative, Bioresource Technol, 77, 2001, 247-255.
[5.] M.M. Kamel , M. Magada, B. M. Kamel and A. Youssef , Adsorption of Direct Dyes By cellulose derivatives, Am Dye Rep,34-50, 1999.
[6.] G. M. Walker and L. R. Weatherley , Adsorption of Acid Dyes on to Granular Activated Carbon in Fixed Beds, Wayer Res.,31(8), 1997, 2093.
[7.] V. Kumar , Management of flyash in India: A Perspective, 3rd International Conference- Flyash Utilization and Disposal, 19-21 Februrary 2003, New Delhi, India.
[8.] S. Oluwaseyi Bada and S. Potgieter - Vermaak, Evaluation and treatment of coal flyash for adsorption application, Leonardo Electronic Journals of Practices and Technologies, 12, 2008, 37-48.
[9.] N. Sarier , Specific features of adsorption of azo dyes on flyash, Russian Chemical Bulletin, 56 (3), 2007, 566-569.
50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 95.00
0 10 20 30 40 50 60
% Removal
Temperature (0C)
MB MG CV RB RH
287 | P a g e [10.] S. Arivoli , M. Thnkuzali and P. Martin Deva Prasath , Adsorption of Rhodamine –B by acid activated
carbon – kinetic, thermodynamic and equilibrium studies, Orbital, 1(2), 2009, 138-155.
[11.] C. Namasivayam, and R.T. Yamuna, Removal of Rhodamine B by biogas waste slurry from aqueous solution, Water, Air and Soil Pollution, 65, 1992, 101-109.
[12.] P. Waranusantigul , P. Pokethitiyook , M. Kruatrachue and E.S. Upatham , Kinetics of basic dye (methylene blue) biosorption by giant duckweed (spirodela polyrrhiza), Environmental Pollution, 25, 2003, 385-392.
[13.] M. Otero , F. Rozada , L.F. Calvo , A. I. Garcia and A. Moran , Kinetic and equilibrium modeling of Methylene Blue removal from solution by adsorbent materials produced from sewage sludges, Biochemical Engineering Journal, 15, 2003, 59-68.
[14.] T. Shahwan and H. N. Erten , Thermodynamic parameters of Cs+ sorption on natural clays, Journal of Radio analytical and Nuclear Chemistry, 253 (1), 2002, 115-120.
