Adsorption of Phenol from Wastewater in Fluidized ... - ScienceDirect

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Procedia Engineering 51 (2013) 300 – 307

Chemical, Civil and Mechanical Engineering Tracks of 3rd Nirma University International Conference (NUiCONE 2012)

Adsorption of Phenol from Wastewater in Fluidized Bed Using Coconut Shell Activated Carbon Sunil J.Kulkarnia* ,Ravi W.Tapre b,Suhas V. Patilc, Mukesh B. Sawarkard a,b

Assistant Professor,Department of Chemical Engineering, Datta Meghe College of Engineering ,Airoli, Navi Mumbai,India, Pincode:402107 c Associate Professor, Gharda Institute of Technology,Lavel,Chiplun ,India,Pincode:415708 d Lecturer,Government Polytechnic,Mumbra, Thane,Maharashtra Pincode:400612

Abstract Phenol is the major pollutants in the wastewater from various industries such as coal conversion process, fertilizers, petroleum refineries, coking plants, pharmaceutical, dye manufacturing etc. In the present study coconut shell activated carbon is used as an adsorbent. The adsorption is carried out in a fluidized bed. Coconut shell has been used for the preparation of absorbent. The effect of various parameters like concentration, fluid flow rate and adsorbent particle size has been studied. It is observed that as the concentration increases the percent saturation of adsorbent increases. Also increase in fluid flow rate gives better adsorption in case of coconut shell activated carbon. However, it is also observed that percent saturation of adsorption decreases with increases in particle size of adsorbent. In the present study particle size of 0.420 mm is found more beneficial. Keywords: Fluidized bed, activated carbon, adsorption, adsordate, isotherms

1. Introduction The phenolic pollution is commonly observed in the chemical and pharmaceutical industries like petrochemical industries, petroleum refineries, coal gasification operations, liquefaction process, resin manufacturing industries, dye synthesis units, pulp and paper mills and pharmaceutical industries. It is a highly corrosive and nerve poisoning agent. When these pollutants contaminate the groundwater, rivers and reservoirs, which are sources for human consumption, harmful side effects, such as sour mouth, diarrhea, excretion of dark urine and impaired vision are seen. The toxic levels usually range between the concentrations of 10-24 mg/l for human and the toxicity level for fish is between 9-25 mg/l. Lethal blood concentration of phenol is around 150 mg/100 ml. Environmental Protection Agency, EPA has set a limit of 0.1mg/lit of phenol in waste water, while that in drinking water is 0.002 mg/lit. A total dose of 1.5 gms may be fatal. The specific tolerance limits (for effluent discharged with inland surface water) for phenolic compounds is 5 mg/litre.As phenol is highly harmful compound, there is a necessity for its removal in order to preserve the environmental quality. Recent studies have shown that biotic and abiotic processes can degrade phenol. Phenol removal by resin has been tried by Gopalkrishnamoorthy and Shanmugam [1]. Abiotic and non– biological processes include adsorption, photodecomposition, volatilization, coupling to soil humus and thermal degradation. In biotic processes both aerobic and anaerobic processes have been employed for its removal. The _____ * Tel.: 919833497367; fax: 91 22 2779 1665. E-mail address: [email protected]

1877-7058 © 2013 The Authors. Published by Elsevier Ltd. Open access under CC BY-NC-ND license. Selection and peer-review under responsibility of Institute of Technology, Nirma University, Ahmedabad. doi:10.1016/j.proeng.2013.01.040

Sunil J.Kulkarni et. al / Procedia Engineering 51 (2013) 300 – 307

study of biokinetic parameters for activated sludge treatment for phenolic water has been carried out by Pandey and Kaul [2]. Kaushik Nath has studied the biological methods for phenol in wastewater [3]. Babu et. al. have used various new adsorbents for phenol removal[4]. Electrochemical chlorination has also been tried by Nanjundam et al.[5]. The work on new adsorbent from coconut husk has been carried out by Krishna and Yenkee[6]. The activated carbon adsorption has also been used for coke effluents by Prasad and Singh[7]. The principle of adsorption, types of adsorption and its the isotherms are described by Treybal[8]. A batch study for phenol adsorption using leaf litter has been carried out by Mishra and Bhattacharya [9]. Besselievne and Schwartz have explained the treatment of industrial waste discharge [10]. The information regarding source, analysis and characteristics of waste is descrided by Manivatsam[11]. The treatment of phenolic wastewater in a multistage bubble column adsorber has been tried by Kumar et.al.[12]. The amount of material adsorbed by activated carbon is surprisingly as large as compare to other carbon. Coony and Zhenpeng[13] have studied activated carbon catalized reaction of phenolics during liquid phase adsorption. Kumar et al.[14] have studied the characterization of activated carbon prepared from coconut shell wood for wastewater treatment. Similar work has been carried out by other researcher’s usig different sources for activated carbon. Activated carbon as an adsorbent is described by John [15]. The coconut shell activated carbon has been tried by many researchers for removal of chromium and other heavy metals with resonable success. In current investigation coconut shell activated carbon is used for phenol removal because of its good adsorption ability and low cost. 1.1. Fluidization and Fluidized Beds Owning to the intense agitation in a well fluidizing bed, local temp and solid distribution are much more uniform than in the fixed bed. This may be important in many chemical and catalytic processes. Since in a fluidized bed particle size of a smaller order of magnitude than in the fixed bed, the resistance to diffusion through the particles is smaller in the fluidized bed. This too, may benefit many chemical and catalytic reactions. Fluidization will permit the ready additions of solids to or the withdrawals of solids from the bed. This is an important advantage over the fixed bed, especially where rapid activity losses are involved. This property of the fluidized bed system is responsible for the ease with which continuous operation is achieved. Owing to the motion of the particles, part internal or external heat transfer surfaces, heat transfer coeffiC0ents in fluidized beds are higher than in fixed beds operating under comparable flow conditions. Thus the fluidized bed offers a great advantage where highly exothermic or endothermic reactions are involved. Although heat transfer coefficients between solid particles and fluid appear to be of the same order of magnitude in both fluidized and fixed beds when both are operating under comparable flow rates, the state of subdivision and heat transfer surfaces are so much greater in the fluidized bed that the rate of solids fluid heat transfer is actually much higher in the fluidized bed. Due to the high particle fluid heat transfer rates, fluidized solids tend themselves more readily to recovery of heat from waste solids than to the generally larger solid particles of fixed bed. In many instances fluidization will cause smaller pressure drop than fixed bed operation. 1.2. Minimum Fluidization Velocity An equation for the minimum fluidization velocity can be obtained by setting the pressure drop across the bed equal to the weight of the bed unit area of cross section, allowing for the forces of the displaced fluid .Drag force by upward moving liquid is equal to weight of particles. Also Pressure drop across bed multiplied by Cross sectional area of tube is equal to Volume of bed multiplied by Fraction of solids. This method is the simplest way of calculating minimum fluidization velocity, Umf. The factors like particle size, particle shape, particle distribution, liquid flow rate, particle density, particle porosity, liquid density, liquid viscosity, diameter of conduit, shape of conduit, roughness of the surface, temperature and pressure affect the fluidization. Umf, the superficial velocity at minimum fluidizing conditions is found by the equation 1. s and l are solid and liquid densities respectively. μ is the liquid viscosity. Here Vom is the fluid velocity and dp is the particle diameter. is void fraction, , the sphericity and μ is the liquid viscocity. The density of adsorbent was found to be 0.42 gram/ml. At minimum fluidization velocity, Vom = Umf . The minimum fluidization velocity was observed to be 2.5 cm/sec for the system.

301

302


1.75

d p V om

2 l

150 1

3 s

mf 3

mf

s

d p V om

l

dp

2 l

l

s

g

2

(1)

mf

2. Methodology 2.1. Preparation of adsorbent The coconut shells were first cleansed to avoid the presence of mud on it. Fixed batch of coconut shells were allowed to stay in heating furnace where the temperature was maintained at about 250–275oC.The furnace used was digitally controlled. So we get accurate temperature required for the preparation. The coconut shells were allowed to stay in furnace till red hot. Thus fixed batch of shells were taken out according to our requirement. The red hot coconut shell was allowed to cool for some time till it reached the room temperature. Thus the shells completely burned were crushed using jaw crusher. As according to our requirement the jaw crusher was adjusted.The material after crushing was send to sieve analysis. 2.2. Experimental Procerdure Due to the non-availability of consistently uniform waste samples, synthetic phenol wastes of different concentrations were made. The concentration range of Phenol in the waste sample varied from as low as 100 mg/lit to as high as 300mg/lit for different runs. The parameters optimized were initial phenol concentration, flow rate and particle size of the adsorbent. 2.3. Study of adsorption isotherms Batch adsorption process is used for the study of equilibrium characteristics of the system. For the present experimental work, synthetically prepared phenol – water solution is used. The experiments were carried out in a batch reactor. During the experiments, mass of adsorbent and volumes of solution in each conical flask were kept constant. Phenol solutions of different concentrations varying from 25 – 300 ppm i.e. (25, 50, 75, 100, 200, and 300) were taken in different batches, thereafter 5 grams of coconut shell activated carbon was added to each reactor. The contents were stirred till adsorbent reached its saturation point. Samples were collected at particular time interval and analyzed by the volumetric titration to know the residual phenol concentration in the solution. The experiments were conducted till the equilibrium is attained. Freundlich Isotherm is presented in figure 1. 2.4. Break through capacity of adsorbent The break through capacity for coconut shell activated carbon was determined in fluidized bed type contactor for each run by changing one parameter at a time keeping other parameters constant for each run, the carbon was filled in the contactor and then phenol solution was run upward at a steady flow rate from bottom. The flow rate of solution of contactor was kept constant. Then different volumes of effluent samples were taken and analyzed to see whether the concentration of phenol reached the incoming phenol concentrations. When outlet phenol concentration reached initial value, the experiment was stopped. Precautions were taken to see that the flow rate was kept constant throughout the run and initially when filling the coconut shell activated carbon in the packed bed, to avoid channeling or dead zone in the bed, the bed was filled with distilled water first and then the coconut shell activated carbon was added so whatever air was there, it was removed in the form of bubbles and then the experiments were started. 2.5. Estimaton of % saturation We determined the area under curve for a graph of (C/C0) v/s (V-Vb)/(Vx-Vb). C and C0 are the outlet

303


Figure 1: Freundlich isotherm

concentration at any time and concentration at the inlet respectively. V, Vb and Vx are the volume of the liquid passed through the column at given time, breakthrough and exhaustion respectively. Area under the curve is the fractional capacity (f) .The value of (V-Vb)/(Vx-Vb) was calculated by plotting 1/(C-C0) verses C. The area under curve at any concentration C gives corresponding value of (V-Vb)/(Vx-Vb). Depth of the bed using equation 2 and percentage saturation by equation 3.

L[V x Vb ] Vb f [V x Vb ]

(2)

Where L is a bed height = 0.07m % saturation

L

(f L

1)

100

(3)

3. Experimental results and discussion The experiments conducted at various phenol concentration by keeping particle size and flowrate constant, are presented and discussed in this section. 3.1. Effect of initial phenol concentration The variation of C/C0 with time at different initial phenol concentration is shown in the figure 2. It was found that C/C0 value is minimum for first couple of readings and then it goes on increasing at reaches maximum value of 1. It reaches the maximum value in minimum time for the initial phenol concentration of 300 mg/l.This happens due to fact that as the time progresses the capacity of the bed reduces and at higher time adsorption capacity of bed becomes negligible. It is observed from same figure that for the initial phenol concentration of 300 mg/l, it takes minimum time i.e. 33 minutes to reach the maximum value of C/C0 . It is also observed that the rate of change in concentration is very high for initial period of 15 to 20 minutes and it goes on decreasing and is almost negligible towards the end. 3.2. Effect of flow rate

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Figure 3 shows the variation of C/C0 with time at different flow rates by keeping particle size and the initial phenol concentration constant. It is observed from the figure that as time increases C/C0 increases with increasing flow rate. At flow rate of 4.2 lpm, C/C0 reaches maximum value of 1 within minimum time interval of 50 minutes. 3.3. Effect of particle size The variation of C/C0 with time at different particle size is shown in the figure 4. The experiments were conducted at various particle size by keeping flow rates and the initial phenol concentration constant. From the figure, it has been observed that as time increases C/C0 increases with time at a given particle size. It is also observed from that as particle size decreases the required contact time reduces. The particle size of 0.420 mm was found to be more suitable than other particle size, since it requires minimum time i.e. 46 minutes to attain maximum C/C0 value of 1. The minimum paricle size offers more surface area for adsorption. 3.4. Effect on percentage saturation The effect of initial phenol concentration on percentage saturation is presented in Figure 5. It is observed from this figure that percentage saturation increases with initial phenol concentration at constant particle size and flow rate. Percentage saturation is realized maximum at initial phenol concentration of 300 mg/l. The variation of percentage saturation with flow rate is presented in Figure 6. It is also observed that from figure 6 that at the fixed particle size and initial phenol concentration, the maximum percentage saturation of 46 percent is observed at the flow rate of 4.2 lpm and percentage saturation increases with increase in flow rate. Figure 7 shows the effect of particle size on percentage saturation. It is observed from the figure that the percentage saturation attains the maximum value of 57 at corresponding particle size of 0.420 mm. It is also observed that percentage saturation decreases with increase in particle size. Conclusion The experimental studies on removal of phenol from waste water in a fluidized bed column using coconut shell activated carbon as a adsorbent have been reported. Experimental results agree well with well known Freundlich adsorption isotherm within 5 percent discrepancy. It is found from the present study that percentage saturation increases with increase in initial concentration of phenol and flow rate. Particle size also found to affect the adsorption operation. The inlet concentration of phenol and flow rate has significant effect on the adsorption operation. It is observed from present experimental study that percent saturation decreases with increase in particle size. The flow rate of 4.2 lpm yields maximum percent saturation of 46 percent.

Figure 2: Variation of C/C0 with time at different initial concentrations


Figure 3: Variation of C/C0 with time at different flow rates

Figure 4: Variation of C/C0 with time for different particle sizes

Figure 5: Effect of initial concentration on percentage saturation

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Figure 6 : Effect of flow rate on percentage saturation

Figure 7: Effect of particle size on percentage saturation

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[8] Treybal R.E.,1992 “Mass Transfer Operations” McGraw Hill 3rd Edition,pp. 565-645. [9] Sushmita Mishra, J. Bhattacharya, May 2006”Potential of Leaf Litter for Phenol Adsorption-a Batch Study” Indian Journal of Chemical Technology, Vol-13, , pp 298-301. [10] Edmund B.Besselievne and Max Schwartz, ,1976 “The Edmund B.Besselievne and Max Schwartz, “The Treatment of Industrial Waste” second ed, McGraw Hill Koga Kusha Ltd, pp. 26-101. [11] N.Manivasakam,“Industrial Effluent- Origin Characteristics,Effects, Analysis and Treatment” third ed, Publi Health Laboratory, Coimbatore , pp. 57-69 [12]K. Suneel Kumar, Kaustubha Mohanty, B. C., Meikap, 2010, “Treatment of phenolic wastewater in a multistage bubble column adsorber using activated carbon prepared from Tamarindus indica wood”, Journal Environmental Protection SC0ence., 4, , pp. 1-7. [13] David O. Coony and ZhenpengXi, Feb.1994,"Activated Carbon Catalizes Reaction of Phenolics During Liquid Phase Adsorption", AICHE, vol.40 No.2 ,. pp. 361-364 [14] S. Kumar, B. Rajmohan, K. Mohanty and B. C. Meikap, 2010, “Characterization of Activated Carbon Prepared from Tamarind Wood for Wastewater Treatment”, International Journal on Environmental Engineering, 2 (1/2/3), pp. 290-302. [15] Hasslen John W, 1957 “Activated Carbon” third ed, A Leonard Hill Book, Chemical Publishing Co. Inc., pp. 57-96 [16] Max Leva, 1969, “Fluidization”,McGraw Hill Publication, New York, pp. 45-250