PHENOL REMOVAL IN PACKED BED USING COCONUT STALK AS ADSORBENT

Transcription

1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 11, November 2017, pp , Article ID: IJMET_08_11_035 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed PHENOL REMOVAL IN PACKED BED USING COCONUT STALK AS ADSORBENT C R Girish and Swaroop M Shajahan Department of Chemical Engineering, Manipal Institute of Technology, Manipal University, India ABSTRACT The present paper investigates the application of coconut stalk fibre to remove phenol from wastewater in a packed column. The influence of operating conditions like flow rate (5, 10, 15 ml/min) and bed height (4, 8 and 12 cm) on the adsorption were investigated. The dynamic behavior of the packed column was studied by drawing the breakthrough curves. The experimental data were investigated by using Thomas model and BDST model. It was found that the adsorption capacity increased with increase in flow rate and bed depth. The BDST model was employed to calculate the service time required for saturation of the bed which will be used for the design of the column. The adsorption capacity was evaluated as mg/g showing that coconut stalk is a promising adsorbent. Keywords: Coconut stalk, wastewater, packed column, breakthrough time, phenol Cite this Article: C R Girish and Swaroop M Shajahan, Phenol Removal in Packed Bed Using Coconut Stalk as Adsorbent, International Journal of Mechanical Engineering and Technology 8(11), 2017, pp INTRODUCTION Industrial wastewater contains many pollutants which causes harmful effects on the environment and the aquatic life [1]. Phenol is one of the pollutant released from wastewater and it is considered as one of the priority pollutants [2]. The source of wastewater are from industries like textile, leather, paper and plastic industries [3]. The allowable concentration of phenol in wastewater as per the environmental protection agency is less than 1 mg/l [4]. Therefore there is a need to treat phenol before it is released into the environment. Different treatment methods like adsorption, coagulation, precipitation, filtration, membrane separation and oxidation are employed for removing phenol from wastewater [5]. Adsorption using adsorbent is considered as the efficient method for removing phenol. Adsorption using commercial activated carbon made from coal, silica gel, alumina, fly ash is considered as an expensive process and regenerating the adsorbent is also difficult [6]. Therefore attention was given to the production of adsorbent from low cost agricultural materials. Various agricultural waste materials like beet pulp [7], coir pith [8], rice husk [9], jute [10], coconut stalk [11] and lantana [12] were used for adsorbent preparation. Batch studies are carried out for removing editor@iaeme.com

2 Phenol Removal in Packed Bed Using Coconut Stalk as Adsorbent phenol using these agricultural waste materials. But the research data on the removal of phenol using agricultural materials in continuous mode are limited. The continuous studies are preferred because it is simple in operation, high yield is obtained and easily scaled up from the laboratory scale [13, 14]. Therefore, in the current work, the adsorption of phenol from wastewater onto coconut stalk was done in packed bed. The study investigates the influence of feed rate and bed height on the process in the packed column. The breakthrough curves (dimensionless concentration curve) are drawn to assess the behavior of the column and to design the packed column. 2. DETERMINATION OF ADSORPTION PARAMETERS The breakthrough curves are employed to assess the performance of continuous column. The breakthrough time and nature of dimensionless curve are required for studying the operation and dynamic behaviour of packed column [15]. The dimensionless concentration curve is given by dimensionless concentration varying with time. The breakthrough time defines the required time for the exit concentration to become 10% of the original concentration. The exhaustion time is the time necessary when the exit concentration becomes 90% of initial concentration. The and are important in finding how the saturation of the bed takes place [16, 17]. The total quantity of the pollutant adsorbed is evaluated by calculating the area under the dimensionless curve = (1) the feed rate (ml/min), the total adsorption time (min), the concentration of solute adsorbed (mg/l). The equilibrium adsorption capacity is evaluated from the expression [1, 15, 18], = (2) the amount of the adsorbent material (g). 3. MODELS USED FOR PACKED BED EXPERIMENTAL DATA 3.1 BDST Model The model is used to explain the adsorption of the pollutant from wastewater in a packed column. The equation relates the bed depth and the necessary time for the saturation required for the bed [19]. =! # $ ln ' 1 (3) the initial concentration (mg/l), the concentration at breakthrough point (mg/l), ) total bed capacity by bed volume (mg/l), * the velocity (m/min) and + the rate constant (l/(mg h)). The expression is of the form =,. + (4) The sorption capacity ) and rate constant + are found from the plot of v/s. [20]. 3.2 Thomas Model The model is useful for assessing the column performance and for getting dimensionless curves. It is derived on the assumption that Langmuir isotherm is used for adsorption of adsorption behaviour. It also follows that axial dispersion is not important in the adsorption of the column. The linear equation of model is as [21] editor@iaeme.com

3 C R Girish and Swaroop M Shajahan 01( 1=2 34,/ 2 34 (5) and the outlet concentration at any time and inlet solute concentrations (mg/l), + 34 the rate constant (ml/min mg),, the theoretical adsorption capacity (mg/g), the mass of adsorbent material (g) and the feed rate of the solution (ml/min). The constants + 34 and, are determined from the plot of v/s [22, 23]. 4. MATERIALS AND METHODS 4.1. Preparation of the adsorbent Coconut stalk obtained from South Travancore region were used. The raw material was washed with water so that all earthy material is removed. Then it is dried at 50 o C for one day to remove the moisture content. Then it is ground and sieved to get powder of finer size. The adsorbent preparation was done by the treating the carbon powder with various chemicals such as sulphuric acid, hydrochloric acid and phosphoric acid. The carbon powder was treated with the above chemicals and then dried at 80 o C for 5 hours [24]. Later the material was washed with water till the slurry was clear and constant ph value was obtained. Then the powder was dried and used for the experiments. From the results of previous experiments [11], the adsorbent treated with HCl for taken for packed bed studies. 4.2 Chemicals used Phenol (Merck India Ltd) was used for the experiments and stock solution was prepared. The required phenol concentration of 200 mg/l was prepared from the original solution. The other chemicals hydrochloric acid, sulphuric acid and phosphoric acid (SD Fine chemicals) are treated with the adsorbent. 4.3 Column studies The packed bed studies were performed in a glass tube of 15 mm dia and 400 mm height. The experimental arrangement for the investigation is represented in Fig.1. The studies were carried out by changing the bed height and the flow rate of the pollutant. The bed height was prepared by packing 1.93 g, 3.89 g and 5.81 g of the adsorbent treated with HCl to get 4cm, 8cm and 12cm of bed depth. The phenol flow rate was varied from 5ml/min to 15ml/min by keeping the concentration at 200 mg/l. The bed height was measured prior to the experiments in order to check the variation in packing. The adsorbent bed was covered with glass wool on both the sides. Then the solution was sent into the column with the help of a peristaltic pump. The phenol solutions were immediately collected at the outlet for measuring the remaining phenol concentration. The remaining concentration was analyzed with UV vis spectrophotometer at 270 nm editor@iaeme.com

4 Phenol Removal in Packed Bed Using Coconut Stalk as Adsorbent Figure 1 The representation of the Packed Bed Experimental Arrangement. 5. RESULTS AND DISCUSSION 5.1 Influence of flow rate The variation of feed rate on the adsorption was done by the variation of feed rate from 5 to 15 ml /min at phenol concentration (200 mg/l) and bed height 8cm. The plots of dimensionless outlet concentration of phenol versus time for various flow rates are given in figure 2. It was 1 Dimensionless concentration ml/min 10 ml/min 5 ml/min t, min Figure 2 The dimensionless curves at different values of flow rates. Observed that steep dimensionless curves were obtained at high flow rates [25, 26]. It was also studied that as the flow rate increases, and decreases as shown in Table 1 [27]. It was noticed that the adsorption capacity increases by increasing the flow rate. This is due to the reason that more mass transfer occurs between the adsorbate and the adsorbent [4] editor@iaeme.com

5 C R Girish and Swaroop M Shajahan 5.2 Influence of bed height The influence of bed depth on the dimensionless curves are studied by variation of bed height in the range 4cm, 8cm, 12cm by keeping the concentration 200 mg/l and flow rate 15 ml/min and are given in fig 3. It is observed that with the increase in bed height from 4 to 12 cm, the experimental break point time increases as given in table 2 [22]. It was noted that lower saturation time was obtained for shorter bed depths. This may be because of bed getting saturated faster. Also shorter bed shows less adsorption capacity to remove the pollutant [28]. The adsorption capacity increases with bed height, because it increases surface area and sufficient surface sites are available for the process [15]. 1 Dimensionless concentration cm 8 cm 12 cm t, min Figure 3 The dimensionless curves at different values of bed heights. 5.3 Modeling of packed column data To study the adsorption of the pollutant in the packed bed and to use it for industrial applications Thomas and BDST models were employed. The experiment data were validated with the models. Thomas model: By increasing the bed height, the value of, increases as shown in Table 3 and 4 showing that more active sites are available for adsorption. Similar type of results were obtained in the work [3]. It was found that by increasing the feed rate the adsorption capacity increased and k value also increases. The probable reason is that adsorption is depending on the amount of the adsorbent available for adsorption [6]. Also bed gets saturated faster at higher flow rates. BDST model The parameters were calculated and are listed in Table 5. It was found that as the values increases, the values of ) increases while + decreases. The rate constant + signifies the rate at which pollutant is transferred from the liquid phase to the adsorbent [3] As the value of + increases, it shows that breakthrough will be prevented by shorter bed. But for higher value of + it signifies breakthrough can be prevented by lengthier bed [29]. The increase in ) value explains the existence of large mass transfer driving force editor@iaeme.com

6 Phenol Removal in Packed Bed Using Coconut Stalk as Adsorbent Table 1 The adsorption constants for various values of flow rate. 9(ml/min) : ;< (min) : => (min) Adsorption capacity? =,=>@ AB B 5ml/min ml/min ml/min Table 2 The adsorption parameters for various values of bed height. C(cm) : ;< (min) : => (min) Adsorption capacity? =,=>@ AB B 4cm cm cm Table 3 Thomas model constants at various values of flow rates. 9(ml/min) D EF (ml/ mg min)? =,: (mg/g)? =,=>@ AB B G H Table 4 Thomas model constants at various bed heights. C(cm) D EF (ml/ mg min)? =,: (mg/g)? =,=>@ AB B G H Table 5 The values of BDST parameters at different values of breakthrough curve. I ; I J K ALM/KA N OPQ R S AB/T D SN U AB ALM Z[ Z[ Z[ 6. CONCLUSIONS The present paper investigated the ability of the coconut stalk as an adsorbent for removing phenol from wastewater. Packed bed experiments were conducted to increase the adsorption capacity. It was found from the experiments that as the feed rate increases the total adsorption capacity increased. It was also noticed that with the increase in bed heights, the capacity increased because of the availability of more active sites. The performance of the column was assessed with the help of Thomas and BDST models. The BDST parameters are helpful for the design of the column and to study the performance of the column. REFERENCES [1] Z. Saadi, R. Saadi, R. Fazaeli, Fixed-bed adsorption dynamics of Pb (II) adsorption from aqueous solution using nanostructured γ-alumina, Journal of Nanostructure in Chemistry, 3(1), 2013, editor@iaeme.com

7 C R Girish and Swaroop M Shajahan [2] F.A. Banat, B. Al-Bashir, S. Al-Asheh, O. Hayajneh, Adsorption of phenol by bentonite, Environmental Pollution,107(3), 2000, [3] L. Zhao, W. Zou, L. Zou, X. He, J. Song, R. Han, Adsorption of methylene blue and methyl orange from aqueous solution by iron oxide-coated zeolite in fixed bed column: predicted curves, Desalination and Water Treatment, 22(1-3), 2010, [4] P. D. Rocha, A. S. Franca, L. S. Oliveira, Batch and column studies of phenol adsorption by an activated carbon based on acid treatment of corn cobs, International Journal of Engineering and Technology, 7(6), 2015, 459. [5] A. C. Lua, Q. Jia, Adsorption of phenol by oil palm-shell activated carbons in a fixed bed, Chemical Engineering Journal, 150(2), 2009, [6] J. Song, W. Zou, Y. Bian, F. Su, R. Han, Adsorption characteristics of methylene blue by peanut husk in batch and column modes, Desalination, 265(1), 2011, [7] D. Gulbeyi, C. Handan, A. Y. Dursun, Adsorption of phenol from aqueous solution by using carbonised beet pulp, Journal of Hazardous Materials, B(125), 2005, [8] C. Namasivayam, D. Kavitha, IR, XRD and SEM studies on the mechanism of adsorption of dyes and phenols by coir pith carbon from aqueous phase, Microchemical Journal, 82(1),2006, [9] P. M. Shiundu, D.N. Mbui, R. M. Ndonye, G. N. Kamau, Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin, Journal of Environmental Monitoring, 4, 2002, [10] L.C. Laurence, H. P. Ngoc, R. Sebastien, F. Catherine, L.C. Pierre, H. N. Thanh, Production of fibrous activated carbons from natural cellulose (jute, coconut) fibers for water treatment applications, Carbon, 44 (12), 2006, [11] C R. Girish, Swaroop M. Shajahan, Removal of Phenol from Wastewater Using Chemically Treated Coconut Stalk: Cocos nucifera, International Research Journal of Environment Sciences, 3(6), 2014, [12] C R. Girish, V. R. Murty, Mass transfer studies on adsorption of phenol from wastewater using Lantana camara, forest waste, International Journal of Chemical Engineering, [13] G. Vázquez, R. Alonso, S. Freire, J. González-Álvarez, G. Antorrena, Uptake of phenol from aqueous solutions by adsorption in a Pinus pinaster bark packed bed, Journal of hazardous materials, 133(1), 2006, [14] C. R. Girish, V. R. Murty, Adsorption of phenol from aqueous solution using Lantana camara, forest waste: packed bed studies and prediction of breakthrough curves,environmental Processes, 2(4), 2015, [15] S. Chen, Q. Yue, B. Gao, Q. Li, X. Xu, K. Fu, Adsorption of hexavalent chromium from aqueous solution by modified corn stalk: a fixed-bed column study, Bioresource technology, 113, 2012, [16] K. Vijayaraghavan, J. Jegan, K. Palanivelu, M. Velan, Biosorption of copper, cobalt and nickel by marine green alga Ulva reticulata in a packed column, Chemosphere, 60(3), 2005, [17] H. Muhamad, H. Doan, A. Lohi, Batch and continuous fixed-bed column biosorption of Cd 2+ and Cu 2+. Chemical Engineering Journal, 158(3), 2010, [18] M. Dutta, J. K. Basu, H. FaraZ, N. Gautam, A. Kumar, Fixed bed column study of textile dye, direct blue 86 by using a composite adsorbent, Archives of Applied Science Research, 4(2), 2012, [19] A. B. Albadarin, C. Mangwandi, H. Ala'a, G. M. Walker, S. J. Allen, M. N. Ahmad, Modelling and fixed bed column adsorption of Cr (VI) onto orthophosphoric acidactivated lignin, Chinese Journal of Chemical Engineering, 20(3), 2012, editor@iaeme.com

8 Phenol Removal in Packed Bed Using Coconut Stalk as Adsorbent [20] C. M. Hasfalina, R. Z. Maryam, C. A. Luqman, M. Rashid, Adsorption of copper (II) from aqueous medium in fixed-bed column by kenaf fibres, APCBEE procedia, 3, 2012, [21] M. Bhaumik, K. Setshedi, A. Maity, M. S. Onyango, Chromium (VI) removal from water using fixed bed column of polypyrrole/fe 3 O 4 nanocomposite, Separation and Purification Technology, 110, 2013, [22] Y. Long, D. Lei, J. Ni, Z. Ren, C. Chen, H. Xu, Packed bed column studies on lead (II) removal from industrial wastewater by modified Agaricus bisporus, Bioresource technology, 152, 2014, [23] H. Nouri, A. Ouederni, Modeling of the dynamics adsorption of phenol from an aqueous solution on activated carbon produced from olive stones, International Journal of Chemical Engineering and Applications, 4(4), 2013, 254. [24] P. Canizares, M. Carmona, O. Baraga, A. Delgado, M.A. Rodrigo, Adsorption equilibrium of phenol onto chemically modified activated carbon F400, Journal of Hazardous Materials, 131, 2006, [25] A. Goshadrou, A. Moheb, Continuous fixed bed adsorption of CI Acid Blue 92 by exfoliated graphite: An experimental and modeling study. Desalination, 269(1), 2011, [26] R. Han, Y. Wang, W. Zou, Y. Wang, J. Shi, Comparison of linear and nonlinear analysis in estimating the Thomas model parameters for methylene blue adsorption onto natural zeolite in fixed-bed column, Journal of Hazardous Materials, 145(1), 2007, [27] D. Charumathi, N. Das, Packed bed column studies for the removal of synthetic dyes from textile wastewater using immobilised dead C. tropicalis, Desalination, 285, 2012, [28] S. Singha, U. Sarkar, S. Mondal, S. Saha, Transient behavior of a packed column of Eichhornia crassipes stem for the removal of hexavalent chromium, Desalination, 297, 2012, [29] K. Vijayaraghavan, J. Jegan, K. Palanivelu, M. Velan, Removal of nickel (II) ions from aqueous solution using crab shell particles in a packed bed up-flow column, Journal of Hazardous Materials, 113(1), 2004, editor@iaeme.com