Characteristic studies of some activated carbons from agricultural wastes

JAMBULINGAM et al.: PROPERTIES OF ACTIVATED CARBONS FROM AGRICULTURAL WASTES 495 Journal of Scientific & Industrial Research Vol. 66, June 2007, pp.495-500 Characteristic studies of some activated carbons from agricultural wastes M Jambulingam 1, *, S Karthikeyan 2, P Sivakumar 2, J Kiruthika 3 and T Maiyalagan 4 1 PG & Research Department of Chemistry, PSG CAS, Coimbatore 2 Department of Chemistry, Erode Sengunthar Engineering College, Thudupathi, Erode 638 057 3 Department of Biotechnology, Government College of Technology, Coimbatore 4 Department of Chemistry, IIT Madras, Chennai Received 07 September 2005; revised 17 November 2006; accepted 20 February 2007 Agricultural wastes like tobacco stem, bulrush Scirpus acutus stem, Leucaena leucocephala shell, Ceiba pentandra shell, Pongamia pinnata shell have been explored for the preparation of activated carbon. Characterization studies such as bulk density, moisture, ash, fixed carbon, matter soluble in water, matter soluble in acid, ph, decolourising power, phenol number, ion exchange capacity, iron content and surface area have been carried out to assess the suitability of these carbons as absorbents in water and wastewater. The results obtained show them to be good adsorbents for both organics and inorganics. Present study reveals the recovery of valuable adsorbents from readily and cheaply available agriculture wastes. Keywords: Activated carbon, Adsorption, Agricultural wastes, Surface area IPC Code: C01B31/08 Introduction Ancient Hindus in India used charcoal for drinking water filtration and Egyptians used carbonized wood as a medical adsorbent and purifying agent as early as 1500 BC 1. Activated carbon from vegetable material was introduced industrially in the first part of the 20 th century, and used in sugar refining 2. In the US, activated carbon from black ash was found very effective in decolorizing liquids 3. Agricultural by-products and waste materials used for the production of activated carbons include olive stones 4, almond shells 5, apricot and peach stones 6, maize cob 7, linseed straw 8, saw dust 9, rice hulls 10, cashew nut hull 11, cashew nut sheath 12, coconut shells and jusks 13, eucalyptus bark 14, linseed cake 15 and tea waste ash 16. Besides these, other sources of activated carbon are sulfonated coal 17, tyre coal dust, activated bauxite, cement kiln dust 18, ground sunflower stalk, shale oil ash, rubber seed coat, palm seed coat 19, de-oiled soya 20, baggase fly ash 21, Red mud 22 etc. This study explores new activated carbon from biological waste materials through various processes. *Author for correspondence Tel: 0422-5397901-902 E-mail: jambupsggas@rediffmail.com Materials and Methods Agricultural wastes (tobacco stem, bulrush Scirpus acutus stem, Leucaena leucocephala shell, Ceiba pentandra shell and Pongamia pinnata shell), collected from fallow lands in and around Erode District, Tamil Nadu, India, were cut into small pieces (3 cm), dried in sunlight and used for the preparation of activated carbons. The material to be carbonized was impregnated with respective salt solutions (,,, ) for varying periods. Accordingly, sufficient quantities were soaked well with 10% salt solution (5 l capacity) respectively so that the solution gets well adsorbed for a period of 24 h. At the end of 24 h, excess solution was decanted off and air-dried. Then the materials were placed in muffle furnace carbonized at 400 C for 60 min. The dried materials were powdered and activated in a muffle furnace kept at 800 C for 60 min. After activation, the carbons obtained were washed sufficiently with 4N HCI. Then the materials were washed with plenty of water to remove excess acid, dried and powdered. In Dolomite process, sufficient quantities of dried agricultural wastes were taken over a calcium

496 J SCI IND RES VOL 66 JUNE 2007 carbonate bed and the upper layer of waste was also covered with a layer of calcium carbonate. The whole material was carbonized at 400 C for 60 min, powdered well and followed by the thermal activation at 800 C for 60 min. In Acid process, dried material was treated with excess of. Charring of the material occurred immediately accompanied by evolution of heat in fumes. When the reaction subsided, mixture was left in an air oven maintained at 140-160 C for 24 h. In chemical activation process, 1 part of the material and 1.5 parts of were mixed with 0.4 parts of N and kept in muffle furnace at 120 C for 14 h. At the end of this period, the product was washed with large volume of water to remove free acid, dried at 110 C and finally activated at 800 C for 60 min. ph and conductivity were analyzed using Elico ph meter (model L1-120) and conductivity meter (model M-180), respectively. Moisture content (%) by mass, ash (on dry basis) % by mass, bulk density, specific gravity, porosity, matter soluble in water, matter soluble in acid, phenol adsorption capacity, carbon tetrachloride activity, iron content were analyzed as per standard procedures. Estimation of Na and K was done using Elico Model Flame Photometer. BET surface area was measured at liquid N 2 temperature using Quantachrome Analyzer. Results and Discussion Bulk density of carbons obtained from all the materials shows that Bulrush S. acutus carbon has the higher bulk density due to its high fibre content and P. pinnata carbon has the lower bulk density, which can be attributed to the material hardness (Tables 1-5). Ash content for all the varieties of carbons is very low thereby increasing the fixed carbon content except for the carbon obtained from P. pinnata and Bulrush S. acutus carbon by N. Except carbons prepared by Acid process, carbon obtained from all other processes exhibit small amount of leaching property. Characterization studies on porosity, surface area. Iodine number, CCl 4 activity and phenol adsorption capacity clearly indicate that the carbons obtained by various processes will depend only on the composition of raw agricultural waste surface area properties of process for Bulrush Scirpus acutus carbon, HCl process for Leucaena and C. pentandra shell waste carbon, chloride process for tobacco waste and Dolomite process for Pongamia carbon. Iron content is almost uniform for all the five carbons. This level of iron content will not affect the effluent water without the problem of iron leaching into Table 1 Activated carbon from Tobacco stem Sl. No Properties HCl Ca N 1 ph 6.71 5.50 6.20 8.63 8.15 9.03 7.19 7.80 6.98 2 Moisture content, % 9.2 10.2 26.8 11.8 11.8 4.4 19.2 10.8 8.8 3 Ash content, % 10.69 14.46 10.16 13.89 10.68 8.78 14.20 8.36 8.86 4 Volatile matter, % 12.20 9.30 9.81 14.40 11.40 16.80 14.90 11.20 10.50 5 Fixed carbon 74.6 73.5 59.8 73.1 68.8 75.2 68.8 81.0 83.1 6 Conductivity, ms/cm 0.23 0.20 0.41 0.19 0.42 0.31 0.26 0.59 0.92 7 Specific gravity, S 1.10 1.33 1.49 0.89 1.25 1.48 1.32 1.88 1.37 8 Bulk density, D 0.63 0.69 0.51 0.44 0.56 0.42 0.36 0.66 0.49 9 Porosity 24.55 33.08 72.48 50.56 39.20 64.86 65.15 54.26 42.34 10 Matter soluble in water, % 0.60 0.58 0.78 1.03 2.42 1.88 2.66 1.81 1.84 11 Matter soluble in acid, % 0.81 0.13 1.14 1.59 1.24 1.50 1.03 0.61 1.44 12 Surface area, m 2 /g 385 351 1250 342 760 271 1204 858 723 13 Sodium, w/w % 1.1 5.1 8.0 5.0 6.1 8.0 12.0 1.5 6.0 14 Potassium, w/w % 4.1 5.1 8.6 6.7 3.6 4.1 3.0 4.0 1.0 15 Yield, % 40 50 46 32 31 60 47 50 65

JAMBULINGAM et al.: PROPERTIES OF ACTIVATED CARBONS FROM AGRICULTURAL WASTES 497 Table 2 Activated carbon from Pongamia pinnata shell Sl. No Properties HCl Ca 1 ph 6.42 5.02 6.54 9.60 8.22 9.11 8.25 7.18 6.05 2 Moisture content, % 5.2 7.4 10.8 5.6 9.6 9.0 7.2 6.4 5.6 3 Ash content, % 15.75 9.74 10.06 7.70 10.04 16.81 19.00 27.00 9.02 4 Volatile matter, % 8.8 10.2 15.8 13.6 11.5 17.6 8.0 9.1 6.8 5 Fixed carbon 87.5 82.1 73.4 76.6 85.2 70.4 81.6 81.0 84.6 6 Conductivity, ms/cm 0.35 0.66 0.13 0.61 0.49 0.14 0.66 0.10 0.81 7 Specific gravity, S 0.45 0.63 0.93 0.92 0.83 0.93 0.50 0.83 1.25 8 Bulk density, D 0.33 0.40 0.32 0.37 0.39 0.39 0.34 0.38 0.43 9 Porosity 40.00 51.81 49.21 59.78 53.01 58.06 32.00 54.22 65.60 10 Matter soluble in water, % 1.51 1.35 1.44 0.89 1.05 1.04 1.86 2.35 2.20 11 Matter soluble in acid, % 0.55 0.89 1.25 1.47 1.03 0.78 1.64 1.31 1.64 12 Surface area, m 2 /g 289 514 219 722 602 746 228 322 455 13 Sodium, w/w % 8.2 1.3 6.0 13.0 18.0 1.0 1.2 3.0 8.5 14 Potassium, w/w % 1.2 1.4 1.9 3.7 1.3 1.3 9.0 1.8 6.0 15 Yield, % 49 65 51 39 41 50 42 56 55 Table 3 Activated carbon from Ceiba pentandra shell Sl. No Properties HCl Ca 1 ph 5.55 6.41 5.35 8.57 9.60 8.30 8.13 8.09 6.71 2 Moisture content, % 12.0 6.6 8.5 6.6 4.0 9.0 6.5 4.9 6.2 3 Ash content, % 10.04 11.64 10.96 15.09 7.42 7.02 17.12 14.67 12.83 4 Volatile matter, % 14.5 20.2 25.0 20.8 17.3 25.2 22.2 10.5 17.4 5 Fixed carbon 69.3 69.5 62.9 68.7 74.0 63.7 73.8 76.5 72.6 6 Conductivity, ms/cm 0.13 0.29 0.19 0.17 0.05 0.24 0.14 0.16 0.08 7 Specific gravity, S 1.17 0.97 0.98 0.96 1.20 1.19 1.07 0.92 1.02 8 Bulk density, D 0.43 0.37 0.30 0.34 0.53 0.30 0.43 0.38 0.41 9 Porosity 63.25 61.86 69.39 64.58 55.83 74.79 59.81 58.70 59.80 10 Matter soluble in water, % 0.85 0.51 0.87 0.43 1.00 1.68 0.55 0.25 0.85 11 Matter soluble in acid, % 0.63 0.48 0.43 0.45 0.62 1.80 0.68 0.45 0.85 12 Surface area, m 2 /g 1143 424 321 430 429 750 261 309 403 13 Sodium, w/w % 4.0 1.1 7.0 1.2 6.0 4.0 3.0 5.6 1.3 14 Potassium, w/w % 2.0 4.0 7.0 5.0 3.0 9.0 1.3 5.0 4.0 15 Yield, % 60 40 32 36 36 41 32 35 44

498 J SCI IND RES VOL 66 JUNE 2007 Table 4 Activated carbon from Scirpus acutus stem Sl. No Properties HCl Ca 1 ph 6.13 5.22 6.42 9.04 9.51 8.02 8.64 7.54 6.04 2 Moisture content, % 8.9 8.6 4.2 6.6 16.0 1.1 15.6 12.0 12.1 3 Ash content, % 4.15 12.87 19.38 17.28 13.89 10.89 10.79 26.70 12.11 4 Volatile matter, % 12.8 12.9 10.0 15.8 12.5 10.2 11.0 11.6 9.1 5 Fixed carbon 82.2 79.8 81.0 82.2 82.0 79.1 83.0 81.1 80.1 6 Conductivity, ms/cm 1.98 4.10 0.90 1.13 1.69 0.45 0.67 0.77 0.20 7 Specific gravity, S 1.31 1.05 0.66 0.83 0.63 0.43 0.62 1.05 0.91 8 Bulk density, D 0.46 0.75 0.36 0.35 0.42 0.28 0.32 0.70 0.48 9 Porosity 55.34 40.00 58.14 44.44 49.40 55.56 60.98 44.00 40.74 10 Matter soluble in water, % 0.89 0.41 0.69 1.15 1.34 0.96 0.52 1.06 0.62 11 Matter soluble in acid, % 0.80 0.40 0.65 1.55 1.57 1.43 0.65 1.32 1.77 12 Surface area, m 2 /g 901 554 612 429 480 263 762 501 559 13 Sodium, w/w % 6.6 1.4 1.6 3.1 4.2 8.8 2.1 5.2 6.1 14 Potassium, w/w % 63 1.9 5.0 4.5 1.6 4.11 10.9 50 67 15 Yield, % 42 39 43 39 30 51 49 54 37 Table 5 Activated carbon from Leucaena leucocephala seed shell Sl. No Properties HCl Ca 1 ph 6.74 6.67 6.96 8.10 9.05 9.50 7.86 6.95 7.25 2 Moisture content, % 10.9 12.0 15.0 10.9 15.0 10.4 18.2 10.6 10.9 3 Ash content, % 14.50 10.94 15.57 17.07 7.12 1.57 16.07 5.67 16.85 4 Volatile matter, % 20.00 26.70 27.50 31.20 30.00 24.20 27.80 31.30 34.20 5 Fixed carbon 73.80 73.50 59.80 73.10 69.00 72.10 69.70 81.00 84.30 6 Conductivity, ms/cm 0.13 0.20 0.69 0.33 0.22 0.17 0.14 0.29 0.49 7 Specific gravity, S 1.00 1.31 1.09 0.81 1.05 1.08 1.35 1.98 1.07 8 Bulk density, D 0.83 0.89 0.41 0.44 0.76 0.52 0.46 0.86 0.79 9 Porosity 24.55 33.08 72.48 50.56 39.20 64.86 65.15 54.26 42.34 10 Matter soluble in water, % 0.90 0.48 1.78 2.03 1.42 2.88 2.06 0.81 0.84 11 Matter soluble in acid, % 0.91 0.23 1.12 1.50 1.44 1.70 1.43 0.81 0.44 12 Surface area, m 2 /g 278 341 1320 342 798 229 1204 888 713 13 Sodium, w/w % 2.2 5.8 8.4 7.4 6.4 4.0 5.0 15.5 10.0 14 Potassium, w/w % 13.1 7.9 7.6 10.7 7.0 6.6 2.9 9.0 8.0 15 Yield, % 45 51 40 31 42 52 39 50 65

JAMBULINGAM et al.: PROPERTIES OF ACTIVATED CARBONS FROM AGRICULTURAL WASTES 499 Percentage of dye removal Dye removal, % 120 100 80 60 40 20 0 20 mg/l 40 mg/l 60 mg/l 0 50 100 150 200 250 Time min Fig. 1 Influence of time on percentage of dye removalconcentration variation treated water. The level of Na and K content is high only in the case of tobacco waste carbon. In general, Na and K content are high in sulphate and chloride process when compared to other treatments. Yield of Bulrush S. acutus carbon prepared by process found high in a vast margin when compared to other carbons. Because of high charring power of, yield of carbon by process shows better result. Surface plays a predominant role for the adsorption of solutes from solution. Classification of activated carbons based on their surface area is as follows: Caron I: Tobacco stem, > > N > > > HCl> > > Dolomite; Carbon II: P. pinnata shell, Dolomite > > > > > N > HCl > > ; Carbon III: C. pentandra shell, HCl > Dolomite > > NO 3 > > > > N > ; Carbon IV: Bulrush S. acutus Stem, HCl > > > > > N > > > Dolomite; and Carbon V: L. leucocephala shell, > > N > > > > >HCl > Dolomite. Surface area of these 5 novel carbons is far better when compared to other carbons. Activated carbon, prepared from L. Leucocephala shell using process, shows high surface area and is selected for further studies to analyze its applicability for water treatment purpose. Adsorption of Rhodamine-B (Basic Dye) onto activated carbon prepared from L. leucocephala shell using process showed that at low concentration (20 mg/l) of dye solution, adsorbent can remove up to 98.00 % of the dye molecules present in the solution (Fig. 1). Even at the high concentrations (40 mg /l & 60 mg/l), adsorbent was able to remove 83.5 % of the dye molecules present in the solution. Conclusions Based on surface area, the following activated carbons/processes are comparable with the commercially available activated carbons: I) Tobacco stem / process; ii) P. pinnata shell / Dolomite process; iii) C. pentandra shell / HCl process; iv) Bulrush S. acutus stem / HCl process; and v) L. leucocephala shell / process. These carbons can be conveniently used for textile effluents removal. In general, all these carbons will be efficient for the adsorption of organics as seen from adsorption of Rhodamine-B from its solution with L. leucocephala shell. References 1 Cheremisinoff N P & Morresi A C, Carbon Adsorption Applications, Carbon Adsorption Handbook (Ann Arbor Science Pub., Inc: Ann Arbor Michigen) 1980, 1-54. 2 Bansal R C, Donnet J B & Stoeckli F, Active Carbon (Marcel Dekker, New York) 1988. 3 Mantell C L, Carbon and Graphite Handbook (John Wiley & Sons, New York) 1968. 4 Lopez-Gonzalez D J, High temperature adsorption of hydrocarbons by activated carbons prepared from olive stones, Adv Sci Technol, 1 (1984) 103-109. 5 Linares-Solano, Lopez-Gonzalez D J, Molina-Sabio M & Rodriguez-Reinoso F, Active carbons from almond shells as adsorbents in gas and liquid phases, J Chem Tech Biotechnol, 30 (1980) 65-72. 6 Nasser M M & El-Geundi M S, Comparative cost of color removal from textile effluents using natural adsorbents, J Chem Biotechnol, 50 (1991) 257-264. 7 Bousher A, Shen X & Edyvean R G J, Removal of colored organic matter by adsorption on to low cost waste materials, Water Res, 31 (1997) 2084-2092. 8 Kadirvelu K, Palanivel M, Kalpana R & Rajeshwari S, Activated carbon from an agricultural by-product, for the treatment of dyeing industry wastewater, Biores Technol, 74 (2000) 263-265. 9 Srinivasan K, Balasubramanian N & Ramakrishna T V, Studies on chromium removal by rice husk carbon, Indian J Environ Hlth, 30 (1988) 376-387. 10 Rengaraj S, Banumathi A & Murugesan B, Preparation and characterization of activated carbon from agricultural wastes, Indian J Chem Technol, 6 (1999) 1-4. 11 Banerjee S K, Majmudar S, Roy A C, Banerjee S C & Banerjee D K, Activated carbon from coconut shell, Indian J Technol, 14 (1976) 45-49. 12 Mortley Q, Mellowes W A & Thomas S, Activated carbon from materials of varying morphological structure, Thermochin Acta, 129 (1988) 173-186.

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