Characteristic studies of some activated carbons from agricultural wastes
JAMBULINGAM et al.: PROPERTIES OF ACTIVATED CARBONS FROM AGRICULTURAL WASTES 495Journal of Scientific & Industrial ResearchVol. 66, June 2007, pp.495-500 Characteristic studies of some activated carbons from agricultural wastes M Jambulingam1,*, S Karthikeyan2, P Sivakumar2, J Kiruthika3 and T Maiyalagan4 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: C01B31/08Introduction Materials and Methods Ancient Hindus in India used charcoal for Agricultural wastes (tobacco stem, bulrushdrinking water filtration and Egyptians used carbonized Scirpus acutus stem, Leucaena leucocephala shell, Ceibawood as a medical adsorbent and purifying agent as early pentandra shell and Pongamia pinnata shell), collectedas 1500 BC1. Activated carbon from vegetable material from fallow lands in and around Erode District, Tamilwas introduced industrially in the first part of the 20th Nadu, India, were cut into small pieces (3 cm), dried incentury, and used in sugar refining2. In the US, activated sunlight and used for the preparation of activatedcarbon from black ash was found very effective in carbons.decolorizing liquids3. Agricultural by-products and waste The material to be carbonized was impregnatedmaterials used for the production of activated carbons with respective salt solutions (ZnCl2, CaCl2, Na2SO4,include olive stones4, almond shells5, apricot and peach Na2CO3) for varying periods. Accordingly, sufficientstones6, maize cob7, linseed straw8, saw dust9, rice hulls10, quantities were soaked well with 10% salt solutioncashew nut hull11, cashew nut sheath12, coconut shells (5 l capacity) respectively so that the solution gets welland jusks13, eucalyptus bark14, linseed cake15 and tea adsorbed for a period of 24 h. At the end of 24 h, excesswaste ash16. Besides these, other sources of activated solution was decanted off and air-dried. Then thecarbon are sulfonated coal17, tyre coal dust, activated materials were placed in muffle furnace carbonized atbauxite, cement kiln dust18, ground sunflower stalk, shale 400°C for 60 min. The dried materials were powderedoil ash, rubber seed coat, palm seed coat19, de-oiled and activated in a muffle furnace kept at 800°C forsoya20 , baggase fly ash21, Red mud22 etc. This study 60 min. After activation, the carbons obtained wereexplores new activated carbon from biological waste washed sufficiently with 4N HCI. Then the materialsmaterials through various processes. were washed with plenty of water to remove excess acid,*Author for correspondence dried and powdered.Tel: 0422-5397901-902 In Dolomite process, sufficient quantities ofE-mail: email@example.com dried agricultural wastes were taken over a calcium
496 J SCI IND RES VOL 66 JUNE 2007carbonate bed and the upper layer of waste was also Results and Discussioncovered with a layer of calcium carbonate. The whole Bulk density of carbons obtained from all thematerial was carbonized at 400°C for 60 min, powdered materials shows that Bulrush S. acutus carbon has thewell and followed by the thermal activation at 800°C higher bulk density due to its high fibre content and P.for 60 min. In Acid process, dried material was treated pinnata carbon has the lower bulk density, which canwith excess of H2SO4. Charring of the material occurred be attributed to the material hardness (Tables 1-5). Ashimmediately accompanied by evolution of heat in fumes. content for all the varieties of carbons is very lowWhen the reaction subsided, mixture was left in an air thereby increasing the fixed carbon content except foroven maintained at 140-160°C for 24 h. In chemical the carbon obtained from P. pinnata and Bulrush S.activation process, 1 part of the material and 1.5 parts acutus carbon by H2SO4+NH4S 2O8. Except carbonsof H2SO4 were mixed with 0.4 parts of NH4S2O8 and prepared by Acid process, carbon obtained from all otherkept in muffle furnace at 120°C for 14 h. At the end of processes exhibit small amount of leaching property.this period, the product was washed with large volume Characterization studies on porosity, surfaceof water to remove free acid, dried at 110°C and finally area. Iodine number, CCl4 activity and phenol adsorptionactivated at 800°C for 60 min. capacity clearly indicate that the carbons obtained by pH and conductivity were analyzed using Elico various processes will depend only on the compositionpH meter (model L1-120) and conductivity meter (model of raw agricultural waste surface area properties ofM-180), respectively. Moisture content (%) by mass, ash Na2SO4 process for Bulrush Scirpus acutus carbon, HCl(on dry basis) % by mass, bulk density, specific gravity, process for Leucaena and C. pentandra shell wasteporosity, matter soluble in water, matter soluble in acid, carbon, chloride process for tobacco waste andphenol adsorption capacity, carbon tetrachloride activity, Dolomite process for Pongamia carbon.iron content were analyzed as per standard procedures.Estimation of Na and K was done using Elico Model Iron content is almost uniform for all the fiveFlame Photometer. BET surface area was measured at carbons. This level of iron content will not affect theliquid N2 temperature using Quantachrome Analyzer. effluent water without the problem of iron leaching into Table 1 — Activated carbon from Tobacco stem Sl. No Properties HCl H2SO4 ZnCl2 Na2SO4 Na2CO3 CaCO3 CaCl2 H2SO4 + H2SO4 + NH4S2O8 H2 O2 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 2 12 Surface area, m /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 499 120 the high concentrations (40 mg /l & 60 mg/l), adsorbent 20 mg/L was able to remove 83.5 % of the dye molecules present 100 40 mg/L in the solution.Dye removal, removal 60 mg/L 80Percentage of dye % Conclusions 60 Based on surface area, the following activated 40 carbons/processes are comparable with the commercially available activated carbons: I) Tobacco stem / ZnCl2 20 process; ii) P. pinnata shell / Dolomite process; iii) C. pentandra shell / HCl process; iv) Bulrush S. acutus stem 0 0 50 100 150 200 250 / HCl process; and v) L. leucocephala shell / ZnCl2 Timemin Time, min process. These carbons can be conveniently used for textile effluents removal. In general, all these carbons Fig. 1 — Influence of time on percentage of dye removal- will be efficient for the adsorption of organics as seen concentration variation from adsorption of Rhodamine-B from its solution withtreated water. The level of Na and K content is high L. leucocephala shell.only in the case of tobacco waste carbon. In general, Naand K content are high in sulphate and chloride process Referenceswhen compared to other treatments. Yield of Bulrush S. 1 Cheremisinoff N P & Morresi A C, Carbon Adsorptionacutus carbon prepared by H2SO4 process found high in Applications, Carbon Adsorption Handbook (Ann Arbora vast margin when compared to other carbons. Because Science Pub., Inc: Ann Arbor Michigen) 1980, 1-54. 2 Bansal R C, Donnet J B & Stoeckli F, Active Carbon (Marcelof high charring power of H2SO4, yield of carbon by Dekker, New York) 1988.H2SO4 process shows better result. 3 Mantell C L, Carbon and Graphite Handbook (John Wiley & Surface plays a predominant role for the Sons, New York) 1968.adsorption of solutes from solution. Classification of 4 Lopez-Gonzalez D J, High temperature adsorption ofactivated carbons based on their surface area is as hydrocarbons by activated carbons prepared from olive stones, Adv Sci Technol, 1 (1984) 103-109.follows: Caron I: Tobacco stem, ZnCl 2 > CaCl 2 > 5 Linares-Solano, Lopez-Gonzalez D J, Molina-Sabio M &H2SO4+NH4S 2O 8 > Na2CO3 > H2SO4+H2O2 > HCl> Rodriguez-Reinoso F, Active carbons from almond shells asH2SO4 > Na2SO4 > Dolomite; Carbon II: P. pinnata shell, adsorbents in gas and liquid phases, J Chem Tech Biotechnol,Dolomite > Na2SO4 > Na2CO3 > H2SO4 > H2SO4+ H2O2 30 (1980) 65-72.> H2SO4+NH4 S2O8 > HCl > CaCl2 > ZnCl2 ; Carbon 6 Nasser M M & El-Geundi M S, Comparative cost of colorIII: C. pentandra shell, HCl > Dolomite > Na2SO4 > removal from textile effluents using natural adsorbents, J ChemNa2NO3 > H2SO4 >H2SO4+ H2O2 > ZnCl2 > H2SO4 + Biotechnol, 50 (1991) 257-264.NH4 S2O8 > CaCl2; Carbon IV: Bulrush S. acutus Stem, 7 Bousher A, Shen X & Edyvean R G J, Removal of colored organic matter by adsorption on to low cost waste materials,HCl >CaCl2 > ZnCl2 > H2SO4+ H2O2 > H2SO4 > H2SO4 Water Res, 31 (1997) 2084-2092.+ NH4 S2O8 > Na2CO3 >Na2SO4 > Dolomite; and Carbon 8 Kadirvelu K, Palanivel M, Kalpana R & Rajeshwari S,V: L. leucocephala shell, ZnCl2 > CaCl2 > H2SO4+ NH4 Activated carbon from an agricultural by-product, for theS2O8> Na2CO3 >H2SO4+H2O2 >H2SO4 >Na2SO4>HCl > treatment of dyeing industry wastewater, Biores Technol, 74Dolomite. Surface area of these 5 novel carbons is far (2000) 263-265.better when compared to other carbons. 9 Srinivasan K, Balasubramanian N & Ramakrishna T V, Studies on chromium removal by rice husk carbon, Indian J Environ Activated carbon, prepared from L. Hlth, 30 (1988) 376-387.Leucocephala shell using ZnCl2 process, shows high 10 Rengaraj S, Banumathi A & Murugesan B, Preparation andsurface area and is selected for further studies to analyze characterization of activated carbon from agricultural wastes,its applicability for water treatment purpose. Adsorption Indian J Chem Technol, 6 (1999) 1-4.of Rhodamine-B (Basic Dye) onto activated carbon 11 Banerjee S K, Majmudar S, Roy A C, Banerjee S C & Banerjeeprepared from L. leucocephala shell using ZnCl2 process D K, Activated carbon from coconut shell, Indian J Technol, 14 (1976) 45-49.showed that at low concentration (20 mg/l) of dye 12 Mortley Q, Mellowes W A & Thomas S, Activated carbon fromsolution, adsorbent can remove up to 98.00 % of the materials of varying morphological structure, Thermochin Acta,dye molecules present in the solution (Fig. 1). Even at 129 (1988) 173-186.
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