The ability of waste banana pith to remove Congo red from aqueous solution

was investigated. Various parameters such as initial dye concentration, contact

time, adsorbent dosage and pH effect were studied. The adsorption rate

constant was found to be 1 X 10.1 min'} at 50 mg I-I dye concentration. Above

92% removal was observed in the pH range 2-11. The removal of dye by banana

pith is mostly due to chemisorption

Kanchana, N.

Namasivayam, C.

Universiti Putra Malaysia Institutional Repository

Pertanika J. Sci. & Techno!. 1(1):33-42 (1993)ISSN: 0128-7680© Universiti Pertanian Malaysia PressRemoval of Congo Red from Aqueous Solutionby Waste Banana Pithc. Namasivayam* and N. KanchanaEnviTOnrnental Chemistry Division, DepaTtrnent of EnviTOnrnental SciencesBhamthiaT University, CoirnbatoTe, Tarnilnadu., India - 641 046Received 9 March 1992.ABSTRAKEksperimen tentang penggunaan sisir batang kayu pisang sebagai penjerapuntuk Congo merah telah dijalankan. Parameter yang dikaji termasuk kepekatanlarutan pewarna, masa tindakan, dos penjerap dan pH larutan. Pemalar kadarpenjerapan ditetapkan sebagai 1 X 10.1 min" pada kepekatan pewarna 50 mg1.1 . Lebih daripada 92% pewarna dijerap pada pH 2-11. Mekasime penjerapansistem pewarna-sisir batang kayu pisang adalah, khususnya, erapan kimia.ABSTRACTThe ability of waste banana pith to remove Congo red from aqueous solutionwas investigated. Various parameters such as initial dye concentration, contacttime, adsorbent dosage and pH effect were studied. The adsorption rateconstant was found to be 1 X 10.1 min'} at 50 mg I-I dye concentration. Above92% removal was observed in the pH range 2-11. The removal of dye by bananapith is mostly due to chemisorption.Keywords: Adsorption, banana pith, Congo red, intra particle diffusionINTRODUCTIONThe textile industry occupies a unique place in the industrial map of Indiaand the total production of cloth from both cotton and synthetic fibres was10527 million metres in 1980 (Badrinath et ai. 1983). Textile mills requirea large volume of water for their processes and the wastewater dischargedfrom the mill is equally large and of a polluting nature. Colour impartsvisible pollution, persists for long distances in streams, decreases re-aeration capacity of the stream, and retards photosynthetic activity. Thetreatment of dyeing wastewater poses several problems as the dyes aregenerally stable to light and oxidation and hence they cannot be treatedby conventional methods of aerobic digestion.The adsorption process provides an attractive alternative especially ifthe adsorbent is inexpensive and readily available. By far, activated carbonhas been the most favoured material for adsorption of various materialslike herbicides, chemical pollutants, dyes etc. (Venkata Rao and Sastry1987). Various other non-conventional adsorbents like Fuller's earth and," Author to whom all correspondence should be addressed.C. Namasivayam & N. Kanchanafired clay, silica (Mckay et al. 1987), biogas residual slurry ( amasivayamand Yamuna 1992a), Fe3+/Cr3+ hydroxide sludge (Namasivayam andChandrasekaran 1990), China clay (Gupta et at. 1989), peat moss and ricehulls ( awar and Doma 1989), coconut husk (Low and Lee 1990) and flyash (Khare et at. 1987; Gupta et at. 1988) have also been reported asefficient adsorbents in removing colour.In India 80% of the population depends on the land for their living.The utilization of agricultural waste is of great significance and can play animportant role in the national economy. India is the second largest bananaproducer after Brazil. It produces about 2.34 million tonnes from acultivated area of 164,000 hectares (Manoharan 1988). The white centralportion of the banana stem, called banana pith, is used to treat personsbitten by poisonous snakes (Pushpangadan et al. 1989). The stems havebeen used for biogas generation (Elorteguri et al. 1987; Sharma et al. 19871989), ethanol production (Tewari et at. 1987) and paper making (Geopaul1980) etc. Mter cutting off the bunch most of the residues are either usedas manure, simply thrown away or burnt off to reduce the volume. Theapproximate amount of dry matter produced per banana plant is about 1,1.3 and 5 g of leaf, pseudostem and fruit respectively (Hegde and Srinivas1991). In order to make the dyeing wastewater treatment economical, it isimperative to go for low cost adsorbents. The aim of this paper is to assessthe ability of waste banana pith to adsorb Congo red from aqueoussolution.MATERIALS AND METHODSWaste banana pith was prepared from the white central portion (bananapith) of banana stems collected from a farm. The banana pith was cut intopieces and dried in sunlight. The powdered waste banana pith was foundto be in the range of 1 mm to 53 II size. Congo red was obtained fromHindustan Ciba-Geigy, Bombay. Tap water was used for the preparation ofdye solutions throughout.Batch adsorption experiments were performed by agitating 1 g ad-sorbent with 100 ml of aqueous Congo red solution at desired initial dyeconcentration for a predetermined time interval at 140 rpm using a shakermachine. The residual dye was removed by centrifugation at 8000 rpm anddye removal was determined by monitoring absorbance changes by meansof Hitachi spectrophotometer (model U-3210).The effect of adsorbent dosage was studied by varying adsorbentdosage from 0.25 to 2.00 g while the dye concentration was maintained at50 mg 1-'. The influence of pH on the adsorption capacity of the adsorbentwas investigated by adjusting the pH of 50 ml dye solution and 50 ml ofwater containing Ig adsorbent using 1:1 HCI or dilute NaOH solutions.Mter equilibration the two solutions were mixed and agitated to equilib-34 Pertanika J. Sci. & Techno!. Va!. 1 No.1, 1993Removal of Congo Red from Aqueous Solution by Waste Banana Pithrium time. Desorption experiments were performed by shaking 1 g of usedadsorbent containing 1.83 mg of Congo red with 100 ml of variousdesorbing media like distilled water, 2N sulphuric acid and 50% (v/v)acetic acid.RESULTS AND DISCUSSIONIn order to find out whether there is any chemical reaction between thedye used and the aqueous extract of waste banana pith, the followingexperiment was carried out. Dye solution and the aqueous extract wereprepared at different levels of pH from 4.81 to 9.23. Absorbances weremeasured before and after mixing the dye solution and the extract. It wasfound that there was no significant change in the absorbances (Table 1).This shows that there is no chemical reaction between Congo red and theaqueous extract of waste banana pith.pH beforetreatment4.815.617.858.419.23TABLE 1Interaction of Aqueous extract of adsorbent with Congo red lAbsorbance at 495.6 nm (Ie max) Abs.ofl:I Afterextract!dye correctionDye Aqueous extract mixture for dilutionof adsorben t factor (3)32(1) (2) (1) + (2) (3)0.39 0.47 0.86 0.44 0.880.55 0.52 1.07 0.55 1.100.58 0.65 1.23 0.62 1.240.59 0.77 1.36 0.66 1.320.59 0.84 1.43 0.69 1.38'Conditions: concentration ofdye, 20 mg 1.1; agitation time, 10 min; weight ofadsorbent, Ig;temperature, 30 ± 2°C.Effect of Contact Time and Initial Dye ConcentrationEffect of contact time and initial dye concentration on adsorption ofCongo red is shown in Fig. 1. The curves are single, smooth and continu-ous, indicating the formation of monolayer coverage on the outer surfaceof the adsorbent (Mckay et al. 1980). The increase in the rate of colourremoval with agitation time may be attributed to a decrease in thediffusion layer thickness surrounding the adsorbent particles (Asfour et at.1985). The time required to reach equilibrium increased considerably asthe initial dye concentration was increased. For an initial dye concentra-tion of 20 mg l-r, saturation was achieved at 10 minutes, where as for thedye concentration of 100 mg 1-1 the time required to reach saturation was140 minutes. A similar trend was observed for the adsorption of Congo redon biogas waste slurry (Namasivayam and Yamuna 1992a).Pertanika J. Sci. & Techno!. Vo!. I No. I, 1993 35C. Namasivayam & . Kanchanao 20 mgr'• 50 mg. 1-1o 75 mg.l-l10 • 100 mg. 1-17 0 0'ICJldlECT<ii>0 4E<1Ja:32o'------;6~0,---~'2:;-;;0,---....,.'..L80,.----2,.L4....,.0--....l3001. min.Fig. 1. Effect ofagitation time and dye concentration on removal ofdye by wastehanana pith; conditions: pH 8.97, 30 ±2 0c.Adsorption DynamicsAdsorption dynamics were studied using various concepts of rate control-ling step. The rate at which the dissolved dye is adsorbed by the wastebanana pith is an important factor for utilization of this adsorbent for theremoval of dyes from wastewater.Adsorption Rate ConstantsThe rate constants for adsorption of Congo red on waste banana pith weredetermined using the following rate expression (Khare et al. 1987).K'log (qe-q) = log qe ---2.303t [1]where qe and q are the amount of dye adsorbed (mg gol) at equilibriumand at time t, respectively. A straight line plot of log (qe-q) vs t shows the36 Pertanika 1. Sci. & Techno!. Va!. 1 No.1, 1993Removal of Congo Red from Aqueous Solution by Waste Banana Pithapplicability of the Lagergren equation (Fig. 2) . Values of rate constantwere calculated from the slope and are presented in Table 2. Maximum K'value of 1.06 X 10-1 min-l was observed for Congo red at 50 mg 1-1. The K'value for the adsorption of Congo red on biogas waste slurry was reportedas 2.8 X 10-2 min-1 (Namasivayam and Yamuna 1992a).The possibility of Congo red being transported within the pores ofwaste banana pith was studied by plotting the amount of dye adsorbed (mgg-1) at different dye concentrations against the tl / 2 (Fig. 3). The doublenature (curved and linear) plots show that the mechanism of adsorptionis complex. The initial curved portion is attributed to boundary layer+ 1.0160120-1e50mg.1-1a 75 mg.1-1.100 mg. Ia40•oo-1.0CTI'"CT0>o~'0>0>E80t. minFig. 2. Lagergren plot for the adsorption of Congu red hy wasl(' hUl/ana pith;conditions: pH 8.97, 30 ±2 "C.TABLE 2Adsorption rate constant for Congo red'Dye concentration,mg }-1Rate constant, K'min-'50751000_1060.0460.022'Conditions: weight of adsorbent, 19; pH 8.97; temperature 30 ± 2"C.PertanikaJ. Sci. & Techno!. Vo!. 1 No. I, 1993 37C. Namasivayam & N. Kanchanaadsorption while the final linear portion is attributed to intraparticlediffusion. Values of rate constant of intraparticle diffusion at 20, 50, 75and 100 mg 1-1 were determined from the slopes of the plots and arepresented in Table 3. The Kp value for intraparticle diffusion was in therange of 0.05 to 0.15 mg g-I min. 1/2 for Congo red at dye concentrationsfrom 20 to 100 mg I-I. Kp value for the adsorption of Congo red on biogaswaste slurry was reported as 0.18 mg g-l min 1/2 at a dye concentration of50 mg 1-1 (Namasivayam and Yamuna 1992a).o 20 mg 1-1• 50mg ,-1o 75mg 1-1.100mgr11012I0'10'1EUQJ.0....oVl.0IIIC 4::Jo~ 2~r-e---------0L....------:--4 ------18-------112----.116t li2 min. lizJFig. 3. Amount ojdye adsorbed (mg dye per g adsorbellt) versus tll2 jor the intraparticletransport ojCongo red by waste banana pith; conditions: pH 8.97, 30 ± 2 "C.TABLE 3Rate Constan ts for In traparticle Diffusion of Congo Red]Dye concentration,mg 1-1Rate constants, Kpmg g'] min 1/22050751000.100.0460.1530.154lConditions: weight of adsorbent, Ig; pH 8.97; temperature 30 ±2"C.38 Pertanika J. Sci. & Techno!. Vo!. 1 No.1, 1993Removal of Congo Red from Aqueous Solution by Waste Banana PithEffect of Adsorbent DosageThe Freundlich plot was employed to plot the adsorption isotherm(Gupta et al. 1989)xlog -- = log k + 1/n log Cem[2]where x is the amount of dye adsorbed (mg 1-1), m is the weight of theadsorbent used (g 1-'), Ce is the equilibrium concentration of the dye insolution (mg I-I) and k and n are constants incorporating all the factorsaffecting the adsorption process such as adsorption capacity and intensityof adsorption. In general, as the k value increases the adsorption capacityof the adsorbent for a given dye increases (Manjunath and Indu Mehrotra1981). The linear plots for log xlm Vs log Ce (Fig.4) show that the dyeCongo red obeys Freundlich isotherm. k and n values calculated from theintercept and the slope were found to be 1.46 and 1.21, respectively. Valueof 1 < n < 10 represents beneficial adsorption (McKay et at. 1982). The kand n values for the adsorption of Congo red on biogas waste slurry werereported as 1.2 and 1.5 respectively (Namasivayam and Yamuna 1992a).o 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6log Ce, mg. 1-1Fig. 4. Freundlich plot for adsOIption of Congo red by waste bonana pith;conditions pH 8.97, 30 ±2 "C.Pertanika J. Sci. & Techno!. Vo!. I o. I, 1993 39C. Namasivayam & N. KanchanaEffect of pHThe effect of pH on the percentage removal of dye is shown in Fig. 5. pHhas no significant effect on the percentage removal of the dye. Above 92%removal was observed in the entire pH range from 2 to 11. It was reportedthat above 90% removal of Congo red by biogas waste slurry occurred inthe pH range 2 to 9.4 (Namasivayam and Yamuna 1992a).65.--'0>oiE 4c~ 2E<t:---... • • • • .---..-oL------'-4-----.l-a--------I'2pHFig. 5. Removal ofCongo red by waste banana pith as afunction ofpH (mg per g adsorbentversus pH); conditions: dye concentration, 50 mg (I adsorbent 1g, 30 ±2 ·C.Desorption StudiesDesorption studies aid in elucidating the mechanism of adsorption of dyeson the adsorbent. The extent of desorption of Congo red with distilledwater, 2 N sulphuric acid and 50% (v/v) acetic acid was found to be 5.56,1.67 and 1.85% respectively. The small amount of desorption in distilledwater indicates the occurrence of physisorption to a small extent involvingweak bonds. The weak desorption in 2N sulphuric acid rules out thepossibility of ion exchange. A small percentage of desorption in 50%acetic acid indicates that the dye seems to be held by the adsorbent, mostlyby chemisorption.CONCLUSIONBanana pith has considerable potential as an adsorbent for the removal ofdyestuffs from waste waters. The removal of Congo red was above 92% in40 Pertanika J. Sci. & Techno!. Vol. 1 No.1, 1993Removal of Congo Red from Aqueous Solution by Waste Banana Piththe pH range of 2 to 11. The treated water is still coloured due to theaqueous extract of banana pith. Since the wastewater after treatment isrich in macro and micro nutrients due to the extract of banana pith it canbe used for irrigational purposes.REFERENCESAsFO R, H.M., M.S. EI- FEUNDl, OA FADALI and M.M. NASSAR. 1985. Equilibrium studieson adsorption of basic dyes on hard wood. j. Chern. Tech. Bio Tech. 35A: 21-28.BADRINATH, S.D., V. RAMAN and V. ARUMUGAM. 1983. Upgrading an existing wastewatertreatment for textile industry - A case study. IA V\PC Tech. 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Removal of Congo Red from Aqueous Solution

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Removal of Congo Red from Aqueous Solution by Waste Banana Pith

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