A cheaper adsorbent has been prepared from carbon slurry waste obtained from National Fertilizer Limited (NFL), Panipat and investigated for the removal of congo red, an anionic dye. Its adsorption on prepared carbonaceous adsorbent was studied as a function of contact time, concentration and temperature. The results have shown that carbonaceous adsorbent adsorbs dye to a sufficient extent (272mgg-1). A comparative study of adsorption results with those obtained on activated charcoal shows that the carbonaceous adsorbent is ~95% efficient as compared to activated charcoal. Thus, it can be fruitfully used for the removal of dyes from wastewater

Bhatnagar, A.

Jain, A.

Mukul, M.

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Environ Chem Lett (2005) 2:199–202DOI 10.1007/s10311-004-0097-0O R I G I NA L PA P ERA. Bhatnagar · A. K. Jain · M. K. MukulRemoval of congo red dye from water using carbon slurry wasteReceived: 18 October 2004 / Accepted: 24 November 2004 / Published online: 22 December 2004 Springer-Verlag 2004Abstract A cheaper adsorbent has been prepared fromcarbon slurry waste obtained from National FertilizerLimited (NFL), Panipat and investigated for the removalof congo red, an anionic dye. Its adsorption on preparedcarbonaceous adsorbent was studied as a function ofcontact time, concentration and temperature. The resultshave shown that carbonaceous adsorbent adsorbs dye to asufficient extent (272 mg g-1). A comparative study ofadsorption results with those obtained on activated char-coal shows that the carbonaceous adsorbent is ~95% ef-ficient as compared to activated charcoal. Thus, it can befruitfully used for the removal of dyes from wastewaters.Keywords Carbon slurry waste · Congo red dye ·Adsorption · Batch and kinetic studiesIntroductionWater shortage is a worldwide problem that is furtherexacerbated by serious water pollution (Zhou 1999). Theavailability of clean water for various activities is be-coming the most challenging task for researchers andpractitioners worldwide. The problem is particularly se-rious for developing countries for three main reasons.First 40% of the world’s population lives in arid andsemiarid lands primarily in Asia and Africa, whereoverpopulation intensifies the problem of water shortage.Secondly, water wastage is a serious problem in manydeveloping countries, in agriculture as well as in industrywhere outdated technologies are still widely used in-volving excessive water consumption.A further problem is that water supplies are beingpolluted by various chemicals including dyes. Dyes areimportant water pollutants which are generally present inthe effluents of textile, leather, paper and dye manufac-turing industries. The worldwide high level of productionand extensive use of dyes generates colored wastewaterswhich cause water pollution. The colored dye effluentsare generally considered to be highly toxic to the aquaticbiota and affect the symbiotic process by disturbing thenatural equilibrium through reduced photosynthetic ac-tivity due to the coloration of water in streams. Some dyesare reported to cause allergy, dermatitis, skin irritation,and cancer in humans. Thus, the removal of dyes fromeffluents before they are mixed up with unpolluted naturalwater bodies is important.Amongst several wastewater treatment technologies,adsorption is the most versatile process and widely used(Faust and Aly 1987), for the pollutants removal fromwastewaters. Activated carbon is mainly used as adsor-bent in the adsorption processes currently in use. How-ever, its widespread applications in wastewater treatmentare restricted due to higher cost. In view of the importanceof pollution control, efforts have been directed towarddeveloping low cost alternative adsorbents. With this aim,various waste materials as low cost adsorbents (Pollard etal. 1992) have been investigated for the removal of toxicsubstances from wastewaters. These materials tend toremove more inorganic contaminants as compared to or-ganics. But none has emerged as a sufficiently efficientalternative to activated carbon.In the present communication, carbonaceous adsor-bent, prepared from carbon slurry waste of the fertilizerindustry, was tested as adsorbent for dyes with a modelsystem of congo red solutions. Congo red (1-naphthale-nesulphonic acid, 3,30-(4,40-biphenylenebis(azo))-bis(4-amino) disodium salt) is a benzidine based dye whichis known to metabolize to benzidine, a known humanThis work has been presented at the National Symposium onBiochemical Sciences: Health and Environmental Aspects(BSHEA—2003), Agra, India (2003).A. Bhatnagar ()) · A. K. Jain · M. K. MukulDepartment of Chemistry,I.I.T. Roorkee,Roorkee, 247667, Indiae-mail: amit_b10@yahoo.co.inA. BhatnagarPresent address: Swiss Federal Institute for Environmental Scienceand Technology (EAWAG),Ueberlandstrasse 133, Duebendorf 8600, Switzerlandcarcinogen. Exposure to the dye has been known to causean allergic reaction and possibly, anaphylactic shock(Bhattacharyya and Sharma 2004). The results obtainedare compared with those on standard activated charcoal inorder to assess the efficacy of the prepared adsorbent.ExperimentalMaterials and solutionsCongo red was procured from B.D.H. (India). All the reagents usedwere of A.R. grade. Double distilled water was used throughoutthese investigations.Preparation of the carbonaceous adsorbentIn India, carbon slurry is produced as a waste in fertilizer plantsusing fuel oil [Low Sulphur Heavy Stock (LSHS)] as a feed stock.It was treated (Srivastava et al. 1987) with H2O2 to oxidize theadhering organic material and then washed with distilled water anddried. The thermal activation of dried material was done at 500C(as at this temperature, maximum porosity was observed) in amuffle furnace for 1 h in the presence of air. After activation, theash content was removed by treating the material with 1M HCl andwashed with distilled water and dried. The yield of the finishedproduct was found to be ~90% and it is now called ‘carbonaceousadsorbent’. Different mesh sizes were obtained after sieving andkept in a desiccator for further use. Some important characteristicsof carbonaceous adsorbent used are: surface area = 380 m2g-1;carbon content = 89.8%; methylene blue number = 90; iodinenumber = 330.Adsorption studiesBatch method was used to study the adsorption on the preparedcarbonaceous adsorbent. For this, a fixed amount of the adsorbent(0.01 g) was added to 10 ml of dye solution of varying concen-trations taken in 50 ml stoppered glass tubes, which were placed inthermostat cum shaking assembly. The solutions were stirredcontinuously at constant temperature for 2 h to achieve equilibrium.The concentration of the dye in the residual solutions was subse-quently analyzed spectrophotometrically at lmax of 497 nm. The pHof all solutions in contact with adsorbent was found to be in therange 5.5–6.5.Results and discussionEffect of contact time and concentrationPreliminary experiments were carried out in order toevaluate the contact time needed by the systems to reachequilibrium. The results are shown in Fig. 1. It is seenfrom Fig. 1 that dye removal seems to occur in twophases. The first phase involved rapid dye uptake in thebeginning and 50% adsorption is completed within 15min followed by the subsequent removal of the dye whichcontinued for a longer period. Figure 1 also indicates thatthe time required for equilibrium adsorption is 1.5 h. Thusfor all equilibrium adsorption studies, the equilibrationperiod was kept under 2 h. Further, the time required toachieve a definite fraction of equilibrium adsorption wasfound to be independent of initial concentrations. Similarobservations were also reported by other workers (Pootset al. 1978), and indicate a first-order process.Adsorption isothermsIn order to determine the efficacy of the prepared car-bonaceous adsorbent, the equilibrium adsorption studieswere carried out and the adsorption isotherms are shownin Fig. 2. It is seen from the figure that the adsorptioncapacity of the adsorbent for congo red is 272 mg g-1.In order to assess the efficacy of the carbonaceousadsorbent, the results of congo red dye adsorption werecompared with standard activated charcoal sample (E.Merck) and incorporated in Fig. 2. It is seen that car-bonaceous adsorbent is about 95% as efficient as standardactivated charcoal in removing congo red and therefore,can be fruitfully employed for dye removal fromwastewaters.Effect of temperatureIn order to understand the effect of temperature on theadsorption of dye, experiments were also conducted at45C and the results are shown in Fig. 2. A comparison ofFig. 1 Effect of contact time on uptake of congo red on carbona-ceous adsorbentFig. 2 Adsorption isotherms of congo red on carbonaceous ad-sorbent at different temperatures and on activated charcoal200adsorption isotherms at 25 and 45C shows that adsorp-tion decreases with an increase in temperature indicatingthat the process is exothermic in nature. The adsorptiondata was further analyzed and found to conform best tothe following Langmuir equation with good correlationcoefficients varying from 0.999 to 0.995.1qe¼ 1qmþ 1qm bCeð1Þwhere qe is amount adsorbed at equilibrium concentrationCe, qm is the Langmuir constant related to maximummonolayer capacity and b is the Langmuir constant re-lated to energy of adsorption. The plots between 1/qe and1/Ce for the adsorption of congo red were drawn in Fig. 3.The values of monolayer capacity (qm) were found to be272 mg g-1 at 25C and 167 mg g-1 at 45C. Further,equilibrium constant (b, in l mol-1) have been evaluatedfrom the intercept and slope of these plots and were foundto be 9.1x104 and 5.5x104 at 25 and 45C, respectively.Monolayer capacity (qm) of the adsorbent for the dye iscomparable to the maximum adsorption (Fig. 1) obtainedfrom adsorption isotherms.The influence of adsorption isotherm shape has beendiscussed (Weber and Chakravorti 1974) to know whetheradsorption is favorable or not in terms of RL, a dimen-sionless constant referred to as the separation factor orequilibrium parameter. RL is calculated using the fol-lowing equation:RL ¼ 11þ bC0 ð2ÞThe values of RL calculated as per the above equation.As the RL values lie between 0 and 1 (3.2x10-4 and5.2x10-4 at 25 and 45C, respectively), the adsorptionisotherm is favorable.The free energy change (DG), enthalpy change (DH)and entropy change (DS) were calculated using the fol-lowing equations:DG ¼ RT lnðbÞ ð3Þlnb2b1 ¼ DHR1T2 1T1 ð4ÞDG ¼ DH  T DS ð5Þfor the adsorption process in order to know the nature ofadsorption. The free energy change (DG) was found to benegative with the values 28.3 and 28.9 kJ mol-1 at 25 and45C, respectively, whereas entropy change (DS) valuesare positive and 28.5 and 28.6 J mol-1K-1 at 25 and 45C,respectively. Further, enthalpy change (DH) of thepresent adsorption system was found to be negative withthe value 19.9 kJ mol-1. These values indicate that theadsorption process is spontaneous and exothermic. Fur-ther, positive DS values indicate the affinity of the ad-sorbent for the dye.Dynamic modelingThe kinetics of adsorption is important from the point ofview that it controls the process efficiency. Various ki-netic models have been used by various workers anddifferent systems conform to different models but theLagergren’s rate equation (Lagergren 1898), is the onemost widely used (Panday et al. 1985; Haribabu et al.1993) for the sorption of a solute from a liquid solution.Thus this first-order equation:logðqe qÞ ¼ log qe kads2:303t ð6Þwhere qe and q are amount of dye adsorbed at equilibriumand at time t, in mg g-1 respectively, and kads is the first-order rate constant, was applied to the present studies ofdye adsorption. As such, the values of logðqe qÞ werecalculated from the kinetic data of Fig. 1 and plottedagainst time. The plots so obtained are found to be linearwith good correlation coefficients varying from 0.999 to0.995 indicating that Lagergren’s equation is applicable tothe dye adsorption on carbonaceous adsorbent and theadsorption process is a first-order process. The first-orderrate constant calculated from the plots is found to be2.08x10-4 min-1.Treatment of effluent of a local dyeing unitThe effluent was obtained from a local dyeing factoryusing various commercial dyes for dyeing purposes ofvarious textiles. This dye wastewater is characterized by adark brown color, a pH of 10.3 and Chemical OxygenDemand (COD) value of 860 mg l-1. The absorptionspectra shows that the dye wastewater has four lmaxvalues at 264.0, 473.0, 550.0 and 831.0 nm with absor-bance of 11.1, 25.7, 12.3 and 0.18 at 264.0, 473.0, 550.0and 831.0 nm, respectively. The treatment of this dyewastewater for dye removal was carried out by passing itthrough a column (cross sectional area: 0.9 cm2; height:3.1 cm; mass: 1.0 g) of carbonaceous adsorbent, of par-ticles of size 50–200 mesh, at a flow rate of 2.5 ml min-1.Fig. 3 Langmuir adsorption isotherms of congo red on carbona-ceous adsorbent at different temperatures201The monitoring of the column was done spectrophoto-metrically at lmax values of the solution. For this purpose,a 10 ml aliquot was collected and absorbance determined.It was observed that effluent coming out of the columnhad almost nil absorbance at all the lmax values upto atotal volume of 130 ml. After that, the color starts ap-pearing and absorbance increased. This means that acolumn of 1 g of carbonaceous adsorbent, as used by uscan treat 130 ml of dye wastewater. The COD of thetreated dye wastewater was within acceptable limits.Thus, the results show that 1 kg of prepared carbonaceousadsorbent can treat 130 l of the dye wastewater obtainedfrom the local dyeing factory. It is therefore, reasonable toconclude that the prepared adsorbent can be fruitfullyused as an alternative adsorbent for treating dyewastewater.ConclusionsThe adsorptive capacity of carbonaceous adsorbent for thecongo red dye is sufficient (272 mg g-1), and is about 95%of the adsorptive capacity of standard activated charcoal.This adsorbent, being a low cost (~US$ 0.1 kg-1) material,can, therefore, be used fruitfully for the removal of dyesfrom wastewaters. As the carbonaceous adsorbent hasshown significant adsorption potential, its columns weresuccessfully used for the removal of effluent of a localdyeing unit. In view of the low cost of this material, theregeneration of the exhausted material need not be done,and it can be disposed of by burning. Further, the presentadsorption system is a first-order process.ReferencesBhattacharyya KG, Sharma A (2004) Azadirachta indica leafpowder as an effective biosorbent for dyes: a case study withaqueous congo red solutions. J Environ Manage 71:217–229Faust SD, Aly OM (1987) Adsorption process for water treatment.Butterworths Publishers, StonehamHaribabu E, Upadhya YD, Upadhyay SN (1993) Removal of phe-nols from effluents by fly ash. Int J Environ Stud 43:169–176Lagergren S (1898) About the theory of so-called adsorption ofsoluble substances K. Svenska Vetenskapsad Handl 24:1–39Panday KK, Prasad G, Singh VN (1985) Copper(II) removal fromaqueous solutions by fly ash. Water Res 19:869–873Pollard SJT, Fowler GD, Sollars CJ, Perry R (1992) Low-costadsorbents for waste and wastewater treatment: a review. SciTotal Environ 116:31–52Poots VJP, McKay G, Healy JJ (1978) Removal of basic dye fromeffluents using wood as an adsorbent. J Water Pollut ControlFed 50:926–935Srivastava SK, Pant N, Pal N (1987) Studies on the efficiency of alocal fertilizer waste as low cost adsorbent. Water Res21:1389–1394Weber TW, Chakravorti RK (1974) Pore and solid diffusion modelsfor fixed-bed adsorbers. J Am Inst Chem Eng 20:228–238Zhou JL (1999) Treating China’s water crisis. Chem Ind 19 April1999202

Removal of congo red dye from water using carbon slurry waste

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Removal of congo red dye from water using carbon slurry waste

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