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Journal of Chemistry & Applied Biochemistry

Research Article

Natural Clay -An Adsorbent for Basic Dye

Ekta Khosla

Department of Chemistry, Hans Raj Mahila Maha Vidyalaya, Jalandhar, Punjab, India


Corresponding author: Ekta Khosla, Department of Chemistry, Hans Raj Mahila Maha Vidyalaya, Jalandhar, Punjab, India; E-mail: ekta1999@gmail.com


Citation: Khosla E. Natural Clay -An Adsorbent for Basic Dye. J Chem Applied Biochem. 2016;2(1): 118.


Copyright © 2016 E Khosla . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Submission: 11/01/2016; Accepted: 27/01/2016; Published: 01/02/2016


Abstract


The adsorption behaviour of Basic Red-12 on Vermiculite and has been investigated to understand the physicochemical process involved and to explore the potential use of low cost materials in textile effluent treatment and management. The adsorption process was found to be pH dependent and optimum pH obtained is 8.0. The equilibrium was established in 2 h and Pseudo first order kinetics was followed. The process obeys Langmuir and Freundlich model. Scanning electron microscopic analysis reveals a conspicuous surface morphology of VC. The results of XRD and FTIR spectroscopy reveal that the process is electrostatic complexation mechanism driven. The thermodynamical measurements suggest that all processes are exothermic accompanied with negative ΔGo, ΔHo and ΔS o.


Keywords: Vermiculite; Basic Red-12; Isotherms; Thermodynamics

Introduction


Dyes constitute the focus of much of environment concernnow a days. Dyes are used in many industries like textile, paper,leather, plastics, cosmetics, pharmaceuticals etc. These industriesuse a considerable amount of water for dyeing and their effluentmainly consist of colored waste water. Color is the first observableparameter for checking the quality of water and according to WHOrecommendations the water used for drinking purpose should becolorless. In industrial waste water color is the first apparent pollutant. The presence of very small amount of color hampers the penetration of sunlight and affects aquatic flora and fauna. The presence of dyes impart excess organic load in waste water. Around 10,000 different types of dyes are available worldwide with an annual production of 7x105 metric tonnes [1].


This is observed that aerobic biodegradation has very less colorremoval efficiency. Most of the treatment technologies work onbiological treatment processes. Other physical and chemical methodslike coagulation [2,3] oxidation, [4] membrane separation, [5] andadsorption are in practice. Adsorption is a procedure of choice dueto its simplicity, efficiency and cost efficacy [6]. Activated carbon isthe best adsorbent but its higher cost and difficult regeneration has encouraged many workers for the research of new adsorbents. Ionicdyes have been removed by the use of adsorbents like orange andbanana peels [7], almond shells [8], corn cob [9], de-oiled soya [10],shale oil ash [11], Sugar cane bagasse [12], coir pith [13], hazelnutshells [14], rice husk [15], wheat husk [16], Baggase [17], bark [18] etc.


Natural clays are abundant on most of the continents of the world.Clay materials possess layered type of structure and they are classifiedon the basis of their layered structures. These clays are much cheaperthan activated carbon. Alkan et.al [19] investigated the removal ofreactive blue 221 and acid blue 62 anionic dyes onto sepiolite fromaqueous solutions. The adsorption capacity of sepiolite increasedwith increasing temperature and decreasing pH. The sepiolite samplecalcinated at 200 °C has a maximum adsorption capacity. However,calcination at higher temperature caused a decrease in the adsorptioncapacity. It was found that the Freundlich isotherm appears to fitthe isotherm data better than the Langmuir isotherm. Yuan et.al[20] investigated the adsorption of methylene blue and neutral redover ordered mesoporous carbons. Theoretical studies showed thatthe adsorption kinetics of dyes on ordered mesoporous carbonswas well depicted by using pseudo-second-order kinetic model.Wang et.al [21] evaluated the efficiency of natural zeolite for theremoval of malachite green in batch system. Kinetic studies indicate that malachite green adsorption on the natural zeolite in a singlecomponent system follows the first-order kinetics. Dogan et.al [22]investigated the removal of reactive dyes over surfactant modifiedzeolite. The adsorption of reactive black 5 and reactive red 239 inaqueous solution on cetyl trimethyl ammonium bromide (CTAB)modified zeolite was studied in a batch system. Experiments wereperformed at different conditions such as initial dye concentration,contact time, temperature and pH. CTAB modification covered thezeolite surface with positive charges and the adsorption capacityof zeolite increased. The adsorption capacity of reactive red 239was found to be two times higher than reactive blue 5 due to thehydrophilicity of the dye molecules.


In the present work Natural clay Vermiculite has been used asan Adsorbent for Basic Dye ‘Basic Red-12’ for study of adsorptionparameters and for studying thermodynamics of the adsorptionprocess.


Materials and Methods


Materials and Chemicals


Vermiculite (VC) a 2:1 type aluminosilicate clay mineral wasobtained from Tamil Nadu Minerals limited, Dharampuri. This wascrushed and finally powdered and particle size < 0.5mm was separatedfor adsorption study. This was activated by washing with DDW andfiltration using vacuum pump and drying at 353 K for 24h and storedin air tight container for further study. The dye Basic red 12(C.I. BasicRed 12) (molecular weight 357.51), molecular formulaC25H29N2Cl (1,3, 3-Trimethyl-2-[3-(1, 3, 3-trimethyl-2-indolinylidene) propenyl]-3-indoliumchloride was purchased from Thomas Baker company andwas used without further purification. The FTIR of VC and surfacederivatives was carried out with Perkin Elmer spectrophotometerin the range 400-4000 cm-1 using perkin elmer spectrophotometer.The pH of dye solutions and pHzpc were determined by using pHmeter by Toshvin (TMP-85). The weighing were carried out ona digital weighing balance of accuracy up to 0.1 mg by citizen Co.Shimadzu 2101 PC UV –Visible spectrophotometer was used forthe determination of residual dye concentration in the medium.The sample was also characterized by X-ray diffractometry using anX’PERT PRO PANalytical with Cu-Kα radiation.


Adsorption Studies


The series of experiments were conducted by placing 50 mlof dye solution in an Erlenmeyer flask and adding the requiredamount of adsorbent to that in an incubator shaker. The pH ofdifferent solutions was adjusted with 0.1 N HCl and 0.1 N NaOH.After attainment of equilibrium the aqueous phase was analyzedfor residual dye concentration using UV visible spectrophotometer.From the absorbance data qe (mg g-1) was determined using eq 1.


     

Where C 0 is initial dye concentration, Ce is final dye concentrationand V is volume of dye in liters and W is mass of adsorbent in g.The isotherms were studied by using 50 ml of dye solution withinconcentration range of 200 ppm to 500 ppm for VC at 303 K, 313 Kand 323 K.


Results and Discussions


Structure of VC


The SEM of VC suggests a compact and less porous arrangementof ions in the adsorbent (Figure 1). Surface chemistry of theadsorbents such as specific surface area, pore volume distribution andpore diameter were measured. Pore volume was determined by thetechnique. The zero point charge of the adsorbents and derivativeswas determined by solid addition technique. The results of the surfacearea analysis, pore volume, bulk density and pHzpc reveals that thesurface area of VC is 65.213 m2/g, with pore volume 4.160 cm3/g, bulkdensity 2.46 g/ml and pHzpc 2.5. Generally, larger the surface area,higher is the adsorbent’s capacity. However, the surface area must beavailable in certain pore sizes. The pores on adsorbents are classifiedby IUPAC as micropores, macropores, and transitional pores. Themicropores have diameters of 10-100 Ao, pores larger than 1,000 Aoare considered as macropores and pores with diameters in the rangeof 100 to 1,000 Ao are defined as transitional. The large pores servemainly as passageways to the smaller pores where the adsorptionforces are stronger.


Figure 1: SEM of Vermiculite at magnification 1800x (15kV).


The FTIR spectra of VC suggests the main bands at 1020 cm-1 and1080 cm-1due to Al-O bond stretching, the bands are also observed at3500 and 3400 cm-1 due to O-H bonds in VC (Fig. not shown here).


The XRD spectra confirm crystalline structure of VC. (Figure 2).


Figure 2: XRD Spectra of VC.


Effect of adsorbent dose


To investigate the effect of adsorbent dose on adsorption of dyeon VC, the experiments were conducted with adsorbent dose between2.5 g/100 ml to 20.0 g/100 ml at 303 K and it was found that with an increase in the dose, the adsorption increases. A significant increaseis observed at optimum adsorbent dose i.e. 10g/100 ml. The resultshave been shown in Figure 3.


Figure 3: Effect of Adsorbent dose.


Effect of pH


Surface change is the most important parameter for ionic dyeadsorption. The dye adsorption is affected by solution pH and in thepresent study the effect of pH is studied in the range of 2-9 whileinitial concentration (500 ppm), adsorbent dose (7.5 g/100 ml) andtemperature (303 K) were kept constant. The adsorption capacity increases when the pH increases for VC. The maximum adsorptionof basic dyes occurs at pH 8 due to negative charge on surface inalkaline medium (Figure 4).


Figure 4: Effect of pH on Dye Removal.


Adsorption isotherms


The Freundlich [23] and Langmuir [24] isotherm models havebeen successfully applied to adsorption processes at temperatures303 K, 313 K and 323 K and thermodynamic parameters calculatedaccordingly. For the equilibrium concentration of adsorbate (Ce)and amount of dye adsorbed at equilibrium (qe), the following linearforms of Langmuir and Freundlich isotherms were studied.


     

     

Where Qo and b are Langmuir constants and KF and n areFreundlich constants. The Freundlich and Langmuir isotherms gavestraight lines and intercepts and slopes were used to determine thevalues of Freundlich and Langmuir parameters as given in Table 1 and Table 2. The isotherms are shown in Figure 5.


Figure 5: Freundlich adsorption Isotherm and Langmuir adsorption isotherm for adsorption of BR-12 on VC.


Table 1: Freundlich Parameters for Adsorption of BR-12 over VC.


Table 2 Langmuir Parameters of Adsorption of dye on VC.


     

     

     

Where b, b1, b2 are Langmuir constants at 303 K, 313 K and 323K respectively.


To check the validity of isotherms on adsorption data regressioncoefficient ‘R’, Standard Estimated error ‘SEE’ and Random sum ofsquares ‘RSS’ are also calculated by using SPSS software.


The value of Kf is increasing with the rise of temperature for BR-12, The value of n is in the range 1.00-2.00. The adsorption of dye ionson micro crystals of VC reveals different adsorption mechanisms.This seems that the increase of concentration of dye ions causesincreased diffusivity with the rise of temperature, thus the values ofintercepts and slopes are also increasing with the rise of temperature.The self diffusion and transport diffusion steps are operating and thisleads to molecular redistribution of dye ions on VC after binding withionic dyes.


The Langmuir adsorption isotherm fits well on the adsorptionof ionic dye on VC. The values of R, SEE and RSS suggest thatthis isotherm model fits on the adsorption of BR-12 on VC. Theapplicability of Langmuir adsorption model reveals these ionic dyesbinds with the aluminosilicate materials to form a chemical bond.The interlayer spacing between the silicate sheets makes possibility ofbinding of ionic dyes with alumiosilicate minerals.


The Thermodynamics of adsorption of BR-12 on VC has beendeterdetermined (Table 3). The adsorption of BR-12 on VC specify that thess is energetically favourable. The adsorption process is enthalpydriven as the entropy of the process decreases after incorporation ofdye idye ion in inter layers of aluminosilcate structure of VC.


Table 3: Thermodynamics of the adsorption process.


Adsorption Kinetics


Adsorption kinetics depends upon the adsorbent-adsorbateinterface and system condition, the adsorption kinetics has been investigated for their suitability and application in water pollutioncontrol. Two vital appraisal elements for adsorption processoperation unit are the mechanism of adsorption and the reactionrate. Dye uptake rate determines the dwelling time required forcompleting the adsorption process till attainment of equilibrium,which can be catalogued from kinetic analysis. The first order rateexpression of Lagergren based on the solid adsorption capacity isgenerally expressed by equation 7.


     

The integrated form of above equation can beexpressed by equation 8.


     

Where qe and qt are the amount of dye adsorbed at equilibriumand time t (min) respectively, k1, the rate constant of pseudo-firstorder rate constant (min-1). The kinetic parameters have been shownin Table 4. The adsorption of dye on VC fitted the Lagergren equationwell with high regression coefficient and less standard estimatederror.


Table 4: Lagergren Pseudo first order kinetics data for dye interactions on VC.


Conclusion


VC is natural clay and has been used as an adsorbent for theremoval of basic dye and it has been found that Clays can be usedwithout much chemical modification for the removal of basicdyes from effluent. The Increase in adsorbent dose increases theadsorption efficiency due to increase in active sites on the surfaceof adsorbent. The pH and temperature are important factors fordeciding the adsorption efficiency of material. The zero point chargeof VC is below 7.0, thus it acts as an efficient adsorbent at that pH.The Freundlich isotherm fits better than Langmuir suggestingphysisorption as a mode of adsorption. Thermodynamic parametersindicate exothermic nature of the process.


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