Gamma radiation induced modification of cotton waste with...

Atanu Jha, N. K. Goel*, N. Misra, V. Kumar, L. VarshneyRadiation Technology Development Division

Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, INDIA*[E-mail:narenderkumar.goel@gmail.com, Ph: 022-25594763/5689]

Gamma radiation induced modification of cotton waste with MPTAC for Textile dye effluent treatment

Abstract: In the present work, cotton waste is surface modified with [(Methacryloylamino)-propyl] trimethyl ammonium chloride (MPTAC), a strong anion exchanger, byusing gamma radiation induced grafting method. Different grafting parameters, such as total absorbed dose, monomer concentration, solvents, etc., have been investigatedto obtain maximum grafting yield. The PMPTAC-g-Cotton samples were characterized using FTIR, elemental analysis and SEM techniques. Surface modified PMPTAC-g-Cotton samples were investigated as a strong anion exchanger for waste water treatment, particularly for textile dyes effluents. The performance of the grafted anionexchanger was evaluated by adsorption of anionic dyes namely, Acid blue 25 (AB25) under batch process in aqueous solutions. Langmuir isotherm model was utilized toanalyze the equilibrium adsorption data of the dye. Higher correlation coefficient (>0.99) for these dyes suggested that adsorbent follow Langmuir adsorption isotherm andthere is a good agreement between the experimental and calculated values of adsorption capacity. Maximum adsorption capacity was found almost linear function of theextent of grafting. The maximum adsorption capacities of grafted adsorbents (with 20% G.Y.) were found to be 250 mg/g for AB25 at room temperature. The excellent uptakeof organic dyes by the grafted anion exchanger suggested its promising application for industrial wastewater treatment.

Introduction: Surface-modified functional polymers have gained greatimportance in many diverse applications, such as functional adsorbents,antimicrobial and anti-fouling surfaces, support for enzyme immobilization, etc.Surface-modified polymers are of substantial importance in many diverse aspectsof modern technology, and whilst there are a number of existing physical andchemical methods like UV, plasma, conventional chemical methods, enzymatic[1] and most recently laser surface modification for surface modification ofpolymers, the frequent requirement for significant infrastructure, harsh reactionconditions and limitation to specific polymer types led to explore high energyradiation (gamma-ray, electrons beams etc.) based technology known forconvenience, high efficiency, high purity, easy and environmental friendly processfor such modifications. Radiation grafting method has been widely adopted tomodify different polymers to improve their desired physicochemical properties fordifferent applications due to its distinctive advantages over conventional chemical

Characterization : Surface modified samples were characterized with varioustechniques, such as gravimetrically, FTIR, SEM, TGA, Water Uptake and elementalanalysis. Polymer grafted on to cotton fibrils have a nitrogen per unit monomer andhence grafted was confirmed by elemental analysis for nitrogen. As shown in figure3, nitrogen contents were found proportional to the grafting extent. Further, graftedsamples were also characterized with TGA and SEM to investigate the thermalstability and morphological simultaneously after surface modification (Fig. 4 andFig.5).

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different applications due to its distinctive advantages over conventional chemicalgrafting [2]. Cotton is one of the most popular and abundant natural fibres, madeof mainly cellulose. Cotton widely used as clothing materials for its naturalabundance and posses good qualities as good heat conductor, excellentmoisture absorption, good dye ability and biodegradable [3,4]. Thus, radiationgrafting method has been adopted to modify cellulose based fiber to enhance itsphysicochemical properties. It is highly interesting material for research andindustrial purposes because of its renewable, biodegradable and biocompatiblecharacteristics and easy fabrication.Experimental: Locally available cotton fiber waste was used as a substrate.MPTAC monomer (purity >97%) 50% (v/v) from Sigma Aldrich was used asreceived. Mohr’s salt and other chemicals were of AR (Purity >99%) grade. Ultra-pure water was used for preparation of all the solutions. Gamma chamber (GC-5000, BRIT) of effective dose rate 1.7kGy/h was used as a radiation source forradiation grafting purpose.Result and discussions: Various experimental parameters, such as totalabsorbed dose, monomer concentration, solvent effect and acid concentrationwere optimized for achieving maximum grafting levels. The developed graftedmatrix was further tested for the Acid Blue 25 (AB25) model anionic dye for thetextile effluents treatment. Grafting yield was found as a function of totalabsorbed dose and saturated beyond 2kGy (Fig.1). Grafting yield was also foundto be near to linear function of monomer concentration up to 50% as shown in fig.2. Further, effect of additives like Mohr’s salt and acid was not found prominentwhich is generally used for homo-polymer inhibition and accelerating in graftingyield simultaneously.

Dye uptake study: Batch equilibrium adsorption studied was carried out with ananionic dye AB25 as a model dye for the textile effluent treatment. The surfacemodified samples with different extent of grafting yield were dipped for 24hrs understirring conditions in the known concentration of the dye solution. Concentration ofdye was monitored spectro-photometrically at equilibrium. Dye uptake was found toincrease almost linearly with the grafting yield (Fig. 6). MPTAC-g-Cotton adsorbentwith 20% GY was used for dye adsorption study. Maximum adsorption capacity ofthe adsorbent was found ~250mg/g.

Fig.5. SEM images of (a) control and (b) MPTAC-g-Cotton grafted sample Fig.6. Effect of grafting % on dye uptake

Conclusion: Radiation induced grafting is environmental friendly process formodifying the cotton fibrils. Optimized experimental parameters showed the desiredextent of grafting can be obtained. Various characterization techniques confirmed thegrafting reaction and also provided the insight of the morphological and thermalstability of the grafted samples. Radiation grafted MPTAC-g-Cotton was found be anefficient adsorbent for acid dye.References1. A. Bhattacharya, B. N. Misra, Prog. Polym. Sci. 29, 767 (2004)2. N. K. Goel, V. Kumar, Y. K. Bhardwaj, S. Pahan, S. Sabharwal, J. Hazard. Mater. 193, 17 (2011)3. Gowariker, V.R., Viswanathan, N.V., Sreedhar, J., 1999. Individual polymer. In: Gowariker, V.R. (Ed.), Polymer Science. p. 258. 4. Flaque, C., Rodrigo, L.C., Ribes-Greus, A., 2000. J. Appl. Polym. Sci. 76 (3), 326–335

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Fig.4. TGA thermograms of (a)Cotton (b) PMPTAC-g-Cotton and(c) PMPTCA

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Fig. 2. Effect of Monomer Conc. ongrafting yield

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