Removal of methylene blue by mango seed kernel powder

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Abstract

Batch experiments were carried out for the sorption of methylene blue onto mango seed kernel particles. The operating variables studied were initial solution pH, temperature, adsorbent mass, initial dye concentration and contact time. Equilibrium data were fitted to Freundlich and Langmuir isotherm equation and the equilibrium data were found to well represented by Langmuir isotherm equation. The monolayer sorption capacity of mango seed kernel for methylene blue sorption was found to be 142.857 mg/g at 303 K. The sorption kinetics was found to follow pseudo first order kinetic model. The methylene blue uptake process was found to be controlled by both surface and pore diffusion with surface diffusion at the earlier stages followed by pore diffusion at later stages. The average effective diffusion coefficient was calculated and found to be 5.66 × 10−4 cm2/s. Analysis of sorption data using Boyd plot confirms that the external mass transfer as the rate limiting step in the sorption process. Various thermodynamic parameters such as enthalpy of sorption ΔH, free energy change ΔG and entropy ΔS were estimated. The positive value of ΔH and negative values of ΔG shows the sorption process is exothermic and spontaneous. The positive value of entropy ΔS shows the increased randomness at the solid–liquid interface during the sorption of dye ions onto mango seed kernel particles.

Introduction

The removal of color from dye bearing effluents is one of the major problem due to the difficulty in treating such wastewaters by conventional treatment methods. The most commonly used method for color removal are biological oxidation and chemical precipitation. However, these process are effective and economic only in the case where the solute concentration are relatively high. Currently sorption process is proved to be one of the effective and attractive processes for the treatment of these dye-bearing wastewaters [1], [2], [3], [4], [5]. Also this method will become inexpensive, if the sorbent material used is of inexpensive material and does not require any expensive additional pretreatment step. In the present study mango seed kernel, a waste material obtained from mango juice manufacturing industry have been used as adsorbent for the removal of methylene blue from its aqueous solution. Methylene blue is selected as a model compound in order to evaluate the capacity of mango seed kernel for the removal of dye (methylene blue) from its aqueous solutions. Methylene blue has wider applications, which include coloring paper, temporary hair colorant, dyeing cottons, wools, coating for paper stock, etc. Though methylene blue is not strongly hazardous, it can cause some harmful effects. Acute exposure to methylene blue will found cause increased heart rate, vomiting, shock, Heinz body formation, cyanosis, jaundice, quadripelgia and tissue necrosis in humans. Previously several researchers had proved several low cost materials such as pear millet husk carbon [6]; Aspergillus niger [7]; rice husk [8]; hair [8]; cotton waste [8]; bark [8]; perlite [9]; carbonized press mud [10]; bagasse bottom ash [10]; raw kaolin [11]; pure kaolin [11]; calcined raw kaoline [11]; calcined pure kaoline [11]; NaOH treated raw kaolin [11]; coir pith [12]; guava seeds activated carbon [13]; iron humate [14]; neem sawdust [15]; clay [16]. In the present study mango seed kernel have been used as an adsorbent for the removal of methylene blue from its aqueous solutions. In the present study the effect of initial methylene blue concentration, fly ash mass, initial dye solution pH and contact time on the amount of color removal have been investigated. Also the sorption of methylene blue at solid–liquid interfaces have been studied extensively at equilibrium and various thermodynamic behaviors have been investigated. Further the kinetics and the mechanistic steps involved in the sorption process were also evaluated.

Section snippets

Materials

The ripened fruits of Mangifera indica (Mango) were collected from the local juice manufacturing industry and seeds were separated from the fruit. The hard seed coat was removed and the seeds were sun dried. These dried seeds were coarsely powdered using domestic mixie and the particle size in the range of 60–85 mesh (BSS) were used as adsorbents for the present study.

The dye used in all the experiments was methylene blue, a basic (cationic) dye. The dye methylene blue was obtained from BDH

Effect of pH

Fig. 1 shows the effect of pH on amount of dye adsorbed qe (mg/g). Where qe was obtained from the mass balance equation given by:qe=(C0Ce)VMwhere, C0 (mg/L) and Ce (mg/L) is the concentration in the solution at time t = 0 and at equilibrium time, V is the volume of solution treated and M is the amount of biomass added (g). From the Fig. 1, it was observed that the solution pH affects the amount of dye adsorbed. The dye uptake was found to increase from with increasing pH and it increases from

Conclusions

The present study shows that the mango seed kernel, a waste biomaterial generated in juice factories can be used as an adsorbent for the removal of methylene blue from its aqueous solutions. The amount of dye sorbed was found to vary with initial solution pH, adsorbent dose, contact time and temperature. The amount of dye uptake (mg/g) was found to increase with increase in solution temperature and contact time and found to decrease with increase in adsorbent dosage. The sorption data were

Acknowledgements

Thanks are due to the reviewers for their inspiring suggestions.

References (29)

  • M. Dogan et al.

    Removal of methyl violet from aqueous solutions by perlite

    J. Colloid Interface Sci.

    (2003)
  • Y.S. Ho et al.

    The kinetics of sorption of basic dyes from aqueous solutions by sphagnum moss peat

    Can. J. Chem. Eng.

    (1998)
  • G. McKay et al.

    Surface mass transfer process using peat as an adsorbent for dyestuffs

    Can. J. Chem. Eng.

    (1980)
  • B.S. Inbaraj et al.

    Evaluation of a carbonaceous sorbent prepared from Pearl Millet Husk for its removal of basic dyes

    J. Sci. Ind. Res.

    (2002)
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