1. INTRODUCTION:

Dyes may also be problematic if theyare broken down unaerobically in the sediments, as toxic amines are often produced due to incomplete degradation by bacteria¹. Synthetic dyes have a complex aromatic structure which provides them physiochemical, thermal, biological, and optical stability². Literature also reports the removal of dyes such as malachite green³ crystal violet, methyl red, eriochrome black T, deorlene, saffranine red⁴. acidorange-7, acid red-88, acid blue 113, and methyl violet by different available adsorbents, such as silica and alumina⁵.

A large number of dyes are commercially available. These are released from Industrial Effluents of dyes and other related industries. It is estimated that approximately 21% of the dye stuffs are lost in industrial effluents during manufacturing and processing operations. M. Auta, B.H. Hameed, reported the Preparation of waste tea Nitrated biomass⁶. Using potassium acetate as an activating agent for adsorption of Acid Blue 25 dye. The O. Tunc, H. Tanacı, Z. Aksu has been studied the Potential use of cotton plant wastes for the removal of black B reactive dye⁷. V.K.Gupta, D.Pathania, S.Agarwal, P.Singh, reported the Adsorptional photo catalytic degradation of methylene blue onto pectin-Cu -Sn a nanocomposite⁸. under solar light. Various physical, chemical and biological methods, including adsorption, biosorption, coagulation/flocculation, advanced oxidation, ozonation, membrane filtration and liquid–liquid extraction have been widely used for the treatment of dye-bearing wastewater. The A.A. Kale has been reported study sieved agro waste of Cicer Arientinum⁹. The B.H. Hameed, M.A.M. Salleh, D.K. Mahmoud, W.A. Karim, A. Idris, worked on Preparation, characterization and evaluation of adsorptive properties of orange peel based Nitrated biomass¹⁰. Via microwave induced K2CO3 activation. The advantages and disadvantages of every removal technique have been extensively reviewed. Highly colored wastes are not only esthetically unpleasant but also hinder light penetration and may disturb the ecosystem. Moreover, dyes itself fare toxic to some organism. Methylene blue (MB) is a cationic dye having various applications in chemistry, biology, medical science and dyeing industries. Its long term exposure can cause vomiting, nausea, anaemia and hypertension.K.Y. Foo, studied removal of dyes in an economic way^11-12. Remains an important issue for researchers and environmentalists. Adsorption is a very effective separation technique in terms of initial cost, simplicity of design, ease of operation and insensitive to toxic substances. V.K. Gupta showed the Application of low-cost adsorbents¹³ for dye removal. Nitrated carbon is the most efficient adsorbent used for dye removal. But it is expensive to produce and regenerate. A. A. Kale. Biosorption of Hg2+ions by Sulphonated biomass of Stalks of Prunus cerasus¹⁴ Nitrated biomass of Prunus cerasus was used for this study. Nitrated biomass of Prunus cerasus to develop a new low cost Nitrated carbon and study its application to remove methylene blue dye from aqueous solution. Kinetics, thermodynamic studies and adsorption isotherm models were investigated to evaluate experimental data.

2. MATERIALS AND METHODS:

2.1. Adsorbent:

The biomass of Prunus cerasus was collected from the locally available garden. The stalks of Prunus cerasus were dried washed with distilled water to remove adhered impurities from its surface. The dried biomass was crushed, milled and sieved to 100m particle size. The dried biomass was soaked with Conc. HNO3 for period of 6 h and the resulting reaction mixture was kept overnight in fume hood. The reaction mixture was repeatedly washed with cold water till to complete remove acid and filtered to obtain Nitrated carbon. This is then dried in oven at 100⁰C for12 hr. The resulting Nitrated carbon of prunus cerasus was preserved and used as an adsorbent for MB removal.

2.2. Adsorbate:

Methylene blue (C₁₆H₁₈N₃SCl.₃H₂O) was obtained from E. Merck, India and was used for sorption study. The solution of required concentration was prepared by dissolving the required amount of MB dye in distilled water.

2.3. Experimental:

The batch adsorption experiments were conducted in a set of 250ml of Erlenmeyer flask containing adsorbent and 100ml of MB solution with various initial concentrations. The flasks were agitated in an isothermal water-bath shaker at 100rpm and 27⁰C until the equilibrium is reached. After decantation and filtration, the equilibrium concentrations of dye in the solution were measured at 665nm using UV-visible spectrophotometer. The pH of solution was adjusted with 1N HCl and 1N NaOH solutions. The amount of dye adsorbed and percentage removal of MB were calculated using Eqs. (1) and (2), respectively:

Where:

qe amount of dye in mg per gram of adsorbent. Ci and Ce are respectively initial concentration and equilibrium time of MB (mg/l).V volume of solution. M mass of adsorbent.

2.4. Adsorption isotherm:

2.4.1. Langmuir isotherm:

The Langmuir (1916) sorption isotherm¹⁵ is applied to equilibrium sorption assuming monolayer sorption onto a surface with a finite number of identical sites. constitution and fundamental properties of solids and liquids. The Langmuir equation is written as

The shape of this isotherm can also be expressed in terms of separation factor (RL), which is given as follows⁶:

Where KL is Langmuir constant (L/mg) related to the affinity of binding sites and the free energy of sorption. qe is dye concentration at equilibrium onto bio sorbent (mg/g). Ce is dye concentration at equilibrium in solution (mg/l). qm is dye concentration when monolayer forms on biosorbent (mg/g).

2.4.2. Freundlich isotherm:

The A.E. Nemr, W.O. Abdel, E.S., AmanyA. Khaled, (2009) Removal of direct blue-86 from aqueous solution by new Nitrated biomass. developed from orange peel ¹⁶. The Freundlich equation for heterogeneous surface energy systemsshown by is given by Eq. (5).

The KF and n are Freundlich constants, determined from the Plot of ln qe versus ln Ce. The parameters KF and 1/n are related to sorption capacity and the sorption intensity of the system. The magnitude of the term (1/n) gives an indication of the favorability of the sorbent/adsorbate systems. P.K. Malik Used the Nitrated biomass, Prepared from sawdust¹⁷ and rice-husk for sorption of acid dyes: a case study of acid yellow 36.

2.4.3. Tempkin isotherm:

X.S. Wang, Y. Qin. (2005) Equilibrium sorption isotherms for of Cu2+ on rice bran.¹⁸ The linearized Tempkin equation is given by the following equation.

T is the absolute temperature in Kelvin, R is the universal gas constant (8.314 J/mol K), and b is the Tempkin constant related to heat of sorption (J/mg). The Tempkin constants a and b are calculated from the slope and intercept of qe versus ln Ce.

3. RESULT AND DISCUSION:

3.1. Removal of MB:

3.1.1. Effect of adsorbent dose and initial dye concentration.:

The adsorbent doses varied from 0.1 to 0.9g/50ml. It is evident that the MB removal increased sharply with an increase in the adsorbent concentration from 0.1/100 to 0.5g/100 ml. This may be due to the availability of more adsorbent sites as well as greater availability of specific surfaces of the adsorbents (Figure1). Further increase in dye concentration showed no significant changes in removal efficiency with increased dye concentration, the driving force for mass transfer also increases. At low concentrations there will be unoccupied active sites on the adsorbent surface. Above optimal MB concentration, the active sites required for the adsorption of dye will lack. N. Barka, S. Qouzal, A. Assabbane, A. Nounhan, Y.A. Ichou (2011). Removal of reactive yellow 84 from aqueous solutions by adsorption onto hydroxyapaite¹⁹. AndJ. Iqbal, F.H. Watto., M.H. Watto, S.R. Malik, S.A. Tirmizi, M. Imran, and A.B. Ghangro (2011) Adsorption of acid yellow dye onflakes of chitosan prepared from fishery waste²⁰.

3.1.2. Effect of contact time:

The effect of contact time on the removal of MB is shown in Figure 2 and about 85% dye removal takes place in 60 min by prunus cerasus. The equilibrium was reached after 80 minutes (Figure 2).

The changes in the rate of adsorption might be due to fact that initially all the adsorbent sites are vacant and solute concentration gradient is very high. Later, the lower adsorption rate is due to a decrease in number of vacant sites of adsorbent and dye concentrations. The decreased adsorption rate, particularly, toward the end of experiments, indicates the possible monolayer formation of MB on the adsorbent surface.The E.L. Abd, M.M. Latif, A.M Ibrahim (2009). Adsorption, kinetic and equilibrium studies on removal of basic dye from aqueous solutions using hydrolyzed oak sawdust²¹. This may be attributed to the lack of available active sites required for further uptake after attaining the equilibrium.

3.1.3. Effect of PH:

The pH of a dye solution is an important influencing factor for the adsorption of MB onto of prunus cerasus Figure 3 shows the effect of pH on adsorption onto of prunus cerasus. The maximum MB removal was observed at pH 8. The ions when dissolved in water. Thus, in acidic medium the positively charged surface of sorbent tends to oppose the adsorption of the cationic adsorb ate. When pH of dye solution is increased the surface acquires a negative charge, there by resulting in an increased adsorption of cationic MB due to an increase in the electrostatic attraction between positively charged dye and negatively charged adsorbent.

3.1.4. Effect of dye concentration.:

The effect of dye concentration on the sorption of MB onto of prunus cerasus was carried out in the concentration range of 10–70mg/100ml. Equilibrium adsorption capacity increased with an increase in MB concentration from 50mg to 50ml. Further increase in dye concentration showed no significant changes in removal efficiency (Figure 4). This is due to the fact that with increased dye concentration, the driving force for mass transfer also increases. At low concentrations there will be unoccupied active sites on the adsorbent surface. Above optimal MB concentration, the active sites required for the adsorption of dye will lack. This retards the overall MB adsorption by Nitrated carbon.

3.1.5. Effect of Temperature:

The effect of temperature is an important influencing factor for the adsorption of MB onto of prunus cerasus Figure 5. Shows the effect of temperature on adsorption onto of prunus cerasus. The maximum MB removal was observed at about 45⁰C.

3.2. Adsorption kinetics:

The pseudo first order rate expression is given as:

Where, qe and qt are the amount of dye adsorbed on sorbent at equilibrium and time t (mg/g) and k1 is the first order rate constant (min^_1). A plot of log (qe^_qt) versus t gives a linear relationship, from which the value of k1and qe can be determined from the slope and intercept. The linearized form of pseudo second order rate expression is given as

where qe is the amount of adsorbate adsorbed per unit mass of sorbent at equilibrium (mg/g), qt is the amount of adsorbate adsorbed at contact time t (mg/g) and k2 is the pseudo second order rate constant (g/mg min). A plot of t/qt versus t gives a linear relationship, from which qe and k2 can be determined from the slope and intercept.The data for the adsorption of MB on of prunus cerasus were applied to pseudo first and pseudo second order kinetic models and the results are presented in Table-1. kinetic model (0.9907) is greater than for first order kinetic model (0.9638) (Table-1, Figure6). This confirmed that the rate limiting step is chemisorptions, involving valence forces through sharing or exchange of electrons. The K.G. Bhattacharyya, A. Sharma, (2005) Kinetics and thermodynamics of methylene blue sorption on neem (azadirachta indica) leaf powder²². The intraparticle diffusion equation is expressed as follows:

Where, kd is the intraparticle diffusion rate constant (mg/g min1/2). The data for intraparticle diffusion are given in Table-1. The linear portion of the plot does not pass through origin. This deviation from the origin may be due to the variation of mass transfer in the initial and final stages of the adsorption process. This confirms that the adsorption of MB on of prunus cerasus was a multi-step process involving adsorption on the external surface and diffusion into the interior. K.V. Kumar, A. Kumaran, (2005) Removal of Methylene blue by mango seed kernel powder²³.

3.3. Adsorption isotherm.:

Adsorption capacity and other parameters were evaluated using Langmuir, Freundlich and Tempkin isotherm models. It has been observed that the sorption capacity (qm) was found to be 40.10mg/g (Table- 2). The high value of correlation coefficient 0.9907 (Fig-6) indicates the applicability of Langmuir isotherm which assumes a monolayer coverage and uniform activity distribution on the sorbent surface. In the present study, RL values (0 <RL <1) favour the adsorption of MB onto of prunus cerasus (Table- 2). Eq. (5) was used to evaluate Tempkin isotherm. The value of correlation coefficient R² obtained from Temkin isotherm was found to be 0.9762 constant b is related to heat of sorption indicating physio–chemical nature of the sorption process. The equilibrium data were also fitted to the Freundlich equation. The parameters KF and n indicated the sorption capacity and the sorption intensity of the system. The magnitude of the term (1/n) gives an indication of the favorability of the sorbent/adsorbate systems. The correlation coefficient value (0.946) is lower than Langmuir and Tempkin values. Therefore, adsorption onto prunus cerasus does not follow Freundlich isotherm closely.

3.4. Adsorption thermodynamics:

Thermodynamic parameters evaluated for MB adsorption onto prunus cerasus are the free energy change (DG°), enthalpy change (∆H⁰) and entropy change (∆S⁰). These parameters were calculated using the following equation.

Where qe is MB concentration at equilibrium onto prunus cerasus (mg/L), R is universal gas constant (8.314 J/mol K), and Ce is MB concentration at equilibrium in solution (mg/L). The values of ∆H⁰ and ∆S⁰ were determined from the slope and intercept of the plot of ln KD versus 1/T. (Figure7). Gibbs free energy change of sorption (DG°) was calculated using Eq. (11). The adsorption of dye increases rapidly with an increase in temperature. The increase in adsorption capacity of prunus cerasus was attributed to the enlargement of pore size and activation of the sorbent surface with temperature. Further rise in temperature increases the mobility of the large dye ions and reduces the swelling effect thus enabling the large dye molecule to penetrate further. The results also indicated that the adsorption of MB is an exothermic process. Thermodynamic parameters (∆H⁰, ∆S⁰and ∆G⁰) for MB. Adsorption was evaluated using Eqs. (10)– (12). The values of ∆H⁰ and ∆S⁰ were determined from the slope and intercept of the plot of ln KD versus 1/T (Figure 7). Table 2 shows the thermodynamic parameters for MB adsorption of prunus cerasus. The calculated values of ∆H°, ∆S° and ∆G° were found to be -31.177 kJ/mol^-1, +0.1099 KJ/mol^-1 and -63.9722 KJ mol^-1 respectively. The negative value of ∆H⁰ (-31.177 kJ/mol^-1) indicates that the Adsorption of MB onto of Prunus cerasus is an exothermic reaction. The calculated value of ∆G° -63.9722 KJ mol^-1 indicates spontaneous nature of the adsorption process. Further the positive value of entropy change, ∆S⁰ reflects the affinity of prunus cerasus for MB dye. Y.S. Ho, G. McKay, D.A.J., Wase, C.F. Foster (2000). Study of the sorption of divalent metal ions on to peat²⁴.

4. CONCLUSION:

In this work of prunus cerasus shows promising adsorption capacity for methylene blue removal. The maximum sorption for MB solution concentration (0.05 g/100ml), sorbent dosage (0.5g/100ml), contact time (80 min) and temperature (303 K) were observed. The maximum removal of methylene blue dye was attained at pH 8.0. The equilibrium data were fitted well in the Langmuir, Freundlich and Tempkin isotherm models which confirmed that the sorption is heterogeneous and occurred through physico–chemical interactions. The rate of sorption was found to obey pseudo-second order kinetics and intraparticle diffusion model with correlation coefficient value R² is 0.9907. The negative DG° values indicated that the sorption of dye onto biosorbent was feasible and spontaneous. The negative ∆H⁰value depicted exothermic nature of the sorption. The parameters KF and n indicated the sorption capacity and the sorption intensity of the system.

5. ACKNOWLEDGEMENTS:

I Dr. A.A. Kale sincerely thankful to head dept of chemistry Prof. A.B. Nikumbh and Principal Dr. K.G. Kanade for providing me infrastructural facility to carry my research work.

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Received on 29.03.2021 Modified on 30.04.2021

Asian Journal of Research in Chemistry. 2021; 14(4):242-246.

DOI: 10.52711/0974-4150.2021.00041