Current World Environment

Introduction

• Continental invasion of air and water.
• Marine pollution through waste discharges.
• Release of variety of chemical and biological contaminates into the water bodies, on land and in air.
• Ground water pollution.
• Acid rains and nuclear fallout.

metal ions from aqueous medium. However, adsorption is an easy and economical process for removal and retrieval of cation from aqueous medium. Efficiency of adsorption process mainly depends on nature of adsorbent, adsorbate, pH, concentration, temperature, time of agitation etc.

The cheap and efficient adsorbents can carry to cater the need of population in the rural areas and the population in the industrial area where safe drinking water is not available. In the present study, Lead (II) is removed by using Ferronia elefuntum Fruit^4-8 as a adsorbent.

Adsorbent

The Ferronia elefuntum Fruit Shell was first dried at temperature of 160^oC for 6 hours. After grinding it was sieved to obtain average particle size of 200 mesh. It was then washed several times with distilled water to remove dust and other impurities. Finally it was dried again in an oven at 50^oC for 6 hours. The adsorbent was then stored in desiccator for final studies.

Batch Study

The dried amount of 0.5 gms of Ferronia elefuntum Fruit Shell was taken in 250 ml reagent bottle and synthetic solution (200 ml) containing various concentration of Lead (II) ion was added and system is equilibrated by shaking the contents of the flasks at room temperature so that adequate time of contact between adsorbent and final concentration of metal ion. Lead (II) was determined by spectrophotometry⁹ using Dithizone method at 515 nm against a reagent blank. The spectrophotometer, systronic model 104) was used to measure the concentration of Lead (II) ions.

Equilibrium adsorption isotherm for C_e verses q_e, plotted for Ferronia elefuntum Fruit Shell are shown in figure 1. The adsorption capacity in mg/L was calculated then the equation.

Qe= (Co -Ce ) V/M



C_e is the concentration of Lead (II) at equilibrium in mg/L V is the volume of solution in litre and M is the mass of adsorbent in grams

Adsorption Isotherms

Equilibrium isotherms was studied for both Langmuir and Freundlich isotherms. The results are shown in figure 2 and 3 which illustrate the plot of Langmuir and Freundlich isotherms of Ferronia elefuntum Fruit Shell for Lead (II). The saturated monolayer can be represented by:

The linearised from of the Langmuir isotherm is Where, Q⁰ and b are Langmuir constants. The plot of 1/C_e Vs 1/q_e was found to be linear, indicating the applicability of Langmuir model. The parameters Q⁰ and b have been calculated and presented in Table 1. The Langmuir constant Q⁰ is a Measure of adsorption capacity and b is a measure of energy of adsorption. In order to observe whether the adsorption is a favourable or not, a dimensionless parameter ‘R’ obtained from Langmuir isotherm is.

R = (1 + b × Cm)^-1

Where, b is Langmuir constant and Cm is maximum concentration used in the Langmuir isotherm. The adsorption of Lead (II) on Ferronia elefuntum Fruit Shell is a favourable process as ‘R’ values lie between zero to one. Coefficients of co-relation (r) are also shown in Table 1. The applicability of Freundlich isotherm was also tried using the following general equation: 

linearised form of this equation is log q_e = B.log C_e + log k.

Where, B and k are Freundlich constants. These constants represent the adsorption capacity and the adsorption intensity respectively.

Plot of log q_e Vs log C_e was also found to be linear. The values of B and k are presented in Table 1. Since the values of B are less than 1, it indicates favourable adsorption.

Results and Discussion

The response of Adsorbate dose and contact time on the removal of Lead (II) is presented in figure (I). The observations reveal that an increase in the adsorbate dose, rate of adsorption increase upto certain level and then it become constant. Also as the time of contact increase, adsorption increase and them it become constants.

Effect of pH on the Removal of Manganese (II)

The effect of pH on the removal of Manganese (II) is shown in Figure [4]. Experiment were conducted at the constant initial Lead (II) concentration, adsorbent dose (Ferronia elefuntum Fruit Shell) of 0.5 gm/100 ml and the contact time of 4 hours. The pH of the aqueous solution is an important controlling parameter in the adsorption process. It was observed that the percentage removal of Lead (II) is higher at pH = 5 and then decrease with increase of pH.

Effect of Particle Size

The adsorbent particle size has significant influence on the kinetics of adsorption. The influence of particle size furnishes important information for achieving optimum utilisation of adsorbent. Four particle size 50, 100, 150, 200 micron size (Indian StandardBSieves) under optimum condition. It is

q_e  = k.C_e

found that, as the particle size increase the rate of adsorption decrease. 

Kinetics of Adsorption

0.5 gm of Ferronia elefuntum Fruit Shell and 200 ml Pb⁺⁺ solution was taken in 1000 ml R. B. and shake vigoriously for about four hours. After every 15 minutes, 5 ml sample of the solution was withdrawn for the first hour and subsequently the interval between the samples withdrawn was increased to 30 minutes. The concentration of the metal ions in the sample, withdrawn were determined by the spectrophotometry and were designated as C_t and the value of the concentration of the metal ion on the Ferronia elefuntum Fruit Shell at the same time interval estimated using the relation.

Table 1: Isothermal constants

Figure 1: Equilibrium adsorption isotherm for Ferronia elefuntum fruit shell-Pb++ Click here to view figure

Figure 2: Langmuir adsorption isotherm Click here to view figure

Figure 3: Freundlich adsorption isotherm Click here to view figure

Figure 4: Effect of pH on% removal of Pb++ Click here to view figure

Figure 5: System-Ferronia elefuntum fruit sheel - Pb++ Click here to view figure

1. formed to be increase with decrease the initial concentration of Lead (II). The removal is found rapid in initial stages followed by slow adsorption upto saturation limit.
2. The developed technique of retrieval of Lead (II) ions using Ferronia elefuntum Fruit Shell appears to be a cheap and practically viable for the use of semiskilled workers in villages.
3. The present work on adsorption process is in good agreement with Langmuir isotherm indicating monolayer adsorption process
4. The results on adsorption process reveals that at pH = 5.0, Lead (II) uptake capacity is better.
5. The straight lines plots of log C_t versus time for the adsorption show the validity of Lagergren equation and suggest the first order kinetics
6. ​​​​​​​Regeneration studies are not necessary with the view that the cost of the adsorption is very and it can be disposed of safely.

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