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Vanadium Removal by Adsorption on Coconut Shell

U.E. CHAUDHARI*
Department of Chemistry, S.R.R.Lahoti Science College, Morshi, M.S., India
Corresponding Author: Dr. U.E.Choudhary, Gayatri Nagar, Warud, Dist. Amravati, M.S.
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Abstract

The studies on removal of vanadium were conducted using coconut shell. Adsorption efficiency has been evaluated. The effect of pH, contact time, adsorbent dose. concentration of metal, particle size and temperature were studied. The results reveals that Langmuir and Freundlich isotherms are followed during adsorption process. Thermodynamics parameter indicate the feasibility of the process. Kinetic studies have been performed to understand the mechanism of adsorption. Column studies have been carried out to compare these with batch capacities.





Keywords

Pentavalent Vanadium, Adsorption, Coconut Shell.

INTRODUCTION

The Twentieth century started with an extensive damage to the natural resources (Tomer, 1999). Unplanned industrilization, urbanization, pollution explosion, change in lifestyle, over exploitation of natural resources, commercial establishment and modern agricultural practices have degraded the quality of environment. The main effects being faced are :
• Continental invasion of air and water.
• Marine pollution through waste discharges.
• Release of variety of chemical and biological contaminants into the water bodies, on land and in air.
• Ground water pollution.
• Acid rains and nuclear fallout.
These effects are not only covering the pollution of environment but also are responsible in creating genetic erosion in plants, animals including human beings and microorganisms. Water is a prime natural resource and is a basic human need. The availability of adequate water supply in terms of its quality and quality is essential for the existence of life.
Water is available in nature as surface water and ground water through the selfpurification mechanisms .like physical, chemical and microbiological processes at natural bodies, are carried out in nature. However, natural water is rarely suitable for direct consumption to human beings. Rapid industrialization and population growth resulted to generation of large quantities of wastewater and causing problem of their disposal. Industrial waste constitutes the major source of various kinds of metal pollution fn natural water. The presence of heavy metals in the enviroment has been of great concern because of their increased discharge, toxic nature and other adverse effects on the receiving streams. When the concentration of toxic metal ions exceed tolerance limit, they may become real health concern (Singh and Lal, 1992). There is an immediate need to introduce cleaner technologies to minimise the pollution and to protect the degarding encironment. It is not possible to achieve zero waste discharge, but it is an essential to treat the waste.
Among the toxic heavy metal ions which are potential health hazards to aquatic animals and human like Pb, Cd, Cr, V, Bi and Mn are important.
The maximum tolerance limit for vanadium for public water supply are 10 mg/L. Toxicity of metal depends on the type of metal, dose and the ionic form. Toxicity of vanadium (WHO, 1998) include rhinitis, blood discharge, an itching and burning sensation in the throat, dry cough with small amount of viscid sputum, general weakness. The moderate toxicity includes respiratory tract infection, bronchitic. bronchopneumonia, Disorder of the nervous system and tremor of the linger and hands. In animals, it affects the kidney, nervous, respiratory, cordiovaschulai and immune system.
Literature survey reveals that, there are many methods namely coagulation, precipitation, ions exchange and adsorption, for removal of vanadium 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.
These cheap and efficient absorbents can carry to cater the need of population in the rural areas and the population in the industrial area where sate drinking water is not available. In the present study, Vanadium (V5+) is removed by using coconut shell (Ayub and Iqbal, 2003) as a adsorbent.

Adsorbent

The coconut shell was first dried at a temperature of 160”C 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°C for 6 hours. The adsorbent was then stored in desiccator for final studied.

Batch study

The dried amount of 0.5 gms of coconut shell was taken in 250 mL reagent bottle and synthetic solution (200 mL) containing various concentration of vanadium ion was added and system is equillibrated by shaking the contents of the flasks at room temperature so that adequate time of contact between adsorbent and final concentration of metal ion vanadium (V) was determined by spectrophotometry using hydrogen peroxide method and measured absorbance at 450 monometer. The spectrophotometer, systronic (model 104) was used to measure the concentration of vanadium (V) ions.

RESULTS AND DISCUSSIONS

Equilibrium adsorption isotherm for Ce verses qe plotted for coconut shell are shown in figure 1. The adsorption capacity in mg/L was calculated then the equation.
qe = (C0 - Ce)V/M where, Co is the initial concentration of vanadium (V) Ce is the concentration of (V) 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 coconut shell for Vanadium. The saturated monoluyer can be represented by :
equation
The lineaiised form of the Langmuir isotherms is
equation
where Q” and b are Langmuir constants. The plot of 1/C, Vs 1/q was found to be linear, indicating the applicability of Langmuir model. The parametrs Q” and b have been calculated and presented in Table 1. The Langmuir constant Q” is a measure of adsorption capacity and b*is the measure of energy of adsorption. In order to observe whether the adsorption. In order to observe whether the adsorption is favourable or not, a dimentionless parameter ‘R’ obtained from Langmuir isotherm is
equation
where b is Langmuir constant and Cm is maximum concentration used in the Langmuir isotherm. The adsorption of Vanadium on Coconut 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
equation
lineaiised form of this equation is
equation
where B & k are Freundlich constants. These constants represent the adsorption capacity and the adsorption intensity respectively.
Plot of log qe Vs log Ce was also found to be linear. The values of B and k are presented in Table l. Since the values of B are less than 1, it indicates favourable adsorption.

Effect of concentration of metal ion and contact time

The responce of Adsorbate dose and contact time on the removal of V( V) 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 then it become constants.

Effect of pH on the removal of vanadium (v)

The effect of pH on the removal of vanadium (V) is shown in Figure[4]. Experiment were conducted at the constant initial vanadium (V) concentration, adsorbent dose (coconut) 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 V(V) is higher at pH = 2 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 Standard Sieves) under optimum condition. It is found that, as the particle size increase the rate of adsorption decrease.

Kinetics of adsorption

0.5 gm of coconut shell and 200 mL V5+ solution was taken in 1000 mL R.B. and shake vigorously 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 spectrophotometi\and were designated as C( and the value of the concentration of the metal ion on the coconut shell at the same time interval estimated using the relation.
equation
The rate of adsorption of V5+ on coconut shell was studied by using the first order rate equation proposed by Lagergren (1998).
equation
where Kad is the rate constant for adsorption. The plote of log Ct Vs t is shown in figure (Lagergren, and Bil 1998).

CONCLUSION

The following conclusions have been drawn from the presents study

1. The percentage retrieval of vanadium is formed to be increase with decrease the initial concentration of vanadium. The removal is found rapid in initial stages followed by slow adsorption upto saturation limit.
2. The developed technique of retrieval of vanadium ions using coconut shell appears to be a cheap and practically viable for the use of semiskilled worker in the villages.
3. The present work on adsorption process is in good agreement with Langmuir isotherm indicating monolayer adsorption process.
4. The result on adsorption process reveals that at pH = 2.0. vanadium uptake capacity is better.
5. The straight lines plots of logC( Vs t 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 adsorbent is very low and it can be disposed of safely.

Tables at a glance

Table icon
Table 1
 

Figures at a glance

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5
Figure 1 Figure 2 Figure 3 Figure 4 Figure 5
 

References





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