INTRODUCTION:

Removal of unwanted substances from the waste water is of prime environmental importance the presence of excess amount of undesirable constituents’ causes water pollution; it is established fact that polluted water is harmful to human and aquatic life. There are various adsorbent available for the removal of inorganic and organic substances from the polluted water. Various researchers are reporting low cost adsorbent for pollution control. Acetic acid is used in the manufacturing of vinegar, cellulose acetate, perfumes, and dyes, plastic and pharmaceutical companies. It occurs in fruit juices which become sour as a result of fermentation. It is chief constituents of vinegar. It is corrosive liquid, the vapors are suffocative and causing a damage to lunges.

Various researchers used plant materials as adsorbent, plant materials are used as a cheap and low coast material for adsorption for example modified corn¹ starch, modified onion skins² Saw dust³, Phosphate treated saw dust⁴, water lettuce⁵, algae material⁶ etc. Adsorption of different metal ions^7-8 and organic compound onto solid surfaces has immersed as a promising field of great application value and has been extensively studied in the recent past.

Sunnhemp having family tabiaceae is an important Asiatic plant found throughout the India, Sunnhemp is a bast fiber obtained from the stem.

The ribbon like strands of fibers are very light in colour, lustrous fairly resistant to micro-organisms and moisture with tensile strength. The individual cells of the fiber are cylindrical with surface striation and cross markings. The ends of the cells are irregularly thickened and blanted chemically. The fiber is chiefly composed of cellulose around 80% with relatively thick layer of lignin.

Sunnhemp is essentially a cordage fiber and is thus widely used for ropes, twines, cords, canvas, matting etc.

As the fibers do not deteriorate in water it is suitable for making finishing net. The fiber is also used in the manufacture of cigarette and tissue paper. The stalks and leaves of the plants are used as green or dry fodder for cattles.

MATERIALS AND METHOD:

Acetic Acid, NaOH, Phenolphthalein were supplied by S.D. Fine Chemicals Ltd and were used without any purification.

Preparation of powder:

Filaments of Sunnhemp (Tag). were collected from Harsool reservoir of Aurangabad city. Bold's Basal medium was used for cultivation. Pure filaments were transferred to 200ml liquid medium in 500ml Borosil flask. This procedure was performed under aseptic conditions. The flasks were then incubated under static condition in culture chamber at 25 + 1°C for 15 to 20days. After sufficient growth pure algal sample was harvested and air dried on filter paper in shadow at room temperature. Fine powder of algal sample was prepared in grinder⁹.

The amount of Acetic Acid was determined volumetrically using Phenolphthalein as a reagent. Effect of contact time, temperature, and effect of initial concentration was also determined.

RESULTS AND DISCUSSION:

On the surface of substance there are free valencies. When adsorbate comes in contact with the surface, each velency satisfied by a weak bond formed. The adsorption of solute from solution takes place due to the decrease in the interfacial tension or clue to solid surface acquiring electrostatic charge in solvent. This charged surface of the adsorbent then attain oppositely charged ions from the solution. During the formation of solid such as zeolites gases are evolved and solid becomes porous, such solids can be used as selective adsorbent and can be used for ion exchange. Same logic can be extended to the coal formation. During incomplete burning of algae material CO or CO₂gets evolved and porosity may be formed. Hence charcoal obtains from the plant materials are more effective adsorbent.

In the present paper we want to study the adsorption behavior of acetic acid on the charcoal obtained from plant Plectonema gracillimum (zopf) Hansgirg. It is important to know adsorption capacity of various adsorbent, because adsorption can be used effectively in the prevention of environmental pollution. It is used for the catalytic processes. Langmuir suggested that the forces operated between adsorbate and adsorbent is mostly short range forces, these may be dispersion forces, the orientation forces and induction forces. Dispersion forces arise from attraction between temporary or instantaneous dipoles. The orientation forces appear upon adsorption of polar molecules earring constant electrical charges. Polar molecules tend to orient themselves with their positive poles towards the negatively charged surface or negative poles toward the positively charged surface. The induction forces also play an important role in the adsorption process. The electric charge present on the surface of adsorbent may induce dipoles in the adsorbate molecule their by attracting them. In addition to these forces hydrogen bonds may also takes place which forms interaction between adsorbate and adsorbent.

a) Effect of Contact Time:

It was observed that Sunnhemp (Tag) can be used as a low coast adsorbent effectively. The maximum time required for adsorption is that 20 minutes for 60% adsorption, after that the amount adsorbed remains constant. (Table No.2)

The removal curve was found to be smooth and continuous indicating the formation of monolayer coverage of adsorbent on the other surface of adsorbate. (Table No.4)

Table No.1: ADSORPTION CAPACITIES (Initial Concentration Co = 5.2 gm/ Ltr.)

Mass of Adsorbent	Equilibrium Concentration Ce gm/Ltr.	Log Ce	X=Co-Ce			X/ M	Log X/M	Ce/X/M
250 mg	4.8	0.6812	0.4	80	0.076	1.6	0.2041	3.25
300 mg	4.2	0.6232	1.0	166	0.192	3.33	0.5224	1.56
400 mg	3.8	0.5797	1.4	175	0.269	3.50	0.5440	1.48
500 mg	3.4	0.5314	1.8	180	0.346	3.60	0.5563	1.44
600 mg	2.2	0.3424	3.0	250	0.576	5.00	0.6989	1.04

Table No. 2: Effect of Contact Time

Time (min.)		Ce	q=Co-Ce	qe-q	Log qe-q
5	2.2	4.8	0.4	4.8	0.6812
10	3.1	4.2	1.0	4.2	0.6232
15	3.8	3.8	1.4	3.8	0.5797
20	4.4	3.4	1.8	3.4	0.5314
25	5.0	2.2	3.0	2.2	0.3424

Adsorption Isotherm: -

To study the validity of Freundlich adsorption Isotherm following equation was used

x/m = Kc ^1/n

The linear plot of log x/m Vs logC indicates the applicability of Freundlich adsorption Isotherm (Table No.1). This shows system which exist monolayer coverage of the adsorbent on the other surface of adsorbate. To verify Langmuir adsorption Isotherm I/ Ce is plotted against 1/q the value of 'b' is calculated graphically which is used to calculate the equilibrium parameter R_L

The range 0< R_L<1 reflect favorable adsorption.

In the present study the value of R_L was found to be less than 1 (one). The Langmuir adsorption parameters are very useful for predicting adsorption capacities and also for incorporating into mass transfer relationship. The isotherm can be written as

Ce is the concentration of the adsorbate at equilibrium, Qe is the amount of metal ions adsorbed per .unit weight of the adsorbent, a_L and K_L are Langmuir constants, qi, indicate the intensity of adsorption and K_L = q_Lb_L, where b| is the adsoiption capacity for the present study we obtained a_L = 2. 025 L/mg b_L = 0.041 mg/ grm

The rate of acid adsorption (removal) falls off to give a smooth curve; this part of plot is due to intra particle diffusion the initial portion of the plot can be interpreted by supposing a three step model as follows:

1) Mass transfer of acid from the bulk solution to the particle surface 2) Intra-particle diffusion 3) Adsorption at an interior side

It is assumed that step three (3) is rapid with respect to first two steps¹⁰.

Table No. 3 Thermodynamic Study

Temperature	1/T ×10³	KC	log Kc	∆G(J/Mole)
303	3.30	0.9069	-0.9571	-5552.69
308	3.24	0.8372	-0.9227	-5434.36
313	3.19	0.7209	-0.8573	-5137.84
318	3.14	0.6511	-0.8136	-4953.84
323	3.09	0.5116	-0.7084	-4313.84

The mathematical theory of diffusion is based on Pick's first law, mainly molecular adsorption processes involve diffusive mass transport and the interpretation of overall behavior in terms of two diffusivity and intrinsic equilibrium sorption properties is difficult.

Intra particle diffusion is an important rate controlling step during adsorption process.

Following equations were used to find out adsorption capacity of plant Plectonema gracillimum

Thermodynamic Study:

The experiments were earned out at different temperature to study the effect of temperature on adsorption, thermodynamic parameter such as ∆G, ∆H, and ∆S were determined using following equations (Table No. 3)

Kc = Equilibrium constant, Cad = Amt. of metal ion adsorbed per litre of the solution at the equilibrium, Ce = Equilibrium concentration (mg/1) of the metal in the solution.

KINETICS:

Kinetics study of the adsorption process of Acetic Acid has been studied and it was observed that it obeys Lagergen equation.

Log (Qe-Q) - log Qe - (Kd/ 2.303). t

Qe and Q are the metal ion adsorbed ( mg/g ) at equilibrium and at time.

Intra-particle diffusion was also studied by plotting mass of solute adsorbed Vs square root of contact time the plot was linear. From the slope intra-particle diffusion constant was determined.

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Received on 10.09.2010 Modified on 18.09.2010

Asian J. Research Chem. 4(1): January 2011; Page 156-159-706