INTRODUCTION:

Interest in biodegradable polymers has been growing at a very fast rate as our society becomes increasingly sensitive to the harmful side effects of the traditional applications of such chemicals. Great pressure is being put on researchers to device a way of implementing biodegradable polymers into waste management¹.

Applications of synthetic polymers were mostly based on their relative inertness to the elements and their biodegradation in comparison with natural macromolecules such as cellulose and proteins. In recent years many important applications require biodegradable polymers. Successful applications include sutures, surgical implants, agricultural mulches and controlled release formulations of drugs and agricultural chemicals.

The nature of the chemical structure of the polymer determines the biodegradability whereas the physical properties of the polymer affect the rate of biodegradation. Biological systems degrade large natural molecules such as starch, cellulose, proteins etc. by hydrolysis followed by oxidation. Polymer based on such molecules have been synthesised recently^6,7.

Most of the known biodegradable polymers contain hydrolysable groups along the polymer main chains. Only a few high molecular weight carbon chains containing polymers are biodegradable². Polysaccharides react with small carboxylic acids to produce derivatives that are biodegradable.^3,4

experimental:

In the present work the B.O.D. and C.O.D. method of biodegradation was used⁵. The determination of B.O.D. involves the determination of the dissolved oxygen used by microorganisms in the biochemical oxidation of organic matter. To ensure that meaningful results, the sample was suitably diluted with specially prepared dilution water so that adequate nutrients and oxygen were available during the incubation period. Normally several dilutions were prepared to cover the complete range of possible values.

The dilution water was seeded with a bacterial culture that has been acclimated to the organic matter present in the water. The seed culture that was used to prepare the dilution water for BOD test was a mixed culture of a large number of saprophytic bacteria and other organisms that oxidized the organic matter. The incubation period was 10 days at 20^oC. The temperature was constant throughout the test. After incubation, the dissolved oxygen of the sample was measured and the B.O.D. was calculated using formula (1)

B.O.D. in mg/gm = {(D₀ - D₁)} - {(C_o - C₁)} x (decimal fraction of sample used)

.... (1)

Where,

D₀ = Dissolved oxygen in sample on 0 day.s

D₁, D₂……, D₁₀ = D.O. in sample on 1^st, 2^nd,………… 10^th day respectively

Co = D.O. in blank on 0 day

C₁, C₂, ...C₁₀ = D.O. in blank on 1^st, 2^nd, ...10^th day respectively

Preparation of dilution water

Required quantity of distilled water was taken and aerated at 20^oC with clean compressed air. 1 ml of CaCl₂, MgSO₄, FeCl₃ and phosphate buffer solution per litre of the above distilled water was added and mixed thoroughly. This standard dilution was prepared just before the use. The addition of small measured volume of water containing a good bacterial population to the dilution water is called seeding. In this experiment acclimated seeds are used for B.O.D.

Pre -Treatment method

Necessary quantity of 1 normal H₂SO₄ or 1 N NaOH was added in the sample to bring the pH in a range of 6.5 to 8.5. Sample was thoroughly shaken just before dilutions were made. Series of dilutions for a sample were made such that at least three of the dilutions should deplete 20% to 90% of initial D.O. The C.O.D. value was treated as guideline for the purpose of dilution.

The prepared dilution water was transferred into one litre graduated cylinder until it was half full, without any air entrapment. Then appropriate quantity of sample was added into the cylinder without producing any air bubbles. The volume was then made up using dilution water and mixed well with glass rod without any air entrapment. The two BOD bottles were filled carefully without any air bubbles inside it. The bottles were stoppered and the other dilution of sample were prepared in similar manner. Similarly standard dilution water was taken into BOD bottle and stoppered it after filling completely.

One set of entire series of dilution prepared was utilized for immediate determination DO and kept the other set in a BOD incubator maintained at 20ºC for 1, 2, 3..........10 days. After 1st day to 10th day the D.O. and concentration of all the incubated sample of the set was determined.

Preparation of Seed

Bacteriological seed was brought from biological reactor of food industry and preserved at 37ºC in laboratory. The seed was activated by adding nutrients, phosphate buffer, dextrose and ammonium chloride in sufficient quantity. It was then aerated for 48 hours and multiplied and activated seed was inoculated to dilute resin sample taken for B.O.D. analysis. By making above changes in the selection of seeds, BOD experiments were carried.

Chemical Oxygen Demand⁵

Chemical oxygen demand was determined by refluxing the sample with a known excess of potassium dichromate in a 50% H₂SO₄ solution in presence of AgSO₄ (as catalyst) and HgSO₄ (to eliminate interference due to chloride). The organic matter of the sample was oxidized to water, CO₂ and NH₃. The unreacted dichromate in the solution was titrated with a standard ferrous ammonium sulphate (FAS) solution. The COD of the sample was calculated using equation (2)

.... (2)

(B-S) ml x 8 x 1000

COD in mg/l =

Where B and S are the volumes of FAS run down in the blank and test experiments respectively and X is the volume of sample taken for the test.

RESULTS AND DISCUSSION:

The polymers synthesized in laboratory as batch 1,2 and 3, showed the HLB ratio as 12, 12.39 and 11.88. This values are well within the range so that the polymers can be used in detergent formulation (Table 1).

Table 1. Hydrophilic- Liphophilic balance

Sr. No.	Polymer Batch	H.L.B.	Remarks
1	1	12	Suggests Its Use in detergent formulation
2	2	12.39	Suggests Its Use in detergent formulation
3	3	11.88	Suggests Its Use in detergent formulation

Table 2. BOD and COD Analysis of Batch 1

Sr. No.	Particulars	Concentrations (mg/g)
Sr. No.	Particulars	BOD at 20⁰C	COD	BOD: COD
1	After 1^st Day	113207	10,88,000	0.1040
2	After 2^nd Day	169811	--	0.1560
3	After 3^rd Day	311320	--	0.2861
4	After 4^th Day	424528	--	0.3901
5	After 5^th Day	509433	--	0.4682
6	After 6^th Day	679245	--	0.6243
7	After 7^th Day	849056	--	0.7803
8	After 8^th Day	1245283	--	1.14
9	After 9^th Day	1075471	--	0.9884
10	After 10^th Day	1018867	--	0.9364

Table 3. BOD and COD Analysis of Batch 2

Sr. No.	Particulars	Concentrations ((mg/g))
Sr. No.	Particulars	BOD at 20⁰C	COD	BOD: COD
1	After 1^st Day	104803.49	970305.67	0.1080
2	After 2^nd Day	209606.98	--	0.2160
3	After 3^rd Day	393013.10	--	0.4050
4	After 4^th Day	445414.84	--	0.4590
5	After 5^th Day	563318.77	--	0.5805
6	After 6^th Day	576419.21	--	0.5940
7	After 7^th Day	589519.65	--	0.6075
8	After 8^th Day	550218.34	--	0.5670
9	After 9^th Day	524017.46	--	0.5400
10	After 10^th Day	235807.86	--	0.2430

Table 4. BOD and COD Analysis of Batch 3

Sr. No.	Particulars	Concentrations ((mg/g))
Sr. No.	Particulars	BOD at 20⁰C	COD	BOD: COD
1	After 1^st Day	248962.65	1124829.87	0.2213
2	After 2^nd Day	298755.18	--	0.2656
3	After 3^rd Day	622406.63	--	0.5533
4	After 4^th Day	634854.77	--	0.5644
5	After 5^th Day	647302.90	--	0.5754
6	After 6^th Day	672199.17	--	0.5976
7	After 7^th Day	647302.90	--	0.5754
8	After 8^th Day	622406.63	--	0.5533
9	After 9^th Day	398340.20	--	0.3542
10	After 10^th Day	373443.98	--	0.3320

Table 5. B.O.D./C.O.D. Ratio of Carbohydrate Polymers

Sr. No.	Batch Type	BOD/ COD Ratio	Remarks
1	Batch 1 (white dextrin, sorbitol maleic anhydride)	1.14	Biodegradable
2	Batch 2 (starch, glycerol and maleic anhydride)	0.6075	Biodegradable
3	Batch 3 (starch glycerol, sorbitol, maleic anhydride	0.5976	Biodegradable

The BOD and COD studies explain the biodegradability of the polymers. It was found that the BOD to COD ratio for batch-1 was highest on 8^th day (Table 2) i.e. the highest biodegradation would take place on 8^th day. This is also evident from 8^th day BOD of the sample. The BOD to COD ratio for batch-2 was highest on 7^th day. i.e the highest biodegradation would take place on 7^th day, which is evident BOD of (Table 3). It was also found that the BOD to COD ratio for batch-3 was highest on 6^th day. i.e. the highest biodegradation would take place on 6^th day which is evident from 6^th day BOD of sample (Table 4).

CONCLUSION:

The measure of biodegradability is the ratio of BOD/COD (Table 5). Using thumb rule of the ratio value equal to 0.6 and above then the polymer is considered to be biodegradable. The polymers of present study are found to be biodegradable as these polymers give this ratio within 8 days.

REFERENCES:

1) Milgrom J., Polym Plast Technol. Engg., p.p.18. 167, 1982.

2) Bitritto M.M., Bell J.P., Brenchle G.M., Huang S.J., Knox J.R., J.applied

3) Ferruti. P. Vaecaroui F. and. Makromol Tuzi M.C.chem, pp180, 375. 1979.

4) Wirick. M.G. J. Polym. Sci. Part A. p.p. 1, 6, 1705, 1965.

5) Dara. S.S., “Experiments and calculations in Engineering Chemistry” p.p.45, S.Chand, 2001

6) Dontulwar, J.R., Borikar, D.K, Gogte, B.B., Carbohydrate Polymers, 63(2006) 375-378

7) Dontulwar, J.R., Borikar, D.K, Gogte, B.B., Carbohydrate Polymers, 65(2006) 207-210

Received on 14.07.2011 Modified on 05.12.2011

Asian J. Research Chem. 5(2): February 2012; Page 197-199

INTRODUCTION:

Chemical Oxygen Demand5

Table 1. Hydrophilic- Liphophilic balance

CONCLUSION:

Chemical Oxygen Demand⁵