Charectarization Of Activated Carbon

Published Date: 02 Nov 2017

Abstract

Activated carbon is material having complex porous structures with associated energetic as well chemical inhomogeneities.Their structural heterogeneity is a result of existence of micropores, mesopores and macropores of different sizes and shapes.Activated carbon is one of the most important adsorbents from an industrial view of point. This study involves the prepartion of activated carbon from natural waste.Chemical activation will be carried out using orthophosphoric acid for 20 hours.The prepared activated carbon will be charactarized for its moisture,density,paticle size,surface area,acidic and basic sites,point zero charge.Further the prepared activated carbon will be charectarized by FT-IR and SEM analysis.

Keywords:Activated carbon, natural waste, charectrarization, SEM analysis, FT-IR

Introduction

Activated carbon, also called activated charcoal, activated coal, or carbo activatus, is a form ofcarbon processed to be riddled with small, low-volume pores that increase the surface area available for adsorption or chemical reactions. Activated is sometimes substituted with active.

Due to its high degree of microporosity, just one gram of activated carbon has a surface area in excess of 500 m2, as determined by adsorption isotherms of carbon dioxide gas at room or 0.0 °C temperature. An activation level sufficient for useful application may be attained solely from high surface area; however, further chemical treatment often enhances adsorption properties.

Activated carbons are mainly produced by physical and chemical activation. Physical activation

involves two stages via the carbonization of the precursor (below 700 °C) followed by the partial gasification of the resulting char with oxidizing gases such as air, carbon dioxide or steam, usually at high temperature (700-1100 °C). Chemical activation involves the impregnation of the precursor material with a chemical activating agent followed by activation at temperatures of 400-800 °C under nitrogen atmosphere. Among the activating agents, phosphoric acid, potassium hydroxide and zinc chloride are widely used. Activated carbon is commonly produced from, coal, coconut shells and wood . However, in laboratory scale studies, an enormous range of alternative lignocellulosic materials has been used to produce activated carbons, such as fruit stones, palm shells , sugar cane bagasse, date pits and rice.

the main objective of this study was to prepare activated carbon from tree pods and to compare the properties of the synthesized activated carbon with the commercial activated carbon.

The tree pods of gold medallion tree from the family caesalpiniaceae where used for preparation of the activated carbon.the seeds and the inner jelly like substance were thrown and only the hard outer cover was used to make the carbon.

Materials and methods

.

Preparation of activated carbon

Gold medallion tree pods (cassia leptophylla) was collected from VIT university campus, vellore.

The pods were washed thoroughly with water, followed by double distilled water and then washed again with hot water at 70°C. Dry it in the oven at 105°C for 6 hours and then powdered using a conventional mixer grinder.

10gms of the the fine powdered material was weighed and this was activated by using 1:1 of ortho-phosphoric acid. The activated material was then dried in a hot air oven at 117°C for 4 hours.

This dried material was washed several times with distilled water and then filtered using whatmann’s no.1 filter paper. The filtered material was again oven dried at 107°C for 4 hours.

This crude material was again made into a fine powder using a conventional mixture grinder, and the passed through a 80 mesh sieve to make it into fine powdered material.

2.5g of the crude activated precurssor was weighed and this was kept in a tubular furnace at 750°C (10°C for every one minute) from room temperature to 750°C (carbonization temperature)

The prepared activated carbon was charectarized for volatile matter, moisture content, zero point charge, acidic and basic site, iodine number, adsorption of methylene blue, particle size, FT-IR, XRD, SEM.

Charectarization of Activated Carbon

Moisture content initially for both commercial and synthesized activated carbon about 0.1g of the carbon was taken in a dry weighed beaker and this was kept in the oven at 110°C.the weight of the beaker + activated carbon was taken every one hour. This was to be done until a constant mass was obtained.

Zero point charge to a series of 250 ml conical flask add 50ml of 0.1M KCl and adjust the intial pH of the solutions from 2-10 using 0.1M HCl and 0.1M NaOH. To the solutions add 0.1g of the activated carbon in each flask, and keep it for shacking in a rotospin. The suspension was filtered and the pH of the supernatant liquid is noted.

A graph of ΔpH againt pH is drawn

Volatile matter after obtaining the material from the furnace the activated carbon was weighed again and subtracted from the initial mass to determine the amount of volatile matter.

Boehms titration for acidic sites 20ml each of 0.1M NaOH, 0.1M NaHCO3, 0.1M Na2CO3 were taken in a conical flask and 0.05g of activated carbon was added to it.this was then shacken in an incubator at 150rpm at 28°C. The solutions were filtered and titrated against 0.1M HCl using methyl orange as the indicator.

Similarly for basic sites 20ml of 0.1M HCl was taken in a conical flask and about 0.05g of activated carbon was added to it.this was then shacken in an incubator at 150rpm at 28°C. The solutions were filtered and titrated against 0.1M NaOH using phenolphthalein as the indicator.

Iodine number weigh accurately 0.2g of the powdered carbon sample and introduce it in the iodine flask. Introduce 40ml of 0.1N iodine solution.shake the contents for exactly four minutes.filter through whatmann no.1 fillter paper. Pippette out 10ml of the solution in to conical flask and titrate it against standard sodium thiosulphate solution using starch as the indicator

Adsorption of methylene blue 10ml of the methylene blue solution was pipetted out to it 0.3g of the activated carbon was added to it. This solution was then rotated in a roto spin for 30 minutes and the solutions were filtered and given for uv-visible interpretation

FT-IR a little amount of both the commercial and synthesized sample was kept in a pouch and given for FT-IR analysis

Results and Discussion

Total yield of the synthesized sample=58.4%

The prepared activated carbon was analysed for its different parameters such as moisture,volatile matter,point zero charge,acidic and basic sites, iodine number, methylene number and the results are summarised in table 1

S.No

Parameter

Prepared activated carbon

Commercial activated carbon

1

Moisture (%)

2

Volatile matter (%)

3

PZC

2.1

4.4

4

Acidic sites (m mol g-1)

3.8

2.74

5

Basic sites (m mol g-1)

1.12

1.5

6

Iodine number

7

Methylene number

Table 1 charectarisation of activated carbon prepared from gold medallion tree pods

Commercial activated carbon

FT-IR

Figure 1 FTIR spectrum of commercially available activate

Carbon

Figure 2 FTIR spectrum of prepared activated carbon from

Gold medallion tree pods

FTIR analysis was done for commercial activated carbon and activated carbon prepared for gold medallion tree pods. The IR spectrum of prepared activated carbon matches with that of the commercially available activated carbon.

Conclusion

Activated carbon was prepared from waste materials such as gold medallion tree pods. The yield of the prepared material was found to be 58.4%. FTIR spectra of the prepared activated carbon exactly matches with that of the standard commercially available activated carbon. The results suggest that

gold medallion tree pods can be a good precurssor for preparation of activated carbon with high yield.