Adsorption of Selected Heavy Metals on Activated Carbon Prepared From Plantain (Musa Paradisiacal.) Peel

Adsorption of Selected Heavy Metals on Activated Carbon Prepared From Plantain (Musa Paradisiacal.) Peel

Chapter One

Aim and Objectives

This research aimed to prepare activated carbon from plantain peel by using various activating agents and applications for the adsorption of some selected heavy metals. The above aim would be achieved by the following objectives

Determination of the elemental composition of plantain
Preparation of activated carbon from plantain peel by chemical activation method using ZnCl_2,H₃PO₄ and NaOH as activating
Evaluation some physicochemical properties of the
Studying the effects of contact time, adsorbent dosage, agitation time, agitation speed, pH and initial concentration on the adsorption efficiency in order to ascertain the optimum conditions as well as nature of the adsorption process of the selected heavy metals (Cu²⁺, Cr⁶⁺and Cd²⁺) on the activated plantain
Investigation of the adsorption efficiency of activated carbon prepared from plantain peel with variable particle sizes on adsorption of selected heavy
Examination of the adsorption efficiency using adsorption isotherm
Determination of adsorption efficiency using R_L

CHAPTER TWO

Literature Review

Several studies have shown that it is imperative to monitor, control and clean up environmental pollution caused by some heavy metals (Austin, 1987; Diets, 1990; Ekanem, 1996). Heavy metal ions are reported as prioritized pollutants, due to their mobility in natural water ecosystems and due to their toxicity (Volesky and Holan, 1995; Min et al., 2004).

The enormous available environmental pollution in the present age is due to urbanization and industrialization, which have added significant amount of heavy metals into natural aquatic and terrestrial ecosystem. These heavy metals are not biodegradable and their presence in streams and lakes lead to bioaccumulation in living organisms causing health problems in plants, animals and human beings (Shetty and Rajkumar, 2009). Several methods such as ion exchange, solvent extraction, reverse osmosis, precipitation and adsorption have been proposed for the treatment of waste water polluted with heavy metals (Gupta and Babu, 2004). Hence, adsorption process by using activated carbon is being widely used to remove heavy metals pollutants from waste waters. (Okuo and Ozioka, 2001)

Among the several chemical and physical methods, adsorption onto activated carbon has been found to be superior to other techniques in water-re-use methodology, because of its capability for adsorbing a wide range of different types of adsorbates (pollutants) efficiently and its simplicity of design (Ahmad et al., 2006).

Other Uses of Activated Carbon in Metals Adsorption

Medicinal applications

First and foremost use of activated carbon is seen in treatment of poisonings and overdoses following oral ingestion. To be specific, overdoses and poisoning following oral ingestion are cured using activated carbon (Yehaskel, 1978). It has become the treatment of choice for many poisonings, and other decontamination. In addition to this, activated carbon is used to reduce blood alcohol content; it is ingested before consumption of ethanol. It is also apparently helpful in detoxification of the body and is a common constituent of colon cleanse products.

Industry and Environment Applications

Carbon adsorption has numerous applications in removing pollutants from air or water streams, both in the field and in industrial processes such as: Spill cleanup, Groundwater remediation, Drinking water filtration, Wastewater treatment, Air purification, Volatile organic compounds capture from painting, dry cleaning, gasoline dispensing operations, and other processes (Yenkie and Natarajan, 1993; Raoet al., 1993).

Gas Purification

In chemical industry, activated carbon has an important role to play. For instance, activated carbon air filters are used for purification of compressed air and gas (Houghton and Wildman 1971). This helps removal of oil vapors, hydrocarbons and odor from it. These filters are also used to retain radioactive gases from a nuclear boiling water reactor turbine condenser. When it comes to purification, activated carbon is helpful for purifying sodium acetate, a non-dangerous homemade chemical (Ekanem, 1996).

Storage o f Fuel

The fuel storage is another area where researchers see a lot of potential in activated carbon on account of its adsorption qualities. In fact, the prospect of storing gas in activated carbon seems very feasible and practical as the gas can be stored in low mass, lower pressure and low volume environment (Yang and Chen 2008; Faller, 2009).

Agriculture

As far as agriculture is concerned; the uses of activated carbon are significant. Fundamentally it is used to detoxify the soil or water when growing plants. Another good part about this form of carbon is that it helps plants get rid of pesticides, fertilizers or herbicides applied to the soil (Ahmednaet al., 2000).

CHAPTER THREE

Materials and Methods

Sample Collection, Identification and Treatment

Samples of plantain peel were collected from SabonGari Central Market in Zaria, Kaduna State. Plantain peels were washed thoroughly with tap water and then with distilled water to remove all trace of impurities, oil, dirt, dust and salts. The samples were sundried and then dried in an oven at 100^oC for 24 hours. The dried PP were cut and pulverized into smaller particle sizes with a mortar and pestle; then sieved into different particle sizes such as 75 µm, 150 µm, 355 µm, 425 µm and 835µm. The plantain peel family is known as musaceaeand was identified as Musa paradisiacaL. in Department of Biological Sciences Ahmadu Bello University, Zaria.

Reagents

The chemicals used were of analytical grade except where stated otherwise.

Carbonization Process

Carbonization process is achieved by weighing 2.00 g fresh batch of sample in clean silica crucibles and heating in an air – tight oven at 500^oC for 5hours. (Gimba and Bahago, 2004; Omeizaet al., 2011). The equation for the process is shown below:

CHAPTER FOUR

Results

Physicochemical Properties

The results of determinations on plantain peel are presented in Table 4.1.

CHAPTER FIVE

Discussion

Dry Matter and Moisture Content of the Plantain Peel

The laboratory results of the moisture content and dry matter content were determined to be 6.7% and 93.3% respectively as shown in Table 4.1. The moisture content of a sample refers to the percentage of water content of the sample. These gave a tangible and substantial amount of organic matter needed for conversion to carbon by carbonization process. Hence, the results obtained for PP samples were good since the yield and quantity of the activated carbon produced can be enhanced by removal of moisture (Shakirullahet al., 2006). The percent moisture was higher than 4.18% for walnut shell reported by Abechi (2006) while lower than 7.21% reported by Erhanet al., (2004) for almond shell. According to Abram (1973), the moisture content should be taken into account when evaluating the relative capacities of different carbon materials for the adsorption of a wide range of adsorbates (Roles et al., 1997).

Ash Content of the plantain peels Sample.

The percentage of ash content for PP sample was found to be 2.01% as shown in Table 4.1. The ash content of a sample is the inorganic residue left after the organic matter has been burnt off; also the ash content depends on the types of plant and carbon source (FAO, 2005; Akyeampong, 1999). The obtained value for plantain peel was favorable because the ash content serves as interference during the adsorption (Khan et al., 2009). The ash content of plant origins have reported value ranging from < 2- 25% for rice husks. The lower the ash content the better the starting material (Lin and Wu 2001). The result obtained for plantain peel was consistent with Abechi (2006) reported 1.47% for walnut shell; Romero Gonzalez et al., (2001) reported ash content of 2.0%, 2.21% and 2.14% for cornelian cherry, apricot stone and almond shells respectively.

CHAPTER SIX

Summary, Conclusion and Recommendation

Summary

This research showed that activated carbon prepared from plantain peel is an effective and efficient adsorbent for sorption of Cr⁶⁺, Cu²⁺ and Cd²⁺. Physicochemical properties indicated high quality adsorbent and FTIR analysis for plantain peel suggest strongly that there were functional groups capable of adsorbing the selected metals. The removal of the selected heavy metal ions by different particle size of activated carbon showed the removal rate increased as particle size decreased, whereas the strength of adsorptivity increased based on variation of activating agent as follows: carbonized carbon < salt activated carbon < base activated carbon < acid activated carbon. It was also observed, the adsorbent dosage, agitation speed, agitation times, pH and initial concentration of metal ion are factors that have great influence on adsorption effectiveness and efficient. Also, the adsorption isotherms (Langmuir and Freundlich) provided important information about the adsorption of the Cr⁶⁺, Cu²⁺ and Cd²⁺ . R_L separation factor give information that the shape of Langmuir which is favorability while the maximum adsorption (q_max) the coefficient of correlation gave us clue on linearity.

Conclusion

From the experimental observation, results and discussion of this research work, it can be inferred that the plantain peel sample used as activated carbon have these:

It is a cheap, good alternative source for activated carbon production and the 1 (one) step activation method of preparation with suitable activating agent and agitation time can be
It can be used as an adsorbent for the adsorption of the Cu²⁺, Cd²⁺andCr⁶⁺
The adsorption process is highly dependent on particle size, activating agents, agitation time adsorbent dosage, agitation speed, pH and initial
The adsorption capacity of activated carbon prepared from plantain peel with both acid and base activators have comparable strength adsorption rate which higher than commercialactivated carbon.
It was observed that the trend of metal affinity for activated PP surface was Cr⁶⁺> Cd²⁺>Cu²⁺.
The adsorption of these metals by activated PP is a monolayer sorption process.
FTIR spectra analysis confirmed the presence of absorbance peaks of carboxyl, alkene, alkanol, amide, aldehyde and alkyl functional groups. Thus, these functional groups are responsible for the adsorption of the selected metals.

Recommendation for Further Studies

Study the adsorption process using other metals like zinc, lead, arsenic amongothers
Use of other activation methods like two –step impregnation and microwave method since the activation determine the efficiency of the adsorption
Use of other activating agents like H₂SO₄, KOH, HCl among
Examine the gas-solid phase
Ability of this adsorbent to be employed in the treatment of water dispensed for public consumption should be
Research should be carried out on the potential of the adsorbent to adsorb other pollutants such as oil spillage, dyes and other poisonous chemical effluent discharge from textile and food industries.

REFERENCES

Abdel-ghani, N. T, Hefney, M.and El-Chaghaby, G.A.F. (2007) . Removal of lead from aqueous solution using low cost abundantly available adsorbents. Int. J Environ. Sci Tech. 4 (1):67– 73.
Abechi, S.E. (2006). Adsorption characteristics of Ti(IV) and Zn(II) oxide coated activated carbon from walnut shells. An M.Sc. Thesis, Department of Chemistry, Ahmadu Bello University, Zaria.
Abram, J. C. (1973).The characteristics of activated carbon. In: Proceeding of Conferences Activated Carbon in Water Treatment University of Reading, UK. Pp 1-29.
Ahalya, N., Kanamadi, R.D., and Ramachandra, T.V. (2005). Biosorption of chromium (vi) from aqueous solution by the husk of Bengal gram (cicerarientinum). Electronic journal Biotechnology 8(3): 258 -264.
Ahalya, N., Ramachandra, T.V. and Kanamadi, R.D. (2003).Biosorption of heavy metals.Research Journal of Chemistry and Environment, 7(4):83-93.
Ahmed, A.A., Hammed, B.H. and Aziz, N. (2006). Adsorption of direct dye on palm ash: Kinetic and equilibrium modeling. Journal of Hazardous materials, 1-10.

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