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46 Seiten, Note: Publication
To God Almighty for His unfailing love.
To my parents: Pastor(Engr). & Deac.(Mrs.) Ubong Udoakpan
To my siblings: Ifreke Ubong Udoakpan
Precious Aniekeme Inyang
Abasiodiong Ubong Udoakpan
Abigail Ubong Udoakpan
I was not alone in putting this research project together. As always, I had guidance from God, followed by my wonderful parents Engr. & Mrs. Ubong Udoakpan who provided the spiritual, moral and financial backup I needed to succeed in this project. I am grateful to my siblings for their prayers, good humor and love made the writing process smooth, fast and fun too.
I also want to thank my incredible Supervisor, Dr. Abii who guided and supported me in this project. Special thanks to Dr. Okoro, who made the field of analytical chemistry quite interesting for me to tread; and always giving me hope and inspiration throughout my project.
Finally, I am most grateful to my lecturers, laboratory workers, and office staff in Chemistry Department for their unalloyed commitment to the growth and development of this department and her students. I really appreciate the suggestions and contributions of my colleagues (2007 class), friends and loved ones throughout this research project. Thanks to all who have touched my life positively. God bless you all.
Biosorption has been widely used as a more efficient alternative for the current expensive approach to heavy metal remediation from water and waste water. The effectiveness of ripe Musa sapientum (MSR) and ripe Musa cardaba (MCR) peels in the removal of Cd2+, Fe2+, Pb2+, Zn2+ ions was investigated. The amount of metal ions sorbed depended on the metal ion – adsorbent contact time, ion concentration and adsorbent weight. Weight of adsorbent was varied between 0.1 – 0.4g; contact time, 5 – 25 minutes; and ion concentration, 0.01 – 0.04M. The results indicated that Musa sapientum (Ripe) showed higher percentage sorption in removing metal ions from waste water than Musa cardaba (Ripe) peels. The peak percentage sorption of metal ions by MSR peel waste are; Cd2+ (99.95%), Fe2+ (100%), Pb2+ (100%), Zn2+ (99.92%) while metal ions by MCR peel waste was; Cd2+ (99.74%), Fe2+ (99.83%), Pb2+ (100%), Zn2+ (99.60%). The results obtained above showed that both adsorbent species are favourable for sorption and removal of the test heavy metals from their aqueous environment. Nevertheless, ripe Musa sapientum (MSR) is highly recommended for both Fe2+ and Pb2+ uptake due to its sorption capacity and efficiency.
The presence of heavy metal ions in our environment is a major concern due to their toxicity to many life forms. Heavy metal contamination exists in aqueous wastes of many industries, such as metal plating, mining operations, tanneries, smelting, alloy industries and storage batteries industries, etc. (Kadirvelu, K et al: 2001). The extreme discharge of heavy metals into the environment due to industrialization and urbanization has posed a great problem worldwide. Unlike organic pollutants, the majority of which are susceptible to biological degradation, heavy metal ions do not degrade into harmless end products (Gupta, V.K et al: 2001). The conventional treatment processes for heavy metal remediation from wastewater include precipitation, membrane filtration, ion exchange, adsorption, and coprecipitation/ adsorption. Further research on the treatment of industrial effluents containing heavy metal have revealed adsorption to be a highly effective technique for the removal of heavy metal from waste water rather than the expensive conventional approaches (Chand, S et al: 1994).
In this era the need for safe and economical methods for the removal of heavy metals from polluted waters has necessitated research interest towards the production of low cost and efficient alternatives to removing heavy metals from waste water. The low cost agricultural wastes such as sugarcane bagasse (Mohan D., and Singh K.P: 2002), rice husk (Munaf E., and Zein R: 1997), sawdust (Selvi K et al: 2001), coconut husk (Chand, S et al: 1994), neem bark (Ayub, S et al: 2001) etc., for the elimination of heavy metals from wastewater have been investigated by the above researchers. The cost of acquiring these biological wastes is necessary in comparing the different adsorbents due to their individual processing requirements as well as local availability. Therefore, an adsorbent can be termed as a low cost adsorbent if it requires little processing, is abundant in nature, or is a by-product or waste material from another industry (Bailey, S.E et al: 1999). It is imperative to harness different agricultural wastes and their effectiveness in the removal of heavy metals from their aqueous environment.
The scope of the study in this research work is the use of banana peels of two species (agricultural waste) to remove the following heavy metals from synthetic waste water; lead (Pb), cadmium (Cd), iron (Fe), zinc (Zn). The heavy metals under investigation were chosen based on their availability in the laboratory as well as their high levels in our environment. The performance of this experiment was greatly hindered by pH of the solutions and temperature of the environment. Nevertheless, insufficient funds and the time line project submission were also major obstacles.
1. To use agricultural biomass to remove toxic metals from the aqueous environment.
2. To determine the effectiveness of this biomass.
3. To implement this new concept/strategy of waste to wealth, thereby ensuring environmental sustainability.
4. To compare the effectiveness of the different species of banana peels (Musa sapientum and Musa cardaba).
5. To recommend the best peel waste in absorption study.
This work will serve as a guide to scientists, researchers and students on the new and novel method of removing heavy metals from waste water. The absorption effectiveness of heavy metals using banana peel waste of two species will also be compared with other absorbents previously studied.
This study will also help to keep the environment clean and green while turning agricultural waste into wealth. This can help reduce unemployment if the youths can gather these wastes, sort them into various types and sell them to companies for the treatment of industrial effluents instead of other expensive chemical methods.
In this chapter, review of heavy metals and their effects is carried out. The primary metals under research will be carefully examined i.e. Zn(zinc),Pb(lead),Cd(cadmium) and Fe(iron). Also, various biological wastes used as adsorbents in heavy metal remediation will be discussed.
A heavy metal is a member of a loosely defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloid, lanthanides and actinides. Many different definitions have been proposed-some based on density, some on atomic number or atomic weight and some on chemical properties or toxicity.(J.H Duffus:2002). Heavy metals occur naturally in the ecosystem and vary in concentration. In recent times, anthropogenic sources of heavy metal i.e. pollution have been introduced into the ecosystem by the activities of man.
Heavy metal pollution is one of the various problems facing mankind. Heavy metals are dangerous both to the environment and human health e.g. mercury, cadmium, lead, chromium, (C. Michael Hogan: 2010), some may cause corrosion (e.g.zinc, lead), some are harmful in other ways e.g. Arsenic may pollute catalysts.
Heavy metal pollution can spring up from many sources but most arises from the purification of metals e.g the smelting of copper and the preparation of nuclear fuels. Electroplating is the primary source of chromium and cadmium. Through precipitation of compounds or by an exchange into soils and mud, heavy metal pollutants can localize and lay dormant. Heavy metals do not decay in water or soil unlike organic pollutants that is why it is very difficult to remediate it. When these heavy metals are percolated into the soil due to improper disposal or run-off into the sea, rivers or streams, it poses a strong health risk for man and animals. Due to its potential for bioaccumulation and biomagnifications, it causes heavier exposure for some organisms that is present in the environment alone.
Heavy metals are beneficial to healthy life. In minute quantities, certain heavy metals are nutritionally essential. These are commonly referred to as trace elements e.g. iron, copper, manganese, zinc. These elements or some of them are food, naturally in food items, in fruits and in vegetables and in commercially available multivitamin products (Stellman J. M: 1998).
The first four heavy metals below and their chemistry are the ones investigated in this research project. Others are also toxic and dangerous to health.
The atomic number of lead is 82. It is soft, malleable poor metal; lead is a group 4A element in period 6. It has a bluish white color when freshly cut, but varnishes to a dull grayish color when exposed to air. Lead has poor electrical conductivity) (Brady J.E and Hoslum J. R: 1996). Lead has been commonly used for thousands of years and even dates back to 6400 BC (Heskel D.K: 1983).
SOURCES OF LEAD
Metallic lead occurs in nature although it is very rare. It is usually found in ore with zinc, silver and copper and is extracted together with these metals. The main lead mineral is galena (PbS), which contains 86.6% lead. Other common varieties are cenissite (PbCO3) and anglesite (PbSO4) (Brady J.E and Hoslum J. R: 1996)
USES OF LEAD
1. Lead is used frequently in polyvinyl chloride (PVC) plastic, which coats electrical cords, also as projectiles for fire arms and fishing sinkers because of its density. It is also used as a shield from radiation in x-ray rooms.
2. Lead is a major constituent of the lead-acid battery used as a car battery. It is used as a coloring element in ceramic glazes, notably in the colors, red and yellow (Stellman J. M : 1998).
3. Lead is highly resistant to corrosion and because of this property; it is used to contain corrosive liquids like sulphuric acid.
4. Lead is very malleable and can be used widely in building construction e.g external coverings of roofing joints.
TOXICITY OF LEAD
Lead poisoning typically results from ingestion of food and water contaminated with lead; but may occur after accidental ingestion of contaminated soil, dust or lead based paint. Lead can damage nervous connections (especially in young children) and cause blood and brain disorders (Needleman H. L et al : 1990).
Meanwhile, lead is a soil contaminant; its presence in natural deposits enters the soil through gasoline (leaded) leaks from underground storage tanks or through a waste stream of lead paint or lead grindings from certain industrial processes or lead pipes.
Iron is a metallic element with atomic number 26 and standard atomic weight of 55.845gmol-1. Iron is a group 8B and period 4 elements and hence classified as a transition metal (Brady J.E and Hoslum J. R: 1996). Iron and iron alloys (steels) are by far the most common ferromagnetic materials in everyday use.
Iron is the 6th most abundant element in the universe, formed as final act of nucleo-synthesis, by silicon fusing in massive stars (Brady J.E and Hoslum J. R: 1996). It makes up about 5% of the earth’s crust; the earth’s core is believed to consist largely of an iron-nickel alloy comprising 35% of the mass of the earth as a whole. Iron forms compounds mainly in the +2 and +3 oxidation states.
SOURCES OF IRON
Pure iron is a metal but it is rarely found in this form on the surface of the earth because it oxidizes readily in the presence of oxygen and moisture. In order to obtain metallic iron, oxygen must be removed from naturally occurring ores by chemical reduction mainly of the iron ore hematite (Fe2O3) by carbon at high temperature (Brady J.E and Hoslum J. R: 1996).
Iron can also be found as dietary supplements in foods like red meat, fish, poultry, lentils, leaf vegetables, fortified bread and breakfast cereals. Iron in meat is more easily absorbed than iron in vegetables. Iron provided by dietary supplements is often found as iron (ii) fumarate, although iron sulphate is cheaper and is absorbed equally well.
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