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Table of Contents COVER PAGE ..................................................................................................................i

CERTIFICATION ………………………………………………………………………ii

CHAPTER ONE ................................................................................................................ 2

INTRODUCTION ............................................................................................................. 3

BACKGROUND OF STUDY ....................................................................................... 3

PROBLEM STATEMENT ........................................................................................... 5

OBJECTIVE OF STUDY ............................................................................................. 5

IMPORTANCE OF THE STUDY ............................................................................... 6

CHAPTER TWO ............................................................................................................... 7

LITERATURE REVIEW ................................................................................................. 7

PRODUCED WATER .................................................................................................. 7

DISCUSSION ON SOME HEAVY METALS ........................................................... 8

Lead (Pb) .................................................................................................................... 8

Copper (Cu).............................................................................................................. 10

Mercury (Hg) ........................................................................................................... 11

Cadmium (Cd) ......................................................................................................... 12

Arsenic (As) .............................................................................................................. 13

METHODS ON REMOVAL OF HEAVY METALS .............................................. 15

Chemical precipitation ............................................................................................ 15

Solvent extraction .................................................................................................... 16

Reverse osmosis........................................................................................................ 16

Evaporation .............................................................................................................. 17

Electrodialysis .......................................................................................................... 17

Ion exchange ............................................................................................................. 17

Adsorption ................................................................................................................ 18

Bioadsorption ........................................................................................................... 19

Lagenaria siceraria ...................................................................................................... 19

Description ............................................................................................................... 19

Distribution .............................................................................................................. 20

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Adsorption models ....................................................................................................... 21

CHAPTER THREE ......................................................................................................... 25

MATERIAL AND METHODS ...................................................................................... 25

MATERIALS ............................................................................................................... 25

METHODS ................................................................................................................... 25

EQUIPMENTS ............................................................................................................ 25

EXPERIMENTS TO BE CONDUCTED .................................................................. 25

WORK PROGRAMME ............................................................................................. 26

REFERENCES ................................................................................................................ 27

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CHAPTER ONE

INTRODUCTION

BACKGROUND OF STUDY

Environmental impact of industrial activities and reprisal activities of stakeholders

and public institutions has giving rise to a state of crises or near crisis in several regions

where projections are not made to monitor, prevent or reduce effect of industrial effluents

on the host environment and communities. Environmental impact assessment and

sustainable development are now keywords in all industrial project aim at creating a

balance between risks, socioeconomic and environmental considerations in the design,

construction, installation and operation of technological facilities.

The Niger Delta region of Nigeria is a region of high petroleum production activity.

The region is currently laden with incessant interference on economic activity due to issues

of sustainable development with stakeholders. One of the visible impacts pointed at is the

effect of the effluent discharge from oil production platforms into rivers and estuaries

(Gberesu, 1989). These affect host communities of these production activities when eat

fish from the rivers or drink contaminated water. International Occupational Safety and

Health Information Centre in her journal (1999) stated that heavy metal toxicity can result

in damaged or reduced mental and central nervous function, lower energy levels, and

damage to blood composition, lungs, kidneys, liver, and other vital organs. Formation

water is natural occurring water which in some cases and found in association with oil and

gas bearing rocks in oil formations or reservoir (Kobranova 1989).

Natural gas and formation water are the major byproducts of the crude oil

production industry. Crude oil, a mixture of oil, gas and water flows from the reservoir

through pipelines to the platform where the mixture is separated. The natural gas is flared

until the resent government program to stop flaring. The water from the separation process

which is known as process water is usually discharge after biological treatment in an

oxidation pond.

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The Federal Ministry of Environment, Nigeria Conservation Foundation noted that

the damage from oil and gas operations is chronic and cumulative, and has acted

synergistically with other sources of environmental stress to result in a severely impaired

coastal ecosystem and compromised livelihoods and health of the regions impoverished

residents. The 70,000 square kilometers Niger Delta contains 7,400 of West Africa’s

20,000 square kilometers of mangroves, and is considered one of the 10 most important

wetlands and marine ecosystems in the world. Millions of people depend upon the delta’s

natural resources for survival, including the poor in many other West African countries

who rely on the migratory fish from the delta. The region contains many threatened species

found nowhere else in the world, including several primates, ungulates and birds.

Information on the volume and characteristics of the effluent discharge is difficult

to assess due to the nontransparent nature of the multi nationals working in the oil

industries.

Several studies including that by Muhammad et al, (2005) and Lenntech (2006)

revealed that drive for proactive attention on effective treatment of waste before discharge

from petroleum has been on the increase to encourage the reduction of its impact on the

economy of such operation and on the environment.

Since heavy metal ions are not biodegradable in nature, effective removal of heavy

metal ions from aqueous solutions through other technologies (physical or chemical) is

important in the protection of environmental quality and public health. Various chemical

and physical methods have been used to remove heavy metal ions in the last few decades.

These methods include chemical precipitation, solvent extraction, ion exchange,

evaporation, reverse osmosis, electrolysis and adsorption. Among these methods, chemical

precipitation, solvent extraction, ion exchange and adsorption are more commonly used.

Chemical precipitation has traditionally been used to remove heavy metal ions from

wastewater with relatively high concentrations. The operation of chemical precipitation is

simple but generates large quantity of sludge that is often difficult for further disposal. In

addition, chemical precipitation is usually not effective to remove trace levels of metal ions

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from aqueous solutions. Solvent extraction has widely been used in organometal removal.

Although the process may have fast kinetics and high capacity, solvent extraction is often

costly due to the quantity and specific type of solvents needed. Ion exchange method has

commonly been used to remove metal ions from water or wastewater, but the process has

slow kinetics, consumes additional chemicals, generates hazardous streams, and is not well

applied to heavy metal ions due to possible problem of resin pollution. Adsorption has been

considered as, possibly, the most cost-effective method for heavy metal ion removal,

especially at medium to low concentrations, because the process is simple, and chemical

consumption or waste generation is not a significant issue. However, traditional adsorbents,

such as activated carbon, are often not effective to adsorb heavy metal ions from water or

wastewater.

The most important parameter for determining the efficiency and cost of adsorbents

is the adsorption capacity. Adsorption isotherm is a graphical; representation of the

relationship between the amounts of adsorbate adsorb per unit mass of adsorbent and the

equilibrium concentration of the solution at constant temperature (Kenedy et al, 1993).

PROBLEM STATEMENT

Most waters have been contaminated by toxic metals through the discharge of

industrial effluent. The contamination of these waters with industrial effluent is becoming

a serious environmental problem in Nigeria. Reports abound that these waters contain

heavy metal ions. The presence of these heavy metal ions in these waters has been

responsible for several health problems with plants, animals and human beings. Industries

in Nigeria pay huge amount of money as surcharges to public treatment plant.

OBJECTIVE OF STUDY

This study deals with the possibility of using lagenaria siceria biomass as an

adsorbent for removal of toxic ions, such as Pb2+, Cd2+, Zn2+,etc from produced water. To

achieve these, a study will carried out with the following specific objectives:

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1. To prepare adsorbent from lagenaria siceria shell and seeds both as

carbonized and dried.

2. To evaluate the application of locally produced activated carbon in produced

water treatment by the removal of heavy metals.

3. To investigate the influence of batch sorption parameters, such as adsorbent

dosage, particle size, pH, initial metal ion concentration, temperature and

contact time.

4. To study the adsorption isotherms using model equations, such as Langmuir

and Freundlich isotherm models.

IMPORTANCE OF THE STUDY

The amount and variety of chemicals discharged into wastewaters has been

increasing considerably. This increase is as a result of rapid development of chemical,

petroleum processing and allied industries in Nigeria. Wastewaters from these industries

are discharged into ground and surface water, making it unfit for human and animal

consumption due to the presence of some chemical and biological pollutants. These

pollutants can cause severe ailments in human and animals, are carcinogenic, toxic and

mutagenic. The increase in the variety and amount of hazardous chemical in bodies of

water has made conventional methods of wastewater treatment ineffective and inefficient

as a result, a new method of treatment through the use of activated carbon has becomes

imperative.

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CHAPTER TWO

LITERATURE REVIEW

PRODUCED WATER

Produced water is an inextricable part of the hydrocarbon recovery processes, yet it

is by far the largest volume waste stream associated with hydrocarbon recovery. Water

production estimates are in the order of 250 million B/D in 2007, for a water-to-oil ratio

around 3:1, and are expected to increase to more than 300 million B/D between 2010 and

2012 (Dal Ferro and Smith 2007). Increasingly stringent environmental regulations require

extensive treatment of produced water from oil and gas productions before discharge;

hence the treatment and disposal of such volumes costs the industry annually more than

USD 40 billion. Consequently, for oil and gas production wells located in water-scarce

regions, limited freshwater resources in conjunction with the high treatment cost for

produced water discharge makes beneficial reuse of produced water an attractive

opportunity.

Water consumption worldwide is roughly split, with 70% agricultural use, 22%

industrial use, and 8% domestic use (UNESCO 2003). A fifth of the population lives in

areas of water scarcity, and one in eight lacks access to clean water. Currently, properly

treated produced water can be recycled and used for waterflooding [produced water re-

injection (PWRI)] and other applications, such as crop irrigation, wildlife and livestock

consumption, aquaculture and hydroponic vegetable culture, industrial processes, dust

control, vehicle and equipment washing, power generation, and fire control (Veil et al.

2004). These beneficial reuses directly decrease the withdrawal of potable water, a highly

valuable commodity in many regions of the world. Although produced water can

potentially be treated to drinking water quality (Tao et al. 1993; Doran et al. 1997; Kharaka

et al. 1998; Funston et al. 2002; Xu et al. 2008), little research has been done on the

feasibility and cost-effectiveness of direct or indirect potable reuse of produced water from

oil and gas production.

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Produced water is the aqueous liquid phase that is co-produced from a producing well along

with the oil and/or gas phases during normal production operations. This includes water

naturally occurring alongside hydrocarbon deposits, as well as water injected into the

ground. The following are the main contaminants of concern in produced water:

High level of total dissolved solids (TDS)

Oil and grease

Suspended solids

Dispersed oil

Dissolved and volatile organic compounds

Heavy metals

Radionuclides

Dissolved gases and bacteria.

Chemicals (additives) used in production such as biocides, scale and corrosion

inhibitors, and emulsion and reverse-emulsion breakers

The amount of produced water, and the contaminants and their concentrations present

in produced water usually vary significantly over the lifetime of a field. Early on, the water

generation rate can be a very small fraction of the oil production rate, but it can increase

with time to tens of times the rate of oil produced. In terms of composition, the changes

are complex and site-specific because they are a function of the geological formation, the

oil and water (both in-situ and injected) chemistry, rock/fluid interactions, the type of

production, and required additives for oil-production-related activities.

DISCUSSION ON SOME HEAVY METALS

Lead (Pb)

Lead is one of the IV-A group elements (atomic number of 82) whose electron

configuration consists of filled shells plus four electrons in the 6s26p2 states. Lead has two

stable positive oxidation states: +2 and +4, and it is generally found in complexes with a

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coordination number of 6. The most common one and the one with the most complex

hydrolysis behavior is Pb2+ (Harrison and Laxen, 1981). Because of its low melting point

and durability, lead has been an important metal in human societies over many thousands

of years. During the period of Roman Empire, lead pipes were widely used in water supply.

Lead was also used early as a construction material. Since the early days of the industrial

revolution, the use of lead has increased dramatically (Harrison and Laxen, 1981).

Nowadays, lead is normally used as a radiation shield around X-ray equipment and nuclear

reactor and is extensively used in paints and, in lead arsenate, as insecticides in agriculture

(Schneegurt et al., 2001). The major reason for lead pollution in environment is due to

anthropogenic factor of industrial applications, such as in electroplating industries, metal

finishing industries, burning of leaded gasoline, mining and metallurgic industries, and

trash incineration. According to a report, the anthropogenic inputs of lead (direct deposition

from air and runoffs) to the environment were one or two orders of magnitudes greater than

that from natural sources (Hutchinson and Meema, 1987). For example, the storage battery

industry has been the largest user of lead. Lead from burning leaded gasoline used to be a

major source of atmospheric and terrestrial lead, much of which eventually entered natural

water systems.

Lead is a cumulative poison and concentrates primarily in the bones. The effects on

human include hypertension and brain damage. Acute lead poisoning in humans causes

severe dysfunction in the kidneys, reproductive system, liver, brain and central nervous

system. Lead poisoning from environmental exposure is known to cause mental

retardation, especially in children. Mild lead poisoning causes anemia. The victim may

have headaches and sore muscles and may feel generally fatigued and irritable (Harrison

and Laxen, 1981). Hence, lead has been classified as priority pollutant by the US

Environmental Protection Agency (EPA) and the Maximum Contaminant Level (MCL) of

lead ions in drinking water has been set at a very low level of 0.015 mg/L by the EPA.

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Copper (Cu)

Copper, the 29th element in the Periodic Table, has the electronic configuration of

1s22s22p63s23p63d104s1. It is the least reactive element in the first row of the transition

metals and it forms some compounds in which there is an incomplete d-subshell. Being a

transition metal, copper occurs in metallic form or in compounds as Cu (I) or Cu (II)

(Merian, 1991). Copper is a reddish metal that occurs naturally in rock, soil, water,

sediment, and air. The primary use of copper, accounting for approximately half of its

production is in electrical equipment. Copper is also a component of many alloys where it

may occur together with other metals, such as silver, cadmium, tin and zinc. Other

important uses of copper are in plating, plumbing and heating. Copper salts may also serve

as pesticides (Friberg et al., 1986). Copper pollution is mainly caused by anthropogenic

factor of industrial applications. Corrosion of plumbing, metal cleaning operations, plating

baths and rinses are by far the greatest cause of concern. For example, copper levels in

plating baths can be as high as 50,000 mg/L, while its concentration in the rinse waters

may be as high as 0.02 to 1% of the process bath concentration (Golomb, 1972). Copper is

rarely found in source water directly, but copper mining and smelting operations and

municipal incineration of wastes may be the major sources of copper contamination to

source water. For example, the concentrations of copper in the sewage to Winnipeg’s three

wastewater treatment facilities were reported to be 157, 271, 201 µg/L, respectively. The

presence of copper in the sewage was attributed mainly to the industrial effluents received

in one of the facilities and was due to the use of copper piping in the districts served by the

other two plants (Carroll and Lee, 1977). It was estimated that the annual industrial

discharges of copper into freshwater environments was at 1.4 x 1010 g/year, and the

amounts of copper in industrial wastes and sewage sludge that have been dumped into the

ocean was 1.7 x 1010 g/year worldwide (Nriagu, 1979).

Copper is an essential element for living organisms, including humans, and

necessary in small amounts in our diet to ensure good health. However, too much copper

can cause adverse health effects, including vomiting, diarrhea, stomach cramps, and nausea

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(Ng et al., 2002). Copper is stored mainly in liver, brain, heart, kidney and muscles. There

are evidences to suggest that copper may be carcinogenic and large acute doses and intake

could accumulate in the liver or kidney and be extremely harmful, even fatal (Tseng et al.,

1999). Marine and aquatic organisms can also be at great risk because copper is highly

toxic to them, even at low concentrations. Although it is an essential element to plants,

exceptionally high copper concentrations may be toxic to plants by affecting mainly the

growth of the roots (Massey et al., 1973).

Mercury (Hg)

Mercury has an atomic number of 80 and exists in ionic form as Hg2+ (mercuric

salts) and Hg+ (mercurous salts). Organic mercury compounds consist of diverse chemical

structures in which mercury forms a covalent bond with carbon. Occurring as elemental

mercury, and as inorganic and organic compounds, all forms of mercury have different

toxicological properties (O’Neill, 1985). Elemental and inorganic mercury compounds are

used in the manufacture of scientific instruments (thermometers, barometers), electrical

equipment (switches, rectifiers, oscillators, electrodes, batteries, coulometers, mercury

vapor lamps, X-ray tubes, lead and tin solders), dental amalgams, synthetic silk. Mercury

has also been used in the plating, tanning and dyeing, textile, photographic and

pharmaceutical industries (Watras and Huckabee, 1994). Human activities have resulted in

the release of a wide variety of inorganic and organic forms of mercury. Elemental mercury

was released into the atmosphere through the electrical industry, chloralkali industry, and

the burning of fossil fuels (coal, petroleum, etc.). Metallic mercury has also been released

directly into fresh water by chloralkali plants, and both phenylmercury and methylmercury

compounds have been released into fresh and sea water by wood paper-pulp industry and

chemical manufacturers. One of the major sources of mercury waste comes from the use

of mercury cells in the chloralkali industry. Water contains mercury mainly in the form of

Hg2+. The acute and long-term action of Hg2+ can be gastrointestinal disturbance and renal

damage − appearing as a tubular dysfunction with tubular necrosis in severe cases (Liu et

al., 2003).

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Methylmercury is formed naturally in the aquatic and terrestrial environment from

elemental mercury and mercuric mercury. The methylmercury is rapidly taken up by living

organisms in aquatic environment and enters the food chain. The hazards involved in long-

term intake of food containing methylmercury are from the efficient absorption (90%) of

methylmercury in man and methylmercury accumulation in the brain. Chronic poisoning

can cause degeneration and atrophy of the sensory cerebral cortex, as well as parenthesis,

ataxia, hearing and visual impairment. Methylmercury exposure to pregnant females may

result in inhibited brain development of the fetus with psychomotor retardation of the child

as a consequence (Watras and Huckabee, 1994). Hence, one of the ways to reduce the effect

of methylmercury can be to minimize the presence of Hg2+.

Cadmium (Cd)

Cadmium (Cd) is a soft, malleable, bluish white metal found in zinc ores, and to a

much lesser extent, in the cadmium mineral greenockite. In 2011, US production of

cadmium was estimated at 600 metric tons, down approximately 40% from the production

levels 20 years ago (1992). Most of the cadmium produced today is obtained from zinc

byproducts and recovered from spent nickel-cadmium batteries. First discovered in

Germany in 1817, cadmium found early use as a pigment because of its ability to produce

brilliant yellow, orange, and red colors. Cadmium became an important metal in the

production of nickel-cadmium (Ni-Cd) rechargeable batteries and as a sacrificial corrosion-

protection coating for iron and steel. Common industrial uses for cadmium today are in

batteries, alloys, coatings (electroplating), solar cells, plastic stabilizers, and pigments.

Cadmium is also used in nuclear reactors where it acts as a neutron absorber. While lithium

ion batteries have made significant gains in popularity for lightweight electronic devices,

new market opportunities for industrial applications of Ni-Cd batteries will continue to fuel

cadmium use. Increased investment in solar power will also drive cadmium use in the

future. China, South Korea, and Japan are the leading producers of cadmium in the world,

followed by North America.

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Cadmium and its compounds are highly toxic and exposure to this metal is known

to cause cancer and targets the body's cardiovascular, renal, gastrointestinal, neurological,

reproductive, and respiratory systems.

Workers may be exposed during smelting and refining of metals, and manufacturing

batteries, plastics, coatings, and solar panels. The expanding Ni-Cd battery recycling

industry is a concern for cadmium exposure. Electroplating, metal machining, welding and

painting are operations associated with cadmium exposure. Workers involved in landfill

operations, the recycling of electronic parts, or the recycling of plastics may be exposed to

cadmium. Compost workers and waste collectors are also potentially exposed to dust which

may contain cadmium. The incineration of municipal waste is another source of cadmium

exposure.

Cadmium is an important metal for many types of businesses and industrial

processes. Cadmium is most often used in the manufacturing sector but worker exposure

can also occur in other industry sectors including construction, wholesale trade, and

transportation.

Arsenic (As)

Arsenic is a widely distributed metalloid, occurring in rock, soil, water and air.

Inorganic arsenic is present in groundwater used for drinking in several countries all over

the world (e.g. Bangladesh, Chile and China), whereas organic arsenic compounds (such

as arsenobetaine) are primarily found in fish, which thus may give rise to human exposure

(WHO, 2001). Smelting of non-ferrous metals and the production of energy from fossil

fuel are the two major industrial processes that lead to arsenic contamination of air, water

and soil, smelting activities being the largest single anthropogenic source of atmospheric

pollution (Chilvers et al., 1987).

Concentrations in air in rural areas range from <1 to 4 ng/m3, whereas

concentrations in cities may be as high as 200 ng/m3. Much higher concentrations (>1000

ng/m3) have been measured near industrial sources. Water concentrations are usually <10

µg/l, although higher concentrations may occur near anthropogenic sources. Levels in soils

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usually range from 1 to 40 mg/kg, but pesticide application and waste disposal can result

in much higher concentrations (WHO, 2001). General population exposure to arsenic is

mainly through intake of food and drinking water. Food is the most important source, but

in some areas, arsenic in drinking water is a significant source of exposure to inorganic

arsenic. Contaminated soils such as mine-tailings are also a potential source of arsenic

exposure (WHO, 2001).

Absorption of arsenic in inhaled airborne particles is highly dependent on the

solubility and the size of particles. Soluble arsenic compounds are easily absorbed from

the gastrointestinal tract. However, inorganic arsenic is extensively methylated in humans

and the metabolites are excreted in the urine. Arsenic (or metabolites) concentrations in

blood, hair, nails and urine have been used as biomarkers of exposure. Arsenic in hair and

nails can be useful indicators of past arsenic exposure, if care is taken to avoid external

arsenic contamination of the samples.

Inorganic arsenic is acutely toxic and intake of large quantities leads to

gastrointestinal symptoms, severe disturbances of the cardiovascular and central nervous

systems, and eventually death. In survivors, bone marrow depression, haemolysis,

hepatomegaly, melanosis, polyneuropathy and encephalopathy may be observed. Ingestion

of inorganic arsenic may induce peripheral vascular disease, which in its extreme form

leads to gangrenous changes (black foot disease, only reported in Taiwan). Populations

exposed to arsenic through drinking water show excess risk of mortality from lung, bladder

and kidney cancer, the risk increasing with increasing exposure. There is also an increased

risk of skin cancer and other skin lesions, such as hyperkeratosis and pigmentation changes.

Studies on various populations exposed to arsenic by inhalation, such as smelter

workers, pesticide manufacturers and miners in many different countries consistently

demonstrate an excess lung cancer. Although all these groups are exposed to other

chemicals in addition to arsenic, there is no other common factor that could explain the

findings. The lung cancer risk increases with increasing arsenic exposure in all relevant

studies, and confounding by smoking does not explain the findings. The latest WHO

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evaluation concludes that arsenic exposure through drinking water is causally related to

cancer in the lungs, kidney, bladder and skin, the last of which is preceded by directly

observable precancerous lesions. Uncertainties in the estimation of past exposures are

important when assessing the exposure–response relationships, but it would seem that

drinking water arsenic concentrations of approximately 100 µg/l have led to cancer at these

sites, and that precursors of skin cancer have been associated with levels of 50–100 µg/l.

The relationships between arsenic exposure and other health effects are less clear. There is

relatively strong evidence for hypertension and cardiovascular disease, but the evidence is

only suggestive for diabetes and reproductive effects and weak for cerebrovascular disease,

long-term neurological effects, and cancer at sites other than lung, bladder, kidney and

skin.

METHODS ON REMOVAL OF HEAVY METALS

The separation of heavy metal ions presented as contaminants in water is

complicated by the number of variables that must be considered, including the solution

composition, the pH, and the presence of organic substances. Also a challenge encountered

in the removal of heavy metal ions is that the target species are usually in low

concentrations and exist in complex mixtures. Various methods have been used in the

removal of heavy metal ions, including chemical precipitation, solvent extraction, ion

exchange, evaporation, reverse osmosis, electrolysis and adsorption (Harrison, 1990).

Chemical precipitation

This is the most traditional, common and simple method. The conventional way to

separate heavy metals from the wastewaters they are dissolved in is to adjust pH to cause

metal precipitation by the addition of lime or other anionic polyelectrolyte. For example,

Janson et al. (1982) used hydroxide precipitation method to remove Zn2+, Pb2+, Cr3+ by

adjusting the pH of the solution to a value greater than 10. Cu2+ can be removed by forming

heavy metal sulfide precipitation. However, Hg2+ cannot be effectively removed by

chemical precipitation. The precipitation method produces a large amount of sludge, which

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transforms an aquatic pollution problem to a solid waste pollution problem. In addition,

chemical precipitation is usually inefficient to deal with low concentration of heavy metals.

Solvent extraction

It is extensively utilized in organometal removal from wastewater. The extractant is

capable of ion exchanging or forming chelates with the metal ions to be removed. Upon

mixing, the metal ions are transported to the organic phase. The phases are allowed to

separate, and the metal ions are stripped from the loaded organic phase. The concentrated

metal ion solution can then be purified or disposed. Solvent extraction offers the

advantages of fast kinetics, high capacities and selectivity for target metal ions. The finite

aqueous solubility of the extractant, solvents and modifiers is, however, a significant

disadvantage (Ritcey and Ashbrook, 1979). It not only adds to the cost of the process

through loss of reagents, but also contaminates the water with potentially toxic organics.

There is also loss of the organics through evaporation and entrainment. In addition, solvent

extraction is not recommended for diluted metal ion solution due to the large volumes of

extractants needed (Beauvais and Alxandratos, 1998). Solvent extraction may not be

effective to inorganic species of heavy metal ions.

Reverse osmosis

It is employed for the recovery of precious and common metals in the metal

finishing industry. Reverse osmosis can show excellent performance in treating

wastewaters containing a single metal or a mixture of metal ions. However, there are certain

drawbacks which have limited its wide applications in industrial effluents. In particular,

the process requires high pressures (up to 100 atmospheres) and is thus fairly costly in

terms of energy. The delicacy of the membranes is also restrictive with regard to the solid

content to be handled and the pH of the liquids to be treated. Nevertheless, the process has

been used for the effluents from electroplating in the electronic components industry. With

the continuous development of the process and improved mechanical strength of

membranes, the range of applications can be expected to increase (Harrison, 1990),

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especially if other removal methods cannot effectively reduce the concentrations of heavy

metals to the desired or required levels.

Evaporation

This is one of the most common methods used in industry for the concentration of

aqueous solutions. Nevertheless, the use of this process as a means for effluent treatment

is rare and occurs only under special circumstances where the effluent contains a high

concentration of static rinses from electroplating operations, particularly chromium

plating. In this application the rinse liquor is evaporated to a metal concentration which

makes the concentration suitable for direct re-use in the plating bath (Harrison, 1990).

Electrodialysis

Electrodialysis separates an aqueous flow under the influence of an electric field

into an enriched stream and a depleted stream. Among the applications of electrodialysis

are the production of potable water from brackish waters, deminerization of cheese whey,

treatment of acid mine drainage, desalting of cooling tower waters, and removal of metals

from plating wastes (Nriagu, 1979). The cost of electrodialysis is very dependent on

dissolved solids concentration. It does not find common use in effluent treatment but may

be appropriate in certain circumstances where the concentrate is of value.

Ion exchange

In recent years, ion exchange resins have been applied in heavy metal ion

adsorption. Ion exchange is one of the most effective techniques for removing heavy metals

from wastewaters. The resins contain functional groups capable of complexing or ion

exchanging with metal ions. The process is employed extensively for metal finishing bath

purification, effluent polishing after primary treatment, and recovering precious metals.

The resin is contacted with the contaminated solution, loaded with metal ions, and stripped

with an appropriate elute (Beauvais and Alexandratos, 1998). Beker and co-workers (1999)

synthesized ion exchange resin based on hydroxethyl cellulose and applied the ion

exchange resin in Fe3+, Co2+, Cu2+, Zn2+ ions removal. However, ion exchange has

18

problems in treating aqueous wastes containing mixtures of metal ions due to low

selectivity of metal ions. Another disadvantage of ion exchange resins is the slow kinetics,

as compared to solvent extraction, although increasing the porosity of the resin or

decreasing the size of the beads can improve the kinetics. In addition, although heavy metal

ions can be removed effectively, in many cases, from wastewaters by means of ion

exchange, most ion exchange resins are too expensive to be discarded once they have been

loaded with heavy metals. The resins must therefore be regenerated and regeneration again

yields a solution of heavy metals which is hard to be disposed of. Regeneration with very

concentrated acids or bases has been recommended to reduce the volume of the

regeneration liquid that must be disposed of, but the concentration technique is not

effective for recovery of ion exchanger. Most important of all, synthetic resins have a poor

contact with aqueous solutions and their modification and/or pretreatment by activation

solvents are necessary for enhanced water wettablility.

Adsorption

In addition to other conventional methods, adsorption is another effective and

widely used method to remove heavy metal ions. Adsorption technology has good potential

to treat waster and industrial residues because it is cost-effective, easy for application and

efficient in various kinds of heavy metal removal. Various adsorption materials have been

studied, such as activated carbons, clays, polymeric synthetic resins, metal oxides, and

some natural materials. Among them, activated carbon is one of the oldest and most

commonly used adsorbents. Adsorption by activated carbon is an established treatment

method for organic contaminants but has been rarely used in an actual treatment setting for

inorganic adsorbates, despite the fact that the ability of activated carbons to remove heavy

metal ions has been established by numerous researchers. For example, adsorption with

activated carbon has been reported for Cu2+, Cd2+, Zn2+, Pb2+, Hg2+, CO2+, Mn2+, Ca2+, Ni2+,

Cr3+ (Dastgheib and Rockstraw, 2002). However activated carbon has some disadvantages

in heavy metals removal. Firstly, the adsorption capacity and kinetics for many metals,

such as Mn2+, Pb2+, CO2+, Zn2+ ions are rather poor. Secondly, activated carbon is

19

expensive (activated carbon adsorbents are sold at market price about US$20-22/kg, and

the higher the quality, the greater the cost). Thirdly, the regeneration of activated carbon is

another challenge, which usually requires thermal chemical process that is expensive, and

causes loss of the adsorbent. Hence, the search for alternative and more effective

adsorbents has attracted great interests in heavy metal removal.

Bioadsorption

As a sub branch of adsorption, biosorption aims to use cheaper materials of

biological origins as adsorbents and has developed rapidly in the last one or two decades.

Biosorption, a passive non-metabolically mediated process, removes metals or metalloid

species, compounds and particulates from solution, by materials of living or dead biomass

(Gadd, 2001) and has served as an important means for purifying industrial wastewaters

containing toxic heavy metal ions. Bioadsorption has the following advantages (Volesky,

2003):

Using cheap raw materials (usually naturally abundant or a waste from other

industries), bioadsorption allows significant cost savings in comparison with

existing competing technology, i.e. ion exchange, its close rival.

Biosorption is more effective than its closest rival, ion exchange in performance,

due to its low sensitivity to environmental and impurity factors.

Additional value may come from the possible recovery of heavy metals as the

sorbed metal ions can be easily desorbed.

Lagenaria siceraria

The bottle gourd is one of humankind's first domesticated plants, providing food,

medicine and a wide variety of utensils and musical instruments.

Description

Vigorous annual herb. Stems prostrate or climbing, angular, ribbed, thick, brittle, softly

hairy, up to 5 m long, cut stems exude no sap. Leaves simple, up to 400 mm long and 400

20

mm broad, shortly and softly hairy, broadly egg-, kidney- or heart-shaped in outline,

undivided, angular or faintly 3-7-lobed, lobes rounded, margins shallowly toothed, crushed

leaves non-aromatic. Leaf stalks up to 300 mm long, thick, often hollow, densely hairy,

with two small, lateral glands inserted at the leaf base. Fruit large, variable, up to 800 x

200 mm, subglobose to cylindrical, flask-shaped or globose with a constriction above the

middle; fleshy, densely hairy to ultimately glabrous, indehiscent, green, maturing

yellowish or pale brown, pulp drying out completely on ripening, leaving a thick, hard,

hollow shell with almost nothing inside except the seeds. The fruit often is an indehiscent

berry (soft-shelled) or gourd (hard-shelled) with one to many, often flattened seeds. Seeds

many, embedded in a spongy pulp, 7-20 mm long, compressed, with two flat facial ridges,

in some variants rather irregular and rugose.

Distribution

It is generally accepted that lagenaria siceraria (previously known as lagenaria

vulgaris) is indigenous to Africa and that it reached temperate and tropical areas in Asia

and the Americas about 10 000 years ago, with human help or probably as a wild species

whose fruits had floated across the seas. Fruits are known to float in the sea for many

months without the seeds losing their viability. Independent domestications from wild

populations are believed to have occurred in both the Old and New Worlds. African and

American land races (subsp. siceraria) are morphologically distinct from Asian land races

(subsp. asiatica). It is uncertain if the seemingly spontaneous populations in Africa are truly

wild.

In southern Africa the calabash flowers mainly in April and May and fruits mainly

from April to July. In this region it grows from about 245-1 265 m above sea level, in areas

with a rainfall of about 400-600 mm annually. Heiser (1997) observed that the bottle gourd

flowers are pollinated at night by hawk-moths and other moth species; by day bumble bees,

cucumber beetles and other insects are active. In the Americas hummingbirds are also

21

attracted by the nectar that only the male flowers produce. He also observed that about 40

male and about 3 to 4 female flowers occur on a single plant.

According to Watt & Breyer-Brandwijk (1962), human poisoning has been reported

from eating the fruit, presumably of the bitter form. (As with other members of the

Cucurbitaceae, e.g. Cucumis africanus, some plants of L. siceraria produce bitter,

poisonous fruits and others non-bitter, edible fruits). Various medicinal uses of the leaves,

fruit and seeds have been recorded from various countries, e.g. as a pectoral, an

anthelmintic, a purgative and even as a headache remedy.

In rural southern Africa and elsewhere in developing countries, the calabash fruit is

still widely used for various kinds of household containers and utensils. Non-bitter types

are used to store water, milk and beer. These calabashes and products made from them are

commonly sold as ornaments at roadside stalls and curio markets.

The calabash can be grown from seed in frost-free areas. It prefers sandy or loamy

soil, some shade, good rainfall or enough water. It can be treated either as a prostrate

ground cover or as a climber, in which case the maturing fruit might need some support.

Adsorption models

Isotherm adsorption models have been used in waste stream treatment to predict the

ability of a certain adsorbent to remove a pollutant down to a specific discharge value.

When a mass of adsorbent and a waste stream are in contact for a sufficiently long time,

equilibrium between the amount of pollutant adsorbed and the amount remaining in

solution will develop. For any system under equilibrium conditions, the amount of material

adsorbed onto the media can be calculated using the mass balance of equation below:

𝑞𝑒 = 𝑉 × 𝐶0 − 𝐶𝑒

𝑚𝑠

22

where C0 and Ce (mg/L) are the initial and the final concentrations of adsorbates in flasks,

respectively, V is the volume of the solution (in Litres) and ms is the mass of dry adsorbent

used (in grammes).(Wang et al., 2010)

Adsorption isotherms are important criteria in optimizing the use of adsorbents as

they describe the nature of interaction between adsorbate and adsorbent. Thus, analysis of

experimentally obtained equilibrium data by either theoretical or empirical equations is

useful for practical design and operation of adsorption systems. The Langmuir and

Freundlich adsorption isotherms were applied to each metal under study.

Langmuir Isotherm

Langmuir equation relates the coverage of molecules on a solid surface to

concentration of a medium above the solid surface at a fixed temperature. This isotherm

based on three assumptions, namely adsorption is limited to monolayer coverage, all

surface sites are alike and only can accommodate one adsorbed atom and the ability of a

molecule to be adsorbed on a given site is independent of its neighbouring sites occupancy.

By applying these assumptions, and a kinetic principle (rate of adsorption and desorption

from the surface is equal), the Langmuir equation can be written in the following form:

𝑄𝑒 =𝑄𝑚𝑎𝑥 × 𝑏 × 𝐶𝑒

1 + 𝑏𝐶𝑒

Where:

Ce – equilibrium concentration of metal ions in the liquid

Qe – equilibrium concentration of metal ions in the solid phase

Qmax – Langmuir constant for maximum metal uptake

b – Langmuir sorption equilibrium constant

The above Langmuir equation is often written in the linear form as follows:

𝐶𝑒

𝑄𝑒

=1

𝑄𝑚𝑎𝑥

𝐶𝑒 +1

𝑏 × 𝑄𝑚𝑎𝑥

23

Qmax and b can be calculated from the slope and intercept of the linear plot, Ce/qe versus

Ce. That is, Qmax = 1/slope and b = 1 / (intercept,Qmax).

Freundlich Isotherm

Freundlich isotherm is an empirical equation. This equation is one among the most

widely used isotherms for the description of adsorption equilibrium. Freundlich isotherm

is capable of describing the adsorption of organic and inorganic compounds on a wide

variety of adsorbents including biosorbent. This equation has the following form:

𝑄𝑒 = 𝐾𝑓𝐶𝑒1/𝑛

Where:

Qe and Ce are the equilibrium concentrations of metal ions in the adsorbed and liquid

phases

Kf is the Freundlich constant characteristic of the system, indicating the capacity

n is the Freundlich constant characteristic of the system, indicating the adsorption

intensity

This equation can also be expressed in the linearized logarithmic form as follows:

𝑙𝑜𝑔𝑄𝑒 = 𝑙𝑜𝑔𝐾𝑓 + 1

𝑛𝑙𝑜𝑔𝐶𝑒

The plot of log Qe versus log Ce has a slope with the value of 1/n and an intercept magnitude

of log Kf. Thus, the Freundlich constants Kf and n can be calculated from the intercept and

slope of the linear plot of log qe versus log Ce. log Kf is equivalent to log Qe when Ce equals

unity. However, in other case when 1/n 1, the Kf value depends on the units upon which Qe

and Ce are expressed. On average, a favourable adsorption tends to have Freundlich

constant n between 1 and 10. Larger value of n (smaller value of 1/n) implies stronger

interaction between biosorbent and heavy metal while 1/n equal to 1 indicates linear

24

adsorption leading to identical adsorption energies for all sites. This isotherm attempts to

incorporate the role of substrate-substrate interactions on the surface. (Febrianto et al.,

2009; Reddy et al., 2010)

25

CHAPTER THREE

MATERIAL AND METHODS

MATERIALS

Lagenaria siceraria will be gotten from Ikot Ekpene, LGA, Akwa Ibom state or from

the Department of Crop Science, University of Uyo, Uyo, Akwa Ibom state. The produced

water will be gotten from a location field in the southern part of the country.

METHODS

Lagenaria siceraria dry shells will be collected in bulk, crushed and washed in cold

water to remove dust and dirt before drying them in an oven at 700C for 24 hours. The seed

and shell will be ground to powder using mortar and pestle. The grounded powder will be

sieved using a desired mesh size to aid in removal of larger particles and also to have a

certain diameter range. The powder gotten from the shell and the seed will be separated

and dried at room temperature in open air on a slab. A portion of the seed and shell will be

taken separately and slowly heated until it turns to charcoal over a Bunsen burner.

EQUIPMENTS

The following equipment will be used during the entire project:

a. pH meter

b. Atomic Adsorption Spectrophotometer

c. Acid and Alkaline solution

d. Oven

e. Water bath

f. Laboratory stirrer

g. Beaker

h. Whatman filter paper

EXPERIMENTS TO BE CONDUCTED

1. Determination of pH value

26

2. Effect of contact time

3. Effect of initial metal ion concentration

4. Effect of dosage

5. Effect of agitation

6. Adsorption isotherms

WORK PROGRAMME

S/N Activities Weeks

1 Material collection 1

2 Pre-treatment of material 2 to 3

3 Consultation with laboratory technologist 3 to 4

4 Laboratory experiments 5 to 9

5 Discussion of results 9 to 11

27

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