CHAPTER ONE

1.0 INTRODUCTION

1.1 Background of the study

Wastewater from several industries such as electroplating, tannery, mining and steel contains

high levels of heavy metals including chromium, cobalt, copper, nickel, zinc, mercury and lead

(Mansoor and Anujkumar., 2018). There are many electroplating plants operating in different

municipalities. Such electroplating plants however have the potential of generating wastewater

that contains substantial amounts of heavy metals like copper, nickel, zinc, chromium, cadmium

(Donatus et al., 2016). It is an established fact that rapid progress of technological innovations

made it virtually impossible to do without the use of metals and therefore the environment is

mundated with excess of metals either biologically essential or non-essential which has led to the

present age fright. Nowadays, the concentrations of heavy metals are high in the loctic and lentic

water due to the release of wastewater and agricultural runoff (Otene and Alfred. 2019).

A few years ago, various techniques and method have been used for the purification of water

such as chemical precipitation, floatation, adsorption, ion-exchange, extraction, membrane

filtration and dialysis (O'Connel et al., 2008). Adsorption has shown to be promising alternative

for Wastewater treatment as it's economically favorable, technically easy and Environmental

friendly (kurniawan et al., 2005).This involved the use of natural and waste material as

Adsorbent in heavy metal removal. Activated carbon appears to be particularly competitive and

effective for the removal of heavy metals at trace quantity (Acharya et al., 2009).Activated

carbon produced from agricultural waste materials has high potential adsorption capacity for the
removal of different pollutants such as odor and taste from drinking water, metals, and chemicals

like herbicides and pesticides (Olawale et al., 2019).

1.2 Statement of the problem

As a result of different human activities, the world is facing serious threats of air, land, and water

pollutions. Water pollution in particular, has raised severe environmental impacts. In addition to

the shortage of resources of water due to drought and misuse, production of large volumes of

wastewater has put a lot of pressure on the humankind.

1.3 Justification of the study

Activated carbon has been considered a very common, economic, environmental and effective

absorbent for removal of heavy metals from wastewater. Adsorption is a very easy and suitable

method for the extraction of heavy metals in waste water. Modification of activated carbon and

mixing it with a base will aid to improve the adsorption capacity and suitable utilization of the

whole step.

1.4 Aims and objective of the study

The aim of this study was to remove heavy metals from wastewater using an activated carbon

produced from an agricultural waste. The aim was achieved through the following objectives:

i. Preparing of Activated carbon (AC) from wheat husk through chemical activation.

ii. To determine some physico chemical parameters such as bulk density, moisture content,

ash content and electrical conductivity.

iii. The treatment of the waste water with activated carbon using batch adsorption studies.
CHAPTER TWO

2.0 LITERATURE REVIEW

Researches has been done on the adsorption of heavy metals from wastewater using locally

made, low cost and environmental friendly agricultural waste as an activated carbon (adsorbent).

In general terms, activated carbons are thought of as being the most effective adsorbents and as

such, their performance in removing contaminants such as heavy metals, radio nuclides, rare

earth elements, phenolic and aromatic derivatives (including dyes and pesticides),

pharmaceuticals and drugs have been examined widely ( Dabrowski et al., 2005).

In the field of wastewater treatment, adsorption onto commercial activated carbon has proved

efficient in the removal of colloidal substance and soluble organic substances that are non-

biodegradable or chemically stable like recalcitrant synthetic molecules. Attention has also been

focused on adsorption onto commercial activated alumina, ion-exchange using organic

polymeric resins and zeolites as other non-consumptive materials. However, despite the

excellence of their performance these systems are expensive to use and as such, cannot be

thought of as a truly viable option in many parts of the world (Wang and Peng, 2010).

Asari et al., (2010), investigated the adsorption behaviour of Zn (II) and Pb (II) ions on rice

husk. The result was shown to depend significantly on the pH, contact time and dosage. The

parameters that influenced Zn (II) and Pb (II) sorption on rice husk were amount of adsorbent,

contact time and pH values of wastewater. The influence of contact time (5 – 70 minutes), pH of

(2 – 9) and adsorbent amount (0.5 – 3 g) were studied. The experimental data were analyzed and

the adsorption behaviour was well described by Langmuir isotherm model.

Idris et al., (2011), studied the kinetic models of Copper and Lead uptake in wastewater using

activated Pride of Barbados shell. In this research work, contact time for the interaction of the

adsorbent with dye effluent was within 30 – 150 minutes and maximum copper adsorption of

96.63% was obtained at 150 minutes, while for lead removal, 85.55% was indicated at contact

time of 30 minutes and the pseudo first order and pseudo second order models were used to test

the adsorption of these metals.

Koel et al., (2012), studied the use of watermelon shell as an adsorbent for the removal of copper

ions from an aqueous solution. This research incorporates the effect of time, temperature,

concentration, particle size, agitation speed and pH. Batch kinetics and isotherm studied were

also performed to understand the ability of adsorbents. The adsorption behaviour of Cu(II) was

studied using Langmuir, Freundlich and Tempkin adsorption isotherm models. The monolayer

adsorption capacity determines from the Langmuir adsorption equation was found to be 111.1

mg/g. Kinetic measurements suggested the involvement of pseudo-second order kinetics in

adsorptions and were controlled by particle diffusion process. Adsorption of Cu (II) on the

adsorbent was found to increase on decreasing initial concentration, increasing temperature,

increasing agitation speed, increasing pH and decreasing particle size.

Juan Carlos et al., (2012), studied the adsorption of heavy metal ions such as Cr, Cd and Co

using orange peel. It was observed that the solution pH has high influence on the adsorption of

the metals. The maximum removal of Cr ion was at the pH 5 and also at constant temperature of

298 K.

Batch adsorption experiment was conducted on Chromium, Cadmium, Lead, Iron and Copper

using activated carbon produced from coconut shell. The outcome however shows that the
percentage removal for Chromium, Cadmium, Lead, Iron and Copper were 90%, 80%, 88%,

88% and 90% respectively from the initial concentration of 70%, 69%, 68%, 70% and 73% as

dosage increases from 0.4 to 1.2 g (Agbosu et al., 2014).

Okereke et al., (2016), studied on the biosorption of Pb and Cd in textile effluent using Musa

sapientum peel. The study showed the adsorption capacity of Musa sapientum on the removal of

Pb and Cd to be 99.76% and 99.99%, respectively at the dosage of about 2.00 g. It was observed

that the percentage removal decreased as the dosage increased. The most important and currently

used method for purifying of water is chemical precipitation, membrane technique, ion

exchange, electrolytic removal process, adsorption (Fu and Wang, 2011). This is usually used to

treat waste water containing high concentration of heavy metals ions but futile when metal ion

concentration is low. It is has no much benefit to the economy and can produce large amount of

sludge to be treated with great difficulties (Fenglian and wang, 2006). Membrane filtration has

been noted to receive recommendation for the treatment for the treatment of inorganic effluent,

since it is capable of removing not only suspended solid and organic compounds but also

inorganic contaminants such as heavy metals. Depending upon the nature of membrane used and

size of the particles that can be retained to purify water by removing different kinds of organic

and inorganic pollutant species, various types of membrane filtration such as ultra filtration,

membrane filtration, reverse osmosis and electro dialysis have been employed. These methods

have ability to clarify, concentrate and most importantly remove heavy metals from waste water

(Figoli et al., 2010). Ion exchange is a reversible chemical reaction where an ion from solution is

exchanged for a similarly charged ion attached to an immobile solid particle. In this process ions

are exchanged between two electrolytes or between an electrolyte solution and a complex. These

solid ion exchange particle are either naturally occurring inorganic zeolites or synthetically
produced organic resins which has the ability to exchange cations with the metals in the

wastewater.ion exchangers are classified as cation exchangers and anion exchangers which has

positively charged mobile ions are available for exchange (Yang et al., 2001). In electro dialysis

Metal ions are separated through the use of semi-permeable ion selective membranes. An

electrical potential between the two electrodes causes a separation of cation and anion, thus cells

of concentrated and dilute salts are formed. When a mixture containing ionic species is

transferred through the cell compartment, the anions migrate towards the anode and cations

towards the cathode (Chen et al., 2004). The membrane is of two types; cation-exchange and

anion-exchanged membranes. these method has been effective method used for producing

drinking water from salty water and recovery of materials from effluents (Sardzadeha et al.,

2009).

2.1 Water Pollution

Water pollution is a fundamental global issue, which requires regular evaluation and revision of

water resource coverage at all stages (international down to character aquifers and wells). It has

been suggested that water pollution is the main global motive of deaths and diseases (Pink et al.,

2006). Water is typically referred to as polluted when it is impaired by anthropogenic

contaminants and either does not support a human use, such as drinking or undergoes a marked

shift in its ability to support its constituent biotic communities, such as fish. Natural phenomena

such as volcanoes, storms, and earthquakes additionally cause fundamental adjustments in water

quality and the ecological reputation of water. Water infection is a major problem in the

worldwide and it is high time to comprehend the significance of its consequence (Kumud, 2013).

2.1.1 Categories
Surface water and ground water have regularly been examined and managed as separate

resources. Surface water passes slowly through the pores of the soil and becomes groundwater.

Conversely, ground water can also feed surface water sources. Sources of surface water pollution

are commonly grouped into two important categories based totally on their origin (Moss, 2008).

(i). Point Sources

Point source water pollution refers to contaminants that enter a waterway from single and

identifiable source, such as a pipe or ditch. Instance of sources in this class consists of discharges

from a sewage therapy plant, a factory, or a metropolis storm drain. The U.S. Clean Water Act

defines point source for regulatory enforcement purposes. The clean water acts’ definition of

point source was amended to encompass municipal storm sewer systems, as well as industrial

storm water, such as from development sites (Kumud, 2013).

(ii). Non-point Sources

Non point source pollution refers to diffuse contamination that does not originate from single

discrete source. Non point source pollution is regularly the cumulative effect of small amounts of

contaminants gathered from a massive area. A frequent instance is the leaching out of nitrogen

compounds from fertilized agricultural lands (Moss, 2008).

Nutrient run off in storm water from "sheet flow" over an agricultural field or a forest is also

mentioned as examples of non point source of pollution. Contaminated storm water washed-off

of parking lots, roads and highways, referred to as urban runoff, is so often included into the

category of non point source of pollution. However, due to the fact that this runoff is typically

channeled into storm drain systems, and discharged via pipes to nearby surface waters, it turns

into a point source (Kumud, 2013).

2.2 Heavy Metals

The term heavy metal refers to any metal or metalloid material that has a quite high density

ranging from 3.5 to 7 g/cm3 and it is toxic at low concentrations. Heavy metals includes both

essential and non essential trace metals, which may also be toxic to the organisms depending on

their own properties, availability (chemical speciation), and concentration levels. Metals such as

copper, iron and zinc are referred to as be non toxic while nickel, cadmium, manganese, lead,

cobalt, mercury etc. are recognized to be notably toxic. Unlike natural contaminants, these

metals waste are non biodegradable and then accumulating in concentration in water which

brings about serious health hazard (Larous et al., 2005).

Heavy metals in this study can be present in the aquatic system in both dissolved forms (which

can cause toxic effects on a broad variety of organisms, together with vertebrates) and particulate

ones (including adsorbed on sediments, suspended particulate matter or colloids, in transitional

complexes, and Fe/Mn hydroxides nets, linked to organic matter and carbonates (Marcovecchio

et al., 2004).

2.2.1 Copper

Copper is very important to all living things as a trace dietary mineral because it is a major

component of the respiratory enzyme complex cytochrome oxidase. Gram amounts of the

different copper salts have infatuated in suicidal efforts and gave an acute copper toxicity in

human. Perhaps, due to oxidation-reduction cycling and the production of reactive oxygen

species that destructs the DNA. Similar quantities of copper salts (30 mg/kg) are toxic in living

tissues/cells (Johnson et al., 2008).

2.2.2 Iron
Iron absorption is highly moderated by living bodies, which contains no moderated physiological

way of excreting iron (Ramzi, 1999). Excessive dosage of ingested iron can bring about

increasing levels of free iron in the blood. Iron typically damages cells in the heart, liver and

elsewhere, causing negative effect like the coma, metabolic acidosis, shock, liver failure,

coagulopathy, adult respiratory distress syndrome, long term organ damage and even death

(Cheney, 1995).

2.2.3 Manganese

Manganese in water has a greater bio-availability than dietary manganese. According to the

results from a study too much exposure to manganese in water are related with expanded

scholarly hindrance and decreased insight remainders in school age children (Devenyi et al.,

1994). It is hypothesized that long term exposure due to inhaling the naturally occurring

manganese in shower water puts up to 8.7 million Americans at risk (Elsner et al., 2005).

2.2.4 Lead

Lead is a profoundly dangerous metal (regardless of whether breathed in or swallowed),

influencing relatively every organ in human body system. Poisoning typically results from

ingestion of food or water contaminated with lead and less commonly after accidental ingestion

of contaminated soil, dust or lead-based paint and determination of lead in the environment

include spectrophotometry, X-ray fluorescence, atomic spectroscopy and electrochemical

methods (Cama, 2007).

2.3 Adsorption Isotherm

Adsorption isotherm describes the equilibrium distribution of solute between the solid and liquid

phases. The results are usually expressed as a plot of the concentration of chemical adsorbed
(mg/g) versus the concentration of the remaining solution (mg/L) at a constant temperature.

Adsorption isotherm is characterized by certain constant values which express the surface

properties and affinity of the adsorbent and can also be use to compare the adsorptive capacities

of the adsorbent for different pollutants. The analysis of the isotherm data by fitting them into

different isotherm models is an important step to find the suitable model that can be used for the

design process. Adsorption isotherm is basically important to describe how solutes interact with

adsorbents and it is critical in optimizing the use of adsorbents (Tan et al., 2008).

2.4 Kinetics Models

Adsorption kinetics models are used to explain the mechanism and characteristics involved in the

kinetics process. It is the measure of the adsorption uptake with respect to time at a constant

pressure or concentration and it is employed to measure the diffusion of adsorbate in the pores

(Lagergren, 2012).

2.4.1 The Pseudo First Order Model

The pseudo first order equation of Langmuir is generally expressed as;

qt = qe(1 – e-k1t)

where, qe and qt (mg/g) are the amounts of MB adsorbent per unit weight of biosorbent at

equilibrium and at time t, respectively, and K1 is the rate constant of pseudo first order

adsorption (Lagergren, 2012).

2.4.2 The Pseudo Second Order Equation

If the rate of adsorption is a second order mechanism, the pseudo second order chemisorptions

kinetic rate equation is expressed as;

 Dqe/dt = k(qe – qt)2

where qe and qt are the sorption capacity at equilibrium and at time t, respectively (mg/g) and k

is the rate constant of pseudo second order sorption {m/(mg min)}.

For the boundary conditions where, q=0 at t=0 and qt = qt at t=t, the integrated form then

become;

1/t = 1/kqe2 + 1/qe.t

where t is the contact time (min), qe (mg/g) and qt (mg/g) are the amount of solute adsorbed at

equilibrium and at any time t. If the pseudo second order kinetics is applicable then the plot of

t/qt against t should give a linear relationship, from which qe and k can be determined from the

slope and intercept of the plot (Ho et al., 1998).

2.5 Wheat Husk (Triticum aestivum).

Wheat is a grass extensively cultivated for its seed, a cereal grain which is a global staple food.

The numerous species of wheat together make up the genus Triticum, and the most largely grown

is common wheat which is known as Triticum aestivum (James, 2014). The archaeological report

implies that wheat was first cultivated in the regions of the fertile crescent. Botanically, the

wheat kernel is a type of fruit called a Caryopsis. Wheat is grown on a wide land area than any

other food crops vegetation and the specie is largely distributed in Turkey, Syria, Iraq, Damascus

and so forth (Ozkan et al., 2002). World trade in wheat is increased than for all other food-crops

combined in 2016, world production of wheat was 749 million tonnes, making it the second

most-produced cereal after maize (Thomas et al., 2010).

Global demand for wheat is increasing due to the special visco-elastic and adhesive properties of

gluten proteins which helps in the production of processed foods whose consumption is growing

as a result of the global industrialization procedures and the westernization of the diet (Shewry

and Hey, 2015). Wheat is one of the essential source of carbohydrate and globally, it is the

leading source of vegetal protein in human food having a protein content of about 13% which is

relatively high as compared to different major cereals but highly low in protein quality for

supplying fundamental amino acids. When taken as the total grain, wheat is a supplier of

numerous nutrients and dietary fiber (Shewry and Hey, 2015). In a small part of the widely

spread population gluten, the most important part of wheat protein can control coeliac disease,

non coeliac gluten sensitivity, gluten ataxia, and dermatitis herpetiformis (Ludvigsson et al.,

2013).

Plate I: Grains and husk of wheat (Triticum aestivum), (Ozkan et al., 2002).

2.6 Analytical Procedure

Many instrumental analytical procedures may be employed for the determination of

concentration of heavy metals in wastewater or many other samples. One of the most significant

method is Atomic Absorption Spectrometry (AAS).

2.6.1 Atomic Absorption Spectrometry (AAS)

Atomic absorption spectroscopy (AAS) is a spectro-analytical method for the quantitative

determination of chemical elements using the absorption of optical radiation (light) by free atoms

in the gaseous state. Atomic absorption spectroscopy focused on the absorption of light by free

metallic ions. A typical atomic absorption spectrometry consists of a light source usually hollow

cathode lamp, a sample holder usually flame, an atom source, a monochromator, a detector and

an electronic system which process the data and a display system which report the result. The

light source uses a hollow cathode lamp or an electrodeless discharge lamp, specific lamp with

specific wavelength is usually used to determine different elements accordingly. A multi element

lamp can also be used to determine the concentration of many elements without changing the

lamp. In terms of detector, solid state detectors are used in a short while ago to replace the use of

photo multiplier tubes. In order to analyze atoms, the atom source must produce free analyte

atoms from the initial sample and one way to generate free atom is to use the heat produced by

an air or a nitrous-oxide acetylene flame. The sample can be introduced into the flame in a

burner head by a nebulizer in a spray chamber. Then the light been passes through the flame and

the light is absorbed according to the concentration of the atom (Wei and Yang, 2010).
 CHAPTER THREE

3.0 MATERIALS AND METHODS

3.1 Sample’s Collection

The wheat husk was collected in September, 2019 from Abubakar Gumi market, Chanchania

area in Kaduna State.

The wastewater was collected in September, 2019 from a municipal drainage system located at

Mobil area, Minna, Niger State.

3.1.1 Sample’s Pretreatment

The wheat husk was extensively washed with clean water in order to remove soil, dirt or stain

and they were therefore air dried at room temperature for the period of 24 hours. The wheat husk

was dried in an oven at 105 0C for the period of an hour. The dried husk was then pounded into

smaller particles with mortar and pestle and the sample was then sieved to achieve the powdered

form of 2 mm mesh size. The wastewater, after collected into a plastic container, 5 cm 3 of

concentrated HNO3 was introduced into wastewater sample for prevention of microbial growth

action and to prevent the metals from sticking to the container.

3.2 Reagents

Table 3.1: List of Reagents Used.

Chemical Quantity (cm3) Maker

Hydrochloric acid 8.6 Hopkin and Williams Ltd. England Analar Standard
Nitric acid 63.0 BDH Chemicals Ltd. Poole England

Hydrogen peroxide 136 BDH Chemicals Ltd. Poole England

Calcium hydroxide 142 Baker Chemical Co. Philipsburg, N.J

Distilled Water 6000 _______

Key:
BDH = British Drug House
Co = Company
Ltd = Limited.

3.3 Glassware and Other Apparatus

Table 3.2: The Materials and Apparatus Used.

Instruments Model Maker

Beakers --- Pyrex, England
Conical flasks --- Pyrex, England
Measuring cylinder --- Pyrex, England
Volumetric flask --- Pyrex, England
Stirring rod --- Pyrex, England
Oven Size two Galleankamp England
Whatman filter paper --- Whatman Ltd. England
pH meter 3015 Jenway England
Muffle furnace Lenton Thertmal design Ltd. England
Sieve Polythene Dana, Nigeria
Multipurpose flask shaker SSL1 United Kingdom.
Plastic sample bottles Polyethene Dana, Nigeria
Spatula --- Nigeria
Mortar and Pestle Wood Nigeria
Weighing balance Scout Pro SPU 601 Ohaus Cooperation, China.
Conductivity meter Windaus 3302, Zeller Lanortechnik, Germany
Crucibles Ceramic ---
Heating mantle --- Faicotech U.S.A.
Desiccator --- ---
Atomic Absorption Spectrometer Perkin Elmer Analyst 200 ---

3.4 Digestion

10 cm3 of the drainage wastewater sample was made up to 50 cm3 with distilled water in a beaker

and then digested with 6 cm3 of nitric acid (HNO3) and 2 cm3 of hydrogen peroxide (H2O2) at

200 0C for 50 minutes. Then, the digested sample was filtered using filter paper and finally made

up to 100 cm3 of volumetric flask with distilled water.

3.5 Carbonization (Pyrolysis)

The pounded sample was carbonized in a muffle furnace at 500 0C for 10 minutes. As the

carbonization time was reached, 1 M of activating agent Calcium hydroxide Ca(OH)2 was added

and the sample was then brought out and allowed to cool down at the room temperature with

cold water, excess water was then decanted and the sample was dried at room temperature. The

washing off of the activated carbon was done with 0.1 M HCl to remove surface ash, followed
by rinsing with distilled water to remove the residual acid. The activated carbon was then dried

in an oven at 110 0C overnight (Rahman et al., 2005).

3.6 Physico-Chemical Characterization

Some of the physical parameters that were studied to know the properties of wheat husk used as

an activated carbon include:

3.6.1 Determination of Moisture Content

This was done by weighing 2 g of the raw sample into a crucible and kept on an oven at 110 0C

for 4 hours and then transferred into a desiccator to cool down for 1 hour and then it was re-

weighed (Ekpete et al., 2017).

Percentage Moisture = W1 – W2 x 100

W1
W1 is the initial weight of the crucible and sample

W2 is the final weight of the crucible after oven dried.

3.6.2 Ash Content

2 g of the raw sample was weighed and put into a crucible and heated in a furnace at 600 0C for 3

hours. The crucible was then transferred into a desiccator. The cooled sample was then weighed

(Omoniyi et al, 2014).

Percentage Ash = W2 – W0 x 100

W1 – W0

W0 = weght of empty crucible

W1 = weight of crucible + raw sample

W2 = weight of crucible + ash sample

3.6.3 Electrical Conductivity Measurement

0.5 g of the activated carbon was measured and put into a 250 cm 3 beaker and 50 cm3 of distilled

water was added and soaked using a glass rod to wet the sample uniformly. It was then stirred for

30 seconds and it was covered with a glass and allowed to stay for 1 hour. Also, 10 cm 3 of the

extract was decanted into a beaker at room temperature and conductivity meter was used to take

the conductivity.

3.6.4 Bulk Density

This was carried out by pouring the activated sample into a measuring cylinder to a given

volume and compressed by tapping on the bench until the mass of the sample reached the

volume of the cylinder at x.cm3 and the volume stops reducing. The compressed sample was then

weighed and the mass (m) was divided by the volume occupied in the cylinder (Ekpete et al.,

2017).

mass
Bulk density=
volume

3.7 Batch Sorption Experiments

3.7.1 The Effect of Adsorbent Dosage

The effect of adsorption dosage in uptake of Fe, Cu, Pb and Mn were determined by adding 0.5

g, 1.0 g, 1.5 g and 2.0 g of activated carbon into 50 cm3 of the effluent sample, it was then
shaken extensively with the aid of mechanical shaker for a period of 1 hour after which it was

collected, filtered and taken for analysis.

3.7.2 The Effect of Temperature

Batch experiments were conducted using various temperature ranges of 30 0C, 40 0C, 50 0C and

60 0C. To the 50 cm3 of the sample effluent was added 0.5 g of activated carbon and shaken with

the aid of mechanical shaker for period of 1 hour which was then filtered and taken for the

analysis.

3.7.3 The Effect of Contact Time

To determine the optimum contact time, 0.5 g of the activated sample was added to four different

conical flasks containing 50 cm3 of the sample effluent and agitated at room temperature for time

range of 30, 60, 90 and 120 minutes. The mixture was then filtered and taken for analysis.

3.8 Calculation of Metal Uptake

The amount of metal ions adsorbed by the adsorbent is calculated using these equations;

Qe = (Ci - Cf) V
M
Where the Qe is the amount of metal ion adsorbed by the adsorbent in mg/g, C f is the final

concentration in mg/L, Ci is the initial metal ion concentration in mg/L, V is the volume of metal

ion solution and M is the mass of wheat husk used in grams.

The percentage removal of the metal ion was calculated using;

% x = Ci – Cf x 100
Ci
Where x % is the percentage of metal removed, C i is the initial concentration and Cf is the final

concentration.