In this study, calcined eggshell powder was used as low-cost adsorbent to remove copper (II) ion from aqueous solution by adsorption. Effects of operational parameters such as contact time, adsorbent dosage, initial concentration and temperature were determined for optimum removal. Results shows a maximum removal of 99.96167% at 30 minutes, 1.5g, 300mg/L and 35. Equilibrium adsorption isotherms, kinetics and thermodynamics were investigated. Langmuir and Freundlich models were used to analyse the experimental data and the isotherm data fitted well to the Langmuir isotherm with monolayer adsorption capacity of 4.5024 mg/g. Adsorption kinetic study revealed that pseudo-second order with correlation coefficient value of 0.9361 best fit to experimental data compared with pseudo-first model. Thermodynamics studies describes the adsorption reaction process as non-spontaneous, increasing in rate with increase in temperature, endothermic and irreversible in nature.
Water is an essential substance for the existence of mankind on earth because of its vital function to man and his environment. The sources of water are; surface water such as streams, rivers, lakes, seas and oceans, ground water such as wells, boreholes, and rain water which is obtained from the physical action of condensation of water vapour that evaporates from the surface of the earth. The rain water replenishes underground and surface water. It is interesting to note that 71% of the earth’s surface is covered by water. This is unevenly distributed between seas and oceans, ground water, glaciers and ice cap and in air (as vapour clouds and precipitation) in percentages of 96.5%, 1.7%, 1.7% and 0.001% respectively. Of these, only 2.5% is fresh water and 98.5% of that water is ice and ground water.
With the increase in industrialisation, water pollution has been a major issue of hazard to man and his environment. Water pollution as defined by Wikipedia is the contamination of water bodies. These contaminants are classified as; physical contaminants (primarily impact the physical appearance or other physical properties of water), biological contaminants (organisms in water), radiological contaminants (chemical elements with an unbalanced number of protons and neutrons resulting in unstable atoms that emit ionizing radiation) and chemical contaminants (elements or compounds including nitrogen, bleach,, salts, pesticides, toxins produced by bacteria, and human or animal dung and metal) of which this study falls under. (USEPA, 2016). Two different groups are used to categorise the factors that are instrumental in water pollution namely; point sources and non-point sources. (Menon, 2011). Point sources are direct sources of water pollution that are identified and controlled (reduced and monitored) easily, some examples are factories, sewage systems, power plants, underground coal mines, oil wells. Non point sources are ambiguously defined and harder to control they include a wide range of sources such as; when rain or snow moves through the ground and picks up pollutants as it moves towards a major body of water, the runoff of fertilizers from farmland, air pollutants deposited on earth. This has necessitated the need for water treatment process. (Menon, 2011).
The wellbeing of the environment, society and the economy is a factor of the quality of water (Corcoran et al.; 2010). Waste water is water that has been negatively affected in quality by anthropogenic influences. Wastewater is defined as a combination of one or more of; domestic effluents consisting of black-water (excreta, water and faecal sludge) and grey water (kitchen and bathing wastewater); water from commercial establishment and institutions, including hospitals ; industrial effluent, storm water and other urban run-off; agricultural, horticultural and aquaculture effluent, either dissolved or as suspended matter (Corcoran et al; 2010).
Heavy metals are naturally occurring elements that play major roles in the industry. Heavy metals present in trace amounts are required in some biological processes; Iron and copper (oxygen and electron transport); zinc (hydroxylation); cobalt (complex syntheses and cell metabolism) (Nielboer and Richardson, 1978) to mention but a few. Although heavy metals have proven to be useful in the industry, some have negative effect on both the environment and on man hence the need for their removal from waste water.
Methods such as chemical precipitation, chemical coagulation, ion-exchange, electrochemical method, membrane process and ultrafiltration can be employed in removal of heavy metals from water. The methods are relatively expensive and the agencies responsible for the provision and distribution of potable water; water board, waste sewerage authority (WASA), rural urban development agency (RUDA), rural urban water supply agency (RUWASA), water resources employ the conventional water treatment process (involving a series of steps; aeration, coagulation, flocculation, sedimentation , clarification, filtration and disinfection), which is sufficient in the removal of physical and biological contaminants only and not chemical contaminants.
Research efforts has/is been made in the determination of a cheap, easily accessible and replicated method of hard metal removal. In developing countries such as Nigeria, water treatment plants are expensive. The ability to pay for services is minimal and skills as well as technology are scarce. In other to alleviate the prevailing difficulties, approaches should be focus on sustainable water treatment systems that are low cost, robust and requires minimal maintenance and operating skills. Locally available materials can be exploited towards achieving sustainable safe potable water supply (Aho and Lagasi, 2012). This makes adsorption and the use of eggshell as an adsorbent a contender as a substitute method of water treatment.
Heavy metals have a wide application in the industry, hence they are present in the industrial effluents generated at the end of a process. They are introduced into the environment during these effluents disposal and generally enter the body by ingestion, inhalation and adsorption through the skin or mucous membrane (Jackson and Henderson, 2016) adversely affecting the system; environment and man. Methods of heavy metal removal is therefore required and important to avoid this.
1.2 Research Problem
The generation of waste water containing heavy metals has become an issue as their release into the environment has increased as a result of industrialisation. This waste water contains amounts of heavy metal that are harmful to the environment and man who is likely to come in contact and use this water. Legislations have been put in place prompting industries to treat the waste water they generate before it is disposed of. This increases the operational cost of a manufacturing process and hence the need for a relatively cheap, easily accessible and replicated method of waste water treatment. The need for the proper disposal of eggshell currently being used as landfills also makes this study important.
1.3 Aim and Objectives
The aim of this research is to study the effectiveness of eggshell as an adsorbent in the removal of cobalt ii ion from aqueous solution providing an affordable and easy substitute for water treatment. The objectives are:
1. Preparation of adsorbent from waste chicken eggshell.
2. Characterisation of adsorbent using FTR, SEM, and XRD techniques.
3. Testing the adsorption capacity of as-synthesised eggshell adsorbent.
4. Optimisation of adsorption variables; contact time, temperature, adsorbent dosage and initial concentration.