OPTIMIZATION OF ACTIVATED CARBON PREPARATION FROM CORNCOB WASTEWATER TREATMENT
CHAPTER ONE
INTRODUCTION
Background of the Study
Water is a limited natural resource and fundamental for life and health (UNWWDR, 2002). About 97.5% of all water on earth is salt water and the remaining 2.5% is fresh water. Around 70% of fresh water is frozen in the Antarctica and Greenland icecaps. Only 1% of the earth‘s fresh water is accessible for extraction and human use (Corcoran, 2010). Water is important for life and for processing various materials in industry. Living organisms cannot exist without water, and almost all industries require water to operate. However, in the 21stcentury the growing population and industrial sector have contributed significantly to a reduction in quality of water and its availability through discharge of untreated wastewater to the environment; thus becoming the concern of many nation across the world (Kapanji, 2009; Sato et al., 2013). Globally, every day more than two million tons of liquid waste are released from point and nonpoint sources into both subsurface and surface water bodies without treatment (Corcoran, 2010).
For example, in Nigeria has used 18% of 49 million m3of its wastewater generated in volume per annum without treatment for agricultural production and other purposes, while the remaining wastewater is discharged into nearby water bodies such as rivers, springs, streams, and lakes (Corcoran, 2010; GTP-MoFED, 2010; Sato et al., 2013). In Addis Ababa, around 390 hectares of land for vegetable farming is irrigated with the contaminated Akaki river, reported to contain high amounts of toxic heavy metals (Ni, Cd, Cr, Zn, Cu, Mn and Pb), and found in the tissues of vegetables (lettuce, swiss chard, cauliflower, cabbage and kale). This shows that, industrial wastewater needs to be treated before being used for irrigation purposes (Itanna, 2002; and Beyene, 2011). The sustainability of the environment has become a critical global issue (Dişli, 2010) and the protection of fresh water bodies from various contaminants has become a major challenge facing the planet earth (Chaturvedi 2014). Among the major causes of environmental pollution is the discharge of untreated industrial wastewater containing toxic chemicals such as heavy metals (Kulkarni 2014). A direct industrial wastewater discharge into fresh water bodies is a usual practice particularly in less developed countries like Nigeria, where no stringent environmental regulations have been enacted (Asfaw, 2007; Zinabu, 2011; Belay and Sahile, 2013). The release of toxic chemicals from industrial wastewater into the environment degrades water quality and is hazardous for human beings, as well as, other living organisms such as aquatic life (Ahluwalia and Goyal, 2007).
The composition of heavy metals from industrial wastewater is a major concern for the environment, based on the rich of copper (Cu), lead (Pb), chromium (Cr), cadmium (Cd), (Zwain et al., 2014). Population growth, an increase in development and the expansion of investment in the industrial sector has led to the rise in demand for industrial products. The expansion and development of various types of industries can result in generating huge volumes of wastewater along with complex toxic chemical compositions which demand advanced technological treatment techniques (Corcoran, 2010; Keng et al., 2013; Zwain et al., 2014). Subsequently, most industries in less developed countries discharge huge volumes of raw wastewater to water bodies, causing environmental and health damage to the local population.
As a result of industrialization and urbanization, the volume of wastewater generated from the Nigerian industrial sector has increased rapidly. From 1980 to 1990, the toxic load discharged per unit of industrial output increased by 1.8, which was about 1.3 times higher than sub-Saharan African countries such as Swaziland, Seychelles and others (UNIDO, 2001; Sato et al., 2013; Tegegn, 2014). Investment inflow into Nigeria to establish industries is increasing for example, the contribution to Gross Domestic Product (GDP) from industry is expected to increase to 19.1% at the end of the Growth and Transformation Plan (GTP) 2014/15 from 8.1% in 2004/05 (GTP-MoFED, 2010; FDRE-CRGE, 2011). As a consequence to prevent increasing environmental and health related problem, Nigeria faces a challenge to effectively treat the industrial wastewater discharge. As with other developing countries, Nigeria cannot afford to use advanced technologies for the treatment of contaminated water. Accordingly, it is crucial to explore locally available materials for the treatment of industrials wastewater. The adsorption principles are cost-effective, simple to design and operate locally available materials corn cob activated carbon (CCAC) will be investigated for adsorptive removal of Pb2+ from synthetic wastewater under batch experiments. The findings of this study will used an input for the exploring and development of low-cost adsorptive removal techniques for the effective treatment of industrial wastewater.
Statement of the Problem
Agricultural Development Led Industrializations (ADLI) is the basic road map for Nigerian development (GTP-MoFED, 2010; FDRE-CRGE, 2011). Development of the country is currently based on ADLI. So far, industrial development is beginning to be realized in the leather industry and other agriculturally based processing industries, such as beverages and food, textiles, and the sugar industry. During future implementations of the Growth and Transformation Plan (GTP-MoFED, 2010; FDRE-CRGE, 2011) important strategies will be enacted into promote environmentally sustainable, agriculturally based processing industries. Others industries, such as chemical, textile, cement, pharmacologic and metal industries are also rapidly growing. Continued population growth and rapid industrialization are found to be the cause of wastewater discharge into the environment, affecting the environment, human health and compromising the life of future generations.
In the capital city, Addis Ababa, an estimated annual volume of 49 million m3 total wastewater is discharged, of which about 4 million m3 is industrial wastewater, with only 4% of the wastewater being treated and reused (Gupta, 2003; Qadir et al., 2010; Van Rooijen et al., 2010; Krishna, 2011). The techniques are currently being implemented in Nigeria are conventional treatment methods. However, these conventional treatment processes require large investments making their application unaffordable for developing countries, like Nigeria (Mandal, 2014).
The liquid waste discharged from industries contains heavy metals toxic to living organisms (Barakat, 2011). Heavy metals of urgent environmental concern are lead, chromium, mercury, cadmium, copper, zinc, and iron. Among these heavy metals, Lead (Pb2+) is hazardous and carcinogenic and discharged from most industries above permissible limited set by Nigerian environmental protection agency. A number of technologies have been developed over the years to remove toxic heavy metals from waste water.
One of the most commonly used techniques involves the process of adsorption, which is the physical adhesion of chemicals onto the surface of solid. Adsorption as a process, employed due to its low cost and applicability on large scales. Adsorption is commonly being done using activated carbon, which adsorbs dissolved organic substances in the water treatment and although activated carbon has several advantages, such as its effectiveness in removing high concentrations or organic and inorganic compounds. (Agbozu & Emoruwa, 2014)
Unfortunately, like other developing countries, Nigeria cannot afford to use advanced treatment technologies to deal with toxic industrial wastewater, therefore, it is crucial to explore locally easily available agricultural waste corn cob as an activated carbon for removal of lead ions. Since corn crop is the second most grown cereals for wide variety of applications in Nigeria and the corn cobs often leaves in the fields has very low economic value. The efforts of using the corn cobs as a biomass fuel has not given very promising results primarily because of the low calorific value of corn cobs. Another alternate route to convert these waste corn cobs to high economic value product can be to convert them into more commonly called as activated carbon for treatment of industrial pollution is promising contribution for developing country like Nigeria to treat their waste water before discharged into the environment. The use of various precursors such Coffee husk, Bamboo steam and lignite coals for producing activated carbon has been studied in detail by several researchers. However, no sufficient research to investigate these issues particularly in Nigeria Corncobs activated carbon as potential adsorbent to remove heavy metal lead from wastewater. Therefore, the research is conducted to treat the lead contaminant before discharge into environment using a locally available corn cobs activated carbon (CCAC).
Research Objectives
The main objective of this research is to study the optimization of activated carbon preparation from corn cob wastewater treatment.
1. To find optimal operational conditions during corn cob activated carbon preparation process.
2. To characterize corn cob activated carbon.
3. To determine the effect of initial concentration of the adsorbates, pH solutions and adsorbent dose by using a batch adsorption technique.
4. To analysis the adsorptive capacity and equilibrium isotherm of corn cobs activated carbon under batch adsorptive experiments.
5. To generate statistical models that fit the experimental data through the use of a full factorial design analysis approach.
Significance of Study
A major challenge of many industries is finding solutions that equate to positive environmental and economic impacts regarding the treatment of their effluents. Solution to this challenge is of uttermost importance to enable improvement of water quality. Since the activated carbons employed in this study are derived from natural sources, they can represent economic and environmental friendly alternatives to conventional adsorbent (commercial activated carbon).
The study can also provide fundamental information in the adsorption of lead metal ions, from aqueous solution. Knowledge of the mathematical models employed in this study could serve as a useful guide for further experimental work, provide predictions of the performance of the adsorption process under different operating conditions and again provide essential information in the design of adsorption treatment system for the treatment of heavy metal bearing effluents.