ABSTRACT
In this study, proximate analysis and characterization techniques were carried out on maize tassel fibres in order to check its feasibility as a bio-sorbent for bio-sorption process before the immobilization with Polyvinyl Alcohol (PVA). The moisture content, ash content, apparent density, particle size and crude protein of maize tassel fibre were determined to show that the bio-material was exceptional for its use in column adsorption. The surface chemistry of the bio-material shows the presence of carboxylic groups and lactonic groups present in the material using Fourier Transform-Infrared spectroscopy (Nicolet 560 spectrophotometer) and Boehmn titration showed the number of acidic sites present in the material. The Brunauer–Emmett–Teller (BET) isotherm (Novastation D version 11.03) was used to find the surface area, pore volume and pore size diameter. The tassel was added to the poly vinyl alcohol at a temperature of 80 ºC with the aid of a magnetic stirrer in the ratio of 2:1 after which it was cooled and extruded with the aid of a syringe to form beads. Column adsorption studies were carried out to investigate the performance of the column by varying flow rates, bed heights and initial concentration on the breakthrough curve to get the breakthrough time and the exhaustion time of the adsorbent bed was used up. The column efficiency was evaluated using Clark model and Thomas model. The proximate analysis revealed moisture content, ash content, apparent density, particle size and crude protein to be 4.51 %, 2.134 %, 0.41 g/ml, 300 μm and 4.06 % respectively for maize tassel fibre. The FT-IR and Boehmn titration showed the number of acidic sites present in the material to be 0.9 mmol/g but the presence of phenolic groups is minimally present in the maize tassel fibre. The Brunauer–Emmett–Teller (BET) isotherm was used to find the surface area, pore volume and pore size diameter to be 652.3 m2/g, 0.4056 cm3/g and 2.144 nm respectively .The Thomas Model was found to predict the breakthrough better than Clark model for the phosphoric compounds with R2 value of 97.5 % for bed heights and flow rates.
CHAPTER ONE
1.0Â Â INTRODUCTION
1.1 Background to the Study
Water is one of the basic needs for all living species alongside with food and air. There are pollutants present in water bodies and among them phosphoric compounds are one of them which causes eutrophication (premature aging of the water body) that leads to the ruins and death of aquatic plants, animals and other living microorganisms. However, one of the major causes of severe water pollution are; Agriculture, industrial development and urbanization (Nguyen, 2015).
Phosphoric compounds occur naturally at low levels in water, plants and animals. It also occurs unnaturally in fertilizers (used in agriculture), cleaning agents (used in industries), wastewater (from household sewage) and bodies of biological organisms. The elevated concentration of phosphates in water body leads to the changes in pH and in water oxygen levels that can be unfavourable to aquatic life. Phosphoric compounds are the major nutrients responsible for eutrophication. Eutrophication occurs as a result of the rapid growth of algae or cyanobacteria bloom due to excess of nutrients in water which acts as a blanket that covers the top of water and inhibits sunlight from reaching aquatic plants. This leads to their death and decline in water oxygen levels (Viswanathan et al., 2014).
The release of industrial and municipal effluents onto land and surface water bodies has polluted water resources such as surface and groundwater, making the management of water resources more complex thereby becoming a threat to the health of human and its population that affects the liver, kidney and heart (Hashem, 2007).
The EPA criterion for acceptable phosphoric concentration in water is 0.1 mg/L or less. The estimated cost of phosphorus removal to achieve a permissible limit of 0.1 mg/L is $44.5 billion in the United States. This only demonstrates the necessity for an effective and inexpensive way to treat phosphorus contaminated waters (Viswanathan  et al., 2014).
Various studies have been carried out to improve procedures and technologies for the removal of phosphoric compounds from water body. These techniques are as follows, physical, chemical and biological methods. From the wide classifications mentioned above, adsorption is the technique that provides the best removal efficiency of phosphoric compounds (Gautam et al., 2014).
Current studies have shown to remove toxic substances from aqueous solutions or from water bodies are the use of adsorbents of biological origin, including alginate, dead and living biomass, chitosan, lignin, and others. Agricultural waste products such as maize tassel (Zvinowanda et al., 2008), rice husks (Krishnani et al., 2007), corn cobs (Kahn and Wahab, 2006) and polymerized orange peels (Guo et al., 2009) have been reported for their removal of toxic substances from aqueous solutions.
The use of raw plant material in water treatment has a major impediment of its susceptibility to bacterial attack that react with the water impurities, which will result to the formation of algae and bacteria that will end up destroying the biomass (Mamba et al., 2012).
The powdered maize tassel is soft and when used alone it clogs the column thus preventing free flow of water. In order to apply this waste material effectively in column experiments, it is essential to immobilize onto an inert substance which can provide support without the maize tassel losing its capacity to remove toxic substances.
Immobilization of such material will create material with mechanical strength and rigidity (Sekhula et al., 2016).
Polyvinyl alcohol (PVA) is a type of synthetic polymer that is easily available, cheap, and possesses tremendous resistance properties; it is a water-soluble material containing large amounts of hydroxide groups. It has inert ability which makes it a good immobilizer (Chu and Hashim, 2006).
This study will focus on the immobilization of maize tassel-PVA for the removal of phosphoric compounds from water body and studying the bed height, varying the initial concentration of the effluent and flow rate for column adsorption.
1.2 Statement of the Research Problem
The pollution of surface water from fish pond can be accredited to runoff from agricultural fields. The pollutants released into the pond can be harmful to aquatic life.
Phosphoric compounds are nutrients that are vital to plant, animal and human growth but needed at low level for survival. However, at high level in nature it can cause algal bloom causing Eutrophication which leads to the depletion of oxygen level in water body there by affecting aquatic life.
There is a trend for substituting pure adsorbents with natural by-products for the development of cost-effective adsorbents. Maize is one of the major staple crops in many developing countries, once the useful nutrient rich portions of maize plants have been harvested, the remaining portion of the plant is usually discarded as waste.
However, it has been reported that during bio-sorption processes there is a problem of leaching of organic matter from the bio-sorbent which leads to change of colour and taste of the final treated water. Metal ions present in the biomaterial can also be leached
into the water when raw biomaterial is used, causing adverse effects on the bio-sorption process. In order to tackle the above challenge, chemical modification is deemed to offer possible solutions.
1.3 Justification of the Study
Maize is a major food crop that is grown in Nigeria in diverse ecological zones and is one of the second most grown crop in Nigeria in terms of area harvested (5.8 million Ha) and second largest in Africa after South Africa with an estimate of 10.79 million MT produced in 2014 (Food and Agriculture Organization Corporate Statistical Database (FAOSTAT), 2014).
In recent years, maize production in Nigeria varied significantly from 7.1 million tonnes in 2006 to 10.4 million tonnes in 2017 (International Institute of Tropical Agriculture (IITA), 2017).
Agricultural wastes are by-products, presently unused or underused for animal feed. These wastes have the following qualities; high cellulose content which is good for adsorption capacity, it is in abundance, eco-friendly, renewable make agricultural solid waste viable option for waste water remediation (Zvinowanda et al., 2008).
Mostly, the materials used for natural biomass materials generally display very low affinity for phosphorus and hereby have relative low sorption capacities. For the enhancement of phosphorus bio-sorption capacity, pre-treatment and modification of the bio-surfaces is required. Therefore, an inexpensive and with limited environmental impact for biomass pre-treatment agent is desirable (Markou et al., 2016).
Column experiments provide data which can be applied for industrial purposes. It is used to itemize the factors which are vital to aid design industrial scale fixed bed adsorption column (Yagub et al., 2015) However, the use of dead biomass in powdered form has some problems, such as difficulty in the separation of biomass after bio-sorption, mass loss after regeneration and low strength and small particle size, which make it difficult to use in column applications. To solve these problems, dead biomass can be immobilized in a bio- polymeric or polymeric matrix used as a supporting material (Odysseas, 2016). So a good support material used for immobilization should be rigid and chemically inert which is why Poly Vinyl alcohol was used.
1.4 Aim and Objectives of the Study
The aim of this work is to use Maize tassel immobilized in poly vinyl alcohol matrix to form beads (PVA beads) to remove phosphoric compounds from surface water. The aim can be achieved through the following objectives;
Preparation and production of maize tassel immobilized in polyvinyl alcohol to form matrix beads.
Characterization of the bio-sorbent using FT-IR, SEM-EDX and BET was
carried out on maize tassel-PVA beads before and after adsorption.
Collection and characterization of the surface water from fish pond.
Evaluation of the following adsorption parameters; flow rate, bed height and initial concentration of the influent.
Evaluation of the column efficiency using empirical models which are the
kinetic isotherms using Clark and Thomas.
1.5 Scope of the Study
The scope of this work includes the preparation of maize tassel immobilized in poly vinyl alcohol matrix to form beads and effluent was collected from a fish pond to know the concentration of phosphoric compounds present. The adsorption process was evaluated using column sorption process and the efficiency was evaluated using Clark and Thomas empirical models.
This material content is developed to serve as a GUIDE for students to conduct academic research
THE REMOVAL OF PHOSPHORIC COMPOUNDS FROM SURFACE WATER NEAR A FARMLAND USING MAIZE TASSEL IMMOBILIZED IN POLYVINYL ALCOHOL
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