The Effect Of Particle Size On The Extraction Of Oil From Groundnut

Project and Seminar Material for Chemical Engineering

The Effect Of Particle Size On The Extraction Of Oil From Groundnut


The aim of this research project was to determine the effect of particle size on the extraction of oil from groundnut.

The successful extraction of the project require the following steps

  1. Collection of the seeds
  2. Preparation of the seeds
  3. Particle size reduction
  4. Extraction process etc.

The groundnut seed for this project research was purchased from a local market in Enugu Metropolis. Also, the method used in this project research is solvent extraction method. The solvent used in the exraction is n-hexane, this n –hexane was used because of its hight yield of oil recovery after extraction. The extraction was carried was carried out using 280g of size reduced groundnut with 600ml of n-hexane. Different particle sizes were used in this experiment using sizes screens of 10mm, 20mm, 40mm, 60mm, and 80mm respectively.

The yield with hexane as solvent used in 10mm, 20mm, 40mm, 60mm and 80 mm are 41.3% 25%, 33.93%, 44% and 55.5% respectively. From this experiment, it now shows that the smaller the particle size, the greater the yield of oil recovered. And from experiment the smallest particle size is 80mm and is gives the highest yield of oil of about 55.5%. in conclusion, the particle size plays important role in leaching operation. Because they either increase the rate of leaching or reduce the rate of leaching. Particle size increase the rate of leaching if the groundnut seeds are property crushed. Furthermore, the smaller the size the greater is the interfacial are between the solvent and solid. And this will help to increase the rate of diffusion of oil from the particle.

Definition of Terms / Nomenclature

Solvent Extraction:

Is the separation of the constituents of a liquid solution by contact with another insoluble liquid.


This can be defined as the solution which is to be extracted.


This is the residual liquid from which has been removed.


It is the liquid with which the feed is contacted.


The Solvent rich product of the operation is called the extract


Is a method of separating the components of solution which depends upon the distribution of eh substances between a gas and a liquid phase, applied to case where all components are present in both phases.

Chapter One


Background of the Study

Groundnut is an annual herbaceous plant growing from 30 to 50cm tall. A groundnut seed is composed of two cotyledons, testa, hypocotyls and epicotyl. All except the testa are considered to be part of the embryo.

The cotyledon is the major storage tissue for proteins and 20 to 22% oil.

Groundnut seed undergo epigeal germination in which case the cotyledons or seed leaves are carried above the soil surface. A planted groundnut seed mature after few months.

According to history, groundnuts were domesticated in prehistoric times in peru where the wild ancestors were still found.

Archaeologists have thus far dated the oldest specimen to about 7,600 years before the present Dill Lay and Tom, (2007) now updated it.

The plant was later spread worldwide by European traders. Cultivation in the English colonies of North Americans was popularized by African Americans, who bought the Kikongo word “Goober”. In South American, the groundnut is thought to have first grown in Argentina or Bolivia where the wildest strains grow today.

Groundnut is best planed in February to March is some states usually the rain forest and in many or early June in the Northern States, this variation is as a result of the difference in climate condition equipments.

The climate requirement for the groundnut is about the same as that for after the plant is well established. In general combination of high temperature and low precipitation are unfavorable, groundnut seed produced under high temperature condition tend to be low in oil and oil quality.

Botanical name of groundnut is “Arachis hypogaea”. Hypogea means in botanical world, “Under the earth”. Groundnut is also known by other name though local such as peanuts, and pignuts,

The stalk at the base of the ovary called the pedicel, elongates rapidly and turns downward to burry the fruits several inches in the ground where they complete their development. The entire plants including roots, is removed from the soil during harvesting.

Statement of the Problem

The statement of the problem in the research project of the effects of particle size on extraction of oil from groundnut, in addition to this, different sample size should be used when carrying out the practical aspect of it in order to know the effect in particle size.

In any process which involves reaction of solvent and solutes processing parameters which affects the optimum yield of the products and if these parameters are not known, checked, controlled or regulated the product end point night result into low product quality and quality or damaged product.

In the process of extraction of oil from groundnut, such parameters should be carefully considered because of the nutritious value of groundnut since any processing parameter neglected may destroy the nutrient content of the groundnut oil.

Purpose / Aims / Objectives of the Study

The purpose of this research project is simply for the acquisition of the knowledge based on the effect of particle size on the extraction of oil from groundnut. The main purpose of study is to find out the effects processing parameters could have, on the yield of oil from groundnut seed and how there parameters could be regulated in order to ascertain high yield of oil from groundnuts seeds.

Scope and Limitation of the Study


The scope of this research project covers all the areas and processes involved during the extraction of oil from groundnut ranging from picking of the groundnut seeds, drying the seed, size reducing the particle, size separation to dissolving the separated particles in a solvent n-hexane and finally separating the mixture through the process of distillation on which the temperature reading was taken.

The study focused on the optimum yield of oil from groundnut seed putting into consideration and care the effect of processing parameters like temperature, particle size, contact time, solvent solute ratio, on the yield of oil. The study also focused on showing the nutritional value of groundnut oil and its various uses and the need to avoid destruction of those nutrients during the oil extractions.

For The Limitation:

In a study of this nature one would like to accumulate data from many areas. But in view of length of time allowed for this research such as wide range sample study was almost externally difficult. We then concentrated this practical work in Enugu metropolis. The reason for choosing Enugu metropolis was because of time factor allowed and upon particle consideration including the fact that we know almost every where and things about Enugu metropolis.

Besides, there were some problems that stemmed up during the research work in which some were stated below.

Financial Constraint:

As a student, there was not enough capital to spend, especially for transport as the practical venue were very far from the school and fact finding and borrowing of necessary literature that would have helped in the writing of this research work, were almost impossible due to the lack of relevant materials in the libraries visited. Also the money was on the high side, hence we encountered problem in getting the money. But all the same all these problems did not prevent us from the continuation of the research work.

Method Research

This is sub-topic that contains all the detailed information on how the project research was conducted. Pieces of information were gathered from research on the internet and consultation way of research, while other were gotten through laboratory, Theoretical, Descriptive and practical way of research. Compose a project write up based on this project topic.

Significance of the Study

The significance of this project research is because of extraction of oil from any vegetable cash crops and contributes to the body of knowledge in the particular area of investigation. Furthermore, extraction of oil from groundnut, when commercialized can bring about the source of development in the community or in the entire country in general. It can also provide oils for food and other uses, employment for the youths and bye products for the industrials and other important productions.

Chapter Five


Table I shows the percentage yield of the groundnut oil at different particles sizes. The highest amount of oil yield was at 1.7um while the least was at 1.18um.

The chart in figure 1 explains the effect of particle size on the extraction of oil from groundnut. The chart shows a decrease in the percentage yield of oil extracted from the groundnut sample as the particle sizes increased from 0.43 to 1.7um.

The phenomenon was as a result of surface area of the particles. The groundnut oil tends to be more loosely bound at smaller particle size and thus is much easier to extract then those with relatively larger particle size and thus is much easier to extract then those with relatively of small particles on each other which is a result of plugging that the process is not just particle size dependent. The equation for the particle size dependent. The equation for the particle size relationship with the percentage oil produced was gotten to be y=9.03x+41.85. where y is the % yield of the oil and x is the particle size in Nm.

The equation can be used to predict the amount of oil that can be extracted from groundnut oil once the particle size are known.

Water content or moisture content is the quantity of water contained in a material (Wikipedia 2010). The moisture content is an indication of the hydrophobicity of the material. The moisture content is related to the oil content of the matierla the higher the moisture content the lower the extractible oils in the material. The moisture content of the groundnut sample was 2.2%.

The specific gravity SG shows the weight of the oil relative to weight of water. This is also related also to the viscosity of the oil. The less heavy natural plant inessential oils are more fluid than the relatively heavier ones and thus les vicious. The relative density of the groundnut oil was 0.93.

The acid value is the mass of potassium hydroxide (KOH) in milligrams that is required to neutralize one gram of the oil. The acid number is a measures of the amount of carboxylic acid groups in the oil, such as fatty acids. An increased acid oxidize or rancidity fast (Hussein et al, 20011).

The Acid value of groundnut oil is 0.5meq. FFA is a source of flavors and aromas. FFA are responsible for how oils behave in other solvents and volatile with characteristic smell (Kardash et al, 2005) and how they are prone to oxidation in their free form and their breakdown products (aldehydes, Ketones, alcohols, and organic acids) provide characteristic flavors and aromas (cao et al 2008). The value of FFA in groundnut was 2.82%. saponification value represents the number of milligrams of potassium hydroxide required to saponify 1g of fact under the specific conditions. The saponification value of the groundnut oil was 220.2. it is a measure of the average molecular weight (or chain length) of all the fatty acids present.

As most of the mass of fat trimester is in the 3 fatty acids, if allows for comparison of the average fatty acid chain length.

The results of the physics chemical analysis of the groundnut oil are an indication that the oil is of good quality, indication that the method is feasible and repeatable.

The effect of particle size shows that oil extraction is more effective with relatively small particle size.

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