ASSESSMENT OF TWO LOCAL PLANT DYES AS COLOURANTS FOR PETROLEUM PRODUCTS (PETROL KEROSENE AND DIESEL)

ABSTRACT

Dyes from Pterocarpus osun Craib and Lawsonia inermis Linn. were extracted using ethanol and methanol respectively. The extracted dyes were subsequently purified using chromatographic methods. Purified pigments were characterized using Ultra-Violet Visible Spectrophotometer, Fourtier Transform Infrared Spectrophotometer and Lovibond Tintometer. The UV spectra of the dyes in petrol,  kerosene  and  diesel  showed  presence  of  chromophores.  The  FTIR spectra of the dyes showed presence of phenolic O-H stretching and C=C of aromatic functional groups. The dye from Lawsonia inermis Linn. was remarkably stable in colouring petrol for a period of twenty-eight days  but not in kerosene and diesel while the dye from Pterocarpus osun Craib was not stable.  Thus,  dye  from  Lawsonia  inermis  Linn.  can  be  used  as  alternative source of colourant  for petrol while the dye  can not be used  for the same purpose  for  kerosene  and  diesel  due  to  their  instability.  The  dye  from Pterocarpus osun  Craib cannot be used because of their instability. They are not remarkably active in colouring any of the petroleum products (petrol, kerosene and diesel).

CHAPTER ONE

1.0     Introduction

1.1     Dyestuffs

Today, in the world of growing environmental consciousness, natural colourants have attracted the attention of everyone1,2. The alarming rate of high use of synthetic dyes which causes carcinogenicity, mutagenicity, green house effect and are very expensive have provided an urgent approach to the use of natural plant dyes in the petroleum industry3,4.    Natural plant dyes have been discovered accidentally and their uses have become so much a part of man’s customs that it is difficult to imagine modern world without dyes. The art of dyeing spread widely as civilization advanced5.

A dye is an organic compound composed of chromophore (the coloured

portion   of   the   dye   molecule)   and   auxochrome   (which   slightly   alters   the colour) .The auxochrome makes the dyes soluble and is a site for bonding material. Dyes are molecules that can be dissolved in water or some other carrier so that they will penetrate the material6.

For a dye to be usable in colouring materials, it must be highly coloured;

must yield goods that are “colour fast”, or resistant to colour change or loss during use and care; and must be soluble or capable of being made soluble in water or other medium in which they are applied, or they must themselves be molecularly dispersible into the material7.

The archaeological evidences have shown that dyeing has been extensively carried out for over 5000 years, particularly in India and Phoenicia8,9. The dyes were obtained from animal, vegetable or mineral origin, with no or very little processing. They include cochineal obtained from dried cochineal insect, brazil- wood from caesalphia plant, madder from the roots of Rubia tinctoria, Tyrian purple  from  purple  snail  (Murex  bandaris),  and  indigo  from  the  leaves  of Indigofera tinctoria and many more. The plant parts that were used are roots, bark, leaves  and  wood10,11.  Colourant  improve  the  appearance,  culinary  effect  and

promote acceptability of substrates12.

The colour index categorizes all colouring matters according to their application and characteristics. Dyes can also be classified according to their chemical structure, shade, fastness, etc13.

With advances in science and technology, dyes synthetically produced from

coal tar and petroleum sources, and natural dyes have almost been replaced by synthetic dyes. The most significant discovery in synthetic dyes occurred in the

19th  century when the first man-made dye was synthesized by a Chemist, William

Henry Perkin14. He produced the first basic azine dye known as mauveine [1] (Mauve). The production of this dye opened door for the synthesis of many classes of dyes including the first azo dye, Congo Red [2].
Dyes are used to colour petrol, kerosene and diesel in order to improve their appearance, as well as for identification of  grade, type of use or merely as a trademark of the manufacturer15. Solvent dyes used to colour refined petroleum products is to be able to differentiate between petrol,  diesel, kerosene and  jet fuels16. Petroleum dyes help in identification of fuel adulteration. They also help to create differentiation in various petroleum products such as leaded and unleaded, high  and  low octane gasoline,  high  and low sulphur diesel and  aviation fuels attributes17.  Other  reasons  for  dyeing  fuel,  such  as  for  aviation,  supports  the fuelling process itself, to ensure that the right type of fuel is used in the correct aircraft – as the consequences of getting this wrong can be disastrous18. However, solubility as well as hue and fastness are the major determinant factors for dyes used in these petroleum products.

Other uses of dyes include in the colouration of food items, inks, metals, leather,  textiles and  paper.  Other  areas of  use  include  photographic  paper,  as indicator in chemical analysis and biological stain and as point leak detection19. With  the  increasing  demand  in petroleum  industry  and  various  sectors  of  the economy for dyes and pigments coupled  with the  high cost of synthetic  dyes importation, there is need to explore plant dyes and their applications will improve the socio-economy and artistic development of the nation.

Synthetic  dyes  have  been  used  over  the  years  in  the  petroleum  industry  for colouring petroleum products. This helps in check-mating adulteration, identification of grade or quality and for aesthetic purposes in the oil industry.  The cost and toxicity (carcinogenity and mutagenity) of the synthetic dyes have shifted attention for alternative dyes which are cheap and environmental friendly. Dye of Pterocarpus osun  Craib have been used to colour petroleum products (petrol, kerosene and diesel) but their stabilities have not been studied or reported while dye of Lawsonia inermis Linn. have not been used to colour petroleum products.

1.2     Lawsonia inermis Linn. plant

Lawsonia inermis (Henna) plant belongs to the family lythraceae. The plant grows at temperatures higher than 11 oC and needs about 5 years to mature. It has a height of 8-10 feet 20-22. The leaves have been extensively used for centuries in the Middle East, the Far East and Northern Africa as dye for nails, skin, hands, hair and textile23. Henna is also used in treating skin problems, headache, jaundice, amebiasis and enlargement of the spleen. Leaves of Lawsonia inermis provide an

important  cosmetic  dyes  and  so  on  24-25.  The  major pigment  in  henna  leaf  is lawsone [2-hydroxyl-1,4-naphthaquinone (C10H6O3)], having a fast-dyeing property26.  Lawsonia  inermis  has  been  well  investigated  phytochemically  by various researchers. The occurrence of β-sitosterol glucoside, flavonoids, quinoids,

naphthalene derivatives, gallic acid, coumarins, and xanthones in lawsonia leaf has been reported27-32.

1.3     Pterocarpus osun Craib plant

Pterocarpus osun belongs to the family papilionaceae and it occurs throughout the tropics. The Nigerian species are trees of about 30 meters tall, with a girth size of about 2.4 meters with spreading crown and with bright yellow and usually alternate leaflets. It has distinct pinkles on twigs and young branches. The fruits are dark brown and velvety when young, with short soft and often stickly pickles mostly surrounding the centre33,34. The wood of Pterocarpus osun contains

16 % of red colour pigments, which are insoluble in water but soluble in organic

acid and alkali6. Pterocarpus osun are medically useful for superficial skin diseases such as eczema and has also been used as an active ingredient in soap35,36. Other active constituents of Pterocarpus osun are tannins, phenols, saponin and flavonoids37-40.

1.4     Statement of the problems

Synthetic dyes are no longer universally attractive in colouring petroleum products due to the numerous challenges (carcinogenic, mutagenic, toxic, cost and so on) associated with their use. The use of colourants for petroleum products cannot be

avoided because it helps in quick, visual differentiation of petrol, kerosene and diesel. It also helps in identification of grade or quality of petroleum products. Presently,  the  dyes  used  by Nigerian  refineries  are  imported,  coded  and  used without the source of import disclosing the exact chemical names and composition either to the refinery staff or to the public. The chemical nature used of dyes in imported petroleum products are also shrouded in secrecy. These have necessitated the search for local alternative sources of colourants for petroleum products in the oil industry.

1.5     Objectives of the study

This study has the following objectives:

i.         To assess the stability of the heartwood of P. osun and young leaf of L. inermis plant extract respectively, as colourants for petroleum products (petrol, kerosene and diesel).

ii.        To determine alternative sources of colouring petroleum products rather than using synthetic dyes, and

iii.       To determine the stability of the dye colours when added to petroleum products.

1.6     Justification of the study Natural dyes have been widely reported to be non-toxic, environmentally friendly and less expensive. Therefore, the assessment of two local plant dyes (P. osun and L. inermis) as colourants for petroleum products is justified.

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