Journal of Applied Sciences & Environmental Management, Vol. 9, No. 1, 2005, pp.65-68

A Preliminary Evaluation of Otamiri River Sands for the Production of Plain Glass

* USHIE, FA; **ESU, EO; *UDOM, GJ.

* Department of Geology, University of Port Harcourt,    P. M. B. 5323, Port Harcourt, Nigeria.
**Department of Geology, University of Calabar, Calabar, Nigeria. Email goddyudom@yahoo.com

Code Number: ja05011

ABSTRACT: Grain-size distribution and chemical analyses were carried out on four sand samples randomly taken from the bank of Otamiri River around Chokocho and Umuanyaga, Etche Local Government Area, Rivers State. This was done to assess the purity and suitability of the sands for the making of plain glass. Results of grain-size analysis show that 86% of the sand particles fall between 0.125mm and 1.2mm, which is within the ideal sand fraction range used for glass making.  Chemical analysis shows the sand to contain more than 99% silica (SiO₂), very low content of iron (0.0017 to 0.0039ppm), chromium (0.000022 to 0.000032ppm), titanium (0.049 to 0.066ppm) and calcium (0.000001 to 0.000003ppm). Others include Aluminium (0.00126 to0.0103ppm), potassium (0.0002 to 0.0042ppm), Magnesium (0.0001 to 0.0002ppm), and Sodium (0.005 to 0.038ppm). The concentration levels of these elements in the samples conform with internationally acceptable standards for glass production. @ JASEM

The most important constituent of glass is silica (SiO₂). Glass sand contains between 95-98% silica (Hutchin and Harrington, 1966; Sempolinski and Schermerhorn 1997) Other constituents are impurities in various concentrations (Hrdina, 1999) which are useful in determining the kind and colour of glass to be made. On the other hand, in the production of ultra-low expansion (ULE) glass, impurities are rather minimised by injecting high purity precursors into flames which then react to form TiO₂ and SiO₂ which deposit into the surface of the growing glass (Hrdina, 1999).

To obtain a homogeneous melt the grains of silica sand should be of even size between 0.12 – 2.00mm (Glass Production Guide, 1966). This paper seeks to evaluate the sands using the data arising from grain-size and chemical analyses in order to determine their suitability for glass making. The grain-size analysis helps to determine the grading of the sands; because for a homogeneous intersolution to be produced, the sand must be even in size and this is known as the “ideal fraction”. The chemical analysis on the other hand helps to determine the purity, hence the type and colour of the glass to be produced.

Physical/Geological Setting Of The Study Area:

The study area is in Etche Local Government Area of Rivers State, Nigeria. It lies between longitude 6⁰45' and 7⁰18'E and latitude 4⁰45' and 5⁰15'N (Fig. 1). The study area is within the subequatorial region which is characterized by two major seasons namely, the rainy season and the dry season (Iloeje, 1972). The rainy season starts in March and ends in October, with a peak in June and July, while the dry season begins in November and lasts till March. Annual total rainfall is over 200cm, relative humidity is above 80% and the mean temperature value is 28.14°C in parts of the state (Udom et al 1999).

Otamiri River takes its rise at Egbu in Owerri area and flows southwards through Owerri town to join the Imo River in Etche LGA, Rivers State. It receives tributaries along its course and drains a considerably large area. By this action, the Coastal Plain Sands (Benin Formation) are constantly washed as the river flows southwards.

Etche LGA lies within the Benin Formation of Oligocene to Miocene age, which is part of the stratigraphic column of the Niger Delta Sedimentary Basin. This Formation overlies the Agbada Formation consisting of sands with shale intercalations, and is prominent as the major petroleum reservoir in the Niger Delta sub-region. Underlying the Agbada Formation is the Akata Formation, mainly shaly, which is the major source rock for petroleum in the Delta (Short and Stauble, 1967).

Basically, the Benin Formation consists of over 90% sands and sandstones, which are gravelly in places with a maximum thickness of 2130metres (Schield, 1798). There are shale intercalations within these sands/sandstones at some levels. The sands are fine-to-coarse-grained in size, granular in texture and hardly consolidated. The sediments represent upper deltaic plain deposits; the sands may represent braided streams, point bars and channel-fills, whereas the thin shale intercalations may represent back-swamp deposits. In the subsurface it is Oligocene in age, becoming progressively younger southwards (Kogbe, 1976).

Data Acquisition

Four sand samples were collected from the Otamiri River around Chokocho and Umuanyaga communities in Etche L.G.A. (Fig. 1). A grab was used to collect the samples from the river banks and exposed river sections. The samples were then subjected to two methods of analysis to generate the needed data.

(a)                Grain-Size Analysis

Grain-size analysis was undertaken to determine the ideal fraction of the sands. This was done, first by sieving the samples through standard set of sieves.

The results are shown in Table 1.

Thereafter, the results were plotted on conventional graph papers to identify the ideal fraction and uniformity coefficient (Cu) of the sands. Cu is given by the formula.

Where D_60­ = diameter of the 60th quartile and

  D­₁₀ = diameter of the 10th quartile

  A typical grain-size distribution plot (representing sample location 4) is presented in Fig 2.

(b)                 Chemical Analysis

500mg of the sample was ground, prepared and left for 16 hours with ocassional agitation. After 16 hours the solution was heated in a water bath until it was clear. Two grammes (2g) of boric acid was added to prevent the precipitation of Ca and Mg fluorides. The solution permits the determination of silicon, titanium, alumunium, iron, calcium, magnesium, sodium and chronium using the Atomic Absorption Spectrophotometric (AAS) method. For this study the Buck/Scientific AAS 200A was used.

The prepared aqueous solution of the sample was analysed for elemental constituents by choosing the wavelengths of the elements and determining the response of the elements when compared with the concentration of the standard solution. The standard control value of each element is shown in Table 2. The results of the elemental constituents of the samples are shown in Table 3.

DISCUSSION AND CONCLUSION

The results of grain size analysis (Table 1) and the resulting distribution curves for the sands show the coefficient of uniformity in the range of 2.80 to 2.98. It is obvious from these values that all the samples exhibit a high degree of uniformity. Also about 86% of the sand fall within the ideal fraction (0.125-2mm). This is suitable for glass making (Glass Production Guide, 1966).               

Chemically, the sand that can be used for glass manufacture must have a minimum of 95-98% silica. It is clear from the results of the chemical analysis (Table 3) that this important chemical requirement is met. The high percentage of silica in the sand transfers qualities like high electrical resistance and high softening temperatures to the glass. The results of this analysis show the presence of Iron, Chromium and Titanium with mean values of 0.0026ppm, 0.000026ppm, and 0.060ppm respectively. These elements are capable of producing different colours in glass. However, their concentration levels in the samples show that the manufacture of colourless glass is possible. If necessary, decolourizers can be used. On the other hand, if coloured glasses are needed, colouring agents can be added. These agents include metallic gold, which gives a gold-ruby glass; selenium which gives a red glass; chronium and copper which produce green glass etc. Silica in its pure form is relatively transparent over a wide range of wavelengths.

In conclusion, particle size distribution test and chemical analysis on Otamiri River sands, show that the sands have met the international standards stipulated for glass making by the Society of Glass Technology. With these preliminary results it is now important to estimate the amount of sand that can be safely quarried from the study area. This step calls for a detailed full-scale work involving a larger number of samples, higher density of sampling and lateral as well as the vertical variation (if any) in the sample quantity.

Acknowledgement: The authors acknowledge with thanks the assistance rendered by the laboratory staff of West African Glass Industry, Tran-Amadi Industrial Layout, Port Harcourt.

REFERENCES

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