Production of activated carbon from date palm pits and its use in industrial wastewater treatment

Essa, Mohammed Hussein (2008). Production of activated carbon from date palm pits and its use in industrial wastewater treatment. PhD thesis The Open University.



The present study investigates, for the first time, the production of granular activated carbon (GAC) from date palm pits, a waste material. Reported data indicates.that the t. yearly production of dates in the Kingdom of Saudi Arabia (KSA) is more than 800 ktonnes of which a significant portion is de-stoned prior to sale. Hence the use of date palm pits for the production of GAC would confer two benefits, Le., reduction in waste disposal costs and concerns and production of a very useful material from this waste, Le., GAC, which at the present is imported in the KSA for several industrial applications.
Considering these facts, date palm pits from a local source were used for the production of GAC. Several GAC production variables were investigated in detail, to study their effect on the BET specific surface area (SSABET), porosity, and the pore size distribution of the produced material. Variables studied included sample predrying, time of carbonization, time of activation, strength of the activating agent (i.e., phosphoric acid), acid impregnation ratio, pH, and temperature. Nitrogen adsorption isotherm data was used for the determination of respective SSABET, and porosity values.
The optimum conditions that produced the best activated carbon were, H3P04 concentration equal to 70%, acid to pits ratio of 1.6:1, and carbonization temperature of 500°C. Additionally, a maximum yield of 24% was noted for the best GAC sample which showed the following characteristics 590 kg m-3 bulk density, 0.5% ash content, 1100 mg g-1 iodine number, and 1319 m2 g-1 SSABET. Furthermore, this GAC sample showed substantial capability to adsorb phenol and 2-Methylphenol (o-cresol) from the aqueous phase. The respective adsorption data fitted well to the Freundlich adsorption isotherm. Several continuous column studies (using operational variables including flowrate, initial pollutant concentration, pH, temperature and dissolved oxygen) were also conducted to find the suitability of the produced optimum GAC sample for the removal of phenol and 2-Methylphenol from the aqueous phase. For example, the adsorption of both phenol and 2-Methylphenol was influenced both by the flowrate and the initial pollutant concentration. Also, the breakthrough time decreased when the flowrate and the initial concentration values were increased, probably due to insufficient pollutant residence time. The respective optimum activated carbon was also successfully used for the reduction of total organic carbon from an industrial wastewater sample.
Furthermore, to minimize waste disposal cost and concerns related to the exhausted GAC, an attempt was also made to regenerate the used GAC sample from the present work using chemical and electrochemical desorption methodologies. The electrochemical desorption method, which so far has been scantly investigated in the literature, was noted to successfully regenerate the used GAC sample, using a current density value of 50 rnA cm-2. Factorial experimental design and optimization of parameters for the production of GAC from date pits, using Response Surface Methodology (RSM), was also completed. The respective results were acid to pits ratio of 1.5:1, carbonization temperature of430°C, and H3P04 concentration of 55%.
In summary, a high efficiency GAC sample was successfully produced from an otherwise waste material i.e., the palm date pits. The produced GAC was also noted to be very efficient for the removal of organic pollutants from the aqueous phase. It is suggested that the use of activated carbon produced from date pits would be economical, since date pits are a waste product and available in large quantity in the Kingdom of Saudi Arabia, and phosphoric acid is manufactured from local resources in the Kingdom.

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