Carbonization of Rice Hull and Chemical Activation of Rice Hull Charcoal by Phosphoric Acid for the Production of Powdered Activated Carbon

Author : Casa, Edmar Pedregosa
Major Adviser : Capareda, Sergio C.
Committee Members : Movillon, Jovita A.; Acda, Reynaldo I.
Year : 1993
Month : April
Type : Thesis
Degree: BS
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Rice hull was carbonized in a muffle furnace at different temperature ranging from 300 to 900 °C. The charcoal yield was calculated as the weight of charcoal recovered per weight of the raw rice hull used. The charcoal recovered was evaluated in terms of their charcoal yield and quality. The charcoal with high yield and considerably good quality was activated using different concentration of phosphoric acid at 400 °C and at room temperature. The adsorptive capacity of the powdered activated carbon was tested by iodine adsorption method. The ash content, moisture content, bulk density and biomass isotherm was developed and the overall carbon recovery throughout the process was calculated.

An equation fir predicting yield at a given temperature (X) was derived by regression analysis. The equation obtained was Y = 39.0925 exp (44977.1913/X²) with a coefficient of regression, r equal to 0.9812.

An inverse relation was observed between the charcoal yield and the temperature. A the carbonization temperature increases, the charcoal yield decreases. The rice hull carbonized at 300 °C gave the highest charcoal yield of 64.01 % while those carbonized at 900 °C was the lowest at 41.60 %. The rice hull carbonized at 400 °C was chosen for activation. The charcoal activated at 400 °C by 5M H₃PO₄ gave the highest iodine number of 300.36 mg/g with corresponding BIN of 494.89 mg/g while those activated at room temperature by the same concentration has low iodine number of 195.467 mg/g. The ash content of the activated carbon produced is considerably lower than the unactivated charcoal id 0.681 g/ml. On the other hand, the moisture content of activated carbon as 3.75 % and the unactivated carbon had 5.45 moisture content. The overall carbon recovery from the carbonization up to the production of activated carbon was 48.39 %.

An equation for the iodine adsorption isotherm curve is X/M = 2.4665 Cr¹/¹·¹¹³⁹² with a regression coefficient of 0.94917.

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