Equilibrium Isotherms of Formaldehyde Elimination from the Aqueous Solutions Containing Natural Adsorbents of Rice Bran and the Resulting Ashes

In this pioneering work, the comparisons conducted on the elimination efficiency of formaldehyde by rice bran and the resulting ashes utilized in the adsorption process. In this study the optimal hydraulic retention time, temperature, pH value and adsorbents dosage for the elimination of formaldehyde using three adsorbents including rice bran, ashes of rice bran produced in 300°C (Carbon-300) and in 500°C (Carbon-500) were determined. The method of one factor at the time was used to optimize the above mentioned factors. The best adsorption conditions for 1000 mg/L of formaldehyde and 1 g of adsorbent in acidic environment (pH = 4) is reported at 80°C (with elimination percentage of 70%w/w for rice bran, 83%w/w for carbon-300 and 90%w/w for carbon-500). Also it was revealed that the adsorption of formaldehyde by rice bran adsorbent and Carbon-300 is a function of Langmuir adsorption isotherm while the resulting carbon in 500°C is a function of Freundlich adsorption isotherm. In all experiments, the rice bran ashes showed much greater capacity for formaldehyde removal than one for rice bran. Rice bran is an ideal option in terms availability and the resulting waste could be eliminated through incineration