Abstract

DORIA HERRERA, Gloria María; VALENCIA URIBE, Gloria Cristina; HORMAZA ANAGUANO, Angelina  and  GALLEGO SUAREZ, Darío. Preliminary study of modified rice husk and its effect on the adsorption of Cr(VI) in solution. Rev. P+L [online]. 2016, vol.11, n.1, pp.103-116. ISSN 1909-0455.

Introduction. There are several studies that affirm that rice husk has a good adsorption capacity in an aqueous solution for removing Cr(VI). On the other hand, the Fenton reagent leads to the formation of hydroxyl radicals, considered as highly oxidant species, and this has brought their wide application in water treatments. Concerning the rice husk, a waste from agricultural industries, it is regarded as an environmental problem given its accumulation, but this waste contains a lot of lignin, cellulose, hemicellulose and silicon oxides and, therefore, it is an efficient natural adsorbent to remove heavy metals. The chemical modification of these materials´ surfaces increases the adsorption capacity of metals in solutions. Objective. Determine the conditions for the modification reaction of rice husk with the Fenton reagent and establish the effect on the removal of Cr(VI) in aqueous solution before and after the modification. Materials and methods. The effect of variables such as initial pH, [Fe⁺²]/[H₂O₂] ratio and time of the reactants were analyzed in order to establish the best conditions for the modification. Then, a 2^k factorial analysis was performed with the initial metal concentration (C), acidity of the medium (pH) and adsorbent´s dosage (D) variables, in order to establish the changes in terms of removal percentages. Results. It was demonstrated that with a lower dose of the contaminant (0.7 ppm), the removal percentages reached 90% in both the modified and the native husks. Conclusions. This research work demonstrated the structural modification of rice husk and the Fenton reagent and also demonstrated that, as the Cr(VI) is increased, the removal percentage is lower. Therefore, the Cr(VI) concentration is a significant variable in the metals´ removal in a solution and, the other way around, the dose of the adsorbent in the ratio used is not a significant variable in the model obtained.

Keywords : rice husk; spectrophotometry; UV-Visible; Fenton; structural modification.

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