Tratamento de efluente do biodiesel de algodão utilizando adsorvente natural (crescentia cujete l.) em comparação com sintéticos.

Abstract

Biodiesel is a renewable fuel developed as an alternative to fossil diesel. The combustion of biodiesel significantly reduces greenhouse gas emissions, but its production process uses mainly water purification, generating wastewater with pollution levels above the permitted standards. In this sense the objective of this study was to characterize the effluent of the cotton biodiesel purification, treat it with natural adsorbent obtained from the bark of cuité (Crescentia cujete L.) and synthetic adsorbents (activated carbon and silica gel) in order to adapt the effluent to reuse or disposal. The physico-chemical characteristics of biodiesel analyzed the wash water were hydrogenionic potential, turbidity, total solids, chemical oxygen demand and content of oils and greases, which were outside the CONAMA resolution limits No. 430/2011 establishing the release quality standards of effluent into receiving bodies. Further physico-chemical evaluation to the passage of washing water by the three adsorbents was carried out and they showed similar efficiency, but the shell of cuité showed better results, within the standards with average values of pH 6.3; turbidity 48,7UNT; Total solids 3.1 mg / L, 97.4% reduction of COD initially and characterized content of oils and greases in 2.5 mg / L. The adsorbents were characterized by X-ray diffraction, absorption spectroscopy in the infrared region and BET, and Thermogravimetry, Proximate Composition and zero charge point for natural adsorbent. Infrared spectra of the mixture of the washing waters after treatment indicated that there removing alcohols and esters present in the catalyst effluent. Despite the bark of cuité present low surface area showed excellent results in preliminary tests for use as an adsorbent, justified by the presence of adsorptive sites. The composition of the peel cuité indicated high content of carbohydrates, especially cellulose, hemicellulose and lignin as well as proteins which possess adsorptive sites, such as carbonyl groups, carboxyl groups, amines, and hydroxyls, which facilitates the adsorption process on the material surface . The point of zero charge of cuité shell was 6.91, and it was found that there was a greater affinity for basic groups, due to a higher concentration of active sites present on the surface of the adsorbent acids. The physical and chemical parameters of cotton biodiesel washings were in non-compliance with environmental legislation, preventing the same discharge into water bodies or their reuse in industry. The adsorbent of cuité bark left the effluent from biodiesel within the standards, with the possibility of reuse in own purification process, and present similar efficiency to synthetic adsorbents indicating potential to be economically viable, in the case of a natural, renewable material and low cost.