Tratamento da fibra da casca de coco verde avaliando a concentração de H2O2 e a exposição do sistema reacional à radiação solar

Abstract

Green coconut shell is bulky waste that hasn´t many exploitation technologies to add high value to reuse that. This reuse may be the exploitation of the fiber as metal adsorbent or as a lipase immobilizer for industrial application. The purpose of this work was to avaluate the effect of H2O2 concentration and the exposure of the reaction system to solar radiation on the treated fiber. For that, oxidation reactions were conducted at controlled temperature at 50 °C and with agitation, following the proportions indicated in the reference methodology (2.0 g of coconut fiber for each 40 mL of solution). The concentration of the H2O2 solution used were 4.5%; 7.5%; 10.5%; 13.5% and 16.5%; pH ajusted to 11.5. Subsequently, the effect of solar radiation (UV) in the reaction system with concentration of 4.5% of H2O2 was evaluated. Lignin, holocellulose and hemicellulose were quantified; hemicellulose, together with α-cellulose, is quantitated indirectly by the addition of 17% NaOH (w/v) to a holocellulose mass. Ashes and extractives were also quantified in the fiber after the reference treatment and after the treatment using a solution of 4.5% H2O2 with pH 11.5. The amount of lignin was 11.5% in the fiber treated with the reference method, while an 8.4% content in the treated fiber was determined with 4.5% H2O2 solution at pH 11.5. The analysis of thermogravimetry showed that the T onset of the analysis, at the temperature related to the degradation temperature of the lignin, showed that the loss of mass was lower, being 71.04% for the reference treated fiber, 62.65% for the fiber treated with H2O2 solution with a pH adjusted at 11.5 and a mean of 61.2% for fibers treated with ultraviolet radiation. With the analysis of colorimetry, it was observed a better bleaching of the fiber through the oxidation processes with exposure of the reaction system to the solar radiation in comparison to the other systems. It was further noted that the proposed modifications resulted in improved thermal stability compared to the reference method. From the results obtained, it is concluded that there is a potential for the use of the treatment of green coconut shell fiber with 4.5% at pH 11.5. However, the use of solar energy caused some variations in the chemical compositions of the treated fiber, making the process not so advantageous.