Espectroscopia UV-VIS aplicada na determinação do tempo de degradação de solução de Abelmoschus esculentus (L.) Moench utilizada como floculante natural

Abstract

The water collected in rivers and springs contains great diversity of microorganisms, particulate matter and dissolved. The treatment of this water is performed in water treatment plants (WTP). The coagulation and flocculation are two of the steps of the water treatment process in which chemical coagulants are used based on iron salts or aluminum, however, the most used are the aluminum base. To replace the aluminum or decrease the concentration of this metal used, many natural alternatives to aid in the coagulation / flocculation process are being assessed, using okra (Abelmoschus esculentus (L.) Moench) of these alternatives. For the preparation of the concentrated and dilute solution of okra used in this work, the fruits were dried in an oven at 60 ° C for 48 hours, and then ground. To determine the degradation time of okra solution, i.e., its lifetime, spectral measurements were performed in both prepared solutions. To each sample was collected into a spectrum in the UV-Vis region. These spectra were arranged in the shape of an X matrix that was applied chemometric method MCR-ALS solution to evaluate the degradation time. It was using Matlab R2007b software and PLS-Toolbox 5.2 Tools. It was then made characterization of the crude water to be used in testing in respect of color parameters, turbidity, pH, TOC (total organic carbon) which is calculated from the values of the UV254 and MOD (dissolved organic matter) from the values the UV272. Assays were performed in Jar Test, in duplicate for 7 days using aluminum polychloride (PAC) and coagulant solution and diluted okra as flocculating aid, plus the addition of alkalizing. Then it was performed to characterize the treated water to the same parameters. Through spectral measurements and tests in the Jar Test was established that the Okra solution is stable only until the time of 24 hours, and after this time, begins the process of degradation of Okra constituents that promote flocculation. Satisfactory results were obtained after treatment with the combination of water PAC coagulant solution and Okra as flocculating aid. The color and turbidity were the parameters that showed the best results for removal of water, between 91% and 96%. The pH showed variation between 53% before treatment and 71% after treatment. The TOC showed a percentage of removal, between 76% and 77%, and a removal MOD between 92% and 93.5%. From these results, it is noted that it is possible used in conjunction okra as flocculating aid, resulting in a reduction of health problems, mainly involving the use of large amounts of coagulating the aluminum base.