Tratamientos combinados mediante carbón activado y ozono para reducir la presencia de atrazina, simazina, carbamazepina y diclofenaco en medio acuoso

Abstract

In this study, the reduction of the emerging organic contaminants atrazine, simazine, carbamazepine and diclofenac in water was investigated by adsorption, oxidation and a combination of both treatments in phases. Adsorption tests were performed using AST M D3860–98 with two types of activated carbon: powdered activated carbon and granular activated carbon. For the oxidation tests, ozone oxidation process wasperformed. Finally, in the combined tests, the adsorption treatment was applied first followed by oxidation and then that order was reversed. Contaminant's reduction percentagewas studied for each treatment at different contact times. The tests were carried out at three different initial concentrations of each contaminant and the variation of the carbon and ozone dose was studied. The results obtained at the lowest initial concentration for each contaminant, 0.7 mg L-1 , showed that, first in adsorption tests with powdered activated carbon, for a dose of 16 mg L -1 , and contact times of 1, 24 and 48 hours, percentage reductions were obtained for the contaminant atrazine of 81, 92 and 94%, for simazine of 64, 80 and 87%, carbamazepine of 53, 95 and 99% and diclofenac of 92, 98 and 99% respectively.In adsorption tests with granular activated carbon, maintaining the same concentration of contaminant and dose of activated carbon, the percentage of reduction of all contaminants in the first hour was less than 10%, but the percentage increased to 25 and 34% for atrazine after 24 and 48 hours of contact time, for the rest of the contaminants it was 21 and 32% for simazine, 24 and 37% for carbamazepine and 27 and 40% in the study with diclofenac, respectively. During ozone oxidation tests, maintaining the same initial contaminant concentration, when ozone was applied at a dose of 19. 7 mg L-1 for the pesticides and 0.224 mg L-1 for the drugs, and with a reaction time of 4 minutes, a reduction of atrazine by 93%, simazine by 82%, carbamazepine by 98% and diclofenac by 78% was obtained, but oxidation by-products were produced XVI Finally, in the combined tests, with the same initial contaminant concentration and the same doses of activated carbon and ozone as above, when the combined treatment started with powdered activated carbon followed by ozone, the contact time required to achieve a reduction of more than 90% was less than 1 hour for all the contaminants studied. Whereas, when the treatment started with granular activated carbon the contact time was 3 days. When the order of treatment was reversed, starting with ozone and following by powdered activated carbon, the same occurred as in the combined treatments of powdered activated carbon followed by ozone, which required contact times of less than 1 hour to achieve reductions of more than 90% for all the contaminants studied. On the other hand, when the activated carbon was granular, the required contact time increased to 4 days for all the contaminants studied. Therefore, better reductions against time were obtained for emerging organic contaminants studied when the combined treatment was performed with powdered activated carbon than with granular activated carbon. The combined treatment that starts with ozone and ends with powdered activated carbon is more favourable because, in addition to reducing the main contaminant, it would also reduce the by-products generated during oxidation.