Tratamento de água produzida utilizando microemulsão formulada a partir de tensoativos de origem vegetal

Abstract

Produced water (PW) is an effluent from oil extraction. Along with the growth of this exploration, there is an increase in the environmental concern of the responsible bodies, especially in relation to the quality of wastewater discarded from this type of activity, which brings two major problems: its composition, as it has a high of oils and greases content (OGC) and salinity, and its significant volume. Such characteristics make its final disposal difficult, making it necessary to properly manage the PW, that is, apply actions such as characterization, treatment, disposal or reinjection. This study proposes a treatment of produced water using microemulsions (ME) with surfactants of vegetable origin, with the aim of reducing two main factors, OGC and salinity. The decision to use a vegetable oil-based surfactant as an alternative to a petroleum-based surfactant was made to reduce the negative effects of the overall process on the environment. Coconut soap, the surfactant (S) used in the formulated ME, was selected after testing a variety of surfactants of plant origin. The other components used in the ME formulation were 2-butanol, as cosurfactant (C), hexane as the oil phase and saline water with 2% NaCl, as the aqueous phase. The ME point used in water treatment was defined by planning the D-optimal mixture, composed of 85% C/S, 2.5% oil phase and 12.5% water phase, with a C/S ratio of 4. In addition Furthermore, a full factorial experimental design was used with combinations of three variables (time, temperature and percentage of microemulsion) and repetition of the central point to select the greatest reduction in OGC and salinity and the best conditions were applied to the real produced water. According to the results, the OGC reduction values ranged from 90.97 to 97.78%, the actual values ranged from 14.33 to 3.52 mg.L-1. These values are within the limits established by environmental agencies, CONAMA, US EPA and OSPAR Commission, for the disposal of water produced at sea. Furthermore, the salinity reduction ranged from 44.37 to 52.17%, the actual values ranged from 31660.35 to 27221.19 mg.L-1. The reduction in salinity of the synthetic water produced treated with microemulsion in this work showed better results when compared to the literature that used ME with a non-biodegradable petroleum-based surfactant in its composition. As for real produced water (RPW), the reduction in TOG was very significant, going from 138.95 mg.L-1 to 12.54 mg.L-1 on average, reaching a reduction of 90.98%. The APR salinity reduction was also quite significant, going from 49376.47 to 25905.88 mg.L-1, thus obtaining a salinity reduction of 47.53%. Therefore, it can be said that the use of a surfactant of plant origin and biodegradable in the formulation of the microemulsion for the treatment of produced water is as effective in reducing TOG and salinity as petroleum-based surfactants, which are more harmful to the environment.