Abstract

Copolymers beads based on methyl methacrylate (MMA) and divinylbenzene (DVB) were prepared by suspension polymerization technique. For the copolymer synthesis, the following reaction parameters were varied: diluent type, dilution degree and divinylbenzene content. The copolymer porosity and specific surface area (BET) were determined. The copolymers were used to prepare columns, which were tested as oil remover from PETROBRAS produced water. Columns containing only one kind of polymer (polyDVB) achieved a oil content reduction of 84.9%; containing two different polymers (polyDVB and poly(MMA-DVB)) reached 89.1%. The results showed that the distinct chemical composition copolymers can retain different compounds from the produced water. The columns can be re-used after a regeneration process.

Introduction

Petroleum industries have emphasized the offshore production, because a significant content of water is coproduced, during the oil exploration and production. Produced water represents the greater stream of residues in oil production. Normally, a new oil field produces little water (around 5–15 %) and, when the field becomes mature, this water volume can increase significantly to 75–90%. Produced water, also named oily water, contains several contaminants (organic and inorganic compounds); the oily water composition depends on the oil field life. This produced water must be treated in order to be reused or discharged without causing negative environment impacts1.

Environmental impact is evaluated by toxicity and contaminants content. Nowadays, the main point when purifying produced water is related to the contaminants, which remain dissolved, and then are more difficulty to be removed1.

In order to ensure the quality of the produced water discharge, the "Brazilian Council of Environment" has established that the waxes and oil content must be 20 mg/L2.

Oily residues, containing small concentration of oil, generate difficulties in water treatment because the phases can be mixed by shear through the equipments, and they can form stable emulsions3.

The reduced size of dispersed oil droplets presents in oily water is the main drawback to be turned round during the treatment of this residue. The main alternative to remove this oil is increasing the dispersed droplets, followed by further separation through physical methods (decantation, centrifugation, membrane filtration, flotation)4.

Nowadays, the industry uses flocculation/flotation processes and hydrocyclones to oily water purification, but several contaminants still remain water-soluble. Several other processes have been used to decrease the oil and contaminants concentration in the produced water.

Spherical and porous copolymers based on vinyl monomers are already used to medicaments and biotechnology5. Although they present potential application in the contaminants removal from produced water, little information has been found in the literature.

These copolymers can be used in several applications because it is possible to control their external (particle size distribution) and internal morphology (porosity and specific area).

The particle size of the polymer depends on aqueous phase/ organic phase ratio, suspension agent (type and concentration), temperature and stirring speed. The formation of porous structure does not depend on monomers chemical structure; it depends only on reaction conditions, such as, dilution degree, diluent type and cross-link degree.

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