Adsorption of organic acids from offshore produced water using microporous activated carbon from babassu pericarp: a low-cost alternative

Abstract

Currently, in different regions of the world, there is a growth on the rate of produced water for each barrel of oil extracted. Among the compounds observed in this water are naphthenic acids (NAs). Efforts to remove NAs from produced water must comply with local legislation and avoid damage to the environment since NAs have great toxicity. This study aimed to investigate the ability of activated carbon from the pericarp of babassu coconut (Atallea speciosa Mart. ex Spreng.) to act as an absorbent of NAs in commercial and natural (offshore) produced waters. The activated carbon was physically and chemically characterized. The maximum adsorption capacity of commercial NAs at equilibrium obtained experimentally was 25 mg g⁻¹. The activated carbon removed both NAs and other contaminants for produced water, as revealed by infrared and NMR techniques. In high-resolution mass spectrometry analysis, the abundance of the acids in the produced water was in the C9 and C10 range, being favorable for the adsorbent with a microporous structure. For the produced water kinetics experiments a maximum amount of adsorbed compounds of 17.91 mg g⁻¹ was reached, and the time to achieve equilibrium was approximately 180 min. Thus, the results show that activated charcoal from babassu coconut pericarp can be used as an adsorbent and can potentially compete with other adsorbents to remove NAs in an aqueous solution. Also, the separation process can be adopted at a low cost on platforms, complementing the operations of hydrocyclones and flotation.

Keywords:

• Characterization
• coconut-based agricultural wastes
• high-resolution mass spectrometry
• petrochemical industry
• produced water treatment
• water-soluble organics

Acknowledgments

The authors are thankful to the braazilian development agencies: CAPES (Coordination for the Improvement of Higher Education Personnel) and CNPq (National Council for Scientific and Technological Development- 444920/2014-5) for the financial aid, Multiuser Analysis Center from IQ-UFG for the technical-scientific support, and FBC (Fábrica Brasileira de Catalisadores LTDA) for the activated carbons kindly donated.

Disclosure of interest

The authors report no conflicts of interest.