Novel Electrochemical Treatment of Spent Caustic from the Hydrocarbon Industry Using Ti/BDD

Abstract

During the crude oil refining process, NaOH solutions are used to remove H2S, H2Saq, and sulfur compounds from different hydrocarbon streams. The residues obtained are called “spent caustics.” These residues can be mixed with those obtained in other processes, adding to its chemical composition naphthenic acids and phenolic compounds, resulting in one of the most dangerous industrial residues. In this study, the use of electrochemical technology (ET), using BDD with Ti as substrate (Ti/BDD), is evaluated in electrolysis of spent caustic mixtures, obtained through individual samples from different refineries. In this way, the Ti/BDD’s capability of carrying out the electrochemical destruction of spent caustics in an acidic medium is evaluated having as key process a chemical pretreatment phase. The potential production of•OHs, as the main reactive oxygen species electrogenerated over Ti/BDD surface, was evaluated in HCl and H2SO4through fluorescence spectroscopy, demonstrating the reaction medium’s influence on its production. The results show that the hydrocarbon industry spent caustics can be mineralized to CO2and water, driving the use of ET and of the Ti/BDD to solve a real problem, whose potential and negative impact on the environment and on human health is and has been the environmental agencies’ main focus.

Evaluating the electrochemical and photoelectrochemical production of hydroxyl radical during electrocoagulation process

“…and energy dispersive X-ray analysis (EDX) were employed. Typical conditions for this type of analysis have been reported elsewhere [27]. Fig.…”

“…The resulting solution was irradiated at different time intervals from 0 to 100 min. The characterization and activation of Ti|IrO2-TaO5 has been previously reported [27].…”

Contribution of cathodic hydroxyl radical generation to the enhancement of electro-oxidation process for water decontamination

“…It can then be assumed that the different O2-evolution overpotentials in these media could have a significant impact on the formation of said species. In earlier work [55], the much superior • OH production in H2SO4 as compared to HCl has been reported and hence, the former acid was selected for subsequent trials.…”

“…A discharge with high organic load not only entails a longer electrochemical treatment, but it can also have influence on the electrochemical performance of the Ti/BDD anode. Phenol concentration in industrial phenolic waste can vary between 2,000 and 11,000 mg dm -3 , attaining more than 100,000 mg dm -3 in terms of chemical oxygen demand [52,55]. To evaluate the electroactivity of phenol at the Ti/BDD surface in 0.5 mol dm -3 H2SO4, a cyclic 12 voltammetric study was made considering two potential regions.…”