Estratégia sequencial de remediação de areia contaminada por petróleo usando microemulsões bio-baseadas

Abstract

Oil spills in coastal zones cause persistent environmental impacts due to the deposition of hydrocarbons in soils and sediments, and the scientific literature still lacks remediation formulations that combine high efficiency with low environmental impact. Previous studies have demonstrated the effectiveness of anionic and nonionic surfactants in microemulsion systems; however, most of these formulations are based on petrochemical inputs, which are highly toxic and poorly biodegradable. To address this gap, this doctoral research aimed to develop, characterize, and apply environmentally friendly microemulsions formulated with plant-based components as sustainable cleaning agents for the ex situ remediation of beach sand contaminated with crude oil. The investigated system consisted of pine essential oil (oil phase), saponified coconut oil soap (anionic surfactant), isopropanol (cosurfactant), and water (aqueous phase). Pseudoternary phase diagrams were constructed to determine stability regions, and a full 2^3 factorial design was employed to evaluate the effects of the microemulsion volume-to- sand mass ratio, contact time, and sediment mass. Removal efficiency was quantified by UV– Vis spectroscopy and gas chromatography. The formulated cleaning agent exhibited physicochemical stability, low toxicity, and high biodegradability, as confirmed by the chemical safety data sheets of its components. Experimental results indicated oil removal efficiencies of up to 90% in batch tests, with superior performance for formulations containing 30–60% of the oil phase. An additional conceptual contribution was the proposal of a sequential remediation strategy based on micellar regeneration, in which the initial washing step with the microemulsion is followed by an aqueous rinse capable of remobilizing adsorbed surfactant molecules, promoting new in situ micellar self-assembly within the sediment. This approach achieved up to 96.5% oil removal in fixed-bed column experiments, with 96% volumetric recovery of the microemulsion and a favorable environmental profile according to green chemistry metrics. Overall, the results demonstrate that bio-based microemulsions are effective and sustainable alternatives for the remediation of petroleum-contaminated coastal environments, contributing to advances in green chemistry and emerging environmental applications.