Compatibility of nonionic and anionic surfactants with persulfate activated by alkali in the abatement of chlorinated organic compounds in aqueous phase

Raul García-Cervilla; Aurora Santos; Arturo Romero; David Lorenzo

doi:10.1016/j.scitotenv.2020.141782

Compatibility of nonionic and anionic surfactants with persulfate activated by alkali in the abatement of chlorinated organic compounds in aqueous phase

Sci Total Environ. 2021 Jan 10:751:141782. doi: 10.1016/j.scitotenv.2020.141782. Epub 2020 Aug 19.

Authors

Raul García-Cervilla¹, Aurora Santos², Arturo Romero³, David Lorenzo⁴

Affiliations

¹ Chemical Engineering and Materials Department, University Complutense of Madrid, Spain. Electronic address: raugar05@ucm.es.
² Chemical Engineering and Materials Department, University Complutense of Madrid, Spain. Electronic address: aursan@quim.ucm.es.
³ Chemical Engineering and Materials Department, University Complutense of Madrid, Spain. Electronic address: aromeros@quim.ucm.es.
⁴ Chemical Engineering and Materials Department, University Complutense of Madrid, Spain. Electronic address: dlorenzo@ucm.es.

PMID: 32882562
DOI: 10.1016/j.scitotenv.2020.141782

Abstract

Surfactant Enhanced In-Situ Chemical Oxidation (S-ISCO) is an emerging technology in the remediation of sites with residual Dense Non-Aqueous Phase Liquids (DNAPLs), a ubiquitous problem in the environment and a challenge to solve. In this work, three nonionic surfactants: E-Mulse3® (E3), Tween80 (T80), and a mixture of Tween80-Span80 (TS80), and an anionic surfactant: sodium dodecyl sulfate (SDS), combined with persulfate activated by alkali (PSA) as oxidant have been investigated to remove the DNAPL generated as liquid waste in lindane production, which is composed of 28 chlorinated organic compounds (COCs). Because the compatibility between surfactants and oxidants is a key aspect in the S-ISCO effectiveness the unproductive consumption of PS by surfactants was investigated in batch (up to 864 h) varying the initial concentration of PS (84-42 mmol·L^-1) and surfactants (0-12 g·L^-1) and the NaOH:PS molar ratio (1 and 2). The solubilization capacity of a partially oxidized surfactant was analyzed by estimating its Equivalent Surfactant Capacity, ESC, (as mmol_{COCs dissolved}g_surf^-1) and comparing it to the expected value for an unoxidized surfactant, ESC_o. Finally, the abatement of DNAPL with simultaneous addition of surfactant and PSA was studied. At the conditions used, a negligible unproductive consumption of PS was found by SDS; meanwhile, PS consumption at 360 h ranged between 70 and 80% using the nonionic surfactants. The highest ratios of ESC/ESC_o were found with SDS and E3 and these surfactants were chosen for the S-ISCO treatment. When oxidant and surfactant were simultaneously applied for DNAPL abatement the COC conversion was more than three times higher with E3 (0.6 at 360 h) than SDS. Moreover, it was obtained that the time needed for the removal of a mass of DNAPL by PSA in the absence of surfactants was notably higher than the time required when a suitable surfactant was added.

Keywords: DNAPL; Lindane wastes S-ISCO; Nonionic and anionic surfactants; Persulfate activated by alkali.