Electromembrane extraction of sodium dodecyl sulfate from highly concentrated solutions

Analyst Pub Date: 2020-05-16 DOI: 10.1039/D0AN00622J

Abstract

This fundamental work investigated the removal of sodium dodecyl sulfate (SDS) from highly concentrated samples by electromembrane extraction (EME). SDS concentrations were in the range of 0.1–1.0% w/v, covering both sub- and super-critical micellar concentrations (CMC). Under optimal conditions, we extracted SDS from 100 μL aqueous sample, through 3 μL supported liquid membrane (SLM) and into 200 μL 10 mM NaOH in water as waste solution. The SLM comprised 1.0% w/w Aliquat 336 in 1-nonanol, and extraction voltage was 5 V. From 0.1% SDS samples, EME removed 100% during 30 minutes operation (100% clearance). SDS concentration above the critical micellar concentration (CMC) challenged the capacity of the system. Thus, to reach 100% clearance from 0.5% samples, we extracted for 120 minutes and replenished the SLM after 60 minutes. Increasing the membrane area of the SLM from 28 mm2 to 43 mm2 provided 100% clearance from 0.5% samples after 30 min EME. Complete clearance of 1.0% SDS samples was not achieved under the tested conditions, and maximal clearance was 60%. Mass balance experiments demonstrated that most of the removed SDS is trapped in the SLM, rather than transferring to the waste solution. For super-CMC samples, aggregation of SDS in the SLM exceeded the SLM capacity and impeded further mass transfer.

Graphical abstract: Electromembrane extraction of sodium dodecyl sulfate from highly concentrated solutions
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