Eliminate the Metal Ion in the Edible Oil Based on High Extraction pH‐Switchable Deep Eutectic Solvents

In this paper, High extraction pH‐switchable deep eutectic solvents (SDESs) were prepared with fatty acid. The high extraction of SDESs is attributed to the fatty acid complex with metal ions in the extracting process. The SDES‐1 was selected as an optimum reagent to extract metal ions from edible oil. The study showed that, in the phase switching, the longer the carbon chain of the fatty acid, the more NaOH is consumed. Only part of the fatty acid participates in the acid‐base reaction during the phase switching. The SDES‐1 is a good extraction of metal ions. All of the Mn ²⁺ in edible oil was extracted when V _SDES−1 : V _sample was 2:1, and SDES‐1 extracts Mn ²⁺ 2 times. The 100 g/L NaOH and GR HCl were selected in the process of phase change. The recovery test shows that the edible oil was separated when SDES‐1 turned into the hydrophilic SDES‐1 salt solution. The Mn ²⁺ was well cleared by adding saturated EDTA‐2Na reagents ( V _sample : V _EDTA−2Na  = 1:10) after 3 times. The SDES‐1 was successfully used to clear Mn ²⁺ in the rapeseed oil.