Application of Hydrophilic–Lipophilic Deviation Equations to the Formulation of a Mixed‐Surfactant Washing Agent for Crude Rice Bran Oil Removal from Spent Bleaching Earth

Abstract

AbstractIn Thailand, spent bleaching earth (SBE) (20–40 wt.% remaining oil), an industrial waste from edible oil refineries, has usually been disposed of by improper landfilling at industrial sites. This study aims to formulate microemulsion‐based washing solutions from mixed surfactants for cleaning SBE contaminated with crude rice bran oil using the hydrophilic–lipophilic deviation (HLD) concept. Binary nonionic‐anionic surfactant mixtures consisting of System A (Dehydol LS3TH‐Levenol WX), System B (Dehydol LS5TH‐Levenol WX), and System C (Dehydol LS7TH‐Levenol WX) were formulated for use as microemulsion‐based washing formulations. A HLDmixed equation extended with the excess free energy term (GEX/RT) was developed and proposed for predicting the optimum salinity. The optimum salinities obtained from the HLDmixed equation were close to those obtained from the phase behavior. In the SBE washing study, the mixed‐surfactant systems showed a washing efficiency of 90% with low surfactant adsorption capacity on bleaching earth (qmax = 0.01–0.03 mol g−1). The mixed surfactants showed improved washing performance compared to that of the single‐surfactant system. This work highlights the utility of using the HLD concept in designing microemulsion‐based washing formulations from surfactants for the removal of vegetable oil from SBE.