This research examined the correlation between the detergency of soils with varying equivalent alkane carbon numbers (EACNs) and hydrophilic-lipophilic deviation (HLD) values. The detergency of oily soils with EACNs ranging from 5.2 to 16.6 was evaluated using C10-4PO-SO4Na as a primary surfactant system and a 1:1 binary mixture of C10-4PO-SO4Na and AOT as a confirmatory surfactant system (with 65/35 polyester/cotton at 25oC). These surfactant systems were characterized using HLD concepts which showed that C10-4PO-SO4Na was more hydrophilic (had a higher negative Cc value) than that of the mixed surfactant system. Detergency of the selected soils was evaluated at different salinities corresponding to HLDs ranging from negative to positive values. The results showed that detergency of all soils increased with increasing salinity (starting with an HLD = -3 (Type I)), reached the maxima at widely different optimum salinities (Ss*) but an identical HLD value of zero (optimum Type III), and then decreased with further increasing salt levels corresponding to positive HLDs (Type II). The preferred HLD range from -3 to zero showed detergency levels exceeding 85% removal with interfacial tension values (IFTs) below 1 mNm-1 for all oily soils studied. Detergency of semisolid octadecane (EACN = 18) was further conducted and demonstrated that performing detergency at HLD = -3 to zero likewise revealed superior soil removal over 85% than systems outside this HLD range. Thus, this work highlighted the utility of using the HLD approach in design surfactant formulations for detergency of widely varying types of soils.
