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2025 AOCS Annual Meeting & Expo.

Surfactants and Detergents

Applications of HLD Principles

Adjustments to the hydrophilic-lipophilic deviation (HLD) equation for salt type

Tuesday, April 29, 2025

10:35 AM – 10:55 AM PST

Room: B110-112

Presenting Author(s)

Brian Grady, PhD (he/him/his)

Douglas and Hilda Bourne Chair in Chemical Engineering
Institute for Applied Surfactant Research, University of Oklahoma
Norman, Oklahoma, United States

Co-Author(s)

ZC

Zahra Chaleshtari

Scientist
Institute for Applied Surfactant Research, University of Oklahoma, United States
SA

Steven Adamy

Associate Research Fellow
Church & Dwight Co., Inc., United States
RZ

Robert Zehr

Senior Research Chemist
Church & Dwight Co., Inc., United States
ML

Marlee Leonard

Undergraduate Research Assistant
Institute for Applied Surfactant Research, University of Oklahoma, United States
JH

Jeff H. Harwell, PhD

Professor Emeritus
Institute for Applied Surfactant Research, University of Oklahoma
NOrman, Oklahoma, United States
DS

Dave A. Sabatini

Professor Emeritus
Institute for Applied Surfactant Research, University of Oklahoma
Norman, Oklahoma, United States

Abstract:

The hydrophilic-lipophilic difference (HLD) equation is being used extensively for designing oil-in-water based surfactant systems to maximize oil solubility and minimize oil-water interfacial tension. However, the equation was developed for and almost always presumes that the salt is sodium chloride. The work described in this paper extends the equation to other monovalent cations (Li, K) and divalent anions (CO₃). The equation was adjusted for molecular weight and the number of cations in the salt. For anionic surfactants, the Hofmeister series successfully qualitatively predicts that the salt concentration to reach HLD=0 scales with Li >Na >K, i.e. the surfactant with lithium requires more salt for the water to reach the hydrophobicity required. Although the exact salt concentration depends on the anionic surfactant headgroup, the difference in optimal salinity between two cations appears to not be dependent on headgroup. Also, CO₃ reduces the activity of the cation as compared to Cl. For narrow-range alcohol ethoxylates, there is little difference between Na and K; while Li requires more salt for a given increase in hydrocarbon number of carbons to reach HLD=0. A broad-range ethoxylate gives inconsistent results, which we attribute to the finite solubility of some surfactant components in the oil.