Effect of pH or Metal Ions on the Oil/Water Interfacial Behavior of Humic Acid Based Surfactant

Abstract

Humic acid, a kind of widespread organic macromolecule on earth, is naturally formed through the microbial biodegradation of plant, animal, and microorganism residues. Because of the large number of active functional groups (phenolic hydroxyl and carboxyl), humic acid has been considered as a biocompatible, green, and low-cost biosurfactant recently. In this work, based on the sensitivity of humic acid to the external chemical environment, the oil/water interfacial behavior of sodium humate at different pH or in the presence of metal ions is closely investigated. Sodium humate is significantly enriched toward the oil/water interface at either low pH or high metal-ion concentration to adjust the properties of the prepared emulsion, but the mechanisms are proved to be different when considering the influence of pH and metal ions. Besides, to the best of our knowledge, humic acid based surfactant is proposed as a Pickering emulsifier for the first time, known as solid surfactant. This work promises the great potential of humic acid as a natural environment-responsive surfactant and has important implications for the application of humic acid based surfactant in industry and understanding of the role of humic acid in the natural environment.

Effect of Humic Acid on Soil Physical and Chemical Properties, Microbial Community Structure, and Metabolites of Decline Diseased Bayberry

“…Indeed, HA is not only a component of humus, but also an organic macromolecule produced by the microbial biodegradation of plant, animal, and microbial residues. Due to the presence of several active functional groups (phenolic hydroxyl and carboxyl), HA has been regarded as a biocompatible, environmentally friendly, and affordable biosurfactant [ 4 , 5 ].…”

Self-Stabilizing Encapsulation through Fast Interfacial Polymerization of Ethyl α-Cyanoacrylate: From Emulsions to Microcapsule Dispersions

“…Besides, a reinjection experiment was carried out, wherein the liquid filled the space of the wrinkled film before homogeneously expanding, which suggests the viscoelastic performance of the polymer film at the interface (Figure 2b and Movie S3). To date, such an attractive phenomenon was only reported in the systems of fine interfacial self-assemblies, 32 interfacial ionic cross-linking, 25,33 and Pickering emulsions, in which the thermal energy is usually less than the desorption Gibbs free energy, resulting in irreversible adsorption of interface-active substances at the interface. 34,35 In this research, polyECA formed via FIP is steadily jammed at the interface due to the combination of the amphiphilicity characteristic of the covalently linked initiator-polyECA product and the entanglement between polymer chains, which provide the droplets with the strong interfacial viscoelastic property.…”

Fast Interfacial Polymerization for Stabilizing Emulsion Droplets with Polymer Films beyond Emulsifiers

“…Amphiphilic organic and inorganic solid particles have shown advantages in stabilizing emulsion droplets and have attracted more and more attention in recent years. , Emulsions stabilized by nanometer or micrometer particles were first disclosed by Ramsten and Pickering in the early 1900s . Particle-stabilized emulsions are commonly defined as Pickering emulsions.…”