Reversible Stability of Emulsion and Polymer Latex Controlled by Oligochitosan and CO2

Abstract

The addition of salt to a colloid solution ensures that emulsions can be easily separated into two phases and that polymer latexes can be coagulated. The switchable stability of emulsions and polymer latexes would improve the properties for their current applications. A switchable process of salt addition can be achieved using CO2 and switchable water, and it is a novel, benign approach to achieving a switchable ionic strength in an aqueous solution. However, the problem associated with switchable water is that its additives are all synthetic tertiary amines, most of which are harmful to human beings and the environment. Oligochitosan, as a natural product, can also be used as a switchable water additive. In this paper, a new switchable water system using oligochitosan to change the ionic strength was explored for use in several potential industrial applications. The conductivity of the aqueous solution of oligochitosan (0.2 wt.%) was switched from 0.2 to 331 μS/cm through the addition and removal of CO2. Oligochitosan and CO2 were successfully utilized to reversibly break a crude oil emulsion. Polystyrene (PS) latexes could also be reversibly destabilized; the zeta potential of the PS latex changed between −5.8 and −45.2 mV in the absence and presence of CO2 after oligochitosan was dissolved in the PS latex. The use of oligochitosan is a more environmentally friendly means for reversibly separating colloid solutions.

Reversible stability of colloids switched by CO2 based on polyhexamethylene guanidine

“…Because of this reversible reaction, the amino compound can be in the form of an inorganic salt in a colloid system, and a reversible equilibrium of emulsification and demulsification is reached by alternating between N 2 and CO 2 . 21 We attempted utilizing oligochitosan as eco-friendly CO 2 switchable water, 22 but the issue is that low protonation of oligochitosan after sparging CO 2 , needs a large amount of oligochitosan in colloids.…”

Bio‐based mixed CO2‐switchable surfactant for reducing viscosity of heavy oil

“…In response to external stimuli such as light (Eastoe et al, 2004), temperature (Binks et al, 2005; Zoppe et al, 2012), pH (Morse et al, 2013), CO 2 (Liu et al, 2006), and so forth, the microscopic appearance and macroscopic characteristics of switchable surfactants undergo a substantial transformation. They have substantial application potential in the oil and gas industry (Klier et al, 2000; Li et al, 2018) and drug delivery (Fernandes et al, 2016; Kogan & Garti, 2006). Using CO 2 as an external trigger to modify the properties of aqueous solutions with CO 2 ‐switchable surfactants is a simple and environmentally beneficial way.…”

“…In the realm of surfactants, bio‐based surfactants are made from biomass, representing a way forward for environmentally friendly (Foley et al, 2012). Glucose and amino acids are excellent building blocks for hydrophilic head groups for surfactant (Li et al, 2018); Natural oils and fats act as hydrophobic groups, bio‐based surfactants can be manufactured. The abundance of amino acids and their derivatives in nature has resulted in amino acid‐based surfactants with good surface activity and biodegradability.…”

Low‐Molecular‐Weight Polymer with CO2‐Switchable Surface Activity

“…However, as the cost of amidine, guanidine, and imidazole is higher than that of the amino compounds, the latter compounds have a greater application value in the field of CO 2 switching. CO 2 and amino compounds' main reaction mechanism is the protonation of primary, secondary, and tertiary amines to form carbonate, bicarbonate, and carbamate (Jiang et al, 2020; Li et al, 2018) species, generating many positive and negative ions in the solution. Furthermore, the temperature increases or N 2 introduction eliminates the protonation reaction.…”

“…Previously, our group used oligochitosan as the CO 2 trigger to perform reversible emulsion behaviors. However, issues arise for real applications because oligochitosan is expensive (Li et al, 2018).…”