N-oleoylsarcosine has excellent biodegradability and high foaming properties, which is widely applied in the fields of cosmetics and chemical industry. Due to the presence of carboxyl and amide group within N-OSS molecular, N-oleoylsarcosine shows good water solubility and reactivity which allows it to bond with metal ions readily.

Effect of N-oleoylsarcosine on lubrication

The rapid adoption of the advantageous PEEK/steel pairing in many tribological applications has prompted intense research to optimize its lubrication. Thus, the role of organic friction modifiers (OFMs) in improving the lubrication of PEEK-steel contacts has been studied and their mechanism explained. Their effect on friction and wear depends on the type of contact motion (i.e. sliding or sliding-rolling) and the steel surface roughness. N-oleoylsarcosine had a significant effect on tribological properties due to its ability to absorb strongly on both materials, inhibit the formation of PEEK transfer films on steel and thus exert either a positive or negative effect depending on the test conditions. They have similar types of hydrocarbon moieties, but different polar groups. OFMs in this study were technical-grade, and contained a small amount of different hydrocarbon structures as impurities. However, the compositions of hydrocarbon structures were similar in the three OFMs, hence the main components of the effect of the OFMs were their polar groups.[1]

The Stribeck curves, representing friction coefficient values as a function of entrainment speed, for the PEEK-smooth steel contact lubricated with PAO and PAO + OFMs are summarized. While PAO showed slightly higher friction at 200% SRR (sliding) than 50% SRR (sliding-rolling), a significant friction reduction was achieved at both SRRs by the addition of   N-oleoylsarcosine (N-oleoyl sarcosine). It is meaningful to mention that when tribological tests were conducted with smooth steel balls, there was almost no wear on the PEEK plates, regardless of SRRs or lubricant formulations.The poor friction reducing properties of OFM-A and OFM-B in PEEK-PEEK and steel-steel contacts could be due to a low ability to absorb/react on either PEEK and steel surfaces under the test condition i.e. temperature employed in this study. OFM-A (olyelamine) and OFM-B (oleic acid) are widely used organic friction modifiers for many applications, but it has been reported that they generally work better at higher temperatures which accelerate the reaction of their polar groups with the surfaces. This indicates that the adsorption of   N-oleoylsarcosine is greater in 200% SRR (sliding) than 50% SRR (sliding-rolling). As explained, SRR is defined as the ratio of the sliding speed to the entrainment speed. Therefore, the sliding speeds at each entrainment speed are higher at 200% SRR than 50% SRR, causing higher frictional heat which accelerates the adsorption of   N-oleoylsarcosine. This is also supported by the fact that PAO +   N-oleoylsarcosine showed lower friction at 200% SRR than 50% SRR for the PEEK-smooth steel contact

N-oleoylsarcosine as an efficient collector

In this study, N-oleoylsarcosine was explored as an efficient collector in the flotation of spodumene from albite. The flotation behaviors were examined by micro-flotation tests and the interaction mechanisms were comprehensively uncovered from atomical scale. It indicated N-OSS could effectively collect spodumene from albite at low temperature and N-OSS was more inclined to adsorb on spodumene surface than that on albite surface, thus significantly expanding the hydrophobicity difference. X-ray photoelectron spectroscopy (XPS) analysis suggested that N-oleoylsarcosine chemically interacted with both Ca and Al active sites on Ca-activated spodumene surface. Whereas, it weakly adsorbed on Ca-activated albite. Density functional theory (DFT) calculations reconfirmed that the adsorption of N-oleoylsarcosine on Ca-activated spodumene surface was more favorable than that on albite surface. The strong adsorption on spodumene was due to the hybridization reaction between the O 2p orbitals of C-O and C=O groups of N-OSS with Ca 4s orbitals as well as Al 3s orbitals on spodumene surface. Nevertheless, N-OSS weakly interacted with Ca atoms on Ca-activated albite due to steric hindrance. N-OSS exhibited selective collecting ability at low temperature in the flotation of spodumene from albite compared with conventional collector, which has promising prospects in the low-temperature flotation of spodumene from albite.[2]

The effect of pulp temperature on the flotation of spodumene and albite in NaOL and N-oleoylsarcosine system is presented. It can be seen that the floatability difference between spodumene and albite almost maintained constant as temperature varied at N-OSS concentration of 1.5 × 10?4 mol/L, which indicated that pulp temperature had negligible influence on the flotation of spodumene and albite in N-oleoylsarcosine system.The flotation results illustrated that N-oleoylsarcosine surpassed NaOL in selectivity and temperature compatibility. For spodumene, the adsorption of N-oleoylsarcosine on both Ca and Al sites was more stable than that on Ca or Al sites alone, in which two O atoms of the C-O and C=O group involved in the bonding reaction with Al and Ca atoms, respectively. In the case of albite, two O atoms of the C-O and C=O group weakly reacted with Ca atoms with lower population values, possibly due to steric hindrance. In addition, the adsorption energy of N-OSS on spodumene surface was much bigger than that on albite surface, reconfirmed that the interaction between N-oleoylsarcosine and Ca activated spodumene surface was much stronger than that of Ca activated albite.

References

[1]Tatsumi, G., Ratoi, M., Shitara, Y., Sakamoto, K., & Mellor, B. G. (2020). Effect of organic friction modifiers on lubrication of PEEK - steel contact. Tribology International, 151, 106513. https://doi.org/10.1016/j.triboint.2020.106513

[2]Shao, H., Yang, B., Luo, H., Zhu, H., Ge, R., & Wu, J. (2024, August 1). The evaluation of N-OSS (N-oleoyl sarcosine) as an efficient collector in the flotation of spodumene from albite at low temperature: Experimental tests and atom-level calculation. Journal of Molecular Liquids, 407, 125110. https://doi.org/10.1016/j.molliq.2024.125110