The tribological performances of fullerenol and nanodiamonds (NDs) as additives in water-based lubricants for amorphous carbon (a-C) coatings are investigated to avoid disadvantage factors, such as chemical reactions and deformation of particles. The effects of size and additive amount on tribological properties of nanoparticles are studied by rigid nanoparticles within the dot size range. The results show that owing to its small particle size (1–2 nm), fullerenol cannot prevent direct contact of the friction pair at low concentration conditions. Only when the quantity of fullerenol increased to support the asperity contact loads in sufficient concentration did nano-bearings perform well in anti-friction and anti-wear effects. Unlike fullerenol, nanodiamond particles with a diameter of about 5–10 nm show friction-reducing effect based on the nano-bearing effects at ultra-low concentration (0.01 wt.%), whereas particles at higher concentration block the rolling movement, hence increasing the coefficient of friction (COF) and wear. As a result of the effect of difference in size, fullerenol provides a better overall lubrication, but it is hard to reach a friction coefficient as low as NDs even under the optimal conditions.

Titanium alloys present challenges in terms of lubrication due to their difficult-to-machine nature, which necessitates the development of sustainable and environmentally friendly lubricants. Water-based lubricants are commonly used for titanium alloys because of their effective cooling properties, despite encountering challenges such as poor lubrication performance and complex mechanisms. This study first demonstrates that polyacrylamide (PAM) is an excellent water-based lubricant additive for the Ti6Al4V (TC4)/GCr15 interface. It results in a reduction of friction and wear in TC4 contacts by 40% and 90%, respectively, when utilizing a low concentration of 2.5 wt%. It is also found that oxidative wear is present on the rubbing surfaces of TC4 when exposed to water at ambient temperature. The exceptional lubricating properties of PAM can be attributed to the formation of a boundary lubrication film, which occurs through the adsorption of PAM onto tribo-oxide layer. Increased concentrations of PAM promote chemisorption and hydrogen-bond interactions, thereby increasing the stability of the boundary lubrication film.

Nanomaterials, such as Graphene, h-BN nanoparticles and MoS₂ nanotubes, have shown their ability in improving the tribological performance of amorphous carbon (a-C) coatings. In the current study, the effectiveness of ZrO₂ nanoparticles (ZrO₂-NPs) in lubricating the self-mated nonhydrogenated a-C contacts was investigated in boundary lubrication regime. The results showed that 13% less friction and 50% less wear compared to the base oil were achieved by employing ZrO₂-NPs in the base oil in self-mated a-C contacts. Via analyzing the ZrO₂-NPs and the worn a-C surface after tests, it was found that the improved lubrication by ZrO₂-NPs was based on “polishing effects”, which is a new phenomenon observed between a-C and nanoparticles. Under the “polishing effect”, micro-plateaus with extremely smooth surface and uniform height were produced on the analyzed a-C surface. The resulting topography of the a-C coating is suitable for ZrO₂-NPs to act as nano-bearings between rubbing surfaces. Especially, the ZrO₂-NPs exhibited excellent mechanical and chemical stability, even under the severe service condition, suggesting that the combination of nonhydrogenated a-C coating with ZrO₂-NPs is an effective, long lasting and environment-friendly lubrication solution.

In this paper, histidine was applied to treat vanadium-containing wastewater. Several independent experimental parameters, including H₂SO₄ concentration, dosage of histidine, reaction time and reaction temperature, were investigated and optimized through response surface methodology. The influence on the reduction process decreased in the following order: dosage of histidine > reaction temperature > reaction time. The reduction efficiency could be achieved at 95.77% under the following reaction conditions: H₂SO₄ concentration of 0.2 mol/L, reaction temperature of 90 °C, dosage of histidine at n(His)/n(V) = 3.6, reaction time of 60 min and stirring rate at 500 rpm. The reduction kinetics was followed successfully with the pseudo-first-order kinetics model and the Ea for reduction of vanadium was calculated to be 25.31 kJ/mol. The reduction kinetics was affected by these factors and the kinetics model could be described by an Equation. This paper provides a versatile strategy for treatment of wastewater containing V(V) and shows a bright tomorrow for wastewater treatment.