Tribological behaviours of Cu nanoparticles recovered from electroplating effluent as lubricant additive

Nowadays, many efforts have been made to minimise the pollution risks of copper electroplating effluent, such as chemical methods, physical methods, etc. Among them, chemical reduction has been used in this paper for its simplicity and potential for industrial production, and the recovered Cu nanoparticles (CuNPs) were innovatively used as a lubricant additive to prolong the lifetime of lubrication equipment and enhance energy conservation via emission reduction. In this paper, the relationships of the remaining Cu²⁺ concentration ([Cu²⁺]) with NaBH₄/CuSO₄ mole ratio, reaction time and reaction temperature were discussed separately. Then, L₉(3³) orthogonal experiment was carried out to determine optimal reaction conditions. Finally, the tribological behaviours [e.g. friction coefficients (FCs) and wear scar diameter (WSD)] of base oil samples with and without addition of the recovered CuNPs were investigated. Results indicate that the optimal reaction conditions were as follows: NaBH₄/CuSO₄ (4 : 6) react at 30°C for 25 min, under which [Cu²⁺] was minimised to 0·2 mg L^-1 with a mean particle size of 33 nm. The FC and WSD of oil with 0·3 wt-%CuNPs were decreased by 33?4 and 19% respectively compared with the base oil. This compound oil was much more suitable for moderate load and high load than for low load. This paper provides a new idea on dealing with the copper electroplating effluent.