Chemical Destabilization of Fresh and Spent Cutting Oil Emulsions: Differences between an Ecofriendly and Two Commercial Synthetic Lubricants

Abstract

The aim of this study was to evaluate if eco-friendly lubricants had an additional advantage over conventional synthetic lubricants in terms of emulsion treatment of metalworking wastewater. To these purpose, two fresh commercial synthetic cutting oil emulsions were compared with an emulsion obtained from a new cutting oil produced from the reuse of slaughtering waste (CADT-605 from Kimya Srl, Bari, Italy). The breaking of the fresh emulsions was carried out with the addition of small amounts of sulfuric acid (2–20 mL/L) followed by pH neutralization by means of calcium hydroxide. During the two-step treatments, COD, BOD5 and non-ionic surfactant (NIS) concentrations were monitored in the aqueous phase. The results demonstrated that the best results were obtained with the emulsion produced with the bio-based lubricant. In addition, this cutting oil was tested in a metalworking plant within 30 days and the resulting spent emulsion was treated with the proposed process. In all the cases, the treatment led to a drastic decrease of the COD, BOD5 and NIS contents that allow the discharge of resulting aqueous phase in sewers or in surface water bodies, together with the other wastewater produced by the plant, in agreement with the Italian regulation.

Reuse of Treated Slaughterhouse Wastewater from Immediate One-Step Lime Precipitation and Atmospheric Carbonation to Produce Aromatic Plants in Hydroponics

“…During the AC process, no reagent or energy consumption is expected. Therefore, considering these assumptions and that the average price of hydrated lime is €220/ton [45], it is expected that the proposed treatment system (IOSLM + AC + hydroponics) will have an average operating cost of €6.73/m 3 . Around 95.5% of this operating cost corresponds to energy costs.…”

Pilot‐scale treatment cycle comprising membrane, thermal, and adsorption processes for spent metalworking fluids remediation

“…[4][5][6] In recent years, the production of MWFs with less toxic and more biodegradable oils from renewable resources, such as vegetable or animal wastes deriving from the agro-food sectors, has been increasing. 7,8 However, the use of synthetic and mineral oils for MWF production is still the most common practice. These oils are characterized by low biodegradability and high toxicity, thus representing a critical threat for operators' health 9 and for the environment.…”

“…In recent years, the production of MWFs with less toxic and more biodegradable oils from renewable resources, such as vegetable or animal wastes deriving from the agro‐food sectors, has been increasing 7,8 . However, the use of synthetic and mineral oils for MWF production is still the most common practice.…”

Exploring the frictional characteristics of kelp liquid as an environmentally friendly lubricant

“…Emulsified cutting fluids have superior cooling and lubricating properties which are used extensively in the machining industry (Wang et al , 2018). Spasiano et al (2020) explored the wastewater treatment of failed emulsions of bio-based lubrication and commercial synthetic cutting oil emulsions to achieve direct discharge of waste fluids, and the results showed that the new metalworking bio-based oils are simple to handle. Suvin et al (2020) developed a biodegradable emulsifier cutting fluid using coconut oil as an additive, and their drilling experiments showed that the performance of the cutting fluid was not significantly different from that of commercial emulsifiers, as well as being environmentally friendly and sustainable.…”