Recovering low-turbidity cutting liquid from silicon slurry waste

Area of Science:

• Materials Science
• Chemical Engineering
• Waste Management

Background:

• Silicon slurry waste contains polyalkylene glycol (PAG), a valuable industrial lubricant.
• Efficient recovery of PAG from waste streams is crucial for sustainability and cost reduction.

Purpose of the Study:

• To develop an effective method for recovering low-turbidity PAG from silicon slurry waste.
• To identify the optimal diluent for PAG recovery through sedimentation.

Main Methods:

• Sedimentation experiments were conducted using PAG waste with varying diluents (water, ethanol, acetone) at adjusted temperatures.
• The turbidity and solid content of the recovered PAG were measured.
• Recovered PAG was analyzed for viscosity and density after vacuum distillation.

Main Results:

• Water was identified as the most effective diluent, promoting particle aggregation and settling due to lower surface potential and steric stabilization.
• Sedimentation with 50 wt.% water resulted in a solid content of 0.122 g/L and turbidity of 44 NTU.
• Vacuum distillation of water-assisted recovered PAG yielded a final product with 0.37 NTU, comparable viscosity, and density to unused PAG.

Conclusions:

• Water is the recommended diluent for recovering low-turbidity PAG (<100 NTU) from silicon slurry waste by sedimentation.
• The developed method allows for the recovery and reuse of PAG, reducing waste and conserving resources.
• Recovered PAG exhibits properties suitable for re-application in cutting processes.