Efficient demulsification of wastewater by steel furnace dust with amphiphilic and surface charge properties

• BFD steel waste is an efficient demulsifier for oil/water separation.
• This process can achieve 98.5% TOC removal.
• After the wastewater treatment, BFD can be regenerated by thermal treatment.
• The wastewater treatment creates an environmentally suitable destination for BFD.

In this work, blast furnace dust (BFD), a steel industry waste, was used as a demulsifier for highly efficient removal of the organic oil contaminant of metal working wastewater. Batch experiments showed that a simple mixture and stirring of BFD with stable emulsified wastewater containing metalworking oil (TOC ca. 15,000 mg L−1 and 1500 NTU) led to 90–98% TOC removal at pH lower than 7. Scanning electronic microscopy, X-ray diffraction, Mossbauer, thermogravimetric analysis, and Raman analyses suggest that the removal of the stable oil micelles is a combination of two synergic processes: (i) an electrostatic capture of the stable negatively charged oil droplets by the positive BFD particles followed by (ii) a strong interaction with the oil and the hydrophobic carbon surface. Preliminary results showed that BFD can be regenerated and reused by simple extraction or thermal treatment.

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