Efficient Removal of Sulfur Hexafluoride (SF₆) Through Reacting with Recycled Electroplating Sludge

This paper reports that recycled electroplating sludge is able to efficiently remove greenhouse gas sulfur hexafluoride (SF₆). The removal process involves various reactions of SF₆ with the recycled sludge. Remarkably, the sludge completely removed SF₆ at a capacity of 1.10 mmol/g (SF₆/sludge) at 600 °C. More importantly, the evolved gases were SO₂, SiF₄, and a limited amount of HF, with no toxic SOF₄, SO₂F₂, or SF₄ being detected. These generated gases can be readily captured and removed by NaOH solution. The reacted solids were further found to be various metal fluorides, thus revealing that SF₆ removal takes place by reacting with various metal oxides and silicate in the sludge. Moreover, the kinetic investigation revealed that the SF₆ reaction with the sludge is a first-order chemically controlled process. This research thus demonstrates that the waste electroplating sludge can be potentially used as an effective removal agent for one of the notorious greenhouse gases, SF<sub>6