Oily hot rolling mill (HRM) sludge containing a high percentage of iron oxides has been treated under microwave irradiation, and the products compared to hexane washed and thermal treated sludges. Metals present in the sludge act as a highly microwave-absorbent material, creating hot spots that trigger the stripping of the water and oils under air. The sludge looses 5 wt% of water and volatiles under 5 min of microwave irradiation (1000 W at 2450 MHz), which represents a similar reduction in weight as 4 h heating at 200 °C, but with savings in energy and time. Most importantly, after microwave irradiation, the material also shows an improvement in its rheological properties (free flowing and smaller particle size) and changes in its chemical composition. Microwaved samples are less oxidized than heated ones (lower Fe³⁺ content), which is an advantage recycling the sludge as a source of iron with lower oxidation state necessitates a lower coke:ore ratio for blast furnace operation.

含有高比例氧化铁的油性热轧机（HRM）污泥已在微波辐射下进行了处理，与经己烷洗涤和热处理的污泥相比，该产品具有较高的比重。污泥中存在的金属起着高微波吸收性的作用，产生的热点触发空气中水和油的汽提。在微波辐照5分钟（2450 MHz下为1000 W）下，污泥释放了5 wt％的水和挥发物，这与在200°C下加热4 h类似，重量减轻，但节省了能源和时间。最重要的是，在微波辐照之后，该材料还显示出其流变性质（自由流动和较小的粒径）的改善以及其化学组成的变化。微波样品的氧化程度低于加热样品（较低的Fe ³⁺ 含量），这是一个优势，将污泥作为具有较低氧化态的铁源进行循环利用，对于高炉操作而言，需要较低的焦炭/矿石比。