Highly efficient and recyclable depth filtrating system using structured kapok filters for oil removal and recovery from wastewater.

A depth filtrating system with rotatable and taper-shaped filter column was reported to highly remove and recover oil from wastewater. In the work, structure filters made of kapok fibers were prepared by air-laying-bonding method. The oil removed from wastewater was then recovered from the oil-loaded filter by rotating the filter column, and the resulted filter was reused. The filtrating system demonstrated extremely high oil/water separation in which oil was completely retained by the filter at the first 20-100min while water passed through the filter's body with a flow rate of 560mL/min using 11,500-13,150mg/L vegetable oil or diesel polluted water. A total of 47.6-176.4L clean water was collected after four cycles of filtration and centrifugation. The separating process depended on filter's structure (packing density) and properties of model oils. The wetted filters which absorbed up to 795.6g (32.31g/g) of oils were centrifuged to recover 80-91% of the oils. The sorption capacity appeared to become constant until 4 cycles of filtration after an apparent drop of 1-6g/g in the second cycle, because of unrecoverable residual oil (2-5g/g). The decrease of flow rates was favorable to filtration of low viscous oil.