Concave soil-based lightweight dual-core filter material and preparation method thereof

The invention provides a concave soil-based lightweight dual-core filter material. The concave soil-based lightweight dual-core filter material comprises a concave soil-based outer core layer on the outer side of the filter material, an air layer in the middle, and a concave soil-based inner core layer on the inside. The concave soil-based outer core layer includes concave soil and may contain a pore expanding agent, the concave soil of the concave soil-based inner layer is waste concave soil or ordinary concave soil and may contain biomass garbage. Raw materials of the concave soil-based inner core layer are taken and placed into a calciner for calcination, cooled, and placed in a granulator, and pellets of 5-6 mm are prepared; after raw materials of the concave soil-based outer core layer are taken and put into the granulator, the pellets are coated to obtain double-layer pellets of 6-7mm; and then calcination and cooling are conducted. The raw materials are cheap and easy to obtain,in addition, the biomass