Surface-active physicochemical characteristics of spent bleaching earth on soil-plant interaction and water-nutrient uptake: A review

The activated or neutral form of bentonite-based spent bleaching earth/clay (SBE) is a by-product generated during the bleaching process in edible oil refinery. Its untreated form is disposed of directly at landfills involving high cost and land area, and possibly causing environmental problems. Recently, this undesirable dumping exercise has been prohibited. To overcome this, SBE is regenerated and reused for value addition, e.g. as bio active materials for water/wastewater treatment. A more recent approach being converting SBE into bio fertilizers; of which the fertilizer characteristics in relation to physical, chemical and biological interaction with soil and its surrounding ecosystem (nutrients, water, pollutants, microorganisms, climate, etc.) is vital in agricultural applications associated with soil fertility management and crops productivity. Previously, SBE's structural characteristics, surface chemistry and activation have been disclosed. This paper provides an insight on soil-crop interactions and agronomy with SBE functions as a soil amendment.