Regeneration of bleaching clay waste by chemical activation with chloride salts.

Spent bleaching earth (SBE) was regenerated by chemical activation with low cost and low pollution chlorides as activating agents. Under the conditions of activation temperature of 600d egrees C and holding time of 1 h investigated, results show that fresh bleaching earth and regenerated bleaching earth are type IV with hysteresis loops corresponding to type H3 from nitrogen adsorption-desorption isotherms, indicating slit-shaped mesoporous structure. It is also found that the effect of the regeneration treatment studied in the present work on the pore structures and chemical properties of the resulting solids is negligible compared to the fresh bleaching earth. On the other hand, the pore properties of these chemically activated solids are higher than those of the sample regenerated from heat regeneration, but only approximate 45% of surface area are reclaimed. It implies that the carbon residues could be retained within pores and/or clogs the entrance of pores, resulting in a decrease in pore properties.