Coal gasification slag is a solid waste generated during the coal gasification process.Coal gasification slag generated in Inner Mongolia region,China is mixed with cement,quicklime and CaSO4 to prepare ceramsite through a non-sintering method.Result shows that the optimal raw materials mass ratio is coal gasification slag∶cement∶quicklime∶CaSO4=70∶30∶2.5∶5.Specific surface area of non-sintered ceramsite prepared under this ratio can reach 51.7 m2·g-1,bulk density is 809 kg·m-3,and particle crushing strength is 6.61 MPa.Using this ceramsite as a filler for denitrification biofilters results in a faster biofilm formation rate than using ordinary commercially available ceramsite.Chemical oxygen demand(COD)decreases from 300 mg·L-1 to below 60 mg·L-1,with a removal rate over 80%when the prepared ceramsite is used as fillers for denitrification biofilters and the hydraulic retention time(HRT)is 12 h.The content of nitrate nitrogen(NO3--N)decreases from 60 mg·L-1 to below 2 mg·L-1,with a removal rate over 95%.This routine achieves re-utilization of coal gasification slag and provides a new filler for wastewater denitrification treatment.
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