Study On Red Mud Environmental Rehabilitation Material For The Absorption Of Heavy-metal Ion

Heavy metal ions pollution of water body is becoming a worldwide environment pollution problem,which damages the human health and life.In this study, sintered red mud and bayer red mud were used as main raw material,then some sintering additive and pore-forming agent were added to prepare red mud ceramic porous filter.Through controlling preparation process and sintering system,the porosity of the filter was controllable while the crushing strength also strong enough for implement, and the surface property was good enough to surface modify. Based on the filtration performance of the ceramic substrate,some heavy metal ions absorbents were coated on the substrate in order to obtain an environmental rehabilitation material which can absorb heavy metal ions.This environmental rehabilitation material were successfully applied in removing Cu2+,As (V),Cd2+ and Pb2+ from electroplating wastewater.The performances and microstructure of the porous ceramic filtration materials made by red mud were tested by SEM, XRD. The results showed that properties of porous ceramic filtration materials prepared by only sintered red mud (S), only Bayer red mud (B)and both of them were all favorable.The porosity (Pa) was 37.39%, water absorption (Wa) was 20.14%, bulk density (D) was 1.86g/cm3, crushing strength was 15.58MPa, acid resistance was 96.63% and alkali resistance was 99.94%, when the optimal sample BS was fired at 1100℃with 60 wt% total content of red mud in which S:B (sintered red mud to Bayer red mud) was 1:1.The major crystalline phase are a-tridymite (SiO2),hematite (Fe2O3),diopside (CaMgSi2O6).The pore-forming materials dolomite and graphite were added into the optimal sample BS to control the porosity. The porosity (Pa) was 43.77%, water absorption (Wa) was 25.52%, bulk density (D) was 1.72g/cm3, crushing strength was 9.90MPa, acid resistance was 90.00% and alkali resistance was 99.31%, when the optimal sample BS1 was fired at 1100℃with 20 wt% additional content of dolomite added. The porosity (Pa) was 45.37%, water absorption (Wa) was 27.95%, bulk density (D) was 1.62g/cm3, crushing strength was 9.57MPa, acid resistance was 90.69% and alkali resistance was 99.57%, when the optimal sample BS4 was fired at 1100℃with 10 wt% additional content of dolomite added.Chitosan,MnO2 and Eu-Ce co-doped TiO2 were used to modify the surface of red mud porous ceramic substrate,then their absorption properties for Cu2+,Pb2+,Cd2+ and As(V)were studied.The results showed that the removal rate of Cu2+by chitosan modified filter was 95.29%, when 2g chitosan modified filter absorbing in a solution of 6mg/L Cu2+ at pH=5 for120min. The removal rate of As (V) by TiO2 modified filter was 95.96%, when 2g Eu-Ce co-doped TiO2 modified filter absorbing in a solution of 2mg/L As (V) at pH=2 for240min. The removal rate of Pb2+ by MnO2 modified filter was 96.75%, when 2g MnO2 modified filter absorbing in a solution of 2mg/L Pb2+ at pH=7 for120min. The removal rate of Cd2+ by MnO2 modified filter was 96.73%, when 2g MnO2 modified filter absorbing in a solution of 2mg/L Cd2+at pH=7 for120min.Chitosan regeneration experiment, which was soaking chitosan modified filter in hydrochloride for 24h showed that the regeneration rate decreased from 96.70% at the first time to 88.41% at the third time.