| Coal gangue is a solid waste generated in the process of coal mining and washing,and its long-term accumulation and storage would cause waste of resources,and environmental pollution.Currently,the resource utilization of coal gangue mainly focused on underground filling,combustion to generate power,land reclamation and production of building materials.However,those convention methods have problems including low technical content and low product values.Therefore,it is essential to explore the high-value utilization of coal gangue.Due to the high silicon and aluminum content of coal gangue,it is an ideal raw material for the preparation of polysilicate metal flocculant.This study modified the traditional"roasting-acid leach-alkali dissolution-polymerization"process,to the innovative"roasting-acid leach-polymerization"process to prepare polysilicate aluminum chloride flocculant PASC.The obtained PASC was then applied to treat slime water,and potential flocculation and sedimentation mechanism were investigated.The results are as follows:The influence of different factors on the performance of PASC in the three stages in the"roasting-acid leaching-polymerization"processes was explored,and the optimal preparation conditions were:alkali-ash ratio 0.9 and roasting temperature 900℃.The acid dosage was 1.75g/g,the acid leaching temperature was 49℃,the liquid-solid ratio was 8.9,and the acid leaching time was 2.8 h.The polymerization pH=3.32,the polymerization time was 2.2 h,and the polymerization temperature was 44.3℃.The removal rate of turbidity of slime water by PASC,which was prepared under the previous condition,could reach 99.11%.The comparison of physicochemical properties illustrates that PASC in this study owned a more integrated cluster network structure and a higher degree of polymerization than PASCa that prepared through conventional process,and its flocculation performance to slime water was also better than PASCa.The influence of PASC on flocculation and settlement ability of Tashan slime water was explored through single-factor experiments,and it was concluded that the optimal conditions were dosage of 250 mg/L,pH=10,fast stirring speed of 400 r/min,fast stirring time of 2 min,slow stirring speed of 100 r/min and slow stirring time of 10 min.The turbidity of slime water could be reduced to 2.12 NTU,with 99.74%of removal rate.Moreover,the PASC in this study was compared with other commercial flocculants on the flocculation performance to slime water from different area and the results show that PASC had certain advantages in dosage and turbidity removal than other flocculants,and the turbidity of slime water from four different areas was decreased to 3 NTU after treated by PASC.The physiochemical characterization of PASC shows that it was a new amorphous polymer,with Al-O-Si,Al-OH and other bonding effects.The morphology was a cluster network structure,and its flocculant mechanism included adsorption electrical neutralization,adsorption bridging and net capture sweeping.The hyperbolic model,primary kinetic model and secondary kinetic model were used to fit the process,and the results show that the sedimentation process was well fitted with the second-order kinetic model(R~2>0.95).There are total of 45 figures,11 tables,and 74 references in this dissertation. |
PDF Full Text Request