| Permeable reactive barrier (PRB) as an in situ method for contaminated underground water remediation is popular subject and commercialization application in developed countries. Due to its advantages of good long-term performance, high cost-performance and easy installation, the PRB technology has attracted much attention during the last decade in China. With the further research, some abroad literatures showed that PRB is applied in contaminated underground water remediation, while there are few reports in our country. On the base of the research domestic and abroad, combined steel slag and fly ash as selected materials into geopolymer, to prepare reactive reaction medium of PRB and constructed simulation system for COD, NH4+-N, PO4-P, Pb2+ and Cd2+ removal in surface water.Steel slag was modified by calcination with Al(OH)3 as additive. The optimal conditions are:calcination temperature is 700 ℃, steel slag:Al (OH) 3=5:1 (m/m). SEM、 XRD and FITR analysis indicated the surface structure of modified steel slag is broken to become rough and porous, RO phase and amorphous form increased while C3S decreased. A systematic study on adsorption performance on tipical pulluntants by modified steel slag in single and multiple system were conducted. The experimental results showed that modified steel slag has a high selectivity to PO4-P in COD--NH4+-N--PO4-P system and the removal of PO4-P is 93%. The modified steel slag has a good treatment performance on Pb2+and Cd2+ in Pb2+-Cd2+ systems and the removal of Pb24 and Cd2+ are 97% and 94%, respectively. The adsorption parameters, the order of kinetic reaction and control steps of adsorption rate were obtained by equilibrium and kinetic studies.The adsorption process is the result of various forces that determined by charactors of polluntants and solution pH.Fly ash was modified by hydrothermal with NaOH solution. The optimal conditions are: fly ash:NaOH=4:1 (m/m), CTMAB solution is 2%(w/w), reaction temperature is 100℃, reaction time is 6h. SEM、XRD and FITR analysis indicated the surface structure of modified fly ash is broken to become rough and porous, and propinquity zeolite was generated. A systematic study on adsorption performance on tipical pulluntants by modified fly ash in single and multiple systems were conducted. The experimental results showed that modified fly ash has a high selectivity to COD and NH4+-N in COD--NH4+-N--PO4-P system and the removal of COD and NH4+-N are 88% and 84%, respectively. The modified fly ash has a good treatment performance on Pb2+ and Cd2+ in Pb2+-Cd2+ systems and the removal of Pb2+ and Cd2+ are 91% and 89%. The adsorption parameters, the order of kinetic reaction and control steps of adsorption rate were obtained by equilibrium and kinetic studies.The adsorption process is the result of various forces that determined by charactors of polluntants and solution pH.Porous geoplomer materials prepared from steel slag and fly ash under alkali solution. The optimal condition are:fly ash:steel slag=1:1 (m/m), modulus of sodium silicate is 1.5, both aluminite powder and CTMAB are 1% (m/m). SEM、XRD and FITR analysis indicated the geopolymer are generated. The sample has character of good compressive strength (2.9 MPa) and permeation coefficient (0.35mm/s), and removal of COD, NH4+-N, PO4-P, Pb2+ and Cd2+ are 78%,74%,82%,95% and 91%, respectively.Building PRB system with modified steel slag and modified fly ash as filler in middle, and porous geoplomer materials as barrier on either hand. Treatment performance on tipical polluntants of simulated Fenhe River was tested. The results showed that the system has good tolerance and stalblity.The removal of COD, NH4+-N, PO4-P, Pb2+ and Cd2+reach to be the highest of 77%,82%,93%,96% and 92% on the 8th day, respectively. And then, the removal were 68%,69%,83%,84% and 81% on the 32th day, respectively. In addition, hydraulic loading and the amount of modified fly ash have influence on treatment performance and stability of system. Over all, the PRB system has good performance and low-cost, which not only expand utilization of surface water treatment but also realize treatment of wastes with processes of wastes against one another. |
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