A Study Of GAC/ZVI For Removing2-ClBP Removal From Water And Soil

Polychlorinated Biphenyls (PCBs), as a class of persistent organic pollutants (POPs), have caused increasing concerns because of their persistency, direct acute toxicity, high residue, bioaccumulation as well as many ill effects on ecological communities and human health; therefore, remediation of PCBs is a popular subject of environmental research. This study was performed to explore the feasibility and mechanism of removing2-C1BP from water and soil using granular activated carbon (GAC) loaded with nanoscale zero-valent iron (Reactive Activated Carbon or RAC).RAC samples were synthesized by the liquid precipitation method; the GAC carrier and dispersant were optimized. Norit HD3000was selected as the GAC carrier, and0.125g/g polyethylene glycol was employed as the dispersing agent. Nano-scale zero valent iron particles (pore diameter of10-50nm) were successfully loaded on RAC. Batch experiments were conducted for removing2-C1BP from water by RAC samples of varying zero valent iron content. The RAC samples removed2-C1BP from water; after48h of treatment, more than80%of2-C1BP was removed in all test runs. The results of material balance, including the chloride ion release, calculations confirmed the chemical reductive dechlorination of2-C1BP contributing significantly to its overall removal from water. The RAC sample of a low iron content (1.32%) removed the most2-C1BP (54.6%). Increasing zero valent iron content reduced the overall removal rate and dechlorination efficiency; most of the loaded zero valent iron particles occupied a portion of GAC’s internal surface resulting in the lower removal rates. The2-C1BP concentration profiles were adequately described by the pseudo-first-order kinetics model.Batch experiments were also conducted for removing2-C1BP from soil by the RAC samples. The results verified the effectiveness of RAC for removing2-C1BP in soil and that the removal efficiency was all higher than that of the base GAC carrier. In7days, the removal efficiency of the RAC samples (1.32-3.96%iron) removed59.3-63.5%of2-C1BP in soil. The2-C1BP removal from soil was well modeled by the pseudo-first-order reaction kinetics. The results of material balance analyses also confirmed that reductive dechlorination of2-C1BP was a major part of the overall removal. RAC materials were effective for removing2-C1BP from soil;2-C1BP in soil was first absorbed on the inner surface of RAC and then reduced by the loaded nanosaclc zero valent iron particles. The RAC Sample with1.32%-iron content had the highest reductive dechlorination efficiency of2-C1BP (61.6%). Natural organic matter in the soil (SOM) reduced the RAC removal of2-C1BP (30.9%). While the SOM inhibited the migration of2-C1BP from soil to RAC, it served as an electron transfer medium promoting the dechlorination of2-C1BP. The RAC samples prepared from the soft and hard GACs removed about the same amount of2-C1BP; however, the soft GAC may result in faster dechlorination.