Decontamination of Multiple Pollutants from Eutrophic River Water Using Iron-Modification Carbon/zeolite

Zeolite has been increasingly used as a capping material to remove nitrogen (N) and phosphorus (P) released from sediments into the overlying water. However, its removal efficiency varies because of the discrepancy of zeolite types. In this study, the iron-modification carbon/zeolite (MCZ) was synthesized and employed as a capping material to control dissolved oxygen (DO), chemical oxygen demand (CODMn), phosphate (PO43−-P), total phosphorus (TP), ammonium nitrogen (NH4+-N), and total nitrogen (TN) in overlying water from eutrophic river water. The carbon/zeolite was synthesized from coal gasification fine slag and was further modified by ferric sulfate to MCZ. A series of microcosm incubation experiments were performed to determine the removal efficiencies for various pollutants in eutrophic river water. After MCZ capping sediment for 10 days, DO concentration of overlying water increased to 5.59 mg L−1, and turbidity decreased from 20.92 NTU to 8.68 NTU, indicating that capping does not have a significant effect on DO. The removal efficiency of CODMn, PO43−-P, TP, NH4+-N, and TN of overlying water reached 100%, 100%, 89%, 92%, and 57%, respectively; they were 1.6, 1.7, 1.6, and 2.3 times of the natural zeolite (NZ) capping, respectively. The FTIR spectrum showed that most of the absorption peaks of MCZ shifted or weakened after capping sediment for 10 days, and new absorption peaks with wavenumbers of 1065 cm−1 and 1407 cm−1 appeared. The total pollutant removal efficiency of MCZ capping was markedly higher than that of NZ capping, thanks to the higher specific surface area, pore volume, and iron ion of MCZ. Our results suggested that MCZ has the potential to be used as in situ capping materials to simultaneously control multiple pollutants in eutrophic river water.