Application of synthetic iron-oxide coated zeolite for the pollution control of river sediments

Contaminants released from river sediments are catching more attentions for river environmental management, especially when external sources of river pollution have been well controlled. To reduce the contaminant release from sediments, in-situ capping is often applied because of its effective reduction of contaminant flux and minimal disturbance to the surroundings. As an innovative sediment capping material, iron-oxide coated zeolite (IOCZ) was synthesized, characterized, and evaluated in this study. Its performance for the NH₄⁺-N, PO₄^3--P, and S^2--S fixation in aqueous solutions was evaluated using batch and fixed-bed column experiments. IOCZ was found effective as a sorbent for NH₄⁺-N, PO₄^3--P, and S^2--S with the maximum Langmuir sorption capacities of 6.23 mg N g^-1, 0.966 mg P g^-1, and 1.70 mg S g^-1, respectively. Under the studied conditions, the whole breakthrough process in the fixed-bed column could be well described by Thomas model, indicating IOCZ can effectively retard NH₄⁺-N, PO₄^3--P, and S^2--S under flowing conditions. In addition, desorption simulative experiments suggested that the retarded pollutants were stable even under some extreme environments such as flooding or tiding. Therefore, IOCZ seems a promising capping material to control the release of NH₄⁺-N, H₂PO₄^--P, and S^2--S from river sediments.