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| Releases of Ammonium and Phosphorus from River Sediments Capped with Zirconium-Modified Zeolite |
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| KeyWord:sediment; zirconium-modified zeolite; active capping; nitrogen and phosphorus; release; control |
| Author Name | Affiliation | | YANG Meng-juan | College of Marine Science, Shanghai Ocean University, Shanghai 201306, China | | LIN Jian-wei | College of Marine Science, Shanghai Ocean University, Shanghai 201306, China | | ZHAN Yan-hui | College of Marine Science, Shanghai Ocean University, Shanghai 201306, China | | WANG Chun-feng | College of Marine Science, Shanghai Ocean University, Shanghai 201306, China | | CHU Ming | College of Marine Science, Shanghai Ocean University, Shanghai 201306, China | | LI Jia | College of Marine Science, Shanghai Ocean University, Shanghai 201306, China | | ZHENG Wen-jing | College of Marine Science, Shanghai Ocean University, Shanghai 201306, China | | FANG Qiao | College of Marine Science, Shanghai Ocean University, Shanghai 201306, China |
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| Abstract: |
| Nitrogen and phosphorus releases from river sediments greatly impact the quality of river water. So far there is still lack of effective means to reduce their releases. Batch and sediment incubation experiments were carried out to examine the efficiency and mechanism of zirconium-modified zeolite（ZrMZ） to reduce phosphate and ammonium releases from the sediments from heavily polluted river after capping with ZrMZ. Phosphate adsorption capacity by ZrMZ decreased with increasing pH. Ammonium adsorption capacity by ZrMZ increased slightly from pH 4 until 8, but decreased from pH 8 to 10. The adsorption kinetics of phosphate and ammonium on ZrMZ was found to follow a pseudo-second-order model. The equilibrium adsorption data of phosphate and ammonium on ZrMZ could be described by the Langmuir and Freundlich isotherm models. The maximum adsorption capacity of phosphate and ammonium on ZrMZ derived from the Langmuir isotherm model was 7.75 mg·g-1 and 9.59 mg·g-1 at pH 7 and 25 ℃, respectively. The removal efficiency of phosphate and ammonium by ZrMZ increased with adsorbent dosage. Phosphate adsorption onto ZrMZ was mainly via ligand exchange, while ammonium adsorption through cation exchange. About 82.5% of phosphate adsorbed onto ZrMZ existed as NaOH-P（Phosphorus extracted by NaOH） form, and was relatively stable and unlikely to be released under low dissolved oxygen conditions. Of total phosphorus adsorbed onto ZrMZ, percentages of water-soluble phosphorus（WSP）, readily desorbable phosphorus（RDP）, and NaHCO3 extractable phosphorus（Olsen-P） were very low and algal available phosphorus（AAP） accounted for only 29%. Capping sediments with ZrMZ not only prevents PO3-4-P and NH+4-N releases from the sediments, but significantly reduces PO3-4-P and NH+4-N concentrations in the overlying water. |
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