| 镧改性沸石活性覆盖控制重污染河道底泥溶解性磷酸盐和铵释放研究 |
| 摘要点击 5431 全文点击 1829 投稿时间：2013-03-13 修订日期：2013-05-31 |
| 查看HTML全文
查看全文 查看/发表评论 下载PDF阅读器 |
| 中文关键词 镧改性沸石 底泥 覆盖 磷酸盐 铵 |
| 英文关键词 lanthanum-modified zeolite sediment capping phosphate ammonium |
|
| 中文摘要 |
| 通过实验考察了镧改性沸石对水中磷酸盐和铵的吸附性能,并探讨了低溶解氧情况下镧改性沸石覆盖控制底泥溶解性磷酸盐和铵态氮释放的效率. 镧改性沸石对水中磷酸盐和铵的吸附动力学过程满足准二级动力学模型. 镧改性沸石对水中磷酸盐的吸附平衡数据可以采用Langmuir等温吸附方程加以描述,对水中铵的吸附平衡数据可以采用Langmuir、Freundlich和Dubinin-Radushkevich(D-R)等温吸附方程加以描述. 当pH 7时,镧改性沸石吸附水中磷酸盐的机制包括配位体交换、路易斯酸碱反应和静电吸引,吸附水中铵的机制是阳离子交换. 镧改性沸石覆盖不仅可以有效地控制溶解性磷酸盐从底泥向上覆水的释放,而且可以明显降低铵态氮从底泥向上覆水迁移的速率. 镧改性沸石覆盖量越多,控制底泥铵态氮释放的效果越好. 镧改性沸石覆盖层吸附从底泥中释放出来的溶解性磷酸盐后主要以较为稳定的形态存在,低溶解氧情况下不容易重新释放出来. 上述结果表明,镧改性沸石适合作为一种覆盖材料用于控制低溶解氧情况下溶解性磷酸盐和铵态氮从底泥向上覆水的释放. |
| 英文摘要 |
| The efficiency and mechanism of sediment capping with an active barrier system (ABS) using lanthanum-modified zeolite (LaMZ) to simultaneously prevent phosphate and ammonium release from sediments in heavily polluted river under low dissolved oxygen conditions were investigated using batch and sediment incubation experiments. The adsorption kinetics of phosphate and ammonium on LaMZ followed a pseudo-second-order model. The equilibrium adsorption data of phosphate on LaMZ could be described by the Langmuir isotherm model. The equilibrium adsorption data of ammonium on LaMZ could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The mechanisms for phosphate adsorption onto LaMZ at pH 7 included ligand exchange, Lewis acid-base interaction and electrostatic attraction. The mechanism for ammonium adsorption onto LaMZ at pH 7 was cation exchange. The fluxes of phosphate and ammonium from the sediment to the overlying water were significantly reduced by the ABS using LaMZ under low dissolved oxygen conditions. Higher LaMZ dosage was found to be favorable for the prevention of ammonium release from the sediments using the ABS. Sequential extraction of phosphorus from phosphate-adsorbed LaMZ indicated that most of phosphate immobilized by the ABS using LaMZ was stable and unlikely to be released under low dissolved oxygen conditions. Results of this work indicate that LaMZ is a suitable capping material for preventing phosphate and ammonium release from sediments in heavily polluted river under low dissolved oxygen conditions. |
