摘要
采用镧氢氧化物对天然沸石进行改性,通过实验研究了该镧改性沸石对水中磷酸盐和铵的去除性能,并探讨了相关的去除机制,结果表明,镧改性沸石对水中的磷酸盐和铵具有很好的去除能力。准二级动力学模型适合描述镧改性沸石对水中磷酸盐和铵的吸附过程。镧改性沸石对水中磷酸盐的吸附平衡数据较好地满足了Langmuir等温吸附模型。镧改性沸石对水中铵的吸附平衡数据较好地满足了Langmuir、Freundlich和Dubinin-Radushkevich等温吸附模型。镧改性沸石对水中磷酸盐和铵的去除过程属于自发的、吸热的及熵增加的过程。当pH由3逐渐增加到10时,镧改性沸石对水中磷酸盐的去除能力逐渐下降;当pH由10增加到12时,对磷酸盐的去除能力明显下降。当pH位于3～7时,镧改性沸石对水中铵的去除能力较高;当pH由7逐渐增加到12时,对铵的去除能力逐渐下降。镧改性沸石对水中磷酸盐的去除能力不受离子强度的影响,亦不受共存的Cl-、HCO3-和SO42-等阴离子的影响。镧改性沸石对水中铵的去除能力不受共存的Mg2+的影响,而受共存的Ca2+、Na+和K+的影响较大。镧改性沸石对磷酸盐的吸附机制包括静电吸引作用、配位体交换和路易斯酸碱反应。镧改性沸石去除水中铵的主要机制为阳离子交换作用。
In this study,lanthanum-modified zeolite（LaMZ） was used as an adsorbent to remove phosphate and ammonium from aqueous solution.The effects of various parameters such as adsorbent dosage,solution pH,reaction time,initial adsorbate concentration,temperature,ion strength and coexisting ions on the removal of phosphate and ammonium by LaMZ were investigated using batch experiments.Results showed that LaMZ was effective for the removal of phosphate and ammonium from aqueous solution.The kinetic studies showed that the adsorption of phosphate and ammonium onto LaMZ could be described by a pseudo-second-order kinetic model.The equilibrium adsorption data of phosphate on LaMZ fitted well with the Langmuir isotherm model,and the equilibrium adsorption data of ammonium on LaMZ fitted well with the Langmuir,Freundlich and Dubinin-Radushkevich isotherm models.The thermodynamic studies revealed that the adsorption of phosphate and ammonium on LaMZ was spontaneous and endothermic process.The phosphate adsorption capacity for LaMZ decreased gradually with increasing pH from 3 to 10,but decreased greatly with increasing solution pH from 10 to 12.The ammonium adsorption capacity for LaMZ was relatively high at pH 3-8,but decreased with increasing solution pH from 8 to 12.The presence of coexisting anions such as Cl-,HCO3-and SO42-had negligible influence on phosphate removal by LaMZ.Coexisting Mg2＋ had negligible influence on ammonium removal by LaMZ,but coexisting cations such as K＋,Na＋ and Ca2＋ had negative influence on ammonium removal by LaMZ.The main mechanisms for phosphate removal by LaMZ include electrostatic interaction,ligands exchange and Lewis acid-base interaction depending on solution pH.The main mechanism for ammonium removal by LaMZ is cation exchange.
出处
《上海海洋大学学报》
CAS
CSCD
北大核心
2012年第5期800-808,共9页
Journal of Shanghai Ocean University
基金
国家自然科学基金项目(50908142)
上海市科学技术委员会项目(10230502900)
上海市教育委员会重点学科建设项目(J50702)
上海海洋大学博士启动基金项目(B-5301-11-0202-0219)
长江水环境教育部重点实验室开放课题(YRWEF201107)
关键词
镧改性沸石
磷酸盐
铵
去除
lanthanum-modified zeolite； phosphate； ammonium； removal
