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超声-镧改性沸石对富营养水体同步脱氮除磷的研究
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2019/9/11 8:29:38  

摘要:过量的氮磷进入水体会导致水体富营养化,为了同步去除水中的氮磷,本文采用沸石作为吸附原材料,通过对其改性处理,制备出用于同步脱氮除磷的超声-镧改性沸石,并研究其对水体氮磷吸附性能和对底泥氮磷的抑制。本文主要的研究结果如下:

(1)超声-镧改性沸石吸附剂的制备研究

单因素实验表明,最佳超声时间为30min,LaCl3浓度为0.3%,pH为9,浸渍时间为10h时脱氮除磷效果最佳。经过响应面实验优化,超声-镧改性沸石的最佳制备工艺为:超声时间35min,LaCl3浓度为0.34%,pH为8.95。此时,NH4+去除率为94.93%,PO43-去除率为97.41%。

通过表征分析表明,超声-镧改性沸石较原沸石,孔道更加疏松,比表面积增加,且表面负载了一层以La-OH形式负载在沸石表面的白色颗粒,是除磷的主要活性成分;EDS分析证实超声-镧改性沸石表面La含量增大到0.49%;超声-镧改性沸石通过离子交换去除NH4+,羟基作用和化学键力是去除PO43-的主要作用。

(2)超声-镧改性沸石对上覆水体中氮磷吸附性能研究

投加量、pH、温度和振荡时间对氮磷吸附有较大影响,最佳条件为:超声-镧改性沸石投加量为4g/L,pH为7,温度为30℃,振荡时间为180min。在此条件下,超声-镧改性沸石对NH4+和PO43-去除率分别为94.93%和96.84%。溶液中共存阳离子对NH4+竞争吸附影响由强到弱依次为K+>Na+>Ca2+>Mg2+;NO3-、SO42-对PO43-几乎无负面影响,HCO3-、CO32-影响较大;PO43-对超声-镧改性沸石吸附NH4+有微弱的竞争作用,NH4+的存在对PO43-吸附有协同作用,并且竞争作用远远小于协同作用。

超声-镧改性沸石吸附氮磷的过程符合准二级动力学方程和Langmuir等温吸附模型,NH4+和PO43-最大吸附量分别是13.53mg/g和5.45mg/g;热力学实验表明超声-镧改性沸石吸附氮磷是一个自发吸热的过程,自发程度随着温度的升高而增加。

(3)超声-镧改性沸石对底泥氮磷的抑制研究

超声-镧改性沸石覆盖可以有效抑制底泥氮磷的释放。覆盖量越大,对底泥氮磷释放抑制效果越好,当超声-镧改性沸石覆盖量分别为3g,5g和8g时,对底泥NH4+释放的抑制率分别为60.20%,66.86%和82.67%,对底泥PO43-释放的抑制率分别为39.77%,53.05%和69.70%;超声-镧改性沸石对底泥氮磷释放抑制效果随着温度的升高而降低,当温度为15℃、25℃和35℃时,超声-镧改性沸石对底泥NH4+释放的抑制率分别为77.97%,66.89%和60.91%,对底泥PO43-释放的抑制率分别为66.29%,53.05%和43.18%。

Excessive nitrogen and phosphorus can leadto eutrophication of water body. In order to remove nitrogen and phosphorusfrom water simultaneously, zeolite was used as adsorption. Ultrasonic-lanthanummodified zeolite for nitrogen and phosphorus removal was prepared by modifyingthe zeolite.The adsorption of nitrogen and phosphorus in water and theinhibition of nitrogen and phosphorus in sediment were also studied. The mainconclusions were as follows:

(1)The single factor experiment showed thatthe optimum ultrasonic time was 30 min, the concentration of LaCl3 was 0.3%, pHwas 9, and the impregnation time was 10 h. Through the optimization of responsesurface experiment, the optimum preparation technology of ultrasonic-lanthanummodified zeolite was as follows: ultrasonic time was 35min, concentration ofLaCl3 was 0.34%, pH was 8.95. The removal rate of NH4+ and PO43- was 94.93% and97.41% respectively.

The characterization analysis showed thatthe pores of ultrasonic -lanthanum modified zeolite was looser than that of theoriginal zeolites, and the specific surface area was increased, and a layer ofwhite particles loaded on the surface of the zeolites in the form of La-OH wasloaded on the surface of the zeolite, which was the main active component forphosphorus removal. EDS analysis confirmed that the content of La on thesurface of ultrasonic -lanthanum modified zeolite increased to 0.49%.Ultrasonic -lanthanum modified zeolite removed NH4+ by ion exchange. Thehydroxyl interaction and chemical bond force were the main functions ofremoving PO43-.

(2)The optimum conditions were as follows:the dosage of ultrasonic -lanthanum modified zeolite was 4 g/L, the pH was 7,the temperature was 30℃and the oscillation time was 180 min. Under theseconditions, the removal rates of NH4+ and PO43- were 94.93%和96.84%, respectively. The effect of co-existing cations on thecompetitive adsorption of NH4+ was K+> Na+>Ca2+>Mg2+, and NO3- andSO42- had almost no negative effect on PO43-, but HCO3- and CO32- had a greatinfluence on it. PO43- had a weak competitive effect on the adsorption of NH4+ byultrasonic-lanthanum modified zeolite, and the existence of NH4+ had asynergistic effect on the adsorption of PO43-. The competition effect was muchsmaller than that of the synergetic effect.

(3)Ultrasonic-lanthanum modified zeolitescover can effectively inhibit the release of nitrogen and phosphorus fromsediment. When the amount of ultrasonic-lanthanum modified zeolite was 3g, 5gand 8g respectively, the inhibition rate of NH4+ release from sediment was60.20%, 66.86% and 82.67%, respectively. The inhibition rates of PO43- releasefrom sediment were 39.77%, 53.05% and 69.70%, respectively. The inhibitoryeffect of ultrasonic-lanthanum modified zeolite on nitrogen and phosphorusrelease from sediment decreased with increasing temperature.When thetemperature was 15℃, 25℃ and 35℃, the inhibition rate of NH4+ from sediment was77.97%, 66.89% and 60.91%. The inhibition rates of PO43- release from sedimentwere 66.29%, 53.05% and 43.18%, respectively.

关键词:沸石;镧;超声;改性;脱氮除磷

Zeolite; Lanthanum; Ultrasonic; Modified;Nitrogen and phosphorus removal

上一篇:聚酰亚胺基复合光催化剂的制备及用于降解水中有机染料性能研究     下一篇:狐尾藻腐解释放胡敏酸的特性及对沉水植物生长的影响
 
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