硅铝比对分子筛吸附氨氮性能的影响
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摘要
基于X射线荧光光谱法确定的4种ZSM5分子筛硅铝比,分析了不同硅铝比分子筛吸附氨氮性能的差异,结合扫描电镜、X射线衍射分析结果,从分子筛的骨架组成、表面形貌和晶体结构角度,考察了硅铝比对分子筛吸附氨氮性能的影响机制;并探讨了分子筛骨架脱硅对其吸附性能的改善作用,为分子筛应用于污水厂尾水深度脱氮提供技术参考.结果表明,不同硅铝比分子筛的表面形貌、晶体结构与吸附氨氮性能具有显著差异:随着分子筛硅铝比增加,其结晶度下降、晶粒形态逐渐模糊、吸附容量降低;当实际硅铝比由35增大至237时,氨氮平衡吸附量由5.65mg/g降至0.41mg/g,由Langmuir吸附等温式确定的饱和吸附量由6.5963mg/g下降至0.4430mg/g.分子筛吸附过程符合准二级动力学模型,吸附速率受离子交换化学吸附作用机理控制,随着硅铝比升高分子筛的离子交换容量下降,其吸附速率降低.分子筛骨架脱硅能够显著改善其氨氮吸附性能,硅铝比为35的分子筛经碱蚀脱硅处理后,其氨氮平衡吸附量提高81.6%,该方法为改善分子筛吸附性能提供了一种有效的技术途径.
This study examined the difference of ammonium adsorption by molecular sieve with different silica-alumina ratios that were determined using x-rays fluorescence(XRF) method. Based on the results from scanning electron microscopy(SEM) and X-ray diffraction(XRF), It was investigated the adsorption mechanism of molecular sieve under different silica-alumina ratio conditions from the perspective of molecular sieve framework, surface morphology, and crystal structure. Meanwhile, the ammonium adsorption improvement through the desilicification of molecular sieve framework was revealed, and this would provide technical reference for the molecular sieve based deep denitrification of sewage treatment plant effluent. The results indicated that molecular sieves with different silica-alumina ratio had significant variation in surface morphology, crystal structure, and ammonium adsorption performance. It was found that the increased silica-alumina ratio was associated with decreased crystallization, increased obscuring of crystal grain shape, and decreased adsorption capacity. When the silica-alumina ratio rose from 35 to 237, the equilibrium adsorption capacity of ammonium by molecular sieve decreased from 5.65mg/g to 0.41mg/g, and the monolayer adsorption saturation capacity confirmed by Langmuir adsorption isotherm decreased from 6.5963mg/g to 0.4430mg/g. The adsorption process conformed to the pseudo-second-order kinetic model, which was revealed that the adsorption rate was controlled by the mechanism of ion-exchange chemical adsorption. Both the ion-exchange capacity of molecular sieve and the rate of adsorption decreased with the increase in silica-alumina ratio. It was observed that the ability of ammonium absorption was significantly improved by desilicification process of molecular sieve framework, and the equilibrium ammonium adsorption with a silica-alumina ratio of 35 increased by 81.6% after a desilicification process. This would provide an effective technological approach for improving the ammonium adsorption by molecular sieve.
This study examined the difference of ammonium adsorption by molecular sieve with different silica-alumina ratios that were determined using x-rays fluorescence(XRF) method. Based on the results from scanning electron microscopy(SEM) and X-ray diffraction(XRF), It was investigated the adsorption mechanism of molecular sieve under different silica-alumina ratio conditions from the perspective of molecular sieve framework, surface morphology, and crystal structure. Meanwhile, the ammonium adsorption improvement through the desilicification of molecular sieve framework was revealed, and this would provide technical reference for the molecular sieve based deep denitrification of sewage treatment plant effluent. The results indicated that molecular sieves with different silica-alumina ratio had significant variation in surface morphology, crystal structure, and ammonium adsorption performance. It was found that the increased silica-alumina ratio was associated with decreased crystallization, increased obscuring of crystal grain shape, and decreased adsorption capacity. When the silica-alumina ratio rose from 35 to 237, the equilibrium adsorption capacity of ammonium by molecular sieve decreased from 5.65mg/g to 0.41mg/g, and the monolayer adsorption saturation capacity confirmed by Langmuir adsorption isotherm decreased from 6.5963mg/g to 0.4430mg/g. The adsorption process conformed to the pseudo-second-order kinetic model, which was revealed that the adsorption rate was controlled by the mechanism of ion-exchange chemical adsorption. Both the ion-exchange capacity of molecular sieve and the rate of adsorption decreased with the increase in silica-alumina ratio. It was observed that the ability of ammonium absorption was significantly improved by desilicification process of molecular sieve framework, and the equilibrium ammonium adsorption with a silica-alumina ratio of 35 increased by 81.6% after a desilicification process. This would provide an effective technological approach for improving the ammonium adsorption by molecular sieve.
引文
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[15]晋晓彤,鄢国平,纪娜,等.粉煤灰合成分子筛的研究进展[J].环境化学,2015,34(11):2025-2038.Jin X T,Yan G P,Ji N,et al.Synthesis of zeolite from coal fly ash,[J].Environmental Chemistry,2015,34(11):2025-2038.
[16]任根宽.用煤矸石合成4A沸石分子筛处理氨氮废水[J].环境工程学报,2014,8(4):1533-1538.Ren G K.Removal of ammonia-nitrogen in wastewater with 4Azeolite molecular sieve synthesized from coal gangue,[J].Chinese Journal of Environmental Engineering,2014,8(4):1533-1538.
[17]任瑞霞,刘姝,宋雯雯,等.ZSM-5分子筛的合成与应用,[J].化工科技,2011,19(1):55-60.Ren R X,Liu S,Song W W,et al.Research advance on the synthesis and application of ZSM-5 zeolite[J].Science&Technology in Chemical Industry,2011,19(1):55-60.
[18]王芳.4A分子筛改性催化剂制备及其吸附氨氮的性能,[J].应用化工,2015,(2):250-253.Wang F.Preparation of modified 4A molecular sieve and performance for ammonia adsorption,[J].Applied Chemical Industry,2015,(2):250-253.
[19]张群.POSS改性介孔分子筛去除饮用水中氨氮的研究,[D].哈尔滨:哈尔滨工业大学,2010.Zhang Q.Research on POSS-modified mesoporous and removing amonion nitrogen in drinking water,[D].Harbin,Harbin Institute of Technology,2010.
[20]杨哲,庆承松,陈冬,等.磁性4A分子筛的制备及其对氨氮的吸附动力学研究,[J].岩石矿物学杂志,2013,32(6):935-940.Yang Z,Qing Z S,Chen D,et al.Adsorption kinetic behavior of magnetic zeolite 4A for ammonia nitrogen,[J].Acta Petrologica et Mineralogica,2013,32(6):935-940.
[21]国家环境保护总局,水和废水监测分析方法编委会水和废水监测分析方法,[M].北京:中国环境科学出版社,2002:254-256.State Environmental Protection Administration of China.Water and waste water monitoring and analysis method,[M].Beijing:China Environmental Science Press,2002:254-256.
[22]刘明光,郭虎森.粉末衍射文件(PDF)的简况与使用,[J].现代仪器与医疗,2002,(2):44-47.Liu M G,Guo H S.The synopsis and application of retrieval of powder diffraction file(PDF),[J].Modern Instruments&Medical Treatment,2002,(2):44-47.
[23]张健,万东锦,朱云云,等.两种ZSM-5沸石分子筛吸附水中氨氮的研究,[J].环境科学与技术,2011,34(8):104-108.Zhang J,Wan D J,Zhu Y Y,et al.Adsorption of NH4+-N from aqueous solution by two kinds of ZSM-5 molecular sieve[J].Environmental Science&Technology,2011,34(8):104-108.
[24]王潇潇,郭少青,张伟,等.SAPO-11分子筛合成条件对其结晶度与催化性能的影响,[J].分子催化,2013,27(4):295-306.Wang X X,Guo S Q,Zhang W,et al.Effect of synthesis conditions on the crystallinity and catalytic performances of SAPO-11 molecular sieves[J].Journal of Molecular Catalysis,2013,27(4):295-306.
[25]杜夏梅,谷迎秋,秦菲,等.丝光沸石硅铝比对骨架脱硅衍生介孔结构的影响,[J].硅酸盐通报,2013,32(10):2108-2113.Du X M,Gu Y Q,Qin F,et al.Effect of MOR Si/Al Ratio on the Mesopore Structure Formed by Framework Desilication,[J].Bulletin of the Chinese Ceramic Society,2013,32(10):2108-2113.
[26]谷迎秋,李勇,秦菲,等.丝光沸石骨架脱硅与介孔改性研究,[J].当代化工,2013,42(7):893-896.Gu Y Q,Li Y,Qin F,et al.Mesopore modification of MOR zeolites via desilication of framework[J].Contemporary Chemical Industry,2013,42(7):893-896.
[2]Kermani M,Bina B,Movahedian H,et al.Biological phosphorus and nitrogen removal from wastewater using moving bed biofilm process[J].Iranian Journal of Biotechnology,2009,7(1):19-27.
[3]Li W J,Li J,Zhang Y Z,et al.Adsorption mechanism of ammonium from aqueous solutions by NaCl modified zeolite[J].China Environmental Science,2016,36(12):3567-3575.
[4]Zhang X Y,Wu Z C,Wang Z W,et al.Adsorption characteristics of ammonium ions by natural clinoptilolite powder[J].China Environmental Science,2010,30(5):609-614.
[5]Nie N,Ding Y Z,Li X Q,et al.Preparation of zeolite and zero valent iron composite for cleanup of hexavalent contamination in water[J].China Environmental Science,2013,33(3):443-447.
[6]沈志强,牟锐,李元志,等.人工湿地生物沸石快速吸附-再生性能与再生机理研究[J].环境科学学报,2015,36(4):1242-1247.Shen Z Q,Mou R,Li Y Z,et al.Study on the rapid adsorptionregeneration performance of bio-zeolite and its regeneration mechanism an a constructed wetland[J].Acta Scientiae Circumstantiae,2015,36(4):1242-1247.
[7]王文超,管俊芳,严春杰,等.斜发沸石处理氨氮废水,[J].环境工程学报,2014,8(3):1036-1040.Wang W C,Guan J F,Yan C J,et al.Adsorption of ammoniumnitrogen in wastewater by clinoptilolite[J].Chinese Journal of Environmental Engineering,2014,8(3):1036-1040.
[8]Wu P,Lu S J,Xu L Z,et al.Efficiency and mechanism of nitrogen and phosphorus removal in modified zeolite wetland[J].Environmental Science,2017,38(2):580-588.
[9]Lin J W,Zhan Y H,Lu X.Adsorption of phosphate and ammonium from aqueous solution on zirconium modified zeolite[J].China Environmental Science,2012,32(11):2023-2031.
[10]佘振宝,宋乃忠.沸石加工与应用,[M].北京:化学工业出版社,2013:65-67.She Z B,Song N Z.Processing and application of zeolite[M].Beijing:Chemical Industry Press,2013:65-67.
[11]王春燕,周集体,何俊慷,等.A型分子筛的合成及其对镉离子的吸附性能,[J].催化学报,2012,V33(11):1862-1869.Wang C Y,Zhou J T,He J K,et al.Synthesis of zeolite A and its application as a high-capacity cadmium ion exchanger[J].Chinese Journal of Catalysis 2012,V33(11):1862-1869.
[12]陈建涛,马丽萍,资泽城,等.5A分子筛的改性制备及其对汞的吸附研究,[J].硅酸盐通报,2014,33(9):2164-2169.Chen J T,Ma L P,Zi Z C,et al.Study on the Preparation of modified5A molecular sieve and its adsorption of mercury[J].Bulletin of the Chinese Ceramic Society,2014,33(9):2164-2169.
[13]李曦同,徐海红,朱文杰,等.巯基修饰MCM-41分子筛的制备及其对Cr(Ⅵ)的吸附动力学,[J].环境工程学报,2015,9(5):2199-2206.Li X T,Xu H H,Zhu W J,et al.Synthesis of SH-MCM-41and its adsorption kinetics to Cr(VI)[J].Chinese Journal of Environmental Engineering,2015,9(5):2199-2206.
[14]Li Y,Sun H M,Wang Y H,et al.Green routes for synthesis of zeolites[J].Progress In Chemistry,2015,27(5):503-510.
[15]晋晓彤,鄢国平,纪娜,等.粉煤灰合成分子筛的研究进展[J].环境化学,2015,34(11):2025-2038.Jin X T,Yan G P,Ji N,et al.Synthesis of zeolite from coal fly ash,[J].Environmental Chemistry,2015,34(11):2025-2038.
[16]任根宽.用煤矸石合成4A沸石分子筛处理氨氮废水[J].环境工程学报,2014,8(4):1533-1538.Ren G K.Removal of ammonia-nitrogen in wastewater with 4Azeolite molecular sieve synthesized from coal gangue,[J].Chinese Journal of Environmental Engineering,2014,8(4):1533-1538.
[17]任瑞霞,刘姝,宋雯雯,等.ZSM-5分子筛的合成与应用,[J].化工科技,2011,19(1):55-60.Ren R X,Liu S,Song W W,et al.Research advance on the synthesis and application of ZSM-5 zeolite[J].Science&Technology in Chemical Industry,2011,19(1):55-60.
[18]王芳.4A分子筛改性催化剂制备及其吸附氨氮的性能,[J].应用化工,2015,(2):250-253.Wang F.Preparation of modified 4A molecular sieve and performance for ammonia adsorption,[J].Applied Chemical Industry,2015,(2):250-253.
[19]张群.POSS改性介孔分子筛去除饮用水中氨氮的研究,[D].哈尔滨:哈尔滨工业大学,2010.Zhang Q.Research on POSS-modified mesoporous and removing amonion nitrogen in drinking water,[D].Harbin,Harbin Institute of Technology,2010.
[20]杨哲,庆承松,陈冬,等.磁性4A分子筛的制备及其对氨氮的吸附动力学研究,[J].岩石矿物学杂志,2013,32(6):935-940.Yang Z,Qing Z S,Chen D,et al.Adsorption kinetic behavior of magnetic zeolite 4A for ammonia nitrogen,[J].Acta Petrologica et Mineralogica,2013,32(6):935-940.
[21]国家环境保护总局,水和废水监测分析方法编委会水和废水监测分析方法,[M].北京:中国环境科学出版社,2002:254-256.State Environmental Protection Administration of China.Water and waste water monitoring and analysis method,[M].Beijing:China Environmental Science Press,2002:254-256.
[22]刘明光,郭虎森.粉末衍射文件(PDF)的简况与使用,[J].现代仪器与医疗,2002,(2):44-47.Liu M G,Guo H S.The synopsis and application of retrieval of powder diffraction file(PDF),[J].Modern Instruments&Medical Treatment,2002,(2):44-47.
[23]张健,万东锦,朱云云,等.两种ZSM-5沸石分子筛吸附水中氨氮的研究,[J].环境科学与技术,2011,34(8):104-108.Zhang J,Wan D J,Zhu Y Y,et al.Adsorption of NH4+-N from aqueous solution by two kinds of ZSM-5 molecular sieve[J].Environmental Science&Technology,2011,34(8):104-108.
[24]王潇潇,郭少青,张伟,等.SAPO-11分子筛合成条件对其结晶度与催化性能的影响,[J].分子催化,2013,27(4):295-306.Wang X X,Guo S Q,Zhang W,et al.Effect of synthesis conditions on the crystallinity and catalytic performances of SAPO-11 molecular sieves[J].Journal of Molecular Catalysis,2013,27(4):295-306.
[25]杜夏梅,谷迎秋,秦菲,等.丝光沸石硅铝比对骨架脱硅衍生介孔结构的影响,[J].硅酸盐通报,2013,32(10):2108-2113.Du X M,Gu Y Q,Qin F,et al.Effect of MOR Si/Al Ratio on the Mesopore Structure Formed by Framework Desilication,[J].Bulletin of the Chinese Ceramic Society,2013,32(10):2108-2113.
[26]谷迎秋,李勇,秦菲,等.丝光沸石骨架脱硅与介孔改性研究,[J].当代化工,2013,42(7):893-896.Gu Y Q,Li Y,Qin F,et al.Mesopore modification of MOR zeolites via desilication of framework[J].Contemporary Chemical Industry,2013,42(7):893-896.