离子强度和pH对针铁矿吸附水溶液中Cd(Ⅱ)的影响
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摘要
探讨了初始浓度、接触时间、pH、离子强度等因素对针铁矿对去除水溶液中Cd(Ⅱ)的影响。利用X射线粉末衍射仪(XRD)对针铁矿进行表征,并通过批量实验研究了针铁矿对Cd(Ⅱ)吸附动力学和等温吸附机理。结果表明:针铁矿比表面积为82. 36 m~2/g;准二级动力学和Langmuir等温吸附适用于针铁矿对Cd(Ⅱ)的吸附,相关系数分别为0. 9535和0. 9915;当25℃、pH为5时,用Langmuir等温线计算得到其最大吸附量为35. 29 mg/g;针铁矿吸附Cd(Ⅱ)能力随pH增大而增大;随着CaCl_2的浓度增大,针铁矿对Cd(Ⅱ)的吸附量减小,随着MgCl_2的浓度增大,针铁矿对Cd(Ⅱ)的吸附量先减小后上升,总体有抑制作用。
The effect of initial aqueous concentration,contact time,p H and ionic strength on Cd( Ⅱ) removal by goethite from aqueous solution were studied. Goethite was characterized by X-ray powder diffraction( XRD). The goethite surface area was determined to be 82. 36 m~2/g. Batch experiments were carried out to determine the adsorption kinetics and isothermal mechanism of Cd( Ⅱ) by goethite. Pseudo-second kinetic equation and Langmuir isotherm were found to fit the experimental data well( r = 0. 9535 and 0. 9915,respectively). The maximum adsorption capacity( Q_m) calculated from Langmuir isotherm was found to be 35. 29 mg/g for Cd( Ⅱ) with p H 5. 0 and 25 ℃. The adsorption process was found to be dependent with p H value. The adsorption capacity of Cd( Ⅱ) increased with the increase of aqueous p H. In CaCl_2 and MgCl_2 solutions,Cd( Ⅱ)adsorption decreased with increasing ionic strength. With the increase of CaCl_2 concentration,the adsorptive capacity of goethite to Cd( Ⅱ) decreased. With the increase of MgCl_2 concentration,the adsorptive capacity of goethite to Cd( Ⅱ)decreased at first,then increased,which had an inhibitory effect generally.
The effect of initial aqueous concentration,contact time,p H and ionic strength on Cd( Ⅱ) removal by goethite from aqueous solution were studied. Goethite was characterized by X-ray powder diffraction( XRD). The goethite surface area was determined to be 82. 36 m~2/g. Batch experiments were carried out to determine the adsorption kinetics and isothermal mechanism of Cd( Ⅱ) by goethite. Pseudo-second kinetic equation and Langmuir isotherm were found to fit the experimental data well( r = 0. 9535 and 0. 9915,respectively). The maximum adsorption capacity( Q_m) calculated from Langmuir isotherm was found to be 35. 29 mg/g for Cd( Ⅱ) with p H 5. 0 and 25 ℃. The adsorption process was found to be dependent with p H value. The adsorption capacity of Cd( Ⅱ) increased with the increase of aqueous p H. In CaCl_2 and MgCl_2 solutions,Cd( Ⅱ)adsorption decreased with increasing ionic strength. With the increase of CaCl_2 concentration,the adsorptive capacity of goethite to Cd( Ⅱ) decreased. With the increase of MgCl_2 concentration,the adsorptive capacity of goethite to Cd( Ⅱ)decreased at first,then increased,which had an inhibitory effect generally.
引文
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[2]宣斌,王济,段志斌,等.铅同位素示踪土壤重金属污染源解析研究进展[J].环境科学与技术,2017(11):17-21.
[3]Wang X S.Cd(Ⅱ)removal by marine arthrobacter protophormiae biomass:mechanism characterization and adsorption performance[J].Desalination and Water Treatment,2013,51(40/42):7710-7720.
[4]Kresge C T,Leonowicz M E,Roth W J,et al.Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism[J].Nature,1992,359:710-712.
[5]Reddad Z,Gerente C,Andres Y,et al.Adsorption of several metal ions onto a low-cost biosorbent:kinetic and equilibrium studies[J].Environmental Science&Technology,2002,36(9):2067-2073.
[6]韩立志,凌瑶,徐霞,等.粉末活性炭对水中重金属离子的吸附性能研究[J].海南师范大学学报(自然科学版),2017,30(1):24-27.
[7]Gupta V K,Agarwal Shilpi,Saleh Tawfik A.Cadmium removal by combining the magnetic properties of iron oxide with adsorption properties of carbon nanotubes[J].Water Research,2011,45(6):2207-2212.
[8]滕洪辉,彭雪,高彬,等.碳材料吸附去除水体中镉离子研究进展[J].水处理技术,2018,44(4):11-16.
[9]马锋锋,赵保卫,刁静茹.小麦秸秆生物炭对水中Cd2+的吸附特性研究[J].中国环境科学,2017,37(2):551-559.
[10]刘慧,朱霞萍,付小君,等.镉在蒙脱石上的吸附解吸动力学与热力学研究[J].矿产综合利用,2013(1):73-77.
[11]朱立超,刘元元,李伟民,等.施氏矿物的化学合成及其对含Ce(Ⅵ)地下水吸附修复[J].环境科学,2017,38(2):629-639.
[12]谢水波,冯敏,杨金辉,等.腐殖酸改性针铁矿对铀U(Ⅵ)的吸附性能及机理研究[J].环境科学学报,2014,34(9):2271-2278.
[13]任天昊,杨琦,李群,等.针铁矿对废水中Cr(Ⅵ)的吸附[J].环境科学与技术,2015,38(增刊2):72-77.
[14]张继义,梁丽萍,蒲丽君,等.小麦秸秆对Cr(Ⅵ)的吸附特性及动力学、热力学分析[J].环境科学研究,2010,23(12):1546-1552.
[15]Leyva-Ramos R,Rangel-Mendez J R,Mendoza-Barron J,et al.Adsorption of cadmium(Ⅱ)from aqueous solution onto activated carbon[J].Water Science and Technology,1997,35(7):205-211.
[16]Obregón-Valencia D,Sun-kou M D R.Comparative cadmium adsorption study on activated carbon prepared from aguaje(Mauritia flexuosa)and olive fruit stones(Olea europaea L.)[J].Journal of Environmental Chemical Engineering,2014,2(4):2280-2288.
[17]Asuquo E,Martin A,Nzerem P,et al.Adsorption of Cd(Ⅱ)and Pb(Ⅱ)ions from aqueous solutions using mesoporous activated carbon adsorbent:equilibrium,kinetics and characterisation studies[J].Journal of Environmental Chemical Engineering,2017,5(1):679-698.
[18]徐楠楠,林大松,徐应明,等.玉米秸秆生物炭对Cd2+的吸附特性及影响因素[J].农业环境科学学报,2014,33(5):958-964.
[19]朱志良,孔令刚,马红梅,等.2种羟基氧化铁对水中Cr(Ⅵ)的吸附性能[J].应用化学,2007,24(8):933-936.
[20]王未平,戴友芝,贾明畅,等.磁性海泡石表面零电荷点和吸附Cd2+的特性[J].环境化学,2012,31(11):1691-1696.
[21]Lehmann J.Bio-energy in the black[J].Frontiers in Ecology and the Environment,2007,5:381-387.
[22]李力,陆宇超,刘娅,等.玉米秸秆生物炭对Cd(Ⅱ)的吸附机理研究[J].农业环境科学学报,2012,31(11):2277-2283.
[23]Filius J D,Lumsdon D G,Meeussen J C L,et al.Adsorption of fulvic acid on goethite[J].Geochimica Cosmochimica Acta,2000,64(1):51-60.