人工湿地基质对磺胺甲恶唑和六价铬复合污染的吸附性能

Adsorption performance of different substrates to combined sulfamethoxazole and hexavalent chromium pollution in a constructed wetland

为探明能够协同吸附磺胺甲恶唑(Sulfamethoxazole,SMZ)和六价铬[Cr(Ⅵ)]的人工湿地基质种类,以蛭石、沸石、河砂、泥炭、水稻土、高炉渣、硅藻土、火山岩、钾长石和砾石10种基质作为吸附剂,采用批次吸附试验,研究SMZ和Cr(Ⅵ)单吸附和共吸附的吸附动力学、吸附等温线和pH响应变化。结果表明:准二级动力学模型能更好地描述SMZ和Cr(Ⅵ)在基质上的吸附过程(R2≥0.993),同时伴随体积扩散、大孔扩散和微孔扩散三个阶段(Ci>0),SMZ和Cr(Ⅵ)互相削弱了彼此的体积扩散和大孔扩散(P>0.05),降低Cr(Ⅵ)吸附量从0.51~0.97 mg·g^(-1)至0.48~0.49 mg·g^(-1),但增加SMZ吸附量从0.35~0.54 mg·g^(-1)至0.45~0.51 mg·g^(-1),SMZ和Cr(Ⅵ)以水稻土和火山岩动力学聚类变化较大。Freundlich模型能更好地描述SMZ和Cr(Ⅵ)(R2≥0.839)在各基质上的吸附行为,Cr(Ⅵ)对SMZ吸附以促进作用为主,SMZ对Cr(Ⅵ)吸附的影响因基质不同而存在差异,其中SMZ和Cr(Ⅵ)互相促进彼此在钾长石、高炉渣、火山岩、砾石的吸附容量,分别提升10%、10%、21%、25%和166%、71%、104%和658%,吸附等温线聚类变化较大。SMZ和Cr(Ⅵ)在各基质上的吸附量随pH递增而递减,酸性pH下泥炭和火山岩对SMZ和Cr(Ⅵ)的吸附量均高于其他基质,pH响应聚类变化较大。研究表明,钾长石、高炉渣、火山岩、砾石和泥炭有利于SMZ和Cr(Ⅵ)的协同吸附,是人工湿地控制SMZ和Cr(Ⅵ)复合污染的潜在基质。

To discover which substrate types in a constructed wetland can synergistically adsorb sulfamethoxazole(SMZ)and hexavalent chromium[Cr(Ⅵ)],batch adsorption experiments were conducted using 10 substrates as adsorbents(vermiculite,zeolite,river sand,peat,paddy soil,blast furnace slag,diatomite,volcanic rock,K-feldspar,and gravel).Adsorption kinetics,adsorption isotherms,and pH response changes of SMZ and Cr(Ⅵ)were studied in single and binary adsorption experiments.A Pseudo-second order model best described the adsorption process of SMZ and Cr(Ⅵ)on all substrates(R2≥0.993),accompanied with three stages of intraparticle diffusion:volume diffusion,macroporous diffusion,and microporous diffusion(Ci>0).SMZ and Cr(Ⅵ)interactively weakened volume diffusion and macroporous diffusion(P>0.05).The adsorption amount of Cr(Ⅵ)decreased from 0.51-0.97 mg·g^(-1) to 0.48-0.49 mg·g^(-1),but the adsorption amount of SMZ increased from 0.35-0.54 mg·g^(-1) to 0.45-0.51 mg·g^(-1).The kinetics cluster of SMZ and Cr(Ⅵ)in paddy soil and volcanic rock changed more significantly.The Freundlich model well describes the adsorption behavior of SMZ and Cr(Ⅵ)on all substrates(R2≥0.839).Cr(Ⅵ)mainly promoted SMZ adsorption,while SMZ affected Cr(Ⅵ)adsorption depending on the substrate type.Both SMZ and Cr(Ⅵ)mutually promoted adsorption by K-feldspar,blast furnace slag,volcanic rock,and gravel.The adsorption capacity of SMZ on K feldspar,blast furnace slag,volcanic rock,and gravel increased by 10%,10%,21%,and 25%,respectively.The adsorption capacity of Cr(Ⅵ)on K-feldspar,blast furnace slag,volcanic rock,and gravel increased by 166%,71%,104%,and 658%respectively.The isotherms cluster of SMZ and Cr(Ⅵ)in K-feldspar,blast furnace slag,volcanic rock,and gravel changed more significantly.When the pH increased,the adsorption amount of SMZ and Cr(Ⅵ)on each substrate decreased.The adsorption amounts of SMZ and Cr(Ⅵ)on peat and volcanic rock were higher than the others at an acidic pH.The pH response cluster of SMZ and Cr(Ⅵ)in peat and volcanic rock changed more significantly.Our results indicate that K-feldspar,blast furnace slag,volcanic rock,gravel,and peat are conducive to the synergistic adsorption of SMZ and Cr(Ⅵ),and to the control combined of SMZ and Cr(Ⅵ)pollution by constructed wetlands.