引用本文:张康,戴亮,赵伟繁,等.污泥腐殖酸对Cd2+的吸附特性[J].环境科学研究,2020,33(6):1459-1468.
ZHANG Kang,DAI Liang,ZHAO Weifan,et al.Adsorption Properties of Sludge-Based Humic Acid to Cd2+[J].Research of Environmental Sciences,2020,33(6):1459-1468.]
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污泥腐殖酸对Cd2+的吸附特性
张康, 戴亮, 赵伟繁, 王刚, 未碧贵, 任珺
兰州交通大学环境与市政工程学院, 甘肃 兰州 730070
摘要:
为了促进污水处理厂剩余污泥的资源化利用,探索S-HA(sludge-based humic acid,污泥腐殖酸)对溶液中重金属Cd2+的吸附特性.采用国际腐殖酸协会(IHSS)推荐的方法提取S-HA,通过元素分析、FT-IR(傅里叶红外光谱分析)和SEM-EDS(外观形态分析)等方法,考察溶液pH和共存阳离子对吸附过程的影响,并对吸附过程分别进行了吸附动力学模型、等温吸附模型和吸附热力学模型拟合,同时通过对比S-HA吸附前后的红外光谱和扫描电镜-能谱图片,探索S-HA对Cd2+的吸附机制.结果表明:①S-HA表面呈松散的簇团状,含有大量的羧基、醇羟基和酚羟基等含氧官能团,芳香度较高,含有较多的脂肪链结构;S-HA在吸附水中Cd2+的过程中,Cd2+与S-HA表面上的酚羟基、羧基等官能团发生了络合作用.②S-HA对Cd2+的吸附量随溶液pH升高而增加,溶液中Na+、NH4+和Ca2+等共存阳离子的存在不利于S-HA对Cd2+的吸附,其中Ca2+的存在对S-HA吸附Cd2+影响最大.③S-HA对Cd2+的吸附由快吸附、慢吸附和吸附平衡3个阶段组成,吸附平衡时间为12 h;吸附过程符合准二级动力学模型,其整体吸附速度由液膜扩散和颗粒内扩散共同控制;吸附等温线符合Freundlich等温吸附模型,25℃下的最大吸附量为19.29 mg/g,Cd2+在S-HA上的吸附是自发吸热反应.研究显示:污水处理厂剩余污泥提取的S-HA对Cd2+具有较好的吸附效果;S-HA对Cd2+的吸附过程同时存在着物理吸附和化学吸附;高pH对S-HA吸附Cd2+有促进作用,而高离子强度对S-HA吸附Cd2+有抑制作用.
关键词:  污泥  腐殖酸  吸附  Cd2+
DOI:10.13198/j.issn.1001-6929.2020.04.14
分类号:X703.5
基金项目:国家自然科学基金项目(No.51668034,31560234);甘肃省教育厅高等学校创新能力提升项目(No.2019B-051)
Adsorption Properties of Sludge-Based Humic Acid to Cd2+
ZHANG Kang, DAI Liang, ZHAO Weifan, WANG Gang, WEI Bigui, REN Jun
School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
Abstract:
In order to promote the resource utilization of excess sludge in sewage treatment plants, the adsorption characteristics of sludge-based humic acid (S-HA) to Cd2+ were explored. S-HA was extracted using the method recommended by International Humic Substances Society (IHSS). The S-HA was characterized by elemental analysis, infrared spectroscopic analysis and morphology analysis. The effects of solution pH and coexisting cations on Cd2+ adsorption were investigated. The adsorption process was fitted with adsorption kinetic model, isothermal adsorption model and adsorption thermodynamic model. Meanwhile, the adsorption mechanism of Cd2+ on S-HA was explored by comparing the infrared spectra and the images and results of scanning electron microscopy-energy dispersive X-ray analysis before and after Cd2+ adsorption on S-HA. The results showed that: (1) The surface of S-HA was loose cluster, containing a large number of oxygenic functional groups, such as carboxyl groups, alcoholic hydroxyl groups and phenolic hydroxyl groups, with a high degree of aromaticity and more fatty chain structure; Cd2+complexed with phenolic groups and carboxyl groups on the surface of S-HA. (2) As the pH increased, the adsorption of Cd2+ on S-HA increased gradually. The presence of co-existing cations such as Na+, NH4+ and Ca2+ in solution was adverse to the adsorption of Cd2+ by S-HA, and Ca2+ had the greatest effect on the adsorption of Cd2+ by S-HA. (3) The adsorption process of Cd2+ by S-HA included three stages: fast adsorption, slow adsorption and adsorption equilibrium, and the adsorption equilibrium time was 12h. The adsorption process was fitted by the pseudo-second order kinetic model, and the overall adsorption rate was controlled by both liquid membrane diffusion and intra-particle diffusion. The adsorption isotherm agreed with the Freundlich isothermal adsorption model, with a maximum adsorption capacity of 19.29 mg/g at 25 ℃. The adsorption of Cd2+ on S-HA was a spontaneous endothermic reaction. The results show that the S-HA extracted from the sludge of the sewage treatment plant had a good adsorption effect on Cd2+. The comprehensive analysis of adsorption kinetics and thermodynamics indicated that both physical adsorption and chemical adsorption existed in the adsorption process of Cd2+ by S-HA. High pH promoted the adsorption of Cd2+ by S-HA, while high ionic strength inhibited adsorption.
Key words:  sludge  humic acid  adsorption  Cd2+