不同贝壳粉对镉的吸附特征研究

发布时间：2018-01-28 11:13

本文关键词： 贝壳粉文石方解石吸附含镉污水　出处：《沈阳农业大学》2017年硕士论文　论文类型：学位论文

【摘要】：水资源在我们的生活中至关重要,而我国水资源现状却不容乐观。随着社会的进步和人类活动的影响,大量污水和废弃物排入河流,污染物的量远远的超过水资源的自净能力,导致水体被严重。目前,水体污染中重金属污染最为严重,特别是重金属镉,水体中的镉不仅会对水生生物的生存产生影响,还会因为污水灌溉和蒸腾作用等,进入到农作物中,甚至还会通过食物链进入人体内。目前,针对含镉废水的处理方法包括化学沉淀法、吸附法、离子交换法等。本文主要采用吸附法,以贝壳粉吸附Cd~(2+)为研究内容,通过静态吸附实验研究了时间、温度、初始浓度、pH对贝壳粉吸附镉能力的影响,同时系统比较了不同贝壳粉吸附Cd~(2+)的热力学和动力学特性。研究结果如下:(1)依据XRD衍射图谱供试贝壳粉分为文石型和方解石型两类。蛏子粉、文蛤粉、螃蟹粉、海螺粉、海虹粉、白蚬粉、鲍鱼粉和毛蚶壳粉为文石型;牡蛎粉和扇贝粉为方解石型。(2)静态吸附结果表明,在溶液镉离子浓度为1OOmg·L-1,振荡24小时的室温条件下,文石型贝壳粉对Cd~(2+)的吸附能力显著高于方解石型贝壳粉,而在文石型贝壳中的吸附也存在较大差异,其中海虹和毛蚶壳粉对Cd~(2+)的吸附性能最强。文石型贝壳粉对水溶液中Cd~(2+)的饱和吸附量为145.8mg.kg~(-1)-197.8mg·kg~(-1),方解石型贝壳粉的饱和吸附量为 29.19 mg·kg~(-1)-30.01 mg kg~(-1)。(3)贝壳粉吸附Cd~(2+)分为快速吸附期和饱和期两个时期。溶液的pH值对贝壳粉吸附Cd~(2+)的影响显著,方解石型贝壳粉和文石型贝壳粉二者均在pH值为4.7-5.0时吸附效果最佳,同时,离子浓度的增加会使交换容量增加。(4)分别用Langmuir、Freundlich和Temkin三种模型与拟合的贝壳粉吸附Cd~(2+)的热力学模型相比,发现贝壳粉对水溶液中Cd~(2+)的吸附反应过程为单分子层吸附反应,通过其反应的吉布斯自由能和熵值证明,该反应为放热反应;动力学分为快速吸附和平衡阶段,快速吸附阶段也较好得符合Lagergren准一级动力学模型而吸附全过程符合Ho准二级动力学模型。说明贝壳粉吸附重金属镉并不是单纯的物理吸附。
[Abstract]:Water resources are of great importance in our life, but the present situation of water resources in our country is not optimistic. With the progress of society and the influence of human activities, a great deal of sewage and waste are discharged into rivers. The amount of pollutants is far beyond the self-purification capacity of water resources, resulting in serious water. At present, heavy metal pollution is the most serious in water pollution, especially cadmium. Cadmium in water will not only have an impact on the survival of aquatic organisms, but also because of sewage irrigation and transpiration, into crops, or even through the food chain into the human body. The treatment methods of wastewater containing cadmium include chemical precipitation method, adsorption method, ion exchange method, etc. In this paper, adsorption method and shell powder adsorption of Cd~(2) are used as the research contents. The effects of time, temperature and initial concentration of pH on the adsorption capacity of cadmium from shell powder were studied by static adsorption experiments. At the same time, the thermodynamic and kinetic characteristics of different shell powder adsorbing Cd~(2) were compared systematically. The results are as follows: 1). According to the XRD diffraction pattern, the shell powder was divided into two types: the clonstone type and the calcite type. Clam powder, crab powder, conch powder, sea rainbow powder, white clam powder, abalone powder and clam powder are of the type of wormstone; The static adsorption results of oyster powder and scallop powder are calcite type. The results show that the concentration of cadmium ion in the solution is 1 OOmg 路L -1 and oscillate at room temperature for 24 hours. The adsorptive capacity of Cd~(2 was significantly higher than that of calcite shell powder, and there was a great difference in the adsorption ability between the clondite shell powder and the calcite shell powder. Among them, the adsorption capacity of sea rainbow and clam clam powder to Cd~(2 was the strongest, and the saturated adsorption capacity of aragonite shell powder to Cd~(2 in aqueous solution was 145.8 mg 路kg ~ (-1) 路kg ~ (-1)). (-197.8mg 路kg ~ (-1)). The saturated adsorption capacity of calcite shell powder is 29.19 mg 路kg~(-1)-30.01 mg 路kg ~ (-1) 路L ~ (3)) Cd~(2). The pH value of the solution has a significant effect on the adsorption of Cd~(2 by shell powder. Calcite shell powder and aragonite shell powder both have the best adsorption effect when pH is 4.7-5.0. The exchange capacity increased with the increase of ion concentration. 4) Langmuir was used separately. The Freundlich and Temkin models were compared with the fitted thermodynamic model of shell powder adsorption of Cd~(2. It was found that the adsorption process of shell powder to Cd~(2 in aqueous solution was monolayer adsorption. The Gibbs free energy and entropy of the reaction proved that the reaction was an exothermic reaction. The kinetics can be divided into two stages: rapid adsorption and equilibrium. The rapid adsorption stage also accords with the Lagergren quasi-first-order kinetic model and the whole adsorption process with Ho quasi-second-order kinetic model, which indicates that the adsorption of heavy metal cadmium by shell powder is not a simple physical adsorption.
【学位授予单位】：沈阳农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53

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