磁性炭化谷壳对水体中砷的去除效果及机理研究

发布时间：2019-01-24 21:47

【摘要】：近年来,有不少利用生物炭作为一种新型的吸附材料去除各种重金属污染土壤和水体方面的研究,但针对含砷废水的生物炭去除研究还鲜有报道。本研究以谷壳为原料,通过不同温度缺氧高温热解制备出5种炭化谷壳,并通过酸、碱改性后筛选出吸附效果最好的一种炭化谷壳,将其进行磁性负载,获得另一种新型的负载纳米Fe3O4的炭化谷壳(CRH-I)。研究CRH-I的吸附时间、pH、添加量这三个因素对吸附的影响；通过吸附动力学、等温吸附探讨其吸附特性。同时,了解CRH-I吸附解吸能力和针对实际含砷废水去除能力。从BET比表面积、孔径结构分析、SEM、XRD、FTIR几个方面对CRH-I进行表征分析及机理研究。主要研究结果如下：(1)通过对As(Ⅴ)吸附性能筛选结果可知,CaO改性的炭化谷壳,使得炭化谷壳得到了活化,溶液中As(Ⅴ)去除率比较高。CRHCaO600的吸附效果最佳,去除率最高达到82%。将筛选出的CRHCaO600进行磁性负载,成功合成新型炭化谷壳CRH-I。(2)吸附实验表明,刚开始吸附速率较快,随着时间推移,速率逐渐下降,8h时,CRH-I对As(Ⅴ)吸附已几乎达到饱和状态,吸附达到平衡。相对CRHCaO600而言,CRH-I对As(Ⅴ)的去除率明显提高。随着溶液pH值降低,CRH-I对As(Ⅴ)的去除率逐渐升高,pH=2时的去除率高达98.3%；当pH=11时,去除率只有63.7%。CRH-I吸附反应满足准动力学二级方程,相关系数为R2=0.999；在不同温度下,将CRH-I对As(Ⅴ)的吸附验数据进行Langmuir方程和Freundlich等温方程拟合,结果更符合Langmuir方程；在25℃时,相关系数R2=0.985。通过吸附热力学分析表明,该吸附过程是自发进行的,且低温更有利于吸附的进行。(3)通过吸附解吸实验可以得知,5次吸附解吸的去除率分别为83.2%、66.4%、65.6%、67.2%、64.0%。由此可以看出,第一次吸附解吸后CRH-I对As(Ⅴ)的去除率仍然是很高的,从第二次以后CRH-I对As(Ⅴ)的去除率开始降低,但是保持一个较稳定的去除率,说明CRH-I依然具备良好的吸附性能,且再生吸附性能稳定。(4)经过对比表面积进行表征分析发现,CRH-I相较CRH600的BET比表面积增大约30%,达到182m2·g-1,微比表面积和微孔体积都扩大了6倍左右。XRD检测结果可知,吸附过程没有新的晶体产生,CRH-Ⅰ吸附As(V)为表面吸附。FTIR分析结果表明,相比CRH600,CRH-Ⅰ分子间的羧基和酚羟基官能团有所增加,产生了芳构化反应和脂肪醚类物质。(5)通过对实际废水进行预处理和添加CRH-Ⅰ相结合的处理方法,在CRH-Ⅰ添加量为2 g、固液比为1：200时,出水As(Ⅲ)、As(V)浓度分别为0.034、0.245mg·L-1,都达到了国家污水综合排放标准(GB8978-1996)中所规定的要求(砷最高允许排放浓度0.5 mg·L-1)。Pb、Cd、Zn、Mn的去除率随着CRH-Ⅰ添加量的增加而逐渐上升,去除率分别为9.8%-30.7%、34.1%-55.1%、10.9%-22.8%、57.1%-66.7%。其中Pb、Cu也达到了排放标准。
[Abstract]:In recent years, biochar has been used as a new adsorption material to remove various heavy metals from contaminated soil and water. However, there are few reports on the removal of arsenic wastewater. In this study, five kinds of carbonized husks were prepared by pyrolysis at different temperature, anoxia and high temperature. After modified with acid and alkali, a carbonized husk with the best adsorption effect was selected and loaded with magnetic. Another new carbonized grain husk (CRH-I) loaded with nanometer Fe3O4 was obtained. The effects of adsorption time and pH, addition on the adsorption of CRH-I were studied, and the adsorption characteristics were investigated by adsorption kinetics and isothermal adsorption. At the same time, the adsorption and desorption ability of CRH-I and the removal ability of arsenic-containing wastewater were studied. The characterization and mechanism of CRH-I were studied from the aspects of BET surface area, pore size structure analysis and SEM,XRD,FTIR. The main results are as follows: (1) the results of screening the adsorption properties of As (鈪，

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