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摘要: 经过酸化改性后的天然磁铁矿，由于比表面积和内部结构发生变化，从而表现出很好的除砷性能，进一步研究其对水体中砷的吸附特征，为实际工程应用提供数据是十分必要的。本文对经0.5 mol/L盐酸浸泡、150℃温度下灼烧10 min的改性磁铁矿吸附砷的特征进行了表征，绘制吸附速率曲线图。吸附影响因素实验结果显示：当初始pH为6~9时，吸附性能强；Cl-、Ca2+、Mg2+、HCO3-、CO32-离子与As（Ⅲ）、As（Ⅴ）不会产生竞争吸附，PO43-、NO3-、SO42-离子与As（Ⅲ）产生竞争性吸附，且PO43- > SO42- > NO3-；PO43-、NO3-离子与As（Ⅴ）产生竞争性吸附。结合X射线衍射、扫描电镜等研究结果，初步探讨了改性磁铁矿的除砷机理，认为改性后的磁铁矿比表面积明显增大，表面生成物含有Fe（Ⅱ）和Fe（Ⅲ）是其吸附砷能力提高的主要原因。实验结果证实，改性天然磁铁矿是一种值得进一步研究并实际应用的水体除砷材料。Abstract: Acid-modified natural magnetite shows excellent arsenic removal properties due to its change in specific surface area and internal structure. It is essential to study further its adsorption to arsenic in water, in order to provide data for practical engineering applications. The feature of arsenic adsorption by modified magnetite immersed in 0.5 mol/L hydrochloric acid and ignited for 10 minutes at 150℃, and the construction of its adsorption rate curve chart is described in this paper. Results of the experiment on adsorption influencing factors indicate that when initial pH value are 6-9, magnetite shows strong adsorption property. Ions such as Cl-, Ca2+, Mg2+, HCO3-, CO32- do not have competitive adsorption with As(Ⅲ) and As(Ⅴ), but PO43-, NO3-, and SO42- have competitive adsorption with As(Ⅲ), in the order of PO43->SO42- >NO3-. PO43- and NO3- have competitive adsorption with As(Ⅴ). In combination with XRD, SEM, and other research results, preliminarily studies show the arsenic removal mechanism of modified magnetite, and conclude that modified magnetite shows an obviously increased specific surface area and that Fe(Ⅱ) and Fe(Ⅲ) contained in its surface products are the main cause for improving arsenic adsorption ability. Experimental results demonstrate that modified natural magnetite is a de-arsenic material for water, which deserves further study and practical application.
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表 1 Lagergren准一级和假二级吸附动力学模型拟合参数
Table 1. Kinetic parameters for As adsorption on the modified magnetite
As形态 温度
(℃)准一级动力学模型 假二级动力学模型 qe(exp)
(μg/g)R2 K1(h-1) qe(cal)(μg/g) R2 K2[(g/μg)h] q2(μg/g) As(Ⅲ) 15 0.9126 2.1017 54.97 0.9813 0.0108 92.59 91.53 25 0.9920 2.2845 43.77 0.9809 0.0118 84.75 91.12 35 0.9408 2.1667 18.92 0.9983 0.0106 94.34 94.10 45 0.9090 2.0934 18.92 0.9979 0.0108 92.59 98.29 As(Ⅴ) 15 0.9909 0.0507 1.12 0.9289 0.0068 147.06 97.49 25 0.9092 0.0654 1.16 0.9953 0.0103 97.08 98.00 35 0.9701 0.0209 1.05 0.9383 0.0093 107.53 94.20 45 0.9092 1.2271 16.87 0.9933 0.0088 113.64 97.89 
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