Pb(Ⅱ)、Zn(Ⅱ)、Cu(Ⅱ)在碱性钙基膨润土上的竞争吸附

Competitive Adsorption of Pb(Ⅱ), Zn(Ⅱ) and Cu(Ⅱ) on Alkaline Ca-bentonite

碱性钙基膨润土(ACB)对废水中的二价重金属离子具有良好的吸附效果,然而,关于多种重金属离子在ACB上的竞争吸附规律尚不明确。本试验利用Langmuir竞争吸附等温模型拟合Pb(Ⅱ)、Zn(Ⅱ)、Cu(Ⅱ)在ACB上的吸附平衡数据,研究3种重金属离子在ACB上的竞争吸附规律,并对影响竞争吸附能力强弱的主要原因进行分析。研究表明,随着溶液中共存重金属离子的增多,ACB对每种重金属的吸附容量会呈现下降趋势,重金属之间存在相互抑制的竞争吸附作用;3种重金属离子在ACB上竞争吸附强弱的顺序是:Pb(Ⅱ)>Cu(Ⅱ)>Zn(Ⅱ),且Cu(Ⅱ)和Zn(Ⅱ)的相互竞争作用最强;重金属的电负性及形成的表面沉淀产物是影响重金属离子在ACB上吸附强弱的关键因素。ACB在多种重金属离子共存时仍对Pb(Ⅱ)和Cu(Ⅱ)具有良好的吸附能力,在重金属吸附方面具有一定的选择性,且对毒性巨大的Pb(Ⅱ)具有优选的吸附性能,研究对于ACB实际工程化处理重金属废水具有一定的参考价值。

Although alkaline Ca-bentonite(ACB) has superior adsorption performance for divalent heavy metal ions in wastewater, the competitive adsorption law for various heavy metal ions is still unclear hampering ACB application for real wastewater. To find the competitive adsorption law of various heavy metal ions on ACB, Langmuir competitive adsorption model was used to fit the adsorption equilibrium data of Pb(Ⅱ), Zn(Ⅱ) and Cu(Ⅱ). In addition, the main factors affecting the competitive adsorption ability were also analyzed in this study. The results showed that the respective adsorption capacity of each heavy metal ion on ACB decreased with the increase of heavy metal ion types in solutions, which indicated that there existed inhibitory actions among heavy metal ions. The competitive adsorption ability for the three heavy metal ions followed the order: Pb(Ⅱ)> Cu(Ⅱ)>Zn(Ⅱ). In addition, the inhibitory effect between Cu(Ⅱ) and Zn(Ⅱ) was more obvious than other binary systems. The electronegativity of heavy metal ions and the formed substances by surface precipitation were the key factors affecting the competitive adsorption performance of various heavy metal ions on ACB. In all, ACB can remain good adsorption performance for Pb(Ⅱ) and Cu(Ⅱ) even in many heavy metal ions co-existing solutions. Moreover, ACB showed the certain selectivity especially having good preferential adsorption for poisonous Pb(Ⅱ) among three heavy metal ions. Therefore, this study is potentially useful for ACB practical applications in wastewater containing heavy metals.