Effects of pH on Microscopic Structure of Cu(Ⅱ) in Copper Nitrate Solution and Cu(Ⅱ) Adsorption on Microscopic Structure of Goethite

ZHANG Jin-jing1,WANG Shuai1,DOU Sen1,XIE Zhong-lei2(1.College of Resources and Environmental Sciences,Jilin Agricultural University,Changchun 130118,China;2.College of Environment and Resources,Jilin University,Changchun 130026,China)

extended X-ray absorption fine structure;Cu(NO3)2;goethite;pH;adsorption;microscopic local structure

It is important to understand the microscopic structure of Cu or Fe for clarifying their environmental behavior.The effects of pH on microscopic local structure of Cu(Ⅱ) in Cu(NO3)2 solution and Cu(Ⅱ) adsorption on that of goethite(α-FeOOH) were preliminarily studied by extended x-ray absorption fine structure(EXAFS) technique.The results showed that the microscopic local structure of Cu(Ⅱ) in Cu(NO3)2 solution under different pH conditions was identical,and the coordination number(N),bond length(R) and thermal disorder parameter(σt2) were 4.3～4.4,1.95～1.96 and 0.005 6 2 for the Cu-O first neighbor shell,respectively.The Jahn-Teller effect which makes the axial Cu-O bonds difficult to characterize quantitatively by EXAFS spectroscopy was related to the EAXFS results of Cu(Ⅱ).The coordination peak of Cu-Cu was not detected at pH 2,but it occurred at about 2.40 at pH 8,indicating that the formation of Cu(OH)2 precipitate at pH 8.Before the adsorption of Cu(Ⅱ) onto goethite,the N,R and σt2 were 6.2,1.98 and 0.008 3 2 for the Fe-O first neighbor shell in goethite respectively.The N and R of Fe-O were identical to initial goethite after the adsorption of Cu(Ⅱ) onto goethite,but its σt2 increased.