title: Sorption of Cu(2+) on humic acids sequentially extracted from a sediment.
abstract: In addition to the diverse properties of humic acids (HAs) extracted from different soils or sediments, chemical compositions, functional groups and structures of HAs extracted from a single soil or sediment could also be diverse and thus significantly affect sorption of heavy metals, which is a key process controlling the transfer, transformation and fate of heavy metals in the environment. In this study, we sequentially extracted four HA fractions from a single sediment and conducted the sorption experiments of Cu(2+) on these HA fractions. Our results showed that aromaticity and acidic group content of HA fraction decreased with increasing extraction. Earlier extracted HA fraction had higher sorption capacity and affinity for Cu(2+). There were two fractions of adsorbed Cu(2+) on HAs, i.e., ion exchanged fraction and surface bonded fraction, which can be captured mechanically by the bi-Langmuir model with good isotherm fitting. The ion exchanged fraction had larger sorption capacity but lower sorption affinity, compared with the surface bonded fraction. The dissociated carboxyl groups of HAs were responsible for both fractions of Cu(2+) sorption, due to the more Cu(2+) sorption on the earlier extracted HA fraction with more carboxyl groups and at higher pH. The intensive competition between H(+) and the exchangeable Cu(2+) could result in the decrease of ion exchanged capacity and affinity for Cu(2+) on HAs.
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China. Electronic address: kyang@zju.edu.cn.
authors.forename: Kun
authors.initials: K
authors.lastname: Yang
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China.
authors.forename: Gangfen
authors.initials: G
authors.lastname: Miao
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China; Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Wu
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China.
authors.forename: Daohui
authors.initials: D
authors.lastname: Lin
authors.affiliation: Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Pan
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
authors.forename: Fengchang
authors.initials: F
authors.lastname: Wu
authors.affiliation: Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: Baoshan
authors.initials: B
authors.lastname: Xing
mesh_terms: D000327:Adsorption; D003300:Copper / Q000737:chemistry* / Q000302:isolation & purification; D019015:Geologic Sediments / Q000737:chemistry*; D006812:Humic Substances; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D006812:Humic Substances; D012987:Soil; D012989:Soil Pollutants; D003300:Copper
keywords: Carboxyl groups; Cu(2+); Humic acids; Sorption; pH