Macroscopic and microscopic investigation of adsorption and precipitation of Zn on γ-alumina in the absence and presence of As.
Contaminants zinc (Zn) and arsenate (As) often coexist in soils. However, little is known concerning the impacts of coexisting As on Zn adsorption and precipitation on soil minerals. In the present study, adsorption and precipitation of Zn on γ-alumina in the absence and presence of arsenate was investigated employing batch experiments and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Results indicated that Zn formed edge-sharing tetrahedral surface complexes at pH 5.5 and Zn-Al LDH-like (layered double hydroxide) precipitates at pH 7.0 on the surface of γ-alumina. The presence of arsenate significantly enhanced Zn sorption densities, and remarkably changed its bonding environment. At pH 5.5, SR-XRD (Synchrotron Radiation-based X-ray Diffraction) and EXAFS showed that koettigite-like precipitate were formed in the cosorption of Zn and As on γ-alumina regardless of the addition sequence of As and Zn. At pH 7.0, when Zn was preequilibrated with γ-alumina prior to the As introduction, mixed Zn-Al LDH-like and amorphous adamite-like precipitates formed. However, when Zn and As were added simultaneously, only amorphous adamite-like precipitate was observed. Zn inner-sphere complexes and surface ternary complexes γ-alumina-As-Zn were the main outcome when As was preequilibrated firstly. Zn-arsenate precipitates could significantly decrease the concentration of Zn in aqueous solution and decrease the bioavailability and mobilization of Zn in soils.
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, PR China. Electronic address: yjwang@issas.ac.cn.
Yu-Jun
YJ
Wang
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, PR China.
Ting-Ting
TT
Fan
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, PR China.
Cun
C
Liu
Delaware Environmental Institute and Department of Plant and Soil Sciences, University of Delaware, Newark, DE, 19717-1303, United States.
Wei
W
Li
Department of Ecosystem Science and Management, University of Wyoming, Laramie, WY, 82071, United States.
Meng-Qiang
MQ
Zhu
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, PR China.
Jian-Xin
JX
Fan
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, PR China.
Hua
H
Gong
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, PR China.
Dong-Mei
DM
Zhou
Delaware Environmental Institute and Department of Plant and Soil Sciences, University of Delaware, Newark, DE, 19717-1303, United States.
Donald L
DL
Sparks
D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry*; D001149:Arsenates / Q000737:chemistry; D011232:Chemical Precipitation; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides; D008903:Minerals / Q000737:chemistry; D012989:Soil Pollutants / Q000302:isolation & purification*; D056928:X-Ray Absorption Spectroscopy; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry / Q000302:isolation & purification*
D001149:Arsenates; D006878:Hydroxides; D008903:Minerals; D012989:Soil Pollutants; C031356:hydroxide ion; D015032:Zinc; D000537:Aluminum Oxide; C025657:arsenic acid
Adsorption; Arsenate; EXAFS; Layered double hydroxide; Surface precipitation; Zinc