title: Effect of co-existing kaolinite and goethite on the aggregation of graphene oxide in the aquatic environment.
abstract: Broad applications of graphene oxide (GO) will result in the release of GO into aquatic environments, where clay minerals and metal (hydr)oxides are commonly present. Thereby the interactions between GO and a binary system containing clay minerals and metal (hydr)oxides can occur. We investigated the aggregation of GO with kaolinite and kaolinite-goethite associations (KGAs) in aquatic systems under different pHs, ionic strengths, and GO concentrations. GO suspension was unstable at low pHs, and the aggregation of GO occurred in the presence of KGA-4% and KGA-10% until pH 5 and 6, respectively. Kaolinite decreased the critical coagulation concentration (CCC) of GO at pH 5.5 from around 50 to 20 mM NaCl due to the reduced energy barrier. Heteroaggregation of GO with KGAs was extremely sensitive to ionic strength at pH 5.5, and the CCC of GO in the presence of KGA-10% increased from less than 1 mM NaCl to 5 mM NaCl with the increase of pH from 5.5 to 9. The heteroaggregation extent of GO with KGAs was enhanced firstly, then reduced with the increase of GO concentrations at pH 5.0, which is likely because KGA plates were more efficiently wrapped by large-size GO sheets with increasing GO concentrations. These findings are useful for understanding and predicting the fate of GO in the relatively complicated aquatic and soil environments where binary minerals co-exist.
authors.affiliation: Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang, 050061, China; Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA, 01003, USA.
authors.forename: Guanxing
authors.initials: G
authors.lastname: Huang
authors.affiliation: Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA, 01003, USA.
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Guo
authors.affiliation: Institute of Costal Environmental Pollution Control, and Ministry of Education Key Laboratory of Marine Environment and Ecology, Ocean University of China, Qingdao, 266100, China. Electronic address: jzhao@ouc.edu.cn.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA, 01003, USA; Department of Chemistry, College of Science, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA, 01003, USA. Electronic address: bx@umass.edu.
authors.forename: Baoshan
authors.initials: B
authors.lastname: Xing
mesh_terms: D006108:Graphite; D007616:Kaolin; D009994:Osmolar Concentration; D010087:Oxides; D012987:Soil
chemical_list: D010087:Oxides; D012987:Soil; D007616:Kaolin; D006108:Graphite
keywords: Critical coagulation concentration; Graphene oxide; Heteroaggregation; Ionic strength; Kaolinite-goethite associations