title: Effects of binding materials on microaggregate size distribution in bauxite residues.
abstract: It is recognized that for successful establishment of a vegetation cover on bauxite residue disposal areas, soil formation and a greater understanding of the processes of soil development are crucial. The stability of microaggregates is a very important physical property that prevents erosion in bauxite residues. Samples were collected from a disposal area in Central China to determine not only the mechanism of aggregation but also clay dispersion. Colloidal stability was assessed by determining organic matter, carbonate, electrolyte, clay mineral, and iron-aluminum oxide forms, as these would contribute to their stability. Organic matter improved microaggregate stability by combining with clay particles and polyvalent cations to form macroaggregates. Polyvalent cations such as calcium had a positive effect on particle flocculation, while organic molecules were more effective at stabilizing microaggregates. Removal of salinity dispersed silt-size aggregates into clay-size aggregates and reduced microaggregate stability. Calcium improved particle aggregation, while sodium had the reverse effect. Quartz powder was added to the residues but did not show any cementing effect, while free and amorphous iron-aluminum oxides were effective binding agents for microaggregate formation. We propose that the presence of organic matter and polyvalent cations, together with incorporation of organic carbon and calcium minerals, may enhance the stability of this material and prove beneficial toward improving its physical condition.
authors.affiliation: School of Metallurgy and Environment, Central South University, Changsha, 410083, People's Republic of China.|South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou, 510655, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhu
authors.affiliation: School of Metallurgy and Environment, Central South University, Changsha, 410083, People's Republic of China.
authors.forename: Nan
authors.initials: N
authors.lastname: Huang
authors.affiliation: School of Metallurgy and Environment, Central South University, Changsha, 410083, People's Republic of China. sgxue70@hotmail.com.
authors.forename: Shengguo
authors.initials: S
authors.lastname: Xue
authors.affiliation: Crop and Environment Sciences Department, Harper Adams University, Newport, Shropshire, TF10 8NB, UK.
authors.forename: William
authors.initials: W
authors.lastname: Hartley
authors.affiliation: School of Metallurgy and Environment, Central South University, Changsha, 410083, People's Republic of China.
authors.forename: Yiwei
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Metallurgy and Environment, Central South University, Changsha, 410083, People's Republic of China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zou
mesh_terms: D000537:Aluminum Oxide / Q000032:analysis* / Q000737:chemistry; D000538:Aluminum Silicates / Q000032:analysis / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D002681:China; D000077215:Clay; D005427:Flocculation; D010316:Particle Size; D012965:Sodium Chloride / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D002254:Carbonates; D012987:Soil; D012989:Soil Pollutants; D012965:Sodium Chloride; D000537:Aluminum Oxide; D000077215:Clay
keywords: Bauxite residue; Binding material; Clay dispersion ratio; Microaggregate size distribution; Microaggregate stability; Sodic properties