Interaction of fluoride with hydroxyaluminum-montmorillonite complexes and implications for fluoride-contaminated acidic soils |
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| Institution: | 1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences 210008, PR China;2. Department of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266003, PR China;3. Department of Environmental Science and Engineering, Ocean University of China, Qingdao 266003, PR China;1. School of Chemical Engineering, The University of Queensland, St Lucia 4072, QLD, Australia;2. Department of Chemical & Environmental Engineering, University of Nottingham Selangor, Malaysia;3. Department of Chemical Engineering & Biotechnology, National Taipei University of Technology, Taipei City, Taiwan, ROC;1. Nutritional Biochemistry Laboratory, Department of Human Physiology, Tripura University, Suryamaninagar 799 022, West Tripura, India;2. Department of Chemistry, Netaji Subhas Mahavidyalaya, Udaipur 799 114, Gomati Tripura, India;3. Department of Chemistry, National Institute of Technology, Agartala, Jirania 799 055, India;1. State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei 230036, China;2. School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China;3. School of Land and Food, University of Tasmania, Hobart, Tasmania 7001, Australia;4. College of Resource & Environment Science, Nanjing Agricultural University, Nanjing 210095, China;5. Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529, USA;1. PG & Research Department of Physics, AVVM Sri Pushpam College (Autonomous), Poondi, Thanjavur, 613 503, Tamil Nadu, India;2. Institute of Physics, Bhubaneswar, 751 005, Odisa, India |
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| Abstract: | In acidic soils and aquatic environments, polymeric hydroxyaluminum (HyAl) cations with various OH/Al ratios are ubiquitous. Hydroxyaluminum-montmorillonite (HyAl-Mt) complexes are widely distributed in acidic to slightly acidic soils and aquatic environments. The fixation of HyAl cations on Mt can significantly modify the mineralogical and electrochemical properties of the host clay, thereby substantially influencing adsorption/desorption and transport of many nutrients and pollutants. In the present study, HyAl-Mt complexes were synthesized through adsorption of polymeric HyAl cations with OH/Al ratio of 1.6 on Na-saturated Mt (Na-Mt). Interaction of F− with HyAl-Mt was investigated in acidic conditions and the environmental implications for F−-contaminated soils were also addressed. Results indicated that the effects of pH on F− sorption by HyAl-Mt were slight in the pH range of 5.0–9.0, whereas sorption increased rapidly with decreasing pH when pH was below 4.5. At initial pH >4.0, ligand exchange was the main mechanism for F− sorption. At initial pH 3.02 and high initial F− concentrations, several synergic mechanisms, such as coprecipitation, scavenging and surface adsorption were involved in F− removal from solution, which resulted in an abrupt and discontinuous increase in sorption capacity of HyAl-Mt for F− with increasing initial F− concentration, and a slight dependency of F− sorption on HyAl-Mt dosage. Compared with Na-Mt, sorption capacities of HyAl-Mt for F− were significantly enhanced by interlayering and coating with polymeric HyAl cations. HyAl-Mt would be important natural scavengers for F−. The presence of HyAl-Mt in acidic soils could greatly retard F− transport and bioavailability in soil environments. Interaction of F− with HyAl-Mt may mitigate acidification of F−-contaminated acidic soils. Application of synthetic HyAl-Mt may be one alternative for remediation of acidic F−-contaminated soils. |
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