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Formation of Manganese Oxide Coatings onto Sand for Adsorption of Trace Metals from Groundwater
Author(s) -
Tilak A. S.,
Ojewole S.,
Williford C. W.,
Fox G. A.,
Sobecki T. M.,
Larson S. L.
Publication year - 2013
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2013.04.0142
Subject(s) - adsorption , manganese , coating , chemistry , groundwater , aquifer , volumetric flow rate , oxide , environmental chemistry , geology , physics , geotechnical engineering , organic chemistry , quantum mechanics
Manganese oxide (MnO x(s) ) occurs naturally in soil and has a high affinity for trace metals adsorption. In this work, we quantified the factors (pH; flow rate; use of oxidants such as bleach, H 2 O 2 , and O 3 ; initial Mn(II) concentrations; and two types of geologic media) affecting MnO x(s) coatings onto Ottawa and aquifer sand using batch and column experiments. The batch experiments consisted of manual and automated titration, and the column experiments mimicked natural MnO x(s) adsorption and oxidation cycles as a strategy for in situ adsorption. A Pb solution of 50 mg L −1 was passed through MnO x(s) –coated sand at a flow rate of 4 mL min −1 to determine its adsorption capacity. Batch experimental results showed that MnO x(s) coatings increased from pH 6 to 8, with maximum MnO x(s) coating occurring at pH 8. Regarding MnO x(s) coatings, bleach and O 3 were highly effective compared with H 2 O 2 . The Ottawa sand had approximately twice the MnO x(s) coating of aquifer sand. The sequential increase in initial Mn(II) concentrations on both sands resulted in incremental buildup of MnO x(s) . The automated procedure enhanced MnO x(s) coatings by 3.5 times compared with manual batch experiments. Column results showed that MnO x(s) coatings were highly dependent on initial Mn(II) and oxidant concentrations, pH, flow rate, number of cycles (h), and the type of geologic media used. Manganese oxide coating exceeded 1700 mg kg −1 for Ottawa sand and 130 mg kg −1 for aquifer sand. The Pb adsorption exceeded 2200 mg kg −1 for the Ottawa sand and 300 mg kg −1 for the aquifer sand.