• Journal of Korean Society of Environmental Engineers
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• v.28 no.1
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• pp.54-60
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• 2006

[ $MnO_2$ ]-Coated Sand(MCS) was prepared with variation of coating temperature, coating time, and dosage of initial Fe(III) with two kinds of sands such as Joomoonjin and quartz sand. An optimum condition for the preparation MCS was determined from the coating efficiency as well as the oxidation efficiency of As(III). Coating efficiency of Mn was strongly dependent on the coating temperature but quite similar over the investigated coating time, showing an increased coating efficiency at higher coating temperature. In contrast to coating efficiency, the oxidation efficiency of As(III) by MCS was severely reduced as increase of coaling temperature. By considering these results, an optimum coating temperature and time for the preparation of MCS was selected as $150^{\circ}C$ and 1-hr, respectively. Coating efficiency increased as the dosage of initial Mn(II) increased, while As(III) oxidation was maximum at 0.8 Mn(II) mol/kg sand. The solution pH was identified as an important parameter affecting stability of MCS, and dissolution of Mn from MCS increased as pH decreased. Oxidation rate of As(III) increased as the dosage of MCS increased as well as solution pH decreased.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.571-576
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• 2007

Manganese-Coated Sand(MCS) prepared with three different methods were applied in the treatment of soluble $Mn^{2+}$ in batch and column experiments. In the bench-scale MCS preparation, the coating efficiency of manganese on the surface of sand increased as the dosage of initial Mn(II) increased. The removed amount of the soluble $Mn^{2+}$ by MCS increased as the solution pH increased, following a typical anionic-type adsorption. The removed amounts of the soluble $Mn^{2+}$ through adsorption was quite similar over the entire pH range, without depending on the contents of Mn on the surface of sand as well as coating methods. When NaClO was used an oxidant, the removed amount of the soluble $Mn^{2+}$ by MCS increased as the concentration of NaClO increased, This trend might be explained by the increased removal efficiency through coating of manganese oxides produced from oxidation of the soluble $Mn^{2+}$ by NaClO on the surface of MCS. From the bench-scale column experiments, the breakthrough of $Mn^{2+}$ occurred after 4,100 bed volume without presence of NaClO while 1.6-times delayed breakthrough of $Mn^{2+}$ was observed in the presence of NaClO. This result also supports that the removal efficiency of the soluble $Mn^{2+}$ could be enhanced by using NaClO.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.7
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• pp.473-482
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• 2009

In this study, iron and manganese coated sand (IMCS) was prepared by mixing Joomoonjin sand with solutions having different molar ratio of manganese ($Mn^{2+}$) and iron ($Fe^{3+}$). Mineral type of IMCS was analyzed by X-ray diffraction spectroscopy. Removal efficiency of arsenic through As(III) oxidation and As(V) adsorption by IMCS having different ratio of Mn/Fe was evaluated. The coated amount of total Mn and Fe on all IMCS samples was less than that on sand coated with iron-oxide alone (ICS) or manganese-oxide alone (MCS). The mineral type of the manganese oxide on MCS and iron oxides on ICS were identified as ${\gamma}-MnO_2$ and mixture of goethite and magnetite, respectively. The same mineral type was appeared on IMCS. Removed amount As(V) by IMCS was greatly affected by the content of Fe rather than by the content of Mn. Adsorption of As(V) by IMCS was little affected by the presence of monovalent and divalent electrolytes. However a greatly reduced As(V) adsorption as observed in the presence of trivalent electrolyte such as $PO_4\;^{3-}$. As(III) oxidation efficiency by MCS in the presence of NaCl or $NaNO_3$ was two times greater than that in the presence of $PO_4\;^{3-}$. Meanwhile a greater As(III) oxidation efficiency was observed by IMCS in the presence of $PO_4\;^{3-}$. This was explained by the competitive adsorption between phosphate and arsenate on the surface of IMCS.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.8
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• pp.878-883
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• 2006

Removal efficiency of As(III) was investigated with a pilot-scale filtration system packed with an equal amount(each 21.5 kg) of manganese-coated sand(MCS) in the bottom and iron-coated sand(ICS) in the top. Height and diameter of the used column was 200 cm and 15 cm, respectively. The As(III) solution was introduced into the bottom of the filtration system with a peristaltic pump at a speed of $5{\times}10^{-3}$ cm/s over 148 days. Breakthrough of total arsenic in the mid-sampling position(end of the MCS bed) and final-sampling position(end of the ICS bed) was started after 18 and 44 days, respectively, and then showed a complete breakthrough after 148 days. Although the breakthrough of total arsenic in the mid-sampling position was started after 18 days, the concentration of As(III) in this effluent was below 50 ppb up to 61 days. This result indicates that MCS has a sufficient oxidizing capacity to As(III) and can oxidize 92 mg of As(III) with 1 kg of MCS up to 61 days. When a complete breakthrough of total arsenic occurred, the removed total arsenic by MCS was calculated as 79.0 mg with 1 kg MCS. As variation of head loss is small at each sampling position over the entire reaction time, it was possible to operate the filtration system with ICS and MCS for a long time without a significant head loss.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1186-1191
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• 2006

Removal efficiency of As(III) through oxidation and adsorption in column reactors was investigated at different ratios of manganese-coated sand(MCS) and iron-coated sand(ICS) : MCS-alone, ICS-alone and both of ICS and MCS. The breakthrough of arsenic immediately occurred from a column reactor with MCS-alone. However, most of the arsenic present in the effluent was identified as As(V) due to the oxidation of As(III) by MCS. While five-times delayed breakthrough of arsenic was observed from a column reactor with ICS-alone. At a complete breakthrough of arsenic, the removed As(III) was 36.1 mg with 1 kg ICS. To find an optimum ratio of ICS and MCS in the column packed with both ICS and MCS, the removal efficiency of As(III) was investigated at three different ratios of ICS/MCS with a fixed amount of ICS. The breakthrough time of arsenic was quite similar in the different ratios ICS/MCS. However, much slower breakthrough of arsenic was observed as the ratio of ICS/MCS decreased. As the ratio of ICS/MCS decreased the concentration of As(III) in the effluent decreased and then showed below 50 ppb at an equal amount of ICS and MCS, suggesting more efficient oxidation of As(III) by greater amount of MCS. When a complete breakthrough of arsenic occurred, the removed total arsenic with an equal amount of ICS and MCS was 68.5 mg with 1 kg of filter material.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.193-200
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• 2010

This study evaluated treatability of soluble Mn(II) using multifunctional sand media simultaneously coated with iron and manganese. In the preparation of IMCS(Iron and Manganese Coated Sand), 0.05 M Mn(II) solution and Fe(III) solution was mixed with sand at pH 7. The mineral type of IMCS was identified as the mixture of ${\gamma}-MnO_2$, goethite and magnetite($F_{e3}O_4$). The contents of Mn and Fe coated onto sand were 826 and 1676 mg/kg, respectively. The $pH_{pzc}$ of IMCS was measured as 6.40. The removal of soluble Mn(II) using IMCS and oxidants such as NaOCl and $KMnO_4$ was investigated with variation of the solution pH, reaction time and Mn(II) concentration in a batch test. The removal of Mn(II) on IMCS was 34% at pH 7.4 and the removals of Mn(II) on IMCS in the presence of NaOCl(13.6 mg/L) at pH 7 and $KMnO_4$(4.8 mg/L) at pH 7.6 were 96% and 89%, respectively. The removal of Mn(II) using IMCS and oxidants followed a typical cationic type, showing a gradual increase of removal as the solution pH increased. The removal of Mn(II) was rapid in the first 6 hrs and then a constant removal was observed. The maximum removed amount of Mn(II) on IMCS-alone and IMCS in the presence of oxidants such as NaOCl(13.6 mg/L) and $KMnO_4$(4.8mg/L) were 833.3, 1428.6 and 1666.7 mg/kg, respectively. Mn(II) removal onto the IMCS in the presence of oxidants was well described by second-order reaction and Langmuir isotherm expression.