• Environmental Engineering Research
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• v.14 no.1
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• pp.41-47
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• 2009

Column experiments were performed in this study to investigate humic acid adhesion to iron oxide-coated sand (ICS) under different experimental conditions including influent humic acid concentration, flow rate, solution pH, and ionic strength/composition. Breakthrough curves of humic acid were obtained by monitoring effluents, and then column capacity for humic acid adsorption ($C_cap$), total adsorption percent (R), and mass of humic acid adsorbed per unit mass of filter media ($q_a$) were quantified from these curves. Results showed that humic acid adhesion was about seven times higher in ICS than in quartz sand at given experimental conditions. This indicates that humic acid removal can be enhanced through the surface charge modification of quartz sand with iron oxide coating. The adhesion of humic acid in ICS was influenced by influent humic acid concentration. $C_cap$ and $q_a$ increased while R decreased with increasing influent humic acid concentration in ICS column. However, the influence of flow rate was not eminent in our experimental conditions. The humic acid adhesion was enhanced with increasing salt concentration of solution. $C_cap$, $q_a$ and R increased in ICS column with increasing salt concentration. On the adhesion of humic acid, the impact of CaCl2 was greater than that of NaCl. Also, the humic acid adhesion to ICS decreased with increasing solution pH. $C_cap$, $q_a$ and R decreased with increasing solution pH. This study demonstrates that humic acid concentration, salt concentration/composition, and solution pH should be controlled carefully in order to improve the ICS column performance for humic acid removal from water.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.341-349
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• 2010

It is well known that manganese is hard to oxidize under neutral pH condition in the atmosphere while iron can be easily oxidized to insoluble iron oxide. The purpose of this study is to identify removal mechanism of manganese in the D water treatment plant where is treating bank filtered water in aeration and rapid sand filtration. Average concentration of iron and manganese in bank filtered water were 5.9 mg/L and 3.6 mg/L in 2008, respectively. However, their concentration in rapid sand filtrate were only 0.11 mg/L and 0.03 mg/L, respectively. Most of the sand was coated with black colored manganese oxide except surface layer. According to EDX analysis of sand which was collected in different depth of sand filter, the content of i ron in the upper part sand was relatively higher than that in the lower part. while manganese content increased with a depth. The presence of iron and manganese oxidizing bacteria have been identified in sand of rapid sand filtration. It is supposed that these bacteria contributed some to remove iron and manganese in rapid sand filter. In conclusion, manganese has been simultaneously removed by physicochemical reaction and biological reaction. However, it is considered that the former reaction is dominant than the latter. That is, Mn(II) ion is rapidly adsorbed on ${\gamma}$-FeOOH which is intermediate iron oxidant and then adsorbed Mn(II) ion is oxidized to insoluble manganese oxide. In addition, manganese oxidation is accelerated by autocatalytic reaction of manganese oxide. The iron and manganese oxides deposited on the surface of the sand and then are aged with coating sand surface.

• Environmental Engineering Research
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• v.14 no.2
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• pp.134-139
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• 2009

In this study, oxidation of As (III) as well as removal of total arsenic by adsorbents coated with single oxides or multi-oxides (Fe (III), Mn (IV), Al (III)) was investigated. In addition, multi-functional properties of adsorbents coated with multi-oxides were evaluated. Finally, application of activated carbon impregnated with Fe or Mn-oxides on the treatment of As (III) or As (V) was studied. As (V) adsorption results with adsorbents containing Fe and Al shows that adsorbents containing Fe show a greater removal of As (V) at pH 4 than at pH 7. In contrast adsorbents containing Al shows a favorable removal of As (V) at pH 7 than at pH 4. In case of iron sand, it has a negligible adsorption capacity for As (V) although it contains 217.9 g-Fe/kg-adsorbent, Oxidation result shows that manganese coated sand (MCS) has the greatest As (III) oxidation capacity among all metal oxides at pH 4. Oxidation efficiency of As (III) by IMCS (iron and manganese coated sand) was less than that by MCS. However the total removed amount of arsenic by IMCS was greater than that by MCS.

• 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.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.379-381
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• 2003

Metal sorption onto the ICS (Iron oxide coated sand) was studied in batch experiments. Heavy metal cations such as Cd, Pb, and Cu, and a metal anion, As, which sporadically exist in mine sites, were tested for the sorptive removal by ICS. In low pH conditions As showed the highest removal efficiency compared to the other metal cations. And the sorption removal of As was apparently pH-independent reaction. However, removal of metal cations increased with pH and above pH 7 most metal cations showed very low soluble concentrations after treatment. Such a high removal ratio of metal cations above the neutral pH appeared predominantly due to precipitation.

• 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.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 on Water Environment
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• v.31 no.2
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• pp.209-215
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• 2015

The purpose of this study is to evaluate the characteristic of the iron oxide carrier for removing arsenic contained in the groundwater. 4 types of iron oxide carrier used in the study is iron oxide coated sand carrier (IOCSC), iron oxide coated zeolite carrier (IOCZC), iron oxide plasticity carrier (IOPC) and platinum iron oxide plasticity carrier (PIOPC). The results of this study, IOPC is showed high arsenic adsorption strength and the maximum amount of adsorption than the IOCC. Based on the results of the arsenic adsorption characteristic, by using IOCC was conducted to column test. As a result, PIOPC is showed a high arsenic adsorption amount than IOPC, it was found that the time required to reach the breakthrough point is also extended. Therefore it is determined that stably compliance with water quality standards enhanced drinking water when using the PIOPC.

• Proceedings of the KSEEG Conference
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• 2005.04a
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• pp.141-145
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• 2005

• Economic and Environmental Geology
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• v.38 no.5 s.174
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• pp.571-577
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• 2005

Permeable reactive barrier using iron oxide coated sand is one of effective technologies for As(V) contaminated groundwater. However, this method is restricted to As(III), because As(III) species tends to be more weakly bound to adsorbent. In order to overcome the limitation of iron oxide coated sand application to As(III) contaminated groundwater, manganese oxide materials as promoter of As(III) removal were combined to the conventional technology in this study. For combined use of iron oxide coated sand and manganese oxide coated sand, two kinds of removal methods, sequential removal method and simultaneous removal method, were introduced. Both methods showed similar removal efficiency over $85\%$ for 6 hrs. However, the sequential method converted the As contaminated water to acid state (pH 4.5), on the contrary, the simultaneous method maintained neutral state (pH 6.0). Therefore, simultaneous As removal method was ascertained as a suitable treatment technology of As contaminated water. Moreover, for more effective As(III) remediation technique, polypropylene textile which has the characteristics of high surface area, low specific gravity and flexibility was applied as alternative material of sand. The combined use of coated polypropylenes by simultaneous method showed much more prominent and rapid remediation efficiency over $99\%$ after 6 hrs; besides, it has practical advantages in replacement or disposal of adsorbent for simple conventional removal device.