• Journal of Environmental Science International
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• v.20 no.2
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• pp.241-249
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• 2011

In this research, equilibrium of adsorption and kinetics of As(V) removal were investigated. The coal mine drainage sludge(CMDS) was used as adsorbent. To find out the physical and chemical properties of CMDS, XRD (X-ray diffraction), XRF (X-ray fluorescence spectrometer) analysis were carried out. The CMDS was consist of 70% of goethite and 30% of calcite. From the results, an adsorption mechanism of As(V) with CMDS was dominated by iron oxides. Langmuir adsorption isotherm model was fitted well more than Freundlich isotherm adsorption model. Adsorption capacities of CMDS 1 was not different with CMDS 2 on aspect of amounts of arsenic adsorbed. The maximum adsorption amount of two CMDS were respectively 40.816, 39.682 mg/g. However, the kinetic of two CMDS was different. The kinetic was followed pseudo second order model than pseudo first order model. Concentrations of arsenic in all segments of the polymer in CMDS 2 does not have a constant value, but the rate was greater than the value of CMDS 1. Therefore, CMDS 2, which is containing polymer, is more effective for adsorbent to remove As(V).

• Economic and Environmental Geology
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• v.53 no.6
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• pp.667-675
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• 2020

An Alum-sludge based adsorbent (ASBA) was synthesized by the hydrothermal treatment of alum sludge obtained from settling basin in water treatment plant. ASBA was applied to remove fluoride and arsenic in artificially-contaminated aqueous solutions and mine drainage. The mineralogical crystal structure, composition, and specific surface area of ASBA were identified. The result revealed that ASBA has irregular pores and a specific surface area of 87.25 ㎡ g-1 on its surface, which is advantageous for quick and facile adsorption. The main mineral components of the adsorbent were found to be quartz(SiO2), montmorillonite((Al,Mg)2Si4O10(OH)2·4H2O) and albite(NaAlSi3O8). The effects of pH, reaction time, initial concentration, and temperature on removal of fluoride and arsenic were examined. The results of the experiments showed that, the adsorbed amount of fluoride and arsenic gradually decreased with increasing pH. Based on the results of kinetic and isotherm experiments, the maximum adsorption capacity of fluoride and arsenic were 7.6 and 5.6 mg g-1, respectively. Developed models of fluoride and arsenic were suitable for the Langmuir and Freundlich models. Moreover, As for fluoride and arsenic, the increase rate of adsorption concentration decreased after 8 and 12 hr, respectively, after the start of the reaction. Also, the thermodynamic data showed that the amount of fluoride and arsenic adsorbed onto ASBA increased with increasing temperature from 25℃ to 35℃, indicating that the adsorption was endothermic and non-spontaneous reaction. As a result of regeneration experiments, ASBA can be regenerated by 1N of NaOH. In the actual mine drainage experiment, it was found that it has relatively high removal rates of 77% and 69%. The experimental results show ASBA is effective as an adsorbent for removal fluoride and arsenic from mine drainage, which has a small flow rate and acid/neutral pH environment.

• Membrane Journal
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• v.26 no.2
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• pp.116-125
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• 2016

This study described a synthesis of MF having a arsenic removal characteristics and the fundamental research was performed about the simultaneous removal system of both As(III) and As(V) ions with the composite nanofiber membrane (PMF) based on PVdF and MF materials for the water-treatment application. From the TEM analysis, the shape and structure of MF materials was investigated. The mechanical strength, pore-size, contact angle and water-flux analysis for the PMF was performed to investigate the possibility of utilizing as a water treatment membrane. From these results, the PMF11 showed the highest value of mechanical strength ($232.7kgf/cm^2$) and the pore-diameter of composite membrane was reduced by introducing the MF materials. In particular, their pore diameter decreased with an increase of iron oxide composition ratio. The water flux value of PMF was improved about 10 to 60% compared with that of neat PVdF nanofiber membranes. From the arsenic removal characterization of prepared MF materials and PMF, it was shown the simultaneous removal characteristics of both As(III) and (V) ions, and the MF01, in particular, showed the highest adsorption-removal rate of 93% As(III) and 68% As(V), respectively. From these results, prepared MF materials and PMF have shown a great potential to be utilized for the fundamental study to improve the functionality of water treatment membrane.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.561-567
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• 2021

The edible sargasso seaweed hijiki Sargassum fusiforme is known to have high concentration of arsenic, which is a threat to human health, particularly due to inorganic arsenic. In this study, various methods were used to remove inorganic arsenic from steamed hijiki concentrate. The highest concentration of arsenate [As(V)] in both raw and processed hijiki during steamed hijiki manufacturing process was within the range of 8.213-14.356 mg/kg, and it is a potential source of inorganic arsenic, which can result in re-contamination and cause environmental pollution. The removal efficiencies of the various removal methods were within the range of 57.3-83.4%, and 19.0% reduction was achieved using activated carbon and alginate bead. Further, activated carbon showed the best adsorption effect of inorganic arsenic. Therefore, we suggest that activated carbon is a suitable efficient method for removing inorganic arsenic and has low operational costs in field applicability.

• Applied Chemistry for Engineering
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• v.34 no.2
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• pp.199-205
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• 2023

Arsenic is a highly toxic element, and its contamination is widespread around the world. The natural materials with high selectivity and efficiency toward pollutants are important in wastewater treatment technology. In this study, the mesoporous synthetic hectorite was synthesized by facile hydrothermal crystallization of gels comprising silica, magnesium hydroxide, and lithium fluoride. Additionally, the naturally available clay was modified using zirconium at room temperature. Both synthetic and modified natural clays were employed in the removal of arsenate from aquatic environments. The materials were fully characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform-infrared (FT-IR) analyses. The synthesized materials were used to remove arsenic (V) under varied physicochemical conditions. Both materials, i.e., Zr-bentonite and Zr-hectorite, showed high percentage removal of arsenic (V) at lower pH, and the efficiency decreased in an alkaline medium. The equilibrium-state sorption data agrees well with the Langmuir and Freundlich adsorption isotherms, and the maximum sorption capacity is found to be 4.608 and 2.207 mg/g for Zr-bentonite and Zr-hectorite, respectively. The kinetic data fits well with the pseudo-second order kinetic model. Furthermore, the effect of the background electrolytes study indicated that arsenic (V) is specifically sorbed at the surface of these two nanocomposites. This study demonstrated that zirconium intercalated synthetic hectorite as well as zirconium modified natural clays are effective and efficient materials for the selective removal of arsenic (V) from aqueous medium.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.920-925
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• 2008

In this presentation, a leaching experiment which is followed the pH changes(pH=4, pH=7) and the mixing rates(1%, 3%, 5%, 7%) was carried out to examine the arsenic reduction effects and the leaching characteristics on arsenic contaminated soil after stabilization treatment in which 5 materials were used as stabilization agencies, i.e. ZVI(zero valent iron), blast furnace slag, steel refining slag, quick lime, and oyster shell meal. Except for blast furnace slag, the arsenic removal rate increased as the mixing rate increases of stabilization agencies. Arsenic leaching concentration was indicated that pH=7 condition is higher than pH=4 condition. This result shows because arsenic immobilization reaction increases as pH decreases, and arsenic adsorption takes place as pH decreases.

• Economic and Environmental Geology
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• v.46 no.6
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• pp.521-533
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• 2013

This study was initiated to evaluate the applicability of Si slag as an adsorbent via investigation of the main properties of Si slag as an adsorbent aw well as characterization of adsorption features between aqueous arsenic and Si slag. The specific surface area of Si slag was measured to be 6.71 $m^2/g$ which seems to be slightly higher than those of other slags, but relatively lower than those of iron (oxyhydr)oxides extensively used for arsenic controlling processes. The point of zero salt effect (PZSE) of Si slag determined by potentiometric titration appeared to be comparatively high (7.3), indicating the Si slag may be favorably used for adsorption of arsenic which predominantly exists as an oxy-anions. The results of adsorption isotherm indicate that regardless of arsenic species, Langmuir-type isotherm is the most suitable to simulate the adsorption of arsenic onto Si slag. With regard to pH-dependence of arsenic adsorption, the adsorption maxima of arsenite was centered at pH 7, and the adsorption was remarkably decreased in the other pH conditions. In the case of arsenate, on the other hand, the adsorption was highest at the lowest pH (4.0) and then gradually decreased with the increase of pH. Based on the results of kinetic experiments, it is likely that the adsorption of arsenite approached equilibrium within 2 hr, but it took about 8 hr for arsenate adsorption to be equilibrated. In addition, the Pseudo second order was evaluated to be most consistent with the empirical data of arsenic adsorption onto Si slag in this study. Under identical conditions, the affinity of arsenate onto Si slag was estimated to be nearly 6 times higher than that of arsenite.

• Membrane Journal
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• v.26 no.6
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• pp.480-489
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• 2016

In this study, the PVdF/MGO composite nanofiber membranes (PMGs) introducing Iron oxide-Graphene oxide ($Fe_3O_4/GO$, Metallic graphene oxide; MGO) was prepared via electrospinng method and its arsenic removal characteristics were investigated. The thermal treatment was carried out to improve the mechanical strength of nanofiber membranes and then the results showed that of outstanding improvement effect. However, in case of PMGs, the decreasing tendency of mechanical strength was indicated as increasing MGO contents. From the results of pore-size analysis, it was confirmed that the porous structured membranes with 0.3 to $0.45{\mu}m$ were prepared. For the water treatment application, the water flux measurement was carried out. In particular, PMG2.0 sample showed about 70% improved water flux results ($153kg/m^2h$) compared to that of pure PVdF nanofiber membrane ($91kg/m^2h$) under the 0.3 bar condition. In addition, the PMGs have indicated the high removal rates of both As(III) and As(V) (up to 81% and 68%, respectively). Based on the adsorption isotherm analysis, the adsorption of As(III) and As(V) ions were both more suitable for the Freundlich. From all of results, it was concluded that PVdF/MGO composite nanofiber membranes could be utilized as a water treatment membrane and for the Arsenic removal applications.

• Progress in Superconductivity and Cryogenics
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• v.22 no.2
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• pp.1-6
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• 2020

Large-scale civil engineering works discharge a large amount of soil suspension contaminated with natural heavy metals. Most of the heavy metal ions due to industrial activities and minings are accumulated in the soils and the sediments of lakes and inner bays through the rivers. It is necessary to remove heavy metals from the soils and the sediments, because some of these heavy metals, such as arsenic and cadmium, have significant biological effects even in small amounts. This study proposes a new volume reduction method of the contaminated soils and sediments by superconducting magnetic separation. Our process can remove the specific minute minerals selectively, which adsorbs heavy metals depending on pH. As a fundamental study, the adsorption behaviors of arsenic and cadmium on minute minerals as a function of pH were investigated, and the adsorption mechanism was discussed based on the crystal structure and pH dependence of surface potential in each minute minerals.

• Journal of Soil and Groundwater Environment
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• v.18 no.3
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• pp.58-64
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• 2013

This study proposed a low temperature hydrothermal carbonization to treat and recycle sewage sludge and determined the optimal conditions for the biochar production. The physical and chemical properties of biochar were analyzed and its sorption capacity for heavy metals was evaluated. To produce biochar, 50 g of sewage sludge was heated at 220, 230, and $240^{\circ}C$ for 1, 2, 3, 5, 8, and 10 hours in a reactor. The optimal conditions to produce biochar was $230^{\circ}C$ and 8 hours. Sorption capacity tests were conducted for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn) and nickel (Ni). Among them, lead was shown the highest heavy metal adsorption efficiency of biochar, followed by copper, cadmium, zinc, and nickel, but arsenic was hardly adsorbed overall.