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Econ. Environ. Geol. 2021; 54(6): 709-716

Published online December 28, 2021

https://doi.org/10.9719/EEG.2021.54.6.709

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

A Study of Fluoride Adsorption in Aqueous Solution Using Iron Sludge based Adsorbent at Mine Drainage Treatment Facility

Joon Hak Lee1,2, Sun Joon Kim2,*

1Technology Research & Development Institute, Korea Mine Rehabilitation & Mineral Resources corp(KOMIR), Wonju 26464, Republic of Korea
2Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, Republic of Korea

Correspondence to : *nnsjkim@hanyang.ac.kr

Received: November 9, 2021; Revised: December 6, 2021; Accepted: December 8, 2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

In this study, an adsorbent prepared by natural drying of iron hydroxide-based sludge collected from settling basin at a mine drainage treatment facility located in Gangneung, Gangwon-do was used to remove fluoride in an artificial fluoride solution and mine drainage, and the adsorption characteristics of the adsorbent were investigated. As a result of analyzing the chemical composition, mineralogical properties, and specific surface area of the adsorbent used in the experiment, iron oxide (Fe2O3) occupies 79.2 wt.% as the main constituent, and a peak related to calcite (CaCO3) in the crystal structure analysis was analyzed. It was also identified that an irregular surface and a specific surface area of 216.78 m2·g-1. In the indoor batch-type experiment, the effect of changes in reaction time, pH, initial fluoride concentration and temperature on the change in adsorption amount was analyzed. The adsorption of fluoride showed an adsorption amount of 3.85 mg·g-1 16 hours after the start of the reaction, and the increase rate of the adsorption amount gradually decreased. Also, as the pH increased, the amount of fluoride adsorption decreased, and in particular, the amount of fluoride adsorption decreased rapidly around pH 5.5, the point of zero charge at which the surface charge of the adsorbent changes. Meanwhile, the results of the isotherm adsorption experiment were applied to the Langmuir and Freundlich isotherm adsorption models to infer the fluoride adsorption mechanism of the used adsorbent. To understand the thermodynamic properties of the adsorbent using the Van't Hoff equation, thermodynamic constants ΔH° and ΔG° were calculated using the adsorption amount information obtained by increasing the temperature from 25°C to 65°C to determine the adsorption characteristics of the adsorbent. Finally, the adsorbent was applied to the mine drainage having a fluoride concentration of about 12.8 mg·L-1, and the fluoride removal rate was about 50%.

Keywords adsorption, mine drainage, fluoride, langmuir model, freundlich model

광산배수 정화시설 철 슬러지 기반 흡착제를 활용한 수용액상 불소 흡착에 관한 연구

이준학1,2 · 김선준2,*

1한국광해광업공단, 광해방지연구팀
2한양대학교 공과대학 자원환경공학과

요 약

본 연구에서는 강원도 강릉에 위치한 광산배수 처리시설 침전지에서 채취한 철 수산화물 기반의 슬러지를 자연 건조해 제조한 흡착제를 사용하여 인공 불소 수용액 및 실제 광산배수에 적용하여 흡착제의 불소 흡착 특성을 확인하였다. 실험에 사용된 흡착제의 화학적 성분, 광물학적 특성 및 비표면적을 분석한 결과, 주구성광물로 산화 철(Fe2O3)이 79.2 wt.%를 차지하며, 결정구조 분석에서 방해석(CaCO3)과 관련된 피크가 분석되었다. 또한 불규칙한 표면과 216.78 m2·g-1의 비표면적을 가지고 있음이 확인되었다. 실내 회분식 실험에서는 반응시간, pH, 초기 불소 농도 및 온도 등의 변화가 흡착량 변화에 미치는 영향을 확인하였다. 동적 흡착실험 결과, 불소의 흡착은 반응 시작 16시간 후 3.85 mg·g-1의 흡착량을 보이며 흡착량이 증가하다 점차 흡착량의 증가율이 감소하였으며, 등온 흡착실험에서 확인된 흡착제의 이론적 최대 흡착량은 81.01 mg·g-1으로 분석되었다. 또한 pH가 증가할수록 불소의 흡착량이 감소하는 모습을 보였으며, 특히 흡착제의 영전하점인 pH 5.5 부근에서 급격한 감소량을 나타냈다. 한편 등온 흡착실험의 결과를 Langmuir 및 Freundlich 등온 흡착 모델에 적용하여 사용한 흡착제의 불소 흡착 메커니즘을 유추한 결과, Freundlich 등온 흡착 모델과 더 높은 상관관계(R2=0.9138)로 일치하는 모습을 보였다. Van't Hoff 식을 활용하여 흡착제의 열역학적 특성을 파악하기 위해 25℃에서 65℃까지 온도를 증가시키며 획득한 흡착량 정보로 열역학적 상수 △Ho와 △Go을 계산하여 흡착제가 흡열의 흡착 특성을 보이며 반응이 비자발적임을 도출하였다. 마지막으로 약 12.8 mg·L-1의 불소 농도를 가지는 광산배수에 흡착제를 적용하여 실제 환경에서 흡착제의 적용가능성을 확인한 결과, 약 50%의 불소 제거효과가 있는 것으로 나타났다.

주요어 흡착, 광산배수, 불소, Langmuir 흡착 모델, Freundlich 흡착 모델

Article

Research Paper

Econ. Environ. Geol. 2021; 54(6): 709-716

Published online December 28, 2021 https://doi.org/10.9719/EEG.2021.54.6.709

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

A Study of Fluoride Adsorption in Aqueous Solution Using Iron Sludge based Adsorbent at Mine Drainage Treatment Facility

Joon Hak Lee1,2, Sun Joon Kim2,*

1Technology Research & Development Institute, Korea Mine Rehabilitation & Mineral Resources corp(KOMIR), Wonju 26464, Republic of Korea
2Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, Republic of Korea

Correspondence to:*nnsjkim@hanyang.ac.kr

Received: November 9, 2021; Revised: December 6, 2021; Accepted: December 8, 2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

In this study, an adsorbent prepared by natural drying of iron hydroxide-based sludge collected from settling basin at a mine drainage treatment facility located in Gangneung, Gangwon-do was used to remove fluoride in an artificial fluoride solution and mine drainage, and the adsorption characteristics of the adsorbent were investigated. As a result of analyzing the chemical composition, mineralogical properties, and specific surface area of the adsorbent used in the experiment, iron oxide (Fe2O3) occupies 79.2 wt.% as the main constituent, and a peak related to calcite (CaCO3) in the crystal structure analysis was analyzed. It was also identified that an irregular surface and a specific surface area of 216.78 m2·g-1. In the indoor batch-type experiment, the effect of changes in reaction time, pH, initial fluoride concentration and temperature on the change in adsorption amount was analyzed. The adsorption of fluoride showed an adsorption amount of 3.85 mg·g-1 16 hours after the start of the reaction, and the increase rate of the adsorption amount gradually decreased. Also, as the pH increased, the amount of fluoride adsorption decreased, and in particular, the amount of fluoride adsorption decreased rapidly around pH 5.5, the point of zero charge at which the surface charge of the adsorbent changes. Meanwhile, the results of the isotherm adsorption experiment were applied to the Langmuir and Freundlich isotherm adsorption models to infer the fluoride adsorption mechanism of the used adsorbent. To understand the thermodynamic properties of the adsorbent using the Van't Hoff equation, thermodynamic constants ΔH° and ΔG° were calculated using the adsorption amount information obtained by increasing the temperature from 25°C to 65°C to determine the adsorption characteristics of the adsorbent. Finally, the adsorbent was applied to the mine drainage having a fluoride concentration of about 12.8 mg·L-1, and the fluoride removal rate was about 50%.

Keywords adsorption, mine drainage, fluoride, langmuir model, freundlich model

광산배수 정화시설 철 슬러지 기반 흡착제를 활용한 수용액상 불소 흡착에 관한 연구

이준학1,2 · 김선준2,*

1한국광해광업공단, 광해방지연구팀
2한양대학교 공과대학 자원환경공학과

Received: November 9, 2021; Revised: December 6, 2021; Accepted: December 8, 2021

요 약

본 연구에서는 강원도 강릉에 위치한 광산배수 처리시설 침전지에서 채취한 철 수산화물 기반의 슬러지를 자연 건조해 제조한 흡착제를 사용하여 인공 불소 수용액 및 실제 광산배수에 적용하여 흡착제의 불소 흡착 특성을 확인하였다. 실험에 사용된 흡착제의 화학적 성분, 광물학적 특성 및 비표면적을 분석한 결과, 주구성광물로 산화 철(Fe2O3)이 79.2 wt.%를 차지하며, 결정구조 분석에서 방해석(CaCO3)과 관련된 피크가 분석되었다. 또한 불규칙한 표면과 216.78 m2·g-1의 비표면적을 가지고 있음이 확인되었다. 실내 회분식 실험에서는 반응시간, pH, 초기 불소 농도 및 온도 등의 변화가 흡착량 변화에 미치는 영향을 확인하였다. 동적 흡착실험 결과, 불소의 흡착은 반응 시작 16시간 후 3.85 mg·g-1의 흡착량을 보이며 흡착량이 증가하다 점차 흡착량의 증가율이 감소하였으며, 등온 흡착실험에서 확인된 흡착제의 이론적 최대 흡착량은 81.01 mg·g-1으로 분석되었다. 또한 pH가 증가할수록 불소의 흡착량이 감소하는 모습을 보였으며, 특히 흡착제의 영전하점인 pH 5.5 부근에서 급격한 감소량을 나타냈다. 한편 등온 흡착실험의 결과를 Langmuir 및 Freundlich 등온 흡착 모델에 적용하여 사용한 흡착제의 불소 흡착 메커니즘을 유추한 결과, Freundlich 등온 흡착 모델과 더 높은 상관관계(R2=0.9138)로 일치하는 모습을 보였다. Van't Hoff 식을 활용하여 흡착제의 열역학적 특성을 파악하기 위해 25℃에서 65℃까지 온도를 증가시키며 획득한 흡착량 정보로 열역학적 상수 △Ho와 △Go을 계산하여 흡착제가 흡열의 흡착 특성을 보이며 반응이 비자발적임을 도출하였다. 마지막으로 약 12.8 mg·L-1의 불소 농도를 가지는 광산배수에 흡착제를 적용하여 실제 환경에서 흡착제의 적용가능성을 확인한 결과, 약 50%의 불소 제거효과가 있는 것으로 나타났다.

주요어 흡착, 광산배수, 불소, Langmuir 흡착 모델, Freundlich 흡착 모델

    Fig 1.

    Figure 1.A photo(a) and size(b) of the adsorbent used in this study.
    Economic and Environmental Geology 2021; 54: 709-716https://doi.org/10.9719/EEG.2021.54.6.709

    Fig 2.

    Figure 2.(a) X-ray diffraction patterns and (b) SEM-EDS data of adsorbent.
    Economic and Environmental Geology 2021; 54: 709-716https://doi.org/10.9719/EEG.2021.54.6.709

    Fig 3.

    Figure 3.(a) SEM-EDS peak patterns and (b) SEM-EDS data of adsorbent.
    Economic and Environmental Geology 2021; 54: 709-716https://doi.org/10.9719/EEG.2021.54.6.709

    Fig 4.

    Figure 4.Kinetic adsorption data of fluoride adsorption onto adsorbent.
    Economic and Environmental Geology 2021; 54: 709-716https://doi.org/10.9719/EEG.2021.54.6.709

    Fig 5.

    Figure 5.Effect of pH environment on the adsorption capacity of adsorbent for fluoride.
    Economic and Environmental Geology 2021; 54: 709-716https://doi.org/10.9719/EEG.2021.54.6.709

    Fig 6.

    Figure 6.Point of zero charge(pzc) determination.
    Economic and Environmental Geology 2021; 54: 709-716https://doi.org/10.9719/EEG.2021.54.6.709

    Fig 7.

    Figure 7.Isotherm adsorption data of fluoride adsorption onto adsorbent.
    Economic and Environmental Geology 2021; 54: 709-716https://doi.org/10.9719/EEG.2021.54.6.709

    Fig 8.

    Figure 8.The plots of Langmuir(a) and Freundlich(b) isotherm model for fluoride adsorption.
    Economic and Environmental Geology 2021; 54: 709-716https://doi.org/10.9719/EEG.2021.54.6.709

    Table 1 . Chemical composition of adsorbent analyzed by X-ray flourescence(XRF).

    ComponentsComposition (wt.%) ASBA
    Al2O31.82
    SO31.69
    SiO22.58
    MnO1.13
    Fe2O379.2
    CaO9.58
    NiO0.12

    Table 2 . BET surface Comparison between GFH and adsorbent used in this study.

    BET surface area (m2/g)Reference
    Adsorbent used in this study216.78This study
    GFH (Granular Ferric Hydroxide)222.00Kumar et al., 2020

    Table 3 . Thermodynamic parameters for fluoride adsorption onto adsorbent.

    qe (mg/g)△H° (kJ/mol)△S° (J/Kmol)△G° (kJ/mol)
    25℃45℃65℃25℃45℃65℃
    Fluoride4.134.644.927.8723.001.020.560.30

    Table 4 . Langmuir and Freundlich adsorption isotherm constants.

    Langmuir modelFreundlich model
    qmKLRLR2KFnR2
    Fluoride81.010.0130.3940.75581.3551.2160.9138

    Table 5 . The water quality data of the ○○mine drainage (unit: mg·L-1).

    MinepHFMnZnNiCdAlFe
    ○○mine7.412.8376.0500.01-a0

    aBelow detection limit.


    KSEEG
    Apr 30, 2024 Vol.57 No.2, pp. 107~280

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