초록 ▼

개발결과 요약
연차목표
▪ 스트론튬 선택성 흡착제 성능 향상화 기술 개발
- 스트론튬 선택성 흡착제의 흡착 성능 및 선택성 향상 기술
- 스트론튬 선택성 흡착제의 해수 내 물성 개선
- 해수 중 방사성 스트론튬 함량 분석 및 방사성 스트론튬 제거 적용연구
▪ 해수 용존 스트론튬 농축 기술 개발 및 공정 설계
- 스트론튬 농축 요소기술 개발
- 고효율 스트론튬 농축 공정설계
▪ 해수 추출 스트론튬 불순물 제어 기술 개발
- 해수 스트론튬 추출물 불순물 규명
- 추출물의 성

개발결과 요약
연차목표
▪ 스트론튬 선택성 흡착제 성능 향상화 기술 개발
- 스트론튬 선택성 흡착제의 흡착 성능 및 선택성 향상 기술
- 스트론튬 선택성 흡착제의 해수 내 물성 개선
- 해수 중 방사성 스트론튬 함량 분석 및 방사성 스트론튬 제거 적용연구
▪ 해수 용존 스트론튬 농축 기술 개발 및 공정 설계
- 스트론튬 농축 요소기술 개발
- 고효율 스트론튬 농축 공정설계
▪ 해수 추출 스트론튬 불순물 제어 기술 개발
- 해수 스트론튬 추출물 불순물 규명
- 추출물의 성질 별 불순물 제어 기술 개발

개발내용 및 결과
▪ Alginate 복합체 제조 및 특성평가
MnO₂-alg. bead, zeolite-alg. foam
Alg-Fe₃O₄ 복합체: 65.4 mg/g (DI water base), 12.4 mg/g (해수 base)
[Sr]=50ppm
▪ MnO₂-자성복합체 성능 최적화, Sr 흡착능: 42 mg/g (DI water base)
⁹⁰Sr 제거율: 82 % (농도=100 Bq/L)
▪ Zeolite계열 흡착제 적용연구 (Zeolite-W vs. Clinoptilolite)
▪ 고효율 흡착시스템 개발
[zeolite 4A-alginate foam 및 zeolite 4A-PVdF membrane적용, pressurized column system, MCDI (membrane capacitive deionization) system]
▪ Batch type 자력분리 반응기(5 L) 개발(MnO₂-자성복합체, 해수 Sr 회수공정)
▪ 해수 Sr 탈착 및 농축공정 개발(해수 Sr 농축액 농도 : 501 ppm)
▪ 농축액 분리/정제 기술 개발(Hydroxide 침천을 통한 Ca, Mg 제거)
▪ 스트론튬 화합물 제조(SrCO₃ 제조, 순도 99%)

기대효과
▪ 스트론튬의 새로운 수급체계 확보에 따른 관련 산업의 안정적 발전에 기여
▪ 스트론튬 회수 원천기술을 확보, 향후 성장 가능한 미래소재시장 선점
▪ 새로운 산업의 육성으로 인력 고용 효과 유발
▪ 다양한 해수용존 유용자원 회수기술개발을 위한 기반기술 활용

적용분야
▪ 해수 추출 스트론튬의 국내산업 활용
▪ 개발된 스트론튬 회수 기술(흡착/회수 공정모델)을 다양한 해수용존 유용금속 회수공정에 확대 응용
▪ 방사성 스트론튬 제거 및 회수공정에 확대 응용

Abstract ▼

Strontium (Sr) which has many industrial applications such as ferrite magnet,ceramic, and fire works exists in seawater with the concentration of approximately 7mg/L. In previous report estimating economic potential on recovery of various elements from seawater in terms of their commercial values an

Strontium (Sr) which has many industrial applications such as ferrite magnet,ceramic, and fire works exists in seawater with the concentration of approximately 7mg/L. In previous report estimating economic potential on recovery of various elements from seawater in terms of their commercial values and concentrations in seawater, Sr locates upper than approximate break-even line, which implies Sr recovery from seawater can be potentially profitable. Recently, Sr separation from seawater has received great attention in the environmental aspect after Fukushima Nuclear Power Plant (NPP) accident which released much amount of radioactive Sr and Cs. Accordingly, the efficient separation of radioactive elements released to seawater has become critical as an important technological need as well as their removal from radioactive wastes.

So far, it has been introduced to separate Sr from aqueous media by various methods including solvent extraction, adsorption by solid materials, and ion exchange. Among them, the adsorption technique using solid adsorbents is of great interest for selectively separating Sr from seawater with respect to low concentration level of Sr. Herein, we report Sr recovery from seawater using various kinds of adsorbents.

Zeolite 4A has been known as an excellent adsorbent for strontium ion with its high ion exchange capacity (~160 mg/g). However, the powder type adsorbent has the drawbacks for the practical use in adsorption process, in which it is difficult to recover the zeolite powder after the use in adsorption process. For its practical application, the formulation methods has been developed using binder, in which alginate-zeolite foam and/or zeolite-PvdF (polyvinyliden fluoride) membrane were applied into pressurized column system and MCDI (membrane capacitive deionization) system, respectively.

Alginate bead which investigated in previous research is promising strontium(Sr) adsorbent but its low mechanical strength and Sr adsorption capacity decrease in seawater due to highly concentrated ions are drawbacks to apply this adsorbent in practical Sr recovery in seawater. In this study, we investigate alginate composite with other material to overcome those disadvantages. Alginate/Fe₃O₄ composite includes high alginic acid content(10 wt%) to prevent destruction caused by swelling of alginate in seawater. Also Fe₃O₄ induced magnetic property in composite, and then it is possible to recover adsorbent by magnetic separation.

MnO₂-alginate bead is synthesized by immobilizing δ-MnO₂ into alginate bead. Becauseδ-MnO₂ is also excellent Sr adsorbent as well as alginate bead, the number of Sr adsorption site is increased and Sr selectivity against Na is also improved. It exhibited 4 times higher Sr adsorption capacity compared with plain alginate bead in real seawater.

Zeolite-alginate foam is flexible foam type adsorbent which provides mechanical stability and zeolite 4A is immobilized on alginate foam to improve Sr adsorption capacity. It exhibited improved distribution coefficient(K_d) than pure alginate foam which proves that Zeolite-alginate foam is highly Sr selective material.

A magnetic composite adsorbent with core-shell structure (MnO₂@C@Fe₃O₄) was synthesized by simply mixing with C@Fe₃O₄ and KMnO₄ solution. MnO₂@C@Fe₃O₄ composites enable to easily separate solids from liquid in the reaction suspension by inducing external magnetic force. This can be critical factor to enhance the overall efficiency of metal recovery process. Sr adsorption by MnO₂@C@Fe₃O₄ was in good agreement with Langmuir isotherm model, and well matched with pseudo-second-order kinetic model. Regeneration of MnO₂@C@Fe₃O₄ could be completed by HCl treatment.

Clinoptilolite has been demonstrated to be the most appropriate sorbent for radioactive strontium removal from wastewater and strontium recovery from seawater,as well as from brine. This most common zeolite is characterized by the composition(Na, K)₄CaAl₆Si₃₀O₇₂·24H₂O. This zeolite is inexpensive and widely available sorbents that should be employable for strontium recovery. The main advantages of applying clinoptilolite is attributed to the ease with which it is regenerable by ammonium salts. However, the purity and morphological properties of natural zeolite could affect largely on the Sr adsorption properties.So, w-type zeolite (15K₂O:12SiO₂:Al₂O₃:445H₂O), synthesized by microwave reactor, and two types of clinoptilolite (C-1(紅沸石), C-2(靑沸石), Hebei Chuangsen Technology) were applied for Sr recovery from seawater. Synthetic zeolite represented the rod shape with several hundreds of diameter. These zeolite showed a high adsorption capacity for Na, K ions and a high selectivity for Sr, K ions in seawater. Finally, the all applied zeolite demonstrated the Sr adsorption uptakes less than 1 mg/g.

To extract Sr from real seawater, adsorption-desorption experiments were repeated by using MnO₂@C@Fe₃O₄ adsorbents and a reactor equipped with electromagnets. Sr concentrate of 501 mg/L was made by using 0.5 M HCl after 8^th cycle repetition.

In the seawater extracted Sr concentrated eluent, high concentration of Ca and Mg are also co-existing. To obtain purified Sr compound, Ca and Mg removal process is needed. In this research, Mg and Ca is removed by following step. 1) Hydroxide precipitation: Mg is completely removed, Ca is partially removed. 2) Sulfate precipitation: In Ca/Sr mixed solution, only Sr is precipitated as SrSO₄ form as 95% purity. This compound is converted to SrCO₃ which is widely used form in industrial applications. To convert SrCO₃, SrSO₄ extracted from seawater is 1) dissolved in 1 M NaCl solution, 2) Na₂CO₃ is added in solution to make precipitate SrCO₃. The purity of final product is 99%.

목차 Contents

• 표지 ... 1제 출 문 ... 2최종보고서 요약서 ... 4요 약 문 ... 6SUMMARY ... 9CONTENTS ... 11목차 ... 12제 1 장 연구개발과제의 개요 ... 14 제 1 절 연구개발의 목적 및 필요성 ... 14 1. 기술개발 목적 및 필요성 ... 14 2. 기술개발 개요 ... 15 제 2 절 연구개발 범위 ... 15 1. 최종목표 ... 15 2. 당해 연도 연구개발내용 ... 16제 2 장 국내외 기술개발 현황 ... 17 제 1 절 국내의 경우 ... 17 제 2 절 국외의 경우 ... 17 제 3 절 기술개발 현황 ... 18제 3 장 연구개발수행 내용 및 결과 ... 20 제 1 절 제올라이트(Zeolite) 4A 흡착제 ... 20 1. Na-A 제올라이트 성형화 및 흡착시스템 ... 20 제 2 절 알긴산염(Alginate) 기반 바이오 흡착소재 ... 25 1. 연구배경 ... 25 2. 연구방법 ... 25 3. 연구결과 및 토의 ... 27 제 3 절 MnO2 자성 복합체(MnO2@C@Fe3O4) ... 47 1. 연구배경 ... 47 2. 연구방법 ... 48 3. 연구결과 및 토의 ... 49 제 4 절 Synthetic zeolite (W-type) 및 clinoptilolite ... 58 1. 연구배경 ... 58 2. 연구방법 ... 58 3. 연구결과 및 토의 ... 59 제 5 절 전기화학적 흡착반응을 통한 Sr 선택성 향상화 ... 62 1. Titanate nanotube 전극이용 전기인가 Sr 흡착성능 평가 ... 62 제 6 절 해수추출 스트론튬 농축공정 ... 77 1. 연구배경 ... 77 2. 연구방법 ... 77 3. 연구결과 및 토의 ... 77 제 7 절 해수추출 스트론튬 분리/정제 및 화합물 제조 기초기술 ... 81 1. 농축액 분리/정제 기술개발 ... 81 2. 스트론튬 화합물 제조 ... 87 제 8 절 해수 중 방사성스트론튬(90Sr) 제거 연구 ... 90 1. 연구배경 ... 90 2. 연구결과 및 토의 ... 98제 4 장 목표달성도 및 관련분야에의 기여도 ... 119제 5 장 연구개발결과의 활용계획 ... 120제 6 장 참고문헌 ... 121끝페이지 ... 124