용액상에 용해되어 있는 이온성 물질에는 중금속, 유가금속, 염료, 이온성액체가 있는데, 이들 이온성 물질들은 환경적인 문제로 제거 해야 할 대상이기도 하면서 일부는 고갈되는 자원으로서 재자원화를 할 필요가 있다. 특히 유가금속의 경우 촉매분야에서 대단히 많이 사용되고 있으나 많은 양이 폐수로 버려지고 있어서 이를 회수하여 재자원화 하는 연구가 최근 활발히 진행되고 있다. 이온성액체는 휘발성이 낮고, 쉽게 분해되지 않으며, 유기용매로 녹이지 못하는 물질을 잘 녹일 수 있는 성질이 있어서 최근 각광 받고 있으나 비싼 가격 때문에 공정 적용에 어려움이 있다. 이러한 이온성 물질들을 제거 또는 회수하기 위하여 생체흡착제 또는 ...
용액상에 용해되어 있는 이온성 물질에는 중금속, 유가금속, 염료, 이온성액체가 있는데, 이들 이온성 물질들은 환경적인 문제로 제거 해야 할 대상이기도 하면서 일부는 고갈되는 자원으로서 재자원화를 할 필요가 있다. 특히 유가금속의 경우 촉매분야에서 대단히 많이 사용되고 있으나 많은 양이 폐수로 버려지고 있어서 이를 회수하여 재자원화 하는 연구가 최근 활발히 진행되고 있다. 이온성액체는 휘발성이 낮고, 쉽게 분해되지 않으며, 유기용매로 녹이지 못하는 물질을 잘 녹일 수 있는 성질이 있어서 최근 각광 받고 있으나 비싼 가격 때문에 공정 적용에 어려움이 있다. 이러한 이온성 물질들을 제거 또는 회수하기 위하여 생체흡착제 또는 이온교환수지를 이용한 흡착기술은 소재 및 운전비용이 낮고, 공정이 단순하기 때문에 매우 효과적이라 할 수 있다. 본 연구에서는 주로 생체흡착제를 이용하여 중금속 및 염료의 제거와 유가금속의 회수, 이온교환수지를 사용하여 이온성액체의 제거에 대한 연구를 수행하였다. 생체흡착제는 발효부산물인 Corynebacterium glutamicum 과 Escherichia coli 그리고 하수슬러지를 사용하였고 PEI를 이용한 표면 개질된 바이오매스와, 다양한 이온교환수지들을 사용하였다. Corynebacterium glutamicum 바이오매스를 사용하여 카드뮴 흡착실험을 수행하였고 카드뮴의 흡착성능 및 실제 적용가능성을 테스트 하여 성공적으로 중금속을 제거할 수 있음을 보였다. 또한 바이오매스에 의한 중금속 흡착 기작을 증명하였으며 제거성능을 예측할 수 있는 모델식을 완성하였다. 첫째, 중금속이 사용된 바이오매스에 의해 제거되는 기작은 두 가지 약 산성 작용기에 의한 Complexation 현상이었다. 알칼리를 이용한 바이오매스의 적정실험을 통해 바이오매스에는 최소한 3가지의 작용기가 있음이 확인되었다. 이중에서 카드뮴이 수산화 침전물을 형성하지 않는 pH 8 이하의 영역에서 카르복실과 포스포네잇 작용기가 카드뮴의 흡착에 관여함을 FTIR과 pH-edge 실험을 통해 알아냈다. 이때 카르복실 작용기의 pK값은 3.57？0.08 이었고, 존재량은 0.32？0.01 mmol/g이었으며 포스포네잇 작용기의 pK 값은 6.90？0.06 이었고, 존재량은 0.56？0.02 mmol/g 이었다. 서로 다른 pH에서 얻은 평형 등온 흡착곡선을 통해 pH가 증가할수록 카드뮴의 흡착성능이 급격히 증가함을 알 수 있었다. 또한 작용기의 양과 중금속과의 흡착계수를 고려한 모델식은 카드뮴의 흡착 등온곡선과 pH-edge곡선을 성공적으로 예측하여 중금속의 제거 기작을 입증하였다. 둘째, 중금속의 결합자리를 증가시켜 중금속 제거 효율을 높이기 위한 연구를 수행하였다. 바이오매스를 산처리 하였을 때 카드뮴의 흡착양이 1.24배 증가하였다. 또한 FTIR과 적정실험을 통해 카르복실 작용기가 1.52배 증가하였음을 확인하여 산처리에 의한 중금속 흡착양의 증가원인은 작용기인 카르복실그룹의 증가가 주된 원인이었음을 밝혔다. 실제폐수에서 루테늄을 회수하기 위하여 PEI-개질된 바이오매스와 원료바이오매스들, 이온교환수지를 비교실험 하였을 때, PEI-개질된 바이오매스의 흡착성능이 매우 높게 나와서, 루테늄 회수를 위한 흡착소재로 적용될 수 있는 가능성을 입증하였다. 이온성액체의 제거에서는 중금속과 염료의 흡착에서 높은 성능을 보였던 표면개질된 바이오매스들과 원료바이오매스들이 낮은 성능을 보였고, 이온교환수지가 높은 흡착성능을 가지고 있음을 보였다. 특히 이온교환수지 중에서 sulphonate을 작용기로 보유한 수지들이 높은 흡착능력이 있음을 보여 주었다. 본 연구를 통해서 흡착기술을 통해 중금속 및 염료, 이온성액체를 제거하고 유가금속을 회수할 수 있음을 보였다. 특히 유가금속 회수의 경우 재자원화 방안으로 응용되어 부가가치를 창출 할 수 있을 것으로 보인다.
용액상에 용해되어 있는 이온성 물질에는 중금속, 유가금속, 염료, 이온성액체가 있는데, 이들 이온성 물질들은 환경적인 문제로 제거 해야 할 대상이기도 하면서 일부는 고갈되는 자원으로서 재자원화를 할 필요가 있다. 특히 유가금속의 경우 촉매분야에서 대단히 많이 사용되고 있으나 많은 양이 폐수로 버려지고 있어서 이를 회수하여 재자원화 하는 연구가 최근 활발히 진행되고 있다. 이온성액체는 휘발성이 낮고, 쉽게 분해되지 않으며, 유기용매로 녹이지 못하는 물질을 잘 녹일 수 있는 성질이 있어서 최근 각광 받고 있으나 비싼 가격 때문에 공정 적용에 어려움이 있다. 이러한 이온성 물질들을 제거 또는 회수하기 위하여 생체흡착제 또는 이온교환수지를 이용한 흡착기술은 소재 및 운전비용이 낮고, 공정이 단순하기 때문에 매우 효과적이라 할 수 있다. 본 연구에서는 주로 생체흡착제를 이용하여 중금속 및 염료의 제거와 유가금속의 회수, 이온교환수지를 사용하여 이온성액체의 제거에 대한 연구를 수행하였다. 생체흡착제는 발효부산물인 Corynebacterium glutamicum 과 Escherichia coli 그리고 하수슬러지를 사용하였고 PEI를 이용한 표면 개질된 바이오매스와, 다양한 이온교환수지들을 사용하였다. Corynebacterium glutamicum 바이오매스를 사용하여 카드뮴 흡착실험을 수행하였고 카드뮴의 흡착성능 및 실제 적용가능성을 테스트 하여 성공적으로 중금속을 제거할 수 있음을 보였다. 또한 바이오매스에 의한 중금속 흡착 기작을 증명하였으며 제거성능을 예측할 수 있는 모델식을 완성하였다. 첫째, 중금속이 사용된 바이오매스에 의해 제거되는 기작은 두 가지 약 산성 작용기에 의한 Complexation 현상이었다. 알칼리를 이용한 바이오매스의 적정실험을 통해 바이오매스에는 최소한 3가지의 작용기가 있음이 확인되었다. 이중에서 카드뮴이 수산화 침전물을 형성하지 않는 pH 8 이하의 영역에서 카르복실과 포스포네잇 작용기가 카드뮴의 흡착에 관여함을 FTIR과 pH-edge 실험을 통해 알아냈다. 이때 카르복실 작용기의 pK값은 3.57？0.08 이었고, 존재량은 0.32？0.01 mmol/g이었으며 포스포네잇 작용기의 pK 값은 6.90？0.06 이었고, 존재량은 0.56？0.02 mmol/g 이었다. 서로 다른 pH에서 얻은 평형 등온 흡착곡선을 통해 pH가 증가할수록 카드뮴의 흡착성능이 급격히 증가함을 알 수 있었다. 또한 작용기의 양과 중금속과의 흡착계수를 고려한 모델식은 카드뮴의 흡착 등온곡선과 pH-edge곡선을 성공적으로 예측하여 중금속의 제거 기작을 입증하였다. 둘째, 중금속의 결합자리를 증가시켜 중금속 제거 효율을 높이기 위한 연구를 수행하였다. 바이오매스를 산처리 하였을 때 카드뮴의 흡착양이 1.24배 증가하였다. 또한 FTIR과 적정실험을 통해 카르복실 작용기가 1.52배 증가하였음을 확인하여 산처리에 의한 중금속 흡착양의 증가원인은 작용기인 카르복실그룹의 증가가 주된 원인이었음을 밝혔다. 실제폐수에서 루테늄을 회수하기 위하여 PEI-개질된 바이오매스와 원료바이오매스들, 이온교환수지를 비교실험 하였을 때, PEI-개질된 바이오매스의 흡착성능이 매우 높게 나와서, 루테늄 회수를 위한 흡착소재로 적용될 수 있는 가능성을 입증하였다. 이온성액체의 제거에서는 중금속과 염료의 흡착에서 높은 성능을 보였던 표면개질된 바이오매스들과 원료바이오매스들이 낮은 성능을 보였고, 이온교환수지가 높은 흡착성능을 가지고 있음을 보였다. 특히 이온교환수지 중에서 sulphonate을 작용기로 보유한 수지들이 높은 흡착능력이 있음을 보여 주었다. 본 연구를 통해서 흡착기술을 통해 중금속 및 염료, 이온성액체를 제거하고 유가금속을 회수할 수 있음을 보였다. 특히 유가금속 회수의 경우 재자원화 방안으로 응용되어 부가가치를 창출 할 수 있을 것으로 보인다.
In this thesis the waste biomass of Corynebacterium glutamicum and Escherichia coli discharged from an industrial fermentation plant, and sewage sludge was used as a new type of biosorbent for the removal and recovery of ionic solutes such as heavy metals, dyes, and precious metals. And ion exchange...
In this thesis the waste biomass of Corynebacterium glutamicum and Escherichia coli discharged from an industrial fermentation plant, and sewage sludge was used as a new type of biosorbent for the removal and recovery of ionic solutes such as heavy metals, dyes, and precious metals. And ion exchange resins also studied for removal of ionic liquids. At first, biosorption of divalent cadmium by the waste biomass of C. glutamicum was studied with assistance of potentiometric titration, FTIR, and some sorption experiments such as isotherms, pH-edge, and kinetics. Within the pH range (pH 3 ？ 6) used in this study, where cadmium does not precipitate, two types of sites (carboxyl groups (pKH= 3.57 ？ 0.08) and phosphonate groups (pKH= 6.90 ？ 0.06)) were found to play a major role in binding protons and cadmium. The equilibrium sorption isotherms determined at different solution pHs indicated that the uptake of cadmium increased significantly with increasing pH. A biosorption model based upon two binding sites was developed. The model was able to predict the equilibrium sorption experimental data at different pH values and cadmium concentrations. In addition, the speciation of the binding sites as a function of the solution pH was predicted using the model in order to visualize the distribution of cadmium present in the aqueous and solid phases. Acid-washed (protonated) biomass showed higher qmax (1.21 times) and b (1.11 times) for cadmium than the raw biomass. Similar enhancements by protonation were observed in biosorption of a cationic dye Methylene Blue (MB). However, qmax and b of Reactive Red 4 (RR 4) biosorption by the protonated biomass were decreased by 0.83 and 0.24 folds, respectively, indicating that protonation is not always a good pretreatment method. From potentiometric titration results, it can be noted that the amount of carboxyl sites increased 1.52 fold after acid washing, although other types of functional groups such as phosphonate and amine sites did not altered. The generation of carboxyl sites was likely due to the cleavage reaction between glycerol and the fatty acid in the cell membrane phospholipids and at the same time, due to the dissolution of salt precipitates embedded in the cell surface. The removal of nickel (II) from wastewater of an electroplating factory was investigated using the waste Escherichia coli biomass as a biosorbent. The results were compared with those from using Amberlite IRN-150 as a commercial sorbent resin. The resin showed better performance with a qmax value of 30.48 mg/g compared to 26.45 mg/g for the biomass, as predicted by the Langmuir isotherm model. Kinetic experiments revealed that the biosorption equilibrium was attained within 15 min. In the recycling of the sorbents, the desorption of nickel (II) from Amberlite was only 50%, which was too low for the adsorption performance of the resin to be maintained at an economic level in subsequent cycles. In contrast, the biomass exhibited reasonable adsorption-desorption performance over three repeated cycles. Adsorption characteristics of sewage sludge are evaluated for the removal of metal ions from polluted waters. A cadmium adsorption model of sludge was studied using adsorption isotherms under batch conditions. From the isotherm data for cadmium, the Freundlich model yielded a better fit than the Langmuir model. Furthermore, potentiometric titrations were performed to determine the concentration of surface functional groups. The titration curve of the sludge was fitted with a model that accounted for both three- and four-conceptual sites, with the four-site titration model yielding a better fit. It can be postulated that one weakly acidic (pKH = 4.43 ？ 0.15) and one neutral (pKH = 6.27 ？ 0.05) group can act as binding sites for cadmium. Regarding proton-cadmium exchange, linear relationships were observed in the slope, with exchange ratios of 0.89 ？ 0.06, 0.82 ？ 0.03 and 0.80 ？ 0.04 at pHs 4, 6 and 7, respectively. From these linear relationships, ion-exchange based mechanisms can be suggested, such as ion-exchange and complexation. The parameters of the Langmuir model revealed that the sludge could uptake 0.282 mmol/g of cadmium at pH 7, which was attributed to one weakly acidic and one neutral functional group. The calculated proton constants were compared with data from the literature. In addition, the speciation of the functional groups, as a function of the solution pH, was predicted in order to visualize the distribution of reactive sites. Evidence from the FT-IR spectra confirmed that the carboxyl groups in sewage sludge act as binding sites for cadmium. Furthermore, the result from the pH edge experiment revealed that phosphonate groups also act as binding sites for Cd2+ ions. The carboxyl and phosphonate groups were found to play a major role in the binding protons and Cd. Using a new approach, the H+/Cd2+ exchange ratio, the binding mechanisms of both the carboxyl and phosphonate groups were established as complexation reactions. Finally, a biosorption model was developed based upon the binding mechanisms, which was successfully used to predict the isotherm and pH edge experiments. Using the developed model equation, the contribution of each functional group on cadmium binding was predicted and visualized. Poly Ethyleneimine (PEI)-modified biomass was used for recovery of ruthenium from industrial wastewater. Raw biomass of C. glutamicum, ion exchange resins such as Amberjet 4200, PEI on silica beads were used for comparing. After the sorbents were contacted with the ruthenium-bearing solution, the ruthenium concentration decreased almost 90% over the initial 50 minutes. Thereafter, the sorption decreased to a very slow rate until approximately 300 minutes. PEIB showed best performance, maximum uptake 64.39 mg/g. The raw biomass of E. coli has maximum uptake 48.71 mg/g and C. glutamicum showed maximum uptake 41.01 mg/g. It is noteworthy that three kind of ion exchange resins (Amberjet 4200, PEI on silica bead, Bayer) showed lower uptake capacity even than raw biomass. Finally, studies to get answer the question if sorption can be used for the removal of ionic liquid, 1-ethyl-3-methylimidazolium acetate from aqueous media have been conducted. Seven types of bacterial biosorbents were prepared from fermentation wastes (Escherichia coli and Corynebacterium glutamicum) through chemical modification of the bacterial surface. Screening study to evaluate the sorption capacity indicated succinic anhydride-modified E. coli biomass (SB-E) was the most powerful among bacterial biosorbents tested. Kinetics, pH-edge, isotherm, and desorption experiments using the selected sorbent SB-E were examined. The sorption kinetics was found to be rapid, with only 10 min required to attain equilibrium. The optimal pH range for the adsorption of EMIM was found from 7.0 to 9.5. The maximum uptake capacity was estimated to be 70.4 mg [EMIM]/g at pH 7.0 by using Langmuir model. Acetic acid, as an eluent, could successfully desorb the EMIM cations, giving a desorption efficiency of over 91.3%. It implies that the bacterial biosorbents can be utilized for the removal and recovery of EMIM cations from aqueous spent media. Ion exchange resins were also used for removal of EMIM cations. The resins which have sulphonate functional groups showed highest sorption abilities range from 580 to 620 mg/g. Bead size and degree of cross linking of resins did not affect to sorption performance of EMIM. Large bead size led to lowered kinetics of EMIM adsorption.
In this thesis the waste biomass of Corynebacterium glutamicum and Escherichia coli discharged from an industrial fermentation plant, and sewage sludge was used as a new type of biosorbent for the removal and recovery of ionic solutes such as heavy metals, dyes, and precious metals. And ion exchange resins also studied for removal of ionic liquids. At first, biosorption of divalent cadmium by the waste biomass of C. glutamicum was studied with assistance of potentiometric titration, FTIR, and some sorption experiments such as isotherms, pH-edge, and kinetics. Within the pH range (pH 3 ？ 6) used in this study, where cadmium does not precipitate, two types of sites (carboxyl groups (pKH= 3.57 ？ 0.08) and phosphonate groups (pKH= 6.90 ？ 0.06)) were found to play a major role in binding protons and cadmium. The equilibrium sorption isotherms determined at different solution pHs indicated that the uptake of cadmium increased significantly with increasing pH. A biosorption model based upon two binding sites was developed. The model was able to predict the equilibrium sorption experimental data at different pH values and cadmium concentrations. In addition, the speciation of the binding sites as a function of the solution pH was predicted using the model in order to visualize the distribution of cadmium present in the aqueous and solid phases. Acid-washed (protonated) biomass showed higher qmax (1.21 times) and b (1.11 times) for cadmium than the raw biomass. Similar enhancements by protonation were observed in biosorption of a cationic dye Methylene Blue (MB). However, qmax and b of Reactive Red 4 (RR 4) biosorption by the protonated biomass were decreased by 0.83 and 0.24 folds, respectively, indicating that protonation is not always a good pretreatment method. From potentiometric titration results, it can be noted that the amount of carboxyl sites increased 1.52 fold after acid washing, although other types of functional groups such as phosphonate and amine sites did not altered. The generation of carboxyl sites was likely due to the cleavage reaction between glycerol and the fatty acid in the cell membrane phospholipids and at the same time, due to the dissolution of salt precipitates embedded in the cell surface. The removal of nickel (II) from wastewater of an electroplating factory was investigated using the waste Escherichia coli biomass as a biosorbent. The results were compared with those from using Amberlite IRN-150 as a commercial sorbent resin. The resin showed better performance with a qmax value of 30.48 mg/g compared to 26.45 mg/g for the biomass, as predicted by the Langmuir isotherm model. Kinetic experiments revealed that the biosorption equilibrium was attained within 15 min. In the recycling of the sorbents, the desorption of nickel (II) from Amberlite was only 50%, which was too low for the adsorption performance of the resin to be maintained at an economic level in subsequent cycles. In contrast, the biomass exhibited reasonable adsorption-desorption performance over three repeated cycles. Adsorption characteristics of sewage sludge are evaluated for the removal of metal ions from polluted waters. A cadmium adsorption model of sludge was studied using adsorption isotherms under batch conditions. From the isotherm data for cadmium, the Freundlich model yielded a better fit than the Langmuir model. Furthermore, potentiometric titrations were performed to determine the concentration of surface functional groups. The titration curve of the sludge was fitted with a model that accounted for both three- and four-conceptual sites, with the four-site titration model yielding a better fit. It can be postulated that one weakly acidic (pKH = 4.43 ？ 0.15) and one neutral (pKH = 6.27 ？ 0.05) group can act as binding sites for cadmium. Regarding proton-cadmium exchange, linear relationships were observed in the slope, with exchange ratios of 0.89 ？ 0.06, 0.82 ？ 0.03 and 0.80 ？ 0.04 at pHs 4, 6 and 7, respectively. From these linear relationships, ion-exchange based mechanisms can be suggested, such as ion-exchange and complexation. The parameters of the Langmuir model revealed that the sludge could uptake 0.282 mmol/g of cadmium at pH 7, which was attributed to one weakly acidic and one neutral functional group. The calculated proton constants were compared with data from the literature. In addition, the speciation of the functional groups, as a function of the solution pH, was predicted in order to visualize the distribution of reactive sites. Evidence from the FT-IR spectra confirmed that the carboxyl groups in sewage sludge act as binding sites for cadmium. Furthermore, the result from the pH edge experiment revealed that phosphonate groups also act as binding sites for Cd2+ ions. The carboxyl and phosphonate groups were found to play a major role in the binding protons and Cd. Using a new approach, the H+/Cd2+ exchange ratio, the binding mechanisms of both the carboxyl and phosphonate groups were established as complexation reactions. Finally, a biosorption model was developed based upon the binding mechanisms, which was successfully used to predict the isotherm and pH edge experiments. Using the developed model equation, the contribution of each functional group on cadmium binding was predicted and visualized. Poly Ethyleneimine (PEI)-modified biomass was used for recovery of ruthenium from industrial wastewater. Raw biomass of C. glutamicum, ion exchange resins such as Amberjet 4200, PEI on silica beads were used for comparing. After the sorbents were contacted with the ruthenium-bearing solution, the ruthenium concentration decreased almost 90% over the initial 50 minutes. Thereafter, the sorption decreased to a very slow rate until approximately 300 minutes. PEIB showed best performance, maximum uptake 64.39 mg/g. The raw biomass of E. coli has maximum uptake 48.71 mg/g and C. glutamicum showed maximum uptake 41.01 mg/g. It is noteworthy that three kind of ion exchange resins (Amberjet 4200, PEI on silica bead, Bayer) showed lower uptake capacity even than raw biomass. Finally, studies to get answer the question if sorption can be used for the removal of ionic liquid, 1-ethyl-3-methylimidazolium acetate from aqueous media have been conducted. Seven types of bacterial biosorbents were prepared from fermentation wastes (Escherichia coli and Corynebacterium glutamicum) through chemical modification of the bacterial surface. Screening study to evaluate the sorption capacity indicated succinic anhydride-modified E. coli biomass (SB-E) was the most powerful among bacterial biosorbents tested. Kinetics, pH-edge, isotherm, and desorption experiments using the selected sorbent SB-E were examined. The sorption kinetics was found to be rapid, with only 10 min required to attain equilibrium. The optimal pH range for the adsorption of EMIM was found from 7.0 to 9.5. The maximum uptake capacity was estimated to be 70.4 mg [EMIM]/g at pH 7.0 by using Langmuir model. Acetic acid, as an eluent, could successfully desorb the EMIM cations, giving a desorption efficiency of over 91.3%. It implies that the bacterial biosorbents can be utilized for the removal and recovery of EMIM cations from aqueous spent media. Ion exchange resins were also used for removal of EMIM cations. The resins which have sulphonate functional groups showed highest sorption abilities range from 580 to 620 mg/g. Bead size and degree of cross linking of resins did not affect to sorption performance of EMIM. Large bead size led to lowered kinetics of EMIM adsorption.
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