연마폐수의 생태독성 저감 및 폐인쇄회로기판으로부터 귀금속의 침출 향상을 위한 흡착 연계 기술

강지혜 전북대학교 일반대학원 2021 국내석사

This thesis was to confirm the possibilities of the sorption-coupled technologies: (i) Reduction of ecotoxicity in milling wastewaters, and (ii) Enhancement of leaching of valuable metals from waste printed circuit boards (WPCBs). In chapter 3, sorption was applied to the control of the ecotoxicity of industrial effluents. It is difficult to reduce the ecotoxicity of industrial effluents by the conventional wastewater treatment process. The objectives of chapter 3 are to identify the substances responsible for ecotoxicity in a milling wastewater and to find appropriate sorbents to reduce the ecotoxicity effectively. The ecotoxicity was measured on the basis of survival of Daphnia magna. Through the coagulation and flocculation processes, the toxic unit (TU) of the milling wastewater (14.9) was reduced to 4.1. Then, the adsorption process was applied to decrease the TU to less than 1 to meet the industrial wastewater discharge standards (the Ministry of Environment of South Korea). Two ion exchange resins, D113 (cation) and D201 (anion), were selected and used for the removal of ionic species. However, adsorption by these resins could not reduce significantly the ecotoxicity. When activated carbon, as an adsorbent for neutral species, was used, all D. magna could survive, indicating TU of 0. The result implies that substances responsible for ecotoxicity are likely neutral species. In order to identify the responsible neutral species, HPLC analysis was conducted. Several peaks appeared and these peaks were correlated with TU. As a result, two peaks were found to be closely related to TU. In this study, appropriate adsorbents were selected based on the substances responsible for ecotoxicity, and by using the adsorbents, the ecotoxicity could be successfully reduced down to zero. In chapter 4, sorption was coupled with the leaching process. Gold is a valuable metal and used in various industries; however, it has a limited reserve. Thus, a friendly economic extraction process is required to develop for the fulfillment of its different uses. Waste printed circuit boards (WPCBs) contain a greater amount of gold as compared to ores. From WPCBs the gold can be recovered using the leaching method. However, the highly toxic leaching agents (e.g. cyanide) were used to recover Au. In this study, we report the development of the sorption-enhanced leaching process using mild leachant (diluted aqua regia) and anion exchange resin (Amberjet 4200). It is hypothesized that if the leached gold species were removed from the solution by adsorption, the forward reaction of leaching can be enhanced, whereas the backward reaction can be depressed. Therefore, the leaching efficiency could be enhanced by coupling with adsorbents. During leaching reaction, in presence of Amberjet 4200, the total amount of gold was found to be 3.38 times higher than in absence of it. Furthermore, it was found that the sorption-coupled leaching could be effective even with mild leachant (e.g. diluted aqua regia). The result indicates that sorption-enhanced leaching could be possible and might replace the conventional leaching methods. In overall, various sorption-coupled technologies deserve further development.

Modeling of sorption, degradation and transport of bacteria and organic contaminant in saturated quartz sand

이순재 Graduate School, Korea University 2013 국내박사

Various reaction processes related to the fate of contaminant in the underground system are studied using modeling approach. First of all, sorption of organic contaminant on solid material was investigated. New method for determination of parameters for the equilibrium/kinetic sorption of organic contaminant was developed using analytical solution of two-site sorption model (TSPI) which assumes to occur fast sorption contaminant on type-1 site and slow rate-limiting sorption on type-2 site. Applying the new method to the experimental data, more parameters could be obtained than applying the solution of the existing three-stage sorption model. The two-site sorption model (TSPI) was compared with another type of two-site model (TSSI) which assumes that the slow rate limiting sorption occurs between Type-1 site and Type-2 site. Application of these two models to a batch system resulted in an identical type of C–t relationship. Model parameters such as distribution coefficient and retardation factor estimated by fitting the analytical solutions of the C–t relationship to the kinetic sorption data well coincided. However, due to differences in the definition of liquid concentration (C+0) at t = +0, some of the parameters deviated from each other. Therefore, care should be taken in the selection of the first-order sorption kinetics of the two site model when modeling reactive solute transport in a porous medium, since the fraction is closely related to the retardation phenomenon. The bacterial sorption on solid matrix was also investigated especially on the effect of the variation of ionic strength. Effect of the perturbation of ionic strength on attachment of bacteria was investigated by imposing various leaching solutions with different ionic strengths after bacterial pulse in the column tests. By monitoring ionic strength of the effluent solution, effect of ionic strength on the dynamic bacterial attachment/detachment during transport was clearly shown. Results have shown that bacterial attachment could be categorized by two main mechanisms. One is the physical factor such as deposition caused by the interaction between sand surface and bacteria, and the second is chemical factor such as attachment onto quartz sand by DLVO interaction. The chemical attachment could be divided into the reversible fraction in secondary energy minimum and irreversible fraction in primary energy minimum by replacing leaching solution with that of lower ionic strength. The interaction energy between bacteria and sand surface calculated by classical DLVO model explains (1) that the chemical deposition in MSM condition was occurred in the primary energy minimum, (2) that the reversibility of the bacterial attachment is due to the separation of the secondary minimum from the primary minimum by lowering ionic strength, (3) and that part of the cells could be retained in the primary minimum in spite of leaching with low ionic strength solution. Bacterial BTC test performed under low, high and perturbed ionic strength condition of leaching solution showed different degree of retardation, attenuation and tailing. These phenomena support the effect of ionic strength on bacterial sorption process. The sorption type of bacteria during transport through sand column was described with eight different types of sorption. The results showed that equilibrium, kinetic reversible and kinetic irreversible sorption processes were occurred in all conditions. Thus, transport model including all the three sorption type is the most appropriate. Depending on the given condition of ionic strength, the contributions of each process were different. Under low ionic strength condition, kinetic reversible and irreversible process had large contribution while equilibrium process had insignificant contribution. Under high ionic strength condition, the three processes contributed significantly. Under perturbed ionic strength condition, kinetic reversible process contributed dominantly and the others had small contribution. Therefore, care should be taken for selection of an appropriate bacterial transport model with regard to sorption types when modeling under various conditions of particle, bacteria, and leaching solution interactions. In the presence of bacteria, the fate of contaminant is affected by more complex processes. To describe the fate of contaminant and bacteria, a model of bacteria associated transport for toluene was developed by accounting for kinetic reactions for biosorption and biodegradation as well as sorption on solid material. This model assumes fully kinetic processes for sorption, biosorption and degradation of contaminant, sorption, growth and decay of bacteria. The developed model could explain the attenuation and significant tailing of toluene BTC in the presence of bacteria reported by Chung et al.(2011). Analysis for the composition of the effluent solution exhibited that the microbial activity during the transport of toluene in the presence of bacteria was related to the processes of biodegradation and biosorption. The mass loss of toluene was mostly attributed by sorption process and followed by the biodegradation. The tailing of the BTC of toluene was attributed to the sorption of toluene onto bacterial cells and the retarded transport of bacteria. At last, I proposed a new method for estimation of the first-order degradation rate coefficient q which is essential for determination of the first-order degradation kinetics q-S relation. The new method is based on the time segment method (TSM) where several q values are calculated from the q-S data for each measured time step. The q-S relation obtained from the TSM was compared with that obtained from straight-line method (SLM) where q is calculated from the slope of ln(S/S0) vs. time data. Three different inhibitory kinetic models (Haldane, Yano, Edward) were applied to the q-S relation for parameter estimation. TSM offered a better prediction of phenol degradation than SLM, and Edward model gave the best results compared to other models.

Sorption of sulfathiazole by giant miscanthus-derived biochar amended agricultural soils

김현정 Graduate School, Korea University 2017 국내석사

Biochar is an effective sorbent for the sorption of organic pollutants because of its carbon-enriched structure, large surface area, and various hydrophilic functional groups. Application of biochar on contaminated sites has received great attention for the restoration of contaminated soil environments in recent years. Sulfonamides (SAs) are among the most frequently detected antibiotics in terrestrial environment and thus pose a potential risk of enhancing antibiotic resistance in bacteria. The behaviors of SAs in soil environments need to be understood to mitigate their adverse effects and the related risks to human health. Sulfathiazole (STZ) was chosen as the model chemical because it is the most dominantly and widely used agronomic among SAs in Korea. The aim of this study was to investigate to the effect of biochar-amendment on the sorption of STZ by biochar-amended soils. The biochar was manufactured from Giant-Miscanthus at two pyrolysis temperatures: 400℃ and 700℃ (labeled GMC-400 and GMC-700, respectively). The sorption isotherm experiments were conducted at pH 5 and pH 7 and the data was fitted with the Freundlich model (FM). Upon attaining sorption equilibrium, desorption studies were conducted on selected samples and the sorption-desorption hysteresis (H) index was estimated. The organic carbon-normalized sorption coefficient Koc was calculated to assess the impact of organic carbon domain for the sorption of STZ. The magnitude of the sorption coefficient (Kd*) of soils amended with GMC-400 (3.96-9.96 L kg-1) was higher than those amended with GMC-700 (1.27-3.38 L kg-1). The sorption capacity of GMC-400-amended soils increased significantly by up to 76.94% with the aging period increasing from 0 to 6 months, whereas no statistical difference was observed in soils amended with GMC-700 during the 6 month period. Results of FTIR and SEM-EDX revealed that the O-containing functional groups of the GMC-400-amended soil increased and the micropores of GMC-700 were deformed. This suggested that the main interaction mechanism between STZ and biochar was hydrogen bonding. The sorption of STZ on biochar-amended soils was pH-dependent in the order pH 2 (92.30 and 64.00 mg kg-1) > pH 5 (65.51 and 42.46 mg kg-1) > pH 7 (46.37 and 24.09 mg kg-1). The H index from the desorption study increased with aging, due to the enhanced sorption sites. The results of this study demonstrate that Giant Miscanthus-derived biochar produced at low temperature (e.g., 400℃) can be applied to soils to enhance the magnitude of STZ sorption by natural soils, thereby effectively reducing the mobility of STZ released from livestock farming sites. 바이오차는 다양한 작용기와 넓은 비표면적을 가지며 탄소를 다량 함유하고 있는 물질로, 환경 중 유기오염물질에 대하여 효과적인 흡착능을 가지고 있다. 이러한 이유로 오염물질을 흡착하는 토양개량제로 주목받고 있고, 관련 연구가 활발히 진행되고 있다. 설폰아마이드는 가축의 질병 예방을 목적으로 널리 사용되는 항생물질이다. 그러나 이 항생물질은 생분해성이 낮아 환경 중에서 오랜 시간 동안 잔류하는 것으로 보고되고 있다. 특히 축산폐수가 처리되지 않고 방류되거나 가축 분뇨 퇴비로 사용 후 수계로 유출된다. 이렇게 환경 중 잔류하는 설폰아마이드는 항생제 내성 병원균을 발생시키고 생태계와 인간을 위협하는 등 문제를 일으킨다. 따라서 이들 물질의 관리에 대한 연구가 필요한 실정이다. 본 연구에서는 바이오차가 토양에 투여 되었을 때 오염물질에 대한 흡착 특성 평가를 목적으로 한다. 특히, 바이오차의 열분해 온도와 숙성 기간에 따른 토양 표면 변화를 관찰하고, 토양용액의 pH 변화가 항생제 종분화와 흡착 거동에 미치는 영향을 평가하였다. 이를 위해 토양의 평균 pH 범위에 속하는 pH 5와 pH 7에서 등온 흡착식 측정실험을 진행하고, Freundlich 등온 흡착식을 적용하였다. 대상 물질로는 대표적인 설폰아마이드계 항생물질인 설파디아졸을 선정하였다. 바이오차의 원료로는 거대억새를 사용하였으며 400℃, 700℃에서 열분해 시킨 후, 토양에 5%의 비율(w/w)로 혼합하여 야외에서 0개월, 3개월, 6개월 동안 숙성 기간을 거쳤다. 설파디아졸에 대한 바이오차의 흡착능력은 열분해 온도, 숙성 기간, 용액 pH에 영향을 받았다. 열분해 온도에 따른 바이오차는 400℃ (3.96-9.96 L kg-1) 가 700℃ (1.27-3.38 L kg-1) 보다 높은 흡착능력을 보였다. 용액 pH에 따라서는 pH 2 (92.30 and 64.00 mg kg-1) > pH 5 (65.51 and 42.46 mg kg-1) > pH 7 (46.37 and 24.09 mg kg-1) 순이었다. 특히, 700℃와 달리 400℃ 바이오차는 토양에서의 숙성기간이 지날수록 설파디아졸에 대한 흡착능력이 최대 76.94% 까지 증가하였다. 이는 숙성기간에 따라 바이오차 표면이 산화되어 산소를 포함한 작용기의 증가로 인한 것이며 FTIR과 SEM-EDX 분석을 통하여 이를 확인했다. 반면에 700℃ 바이오차는 높은 열분해 온도로 인하여 공극의 대부분이 파괴되었고, 숙성기간에 따른 표면 변화가 적었다. 결과적으로 STZ와 바이오차 사이의 주된 결합이 수소결합이라는 것을 의미하였다. 추가적으로 흡탈착 hysteresis를 평가하여 숙성기간을 거친 바이오차가 탈착에 대한 저항력 또한 높은 것을 확인했다. 본 연구결과들을 토대로 종합할 때, 낮은 온도에서 열분해 된 거대억새 유래 바이오차는 토양에 개량되어 오랜 기간 동안 STZ의 안정화에 대하여 우수한 효과를 보인다.

자연 토양과 퇴적물의 Black Carbon에 대한 다환방향족탄화수소(PAHs)의 흡착 및 탈착 특성 : Sorption and Desorption Behaviors of Polycyclic Aromatic Hydrocarbon on

쳔민펑 경북대학교 대학원 2007 국내석사

Contaminant distribution is integral to environmental evaluations of contaminated sediments and soil on every level. Serious health concerns arise when polycyclic aromatic hydrocarbons (PAHs) are present as environmental pollutants due to their carcinogencity and mutagenicity. To fully assess sorption of hydrophobic organic compounds in natural soil and sediment system is still challenging despite the attention it has received over the years. In addition to the complexity of sediments or soils, several factors relevant to the role of black carbon in sorption of hydrophobic organic compounds in various environmental systems contribute to such difficulties. Note that for the purposes of this research, black carbon (BC) is defined as carbonaceous materials including soots, chars, charcoal, coke as well as coal and kerogen. The heterogeneity of black carbon, the diverse origins of black carbon as well as the lack of standardization in definition, identification, and analytical techniques are the factors contributing to difficulties in fully understanding sorption processes. A wet chemical oxidation method was used for isolation and quantification of BC. The various chemical-treatment steps of the BC isolation procedure have potential to impact on BC surface and adsorptive properties. Sorption and desorption characteristics of PAHs in black carbon isolated from natural soil and various lake-sediments were investigated. Black carbon show higher distribution coefficient than predicted based on dissolution of PAH in untreated soil and sediments. Lake sediment black carbon shows higher sorption capacity and more nonlinearity than original sediment on sorption isotherm; it is different form natural soil black carbon, natural soil black carbon shows smaller sorption capacity than untreated soil. It was the result of the difference on BET surface and organic carbon content. In terms of R2 values, MTCFOKM was the best fitting the data in both sorption and desorption kinetics. In addition, the Langmuir model was the best fitting the data in sorption isotherm. To characterize the difference of desorption-resistance in soil/sediment and black carbon, cyclic sorption/desorption studies were conducted. Effect of contact time on sorption isotherm of PAHs was investigated. The results indicated the sorption constant increased as the contact time increased, but the nonlinearity N decreased as the contact time increased. The increase in sorption was attributed to contact time. Effect of initial concentration on the sorption and desorption behaviors of PAHs was also investigated. Sorption and desorption constants were decreased as initial concentration increased. Effect of aging time on desorption kinetics on original soil/sediments and black carbon were also investigated. The desorption equilibrium concentration in solid phase, desorption constant and desorption resistance of PAHs increased consistently with the increasing aging time.

(A) bioassay-based approach for the determination of benzalkonium ion distribution coefficients between water and soil components

Mlamuli Ndabambi Graduate School, Korea University 2019 국내박사

Chemical risk assessment requires reliable models to describe the environmental fate of chemicals. Special attention should be given to those chemicals known to be bioactive and also have high production volumes. Benzalkonium compounds are one such group of chemicals, designed to be biocidal and also produced in large volumes due to their widespread use in industrial, domestic and agricultural applications. Although benzalkonium compounds present a risk to terrestrial and aquatic ecosystems, there are no suitable models to describe their environmental fate. One of the reasons for the absence of reliable models is the unavailability of suitable analytical techniques to measure free concentrations of benzalkonium compounds at environmentally relevant levels. Since benzalkonium compounds are solids at environmental temperatures, their distribution will be confined to water and soils. Novel approaches are therefore, required to determine benzalkonium ion distribution coefficients between water and soil components. This study reports on a bioassay-based method for the determination of benzalkonium ion distribution coefficients between water and soil components. A standardized algal growth inhibition test using Pseudokirchneriella subcapitata was modified by including sorbents in the culture medium. The nominal median inhibitory concentrations obtained in sorbent free medium were subtracted from those obtained from media with sorbents in order to estimate the sorbed concentrations. A toxicokinetic model was then used to compute free concentrations after accounting for the chemical sorbed to algal cells. Sorption to soil components accounted for over 80% of the initial spiked amount. The algal growth inhibition assay was sufficiently sensitive to allow distribution coefficients to be determined at free concentrations below 1 µmol L-1 and sorbed concentrations that were below 10% of the sorbent cationic exchange capacity. These values are within the range of reported environmental concentrations. The developed method was used to determine distribution coefficients for peat, kaolinite and montmorillonite. When distribution coefficients were corrected for each sorbent’s cation exchange capacity, the computed distribution coefficients for each compound were all within one order of magnitude. It was also noted that at low sorbate loadings, van der Waals interactions between the neutral organic surfaces on peat and the alkyl chains of benzalkonium ions did not make a significant contribution to sorption. Therefore, at environmentally relevant concentrations sorption to the tested soil components was attributed to charge-charge interactions between the cationic sorbate and negatively charged sorbent surfaces. However, there was a strong positive correlation between the computed distribution coefficients and the length of the alkyl chain of the benzalkonium ion. This correlation was attributed to the increase in hydration energy with molecular weight of the ion. Higher hydration energies favor the partitioning of cations away from the aqueous phase. This was further explained by computing sorption energies of each ion and comparing them with hydration energies of a homologous series of alkanes. This study also developed a method to calculate the distribution coefficients for soils of a known composition. Since the magnitude of the distribution coefficient was determined by both length of the alkyl chain and the sorbent cation exchange capacity, the model considers the two parameters in predicting sorption coefficients. Although the developed model is not suitable for the 16 and 18 carbon alkyl chain homologues, it does cater for the most popular homologues (C12 and C14) in most commercial formulations and the environment. 화학물질의 위해성평가를 위하여 화학물질의 거동에 대한 정확한 정보가 필요하다. 벤잘코늄 화합물은 세정제 및 살생물제로 널리 사용되고 있으며 수계와 토양으로 배출된다. 이로 인해 거의 모든 환경매체에서 벤잘코늄 화합물이 검출된 바 있다. 벤잘코늄은 살생제로 널리 쓰이는 물질이므로 환경중으로 배출되었을 때 본질적으로 악영향을 미칠 우려가 있다. 그럼에도 아직까지 벤잘코늄 이온의 환경 중 분배를 설명하기에 적합한 신뢰성이 있는 모델이 개발되어 있지 못하다. 특히 환경 중 잔류수준에서의 자유농도를 측정하기 위한 적절한 분석기법이 개발되지 못한 것도 한 원인이다. 그러므로 물과 토양 성분 사이의 벤잘코늄 이온의 평형 분배계수를 결정하는 새로운 접근법이 필요하다. 본 연구는 물과 토양 성분 사이의 벤잘코늄 이온의 분배 계수를 결정하기 위한 새로운 생물학적 기법을 제시한다. Pseudokirchneriella subcapitata를 이용한 표준 조류성장저해 시험에 벤잘코늄 이온을 수착할 수 있는 매질을 배지에 넣는 방법을 통해 분배계수를 얻을 수 있도록 변형하였다. 수착된 농도를 계산하기 위하여 수착매질이 없는 배지에서 얻어진 반수영향농도(EC50)와 수착매질이 포함된 배지에서 얻어진 EC50 값의 차이를 구하였다. 이 차이와 독성동태학적 모델 (toxicokinetic model)을 이용하여 조류 세포에 수착된 벤잘코늄 이온의 양을 고려한 후 자유농도를 계산하였다. 새로운 생물검정법은 민감도가 매우 높아 1 μmol L-1 이하의 자유농도와 수착제 양이온 교환 용량의 10% 미만이 수착된 수준에서 분배 계수를 결정할 수 있었다. 개발된 기법을 활용하여 토탄, 카올리나이트 및 몬트모릴로나이트에 대한 분배계수를 결정하였다. 각각의 수착제에 대한 분배계수를 양이온 교환용량으로 보정하면, 개별 화합물에 대한 얻어진 분배계수는 모두 큰 차이가 없는 것으로 나타났다. 또한 토탄 분배계수는 점토 분배계수와 비슷한 것으로 나타났다. 이는 환경 농도 수준에서 토탄의 소수성 표면이 수착과정에서 중요한 역할을 하지 않음을 의미하며 토양 성분에 대한 수착은 주로 양이온 교환으로 인한 것으로 생각된다. 알킬사슬의 길이에 따라 분배계수가 증가하는 것으로 나타났으며, 이는 알킬사슬의 길이 증가에 따라 요구되는 수화에너지가 커지는 것에 기인한 것으로 볼 수 있다. 이를 바탕으로 벤잘코늄 이온의 알킬사슬 길이와 토양구성성분을 고려한 분배계수 예측모델을 제안하였다. 이 모델은 알킬사슬의 길이가 16 및 18인 동족체에는 적합하지 않지만 대부분의 상업용 제제 및 환경에서 가장 많이 검출되는 동족체 (C12 및 C14)의 분배 계수를 설명하기에 충분하였다.

투수성 반응벽체 기술을 이용한 중금속(아연, 니켈)오염 지하수 처리

최경일 경북대학교 대학원 2011 국내석사

In this study, sorption of Zinc and Nickel onto various kinds of adsorbents such as Iron Oxide Coated Sand(IOCS), Manganese Oxide Coated Sand(MnCS), nano Hydoxyapatite(HAP), Phosphate-Modified Montmorillonite(PMM), Fishbone was estimated as a preliminary study for the application of it in the Permeable Reactive Barrier(PRB) to treat Zn and Ni concentrated groundwater(GW). The effect of salinity and humic acid on the sorption of Zn and Ni on to sorbent was investigated. The experimental data were fitted to several isotherm models such as Langmuir, Freundlich, Dubinin-Radushkevich, Sips, Redlich-Peterson, Kargi-Ozmihci, and Khan models to characterize sorption behaviors. In the single-solute sorption isotherms, the maximum sorption capacity in Langmuir model(qmL) for Zn at 0‰ salinity in the order of was IOCS(0.008 mmol/g) < MnCS(0.012 mmol/g) < PMM(0.314 mmol/g) < fishbone(0.456 mmol/g) < nano HAP(0.727 mmol/g); and at 30‰ salinity was IOCS(0.006 mmol/g) < MnCS(0.006 mmol/g) < PMM(0.147 mmol/g) < fishbone(0.362 mmol/g) < nano HAP(0.474 mmol/g). Similarly, sorption capacity of Ni at 0‰ salinity is the order of was IOCS(0.003 mmol/g) < MnCS(0.006 mmol/g) < PMM(0.383 mmol/g) < fishbone(0.568 mmol/g) < nano HAP(0.643 mmol/g); and 30‰ salinity was IOCS(0.002 mmol/g) < MnCS(0.002 mmol/g) < nano HAP(0.254 mmol/g) < PMM(0.319 mmol/g) < fishbone(0.379 mmol/g). The highest Zn sorption capacity at 0 and 30‰ of salinity was found with nano HAP, and the highest Ni sorption capacity at 0‰ salinity was with nano HAP and at 30‰ salinity was with fishbone. The sorption capacity decreased as the salinity of the solution increased and this phenomenon was the result of the salting out effect which hinders sorption. In the competitive sorption of Zn and Ni, the lower sorption capacity of the sorbents were observed for bi-solute sorption compared with single-solute sorption. In the bi-solute competitive sorption, IOCS and fishbone at 30‰ of salinity had lower sorption capacity than the single-solute sorption. On the other hand, the sorption capacity of MnCS, nano HAP, and PMM was higher in bi-solutie competitive sorption than that in single-solute sorption. As concentration of humic acid was increased, sorption capacity of heavy metals decreased both at 0 and 30 ‰ of salinity. Because humic acid reacted with Zn and Ni well and prevent Zn and Ni from sorption to sorbent. Sorption capacity of heavy metals increased with increasing pH, it may caused by precipitation of heavy metals.

Sorption of hydrophobic organic chemicals by Korean andisols from methanol-water system : the effects of functional group and aqueous ionic composition

김주희 Graduate School, Korea University 2010 국내석사

Water miscible organic solvent may increase the mobility of organic contaminants through soil subsurface by increasing the solubility and decreasing the sorption. Sorption of hydrophobic organic compounds (HOCs) by soils in the cosolvent system can be successfully described by log linear cosolvency model. However, the application of similar model to sorption of ionizable hydrophobic organic compounds (HIOCs) by variable charge soils is limited due to further consideration of the additional effect of functional group, ionic speciation of solute, and ionic composition of solution. In this study, sorption of two model solutes (naphthalene (NAP), and 1-naphthoic acid (1-NAPA)) by three Korean Andisols (SD, DH, and EG), kaolinite and humic acid were measured as a function of methanol volume fraction (0 ≤ fc ≤0.5) and ionic composition (CaCl2 and KCl). Solubility of 1-NAPA was also measured from methanol-CaCl2, methanol-KCl and methanol-soil extract solution mixture within the range of fc ≤ 0.5 . From sorption experiments with 3 Korean Andisols, log Km (the linear sorption coefficient) of NAP from both ionic compositions was log linearly decreased with increasing fc with ασ values being 4-11% greater in methanol-CaCl2 mixture relative to methanol-KCl mixture. However, the sorption of 1-NAPA remained relatively constant under same condition (i.e., no apparent correlation between log Km and fc for 1-NAPA). Sorption of 1-NAPA by kaolinite at methanol-CaCl2 mixture of fc = 0.5 was greater than at fc = 0, while for methanol-KCl mixture, sorption of 1-NAPA was low at fc = 0.5. Sorption of 1-NAPA by humic acid was decreased as increasing fc regardless of ionic composition. The solubility profile measured from different ionic composition provide the knowledge of the impact of different ions on the change of aqueous activity of the solutes. From solubility experiments, no significant difference in 1-NAPA solubility between methanol-CaCl2-soil extract mixture and methanol-CaCl2 mixture was found, indicating the presence of soil did not induce the change of aqueous activity of 1-NAPA. However, compared to methanol-KCl mixture, solubility enhancement of 1-NAPA in methanol-CaCl2 mixture was greater than in methanol-KCl mixture (i.e., the slope(σ) of the solubility profile with fc in methanol-CaCl2 mixture was greater than methanol-KCl mixture), showing the impact of cation on the change of aqueous activity of 1-NAPA. In conclusion, the result of the study clearly demonstrates that functional group of 1-NAPA and ionic composition can modify the action of cosolvent moderating the sorption behavior of 1-NAPA toward variable charge soils. However, the exact mechanism is unclear yet. Further works focusing on the alternation of sorption domain in the presence of cosolvent and subsequent impacts on HIOCs sorption by variable charge soils are required. 본 연구는 물-메탄올 시스템에서 유기화합물의 Korean Andisols 흡착에 영향을 미치는 인자들 (유기화합물의 작용기와 용액의 이온조성) 에 대한 고찰을 목적으로 하고 있다. Cosolvent는 용액 중에 존재하는 유기화합물의 활동도와 용해도에 영향을 미치는 동시에 흡착에도 영향을 미치며, 유기화합물의 토양흡착은 cosolvency model에 의해 정량적으로 적용될 수 있다. 지금까지 비극성 유기화합물 (Hydrophobic organic compounds, HOCs) 의 토양흡착에 미치는 cosolvent effects에 대해서 많은 연구가 이루어졌다. 그러나 이온화 유기화합물 (Hydrophobic ionizable organic compounds, HIOCs) 에 대한 cosolvency model의 적용은 1) 유기화합물의 작용기 2) 용액 중의 이온 조성 3) 이온화종 (ionized species)과 중성종 (neutral species) 의 토양에 대한 흡착 등을 동시에 고려해야 하기 때문에 제약을 받게 된다. 두 유기화합물 (naphthalene (NAP), 1-Naphthoic acid (1-NAPA)) 의 Korean Andisols에 대한 흡착을 메탄올 양 (0 ≤ fc ≤0.5) 과 이온조성 (CaCl2 과 KCl) 을 달리하여 관찰하였고, 1-NAPA의 카올리나이트 흡착과 휴믹산 흡착실험이 추가적으로 진행되었다. 또한, 1-NAPA의 용해도 실험을 메탄올-CaCl2, 메탄올-KCl 그리고 methanol-토양추출용액에서 메탄올 양 (fc ≤ 0.5) 을 달리하여 실험하였다. 흡착실험 결과, naphthalene은 메탄올-CaCl2 용액과 메탄올-KCl 용액에서 모두 메탄올 양이 증가할수록 흡착량이 감소되어 cosolvency model에 적용되었으나, 1-Naphthoic acid는 메탄올 양이 증가하여도 흡착량이 거의 감소하지 않고 오히려 증가하는 행동을 보였다. 1-Naphthoic acid의 카올리나이트와 휴믹산 흡착 실험 결과, 휴믹산에서는 메탄올 양에 따라 흡착이 감소되었으나 카올리나이트에서는 메탄올-CaCl2 용액에서 메탄올 양에 따라 흡착이 오히려 증가하는 경향을 보였다. 1-NAPA의 용해도실험 결과 메탄올-CaCl2와 methanol-CaCl2-토양추출용액 간에 뚜렷한 차이가 없었다. 이 결과는 토양이 존재하여도 수용액에서의 1-NAPA의 활동도에는 변화가 없다는 것을 나타낸다. 그러나메탄올-KCl 용액과 비교했을 때, 메탄올-CaCl2 용액에서의 1-NAPA 용해도 증가가 메탄올-KCl 용액에서 보다 더 컸으며, 이는 수용액에 존재하는 양이온이 1-NAPA 활동도에 영향을 미친다는 것을 나타낸다. 본 연구의 결과를 통해서 용액의 이온조성과 유기화합물의 작용기가 cosolvent effect (1-NAPA의 가변전하토양에 대한 흡착에 미치는 기작) 에 중요한 기여를 할 수 있다고 제시되었으나, 그 기작은 아직 명확하지 않다. 따라서 cosolvent의 존재 하에서 실제 가변전하토양의 친수성 영역과 소수성 영역의 두 영역에서 HIOCs가 흡착하는 현상을 전체적으로 묘사할 수 있는 추가적인 실험이 필요하다고 판단된다.

biochar 기반 복합소재를 이용한 오염물질 제거

서용득 울산대학교 일반대학원 2021 국내석사

In this study, We synthesized various types of biochar through pyrolysis and examined their application methods to increase the value of biochar. The feasibility of using biochar as a sorbent to remove nitro explosives and metals from contaminated water was investigated through batch experiments. Biochar, synthesized using biomasses, showed a porous structure and a high surface area and included embedded carbonate minerals. Compared with granular activated carbon (GAC), biochar was competitive as a sorbent for removing Cd, Cu, Pb, and Zn from water according to the maximum sorption capacities of the metals. Some biochars also effectively sorbed nitro explosives from water. Correlation analysis between maximum sorption capacities and properties of biochar showed that the sorption capacity of biochar for cationic toxic metals is related to the cation exchange capacity (CEC) and that the sorption capacity of explosives is proportional to the surface area and carbon content. In addition, results from X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) analyses, and laboratory experiments suggest that surface functional groups may be responsible for the sorption of cationic metals to the biochar surface. In contrast, carbon contents may account for the sorption of explosives, possibly through π–π electron donor-acceptor interactions. The feasibility of using biochar as a sorbent to remove nine halogenated phenols (2,4-dichlorophenol, 2,4-dibromophenol, 2,4-difluorophenol, 2-chlorophenol, 4-chlorophenol, 2-bromophenol, 4-bromophenol, 2-fluorophenol, and 4-fluorophenol) and two pharmaceuticals (triclosan and ibuprofen) from the water was examined through a series of batch experiments. Biochar was synthesized using various biomasses, including fallen leaves, rice straw, corn stalks, spent coffee grounds, and biosolid. Compared to GAC, most biochar samples did not effectively remove halogenated phenols or pharmaceuticals from water. The increase in pH and deprotonation of phenols in biochar systems may be responsible for its inefficiencies at this task. However, when pH is maintained at 4 or 7, the sorption capacity of biochar is markedly increased. Considering the maximum sorption capacity and properties of sorbents and sorbates, the sorption capacity of biochar for halogenated phenols is related to the surface area and carbon content of biochar and hydrophobicity of contaminants. In the cases of triclosan and ibuprofen, the sorptive capacities of GAC, graphite, and biochars were also significantly affected by pH, according to the point of zero charge (PZC) of sorbents and deprotonation of the pharmaceuticals. Pyrolysis temperature did not affect the sorption capacity of halogenated phenols or pharmaceuticals. The synthesis of zero-valent iron [Fe(0)]-included biochar (Fe(0)-biochar] was applied to remove nitro explosives (2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)) and halogenated-phenols (DBP and DFP) from contaminated waters. Due to the presence of biochar on the outside, the removal of nitro explosives and halogenated phenols was significantly enhanced via sorption. The sorbed contaminants were further transformed into reducing agents, indicating that the inner Fe(0) played the role of a reductant in the Fe(0)-biochar. Compared to direct reduction with Fe(0), the reductive transformation with Fe(0)-biochar was markedly enhanced, suggesting that the biochar in Fe(0)-biochar may act as an electron transfer mediator. Further experiments showed that the surface functional groups of biochar were involved in the catalytic enhancement of electron transfer. Co-pyrolysis of polymer and biomass wastes was investigated as a novel method for waste treatment and synthesis of enhanced biochar. Co-pyrolysis of RS with polypropylene (PP), polyethylene (PE), or polystyrene (PS) increased the carbon content, CEC, BET surface area, and pH of the biochar. As a result, the sorption of 2,4-dinitrotoluene (DNT) and Pb to polymer/RS-derived biochar was markedly enhanced. The increased aromaticity and hydrophobicity contents may enhance the DNT sorption to the polymer/RS-derived biochar. In contrast, increasing CEC, higher pH, and the newly developed surface area may account for the enhancement in Pb sorption. The addition of polymer to RS did not significantly change the catalytic role of biochar during DNT reduction by dithiothreitol. Biochar was synthesized using wood chips (WC), BS, and biomass obtained in large quantities in Korea, and its adsorption capacity was analyzed through a batch experiment. We evaluated the carbon sequestration capacity using biochar–mortar composites according to characteristics for construction and environmental applications. Characterization of biochar–mortar composites showed that 3-5 vt% biochar inclusion did not significantly change the composites' engineering properties, including flowability, compressive strength, and thermal conductivity. Furthermore, as the biochar content increased in the biochar–mortar, the benzene and toluene concentrations in the air were accordingly reduced, suggesting that biochar inclusion may be favorable to remove volatile toxic contaminants. The toxicity characteristics leaching procedure (TCLP) and Micotox®bioassay tests showed that biochar–mortar composites were not toxic. These results confirmed that biochar and biochar-based composite materials are competitive can be effectively used as sorbents, catalysts, or reducing agents for contaminants. The improving value of biochar suggests that biochar production via pyrolysis may be a promising option for carbon sequestration to release CO2 mitigation.

Hydrothermal synthesis of K2CO3-promoted hydrotalcite based on hydroxide-form precursors for high temperature CO2 sorbent

장희진 Graduate School, Korea University 2014 국내석사

In many materials for CO2 sorption, hydrotalcite is attracting substantial attention as high temperature (200-500 °C) CO2 sorbent due to its fast sorption/ desorption kinetics and easy regenerability. However, the CO2 sorption capacity of conventional hydrotalcite is relatively low for large-scale commercial use. To enhance the CO2 sorption capacity, hydrotalcite is impregnated with K2CO3 and/or Na2CO3. Although K2CO3/Na2CO3 promoted hydrotalcite has high CO2 sorption capacity, the synthesis method takes long time and is inconvenient because hydrotalcite synthesis step and alkali metal impregnation step are separated. Conventionally, hydrotalcite is synthesized from water soluble nitrate form precursors by a co-precipitation method. Although hydrotalcite structure is easily developed by a co-precipitation method, product crystallinity is low. Moreover, product should be repeatedly washed because large amount of basic solution such as NaOH or KOH are added during the synthesis step to control the pH of solution. In this study, K2CO3-promoted hydrotalcite was newly synthesized by a simple and eco-friendly method without a solvent-consuming washing step. Analysis based on X-ray diffraction indicated that all samples had structures of well-defined hydrotalcite crystalline and un-reacted Mg(OH)2 precursor. Moreover, K2CO3 was successfully co-precipitated in sample during the synthesis step. Morphology of hydrotalcite was confirmed by the scanning electron microscopy and showed the hexagonal plate-like structure. The analysis based on N2 adsorption data showed the decrease in surface area with increase in the amount of co-precipitated K2CO3. Thermogravimetric analysis was used to measure CO2 sorption capacity and the results revealed that CO2 sorption capacity increased by co-precipitation of K2CO3 and K2CO3 co-precipitated amount had an optimum value. The CO2 sorption isotherm was measured at 240 °C temperature and 0.05-10 bar pressure range and fitted to Langmuir isotherm model. Moreover, the regeneration ability of sorbents was assessed by sorption/desorption cycles.

Double salt-based sorbents for carbon dioxide capture and its application to sorption-enhanced reaction processes for high-purity hydrogen production

이찬현 Graduate School, Korea University 2017 국내박사

High-temperature CO2 sorption has been investigated as a new CO2 capture technology, and the development of high-temperature CO2 sorbents is critically important for the realization of this technology. One of candidate solid materials, metal oxides have been highlighted due to their outstanding theoretical sorption capacities. However, sorbents based on metal oxides need harsh conditions for regeneration and the sorption uptakes are significantly decreased during cyclic sorption/desorption procedure. To solve these problems, salt-promoting has been suggested as a prominent solution. In this thesis, double salt-based sorbents containing metal oxide and alkali metal carbonate and/or alkali metal nitrate were prepared and tested for high-temperature CO2 sorption. The prepared sorbents showed unique CO2 sorption characteristics in the temperature of 300-500 °C for Na-Mg and K-Mg double salt-based sorbents and 600-800 °C for Na-Ca double salt-based sorbent, respectively. A remarkably high CO2 sorption uptakes were measured using TGA and it maintained during repeated sorption/desorption cycles. In addition to the high CO2 sorption uptake and good cyclic stability, the double salt-based sorbents show exceptionally fast sorption/desorption kinetics. In-situ X-ray diffraction analysis revealed that the CO2 sorption mechanism is based on the reaction of CO2 with metal oxide and alkali metal carbonate in the double salt-based sorbent to form double salt of carbonates. The sorption behavior of double salt-based sorbent was also analyzed with theoretical models, and the results advanced the understanding of the effect of alkali metal carbonate on double salt-based sorbents. The sorption properties of double salt-based sorbents were further improved by manipulation of synthetic methods. Double salt-based sorbents were newly synthesized using a pH-controlled precipitation method and the prepared sorbents were investigated for high-temperature CO2 sorption. In the new method for the synthesis of double salt-based sorbents, the pH of the reagent solution was controlled by adding different reagent solutions, resulting in various component ratios in the sorbent. The CO2 sorption ability was enhanced in the sorbents synthesized using the new pH-controlled method, compared to the samples synthesized by the conventional precipitation method. The prepared double salt-based sorbents were also applied for the CO2 sorbent in the sorption-enhanced water gas shift (SE-WGS) reaction where WGS reaction and CO2 sorption are carried out simultaneously for the production of high-purity hydrogen. Since the performance of SE-WGS is dependent on the degree of homogeneity of catalyst and sorbent, one-body hybrid solid, a physical admixture of catalyst and sorbent, was prepared by ball-milling. However, the SE-WGS reaction with double salt-based sorbents showed poor reactivity and reduced CO2 sorption capacity. To solve these problems, a divided section packing concept was applied. In the divided section packing method, the degree of homogeneity for catalyst and sorbent in the column could be controlled by number of sections. Finally, high-purity hydrogen could be produced from the SE-WGS reaction with divided section packing, and the productivity was increased when the reaction zone was divided into more sections and packed more sorbent. The experimental results showed that the double salt-based sorbent can be applied to SE-WGS reaction and the productivity of hydrogen is improved by removal of byproduct CO2.