Yong-Yoon Ahn

Euntae Yun

Yong-Uk Shin

Jaesung Kim

Bowen Yang

Yudong Xue

Hongshin Lee

Jihyun Choi

Hayoung Yoo

Moongyu Kim

Yelim Kim

Geondu Gim

Saein Suh

Yaeeun Kim

Wooseok Choi

Soyeon Song

Dahye Min

Nayeon Ko

The ROCATES Lab concentrates its research efforts to explore diverse approaches for oxidation-based water remediation, develop advanced materials and systems for markedly improving water treatment efficiency, and investigate redox chemistry that is fundamental to degradative reaction pathways.

Formation and Decay of Aqueous Fe(IV) during Fe(II) Ozonation under Acidic Conditions: Kinetics and Mechanistic Insights into pH-Dependent Behavior

Identifying a catalytic center in metal-carbon composites for O3 and persulfate activation: Active site switching between carbon and metal phases

Revisiting current efficiency for electrochemical reactive chlorine generation and mediated wastewater treatment

Hydraulic conductivity reduction during the recharge of the discharged groundwater: Clogging pattern variation according to turbidity fluxes

Conversion of ozone into hydroxyl radical by granular activated carbon with and without biofilms: Implications for micropollutant abatement

Bromide oxidation by bromate in a frozen solution and reactive bromine species production

Unveiling the unforeseen role of manganese constituent in creating a carbon-based composite as a high-efficiency persulfate activator: Catalyzing carbon phase graphitization and promoting persulfate binding affinity

Paired photoelectrochemical system for total nitrogen removal via engineered active sites in spaced TiO2 nanotube platform

Encapsulating Co and Pd nanoparticles as spatially separated dual active sites for heterogeneous persulfate activation: Synergistic catalysis and switching of the primary reaction pathway

Potential of homogeneous persulfate activation as a strategy for the oxidative treatment of tetramethylammonium hydroxide: Superiority of sulfate radical over hydroxyl radical in the oxidation of methylammoniums

Oxyanion-sensitive catalytic activity of Ni(II)/oxyanion systems for heterogeneous organic degradation: Differential oxidizing capacity of Ni(III) and Ni(IV) as high-valent intermediates

Prediction of hydroxyl radical exposure during ozonation using different machine learning methods with ozone decay kinetic parameters

Ferrate (VI) activation with nanoconfined Cu–Mg sites for water treatment: Selective Cu (III) production via support-dependent redox catalysis

Unveiling the oxidation mechanism of persistent organic contaminants via visible light-induced dye-sensitized reaction by red mud suspension with peroxymonosulfate

Role of inorganic anions in improving the oxidizing capacity of heat-activated peroxymonosulfate: Identification of primary degradative pathways

Persulfate-based advanced oxidation: critical assessment of opportunities and roadblocks

Identifying the nonradical mechanism in the peroxymonosulfate activation process: singlet oxygenation versus mediated electron transfer

Nanomaterials in the construction industry: a review of their applications and environmental health and safety considerations

Activation of persulfates by carbon nanotubes: oxidation of organic compounds by nonradical mechanism

Surface-loaded metal nanoparticles for peroxymonosulfate activation: Efficiency and mechanism reconnaissance

Simultaneous and Synergistic Conversion of Dyes and Heavy Metal Ions in Aqueous TiO 2 Suspensions under Visible-Light Illumination

Exploring the role of persulfate in the activation process: radical precursor versus electron acceptor

Activation of peroxymonosulfate by surface-loaded noble metal nanoparticles for oxidative degradation of organic compounds

Photocatalytic reactivity of surface platinized TiO2: substrate specificity and the effect of Pt oxidation state

Selective Photocatalytic Oxidation of NH 3 to N 2 on Platinized TiO 2 in Water

Selective Oxidative Degradation of Organic Pollutants by Singlet Oxygen-Mediated Photosensitization: Tin Porphyrin versus C 60 Aminofullerene Systems

Oxidizing capacity of periodate activated with iron-based bimetallic nanoparticles

Oxidation of organic pollutants by peroxymonosulfate activated with low-temperature-modified nanodiamonds: Understanding the reaction kinetics and mechanism

Photochemical production of reactive oxygen species by C60 in the aqueous phase during UV irradiation

Heterogeneous photocatalytic treatment of pharmaceutical micropollutants: Effects of wastewater effluent matrix and catalyst modifications

Photochemical and Antimicrobial Properties of Novel C 60 Derivatives in Aqueous Systems

Chloride-mediated enhancement in heat-induced activation of peroxymonosulfate: New reaction pathways for oxidizing radical production

Boosting the electrocatalytic activities of SnO2 electrodes for remediation of aqueous pollutants by doping with various metals

Photocatalytic degradation of N-nitrosodimethylamine: mechanism, product distribution, and TiO2 surface modification

Visible-light-induced activation of periodate that mimics dye-sensitization of TiO2: simultaneous decolorization of dyes and production of oxidizing radicals

Jaesang Lee

Reports that promote persulfate-based advanced oxidation process (AOP) as a viable alternative to hydrogen peroxide-based processes have been rapidly accumulating in recent water treatment literature. Various strategies to activate peroxide bonds in persulfate precursors have been proposed and the capacity to degrade a wide range of organic pollutants has been demonstrated. Compared to traditional AOPs in which hydroxyl radical serves as the main oxidant, persulfate-based AOPs have been claimed to involve different in situ generated oxidants such as sulfate radical and singlet oxygen as well as nonradical oxidation pathways. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and …

Select persulfate activation processes were demonstrated to initiate oxidation not reliant on sulfate radicals, although the underlying mechanism has yet to be identified. This study explored singlet oxygenation and mediated electron transfer as plausible nonradical mechanisms for organic degradation by carbon nanotube (CNT)-activated peroxymonosulfate (PMS). The degradation of furfuryl alcohol (FFA) as a singlet oxygen ( 1 O 2 ) indicator and the kinetic retardation of FFA oxidation in the presence of l -histidine and azide as 1 O 2 quenchers apparently supported a role of 1 O 2 in the CNT/PMS system. However, the 1 O 2 scavenging effect was ascribed to a rapid PMS depletion by l -histidine and azide. A comparison of CNT/PMS and photoexcited Rose Bengal (RB) excluded the possibility of singlet oxygenation during heterogeneous persulfate activation. In contrast to the case of excited RB, solvent exchange (H 2 O …

The extraordinary chemical and physical properties of materials at the nanometer scale enable novel applications ranging from structural strength enhancement and energy conservation to antimicrobial properties and self-cleaning surfaces. Consequently, manufactured nanomaterials (MNMs) and nanocomposites are being considered for various uses in the construction and related infrastructure industries. To achieve environmentally responsible nanotechnology in construction, it is important to consider the lifecycle impacts of MNMs on the health of construction workers and dwellers, as well as unintended environmental effects at all stages of manufacturing, construction, use, demolition, and disposal. Here, we review state-of-the-art applications of MNMs that improve conventional construction materials, suggest likely environmental release scenarios, and summarize potential adverse biological and toxicological …

Carbon nanotubes (CNTs) have been found to activate persulfates (i.e., peroxymonosulfate and peroxydisulfate) into reactive species that are capable of oxidizing organic compounds in water. In the presence of single- or multi-walled CNTs, persulfates effectively degraded phenolic compounds and certain pharmaceuticals. Phenyl derivatives substituted with electron-withdrawing groups, such as benzoic acid and nitrobenzene, were resistant to degradation by the CNT/persulfate system. Based on observations regarding persulfate decomposition and linear sweep voltammetry using a CNT electrode, it has been suggested that persulfates bind onto the surface of CNTs, forming reactive complexes that are immediately decomposed upon reaction with organic compounds. Electron paramagnetic resonance spectroscopy with spin-trapping indicates that these reactive species are distinct from sulfate radical anions or …

This study comparatively examines the efficiency and mechanism of peroxymonosulfate (PMS) activation by twenty metal and metalloid nanoparticles loaded on alumina. Among the tested metals, Co exhibited the highest capacity for PMS activation and accompanying oxidative degradation of trichlorophenol (TCP), a representative organic pollutant in water. Other transition metals such as Mn, Cu, Mo, Ni, and W exhibited moderate activity, while Ti, Zn, Fe, V, Cr, Al, and Si were mostly ineffective. In contrast, all of the tested noble metals (Ru, Rh, Pd, Ir, Pt, and Au) except Ag enabled rapid PMS activation and TCP degradation, outperforming Co at acidic pH. Transition metals with noticeable PMS activation capacity differed from noble metals in several aspects, such as the effect of radical quenching on 4-chlorophenol (4-CP) degradation, electron paramagnetic resonance spectral features, oxidative conversion of …

This study reports synergistic effects in the simultaneous conversion of dyes and heavy metal ions in aqueous TiO 2 /dye/metal ion systems (ternary components) under visible light (λ > 420 nm). TiO 2 /Cr(VI)/Acid Orange 7 (AO7), TiO 2 /Cr(VI)/Rhodamine B (RhB), TiO 2 /Ag + /AO7, and TiO 2 /Ag + /RhB were chosen as test systems. Although dyes can be degraded in TiO 2 suspensions under visible light, their removal rates were markedly enhanced in the presence of metal ions. Similarly, the reduction rates of metal ions in visible-light-illuminated TiO 2 suspensions were negligible, but they were highly accelerated with dyes present. In particular, the synergistic effect in the ternary system of TiO 2 /Cr(VI)/AO7 was outstanding. The presence of dissolved oxygen increased the photoreduction rate of Cr(VI) despite the fact that Cr(VI) and O 2 are competing electron acceptors. This is ascribed to in-situ photogenerated H 2 O 2 from O …

This study elucidates the mechanism behind persulfate activation by exploring the role of various oxyanions (e.g., peroxymonosulfate, periodate, and peracetate) in two activation systems utilizing iron nanoparticle (nFe 0 ) as the reducing agent and single-wall carbon nanotubes (CNTs) as electron transfer mediators. Since the tested oxyanions serve as both electron acceptors and radical precursors in most cases, oxidative degradation of organics was achievable through one-electron reduction of oxyanions on nFe 0 (leading to radical-induced oxidation) and electron transfer mediation from organics to oxyanions on CNTs (leading to oxidative decomposition involving no radical formation). A distinction between degradative reaction mechanisms of the nFe 0 /oxyanion and CNT/oxyanion systems was made in terms of the oxyanion consumption efficacy, radical scavenging effect, and EPR spectral analysis. Statistical …

This study demonstrates the capability of noble metal nanoparticles immobilized on Al 2 O 3 or TiO 2 support to effectively activate peroxymonosulfate (PMS) and degrade select organic compounds in water. The noble metals outperformed a benchmark PMS activator such as Co 2+ (water-soluble) for PMS activation and organic compound degradation at acidic pH and showed the comparable activation capacity at neutral pH. The efficiency was found to depend on the type of noble metal (following the order of Pd > Pt ≈ Au ≫ Ag), the amount of noble metal deposited onto the support, solution pH, and the type of target organic substrate. In contrast to common PMS-activated oxidation processes that involve sulfate radical as a main oxidant, the organic compound degradation kinetics were not affected by sulfate radical scavengers and exhibited substrate dependency that resembled the PMS activated by carbon …

Surface platinized TiO 2 (Pt/TiO 2 ) has been frequently studied, but its photocatalytic reactivities reported in the literature are not consistent in some cases. To understand the discrepancies, the effects of Pt speciation on TiO 2 on the photocatalytic degradation (PCD) of a few chlorinated organic compounds (trichloroethylene (TCE), perchloroethylene (PCE), dichloroacetate, etc.) were investigated with several Pt/TiO 2 samples that were prepared differently. The oxidation state of Pt deposits was analyzed by X-ray photoelectron spectroscopy and was found to be the most important factor in determining the initial PCD rates of chlorinated organic compounds. TiO 2 with oxidized Pt species (Pt ox /TiO 2 ) was less reactive than TiO 2 with metallic Pt (Pt 0 /TiO 2 ) for all substrates tested. In particular, Pt ox /TiO 2 strongly inhibited the PCD of TCE and PCE whereas it was more reactive than pure TiO 2 for the PCD of other …

Selective photocatalytic oxidation of NH 3 to N 2 is proposed as a new treatment method for controlling the levels of ammonia in water. The photocatalytic oxidation of ammonia on naked and metallized TiO 2 in water saturated with air, nitrogen, or N 2 O gas was investigated. While the slow photocatalytic oxidation of NH 3 to NO 2 - /NO 3 - is the only pathway for decomposition of NH 3 on naked TiO 2 and Au/TiO 2 , a new pathway, that of selective oxidation of ammonia to dinitrogen, opens up on Pt/TiO 2 . The formation of dinitrogen from the oxidation of 15 NH 3 was confirmed by mass spectrometric detection of 15 N 2 . The photocatalytic conversion of NH 3 to N 2 greatly increases when the Pt/TiO 2 suspension is saturated with N 2 O gas, whereas N 2 O itself shows little reactivity with naked TiO 2 and Au/TiO 2 . Over 80% of the total nitrogen available in ammonia (0.1 mM) is converted into N 2 within 40 min illumination of the N 2 O …

This study evaluates the potential application of tin porphyrin- and C 60 aminofullerene-derivatized silica (SnP/silica and aminoC 60 /silica) as 1 O 2 generating systems for photochemical degradation of organic pollutants. Photosensitized 1 O 2 production with SnP/silica, which was faster than with aminoC 60 /silica, effectively oxidized a variety of pharmaceuticals. Significant degradation of pharmaceuticals in the presence of the 400-nm UV cutoff filter corroborated visible light activation of both photosensitizers. Whereas the efficacy of aminoC 60 /silica for 1 O 2 production drastically decreased under irradiation with λ > 550 nm, Q-band absorption caused negligible loss of the photosensitizing activity of SnP/silica in the long wavelength region. Faster destruction of phenolates by SnP/silica and aminoC 60 /silica under alkaline pH conditions further implicated 1 O 2 involvement in the oxidative degradation. Direct charge …

Nanosized zerovalent iron (nFe 0 ) loaded with a secondary metal such as Ni or Cu on its surface was demonstrated to effectively activate periodate (IO 4 – ) and degrade selected organic compounds at neutral pH. The degradation was accompanied by a stoichiometric conversion of IO 4 – to iodate (IO 3 – ). nFe 0 without bimetallic loading led to similar IO 4 – reduction but no organic degradation, suggesting the production of reactive iodine intermediate only when IO 4 – is activated by bimetallic nFe 0 (e.g., nFe 0 –Ni and nFe 0 –Cu). The organic degradation kinetics in the nFe 0 –Ni(or Cu)/IO 4 – system was substrate dependent: 4-chlorophenol, phenol, and bisphenol A were effectively degraded, whereas little or no degradation was observed with benzoic acid, carbamazepine, and 2,4,6-trichlorophenol. The substrate specificity, further confirmed by little kinetic inhibition with background organic matter, implies the selective …

Changes in surface carbon hybridization through high-temperature annealing (>1000 °C) of nanodiamond (ND), i.e., surface graphitization, enable peroxymonosulfate (PMS) activation by ND. Alternatively, this study suggests low-temperature surface modification (500 °C) of ND as an effective strategy for allowing ND to activate PMS. ND calcination in the presence of poly(diallydimethylammonium chloride) (PDDA) and graphene oxide (GO) in an NH 3 atmosphere produced binary and ternary nitrogen-doped ND composites (i.e., N-ND/PDDA and N-ND/PDDA/GO). Compared with bare ND, theses surface-modified NDs markedly enhanced organic oxidation associated with PMS activation. In particular, N-ND/PDDA/GO outperformed graphitized ND in terms of PMS activation capacity. Spectroscopic characterization implied that the content of pyridinic N and the N doping level increased with further modification of …

The objective of this study was to investigate photochemical production of singlet oxygen ( 1 O 2 ) and superoxide radical anion (O 2 • - ) by C 60 in water. It was demonstrated that photoexcited C 60 in the aqueous phase efficiently mediated transfer of absorbed energy to oxygen and produced singlet oxygen when associated with surfactant (Triton X100 and Brij 78) or polymer (polyvinylpyrrolidone), which is consistent with previously observed behavior in organic solvents. However, when C 60 was present as colloidal aggregate suspension, prepared through solvent exchange or sonication, this intrinsic character was lost. Similarly, C 60 associated with surfactant mediated electron transfer from electron donor (triethylamine) to oxygen producing superoxide radical, while C 60 aggregates and C 60 associated with polymer did not. These results suggest that the ability of C 60 to mediate energy and electron transfer may be …

This study evaluates the applicability of TiO 2 -based photocatalysts for the treatment of pharmaceutical micropollutants in secondary wastewater effluent (SWE). Photolytic experiments using SWEs with different compositions demonstrated that the rates of photocatalytic degradation of acetaminophen and carbamazepine inversely correlated with the concentration of dissolved organic carbon (DOC), regardless of the type of applied light source and initial pharmaceutical concentration. The critical relevance of organic matter to the scavenging behavior of SWE was further verified by assessing the photocatalytic performance as a function of the concentrations of potential effluent-derived quenchers (i.e., NO 3 − , Cl − , alkalinity, and humic acid). Kinetic comparison of the degradation of trace levels of pharmaceuticals (i.e., caffeine, cimetidine, propranolol, and sulfamethoxazole) using TiO 2 /UV-A, TiO 2 /UV-C, and H 2 O 2 /UV …

Four novel hexakis C 60 derivatives with varying functionalities were synthesized, and their photochemical properties and photodynamic disinfection efficiencies were quantitatively evaluated. All these C 60 derivatives generated 1 O 2 more efficiently than commercial multihydroxylated C 60 (fullerol), as assessed by furfuryl alcohol consumption and electron paramagnetic resonance analysis. Despite significant agglomeration/aggregation in the aqueous phase to micrometer-sized particles, nanosecond laser flash photolysis showed that the lifetime of triplet state (a key intermediate for energy transfer responsible for 1 O 2 production) was comparable to reported values for pristine C 60 in organic phase. As a result of facile 1 O 2 production, the C 60 derivatives efficiently inactivated Escherichia coli and MS-2 bacteriophage. Cationic aminofullerene hexakis, which likely exerted electrostatic attraction, exhibited …

This study is the first to demonstrate the capability of Cl – to markedly accelerate organic oxidation using thermally activated peroxymonosulfate (PMS) under acidic conditions. The treatment efficiency gain allowed heat-activated PMS to surpass heat-activated peroxydisulfate (PDS). During thermal PMS activation at excess Cl – , accelerated oxidation of 4-chlorophenol (susceptible to oxidation by hypochlorous acid (HOCl)) was observed along with significant degradation of benzoic acid and ClO 3 – occurrence, which involved oxidants with low substrate specificity. This indicated that heat facilitated HOCl formation via nucleophilic Cl – addition to PMS and enabled free chlorine conversion into less selective oxidizing radicals. HOCl acted as a key intermediate in the major oxidant transition based on temperature-dependent variation in HOCl concentration profiles, kinetically retarded organic oxidation upon NH 4 …

The purpose of this study is to search for effective dopants and their optimal combinations to improve the electrocatalytic activity of the SnO 2 electrode for the remediation of aqueous pollutants. For this purpose, Sb was selected as the primary dopant for SnO 2 and six elements (Fe(III), Ni(II), Co(II), Ru(III), Ce(III), and Pd(II)) were also introduced into the optimized Sb–SnO 2 electrodes. The electrodes were checked for their electrochemical properties at different doping levels and tested for their electrocatalytic activities for the degradation of phenol and Eosin Y. In addition, RNO (N,N-dimethyl-p-nitrosoaniline) was used as a probe molecule for OH radicals to examine the reaction mechanism occurring at the electrodes. Sb with a 5–10at.% was most effective in making SnO 2 an electrocatalyst and Ni (∼1%) enhanced the degradation rate and TOC removal rate of phenol at the Sb–SnO 2 anode by a factor of 14 and 8 …

The photocatalytic degradation (PCD) reaction of N- nitrosodimethylamine (NDMA) in water was investigated using pure and surface-modified TiO 2 . The PCD products of NDMA were methylamine (MA), dimethylamine (DMA), nitrite, nitrate, and ammonium, and their distribution could be changed by modifying the surface of TiO 2 . The PCD reaction of NDMA seems to be initiated mostly by OH radicals, not valence band holes, because the addition of excess oxalates (hole scavengers) only moderately retarded the PCD rate. The presence of oxalate, however, enabled a new reductive transformation path in which the CO 2 - • radicals generated from the oxalate converted NDMA into DMA. In acidic suspensions of pure TiO 2 , the formation of MA was highly favored over DMA and NH 3 , whereas all degradation products (MA, DMA, and NH 3 ) were generated at comparable concentrations at basic pH. It is suggested that …

Inspired by the mechanism behind self-sensitized destruction of dyes on semiconductor photocatalysts, we herein present the first instance of visible-light-induced activation of periodate (IO 4 − ) into reactive iodine radicals via sensitized electron transfer from an organic dye, Rhodamine B (RhB). The IO 4 − reduction not only leads to oxidative decolorization of RhB but also formation of reactive intermediates that degrade organic compounds. Electron transfer from the excited dye to IO 4 − was confirmed by detecting RhB radical cation (RhBradical dot + ) and measuring its lifetime. The efficiency of organic compound degradation was found to significantly vary depending on the target substrate, i.e., phenol, bisphenol A, and 4-chlorophenol were rapidly decomposed, whereas benzoic acid, carbamazepine, 4-nitrophenol, and sulfamethoxazole exhibited moderate decomposition rate. Lines of evidence in addition to the …

고려대학교 산화환원촉매 연구실

교수님 소개

이재상

연구실 소개

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

Identifying a catalytic center in metal-carbon composites for O3 and persulfate activation: Active site switching between carbon and metal phases

Identifying a catalytic center in metal-carbon composites for O3 and persulfate activation: Active site switching between carbon and metal phases

Formation and Decay of Aqueous Fe(IV) during Fe(II) Ozonation under Acidic Conditions: Kinetics and Mechanistic Insights into pH-Dependent Behavior

연구실 보유 특허

대학별 입시끈

우리 연구실 모집

교수님 소개

이재상

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

Identifying a catalytic center in metal-carbon composites for O3 and persulfate activation: Active site switching between carbon and metal phases

Identifying a catalytic center in metal-carbon composites for O3 and persulfate activation: Active site switching between carbon and metal phases

Formation and Decay of Aqueous Fe(IV) during Fe(II) Ozonation under Acidic Conditions: Kinetics and Mechanistic Insights into pH-Dependent Behavior

연구실 보유 특허

최근 3년간 연구실적 높은 연구실

대학별 입시끈

우리 연구실 모집