Air ionization as a control technology for off-gas emissions of volatile organic compounds

Kim, Ki-Hyun,Szulejko, Jan E.,Kumar, Pawan,Kwon, Eilhann E.,Adelodun, Adedeji A.,Reddy, Police Anil Kumar Elsevier Applied Science Publishers 2017 Environmental pollution Vol.225 No.-

<P><B>Abstract</B></P> <P>High energy electron-impact ionizers have found applications mainly in industry to reduce off-gas emissions from waste gas streams at low cost and high efficiency because of their ability to oxidize many airborne organic pollutants (<I>e.g</I>., volatile organic compounds (VOCs)) to CO<SUB>2</SUB> and H<SUB>2</SUB>O. Applications of air ionizers in indoor air quality management are limited due to poor removal efficiency and production of noxious side products, e.g., ozone (O<SUB>3</SUB>). In this paper, we provide a critical evaluation of the pollutant removal performance of air ionizing system through comprehensive review of the literature. In particular, we focus on removal of VOCs and odorants. We also discuss the generation of unwanted air ionization byproducts such as O<SUB>3</SUB>, NOx, and VOC oxidation intermediates that limit the use of air-ionizers in indoor air quality management.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Much research effort has been put to eliminate or reduce airborne pollutants. </LI> <LI> Destructive methods of VOCs commonly involve thermal oxidation with or without a catalyst. </LI> <LI> In this review, we provide insights into effective strategy for air quality remediation. </LI> <LI> To this end, we assessed the role of air ionization methods for the control of IAQ. </LI> <LI> We discuss future opportunities for air ionization techniques as reliable tools for controlling VOCs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Production of bioplastic through food waste valorization

Tsang, Yiu Fai,Kumar, Vanish,Samadar, Pallabi,Yang, Yi,Lee, Jechan,Ok, Yong Sik,Song, Hocheol,Kim, Ki-Hyun,Kwon, Eilhann E.,Jeon, Young Jae Elsevier 2019 Environment international Vol.127 No.-

<P><B>Abstract</B></P> <P>The tremendous amount of food waste from diverse sources is an environmental burden if disposed of inappropriately. Thus, implementation of a biorefinery platform for food waste is an ideal option to pursue (e.g., production of value-added products while reducing the volume of waste). The adoption of such a process is expected to reduce the production cost of biodegradable plastics (e.g., compared to conventional routes of production using overpriced pure substrates (e.g., glucose)). This review focuses on current technologies for the production of polyhydroxyalkanoates (PHA) from food waste. Technical details were also described to offer clear insights into diverse pretreatments for preparation of raw materials for the actual production of bioplastic (from food wastes). In this respect, particular attention was paid to fermentation technologies based on pure and mixed cultures. A clear description on the chemical modification of starch, cellulose, chitin, and caprolactone is also provided with a number of case studies (covering PHA-based products) along with a discussion on the prospects of food waste valorization approaches and their economic/technical viability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The tremendous amount of food waste (FW) is produced from diverse sources. </LI> <LI> To resolve FW problems, implementation of a biorefinery platform for FW is essential. </LI> <LI> The adoption of such a process can produce value-added products while reducing the waste. </LI> <LI> This review focuses on current technologies for the production of polyhydroxyalkanoates (PHA). </LI> <LI> Prospects of FW valorization are discussed along with their economic/technical viability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Recent advancements in supercapacitor technology

Raza, Waseem,Ali, Faizan,Raza, Nadeem,Luo, Yiwei,Kim, Ki-Hyun,Yang, Jianhua,Kumar, Sandeep,Mehmood, Andleeb,Kwon, Eilhann E. Elsevier 2018 Nano energy Vol.52 No.-

<P><B>Abstract</B></P> <P>Supercapacitors (SCs) are attracting considerable research interest as high-performance energy storage devices that can contribute to the rapid growth of low-power electronics (e.g., wearable, portable electronic devices) and high-power military applications (e.g., guided missile techniques and highly sensitive naval warheads). The performance of SCs can be assessed in terms of the electrochemical properties determined through a combination between the electrode and the electrolyte materials. Likewise, the charge storage capacities of SCs can be affected significantly by selection of such materials (e.g., via surface redox mechanisms). Enormous efforts have thus been put to make them more competitive with existing options for energy storage such as rechargeable batteries. This article reviews recent advances in SC technology with respect to charge storage mechanisms, electrode materials, electrolytes (e.g., particularly paper/fiber-like 3D porous structures), and their practical applications. The challenges and opportunities associated with the commercialization of SCs are also discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> There has been great demand for a reliable technical platform for electrochemical storage. </LI> <LI> SCs are highly attractive option due to their fast storage capability and enhanced cyclic stability. </LI> <LI> This review covers the charge storage mechanisms of SCs along with comparison of selected SCs. </LI> <LI> We also discuss the technical challenges for developing SCs with high enough energy density. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Recently developed methods to enhance stability of heterogeneous catalysts for conversion of biomass-derived feedstocks

김수산,Yiu Fai Tsang,Eilhann E.Kwon,Kun-Yi Andrew Lin,이제찬 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.1

Many processes for the conversion of biomass and its derivatives into value-added products (e.g., fuels and chemicals) use heterogeneous catalysts. However, the catalysts often suffer from deactivation under harsh reaction conditions, such as liquid phase at high temperatures and pressures. The catalyst deactivation is a big obstacle to developing industrially relevant biomass conversion processes, including leaching, sintering, and poisoning of metals and collapse of catalyst support. Different approaches have been applied to limit the reversible and irreversible deactivation, highly associated with the kind of catalyst, reactants, reaction conditions, etc. This review presents recent advances in strategies to stabilize heterogeneous catalysts against deactivation for biomass conversion reactions.

Antiseptic chlorhexidine in activated sludge: Biosorption, antimicrobial susceptibility, and alteration of community structure

Keerthisinghe, Tharushi P.,Nguyen, Luong N.,Kwon, Eilhann E.,Oh, Seungdae Elsevier 2019 Journal of environmental management Vol.237 No.-

<P><B>Abstract</B></P> <P>Chlorhexidine (CHX) is a broad-spectrum antimicrobial, which may pose environmental health risks. This study examined the removal potential and the mechanisms regulating the fate of CHX in activated sludge (AS). Bioreactors inoculated with AS removed 74 ± 8% and 81 ± 6% of CHX at steady state while receiving 0.5 and 1 mg/L CHX, respectively. Analysis of the removal pathways showed that biosorption, rather than biological breakdown or other abiotic losses, largely (>70%) regulated the removal of CHX. 16S rRNA gene-based analysis revealed that CHX selected for <I>Luteolibacter</I> (4.3–10.1-fold change) and <I>Runella</I> (6.2–14.1-fold change) with potential multi-drug resistance mechanisms (e.g., efflux pumps). In contrast, it significantly reduced core members (<I>Comamonadaceae</I> and <I>Flavobacteriaceae</I>) of AS, playing a key role in contaminant removal and floc formation directly associated with the performance of WWTPs (e.g., wastewater effluent quality). Antimicrobial susceptibility testing showed that 0.4–1.3 mg/L of CHX can be sublethal to AS. Our work provided new insights into the fate of CHX in urban waste streams and the potential toxicity and effects on the structure and function of AS, which has practical implications for the management of biological WWTPs treating CHX.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Activated sludge-inoculated bioreactors removed 70–80% of CHX at steady state. </LI> <LI> CHX was removed in activated sludge largely by biosorption. </LI> <LI> CHX could be inhibitory to activated sludge at environmentally relevant levels. </LI> <LI> CHX selected for <I>Luteolibacter</I> and <I>Runella</I> with potential multi-drug resistance mechanisms. </LI> <LI> CHX reduced core members of activated sludge<I>.</I> </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Metal-organic frameworks (MOFs) as futuristic options for wastewater treatment

Kumar, Pawan,Bansal, Vasudha,Kim, Ki-Hyun,Kwon, Eilhann E. Elsevier 2018 Journal of industrial and engineering chemistry Vol.62 No.-

<P><B>Abstract</B></P> <P>To date, the utilization of metal-organic frameworks (MOFs) is found from numerous fields of applications including separation, storage, sensing, and many other miscellaneous ones. Their feasibility toward wastewater treatment (WWT) for several pollutants (e.g., heavy metal ions, pesticides, volatile organic pollutants (VOCs), and other hazardous chemicals) has not yet been thoroughly evaluated. Here, we attempted to provide the current technical advances associated with MOF-based WWT in reference to conventional materials. Our review emphasized current perspectives on contamination processes in water systems and performance of MOF in diverse WWT applications.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Metal-organic frameworks (MOFs) as futuristic options for wastewater treatment

Pawan Kumara,Vasudha Bansal,김기현,Eilhann E.Kwon 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.62 No.-

To date, the utilization of metal-organic frameworks (MOFs) is found from numerous fields of applications including separation, storage, sensing, and many other miscellaneous ones. Their feasibility toward wastewater treatment (WWT) for several pollutants (e.g., heavy metal ions, pesticides, volatile organic pollutants (VOCs), and other hazardous chemicals) has not yet been thoroughly evaluated. Here, we attempted to provide the current technical advances associated with MOF-based WWT in reference to conventional materials. Our review emphasized current perspectives on contamination processes in water systems and performance of MOF in diverse WWT applications.

Metal–organic framework composites as electrocatalysts for electrochemical sensing applications

Kempahanumakkagari, Sureshkumar,Vellingiri, Kowsalya,Deep, Akash,Kwon, Eilhann E.,Bolan, Nanthi,Kim, Ki-Hyun Elsevier 2018 Coordination chemistry reviews Vol.357 No.-

<P><B>Abstract</B></P> <P>Metal–organic frameworks (MOFs) are porous coordination polymers linked by metal ions and ligands. With the progress of MOF research, many redox active MOFs have been synthesized by judicious selection of the electroactive metal ions and/or organic functional groups. Due to the unique properties (e.g., high surface areas, tailorable pore sizes, and exposed active sites), MOFs are found to have a wide range of redox activities to be applied in various fields (e.g., microporous conductors, electrocatalysts, energy storage devices, and electrochemical sensors). The potential of the MOFs composites has also been realized as ideal hosts for functional materials (like conducting nanoparticles). These composites are thus demonstrated to have superior electrocatalytic/electrochemical sensing properties than their pristine forms. Accordingly, various MOF composite-based platforms have been developed as efficient electrochemical sensors for environmental and biochemical targets. This review was organized to provide up-to-date information and insights into the fundamental aspects of MOF composites as electrocatalytic/electrochemical sensors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MOF composites have been developed with superior electrocatalytic properties. </LI> <LI> MOF composites can be applied as electrocatalysts for electrochemical sensing. </LI> <LI> They were employed for sensing environmental analytes like metals and organics. </LI> <LI> Their use was extended further to detect various biological targets like glucose. </LI> </UL> </P>

Recovery of nanomaterials from battery and electronic wastes: A new paradigm of environmental waste management

Dutta, Tanushree,Kim, Ki-Hyun,Deep, Akash,Szulejko, Jan E.,Vellingiri, Kowsalya,Kumar, Sandeep,Kwon, Eilhann E.,Yun, Seong-Taek Elsevier 2018 RENEWABLE & SUSTAINABLE ENERGY REVIEWS Vol.82 No.3

<P><B>Abstract</B></P> <P>Recycling battery and electronic wastes for the recovery of nanomaterials (NMs) has ushered in a new era in nanotechnology and environmental research. Essentially, NM recycling offers a two-way method of environmental remediation. The potential economic benefits of high-value NM end-products are conducive for industrial scale operations. Simultaneously, it reduces the industrial consumption of finite primary resources. The added benefits of abating environmental pollution (e.g., from VOCs, VFAs, SO<SUB>2</SUB>, NOx, and heavy metals) further contributes to the significance of ongoing research in this particular area. However, some challenges still persist due to the lack of motivation for recycling and the problem of the limited usability (or low stability) of many of the end-products. In this study, we aimed to evaluate different basic aspects of waste recycling in relation to NM recovery, along with other associated techniques. The utility of recovered NMs and potential options for NM recovery are described as highlighting features to help construct a future roadmap for this emerging scientific field. In addition, an assessment of the potential economic returns from recycling high-purity NMs is provided. Outcomes of this review may fuel further innovations for optimizing the current recycling methods for the efficient synthesis of commercial-grade, high purity NMs at minimal cost.</P>

Production of 5-hydroxymethylfurfural from starch-rich food waste catalyzed by sulfonated biochar

Cao, Leichang,Yu, Iris K.M.,Chen, Season S.,Tsang, Daniel C.W.,Wang, Lei,Xiong, Xinni,Zhang, Shicheng,Ok, Yong Sik,Kwon, Eilhann E.,Song, Hocheol,Poon, Chi Sun Elsevier 2018 Bioresource technology Vol.252 No.-

<P><B>Abstract</B></P> <P>Sulfonated biochar derived from forestry wood waste was employed for the catalytic conversion of starch-rich food waste (e.g., bread) into 5-hydroxymethylfurfural (HMF). Chemical and physical properties of catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, and elemental analysis. The conversion of HMF was investigated via controlling the reaction parameters such as catalyst loading, temperature, and reaction time. Under the optimum reaction conditions the HMF yield of 30.4 Cmol% (i.e., 22 wt% of bread waste) was achieved in the mixture of dimethylsulfoxide (DMSO)/deionized-water (DIW) at 180 °C in 20 min. The effectiveness of sulfonated biochar catalyst was positively correlated to the density of strong/weak Brønsted acidity (SO<SUB>3</SUB>H, COOH, and OH groups) and inversely correlated to humins content on the surface. With regeneration process, sulfonated biochar catalyst displayed excellent recyclability for comparable HMF yield from bread waste over five cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> HMF yield of 30.4 Cmol% (∼20 wt%) from bread waste was achieved at 180 °C in 20 min. </LI> <LI> SBC loading, temperature, and reaction time controlled starch conversion route. </LI> <LI> HMF yield was in line with the total acidity density (TAD) of SBC. </LI> <LI> TAD of recovered biochar catalysts was inversely correlated with humins content. </LI> <LI> With regeneration, SBC displayed comparable performance and excellent recyclability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>