A comparison of figure of merit (FOM) for various materials in adsorptive removal of benzene under ambient temperature and pressure

Khan, Azmatullah,Szulejko, Jan E.,Kim, Ki-Hyun,Sammadar, Pallabi,Lee, Sang Soo,Yang, Xiao,Ok, Yong Sik Elsevier 2019 Environmental research Vol.168 No.-

<P><B>Abstract</B></P> <P>To effectively remove gaseous pollutants from air using sorbents, a thorough knowledge of the actual sorption performance is needed at ambient conditions rather than at unrealistically high-pressure conditions, as is commonly presented in the literature. To this end, the sorbent capacities of gaseous benzene were evaluated at a constant sorbent bed inlet pressure (50 ppm or ~5 Pa) in 1 atm of N<SUB>2</SUB>, room temperature (298 K), a fixed flow rate (50 mL min<SUP>−1</SUP>), and equal outlet sampling intervals (5 min). The benzene adsorption patterns were investigated against six sorbent types in a total of 17 different forms: 1- zeolite in five forms: beads (ZB), ground to 212 µm (ZG212), beads ground to 300 µm (ZG300), coarsely ground/washed zeolite (ZWc), and coarsely ground/washed/thermally treated zeolite (ZTc), 2- activated carbon in two forms: 212 µm (ACd212) and granular (ACdg), 3- Carbopack-X (CX), 4- Tenax TA (TA), 5- used black tea leaves of 150 or 300 µm in three forms: dry (TD150/TD300), wet (TW150/TW300), and wet dust (TWd), and 6- used ground coffee in either dry (CD) or wet forms (CW). Accordingly, the largest adsorption capacities at 5 Pa (e.g., >10 mg g<SUP>−1</SUP>) were observed for ACd212 (79.1) and ACdg (73.6). Moderate values (e.g., 5 < < 10 mg g<SUP>−1</SUP>) were obtained for ZG212 (7.98), CX (6.79), ZG300 (5.70), and ZB (5.58), while the remainder were far lower at < 5 mg g<SUP>−1</SUP> (e.g., tea leaves, ground coffee, TA, ZWc, and ZTc). The experimental benzene capacities of the tested sorbents were further assessed by the Langmuir, Henry's law, Freundlich, Dubinin-Radushkevich, and Elovich isotherm models. The linearized Langmuir adsorption isotherms of ACd212, ACdg, and CX showed the presence of more than one adsorption site (i.e., retrograde at the lowest pressures and two others at higher pressures). However, TA, zeolite, tea leaves, and ground coffee exhibited a type-V isotherm, wherein the sorption capacity continued to increase with loaded volume (i.e., multilayer adsorption). Thus, ACd212 has the best figure-of-merit based on a high 10% breakthrough volume (BTV) and low cost for real-world applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Activated carbon (ACd212) has retrograde isotherm. </LI> <LI> The ground sorbent has higher BTV compare to granular sorbent. </LI> <LI> The Langmuir adsorption isotherms identified more than one adsorption site. </LI> <LI> Tea leaves and ground coffee followed multilayer adsorption isotherm. </LI> <LI> The practicality of different sorbents is finally evaluated in terms of FOM. </LI> </UL> </P>

Movement of Heavy Metals from Soil to Human Food Chain and Risk Assessment

Xiao-E Yang,Wendan Xiao,Mahamad Tarig,Zhenli He 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Atrasentan (ABT-627) enhances perfusion and reduces hypoxia in a human tumor xenograft model.

Yang, Kwang Mo,Russell, James,Lupu, Mihaela E,Cho, Hyungjoon,Li, Xiao-Feng,Koutcher, Jason A,Ling, C Clifton Landes Bioscience 2009 Cancer Biology & Therapy Vol.8 No.20

<P>The endothelin-1 antagonist, Atrasentan (ABT-627) was used to modify perfusion in the human tumor xenograft model, HT29, growing in nude mice. Atrasentan produced a significant increase in perfusion, as measured in vivo by Gd-DTPA DCE-MRI. Changes in tumor hypoxia were assessed by comparing the binding of two hypoxia tracers, pimonidazole and EF5 given before and after Atrasentan administration. In vehicle-treated controls, the distribution of EF5 and pimonidazole was very similar. However, Atrasentan treatment was associated with decreased uptake of the second hypoxia tracer (EF5), relative to the first (pimonidazole). Although Atrasentan had no independent effect on the growth of HT29 tumors, Atrasentan combined with 20 Gy radiation led to a modest but significant increase in tumor growth delay compared to radiation alone.</P>

Effect of the Oxygen Flux Ratio on the Structural and the Optical Properties of Silver-oxide Films Deposited by Using the Direct-current Reactive Magnetron Sputtering Method

Xiao-Yong Gao,Hong-Liang Feng,Zeng-Yuan Zhang,Jiao-Min Ma,Meng-Ke Zhao,Chao Chen,Jin-Hua Gu,Shi-E Yang,Yong-Sheng Chen,Jing-Xiao Lu 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.2

Using values of the oxygen flux ratio (OFR = [O2]/[Ar]) ranging from 0 to 0.5, authors deposited a series of silver-oxide (Ag_xO) films on glass substrates by direct-current reactive magnetron sputtering (DC sputtering) at a substrate temperature of 150 ℃. The effect of the OFR on the film’s structural and optical properties was systematically investigated by using X-ray diffractometry, scanning electron microscopy and spectrophotometry. The Ag_xO films deposited clearly show an evolution of the film’s phase structure from the biphased (Ag + Ag_2O) structure to the biphased (AgO + Ag_2O) structure and then to the single-phased (Ag_2O) structure as value of the OFR increases. Accordingly, the film’s surface morphology, related to the film’s crystalline structure, clearly changes from a loose and porous surface structure to a compact surface structure and then to a pyramid-like surface structure with increasing value of the OFR. The novel porous structure may be attributed to the interruption of the silver’s growth course by the AgO on the film’s surface. Notably, a single-phased Ag_2O film is deposited by DC-sputtering at OFR = 0.5 due to the dual effects of thermal decomposition of the AgO phase and a combination reaction of AgO and Ag to Ag_2O. The oscillations both in the film’s reflectivity and transmissivity spectra are strengthened with increasing OFR, indicating an evolution from the metallic behavior of the biphased (Ag + Ag_2O) film to the dielectric behavior of the biphased (Ag_2O + AgO) film and the single-phased Ag2O film. The fitted optical absorption edges of the Ag_2O and the Ag_xO films deposited at values of the OFR of 0.5 and 0.33 are approximately 2.43 eV and 2.34 eV, respectively. The absorption edges are closely related to the direct interband transitions.

Characterization of bioenergy biochar and its utilization for metal/metalloid immobilization in contaminated soil

Yang, Xiao,Igalavithana, Avanthi D.,Oh, Sang-Eun,Nam, Hyungseok,Zhang, Ming,Wang, Chi-Hwa,Kwon, Eilhann E.,Tsang, Daniel C.W.,Ok, Yong Sik Elsevier 2018 The Science of the total environment Vol.640 No.-

<P><B>Abstract</B></P> <P>This study is a comparison of the effect of biochar produced by bioenergy systems, via the pyrolysis and gasification processes, on the immobilization of metals/metalloids in soil. Because the processes for these two techniques vary, the feedstocks undergo different heating regimens and, as a result, their respective char products exhibit different physico-chemical properties. Therefore, this study focuses on (1) the characterization of derivative biochar from the bioenergy system to understand their features and (2) an exploration of various biochar impacts on the mobility of As and Pb in contaminated soil. The results showed bioenergy biochars (BBCs) performed well in mitigating Pb extractability (1 M ammonium acetate) with a Pb immobilization >80%, but unfavorably mobilized the bioavailable As, likely because of electrostatic repulsion and ion exchange competition. The BBC surface functional group would chemically bond with the As and remain stable against the pH change. An increment in aromatic carbon would effectively enhance cation-π interaction for Pb immobilization. Nevertheless, an amendment with richer condensed structure and higher inorganic minerals (Ca<SUP>2+</SUP>, K<SUP>+</SUP>, Mg<SUP>2+</SUP>, and Na<SUP>+</SUP>) can lead to better performance in retaining Pb.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bioenergy system biochars (BBC) can be used to mitigate the bioavailability of metal(loid) pollutants in soil. </LI> <LI> The use of oxidizing gas in bioenergy technology can increase the surface functionality of the carbonaceous by-product. </LI> <LI> BBC characteristics are closely related to the immobilization performance of Pb and As in soil. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fabrication of spherical biochar by a two-step thermal process from waste potato peel

Yang, Xiao,Kwon, Eilhann E.,Dou, Xiaomin,Zhang, Ming,Kim, Ki-Hyun,Tsang, Daniel C.W.,Ok, Yong Sik Elsevier 2018 Science of the Total Environment Vol.626 No.-

<P><B>Abstract</B></P> <P>The aim of this study was to develop a new approach for the preparation of spherical biochar (SBC) by employing a two-step thermal technology to potato peel waste (PPW). Potato starch (PS), as a carbon-rich material with microscale spherical shape, was separated from PPW as a precursor to synthesizing SBC. The synthesis process comprised (1) pre-oxidization (preheating under air) of PS at 220 °C and (2) subsequent pyrolysis of the pretreated sample at 700 °C. Results showed that the produced SBC successfully retained the original PS morphology and that pre-oxidization was the key for its shape maintenance, as it reduced surface tension and enhanced structural stability. The SBC possessed excellent chemical inertness (high aromaticity) and uniform particle size (10–30 μm). Zero-cost waste material with a facile and easy-to-control process allows the method to be readily scalable for industrialization, while offering a new perspective on the full use of PPW.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Potato starch (PS) derived from potato peel waste (PPW) has highly regular spherical shape. </LI> <LI> PS morphology was retained with pre-oxidation process after pyrolysis. </LI> <LI> PS's spherical shape affords great homogeneity to the produced biochar. </LI> <LI> Mechanism of shape maintenance was studied via various spectral characterizations. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Novel Multi-Path Routing Algorithm Based on Clustering for Wireless Mesh Networks

( Chun-xiao Liu ),( Yan Zhang ),( E Xu ),( Yu-qiang Yang ),( Xu-hui Zhao ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.4

As one of the new self-organizing and self-configuration broadband networks, wireless mesh networks are being increasingly attractive. In order to solve the load balancing problem in wireless mesh networks, this paper proposes a novel multi-path routing algorithm based on clustering (Cluster_MMesh) for wireless mesh networks. In the clustering stage, on the basis of the maximum connectivity clustering algorithm and k-hop clustering algorithm, according to the idea of maximum connectivity, a new concept of node connectivity degree is proposed in this paper, which can make the selection of cluster head more simple and reasonable. While clustering, the node which has less expected load in the candidate border gateway node set will be selected as the border gateway node. In the multi-path routing establishment stage, we use the intra-clustering multi-path routing algorithm and inter-clustering multi-path routing algorithm to establish multi-path routing from the source node to the destination node. At last, in the traffic allocation stage, we will use the virtual disjoint multi-path model (Vdmp) to allocate the network traffic. Simulation results show that the Cluster_MMesh routing algorithm can help increase the packet delivery rate, reduce the average end to end delay, and improve the network performance.

Effects of carbon dioxide on pyrolysis of peat

Lee, Jechan,Yang, Xiao,Song, Hocheol,Ok, Yong Sik,Kwon, Eilhann E. Elsevier 2017 ENERGY Vol.120 No.-

<P><B>Abstract</B></P> <P>This study focuses on the mechanistic understanding of effects of CO<SUB>2</SUB> on pyrolysis of peat. To do this, three pyrolytic products (<I>i.e.</I>, syngas: H<SUB>2</SUB> and CO, pyrolytic oil (tar), and biochar) were characterized. Thermal cracking of volatile organic carbons (VOCs) generated from pyrolysis of peat was enhanced in the presence of CO<SUB>2</SUB>. Besides the enhanced thermal cracking of VOCs, unknown reaction between CO<SUB>2</SUB> and VOCs was also identified. Accordingly, CO<SUB>2</SUB> played a role in enhancing syngas production and in reducing tar formation in pyrolysis of peat. This study also reveals that peat-biochar produced in CO<SUB>2</SUB> exhibited a larger surface area than that produced in N<SUB>2</SUB>. The results shown in this paper would be used for various applications such as energy recovery from peat using a potent greenhouse gas (for example, CO<SUB>2</SUB>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> More CO can be produced from pyrolysis of peat in CO<SUB>2</SUB> than in N<SUB>2</SUB>. </LI> <LI> Less amount of tar produced from pyrolysis of peat in CO<SUB>2</SUB> than in N<SUB>2</SUB>. </LI> <LI> Surface area of peat-biochar made in CO<SUB>2</SUB> is larger than that made in N<SUB>2</SUB>. </LI> <LI> CO<SUB>2</SUB> can modify the quantity/quality of pyrolytic products from peat. </LI> </UL> </P>

Metal(loid) immobilization in soils with biochars pyrolyzed in N₂ and CO₂ environments

Igalavithana, Avanthi Deshani,Yang, Xiao,Zahra, Hilda Rizkia,Tack, Filip M.G.,Tsang, Daniel C.W.,Kwon, Eilhann E.,Ok, Yong Sik Elsevier 2018 Science of the Total Environment Vol.630 No.-

<P><B>Abstract</B></P> <P>Previous studies indicated that using CO<SUB>2</SUB> as a reaction agent in the pyrolysis of biomass led to an enhanced generation of syngas <I>via</I> direct reaction between volatile organic carbons (VOCs) evolved from the thermal degradation of biomass and CO<SUB>2</SUB>. In addition, the physico-chemical properties of biochar in CO<SUB>2</SUB> were modified. In this current study, biochars generated from red pepper stalks in N<SUB>2</SUB> and CO<SUB>2</SUB> (RPS-N and RPS-C, respectively) were tested for their effects on the immobilization of Pb, Cd, Zn, and As in contaminated soils. Soils were incubated for one month with 2.5% of RPS, and two biochars (<I>i.e.</I>, RPS-N and RPS-C) at 25°C. After the incubation period soils were analyzed to determine the amendment effects on the behavior of metal(loid)s. The potential availability and mobility kinetics of metal(loid)s were assessed by single extraction of ammonium acetate and consecutive extraction of calcium chloride, respectively. Sequential extraction was used to further examine potential changes in geochemical fractions of metal(loid)s. The increased soil pH induced by application of the biochars reduced the potentially available Pb, Cd, and Zn, while RPS-C significantly reduced Pb due to the high surface area and aromaticity of RPS-C. However, RPS-C mobilized potentially available As compared to RPS-N due to the increased soil pH. Biochars reduced the mobility kinetics of Pb, Cd, and Zn, and RPS-N effectuated the greatest reduction of As mobility. The RPS-C increased the Fe and Mn oxides, hydroxide, and organically bound Pb, while both biochars and RPS-N increased residual Cd and Zn, and organically bound As, respectively. When considering the two biochars, RPS-C was highly effective for immobilization of Pb in soils, but it had no effect on Cd and Zn and a negative effect on As. In addition, RPS-C significantly increased the total exchangeable cations in soils.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biochars markedly reduced Cd, Pb and Zn mobility in soils. </LI> <LI> Biochar pyrolyzed in CO<SUB>2</SUB> most effectively immobilized Pb. </LI> <LI> Biochar pyrolyzed in CO<SUB>2</SUB> increases As mobility more. </LI> <LI> More siloxane groups present in biochar pyrolysed in CO<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The potential of biochar as sorptive media for removal of hazardous benzene in air

Khan, Azmatullah,Szulejko, Jan E.,Samaddar, Pallabi,Kim, Ki-Hyun,Liu, Botao,Maitlo, Hubdar Ali,Yang, Xiao,Ok, Yong Sik Elsevier 2019 Chemical Engineering Journal Vol. No.

<P><B>Abstract</B></P> <P>Airborne benzene is hazardous even at sub-ppm levels. Therefore, an effective strategy is required for its removal, such as the use of a sorbent with large adsorption capacity or high breakthrough volume. To meet the goal, the performance for the removal of benzene was assessed by loading benzene at 5 Pa inlet partial pressure against seven types of biowaste-derived biochar: (1) paper mill sludge, (2) conventional biochar with magnetic properties, (3) biochar composites with carbon nanotubes (CNTs), (4) gasification biochar from mixed feedstock, (5) gasification biochar from a single feedstock, (6) modified gasification biochar, and (7) activated carbon (AC) as a reference. The 298 K maximum adsorption capacities (mg g<SUP>−1</SUP>), when measured at a benzene inlet pressure of 5 Pa (or 50 ppm in ultrapure nitrogen) and flow rate of 50 mL atm min<SUP>−1</SUP>, varied widely for different biochars, from 0.35 (MS: Swine manure + plastic mulch film waste) to 144 mg g<SUP>−1</SUP> (XC-1: biochar from mixed feedstock); their 10% breakthrough volumes (BTV) were in the range of 0.22–492 L g<SUP>−1</SUP>, respectively. The experimental data (capacity vs. benzene outlet partial pressure) could be fitted to either two or three linearized Langmuir isotherms with distinctive sorption mechanisms ((1) a retrograde region (Type III isotherm: 0 to ∼0.2 Pa), (2) an intermediate pressure region (0.2 and 2.0 Pa), and (3) a higher pressure region (>2 Pa)) which was also confirmed similarly by Freundlich, Dubinin–Radushkevich, and Elovich fitting. About 65% of the maximum capacity was achieved in the retrograde region. The strongest biochar sorbent, XC-1, showed similar performance as activated carbon to prove its feasibility toward air quality management (AQM) applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Performance of biochars for gaseous benzene removal was assessed. </LI> <LI> The adsorption isotherms were assessed by maximum capacity, partition coefficient, and BTV. </LI> <LI> Retrograde was found for activated carbon and gasified/modified biochars. </LI> <LI> The strong sorbents of multiple sorption sites fitted best with Elovich and Langmuir models. </LI> </UL> </P>