Evaluation of the Performance of Structured Mixed Packing and Inert Packing Materials in Toluene Biotrickle-filtration

Duanfang Sun,Jianjun Li,Taicheng An,Meiying Xu,Guoping Sun,Jun Guo 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.5

Packing materials play a key role in waste gas treatment. Organic and inert packing materials have their disadvantages, which may be minimized by mixed packing. In this study, various operating conditions were applied to evaluate the performance of structured mixed packing and inert packing materials in toluene biotricklefiltration. Four biotrickle filters were packed with structured mixed packing materials, namely, ceramic pall rings,ceramic rashig rings, and lava rock. Their toluene removal capacity was studied for 217 day using a laboratory-scale reaction under various operating conditions. The key elimination capacity (removal efficiency > 95%) ranking of the biotrickle filters was as follows: Structured mixed packing (306.20 ± 7.90 g/m^3/h) > pall ring (156.71 ± 7.84 g/m^3/h)> rashig ring (153.31 ± 6.14 g/m^3/h) > lava rock (150.32 ±9.19 g/m^3/h). The structured mixed packing and inert packing resulted in excellent toluene-degrading biofilter performance under long-term operation. The structured mixed packing provided a more rapid startup rate and better process robustness than the inert packing did. The biotrickle filter with mixed packing materials had a high elimination capacity which makes it suitable for various real-life applications, whereas the capability of the inert packing material was more suitable for treating a steady low toluene load.

Bacterial Community Diversity and Functional Gene Abundance of Structured Mixed Packing and Inert Packing Materials Based Biotrickling Filters

Duanfang Sun,Jianjun Li,Taicheng An,Meiying Xu,Guoping Sun,Jun Guo 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.3

Packing is the most important factor in biofilter design. A structured mixed packing (SMP) material, combined with various organic and inorganic materials (mineral matter is 80.18 ± 0.48%, w : w), was constructed by ureaformaldehyde resin in order to minimize the disadvantages of these materials when used as stand-alone components. The performance of the toluene biotrickling filter (BTF)packed with SMP was compared with the other BTFs packed with a ceramic raschig ring, ceramic pall ring, and lava rock, respectively, for 217 day under various operating conditions. Real-time PCR and DGGE techniques were applied to reveal the gene coding for the toluene-degrading enzymes and the bacterial community structure in the BTFs. The toluene-degradation gene copies exponentially increased, and bacterial diversity significantly decreased with the improving elimination capacities of the BTFs. The overload and shutdown operations resulted in insignificant fluctuations in the toluene-degradation gene copies at equal levels as well as a slight variation in the bacterial community structures in the BTFs. Various putative toluenedegrading bacteria were found using sequencing bands from the DGGE gels; some bacteria, such as Burkholderia spp., were further confirmed by real-time PCR; other bacteria,such as Alcaligenes spp., might not have been reported. The packing properties of SMP material supported more toluene-degradation gene copies in the biofilm, and higher toluene-degrading bacterial diversity of the BTF, than did inert packing. Thus, the BTF with SMP demonstrated excellent performance, suggesting the suitability of SMP for real applications, whereas the capabilities of inert packing materials are more suited to the treatment of steady low VOC loads. Packing is the most important factor in biofilter design. A structured mixed packing (SMP) material, combined with various organic and inorganic materials (mineral matter is 80.18 ± 0.48%, w : w), was constructed by ureaformaldehyde resin in order to minimize the disadvantages of these materials when used as stand-alone components. The performance of the toluene biotrickling filter (BTF)packed with SMP was compared with the other BTFs packed with a ceramic raschig ring, ceramic pall ring, and lava rock, respectively, for 217 day under various operating conditions. Real-time PCR and DGGE techniques were applied to reveal the gene coding for the toluene-degrading enzymes and the bacterial community structure in the BTFs. The toluene-degradation gene copies exponentially increased, and bacterial diversity significantly decreased with the improving elimination capacities of the BTFs. The overload and shutdown operations resulted in insignificant fluctuations in the toluene-degradation gene copies at equal levels as well as a slight variation in the bacterial community structures in the BTFs. Various putative toluenedegrading bacteria were found using sequencing bands from the DGGE gels; some bacteria, such as Burkholderia spp., were further confirmed by real-time PCR; other bacteria,such as Alcaligenes spp., might not have been reported. The packing properties of SMP material supported more toluene-degradation gene copies in the biofilm, and higher toluene-degrading bacterial diversity of the BTF, than did inert packing. Thus, the BTF with SMP demonstrated excellent performance, suggesting the suitability of SMP for real applications, whereas the capabilities of inert packing materials are more suited to the treatment of steady low VOC loads.

Toluene Removal Efficiency, Process Robustness, and Bacterial Diversity of a Biotrickling Filter Inoculated with Burkholderia sp. Strain T3

Duanfang Sun,Jianjun Li,MEI-YING XU,Taicheng An,GUO-PING SUN,JUN GUO 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.1

Microorganisms determine the overall biofilter performance under specific operating conditions. The toluene removal and process robustness of a laboratoryscale,ceramisite-based biotrickling filter inoculated with Burkholderia sp. strain T3 (BTFb) were compared with those of another biotrickling filter inoculated with activated sludge (BTFa) for 3 months under various operating conditions. Denaturing gradient gel electrophoresis was applied to visualise the bacterial community of the BTFa and BTFb. Real-time polymerase chain reaction was performed to determine the genes coding for toluenedegrading enzymes. Burkholderia sp. strain T3, which possesses the major toluene-degrading genes in BTFb, was traced in the BTFb bacterial community. The strain was found to stabilize the relative quantity steadily at higher than 60% during toluene biofiltration. Thus, BTFb performed more efficiently than BTFa as evidenced by achieving 98.86% toluene removal efficiency (RE) on 3 day, critical elimination capacity (EC) of 234.23 ± 10.54 g/m3/h, and rapid restoration of the initial RE and EC levels within 3 day of reoperation, even after 1 month of shutdown. The efficiency of BTFb is also evident by the stabilised RE and EC levels within a wide temperature range and a gradually decreasing system pH. Maintaining the pressure drop levels below 150 Pa during prolonged operation also contributed to the efficiency of BTFb. Thus, based on the study results,we propose that Burkholderia sp. strain T3 is a highly efficient and applicable inoculum for toluene biofiltration.

Treatment of Volatile Organic Compounds from a Typical Waste Printed Circuit Board Dismantling Workshop by a Pilot-scale Biotrickling Filter

Dongqi Liao,Jianjun Li,Duanfang Sun,Meiying Xu,Taicheng An,Guo-Ping Sun 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.4

A pilot-scale biotrickling filter (BTF) was designed to treat volatile organic compounds (VOCs) emitted from a typical waste printed circuit board (WPCB) pyrolysis workshop. Measured by gas chromatography-mass spectrometry (GC-MS), the main components of VOCs and their concentrations were benzene, toluene, chlorobenzene, ethyl-benzene, xylene, styrene, benzaldehyde, and trimethyl-benzene. The removal efficiencies of the BTF for these compounds ranged from 81.1 to 97.8% after 90 days of operation. The maximum elimination capacity of 25.94 g/m3 h was obtained with the inlet loading of 30.72 g/m3 fixed the fixed empty-bed residence time (EBRT) of 9.80 sec. Hazard ratio index based on threshold limit value for time weighted average (TLV-TWA) and VOCs concentrations indicated that the cancer risk of VOCs was significantly reduced after the BTF treatment. The microbial community analysis revealed initial inoculum and some emerging bacteria played crucial roles in the improvement of BTF performance with the biodegradation of this kind of VOCs by the polymerase chain reactiondenaturing gradient gel electrophoresis (PCR-DGGE) technique and pyrosequencing analyses indicated that proteobacteria phylum was the dominant in the BTF. All above results indicated that VOCs with multicomponent and fluctuant concentrations from a typical waste printed circuit board pyrolysis workshop were removed efficiently and in an environmentally friendly way by the biofiltration method.

Activation of peroxymonosulfate on visible light irradiated TiO₂ via a charge transfer complex path

Jo, Yoosang,Kim, Chuhyung,Moon, Gun-Hee,Lee, Jaesang,An, Taicheng,Choi, Wonyong Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.346 No.-

<P><B>Abstract</B></P> <P>Photo-induced activation of peroxymonosulfate (PMS) has been enabled by either the direct photolysis of the peroxide bond or the semiconductor bandgap-excited photocatalysis. Whereas the existing approaches utilize UV light, this study first studied the utilization of visible light for the PMS activation in which the dual roles of PMS as a complexing ligand on TiO<SUB>2</SUB> and a precursor of sulfate radical (SO<SUB>4</SUB> <SUP> −</SUP>) are enabled via ligand-to-metal charge transfer (LMCT) mechanism. In this LMCT-mediated photocatalysis, PMS coordinated to TiO<SUB>2</SUB> as a surface complex is photoexcited by visible light to inject electrons to the CB of TiO<SUB>2</SUB>, which subsequently activate PMS to yield SO<SUB>4</SUB> <SUP> −</SUP>. Despite the lack of visible light activity of both TiO<SUB>2</SUB> and PMS, the addition of PMS induced a significant degradation of 4-chlorophenol and dichloroacetate on TiO<SUB>2</SUB> under visible light irradiation. Together with several spectroscopic analyses, the result revealed the formation of an interfacial charge transfer (CT) complex of PMS on TiO<SUB>2</SUB> and the LMCT-mediated PMS conversion into SO<SUB>4</SUB> <SUP> −</SUP>. Multi-activity assessment showed that the oxidizing capacity of TiO<SUB>2</SUB>/PMS varied depending on the substrate type; benzoic acid and acetaminophen were rapidly decomposed whereas nitrophenol oxidation was insignificant. The role of SO<SUB>4</SUB> <SUP> −</SUP> as the main oxidant was identified based on (1) quenching effect of methanol as a radical quencher, (2) coumarin hydroxylation as an indication of SO<SUB>4</SUB> <SUP> −</SUP> formation, and (3) EPR spin-trapping technique. The comparison of TiO<SUB>2</SUB>/PMS <I>versus</I> Co<SUB>3</SUB>O<SUB>4</SUB>/PMS suggested that the repeated acetaminophen decay was achievable with TiO<SUB>2</SUB>/PMS without the loss of activating capacity whereas a gradual reduction in degradation efficiency was observed with Co<SUB>3</SUB>O<SUB>4</SUB>/PMS.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PMS serves as a complexing ligand and a radical precursor in the activation process. </LI> <LI> Visible light irradiation activates PMS on TiO<SUB>2</SUB> via ligand-to-metal charge transfer. </LI> <LI> The TiO<SUB>2</SUB>/PMS/visible light system shows catalytic performance in organic oxidation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Persistent free radicals in carbon-based materials on transformation of refractory organic contaminants (ROCs) in water: A critical review

Qin, Yaxin,Li, Guiying,Gao, Yanpeng,Zhang, Lizhi,Ok, Yong Sik,An, Taicheng Elsevier 2018 Water research Vol.137 No.-

<P><B>Abstract</B></P> <P>With the increased concentrations and kinds of refractory organic contaminants (ROCs) in aquatic environments, many previous reviews systematically summarized the applications of carbon-based materials in the adsorption and catalytic degradation of ROCs for their economically viable and environmentally friendly behavior. Interestingly, recent studies indicated that carbon-based materials in natural environment can also mediate the transformation of ROCs directly or indirectly due to their abundant persistent free radicals (PFRs). Understanding the formation mechanisms of PFRs in carbo-based materials and their interactions with ROCs is essential to develop their further applications in environment remediation. However, there is no comprehensive review so far about the direct and indirect removal of ROCs mediated by PFRs in amorphous, porous and crystalline carbon-based materials. The review aims to evaluate the formation mechanisms of PFRs in carbon-based materials synthesized through pyrolysis and hydrothermal carbonization processes. The influence of synthesis conditions (temperature and time) and carbon sources on the types as well as the concentrations of PFRs in carbon-based materials are also discussed. In particular, the effects of metals on the concentrations and types of PFRs in carbon-based materials are highlighted because they are considered as the catalysts for the formation of PFRs. The formation mechanisms of reactive species and the further transformation mechanisms of ROCs are briefly summarized, and the surface properties of carbon-based materials including surface area, types and number of functional groups, etc. are found to be the key parameters controlling their activities. However, due to diversity and complexity of carbon-based materials, the exact relationships between the activities of carbon-based materials and PFRs are still uncertain. Finally, the existing problems and current challenges for the ROCs transformation with carbon-based materials are also pointed out.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Abundant of PFRs formed in carbon-based materials during the synthesis process. </LI> <LI> The PFRs types and concentrations affected by synthesis conditions. </LI> <LI> The PFRs can activate oxidants and reductants to degrade organic contaminants. </LI> <LI> The PFRs can directly react with organic contaminants. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhanced photocatalytic mechanism of Ag₃PO₄ nano-sheets using MS₂ (M = Mo, W)/rGO hybrids as co-catalysts for 4-nitrophenol degradation in water

Zhang, Weiping,Li, Guiying,Wang, Wanjun,Qin, Yaxin,An, Taicheng,Xiao, Xinyan,Choi, Wonyong Elsevier 2018 Applied Catalysis B Vol.232 No.-

<P><B>Abstract</B></P> <P>A chemically modified Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>(M = Mo, W)/rGO composite was firstly synthesized via a liquid-exfoliation solvothermal method. The structure, morphology, optical properties and composition were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, UV–vis diffuse reflectance spectra and X-ray photoelectron spectroscopy, respectively. The characterization results indicated that compact structure could be obtained by using this typical method due to in-situ chemical modification, which could also control the sizes of Ag<SUB>3</SUB>PO<SUB>4</SUB> nano-sheets by adding MS<SUB>2</SUB>/rGO hybrids. More importantly, the resultant Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO composite exhibited higher photocatalytic activity and stability toward the degradation of 4-nitrophenol than pure Ag<SUB>3</SUB>PO<SUB>4</SUB> under sunlight irradiation. The stable structure of Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO was closely related with Z-scheme electronic structure and electrical conductivity of MS<SUB>2</SUB>/rGO hybrids, leading to a higher consumption and transfer of photogenerated electrons. However, by controlling the amounts of MS<SUB>2</SUB>/rGO hybrids, more stable but lower photocatalytic activity composites could be obtained. Further analysis found that the holes and O<SUB>2</SUB> <SUP>−</SUP> were the main reactive species involved in the photocatalytic degradation of 4-nitrophenol. In addition, possible photocatalytic degradation pathways of 4-nitrophenol were also proposed based on the identified intermediates. The findings of this work may provide a new method to design efficient composites for photocatalytic degradation of organic pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO catalyst was fabricated via a liquid-exfoliation solvothermal method. </LI> <LI> Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO has high photocatalytic activity and stability under sunlight. </LI> <LI> The stability of Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO was due to its rapid transfer of photogenerated e<SUP>−</SUP>. </LI> <LI> h<SUP>+</SUP> and O<SUB>2</SUB> <SUP>−</SUP> were the main RSs in photocatalytic degradation of 4-nitrophenol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>