Developing a sorptive material of cadmium from pyrolysis of hen manure.

A large amount of manure is generated from concentrated animal feeding operations (CAFOs), leading to serious environmental issues and hazardous risks from pathogens, such as methicillin-resistant Staphylococcus aureus. Therefore, developing an effective method for manure disposal is essential. Thus, in this study, we suggest the use of CO2 in pyrolysis of hen manure (HM) as an effective method to convert the carbon in HM into syngas (especially carbon monoxide (CO)). HM was used and tested as the model compound. From the results of thermo-gravimetric analysis, the decarboxylation of CaCO3 in HM in the presence of N2 was realized at temperatures ranging from 638 to 754 °C. The Boudouard reaction was observed at ≥ 664 °C in the presence of CO2. Despite the lack of occurrence of the Boudouard reaction, more CO formation was observed in the presence of CO2 at ≥ 460 °C. This was deemed as a homogeneous reaction induced by CO2. Considering the high Ca content of HM, HM biochar in N2 and CO2 were used as adsorbent for removal of Cadmium (Cd), which is toxic heavy metal. The adsorption capacities of HM_N2 and HM_CO2 were 302.4 and 95.7 mg g-1, respectively. The superior performance of HM_N2 is mainly attributed to the presence of Ca(OH)2, which provides favorable (alkaline) conditions for precipitation and ion exchange. Our results indicate the environmental benefits from using CO2. Specifically, CO2 (representative greenhouse gas) converted into fuel. Given this, pyrolysis of HM in the presence of CO2 was achieved at ≤ 640 °C, and the atmospheric condition should be switched from CO2 to N2 at ≥ 640 °C to ensure the decarboxylation of CaCO3.

Environmental benefits from the use of CO2 in the thermal disposal of cigarette butts.

As the global consumption of cigarettes has increased, the massive generation of cigarette butts (CBs) has led to critical environmental and health problems. Landfilling or incineration of CBs has been conventionally carried out, but such disposal protocols have suffered from the potential risks of the unwanted/uncontrolled release of leachates, carcinogens, and toxic chemicals into all environmental media. Thus, this study focuses on developing an environmentally dependable method for CB disposal. Littered CBs from filtered/electronic cigarettes were valorized into syngas (H2/CO). To seek a greener approach for the valorization of CBs, CO2 was intentionally considered as a reaction intermediate. Prior to multiple pyrolysis studies, the toxic chemicals in the CBs were qualitatively determined. This study experimentally proved that the toxic chemicals in CBs were detoxified/valorized into syngas. Furthermore, this work demonstrated that CO2 was effective in thermally destroying toxic chemicals in CBs via a gas-phase reaction. The reaction features and CO2 synergistically enhance syngas production. With the use of a supported Ni catalyst and CO2, syngas production from the catalytic pyrolysis of CBs was greatly enhanced (approximately 4 times). Finally, the gas-phase reaction by CO2 was reliably maintained owing to the synergistic mechanistic/reaction feature of CO2 for coke formation prevention on the catalyst surface.

Iron-modified phosphorus- and silicon-based biochars exhibited various influences on arsenic, cadmium, and lead accumulation in rice and enzyme activities in a paddy soil.

Contamination of paddy soils with potentially toxic elements (PTEs) has become a severe environmental issue. Application of functionalized biochar for rice cultivation has been proposed as an effective means to reduce environmental risks of these PTEs in paddy soils. This work was undertaken to seek the positive effects of a rice husk-derived silicon (Si)-rich biochar (Si-BC) and a pig carcass-derived phosphorus (P)-rich biochar (P-BC), as well as their Fe-modified biochars (Fe-Si-BC and Fe-P-BC) on the enzyme activity and PTE availability in an As-Cd-Pb-contaminated soil. A rice cultivation pot trial was conducted using these functionalized biochars as soil amendments for the alleviation of PTE accumulation in rice plants. Results showed that Si-BC decreased the concentrations of As in rice grain and straw by 59.4 % and 61.4 %, respectively, while Fe-Si-BC significantly (P < 0.05) enhanced plant growth, increasing grain yield (by 38.6 %). Fe-Si-BC significantly (P < 0.05) elevated Cd and Pb accumulation in rice plants. P-BC enhanced the activities of dehydrogenase, catalase, and urease, and reduced grain-Pb and straw-Pb by 49.3 % and 43.2 %, respectively. However, Fe-P-BC reduced plant-As in rice grain and straw by 12.2 % and 51.2 %, respectively, but increased plant-Cd and plant-Pb. Thus, Fe-modified Si- and P-rich biochars could remediate paddy soils contaminated with As, and enhance the yield and quality of rice. Application of pristine P-rich biochar could also be a promising strategy to remediate the Pb-contaminated paddy soils and limit Pb accumulation in rice.

Valorization of aflatoxin contaminated peanut into biodiesel through non-catalytic transesterification.

Aflatoxins (AFs) are the extremely hazardous metabolites (carcinogens) that are sporadically observed in crops, and these toxic chemicals are indeed lethal to the health of living organisms including human beings. Thus, AF contaminated food waste needs to be disposed as an environmentally benign way, not releasing it into the environment. This study offered a sustainable disposal and valorization platform for AF contaminated food. Peanut was used as a model food waste, because AF is readily appeared in the peanut during its harvesting, cultivation, storage, transportation process. As the valorization platform, non-catalytic transesterification of AF contaminated peanut was employed to convert it to biodiesel (BD). From the process, lipid in AF contaminated peanut is converted into BD (95.2 wt% yield) at 365°C for 1 min. Since the boiling points of BD and AF are significantly different, this process could also resolve the separation problem of AF (180 °C) from BD (≥ 330 °C) during the transesterification reaction. As a comparison study, alkali-catalyzed reaction was done. The alkali-catalyzed one required a pretreatment process to extract peanut oil for transesterification. The highest yield was 67.8 wt% yield after 6 h of reaction at 65 °C.

Biochar heavy metal removal in aqueous solution depends on feedstock type and pyrolysis purging gas.

The effectiveness of biochar as a sorptive material to remove contaminants, particularly heavy metals, from water is dependent on biomass type and pyrolysis condition. Biochars were produced from pulp mill sludge (PMS) and rice straw (RS) with nitrogen (N2) or carbon dioxide (CO2) as the purging gas. The sorptive capacity of the biochars for cadmium(II), copper(II), nickel(II) and lead(II) was studied. The heavy metal adsorption capacity was mainly affected by biomass type, with biochars adsorption capacities higher for lead(II) (109.9-256.4 mg g-1) than for nickel(II) (40.2-64.1 mg g-1), cadmium(II) (29.5-42.7 mg g-1) and copper(II) (18.5-39.4 mg g-1) based on the Langmuir adsorption model. The highest lead(II) adsorption capacities for PMS and RS biochars were 256.4 and 133.3 mg g-1, respectively, when generated using N2 as the purging gas. The corresponding lead(II) adsorption capacities were 250.0 and 109.9 mg g-1, respectively, when generated using CO2 as the purging gas. According to the intraparticle diffusion model, 30-62% of heavy metal adsorption was achieved in 1 h; film diffusion was the rate-dominating step, whereas pore diffusion was a rate-limiting step. Ion exchange and complexation between heavy metals and biochar surface functional groups such as carbonyl and hydroxyl groups were effective mechanisms for heavy metal sorption from the aqueous solution. We conclude that proper selection of both the feedstock type and the purging gas is important in designing biochars for the effective removal of potentially toxic metals from wastewater.

Valorization of disposable COVID-19 mask through the thermo-chemical process.

It becomes common to wear a disposable face mask to protect from coronavirus disease 19 (COVID-19) amid this pandemic. However, massive generations of contaminated face mask cause environmental concerns because current disposal processes (i.e., incineration and reclamation) for them release toxic chemicals. The disposable mask is made of different compounds, making it hard to be recycled. In this regard, this work suggests an environmentally benign disposal process, simultaneously achieving the production of valuable fuels from the face mask. To this end, CO2-assisted thermo-chemical process was conducted. The first part of this work determined the major chemical constituents of a disposable mask: polypropylene, polyethylene, nylon, and Fe. In the second part, pyrolysis study was employed to produce syngas and C1-2 hydrocarbons (HCs) from the disposable mask. To enhance syngas and C1-2 HCs formations, multi-stage pyrolysis was used for more C-C and C-H bonds scissions of the disposable mask. Catalytic pyrolysis over Ni/SiO2 further expedited H2 and CH4 formations due to its capability for dehydrogenation. In the presence of CO2, catalytic pyrolysis additionally produced CO, while pyrolysis in N2 did not produce it. Therefore, the thermo-chemical conversion of disposable face mask and CO2 could be an environmentally benign way to remove COVID-19 plastic waste, generating value-added products.

Mitigation of harmful chemical formation from pyrolysis of tobacco waste using CO2.

Global consumption of tobacco has been continuously increasing. This results in the considerable generation of toxic waste materials from the tobacco industry and daily life. Conventional disposal methods for them (incineration and landfilling) could be a potential hazard for releasing carcinogens and toxins into our eco-system. Accordingly, an eco-friendly disposal platform for converting tobacco waste (TW) into syngas was mainly studied in this present work. To realize this, pyrolysis of two commercial cigarette products (Marlboro and HEETS (electronic cigarette)) was done under the CO2/N2 conditions. One of the main findings from the present study was that CO2 reacted with volatile matters (VMs) obtained from the thermolysis of TW through the gas phase reactions (GPRs), which provided a strategic measure to manipulate carbon rearrangement of all pyrolysates. In particular, the GPRs expedited the carbon rearrangement of harmful chemical species, converting toxic chemicals into syngas. When the fraction of VMs in TWs increased, the GPR were more effective. Therefore, the introduced eco-friendly method using CO2-mediated thermochemical process could be beneficial for energy recovery from TWs while mitigating the formations of harmful chemical species.

An efficient system for electro-Fenton oxidation of pesticide by a reduced graphene oxide-aminopyrazine@3DNi foam gas diffusion electrode.

A stable rGO-AmPyraz@3DNiF gas diffusion electrode was prepared via modification of 3D nickel foam (3D-NiF) with aminopyrazine functionalized reduced graphene oxide (rGO-AmPyraz) for the electro Fenton (EF) process. The generation capacity of H2O2 and OH radicals by this electrode was assessed relative to 3DNiF and rGO-AmPyraz@indium tin oxide (ITO) electrodes and with/without a coated Fe3O4 plate. The rGO-AmPyraz@3DNiF electrode showed the maximum production of these radicals at 2.2 mmol h-1 and 410 µmol h-1, respectively (pH 3) with the least leaching of Ni2+ such as < 0.5 mg L-1 even after 5 cycles (e.g., relative to 3DNiF (24 mg L-1). Such control on Ni ion leaching was effective all across the tested pH from 3 to 8.5. Its H2O2 generation capacity was far higher than that of the nanocarbon supported on commercially available ITO conductive glass. The mineralization of dichlorvos (at initial concentration: 50 mg L-1) was confirmed with its complete degradation as the concentrations of the end products (e.g., free Cl-1 (5.36 mg L-1) and phosphate (12.89 mg L-1)) were in good agreement with their stoichiometric concentration in dichlorvos. As such, the proposed system can be recommended as an effective electrode to replace nanocarbon-based product commonly employed for EF processes.

Valorization of swine manure biochar as a catalyst for transesterifying waste cooking oil into biodiesel.

As demand of proteins from meats has significantly increased with economy growth, the population of livestock proliferates. Thus, heavy amount of livestock byproducts released from livestock industries will become more problematic if they are handled in an unsatisfactory manner. In this study, swine manure (SM) waste was directly valorized to be used as a reaction catalyst for biodiesel production. Pyrolysis was adapted to produce swine manure biochars at 500 (SMB@500) and 650 °C (SMB@650), and the materials were used for conversion of waste cooking oil into biodiesels (i.e., fatty acid methyl esters: FAMEs). The properties of SMBs and resulting pyrolytic gases (i.e., H2, CO, and C1-2 hydrocarbons (HCs)) and liquids during pyrolysis were also characterized. SMBs used in this study included a large quantity of metallic contents that significantly contributed to the rapid reaction for biodiesel production. In detail, SMB@500 and SMB@650 showed higher than 96% of FAME yield at 305 and 210 °C of reaction temperature, while non-catalytic reaction using SiO2 showed similar FAME yield at 330 °C. Thus, this work offers a sustainable way to recycle organic and inorganic materials in livestock manures for energy (biodiesel, pyrolytic oil, H2, and C1-2 HCs) production.

Catalytic Pyrolysis of Polystyrene over Steel Slag under CO2 Environment.

As the consumption of plastic materials has been dramatically increased, the abundant presence of their debris has become a significant problem worldwide. Thus, this study proposes a sustainable plastic conversion platform for energy recovery. In detail, polystyrene pyrolysis was examined as a case study under CO2 atmosphere in reference to N2 condition. The major gaseous and liquid products from polystyrene pyrolysis include permanent gases (syngas and C1-2 hydrocarbons) and condensable aromatic compounds. Under CO2 environment, the reduction of polycyclic aromatic hydrocarbons (PAHs) was achieved during polystyrene pyrolysis, in comparison with N2 condition. Since its slow reaction kinetics, conversion of condensable hydrocarbons into permanent gases was not fully activated. Therefore, a cheap industrial waste, steel slag (SS), was employed as a catalyst to increase reaction kinetics. The synergistic effects of SS and CO2 contributed to doubling H2 production, while CO formation increased more than 300 times, in reference to non-catalytic pyrolysis. Because CO2 acted as an oxidant for CO production, control of H2/CO ratio was achieved in different conditions. Thus, the utilization of CO2 would suggest a promising way to reduce the formation of PAHs, adopting the reliable platform to produce syngas from plastic waste.

Emulsification characteristics of ether extracted pyrolysis-oil in diesel using various combinations of emulsifiers (Span 80, Atlox 4916 and Zephrym PD3315) in double reactor system.

Emulsification is a cost effective and simple method to use pyrolysis oil (or bio-oil) along with diesel as an emulsified fuel. Several combinations of emulsifiers, such as Span 80 and Atlox 4916, Span 80 and Zephrym PD3315, and Atlox 4916 and Zephrym PD3315, were tested to obtain stable emulsions. Two set of reactors (ultrasonicator and agitator-based mechanical reactor system) were used for the process. The ether-extracted pyrolysis oil (EEO), emulsifier, and diesel content of 10%-15%, 3%, and 82-87% were exposed to an ultrasonic power of 40% and with an agitation rate of 900 rpm. The emulsions obtained using Span 80 and Zephrym PD3315 showed stratification within 10 min. The emulsions for Span 80 and Atlox 4916 with a ratio of 3/15/82 for Emulsifer/EEO/Diesel, and for Atlox 4916 and Zephrym PD3315 emulsifiers with a ratio of 3/10/87 for Emulsifer/EEO/Diesel remained stable for more than 15 days. The functional groups analysis showed the stability of the emulsion for Span 80 and Atlox 4916, whereas a change in the absorbance intensity was observed when Atlox 4916 and Zephrym PD3315 were used, indicating stratification.

Use of steel slag as a catalyst in CO2-cofeeding pyrolysis of pine sawdust.

To seek an innovative way for simultaneous waste management and energy recovery, two waste materials (pine sawdust: PSD and steel slag: SS) were used in the pyrolysis process. PSD was used as a carbonaceous material for pyrolysis, and SS was used as a catalyst. Also, to achieve a more sustainable conversion system, a viable use of carbon dioxide (CO2) as a raw material in the non-catalytic/catalytic pyrolysis process was evaluated. Hence, the present study laid great stress on the CO2 effects. The present study pointed the optimistic technical features in line with the use of CO2 in the pyrolysis process. Exploiting CO2 in pyrolysis of PSD offered a strategic way to control carbon reallocation from liquid to gaseous pyrolysates by the gas phase reactions (GPRs). The reactions of CO2 and volatile pyrolysates led to CO enhancement, which was only observed at ≥ 600 °C due to the slow reaction kinetics of the GPRs of volatile pyrolysates and CO2. Such the slow reaction kinetics was expedited remarkably when SS was acted as a catalyst. Moreover, CO2 expedited thermal cracking of volatile pyrolysates including dehydrogenation, which led to the enhanced formation of CH4 and H2.

Sustainable production of alkyl esters via thermal process in the presence of carbon black.

In this study, it is introduced a sustainable synthetic route of alkyl esters, considered value-added industrial chemicals and fuels, from volatile fatty acids (VFAs) that can potentially be generated from organic waste. In the presence of a porous carbon material, the thermally induced reaction could be conducted under an initial pressure of 1 atm. Even though the reaction was finished within <10 s, they gave a high yield of target products: the conversion of six VFAs into their corresponding methyl esters which can be further converted into gasoline alternatives with >90 wt% yields. The carbon black showed better performance for both reactions than other commercially available porous material such as silica. This work suggests that carbon is a good option of being used as a porous material for thermal esterification to produce renewable alternative chemicals from waste-derived feedstocks.

Synthesis of nickel/biochar composite from pyrolysis of Microcystis aeruginosa and its practical use for syngas production.

This study proposes a sustainable waste-to-energy/biochar platform using a toxic microalgal biomass waste. In particular, CO2-feeding pyrolysis of Microcystis aeruginosa (M. aeruginosa) waste was investigated, focusing on the analysis of gaseous pyrolysates and properties of biochar with a construction of mass balance. Also, the catalytic capability of biochar produced from M. aeruginosa was explored to reinforce the mechanistic impact of CO2 on the pyrolysis process within the overall process level. Ni impregnated biochar composite was further synthesized and used as a catalyst to promote syngas formation in the CO2-feeding pyrolysis process of M. aeruginosa.

Catalytic pyrolysis of swine manure using CO2 and steel slag.

Pyrolysis of swine manure (SM) was conducted as a case study to establish an environmentally sound management of livestock manure. To build a more renewable pyrolysis platform for SM, this study selected carbon dioxide (CO2) as the reaction medium. In addition, CO2 was used in pyrolysis of SM to restrict the formation of toxic compounds, such as benzene derivatives and polycyclic aromatic hydrocarbons (PAHs). A series of thermo-gravimetric analysis (TGA) tests was done to understand the thermolysis of SM in the CO2 environment. The TGA tests elucidated no occurrence of heterogeneous reactions between the SM sample and the CO2. Moreover, the TGA tests of SM suggested that SM contains more volatile matter (VM) than lignocellulosic biomass. Non-catalytic transesterification of SM lipids confirmed that the dried SM sample contained 8.85 ±â€¯0.05 wt% of lipids. This study also confirmed that the mechanistic role of CO2 was realized through the gas phase reactions between volatile pyrolysates evolved from the thermolysis of SM and CO2. In summary, CO2 donates O, enhancing the generation of CO through homogeneous reactions. In parallel, this study confirmed that CO2 suppress dehydrogenation. Therefore, the identified gas phase reactions between volatile pyrolysates and CO2 led to the compositional modifications in the condensable pyrolysates. However, such mechanistic features arising from CO2 only initiated at ≥520 °C. To expedite the reaction kinetics of the homogeneous reaction triggered by CO2, steel slag (SS) was used as a catalyst. Hence, the reaction kinetics associated with the mechanistic role of CO2 were substantially enhanced (up to 80%) when SS was used as a catalyst. Therefore, all experimental findings strongly suggest that CO2 can be utilized as a raw material in a thermo-chemical process. More importantly, all observations suggest that CO2 lopping can also be achieved in a thermo-chemical process. Lastly, this study shows that the high Cu content in SM was effectively immobilized through pyrolysis. Conclusively, this study experimentally proved that CO2 could be promising for restricting the formation of toxic pollutant in the thermo-chemical treatment in that CO2 offers an innovative and strategic means for controlling the ratio of C to H. Note that aromaticity and toxicity of chemical compounds are highly contingent on the ratio of C to H.

Photo-induced redox coupling of dissolved organic matter and iron in biochars and soil system: Enhanced mobility of arsenic.

Dissolved organic matter (DOM) elucidated from biochars enhances the dissolution of iron oxides and reduction of iron. However, given that reduction mechanism of iron (Fe(III)) in the practical biochar applications for soil amendment and environmental remediation have not been fully elucidated, this study laid great emphasis on the photo-induced Fe(II) liberated from DOM-Fe(III) complexes. Thus, pyrolysis of biomass was carried out at 300 °C to maximize DOM release from biochars. Moreover, three different biomass samples (rice straw (R), granular sludge (G) from an anaerobic digester, and spent coffee grounds (C)) were chosen as carbon substrates for biochars preparation. To demonstrate the transformation of Fe(III), 1 and 5 wt% biochar was applied to the clean (S1) and arsenic-contaminated (S2) soil with/without the light. The results indicate that the light condition produces more Fe(II). The amount of Fe(II) accounts for 25.3, 28.6, and 30.7% of total iron under the light with 5 wt% GB, RB, and CB in S1, and 10.6, 13.1, and 13.8% in S2. This study demonstrates that Fe(II) is generated more under ultraviolet irradiation than visible light and dark condition. In addition, a control experiment without biochar showed that DOM plays an important role in the reduction of Fe(III). The mobility of arsenic increased under the light condition since the intermediates of DOM photo-degradation accelerates the dissolution of iron oxides and arsenic competes with DOM for the adsorption. Therefore, there was no significant correlation between the elution of arsenic and the formation of Fe(II) during the reductive dissolution of iron oxide under the light condition.

Adsorption properties of advanced functional materials against gaseous formaldehyde.

Intense efforts have been made to eliminate toxic volatile organic compounds (VOCs) in indoor environments, especially formaldehyde (FA). In this study, the removal performances of gaseous FA using two metal-organic frameworks, MOF-5 and UiO-66-NH2, and two covalent-organic polymers, CBAP-1 (EDA) and CBAP-1 (DETA), along with activated carbon as a conventional reference material, were evaluated. To assess the removal capacity of FA under near-ambient conditions, a series of adsorption experiments were conducted at its concentrations/partial pressures of both low (0.1-0.5 ppm/0.01-0.05 Pa) and high ranges (5-25 ppm/0.5-2.5 Pa). Among all tested materials at the high-pressure region ㅐ (e.g., at 2.5 ppm FA), a maximum adsorption capacity of 69.7 mg g-1 was recorded by UiO-66-NH2. Moreover, UiO-66-NH2 also displayed the best 10% breakthrough volume (BTV10) of 534 L g-1 (0.5 ppm FA) to 2963 L g-1 (0.1 ppm FA). In contrast, at the high concentration test (at 5, 10, and 25 ppm FA), the maximum BTV10 values were observed as: 137 (UiO-66-NH2), 144 (CBAP-1 (DETA)), and 36.8 L g-1 (CBAP-1 (EDA)), respectively. The Langmuir isotherm model was observed to be a better fit of the adsorption data than the Freundlich model under most of the tested conditions. The superiority of UiO-66-NH2 was attributed to the van der Waals interactions between the linkers (framework) and the hydrocarbon "tail" (FA) coupled with interactions between its open metal sites and the FA carbonyl groups. This study demonstrated the good potential of these advanced functional materials toward the practical removal of gaseous FA in indoor environments.

Valorization of alum sludge via a pyrolysis platform using CO2 as reactive gas medium.

In an effort to seek a new technical platform for disposal of drinking water treatment sludge (DWTS: alum sludge), pyrolysis of DWTS was mainly investigated in this study. To establish a more sustainable thermolytic platform for DWTS, this study particularly employed CO2 as reactive gas medium. Thus, this study laid great emphasis on elucidating the mechanistic roles of CO2 during the thermolysis of DWTS. A series of the TGA tests of DWTS in CO2 in reference to N2 revealed no occurrence of the heterogeneous reaction between CO2 and the sample surface of DWTS. As such, at the temperature regime before initiating the Boudouard reaction (i.e., ≥700 °C), the mass decay patterns of DWTS in N2 and CO2 were nearly identical. However, the gaseous effluents from lab-scale pyrolysis of DWTS in CO2 in reference to N2 were different. In sum, the homogeneous reactions between CO2 and volatile matters (VMs) evolved from the thermolysis of DWTS led to the enhanced generation of CO. Also, CO2 suppressed dehydrogenation of VMs. Such the genuine mechanistic roles of CO2 in the thermolysis of DWTS subsequently led to the compositional modifications of the chemical species in pyrolytic oil. Furthermore, the biochar composite was obtained as byproduct of pyrolysis of DWTS. Considering that the high content of Al2O3 and Fe-species in the biochar composite imparts a strong affinity for As(V), the practical use of the biochar composite as a sorptive material for arsenic (V) was evaluated at the fundamental levels. This work reported that adsorption of As(V) onto the biochar composite followed the pseudo-second order model and the Freundlich isotherm model.

Consecutive reduction of Cr(VI) by Fe(II) formed through photo-reaction of iron-dissolved organic matter originated from biochar.

Employing biochar for environmental remediation has been widely practiced. Nonetheless, the reduction mechanisms of hexavalent chromium (Cr(VI)) in the presence of biochar have not been fully elucidated (i.e., direct or indirect reduction of Cr(VI) by biochar). In particular, the effect of light on Cr(VI) reduction by biochar was rarely reported. Thus, to clarify the reduction mechanisms of Cr(VI) by biochar at the fundamental level, this study laid great emphasis on the photo-induced reduction of Cr(VI) in the application of biochar. Biochar releases dissolved organic matter (DOM), the DOM can extract Fe(III) from soil by complexation, and the complexes can be photo-reacted under the light. In these respects, Fe(II) formed by the photo-induced reaction of DOM-Fe(III) was particularly evaluated in this study. To evaluate that, three biomass samples (rice straw, granular sludge from an up-flow anaerobic sludge blanket, and spent coffee ground) were torrefied to biochar. To circumvent the adsorption of Cr(VI) onto biochar, biochar extractives (served as a source for DOM) and Fe(III) solution were tested with/without UV light to prove Fe(II) formation. This study experimentally proved that the more Fe(II) under the UV radiation was formed in the co-existence with biochar extractives and Fe(III). All experimental data from three biochar samples were indeed very similar. Cr(VI) reduction by Fe(II) from GB, RB, and CB reached up to 96, 79, and 100%, respectively. The different reduction efficiency signified that the low molecular weight of organic acids, such as oxalate, were more sensitive to the UV light, thereby resulting in the enhanced Fe(II) formation. Such Fe(II) formation subsequently led to the high reduction efficiency of Cr(VI).

Production of bio-oil from fast pyrolysis of biomass using a pilot-scale circulating fluidized bed reactor and its characterization.

To circumvent the adverse impacts arising from an excessive use of fossil fuels, bioenergy and chemical production from a carbon neutral resource (biomass) has drawn considerable attention over the last two decades. Among various technical candidates, fast pyrolysis of biomass has been considered as one of the viable technical routes for converting a carbonaceous material (biomass) into biocrude (bio-oil). In these respects, three biomass samples (i.e., sawdust, empty fruit bunch, and giant Miscanthus) were chosen as a carbon substrate for the pyrolysis process in this study. A pilot-scale circulating fluidized bed reactor was employed for the pyrolysis work, and biocrude from the fast pyrolysis process at 500 °C were characterized because the maximum yield of biocrude (60 wt% of the original sample mass) was achieved at 500 °C. The physico-chemical properties of biocrude were measured by the international standard/protocol (ASTM D7544 and/or EN 16900 test method) to harness biocrude as bioenergy and an initial feedstock for diverse chemicals. All measurements in this study demonstrated that the heating value, moisture content, and ash contents in biocrude were highly contingent on the type of biomass. Moreover, characterization of biocrude in this study significantly suggested that additional unit operations for char and metal removal must be conducted to meet the fuel standard in terms of biocrude as bioenergy.