[1] Author: Kwangsuk Yoon, Gihoon Kwon, Eunji Kim, Jörg Rinklebe, Hocheol Song[2] Journal: Chemical Engineering Journal (IF=16.74)[3] DOI: https://doi.org/10.1016/j.cej.2024.149470[4] AbstractThis study aimed to fabricate zero-valent iron (Fe0)-loaded biochar from an industrial waste and further demonstrate its applicability as an environmental medium to remove Se(VI) and Se(IV). The biochar (PS/BC-750) was produced via the pyrolysis of paper-mill sludge under N2 atmosphere. The characterization revealed that PS/BC-750 has a porous carbon structure embedded with reduced Fe phases (Fe0 and FeO). The adsorptive removal of Se(VI) and Se(IV) by PS/BC-750 was highly dependent on pH condition and progressively decreased with the pH increase. The adsorption kinetics of Se(VI) and Se(IV) reached equilibrium within 1440 and 60 min, respectively, following a pseudo-second-order kinetics. Se(VI) and Se(IV) adsorption isotherms fit to the Freundlich and Langmuir models, respectively, highlighting the importance of chemisorption in the adsorption processes. X-ray photoelectron spectroscopy and competing anions experiments revealed that Se(VI) was adsorbed mainly on the Fe phases while Se(IV) was adsorbed on both Fe phases and carbon surface by specific binding mechanisms, with those adsorbed on Fe phases being subsequently reduced to Se0. The results demonstrated that the pyrolytic process can be of a viable platform for converting Fe-containing waste materials into environmental media with a wide application potential. 

[1] Author: Qiaozhi Zhang, Yang Cao, Mingjing He, Hanwu Lei, Hocheol Song, Daniel S. Alessi, Daniel C.W. Tsang[2] Journal: Bioresource Technology (IF=11.88)[3] DOI: https://doi.org/10.1016/j.biortech.2023.130211[4] AbstractThis study investigated the feasibility of a high-loading process with less water consumption for the valorization of wet biomass waste through hydrothermal carbonization (HTC) with and without N2 pressurization from the views of water saving, carbon utilization, and energy recovery. The results revealed that reducing the liquid-to-solid ratio from 10 to 2.5 significantly improved carbon storage in hydrochar due to preferential carbon sequestration as the solid phase (59.9%) instead of being lost in the liquid phase (∼10%). The pressurized HTC process resulted in a higher stability hydrocharthrough the devolatilization of secondary char that was less stable, yet resulted in ∼10% 15% more carbon transformation to the gas phase. A cost-benefit analysis further demonstrated the potential of the high-loading HTC process for enhancing energy recovery while minimizing energy consumption during hydrochar production from high-moisture yard waste. 

[1] Author: Kyung Min Lee, Byeongseok Kim, Juwon Lee, Gihan Kwon, Kwangsuk Yoon, Hocheol Song, Kyung Hoon Min, Sang Eun Shim, Sungwon Hwang and Taejin Kim[2] Journal: Catalysis Science and Technology (IF=6.17)[3] DOI: https://doi.org/10.1039/d3cy01103h[4] AbstractNiOx/CeO2 catalysts have shown promising results in various catalytic reactions, including the NO reduction by CO. In this study, we investigated the effect of oxidation and reduction treatments on the NO reduction by CO over pretreated NiOx/CeO2 catalysts. A series of oxidized and reduced supported NiOx catalysts were synthesized in two steps: (1) the pretreatment of CeO2 supports at different temperatures (400, 500, and 700 °C) under oxidizing and reducing conditions and (2) the synthesis of NiOx/CeO2 catalysts by an incipient wetness impregnation method (IWI) with a fixed surface density of 5.3 Ni per nm2 under specific conditions (oxidation/reduction) applied during the CeO2 treatment. The prepared catalysts were characterized via BET, ICP/OES, Raman, XPS, and XRD to understand their physicochemical properties. The results showed that as the pretreatment temperature increased, the physicochemical properties of NiOx/CeO2 catalysts were changed: a decreased specific surface area (SSA), decreased oxygen vacancy/defect sites, and an increased crystallite size. The oxidized NiOx/CeO2 catalyst at a lower pretreatment temperature displayed a better catalytic activity, indicating that the physicochemical properties of the catalysts were key factors in enhancing the catalytic activity. To understand the intermediate species and reaction mechanism during the NO reduction by CO, an in situ DRIFTS study was performed and a possible reaction mechanism was also discussed. 

[1] Author: Hanbo Chen, Yurong Gao, Huiyun Dong, Binoy Sarkar, Hocheol Song, Jianhong Li, Nanthi Bolan, Bert F. Quin, Xing Yang, Fangbai Li, Fengchang Wu, Jun Meng, Hailong Wang, Wenfu Chen[2] Journal: Environment International (IF=13.35)[3] DOI: https://doi.org/10.1016/j.envint.2023.107989[4] AbstractSustainable management of ever-increasing organic biowaste and arable soil contamination by potentially toxic elements are of concern from both environmental and agricultural perspectives. To tackle the waste issue of crawfish shells and simultaneously minimize the threat of arsenic (As) and lead (Pb) to human health, a pot trial was conducted using chitin (CT), crawfish shell biochar (CSB), crawfish shell powder (CSP), and CT–CSB composite to compare their remediation efficiencies in As/Pb co-contaminated soil. Results demonstrated that addition of all amendments decreased Pb bioavailability, with the greatest effect observed for the CT–CSB treatment. Application of CSP and CSB increased the soil available As concentration, while significant decreases were observed in the CT and CT–CSB treatments. Meanwhile, CT addition was the most effective in enhancing the soil enzyme activities including acid phosphatase, α-glucosidase, N-acetyl-β-glucosaminidase, and cellobiohydrolase, whereas CSB-containing treatments suppressed the activities of most enzymes. The amendments altered the bacterial abundance and composition in soil. For instance, compared to the control, all treatments increased Chitinophagaceae abundance by 2.6–4.7%. The relative abundance of Comamonadaceae decreased by 1.6% in the CSB treatment, while 2.1% increase of Comamonadaceae was noted in the CT–CSB treatment. Redundancy and correlation analyses (at the family level) indicated that the changes in bacterial community structure were linked to bulk density, water content, and As/Pb availability of soils. Partial least squares path modeling further indicated that soil chemical property (i.e., pH, dissolved organic carbon, and cation exchange capacity) was the strongest predictor of As/Pb availability in soils following amendment application. Overall, CT–CSB could be a potentially effective amendment for simultaneously immobilizing As and Pb and restoring soil ecological functions in contaminated arable soils. 

[1] Author: Hyeonjung Yu, Jeong-Yun Jang, In-Hyun Nam, Hwanju Jo, Gil-Jae Yim, Hocheol Song, Dong-Wan Cho[2] Journal: Bioresource Technology (IF=11.88)[3] DOI: https://doi.org/10.1016/j.biortech.2023.129705[4] AbstractWith rising of harmful algae blooming and toxin exposure, practical utilization of harmful algae has been developed. This work aimed to magnetically harvest Microcystis aeruginosa (MA) using iron oxides and investigate the feasibility of algae/iron oxides mixture as feedstock in pyrolytic platform to produce syngas and metal biochar. Carbon dioxide (CO2) was used as a feeding gas to enhance the production efficiency of syngas and also functioned pH controller for better MA harvesting and toxin removal. CO2support brought multiple benefits: magnetite (Fe3O4) and maghemite (γ-Fe2O3) recovered MA in a relatively short period of time (∼1 min), the recovered biomass generated 34-fold increased carbon monoxide, and metal biochar adsorbed higher amount of toxin from MA (2.8-fold). Pyrolytic utilization of harmful algae supported by CO2 and iron oxides could be one of promising techniques for evolution of metal biochar to remove toxin, while efficiently recover biomass and enhance syngas production. 

[1] Author: Rebecca J. Wicker, Ehsan Daneshvar, Ashok Kumar Gupta, Hocheol Song, Eakalak Khan, Amit Bhatnagar[2] Journal: Chemical Engineering Journal (IF=16.74)[3] DOI: https://doi.org/10.1016/j.cej.2023.144585[4] AbstractMixed-species photosynthetic consortia have several advantages over conventional microalgal monocultures, including better carbon capture, more efficient wastewater treatment, and resilience to environmental stressors. In this study, a constructed photosynthetic consortium was investigated using a hybrid cultivation approach (combined planktonic and biofilm growth) in a pilot-scale raceway pond. A blend of locally-sourced waste streams was used as growth medium; biogas digestate and aquaculture effluent. The consortium performed well in terms of carbon capture, with 80.1% and 78.6% removal of inorganic and organic carbon species, respectively, over a 42-day cultivation period. Removal of phosphate and nitrogen species was suboptimal; 46.8% of phosphate had been consumed by the end of cultivation, but just 27.9% of total nitrogen had been removed. Despite inefficient total nitrogen removal, nitrite and ammonia were almost completely depleted after 15 days. Light microscopy was employed to monitor biofilm formation and changes in biodiversity over time, which helped to elucidate the processes responsible for nutrient and carbon flux, as well as biofilm formation and interspecies associations. Understanding how different mechanisms and biological functions can be encouraged or inhibited in mixed-species consortia is imperative for tailoring consortia to industrially-relevant applications, such as carbon capture, nutrient removal, or production of biomass or specific metabolites. The present study demonstrates not only the importance of cultivating dynamic, biodiverse, and adaptable consortia instead of fragile monocultures, but also the utility in real-time monitoring of such systems, so that environmental parameters can be adjusted for optimal performance. 

[1] Author: Kwangsuk Yoon, Dong-Wan Cho, Gihoon Kwon, Jörg Rinklebe, Hailong Wang, Hocheol Song[2] Journal: Chemosphere (IF=8.94)[3] DOI: https://doi.org/10.1016/j.chemosphere.2023.138665[4] AbstractOne of the main challenges of biochar application for environmental cleanup is rise of pH in water or soil due to high ash and alkali metal contents in the biochar. While this intrinsic property of biochar is advantageous in alleviating soil and water acidity, it severely impairs the affinity of biochar toward anionic contaminants such as arsenic. This study explored a technical approach that can reduce the basicity of lignin-based biochar by utilizing FeCl3 during production of biochar. Three types of biochar were produced by co-pyrolyzing feedstock composed of different combinations of lignin, red mud (RM), and FeCl3, and the produced biochar samples were applied to adsorption of As(V). The biochar samples commonly possessed porous carbon structure embedded with magnetite (Fe3O4) particles. The addition of FeCl3 in the pyrolysis feedstock had a notable effect on reducing basicity of the biochar to yield significantly lower solution pH values than the biochar produced without FeCl3 addition. The extent of As(V) removal was also closely related to the final solution pH and the greatest As(V) removal (>77.6%) was observed for the biochar produced from co-pyrolysis of lignin, RM, and FeCl3. The results of adsorption kinetics and isotherm experiments, along with x-ray spectroscopy (XPS), strongly suggested adsorption of As(V) occurred via specific chemical reaction (chemisorption) between As(V) and Fe–O functional groups on magnetite. Thus, the overall results suggest the use of FeCl3 is a feasible practical approach to control the intrinsic pH of biochar and impart additional functionality that enables effective treatment of As(V). 

[1] Author: Gihoon Kwon, Dong-Wan Cho, Juyeong Park, Amit Bhatnagar, Hocheol Song[2] Journal: Chemical Engineering Journal (IF=16.74)[3] DOI: https://doi.org/10.1016/j.cej.2023.142771[4] AbstractThe rapid expansion of plastic manufacturing industries in last several decades has brought serious concerns over the environmental impacts of plastic wastes. Recent outbreak of Covid-19 drastically increased production, use, and disposal of plastic products. Current management strategies for wasted plastics still rely on landfill and incineration that continue to exacerbate plastic pollution and carbon emissions. Many countries have put forward multifaceted administrative efforts to reduce plastic wastes, but the annual global generation of plastic wastes is still increasing. In techno-society, researchers have been exploring more effective plastic wastes treatment technologies to alleviate environmental impacts of plastic wastes. Such efforts entailed several technical options that can potentially contribute to establishing a circular economy for plastics. Thermochemical process is a prominent example of such techniques. This review presents an overview of the issue of plastic pollution, covering topics including global plastic production, environmental impacts, and toxicity. In addition, the global administrative efforts aimed at reducing plastic pollution are discussed, as well as detection and treatment strategies to establish a circular economy in plastic management. 

[1] Author: Shiv Bolan, Lokesh P. Padhye, Manish Kumar, Vasileios Antoniadis, Srinidhi Sridharan, Yuanyuan Tang, Narendra Singh, Choolaka Hewawasam, Meththika Vithanage, Lal Singh, Jörg Rinklebe, Hocheol Song, Kadambot H.M. Siddique, M.B. Kirkham, Hailong Wang, Nanthi Bolan[2] Journal: Environmental Pollution (IF=9.98)[3] DOI: https://doi.org/10.1016/j.envpol.2023.121080[4] AbstractMedical wastes include all solid and liquid wastes that are produced during the treatment, diagnosis, and immunisation of animals and humans. A significant proportion of medical waste is infectious, hazardous, radioactive, and contains potentially toxic elements (PTEs) (i.e., heavy metal (loids)). PTEs, including arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg), are mostly present in plastic, syringes, rubber, adhesive plaster, battery wastes of medical facilities in elemental form, as well as oxides, chlorides, and sulfates. Incineration and sterilisation are the most common technologies adopted for the safe management and disposal of medical wastes, which are primarily aimed at eliminating deadly pathogens. The ash materials derived from the incineration of hazardous medical wastes are generally disposed of in landfills after the solidification/stabilisation (S/S) process. In contrast, the ash materials derived from nonhazardous wastes are applied to the soil as a source of nutrients and soil amendment. The release of PTEs from medical waste ash material from landfill sites and soil application can result in ecotoxicity. The present study is a review paper that aims to critically review the dynamisms of PTEs in various environmental media after medical waste disposal, the environmental and health implications of their poor management, and the common misconceptions regarding medical waste. 

[1] Author: Dong-Wan Cho, Chul-Min Chon, Gil-Jae Yim, Jungho Ryu, Hwanju Jo, Sun-Joon Kim, Jeong-Yun Jang, Hocheol Song[2] Journal: Chemosphere (IF=8.94)[3] DOI: https://doi.org/10.1016/j.chemosphere.2022.136536[4] AbstractNano Fe(III) oxide (FO) was used as an amendment material in CO2-assisted pyrolysis of spent coffee grounds (SCG) and its impacts on the syngas (H2 & CO) generation and biochar adsorptive properties were investigated. Amendment of FO led to 153 and 682% increase of H2 and CO in pyrolytic process of SCG, respectively, which is deemed to arise from enhanced thermal cracking of hydrocarbons and oxygen transfer reaction mediated by FO. Incorporation of FO successfully created porous structure in the produced biochar. The adsorption tests revealed that the biochar exhibited bi-functional capability to remove both positively charged Cd(II) and Ni(II), and negatively charged Sb(V). The adsorption of Cd(II) and Ni(II) was hardly deteriorated in the multiple adsorption cycles, and the adsorption of Sb(V) was further enhanced through formation of surface ternary complexes. The overall results demonstrated nano Fe(III) oxide is a promising amendment material in CO2-assisted pyrolysis of lignocellulosic biomass for enhancing syngas generation and producing functional biochar.