Publications by authors named "Yongtae Ahn"

In this study, we investigated the efficiency of a bentonite/iron-coated sand (B/ICS) stabilizer in reducing the mobility and accumulation of heavy metals (Pb, Cd, Zn, and As) in contaminated sediments. Bentonite is effective in the adsorption of heavy metals, while ICS is effective in the adsorption of As. When combined, the stabilizer can be applied to mixed-contaminated sediments containing both heavy metals and As.

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The performance and stability of a bioelectrochemical anaerobic digester (BeAD), continuously augmented with electroactive microorganisms (EAMs), were investigated. The BeAD showcased superior performance, sustaining the high COD removal efficiency and methane production rate of 76.5 % and 0.

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  • This study examined how manganese (Mn(II)) and arsenite (As(III)) coexist and are contaminated in groundwater, focusing on their oxidation with varying pH, bicarbonate (HCO), and sodium hypochlorite (NaClO) levels.
  • Results indicated that with a NaClO:As(III) ratio greater than 1, As(III) could be oxidized quickly (99.7% efficiency), while the oxidation rates of Mn(II) were influenced by pH and bicarbonate presence.
  • The research utilized an artificial neural network (ANN) to analyze data, showing high predictive accuracy for Mn(II) oxidation rates based on pH and NaClO concentrations, with R values of
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This study focused on evaluating the effectiveness of stabilizer/binding agents in immobilizing arsenic (As) in contaminated soil using both geochemical and geophysical monitoring methods. The effluent from the stabilizer/binding agent's application and control columns was analyzed, and the status of the columns was monitored using electrical resistivity (ER) and induced polarization (IP) methods. As stabilizers/binder, acid mine drainage sludge (AMDS) and steel slag (SS) were used, which delayed As and Ca leaching time and significantly reduced As leaching amount.

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This study focuses on the bioremediation of nitrate-contaminated groundwater, which has become a significant environmental problem due to the increasing usage of fertilizers and sewage disposal. The nitrate reduction efficiencies of biological denitrification by injection of carbon source in a pilot-scale treatment system setup were investigated at a groundwater contamination site. The field test was conducted using acetate as a carbon source for 22 days to assess the nitrate reduction efficiencies of in-situ treatment.

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  • Azoreductase is an enzyme that breaks down toxic textile azo dyes, which are harmful pollutants in water.
  • The study involved inserting the azoreductase gene from Klebsiella pneumoniae into E. coli, resulting in effective degradation of specific dyes (Remazol Red-R and Acid-Blue 29).
  • Results showed that the crude and purified enzymes significantly reduced dye color within half an hour, confirming the enzyme's potential in bioremediation.
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Nanomaterials have attracted more curiosity recently because of their wide-ranging application in environmental remediation and electronic devices. The current study focuses on zinc oxide nanoparticles' (ZnO NPs) simple production, characterization, and applications in several fields, including medicinal and photocatalytic degradation of dyes. The non-aqueous-based reflux method is helpful for ZnO NP synthesis; the procedure involves refluxing zinc acetate dihydrate precursor in ethylene glycol for 3 hours in the absence of sodium acetate, in which the refluxing rate and the cooling rate are optimized to get the desired phase, and the unique morphology of polyol-mediated ZnO NPs; it has been achieved using the capping agent TBAB (tetra-butyl ammonium bromide) and precursor zinc acetate dihydrate.

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  • - The study evaluated the toxic effects of five bisphenols (BPs) on the freshwater microalga Chlamydomonas mexicana, revealing that BPAF, BPB, and BPZ are more toxic than BPS and BPF.
  • - C. mexicana effectively removed a high percentage of BPs after 14 days, demonstrating its potential for bioremediation, with recorded removal rates of 61% to 99% for different bisphenols.
  • - The biotransformed products of the BPs were found to be less toxic than the original compounds, and the biomass generated could potentially be used as a biodiesel feedstock based on its fatty acid composition.
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Fluoride, a naturally occurring chemical element, is largely insoluble in soils. More than 90% of the fluoride in soil is bound to soil particles and is unable to be dissolved. As part of the soil, fluoride is predominantly located in the colloid or clay fraction of the soil, and the movement of fluoride is strongly affected by the sorption capacity of the soil, which is affected by pH, the type of soil sorbent present, and the salinity.

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Ex situ mineralization of CO is a promising technology that employs Ca- and Mg-rich industrial wastes but it simultaneously produces end products. Although Mg is a major mineralization source, it can adversely impact carbonate precipitation and crystal stability during co-precipitation in combination with Ca. In this study, the effects of Mg ions on the mineralization process and its products were investigated using precipitates formed at different aqueous concentrations of Mg.

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In this work, the effectiveness of pyrite/sodium hypochlorite (FeS/NaClO) treatment to eliminate arsenic (As) from fractured-bedrock groundwater via oxidative adsorption was evaluated. The As concentration in the tested reactors decreased sharply during the initial 5 min, as the addition of NaClO effectively increased the As removal efficiency, attaining 98.6% removal within 60 min in the presence of 0.

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The production of biohythane, a combination of energy-dense hydrogen and methane, from the anaerobic digestion of low-cost organic wastes has attracted attention as a potential candidate for the transition to a sustainable circular economy. Substantial research has been initiated to upscale the process engineering to establish a hythane-based economy by addressing major challenges associated with the process and product upgrading. This review provides an overview of the feasibility of biohythane production in various anaerobic digestion systems (single-stage, dual-stage) and possible technologies to upgrade biohythane to hydrogen-enriched renewable natural gas.

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Synthesis of metalloid nanoparticles using biological-based fabrication has become an efficient alternative surpassing the existing physical and chemical approaches because there is a need for developing safer, more reliable, cleaner, and more eco-friendly methods for their preparation. Over the last few years, the biosynthesis of metalloid nanoparticles using biological materials has received increased attention due to its pharmaceutical, biomedical, and environmental applications. Biosynthesis using bacterial, fungal, and plant agents has appeared as a faster developing domain in bio-based nanotechnology globally along with other biological entities, thus posing as an option for conventional physical as well as chemical methods.

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The present study aims at understanding the effects of fuel preheating on engine characteristics of waste animal fat-oil (WAF-O) biodiesel in a single-cylinder CI engine, with the preheating technique proposed as an effective means for enhancing the fuel properties. To understand the effects of the preheated fuel, the WAF-O biodiesel was preheated at 60, 80, 100 and 120 °C and tested along with neat diesel and unheated WAF-O biodiesel. For this purpose, biodiesel was produced from different animal wastes by means of KOH-assisted ethanol-based transesterification, reporting its maximum yield as 96.

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SARS-CoV-2 is the causative agent of the COVID-19 pandemic. This in silico study aimed to elucidate therapeutic efficacies against SARS-CoV-2 of phyco-compounds from the seaweed, . Twelve phyco-compounds were isolated and toxicity was analyzed by VEGA QSAR.

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Nanoparticles are inevitable byproducts of modern industry. However, the environmental impacts arising from industrial applications of nanoparticles are largely under-reported. This study evaluated the ecotoxicological effects of aluminum oxide nanoparticles (AlONP) and its influence on sulfacetamide (SA) biodegradation by a freshwater microalga, Scenedesmus obliquus.

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This review presented the unique characteristics of different types of cyclodextrin polymers by non-covalent host-guest interactions to synthesize an inclusion complex. Various cancers are treated with different types of modified cyclodextrins, along with the anticancer drug paclitaxel. PTX acts as a mitotic inhibitor, but due to its low dissolution and permeability in aqueous solutions, it causes considerable challenges for drug delivery system (DDS) designs.

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An inadequate lignocellulolytic capacity of a conventional anaerobic digester sludge (ADS) microbiota is the bottleneck for the maximal utilization of lignocellulose in anaerobic digestion. A well-constructed microbial consortium acclimatized to lignocellulose outperformed the ADS in terms of biogas productivity when fractionated biocomponents of rice straw were used to achieve a high methane bioconversion rate. A 33.

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The effective fractionation of structural components of abundantly available lignocellulosic biomass is essential to unlock its full biorefinery potential. In this study, the feasibility of humic acid on the pretreatment of Kentucky bluegrass biomass in alkaline condition was assessed to separate 70.1% lignin and hydrolyzable biocomponents.

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Accidental chemical leaks and illegal chemical discharges are a global environmental issue. In 2012, a hydrogen fluoride leak in Gumi, South Korea, killed several people and contaminated the environment. This leak also led to a significant decline in crop yield, even after the soil concentration of hydrogen fluoride decreased to below the standard level following natural attenuation.

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Bacterial strains resistant to antimicrobial treatments, such as antibiotics, have emerged as serious clinical problems, necessitating the development of novel bactericidal materials. Nanostructures with particle sizes ranging from 1 to 100 nanometers have appeared recently as novel antibacterial agents, which are also known as "nanoantibiotics". Nanomaterials have been shown to exert greater antibacterial effects on Gram-positive and Gram-negative bacteria across several studies.

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The adaptability and biofuel production potential of two strains of microalgae isolated and cultivated in livestock wastewater effluent (LWE) with acid mine drainage (AMD) were investigated. The isolated strains of microalgae from samples obtained from LWE and AMD, two microalgal strains (Nephroselmis sp. KGE2 and Autodesmus obliquus KGE17) were selected based on their growth rate and lipid productivity.

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Bioaugmenting lignocellulose digestion with potent lignocellulolytic microbiomes (LMs) facilitates efficient biomethanation. Assessing the metabolic roles of microbial communities of the LMs and their complex interactions with the indigenous anaerobic digester microbiome is pivotal in implementing bioaugmentation. Multiple meta-omics are the frontline approaches to investigating gene functions, metabolic roles, and the ecological niches of LMs.

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A novel metal-biochar (Biochar/AMDS) composite were fabricated by co-pyrolysis of spent coffee waste (SCW)/acid mine drainage sludge (AMDS), and their effective application in adsorptive removal of air pollutants such as formaldehyde in indoor environments was evaluated. The physicochemical characteristics of Biochar/AMDS were analyzed using SEM/EDS, XRF, XRD, BET, and FTIR. The characterization results illustrated that Biochar/AMDS had the highly porous structure, carbonaceous layers, and heterogeneous Fe phases (hematite, metallic Fe, and magnetite).

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Article Synopsis
  • The study focuses on improving the commercial viability of producing biofuels from concentrated microalgal strains, addressing energy consumption as a major challenge.
  • It demonstrates a novel energy-saving microwave pretreatment technique that requires only 4.2 MJ/kg to efficiently convert high concentrations (100 g/L) of biomass from Chlamydomonas species into bioethanol, higher-alcohols, and biodiesel.
  • The results show a total conversion efficiency of 67% and high biomass utilization rates, ultimately enhancing biofuel yield while minimizing waste through integrated pretreatment processes.
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