Jiseon Jang

Enhanced adsorption of cesium on PVA-alginate encapsulated Prussian blue-graphene oxide hydrogel beads in a fixed-bed column system

A continuous fixed-bed column study was performed using PVA-alginate encapsulated Prussian blue-graphene oxide (PB-GO) hydrogel beads as a novel adsorbent for the removal of cesium from aqueous solutions. The effects of different operating parameters, such as initial cesium concentration, pH, bed height, flow rate, and bead size, were investigated. The maximum adsorption capacity of the PB-GO hydrogel beads was 164.5mg/g at an initial cesium concentration of 5mM, bed height of 20cm, and flow rate of 0.83mL/min at pH 7. The Thomas, Adams-Bohart, and Yoon-Nelson models were applied to the experimental data to predict the breakthrough curves using non-linear regression. Although both the Thomas and Yoon-Nelson models showed good agreement with the experimental data, the Yoon-Nelson model was found to provide the best representation for cesium adsorption on the adsorbent, based on the χ(2) analysis.

Facile synthesis of pectin-stabilized magnetic graphene oxide Prussian blue nanocomposites for selective cesium removal from aqueous solution.

This work focused on the development of pectin-stabilized magnetic graphene oxide Prussian blue (PSMGPB) nanocomposites for removal of cesium from wastewater. The PSMGPB nanocomposite showed an improved adsorption capacity of 1.609mmol/g for cesium, compared with magnetic graphene oxide Prussian blue, magnetic pectin Prussian blue, and magnetic Prussian blue nanocomposites, which exhibited adsorption capacities of 1.230, 0.901, and 0.330mmol/g, respectively. Increased adsorption capacity of PSMGPB nanocomposites was attributed to the pectin-stabilized separation of graphene oxide sheets and enhanced distribution of magnetites on the graphene oxide surface. Scanning electron microscopy images showed the effective separation of graphene oxide sheets due to the incorporation of pectin. The optimum temperature and pH for adsorption were 30°C and 7.0, respectively. A thermodynamic study indicated the spontaneous and the exothermic nature of cesium adsorption. Based on non-linear regression, the Langmuir isotherm fitted the experimental data better than the Freundlich and Tempkin models.

Conversion of orange peel waste biomass to bioelectricity using a mediator-less microbial fuel cell.

Microorganisms have the potential to become a game-changer in sustainable energy production in the coming generations. Microbial fuel cells (MFCs) as an alternative renewable technology can capture bioenergy (electricity) from carbon-based sources by utilizing microorganisms as biocatalysts. This study demonstrated that MFC technology can be explored for bioelectricity production from orange peel waste (OPW), an agricultural byproduct and an organic substrate, without any chemical pretreatment or the addition of extra mediators. A maximum voltage generation of 0.59 ± 0.02 V (at 500 Ω) was achieved in a dual chamber MFC during stable voltage generation stages. The maximum power density and current density obtained were 358.8 ± 15.6 mW/m(2) and 847 ± 18.4 mA/m(2), respectively. Key components of OPW, namely pectin and cellulose, were also tested in their pure form, with pectin giving a stable current, while no significant current generation was achieved using cellulose alone as the substrate, thus demonstrating the absence of cellulose-degrading bacteria. Maximum pectinase and polygalacturonase enzyme activities of 18.55 U/g and 9.04 U/g (per gram of substrate), respectively were achieved during orange peel degradation in MFCs. Bacterial identification using 16S rRNA analysis of the initial inoculum fed to the MFC, the biofilm attached to the anode, and the anode suspension, showed significant diversity in community composition. A well-known exoelectrogen, Pseudomonas, was present among the predominant genera in the anode biofilm.

Heavy metals removal by EDTA-functionalized chitosan graphene oxide nanocomposites

Graphene-based two-dimensional materials have been explored in a variety of applications, including the treatment of heavy-metal-rich water/wastewater. Ethylenediaminetetraacetic acid (EDTA)-functionalized magnetic chitosan (CS) graphene oxide (GO) nanocomposites (EDTA-MCS/GO) were synthesized using a reduction precipitation method and applied to the removal of heavy metals, such as Pb2+, Cu2+, and As3+, from aqueous solutions. The synthesized nanocomposite was characterized by FT-IR, XRD, SEM, MPMS, zeta-potential and BET analyses. The influence of various operating parameters, such as pH, temperature, metal ion concentration, and contact time on the removal of the metal ions, was investigated. Owing to the large specific surface area, hydrophilic behavior, and functional moieties, the magnetic nanocomposite demonstrated excellent removal ability with a maximum adsorption capacity of 206.52, 207.26, and 42.75 mg g−1 for Pb2+, Cu2+, and As3+, respectively. The equilibrium data was evaluated by Langmuir and Freundlich isotherms, while the heavy metal adsorption reaction kinetics was analyzed by Lagergren pseudo-first-order and pseudo-second-order kinetic models. The nanocomposite was reused in four successive adsorption–desorption cycles, revealing a good regeneration capacity of the adsorbent.

Rice straw-based biochar beads for the removal of radioactive strontium from aqueous solution

Biochars from agricultural residues have recently attracted significant attention as adsorbents for purifying contaminated water and wastewater. In this study, the removal of strontium from aqueous solutions was investigated using rice straw-based biochar (RSBC) beads in both batch and continuous fixed-bed column systems. The RSBC beads had negatively charged surfaces and exhibited a large surface area (71.53m2/g) with high micro-porosity. The synthesized beads showed a maximum adsorption capacity of 175.95mg/g at an initial strontium concentration of 10g/L at 35°C and pH7. Furthermore, they showed a good selectivity toward strontium ions in the presence of competing ions such as Al3+, Mg2+, and K+. The effects of different operating conditions like flow rate and initial strontium concentration were investigated in the fixed-bed column reactor. The Thomas, Adams-Bohart, and Yoon-Nelson models were applied to the experimental data to predict the breakthrough curves using non-linear regression. Both the Thomas and the Yoon-Nelson models were appropriate for describing entire breakthrough curves under different operating conditions. Overall, RSBC beads demonstrate great potential as efficient adsorbents for the treatment of wastewater polluted with strontium in a continuous operation mode.

Biodegradation of the sulfonamide antibiotic sulfamethoxazole by sulfamethoxazole acclimatized cultures in microbial fuel cells

Microbial fuel cells (MFCs) are known for their ability to enhance the removal rate of toxins while generating power. This research presents a performance assessment of MFCs for power generation and sulfamethoxazole (SMX) degradation using SMX acclimatized cultures. Experiments were performed in MFC batch mode using different SMX concentrations in synthetic wastewater. The experimental results showed that voltage generation was >400mV up to the SMX concentration of 0.20mM (at 400Ω external resistance). Control experiments supported the inference that biodegradation was the main process for SMX removal compared to sorption by SMX acclimatized cultures and that the process results in efficient removal of SMX in MFC mode. The specific removal rates of SMX in MFC with SMX acclimatized sludge were 0.67, 1.37, 3.43, 7.32, and 13.36μm/h at initial SMX concentrations of 0.04, 0.08, 0.20, 0.39, and 0.79mM, respectively. Moreover, the MFC was able to remove >90% of the TOC from the wastewater up to SMX concentrations of 0.08mM. However, this TOC removal produces negative effects at higher SMX concentrations due to toxic intermediates. Microbial community analysis revealed large changes in bacterial communities at the phylum, class, and genus levels after SMX acclimatization and MFC operation. Thauera, a well-known aromatic-degrading bacteria, was the most dominant genus present in post-acclimatized conditions. In summary, this study showed that acclimatized sludge can play an important role in the biodegradation of SMX in MFCs.

Effect of wastewater containing multi-walled carbon nanotubes on dual-chamber microbial fuel cell performance

The use of engineered nanomaterials is continuously increasing in commercial products and industrial applications, and a significant portion of these materials may enter domestic and industrial wastewater streams and subsequently, wastewater treatment plants. Microbial fuel cells (MFCs) represent a new emerging technology for simultaneously generating bioenergy and treating wastewater. In this work, the performance of a MFC with wastewater containing multi-walled carbon nanotubes (MWCNTs) was evaluated. No significant negative effect on power generation was observed for MWCNT concentrations from 10 mg L−1 to 200 mg L−1. In fact, there was a stimulating effect due to the increased conductivity resulting from the MWCNTs, therefore slightly enhancing voltage generation (linked to enhanced electron transfer rate). The maximum voltage generation was increased from 0.61 V to 0.68 V (at 1000 Ω external resistance). Low lactate dehydrogenase release at all concentrations of MWCNTs showed that no adverse cell piercing took place and the wrapping of cells by MWCNTs most likely occurred. Chemical oxygen demand (COD) removal efficiency was also enhanced from 74.2% to 84.7%. The experimental results demonstrated that wastewater containing MWCNTs can be applied to MFCs for generating bioelectricity and treating wastewater without any significant adverse effect on performance.

Magnetite nanoparticles supported on organically modified montmorillonite for adsorptive removal of iodide from aqueous solution: Optimization using response surface methodology

Magnetite nanoparticles supported on organically modified montmorillonite (MNP-OMMTs) were successfully synthesized by a facile coprecipitation method. The surface of natural clay was modified using a cationic surfactant, hexadecyltrimethylammonium. The synthesized MNP-OMMTs were used as an adsorbent to remove iodide from aqueous solutions. The maximum adsorption capacity of the adsorbent was 322.42mg/g, which is much higher than other previously reported adsorbents for removing iodide in aqueous solution. The experimental data were well fitted to a pseudo-second-order kinetic model, and the adsorption behavior followed the Langmuir isotherm. A thermodynamic study indicated that iodide adsorption was spontaneous and endothermic. The individual and combined effects of key process parameters (pH, temperature, and initial iodide concentration) were studied using a response surface methodology. The maximum iodide removal efficiency of 93.81% was obtained under the optimal conditions of pH3.9, a temperature of 41.3°C, and an initial iodide concentration of 113.8mg/L.

Adsorption of Ethylbenzene and Tetrachloroethylene Using Natural and Organically Modified Clays

The vapor of two volatile organic compounds, ethylbenzene, and tetrachloroethylene were adsorbed to natural and organically modified montmorillonite clays, respectively. The surface of clay was modified using a cationic surfactant, hexadecyltrimethylammonium (HDTMA) with a cation-exchange capacity of 161 mg HDTMA/g-clay. The adsorption was performed by passing the mixture of nitrogen and the vapor of organic compounds through a fixed adsorption bed. Desorption was also conducted by allowing the pure nitrogen to flow through the loaded bed. The experiments were conducted at 24, 34, and 44°C in order to investigate the effect of temperature on the adsorption and desorption behavior of the two types of clays. The adsorption data were modeled with the BET adsorption isotherm equation. The isotherms of natural and modified clays exhibited a typical favorable Type I behavior. The temperature effect on the adsorption capacity was significant when the natural clay adsorbed the two organic compounds, while the temperature effect was minor when the modified clay was used. The desorption rate constants were in the order of 10−5 min−1 and these values were not greatly varied when the type of clay changed from natural to modified clay.

Mercuric Ion Capturing by Recoverable Titanium Carbide Magnetic Nanocomposite

Two-dimensional metal carbides and nitrides (MXenes) have attracted increasing attention for application in water/wastewater treatment. The functionalization of MXenes to increase their stability while demonstrating high pollutant removal can facilitate sustainable water/wastewater treatment processes. In this study, the highly stable magnetic titanium carbide (Ti3C2Tx) MXene nanocomposite (MGMX nanocomposite) was successfully synthesized through a facile hydrothermal approach and was tested for aqueous-phase adsorptive removal of mercuric ions. The synthesized MGMX nanocomposite was studied using characteristic analyses, showing high stability as revealed by zeta-potential analysis and dynamic light-scattering technique. The MGMX nanocomposite presented excellent Hg(II) removal in a wide range of pH conditions, and an exceptional maximum experimental Hg(II) uptake capacity of 1128.41mgg-1 was observed. The adsorption behavior was investigated using the Redlich-Peterson adsorption isotherm, pseudo second-order kinetics, and thermodynamics models. In the adsorption/desorption investigation, the MGMX nanocomposite was reusable for up to five cycles of adsorption/desorption. The stability, hydrophilic nature, available adsorptive surfaces, and easy separation after reaction make the MGMX nanocomposite an efficient sorbent for the removal of toxic Hg(II) for water purification.