Jin Sun Cha

In this study, hydrochar and pyrochar were made from cellulose, lignin (components of biomass), and corn husk (a type of biomass) through hydrothermal carbonization at 300 ℃ and pyrolysis at 300 ℃ and 500 ℃. Their physiochemical properties and Cd(Ⅱ) adsorption performances were then compared. Additionally, characteristics of hydrochar and pyrochar generated by each process were analyzed, including char generation yield, proximate & ultimate analysis, specific surface area (BET surface area) & porosity analysis, SEM & EDS (Scanning Electron Microscope & Energy Dispersive Spectrometer), FT-IR, pHpzc, and so on. The pyrochar generated at the same temperature (300 ℃) had higher char generation yield, ash content, and oxygen content with more oxygen functional groups than hydrochar. However, pyrochar had a lower specific surface area and pore volume than hypercar. By type of biomass, lignin showed the highest char generation yield. Regarding pHpzc, corn husk had the highest value, followed by lignin and cellulose. Cd(Ⅱ) adsorption characteristics in hydrochar and pyrochar were more suitable for the Langmuir adsorption model. It was found that the Cd(Ⅱ) adsorption amount (116.8 mg/g) was the highest in PC-CH-500, which had high pHpzc and inorganic content. As a result, electrostatic adsorption and cation exchange were the main mechanisms of Cd(Ⅱ) adsorption under the condition of pH solution < pHpzc.

This study investigated factors influencing the flowability of zeolite using three types of commercial zeolites with low flowability – Zeolite-beta, Zeolite-Y, and ZSM-5 - and manufactured a device applying piezoelectric energy to measure their apparent density. Zeolite properties such as flow function (FF) and cohesion by Powder Rheometer, elemental analysis by XRF, specific surface area, pore characteristics, and shape of zeolite particles by FE-SEM, average particle size and size distribution by particle size analyzer were analyzed. Low flowability zeolite could pass through a mesh hole moved by piezoelectric energy. The apparent density measured by the device applying piezoelectric energy was found to be more uniform with a smaller standard deviation than existing density measurement equipment.

Capacitive deionization of saline water is one of the most promising water purification technologies due to its high energy efficiency and cost-effectiveness. This study synthesizes porous carbon composites composed of reduced graphene oxide (rGO) and activated carbon (AC) with various rGO/AC ratios using a facile chemical method. Surface characterization of the rGO/AC composites shows a successful chemical reduction of GO to rGO and incorporation of AC into rGO. The optimized rGO/AC composite electrode exhibits a specific capacitance of ~243 F g-1 in a 1 M NaCl solution. The galvanostatic charging-discharging test shows excellent reversible cycles, with a slight shortening in the cycle time from the ~260th to the 530th cycle. Various monovalent sodium salts (NaF, NaCl, NaBr, and NaI) and chloride salts (LiCl, NaCl, KCl, and CsCl) are deionized with the rGO/AC electrode pairs at a cell voltage of 1.3 V. Among them, NaI shows the highest specific adsorption capacity of ~22.2 mg g-1. Detailed surface characterization and electrochemical analyses are conducted.

The catalytic co-pyrolysis (CCP) of Kraft lignin (KL) with refuse-derived fuels (RDF) over HZSM-5, Ni/HZSM-5, and NiDHZSM-5 (Ni/desilicated HZSM-5) was carried out using pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS) to determine the effects of the nickel loading, desilication of HZSM-5, and co-pyrolysis of KL with RDF. The catalysts were characterized by Brunauer–Emmett–Teller surface area, X-ray diffraction, and NH₃-temperature programed desorption. The nickel-impregnated catalyst improved the catalytic upgrading efficiency and increased the aromatic hydrocarbon production. Compared to KL, the catalytic pyrolysis of RDF produced larger amounts of aromatic hydrocarbons due to the higher H/C_eff ratio. The CCP of KL with RDF enhanced the production of aromatic hydrocarbons by the synergistic effect of hydrogen rich feedstock co-feeding. In particular, Ni/DHZSM-5 showed higher aromatic hydrocarbon formation owing to its higher acidity and mesoporosity.