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    Process Optimization and Kinetics Study of Metals Leaching from Spent Hydrocracking Catalysts by Cell-free Medium Filtrate of Aspergillus aculeatus
    (2026-10-01)
    Sawangchart, Thanakorn
    ;
    Meksiriporn, Bunyarit
    ;
    Sutjaritvorakul, Thanawat
    Hydrocracking catalysts (HCC) are widely used in petrochemical refinery catalytic processes. Although these catalysts are frequently reusable, the efficacy of HCC gradually declines. This procedure leads to the production of a large amount of spent hydrocracking catalyst (SHCC), which contains valuable metals as well as hazardous chemical wastes. The pyro-hydro-metallurgical approach for metal restoration from catalyst waste is insufficient for environmental sustainability. The application of biological techniques is a more environmentally friendly strategy. Fungal leaching has emerged as an alternative method for the recovery of metals. Although metal recoveries were moderate, the use of cell-free fungal filtrate enabled rapid leaching under mild conditions, highlighting its potential as a greener and operationally simpler alternative to conventional whole-cell bioleaching. Aspergillus aculeatus was isolated from contaminated soil of a gold mine located in Thailand. The filtrate of the fungal culture medium was utilized for metal leaching, and this experiment was carried out using a Box-Behnken experimental design. The optimum processes included a spent catalyst density of 10% (w/v), a temperature of 50 °C, and a shaking rate of 148 rpm for 180 min, with the catalyst powder size being less than 150 µm. The predicted highest metal recovery rates of 7.98% for Al, 5.27% for Ni, 24.55% for Mo, 11.92% for Fe, and 0.93% for Zn aligned precisely with the actual experimental results. The comprehension of kinetics through the application of the shrink core model indicates that the mechanism of reactions is predominantly influenced by the surface chemical control reaction rather than the diffusion process. The leaching rates of Mo, Fe, Al, Ni, and Zn followed a descending order from highest to lowest.
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    Dip-to-detect electrochemical microfluidic device: Integrating sample collection and automated mixing for on-site detection of heavy metals
    (2026-02-01)
    Khamcharoen, Wisarut
    ;
    Jaewjaroenwattana, Jutamas
    ;
    Wajasen, Kwanchanok
    ;
    Naorungroj, Sarida
    ;
    Jampasa, Sakda
    Human exposure to heavy metals poses a global threat due to their harmful health and environmental effects. Standard analytical methods rely on complex operations and sophisticated instruments, making them costly, labor-intensive, and limited in on-site suitability. This work presents a “dip-to-detect” electrochemical microfluidic device that enables direct sample dipping and automated electrolyte mixing. The device is made using stacked layers of transparent and double-sided adhesive films designed to enable sequential flow control. We implement a fluid-triggered valve to allow direct dipping and store the sample solution inside the channel without leakage. The electrolyte is added to the device without fixed-volume pipetting, activating the valve for rapid mixing with the sample solution. The device is equipped with a near field communication (NFC) controlled potentiostat for the portable detection of Cd(II) and Pb(II) with limits of detection of 90 ppb and 80 ppb, respectively. To validate its performance, the microfluidic device was tested with spiked industrial water samples. The device demonstrated good recovery, ranging from 102.2 % to 116.7 %. The dip-to-detect electrochemical microfluidic device eliminates the need for pipetting and manual mixing. This platform introduces a new alternative for field-deployable sensing and has the potential to inspire future designs focused on simple sample collection, automated reagent handling, and minimal user intervention.