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Adsorptive performance of mesoporous silica-modified Bangkok clay as an alternative GCL
(2026-06-05)
Sathawong, Sidthipong
;
Asadullah
;
Somsiripan, Thotsaporn
;
Tohdee, Kanogwan
;
Jongsomjit, Bunjerd
This study investigates the adsorption performance and characterisation of mesoporous silica-modified Bangkok clay (BKC) as a geosynthetic clay liner (GCL) for removal of heavy metal in aqueous solution. BKC was modified with mesoporous SBA-15 to create a mesoporous silica-coated clay (5SBS), enhancing its surface area, porosity, and adsorption efficiency. The materials were characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller (BET), and X-ray photoelectron spectroscopy techniques while adsorption experiments of Cu(II), Zn(II), and Cd(II) ions under controlled conditions in ternary systems. The 5SBS composite exhibited superior physicochemical characteristics, including a BET surface area of 67.45 m2/g and well-distributed mesopores. Adsorption kinetics followed a pseudo-second-order model, indicating chemisorption as the dominant mechanism. Equilibrium isotherm data fit best with the Langmuir and Sips models, suggesting monolayer adsorption on homogenous surfaces. The maximum uptake capacities for 5SBS were 31.74, 17.96, and 14.26 mg/g for Cu(II), Zn(II), and Cd(II), respectively, outperforming unmodified BKC and closely matching bentonite. Enhanced thermal stability and minimal pore structure degradation post-adsorption confirmed its suitability for harsh environmental conditions. Metal adsorption has mainly occurred at the surface of the mesoporous silica-modified clay by bonding with surface functional groups. Hydraulic conductivity results further indicate that SBA-15 modification effectively reduces permeability and chemical sensitivity of BKC, maintaining performance comparable to bentonite through stable pore-blocking mechanisms. These findings highlight 5SBS as sustainable alternative to bentonite in GCL, with potential implications for contaminant protection.
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Fungal Transformation and Oxalate-Mediated Mineralization of Heavy Metal Oxides by Aspergillus aculeatus
(2026-04-01)
Sawangchart, Thanakorn
;
Chutipaijit, Sutee
;
Meksiriporn, Bunyarit
;
Narueban, Worapat
;
Tilokkarn, Worrathon
Fungal transformation is increasingly recognized as an important process influencing metal solubilization and immobilization in soil environments. In this study, a fungal strain (PTW4) isolated from mining-contaminated soil was molecularly identified as Aspergillus aculeatus. The strain was evaluated for its ability to solubilize and transform several heavy metal oxides, including ZnO, Pb<inf>3</inf>O<inf>4</inf>, Cu<inf>2</inf>O, and MoO<inf>3</inf>. PTW4 produced consistent halo formation across all tested oxides, accompanied by progressive acidification of the culture medium, suggesting organic acid-mediated solubilization. Characterization of extracellular precipitates by SEM-EDS and XRD indicated mineral phases consistent with oxalate-associated biominerals, including zinc oxalate dihydrate (ZnC<inf>2</inf>O<inf>4</inf>·2H<inf>2</inf>O), lead oxalate (PbC<inf>2</inf>O<inf>4</inf>), and copper oxalate hydrate (CuC<inf>2</inf>O<inf>4</inf>·xH<inf>2</inf>O). These minerals represent low-solubility phases that may reduce metal mobility in the surrounding environment. In contrast, molybdenum did not precipitate under the experimental conditions, suggesting metal-specific constraints in fungal biomineralization processes. Although organic acid production was not directly quantified, identification of oxalate mineral phases supports an oxalate-associated mineralization mechanism. Overall, the results provide evidence for heavy metal solubilization and selective extracellular precipitation consistent with oxalate biomineral formation by A. aculeatus PTW4, highlighting its potential relevance to fungal-mediated bioremediation and selective bioleaching processes.
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Synthesis, Scrutiny, and Applications of Bio-Adsorbents from Cockle Shell Waste for the Adsorption of Pb and Cd in Aqueous Solution
(2023-04-01)
Panpho, Phakakorn
;
Vittayakorn, Naratip
;
Sumang, Rattiphorn
Heavy metals in wastewater represent one of the most serious concerns around the world. They cause significant harm to human health. Cockle shells have been considered a source of calcium carbonate (CaCO<inf>3</inf>), but their shells are disposed of as waste that pollutes the coastal environment. CaCO<inf>3</inf> has attracted considerable attention as an adsorbent for heavy metals. To ensure the meaningful use of cockle shell (CS) waste and achieve a zero-waste production system, in this study, CaCO<inf>3</inf> powder was synthesized from CS. It was characterized using XRD, TA/DTA, FESEM, and AAS. The XRD results illustrated that partial phase changes occur from aragonite (natural shell) to calcite (CaCO<inf>3</inf>), calcium hydroxide (Ca(OH)<inf>2</inf>), and calcium oxide (CaO) during heating. The calcined CS presented excellent adsorption performance for Pb and Cd. The Pb removal efficiency scores were about 97%, 96%, and 99% and the Cd removal efficiency scores were 100%, 98%, and 99% in a shorter time for calcined CS at 700 °C, 900 °C, and 950 °C, respectively. The results of this study show that the calcium carbonate from CS is an effective and low-cost adsorbent for the adsorption of Pb and Cd in aqueous solution.
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Size Distributions of Inhalable Particulate Matter and Particle-bound Heavy Metals and Their Potential Occupational Health Risk Related to Informal E-waste Recycling in Thailand
(2022-02-08)
Keawhanu, Thidarat
;
Sukonthamut, Sujitra
;
Suriyawong, Achariya
;
Junyapoon, Suwannee
Concentrations and size distributions of atmospheric particulates and particulate-bound heavy metals in different inhalable fractions were studied in working areas during manual dismantling, thermal cutting and cable sheath burning activities. The particulate samples were collected on quartz fiber filters using an eight-stage cascade impactor with flow rate of 28. 3 l min-1. Mass concentrations of the particles were measured in each size fraction. Heavy metals bound on the particles were extracted with acid digestion and then analyzed using Atomic Absorption Spectrophotometer. Risk assessment of worker exposure to the particles was determined. The results indicated that the concentrations of ultrafine (d<inf>ae</inf> < 0.43 μm), fine (0.43 < d<inf>ae</inf> < 2.1 μm) and coarse (2.1 < d<inf>ae</inf> < 10 μm) particles were in the ranges of 14.49-62.04, 57.51-120.26 and 153.26–646.99 μg m−3 during manual dismantling, 363.41-1,011.95, 2,105.40-4,899.11 and 1,698.54-7,075.61 μg m−3 during thermal cutting and 364.73-1,694.72, 1,953.33-4,431.41 and 1,385.97-6,126.13 μg m−3 during cable sheath burning, respectively. The concentrations of PM<inf>2.1</inf> and PM<inf>10</inf> released from these activities did not exceed the OSHA PEL threshold limits. Heavy metals adsorbed on the particles (Fe, Cr, Zn, Cu, Pb, Mn) detected during manual dismantling did not exceed the TWA standard. Concentrations of Cr and Pb during cable sheath burning highly exceeded the standards whereas Pb concentrations during thermal cutting slightly exceeded the standard. The heavy metals released from these recycling activities were more enriched on coarse mode than fine mode. Inhalation exposure to Cr, Pb and Mn posed a potential health risk to the workers.

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