ARSENIC REMOVAL BY NOVEL NATURAL MAGNETIC ROCK MATERIAL FROM ARSENIC-BEARING GROUNDWATER AND ITS COMPARISON WITH SYNTHESIZED MAGNETIC NANOPARTICLE (Invited Presentation)

The arsenic pollution in surface and subsurface water, mobilization and its contamination in agricultural/aquacultural product (by food chain), are an important issue for environmental safety and human health. Thus, the removal of arsenic is an essential concern worldwide, in present decades. Considering this background, present research focuses on the arsenic removal from arsenic-bearing groundwater (AGW) and arsenic-containing-synthetic water (ASW) (2 mg/L) using natural magnetic material (NMM) (rock) and synthesized magnetic material (SMM) by Bacillus pasteurii and humic acid, comparative manner. The natural magnetic rock materials (NMM) were collected from northern part of Taiwan (Lengshueikeng, Yangmingshan National Park) from different site as Site-A (GPS: 25° 9′ 56.88″; 121° 33′ 58.32″), Site-B (GPS: 25° 9′ 52.56″; 121° 34′ 9.48″) and Site-C (GPS: 25° 9′ 44.28″; 121° 34′ 17.04″) with triple replicate (n=3) and used for arsenic removal. The AGW was collected from Santiaolun, Sihu Township, Yunlin County, Taiwan (GPS: 23° 39′ 7.20″; 120° 9′ 32.4″). The AGW (97.56±0.05 μg/L) exceed the WHO limit (10 μg/L) of arsenic in drinking water. The NMM consist of dominantly magnetite, hematite, ferrihydrate, coesite, quartz, and stishovite with the presence of iron (6.25-8.86% Fe₃O₄), which is widespread and important component in sedimentary rocks. The investigation of NMM and SMM in vibrating sample magnetometers, demonstrated the typical magnetization properties, which can be separated after arsenic removal. The thermogravimetric analysis of SMM displayed the existence of organic matter decomposition during particle synthesis. The TEM and SEM exhibited the nanoparticle particle formation within the range of 10-39 nm (10-20 nm particle Fe₃O₄ through B. pasteurii). The study on functional group (before and after removal of arsenic) indicated the existence and binding nature in between arsenic and iron. >90% of arsenic was removed from AGW using Fe₃O₄, Fe₃O₄ (N₂-Environment), Fe₃O₄ with humic acid, and Fe₃O₄ with B. pasteurii after 25 min, 8 min, 13 min and 120 min, respectively. In case of NMM in Site-A, the arsenic removal was observed very fast as 85-87% within 30 second, whereas 95-99%, 93-95% and 88-91% removal detected using the sample of Site-A, Site-B, and Site-C respectively, after 120 min at natural pH (8.31±0.05) of AGW. Thus, NMM (ecofriendly green material) can be applicable for arsenic removal from AGW.