Nghiên cứu sự trao đổi và hấp phụ các cation kim loại trên bề mặt kaolinite từ lý thuyết phiếm hàm mật độ

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Tác giả: Ngọc Trí Nguyễn

Ngôn ngữ: vie

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Thông tin xuất bản: Tạp chí Khoa học Trường Đại học Quy Nhơn, 2024

Mô tả vật lý: tr.9

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ID: 461854

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In this study, metal cations exchange and adsorption processes onto kaolinite surfaces are investigated using first-principles calculations. Obtained results indicate that the exchanges of cations are mostly unfavorable, and the Al sites are conveniently replaced compared to Si sites. The metal cations are adsorbed strongly onto kaolinite surfaces at both O-slab and H-slab. The adsorption ability of metal cations decreases in the order of Li+ >
K+ >
Na+ >
Ca2+ >
Al3+ >
Fe3+ >
Cr3+ >
Mg2+ at the PBE functional. Remarkably, the insertions of Li+ and Mg2+ into the lattice structure of kaolinite are found at H-slab following the formation of Li-O and Mg-O new bonds, respectively. The intercalation into kaolinite by Ca2+ is observed in forming Ca-O bonds for both H-slab and O-slab. For Na+, K+, and Cr3+, the favorable attachment is located at the O-slab upon adsorption. Besides, the Al3+ and Fe3+ ions interact preferably on the H-slab. The analyses of the density of states and electron localization function clarify the appearance of M-O covalent bonds upon the adsorption process. Further, K+ is suggested as a promising addition to kaolinite surfaces for the efficient adsorption and removal of organic compounds in environments.Trong nghiên cứu này các quá trình trao đổi và hấp phụ các cation kim loại được khảo sát sử dụng các tính toán theo các nguyên lý đầu tiên. Các kết quả thu được chỉ ra rằng, các sự trao đổi cation hầu như không thuận lợi, trong đó các vị trí Al3+ dễ thay thế hơn Si4+. Các cation kim loại được hấp phụ mạnh mẽ trên kaolinite ở cả hai mặt H-slab và O-slab. Kết quả tính tại phiếm hàm PBE, khả năng hấp phụ các cation kim loại giảm theo thứ tự Li+ >
K+ >
Na+ >
Ca2+ >
Al3+ >
Fe3+ >
Cr3+ >
Mg2+. Đáng chú ý, sự xâm nhập vào cấu trúc tinh thể của kaolinite được phát hiện đối với Li+ và Mg2+ ở mặt H-slab cùng với sự hình thành tương ứng các liên kết mới Li-O và Mg-O. Trong khi đó, sự xen vào giữa các lớp kaolinite bởi các cation Ca2+ được phát hiện với sự hình thành các liên kết Ca-O với cả hai mặt H-slab và O-slab. Đối với Na+, K+, hay Cr3+, sự ưu tiên ở bề mặt O-slab trong quá trình hấp phụ. Trong khi đó, Al3+ và Fe3+ tạo sự tương tác tốt ở trên bề mặt H-slab. Các phân tích mật độ trạng thái và phân bố mật độ electron chứng tỏ sự hình thành các liên kết cộng hóa trị M-O trong quá trình hấp phụ. Hơn nữa, K+ được đề xuất như là sự bổ sung trên bề mặt kaolinite đối với các khảo sát xa hơn về hấp phụ và loại bỏ hiệu quả các hợp chất hữu cơ trong các môi trường.

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