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Vật liệu biochar từ tính được tổng hợp bằng phương pháp nung vỏ trấu ở 500°C trong môi trường nitơ, sau đó cố định các oxit sắt lên bề mặt biochar sử dụng phương pháp thủy nhiệt hỗn hợp Fe(OH)2 và Fe(OH)3 được tạo ra từ tiền chất Fe2+ và Fe3+ trong môi trường kiềm. | Nghiên cứu tổng hợp vật liệu biochar từ tính và ứng dụng để xử lý xanh methylen trong nước VNU Journal of Science Natural Sciences and Technology Vol. 36 No. 1 2020 9-19 Original Article Synthesis of Magnetic Biochar and Their Application for the Treatment of Methylene Blue in Water Tran Dinh Trinh Nguyen Thi Hoai Phuong Faculty of Chemistry VNU University of Science Vietnam National University Hanoi 19 Le Thanh Tong Hoan Kiem Hanoi Vietnam Received 13 August 2019 Revised 22 December 2019 Accepted 13 January 2020 Abstract Magnetic biochar materials were synthesized by heating rice husk at 500 C under nitrogen environment then fixing iron oxides on biochar surface using hydrothermal method applied to Fe OH 2 and Fe OH 3 which were generated from respective precursors Fe2 and Fe3 in alkaline environment. The presence of iron oxides on the surface of biochar and the surface characteristics of iron-composite materials were studied with the aid of modern physicochemical analysis techniques SEM EDX BET FT-IR XRD . Magnetic biochar materials were relatively porous with an average spectific surface area of 62.1 m2 an average capillary size of about 17.2 nm. The mixture of iron oxide particles were revealed within the nano scale about 15 nm . The methylene blue adsorption efficiency depended upon the amount of adsorbent adsorption time pH of solution and pollutant concentrations. Specifically the optimal conditions for maximum adsorption efficiency were as follows 0.02 g L of magnetic biochar the adsorption equilibrium time was 3 hours at room temperature in a solution of pH7 The efficiency of methylene blue adsorption in optimal conditions reached over 98.82 . The Langmuir and Freundlich isotherm adsorption models all described well the methylene blue adsorption process at room temperature with the regression coefficients R2 of 95.0 and 90.0 respectively. The maximum adsorption capacity of methylene blue calculated by Langmuir model was 22.4 mg g. Keywords Biochar .
