Tạp chí Phân tích Hóa, Lý và Sinh học

      In this paper, catalyst Cu-, Fe-doped TiO2 with various ratio were tested by reaction of photodegardation of pesticide (2,4,5-T) in water. Experience results showed that the highest photodegradation reached on 5%Cu/TiO2 and 5%Fe/TiO2. This report also supposed the photodegradion reaction of 2,4,5-T on this heterojunction of TiO2 doping Cu and Fe conform to Langmuir-Hinshelwood kinetic equation and the experiences results showed that with catalysts x%Cu/TiO2, the decrease of 2,4,5-T concentration was much faster than that with x%Fe/TiO2 and TiO2 pure (in the same doping ratio).Keywords: Photocatalyst, catalyst kinetic, photodegradation, pesticide.

   The coating nanomixed oxides CeO2-Mn2O3 on activated charcoal was synthesized by sol-gel method combustion method using polyvinyl alcohol (PVA). The percentage of mixed oxides in materials was varied at 8, 10, 12 and 15 %. Optimum conditions were applied to synthesize materials which is molar ratio of Mn2+/Ce4+ =1/1. Gel formation was obtained at temperature of 80oC, molar ratio of   (Mn2++Ce4+)/PVA=1/3 pH 4 and calcination temperature of 350oC for 2 hours. The Ce(IV) concentration of synthesized material was determined by titration method using diethylene triamine pentaacetic acid (DTPA) with asenazo indicator. Whereas, Mn(II) concentration was determined by atomic absorption spectrophotometry on Perkin Elmer Analyst 200 at wavelength of 279.5 nm. Arsenic and ammonium adsorption on materials were illustrated. The adsorption capacity of As(III) and ammonium by nanomixed oxides on activated charcoal is 4.10 mg/g and 2.89 mg/g, respectively. From the results, these composite materials promises a great application to treat As(III) and ammonium in aqueous solution.Keywords: CeO2 – Mn2O3, PVA, sol – gel, ammonium, arsenic, adsorption.  

Hầm biogas hộ gia đình ở nông thôn Việt Nam đã chứng minh hiệu quả xử lý chất thải chăn nuôi nhất định, đồng thời tạo ra nhiên liệu khí sinh học cho các hộ gia đình. Để đánh giá hoạt động của hầm biogas xử lý chất thải nuôi heo cũng như khả năng xử lý kết hợp với chất thải sinh hoạt từ các hộ gia đình, nghiên cứu đã thực hiện trên hầm biogas trong thực tế có thể tích 6m3. Khảo sát được thực hiện trong 3 giai đoạn chạy tại đó, giai đoạn 1 và giai đoạn 2 hầm biogas chỉ xử lý phân lợn ở các tải trọng khác nhau, và ở giai đoạn 3, chất thải sinh hoạt hữu cơ được bổ sung để tăng tải trọng hệ thống lên 10% so với chế độ 2. Kết quả cho thấy, hầm hoạt động ổn định trong 60 ngày khảo sát ở giai đoạn 3, không chỉ cho lượng khí sinh ra cao hơn 58% mà còn có năng suất sinh khí riêng (m3 mê tan/kgVS) cao hơn 39% so với chế độ không bổ sung chất thải rắn. Nước thải sau xử lý có hàm lượng COD trung bình 1588 mg/L, cần được xử lý trước khi thải ra môi trường.

   In this study, the content of cafein e (CF), theobromine (TB) and theophylline (TP) were determined in 35 tea samples, including green tea, black tea and different geographical origins (Yen Bai, Tuyen Quang, Thai Nguyen, Ha Giang, Hoa Binh and Lam Dong). High performance liquid chromatography (HPLC) method was used with the optimal separation conditions investigated. The mobile phase was a mixture of acetonitrile and 20 mM, pH = 3 phosphate buffer solution (15:85 v / v) with maximum absorption wavelength at 271 nm at room temperature. Extraction conditions was optimized by factorial design of experiments. Optimum conditions were temperature extraction of 99 ° C, extraction time of 8 minutes. The amounts of TB, TP and CF in tea had been determined by HPLC using the calibration curve. CF, with an average content of 65,8 mg g-1 was the major  methylxanthine. TB and TP had average contents of 5,288; 5,859 mg g-1, respectively. The coefficient of variation of the method is less than 1.0%. The recovery for CB, TP and CF ranged from 99.0% to 101.8%. The results of the 35 tea sample colected in different areas showed  the weight percentages of the three substances are different. The contents of xanthines in Vietnamese tea reflectthe sources of tea from diferent areas among  Northern Midland region, Northern Mountainous region and Tay Nguyen region of Vietnam. Keywords: cafein e, theobromine, theophylline; original sources; tea; HPLC   

    The multi-ligand complexation in Nd(III) - 4-(3-methyl-2-pyridylazo)resorcinol (3-CH3-PAR) -acetic acid (CH3COOH) system has been investigated by spectrophotometric method. Thecolour Nd(III)-(3-CH3-PAR)-CH3COOH complex, with composition 1 : 2 : 1, is formed mostfavourably at pH = 8.5 ÷ 11.5 and has an absorption maximum at 532 nm. The morlarabsorption coefficient and stability constant have been determined. It was shown that thecomplex of Nd(III)-(3-CH3-PAR)-CH3COOH is stable with time in accordance with the Beer'slaw in a rather large limit interval.

   In this study, benzotriazole (BTA) used as a good inhibitor on corrosion of copper in 3.5% NaCl or 0.001 M HCl has been studied through immersion tests.  It was found that at the concentration of 4% BTA, the inhibition of corruption of copper by forming a couprous ion- BTA condensation compound in minium 24 hours exposure. The increasing of concentration of NaCl or HCl concentration will increase the corrosion of coper but can be controlled by BTA film. Key words: benzotriazole, corrosion of copper, sodium chloride 

      Complexes of benzaldehyde thiosemicarbazone (HL1), benzaldehyde N(4)- phenyl thiosemicarbazone (HL2), isatin thiosemicarbazone (HL3) and isatin N(4)- methyl thiosemicarbazone (HL4) with copper(II) were synthesized in base medium of NH3. Form of these complexes were Cu(L)2, which L: L1, L2, L3, L4. The chemical structures of ligands and their complexes were characterized by elemental analysis, MS, IR, 1H- NMR and 13C- NMR spectroscopy. The obtained results showed that the ligands are bidentate, coordinated to the copper(II) over N, S- donor atoms. The test in vitro antibacterial activities of the ligands and their complexes against three of positive bacteria types: Lactobacillus fermentum, Bacillus subtilis, Staphylococcus aureus and three of negative bacteria types: Salmonella enterica, Escherichia coli, Pseudomonas aeruginosa and one type of fungus: Candida albican show that Cu(L2)2 againt 3/7 bacteria and fungus type.

   Styrene - deproteinized natural rubber (DPNR) grafting copolymerization using emulsion polymerization with tetraethylenepentamine (TEPA) - tert-butyl hydroperoxide (TBHPO)  as a redox initiator was investigated. The DPNR was prepared by adding SDS (sodium dodecyl sulfate) and urea into the high-ammoniated natural rubber (HANR) latex and followed by centrifugation. DPNR was successfully prepared with lowest nitrogenous content about 0.015 % w/w by centrifugation at 10000 rpm for three times repetition. Then 1HNMR was used to confirm the graft copolymer. The thermal properties of DPNR and graft styrene copolymer were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The result demonstrates the ability of styrene grafting to improve the thermal stability of DPNR.  

   This work researches the factors effected to behaviour of arsenic releasing from pyrite tail after exploitatin in laboratory model scale. That were pH, metallic ions, bacteria effected to mobility of As(III) and As(V) under anoxic and oxygen present condition. The atates of arsenic and heavy metals are important factors influencing to their moving, transportation and deposition in environment and cause environmental pollution. In the oxygen condition and high pH values, As(V) ) is more dominant than As(III) and in the anoxic condition As(III) is more dominant.  In more reductive conditions, arsenic concentration is decreased together with reducing of iron(II) concentration, this prove that, the As(III) transfered to arsenide and precipitated with sulfide and another ions. The sulfate-reducing bacteria are very important to arsenic metabolism, but they are only well metabolized in neutral pH. In the real pyrite taling site, the pH commonly is quite low during the intensive weathering period so these bacteria mostly develope in the post-weasthering period, where pH values increased near neutral. The study improved knowledge about environmental protection in ore mining tail with  purpose of environmental pollution reduction.Keywords: Arsenic mobilization, behaviour of arsenic, arsenic releasing from pyrite. 

     The ligand H-7CPTSC was synthesized by condensation reaction between 1-pyrandehyde and relevant thiosemicarbazide. The complexation of the ligand with cooper ion occurred in aqueous ammonia solution. Using different physical methods such as infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry, and X-ray single crystal diffraction, it is confirmed that the ligand and its copper complex have been successfully synthesized. Also, the complex shows a metal:ligand ratio is of 1:2.Keywords: thiosemicarbazone, pyrene, copper, metal complex, X-ray structure.