HA型粘结剂性能评判的研究

冷固结球团直接还原工艺成功的关键因素之一是成型粘结剂的选用。粘结剂性能评判 ,传统的方法是通过考查球团矿的机械强度来说明粘结剂性能的优劣 ,步骤繁锁。经过试验研究 ,本文提出了用粘度大小来评判粘结剂性能的直接方法并从理论上进行了论证。对于 HA型复合粘结剂 ,在六速旋转粘度计上测量 ,50 g复合粘结剂的粘度若大于或等于 6.5× 1 0 -3 Pa·s,表示粘结剂性能较好 ,能满足铁精矿冷固球团直接还原工艺的要求 ;若小于或等于 3.0× 1 0 -3 Pa· s,则表示该粘结剂性能较差。     

高纯超细活性γ-Al2O3的应用及其研究进展

从γ-Al2O3的结构和特性出发介绍了高纯超细活性γ-Al2O3在高性能特种陶瓷合成、催化剂或其载体及化学机械抛光等方面的应用，综述了国内外有关高纯超细Al2O3多种制备方法的研究现状和发展趋势。     

Purification and characterization of extracellular chitinase from a novel strain Aspergillus fumigatus CS-01

Twelve samples derived from different locations in south central area of China are treated by enrichment and spread-plate technique for initial screening. Seven chitinase-producing strains are isolated. The chitinase present in the culture supernatant of strain CS-01 possesses the maximum activity of 0.118 U/mL. Analysis of the morphological feature and the ITS rDNA sequence reveals that strain CS-01 belongs to Aspergillus fumigatus. Production of the chitinase is regulated by a inducible way and the maximum activity appears at 36 h in colloidal chitin culture. Purification of the chitinase is carried out by salting out, gel filtrate chromatography and anion exchange chromatography sequentially. Native-PAGE and SDS-PAGE indicate that the chitinase from A. fumigatus CS-01 is a monomer with the relative molecular mass estimated to be 4.50×10⁴. Its maximum activity appears at pH 5 and 55 °C. The chitinase is stable at pH 4.0–7.5 and below 45 °C. Foundation item: Projects(50621063, 50674101) supported by the National Natural Science Foundation of China     

Bioleaching of chalcocite by mixed microorganisms subjected to mutation

Mixed microorganisms with elevated activity of chalcocite-leaching were screened by mutation methods. The original microorganisms collected from acid mine drainage of different sites were mixed and then treated with mutagens NO₂⁻, diethyl sulfate (DES), UV and their combinations, respectively. Five groups of mixed microorganisms with much stronger ore-leaching ability were obtained by screening on the leaching media. Among them, group E of mixed microorganisms (treated with 1% DES for 60 min) with the best performance on chalcocite-leaching, increases the content of Cu²⁺ by 101.4% in 20 d of leaching compared with the control culture. In addition, group E is more tolerant to Cu²⁺ in media than the control without mutation treatment. Analysis for the diversity of microbial clones indicates that half of operational taxonomic units (OTUs) in group E are Acidithiobacillus ferrooxidans. These observations suggest that group E might have potentials for industrial application. Foundation item: Project(50321402) supported by the National Natural Science Foundation of China; Project(2004CB619201) supported by the Major State Basic Research and Development Program of China     

Identification and fermentation optimization of protopectinase-overproducing strain Aspergillus niger CD-01 for pectin production

In order to solve the citrus peel resource waste problem and minimize the drawbacks of chemical extraction of pectin, a protopectinase-overproducing strain CD-01 for pectin production was isolated from a pit soil dumped with perished orange in Changde City, Hunan Province of China. The strain CD-01 had the same morphology and 28S rRNA gene sequence (FJ184995) as that of Aspergillus niger (ATCC 64028). It was thus identified and named as Aspergillus niger CD-01. The fermentation condition was optimized based on L₉(3⁴) orthogonal experimental design and the variances analyses. The results show that the optimal condition for producing pectin is as follows: time 36 h, temperature 35 °C, pH 5, and urea as the nitrogen source. Under this condition, the pectin yield can reach up to 24.5%. This shows a great potential of Aspergillus niger CD-01 in pectin extraction from citrus. Foundation item: Projects(50621063, 50674101) supported by the National Natural Science Foundation of China     

Bioleaching of pyrrhotite by Sulfobacillus thermosulfidooxidans

The bioleaching of pyrrhotite was investigated using Sulfobacillus thermosulfidooxidans.The effects of pH,pulp concentration,inoculation amount,external addition of ferrous and ferric ions were examined.The pH is found to exert a profound effect on the leaching process for controlling the bacterial activity and precipitation of ferric ions mainly as jarosite.The results show that low pulp content increases the leaching rate of iron.The inoculation amount from 1×107 cell/mL to 1×108 cell/mL has positive effects on the leaching rate.The results also imply that addition of ferrous sulfate（1 g/L） is required for the bacteria to efficiently drive the extraction of iron,however,the leaching efficiency has no obvious enhancement when 2 g/L ferrous sulfate was added.Comparatively,addition of ferric sulfate（2 g/L） significantly inhibits the bioleaching process.At the end of bioleaching,jarosite and sulfur are observed on the surface of pyrrhotite residues by using XRD and SEM.With the passivation film formed by jarosite and sulfur,the continuous iron extraction is effectively blocked.     

2-氨基-5-巯基-1,3,4-噻二唑缓蚀剂结构的密度泛函计算

采用密度泛函量子化学计算方法,获得了在B3LYP/6-311 G(2d)(5D,7F)理论水平上2-氨基-5-巯基-1,3,4-噻二唑(简称AMT)4种互变异构体的平衡几何构型、能量和电荷分布,证实了4种互变异构体的所有原子处于同一平面,且有一种异构体最稳定.研究结果表明:AMT4种异构体中的环骨架具有芳香性,AMTc与Cu形成的缓蚀膜层是Cu(Ⅰ)与AMTc中的7N和2S原子分别形成共价键和配位键相互交错而成.计算了AMT4种异构体的谐振频率和红外光谱强度.     

Cu~(2+)对Fe~(2+)在T.f菌修饰粉末微电极上氧化行为的影响

Fe2 + 的氧化在细菌浸矿过程中具有重要作用 ,细菌浸铜过程中 ,Cu2 + 的存在对T .f菌的生长代谢和其氧化Fe2 + 的能力有一定影响。制备了T .f菌修饰碳粉粉末微电极 ,研究了Cu2 + 存在下Fe2 + 在T .f菌修饰粉末微电极上氧化的电化学反应机理 ,并测定了相应的电极过程动力学参数。循环伏安研究表明 ,Cu2 + 的存在不影响Fe2 + 在T .f菌修饰粉末微电极上的氧化反应的可逆性。对电极稳态及暂态过程研究表明 ,当Cu2 + 浓度在 12mmol/L以下时 ,Cu2 + 的存在不会抑制Fe2 + 在T .f菌修饰粉末微电极上的氧化 ,适量Cu2 + 加强T .f菌氧化Fe2 +的作用是在于其加快了电荷传递速率     

高岭石脱水反应的非等温热重法研究

在系统分析非等温固相反应特点的基础上,建立了非等温脱水反应速率方程.采用非等温热重法、通过计算机辅助计算,对高岭石脱水反应动力学规律进行了研究.结果表明:由于高岭石晶体结构中内、外羟基脱除的顺序不同,其脱水反应机制在反应分数(α)为0.7左右时发生改变.在反应前期(0＜α＜0.7)时,脱水反应遵循二维扩散控制规律,脱水反应表观活化能为159.682 kJ/mol、表观频率因子为1.007×10 10/min.     

丁基黄原酸甲酸乙酯的合成及对黄铜矿浮选研究

考察了不同条件对丁基黄药合成丁基黄原酸甲酸乙酯(BXEF)的影响。研究结果表明,合成BXEF反应的最佳工艺参数为：反应温度25℃,反应时间200 min,n(丁基黄药)：n(氯甲酸乙酯)=1．04：1。在此条件下,BXEF的产率可以达到94．5%。对江西永平铜矿硫化物矿石的浮选试验结果表明,与丁基黄药相比,BXEF对硫化铜矿有更高的浮选回收率,而且铜精矿中铜的品位更高。对丁基黄药和BXEF的量子化学计算结果表明,BXEF比丁基黄药有更低的能量,稳定性更强。