烷基聚葡糖苷溶液的表面吸附平衡与动力学

用吊片法和气泡最大压力法分别测定了烷基聚葡糖苷(APG)C₉.₆G_1.3水溶液的平衡和动态表面张力,研究了APG水溶液表面的吸附平衡、动力学及其影响因素.测得其cmc(临界胶束浓度)为0.032g/L.吸附过程由初始的扩散控制转变到势垒控制,吸附势垒为4～7kJ/mol.温度升高,平衡和动态表面张力均减小,吸附量增加;加入无机盐,平衡和动态表面张力增大,吸附量亦增加;醇类的吸附使动态表面张力下降速率加快,表明APG与醇分子间有协同吸附作用.     

氢气在炭狭缝微孔内吸附的预测

通过边界的平均场近似,推导二平板狭缝孔格子理论Ono-Kondo吸附等温方程.利用格子气模型特性和微观物理学理论,计算氢分子在石墨平面的最大吸附容量.比较由氢分子在石墨平面二典型聚集状态标定的Ono-Kondo方程,并用预测精度较高的方程计算了与文献相同条件下的吸附等温线.在比较了计算结果、试验结果和GCMC分子模拟结果后,对Ono-Kondo吸附等温方程的特点、理论基础作了分析,指出了方程的适用范围.     

Si(001)-(2×2×1):H表面O2吸附的密度泛函理论研究

A novel model was developed to theoretically evaluate the O2 adsorption on H-terminated Si(001)-(2*2*1) surface. The periodic boundary condition, the ultrasoft pseudopotentials technique based on density functional theory (DFT) with generalized gradient approximation (GGA) functional were applied in our ab initio calculations. By analyzing bonding energy on site, the favourable adsorption site was determined. The calculations also predicted that the adsorption products should be Si=O and H2O. This theoretical study supported the reaction mechanism provided by Kovalev et al. The results were also a base for further investigation of some more complex systems such as the oxidation on porous silicon surface.     

温度对α-Al2O3(0001)表面吸附生长ZnO影响的DFT研究

The adsorption and the growth of ZnO on α-Al2O3(0001) surface at various temperatures were theoretically calculated by using a plane wave pseudopotentials (USP) method based on density functional theory.The average adsorption energy of ZnO at 400, 600 and 800 ℃ is 4.16±0.08, 4.25±0.11 and 4.05±0.23 eV respectively. Temperature has a remarkable effect on the structure of the surface and the interface of ZnO/α-Al2O3(0001). It is found that the Zn-hexagonal symmetry deflexion does not appear during the adsorption growth of ZnO at 400 ℃, and that the ZnO10-10 is parallel with the 10-10 of the α-Al2O3(0001), which is favorable for forming ZnO film with the Zn-terminated surface. It is observed from simulation that there are two kinds of surface structures in the adsorption of ZnO at 600 ℃: one is the ZnO surface that has the Zn-terminated structure, and whose 10-10 parallels the 10-10 of the substrate surface, and the other is the ZnO10-10 //sapphire 11-10 with the O-terminated surface. The energy barrier of the phase transition between these two different surface structures is about 1.6 eV, and the latter is more stable. Therefore,the suitable temperature for the thin film growth of ZnO on sapphire is about 600 ℃, and it facilitates the formation of wurtzite structure containing Zn-O-Zn-O-Zn-O double-layers as a growth unit-cell. At 600 ℃, the average bond length of Zn-O is 0.190±0.01 nm, and the ELF value indicates that the bond of (substrate)-O-Zn-O has a distinct covalent character, whereas the (Zn)O-Al (substrate) shows a clear character of ionic bond. However, at a temperature of 800 ℃, the dissociation of Al and O atoms on the surface of the α-Al2O3(0001) leads to a disordered surface and interface structure. Thus, the Zn-hexagonal symmetry structure of the ZnO film is not observed under this condition     

洁净和氧吸附的Cu(100)表面重构的理论研究

The interaction of atomic oxygen with the clean Cu(100) surface has been studied by means of cluster and periodic slab models density functional theory in the present paper. The Cu(4,9,4) cluster and a three-layer slab with c(2×2) structure are used to model the perfect Cu(100) surface. Three possible adsorption sites,top, bridge and hollow site, were considered in the calculations. The predicted results show that the hollow site is the prefer site for atomic oxygen adsorbed on Cu(100) surface energetically. This is in good agreement with the experiment. The calculated binding energies are respective 2.014, 3.154 and 3.942 eV for top, bridge and hollow sites at mPW1PW91/LanL2dz level for the cluster model. The geometry of Cu(100) surface has also been optimized theoretically with various density functional methods and the results show that the prediction from the B3PW91/LanL2dz and mPW1PW91/LanL2dz reproduce the experimental observation.The frontier molecular orbitals and partial density of states analysis show that the electron transfer from the d orbital of substrate to the p orbital of the surface oxygen atom.     

纳米羟基磷灰石制备及其对溶液中苯酚吸附的优化设计

采用化学沉淀法制备得到纳米羟基磷灰石(n-HAp)粉体,研究了n-HAp粉体对水溶液中苯酚的吸附性能,并初步探讨了其在粉体上的吸附机理,在低浓度(5~30mg/L)时的吸附符合Freundlich等温吸附模型。实验结果表明,n-HAp粉体对苯酚具有较好的吸附效果,2h可基本达到吸附平衡。利用正交设计实验探讨了粉体煅烧温度、吸附温度、吸附时间、溶液pH等因素对吸附效果的影响。正交实验结果统计分析表明,各种因素对吸附的影响程度依次为:溶液pH>煅烧温度>振荡温度>振荡时间。pH对吸附性能的影响最明显,强酸和强碱环境能有效提高n-HAp对苯酚的吸附量。     

甲醇在氧化锌表面吸附的研究

摘要用原位红外和脉冲实验研究了甲醇在氧化锌表面的吸附行为. FTIR结果表明, 甲醇吸附于氧化锌上易生成甲氧基, 且其生成量随着吸附温度的提高而增加. 进一步的研究结果表明, 甲氧基是由甲醇同氧化锌表面的羟基反应生成的, 将其暴露于水蒸汽中后很快消失. 脉冲实验发现, 氧化锌上脉冲甲醇时产生水, 再脉冲水则产生甲醇. 因此甲醇在氧化锌表面吸附生成甲氧基和水的反应是可逆的.     

污泥生物淋滤过程中黄铁矾对重金属离子的吸附与共沉淀作用的模拟研究

生物淋滤处理可加速污泥中重金属(Zn,Cu和Cr)的溶出。但在淋滤后期,约有31%的已溶出的Cu2+被重新固持。并且,Cu2+浓度的再次下降与Fe3+沉淀形成黄铁矾的反应在时间上具有同步性。为阐明Cu2+固持机理,文章利用氧化亚铁硫杆菌的生物催化氧化作用,模拟生物淋滤环境在纯体系合成了黄铁矾。吸附试验表明,在pH 2.0～2.5的范围内(污泥生物淋滤过程中重金属溶出范围),黄铁矾对10 mg·L-1 Cu2+(该浓度与供试污泥生物淋滤中的Cu2+浓度相近)的吸附率低于9%,不能完全解释Cu2+的重新固持现象。共沉淀试验表明,Cu容易与黄铁矾形成共沉淀而掺入矿物的晶格。当Cu2+为10 mg·L-1时,约有44.6%的Cu2+与黄铁矾产生共沉淀而进入固相。可以认为,Cu与黄铁矾的共沉淀效应,是导致污泥生物淋滤后期Cu2+浓度再次下降的主要原因,黄铁矾对Cu2+的吸附只起极小的作用。     

密度泛函理论研究MN@H_2O (M=Ga,Ge, In,Sn, Sb; N=M,Al)团簇的特性

采用密度泛函理论的B3LYP, B3P86, B1B95, P3PW91和PBE1PBE方法结合SDD, LANL2DZ和CEP-121G基组计算了d~(10)组态二聚物MN(M=Ga, Ge, In, Sn和Sb; N=M和Al)的几何结构.采用B3P86/SDD进一步研究了MN@H_2O团簇的几何结构及吸附能.结果表明,水分子结合在二聚物M_2上时,对二聚物影响较大,对水分子自身影响较小.将M_2中Ga, Ge, In, Sn或Sb替换一个原子为Al时,水分子在GeAl和SnAl上的吸附能变化较大,而在GaAl, InAl和SbAl上吸附能变化较小.另外, H_2O吸附在Ga, Ge, In, Sn和Sb上时,与吸附在Al上时,吸附能的变化不大.