水处理纳米材料的制备、性能及应用研究

工业的高速发展使地球上有限的水资源受到日益严重的污染，去除水中的有毒、有害化学物质已成为环保领域的一项重要工作。纳米材料与技术的开发应用为实现高效、低成本的水处理开辟了新的途径。 本课题组开发的纳米-亚纳米功能新材料（生态宝）可用作养殖生态环境改良剂，它对“三氮”、硫化物、CODCr、BOD5、重金属等有害物质具有很好的去除能力。生态宝用于养殖幼参，有显著的促生长、增加成活率的作用。生态宝用于养殖对虾，对虾体内重金属含量有明显降低。 以粉末状P25型纳米TiO2为光催化剂，系统的研究了它对染料AB80的光催化降解。在紫外光照射下，光催化反应75min，染料AB80溶液完全脱色，光催化反应135min，染料溶液完全矿化；AB80的光催化脱色反应遵从准一级反应动力学；催化剂的最佳剂量为1.0g/L。AB80在TiO2颗粒表面的吸附符合Langmuir方程式，随着pH值的增加吸附量迅速减少；pH值在反应中起着重要的作用，碱性溶液中的反应速度比酸性溶液的大，pH=10.0初始反应速度最大；电子捕获剂（H2O2）的加入能够显著的提高反应速率，H2O2浓度为5mmol/L时，反应速度变为原来的2.78倍。 以硅藻土为载体，采用溶胶-凝胶法制备了负载型的纳米TiO2，SEM分析结果表明，TiO2的包覆量对负载光催化剂的形貌有很大影响，TiO2包覆量较低(14.5%)的复合物无团聚现象发生。XRD分析结果表明，所制备的TiO2为锐钛矿和金红石混晶型，平均粒径11nm。FT-IR分析结果表明，TiO2和硅藻土之间没有生成化学键。以染料AB80和B-2BF为模型污染物，利用制备的光催化剂复合物进行了吸附-光催化试验，结果表明，TiO2包覆量为14.5%的复合物具有较高的吸附-光催化活性，对模型污染物的降解效果好于德国Degussa公司的商品纳米P25-TiO2。溶液pH对TiO2/硅藻土复合物光催化活性影响很大，弱酸性条件有利于反应的进行。TiO2/硅藻土对实际印染废水有较好的降解效果，试验条件下，废水光催化反应3.5h，色度去除率为100%。研究了液固多相光催化反应的催化剂失活原因及再生手段，提出TiO2/硅藻土复合物再生的方法为酸洗和高温烧结。对于模拟印染废水来说，光催化剂重复使用对光催化活性几乎没有影响，重复使用15次后，催化活性仅降低了12%。而对实际印染废水来说，重复使用对光催化活性有影响，光催化剂复合物重复使用7次后，催化活性降低了41%。TiO2/硅藻土复合光催化剂成本低，简便易行，光催化效果好，有望在环境污染物治理中得到广泛的应用。 采用CuCl水解法制得了硅藻土负载的纳米Cu2O，并利用XRD、SEM等手段对其进行表征。研究了负载的纳米Cu2O对B-2BF和AB80染料废水的光催化降解，发现纳米Cu2O经过负载后，团聚减少，分散性好，对染料废水的光催化降解效率成倍增长。纳米Cu2O包覆量为31.3%的光催化剂复合物光催化活性最好，其光催化效率是纯的Cu2O的6倍。负载的纳米Cu2O可以有效的利用太阳光进行光催化反应，而且太阳光下纳米Cu2O的光催化活性比纳米TiO2的强。太阳能是取之不尽、用之不竭的清洁能源，利用太阳能来处理染料废水成本低、无污染，是一种非常有发展前景的环境治理新技术。pH 5-pH 7是负载纳米Cu2O光催化降解B-2BF的最佳反应范围。负载的纳米Cu2O光催化剂有较好的稳定性，重复使用8次以后，其脱色率仍能达到75%以上。

Photocatalytic degradation of CI Acid Blue 80 in aqueous suspensions of titanium dioxide under sunlight

The dye C.I. Acid Blue 80 (AB80) was easily degraded by TiO2-P25 assisted photocatalysis in aqueous dispersion under irradiation of sunlight. The optimal reaction conditions were [TiO2] = 2.0 g/L, pH = 10, [H2O2] = 5 mmol/L. The photocatalytic reaction followed pseudo-first order kinetics. The adsorption of AB80 onto TiO2 was in accord with Langmuir equation.

A Molecular Dynamics Study of the Early Stages of Calcium Carbonate Growth

The precipitation of calcium carbonate in water has been examined using a combination of molecular dynamics and umbrella sampling. During 20 ns molecular dynamics trajectories at elevated calcium carbonate concentrations, amorphous particles are observed to form and appear to be composed of misaligned domains of vaterite and aragonite. The addition of further calcium ions to these clusters is found to be energetically favorable and virtually barrierless. By contrast, there is a large barrier to the addition of calcium to small calcite crystals. Thus, even though calcite nanocrystals are stable in solution, at high supersaturations, particles of amorphous material form because this material grows much faster than ordered calcite nanocrystals.

Edge-preserving self-healing: Keeping network backbones densely connected

Healing algorithms play a crucial part in distributed peer-to-peer networks where failures occur continuously and frequently. Whereas there are approaches for robustness that rely largely on built-in redundancy, we adopt a responsive approach that is more akin to that of biological networks e.g. the brain. The general goal of self-healing distributed graphs is to maintain certain network properties while recovering from failure quickly and making bounded alterations locally. Several self-healing algorithms have been suggested in the recent literature [IPDPS'08, PODC'08, PODC'09, PODC'11]; they heal various network properties while fulfilling competing requirements such as having low degree increase while maintaining connectivity, expansion and low stretch of the network. In this work, we augment the previous algorithms by adding the notion of edge-preserving self-healing which requires the healing algorithm to not delete any edges originally present or adversarialy inserted. This reflects the cost of adding additional edges but more importantly it immediately follows that edge preservation helps maintain any subgraph induced property that is monotonic, in particular important properties such as graph and subgraph densities. Density is an important network property and in certain distributed networks, maintaining it preserves high connectivity among certain subgraphs and backbones. We introduce a general model of self-healing, and introduce xheal+, an edge-preserving version of xheal[PODC'11]. © 2012 IEEE.

Human Parechovirus Infection in Neonatal Intensive Care

Background: Approximately 5-6% of all infective episodes in NICU are of viral origin. Previous studies suggest that human parechovirus (HPeV) infection presents most commonly in term infants, as a sepsis-like syndrome in which meningoencephalitis is prominent. Our aim was to study the infection rate and associated features of HPeV.

Methods: Blood samples were taken from NICU babies greater than 48 hours old, who were being investigated for late onset sepsis. Clinical and laboratory data were collected at the time of the suspected sepsis episode. Samples were tested using universal primers and probe directed at the 5'-untranslated region of the HPeV genome by reverse transcriptase PCR. Results were confirmed by electrophoresis and DNA sequencing.

Results: HPeV was detected in 11 of 84 samples (13%). These infants had a mean (interquartile range, IQR) gestational age of 28.9 (26.9 - 30.6) weeks and mean birth weight of 1.26 (SD = 0.72) kg. The median day of presentation was 16 (IQR: 11-27). These characteristics were similar to the infants without positive viral detection. Six infants presented with respiratory signs. One infant presented with signs of meningitis. Six of the 11 episodes of HPeV infection occurred during the winter months (December - February). No HPeV positive infants had abnormal findings on their 28-day cranial ultrasound examination.

Conclusions: We found a HPeV infection rate of 13% in infants being tested for late onset sepsis. HPeV should be considered as a possible cause of sepsis-like symptoms in preterm infants.