PTFE超滤膜对水中三种典型天然有机物的去除及其膜污染机制

研究聚四氟乙烯(PTFE)超滤膜对水中天然有机物的去除效果以及膜污染机制。天然有机物是膜污染中的主要污染物,其中腐植酸(HA)、海藻酸钠(SA)和牛血清蛋白(BSA)为典型的代表。过滤试验采用序批式,配制特定浓度的天然有机物水样进行死端过滤。通过采用紫外分光光度计和TOC-L仪测定水样的UV和总有机碳的值来评估PTFE对三种天然有机物的去除效果,同时采用扫描电子显微镜(SEM)对污染后的膜表面进行观察以推断其污染机制。此外,在HA原料液中添加钙离子(Ca^(2+))和鸡蛋白溶菌酶(LYS,带正电)进行过滤试验,探究PTFE对带不同电荷有机物的去除效果和超滤膜的污染机制。PTFE超滤膜对三种典型的天然有机物去除率以及膜污染情况不尽相同,对HA和SA的去除率远高于BSA,而对HA的去除率稍高于SA。HA和SA对PTFE的膜污染机制是先膜孔阻塞而后形成滤饼层,BSA则为膜孔吸附。PTFE对LYS的去除率几乎为零,但混合了HA和Ca^(2+)后的去除率显著升高,加入Ca^(2+)升高更明显,原因是Ca^(2+)与LYS不但有静电吸附作用,还有架桥作用,形成了更致密的滤饼层。

无人机跟踪过程中的避障问题研究

针对单架无人机跟踪单一目标问题,提出Lyapunov矢量场法和速度障碍法相结合的方法,保证UAV在执行跟踪任务时的安全。首先,建立无人机运动模型,通过基于Lyapunov矢量场法的航向控制使无人机能够收敛到极限环;其次,利用速度障碍法原理判断无人机与障碍物之间是否存在飞行冲突,推导出避障所需的航向控制量;最后,针对障碍物重叠情况,利用几何关系将重叠区域合并,再求解出航向控制量,完成对重叠威胁区域的避障。仿真结果表明,所提算法在单一障碍物和多障碍物的条件下,都能有效地跟踪目标并实现避障。

Hydrous manganese dioxide adsorbing humic acid： controlling trihalomethane formation

Effectiveness of hydrous manganese dioxide （δMnO2） adsorbing humic acid under different conditions and its subsequent effects on trihalomethane （THMs） formation have been studied. Humicacid removal increases with higher pH and residual TOC decreases from 3.63 mg/L to 1.68 mg/L with pH increasing from 5.5 to 8.5 at 3.0 mg/L δMnO2; δMnO2 exhibits good potential of removing humic acid and the adsorbing potential as high as 1 mg TOC/mg δMnO2 is achieved; the fractional reduction of humic acid with higher molecular weight is about 30% higher than that with lower molecular weight. δMnO2 adsorption obviously reduces subsequent THMs formation; more significant THMs formation reduction is observed for humic acid with higher molecular weight. δMnO2 adsorption is an important factor that contributes to humic acid removal and THMs formation reduction in permanganate pre-oxidation process.

The oxidative and adsorptive effectiveness of hydrous manganese dioxide for arsenite removal

This study focuses on the effectiveness of hydrous manganese dioxides （ζMnO2） removing arsenite （As（Ⅲ）） from aqueous solution. Effects of such factors as permanganate oxidation, pH, humic acid and Ca^2＋ on As removal and possible mechanisms involved in have been investigated. Permanganate oxidation increases As removal to a certain extent; the higher pH results in the formation of more easily adsorbed As species, contributing to higher As removal; hmnic acid occupies adsorbing sites and decreases ζ potential of ζMnO2, therefore inhibiting As removal; Ca^2＋ facilitates As adsorption on ζMnO2, mainly through increasing ζ potential and decreasing repulsive forces between As and surface sites.ζMnO2 exhibits oxidative and adsorptive potential for As（Ⅲ）, and may be employed as adsorbents or filter coating for As removal in water treatment process.