The grafting of isoprene onto poly(propylene oxide)

The grafting of isoprene as well as a comonomer mixture of isoprene and acrylonitrile onto a backbone of high molecular weight poly(propylene oxide) with tertiary-butyl peroctoate gave a gumstock which is sulfur curable to a product having interesting elastomeric properties.     

乙炔加氢制乙烯高选择性催化剂的研究

研究了乙炔加氢制乙烯Pd/Al_2O_3催化剂钯含量及助剂与起始反应温度及反应温度、加氢活性和选择性之间的关系.在此基础上研制出高选择性(≥98%)的CHC-1型催化剂.500h连续实验结果表明:其活性、选择性均稳定.     

Sampling of French local networks and applications

In this paper the authors describe a study in progress by which it is intended to represent all the French local telephone networks by just a small number of typical cases. The objectives are firstly, to gain a better knowledge of the existing network and secondly, to be able to compare equipment policies by simulating the evolution of the sample networks. The representative areas were chosen by original data analysis methods (principal component analysis followed by classification and choice of samples). Detailed data appertaining to the sample areas were then collected. They give examples of overall statistical results extrapolated at national level and discuss the corresponding applications. Lastly, they consider further developments of the study.     

Dendritic anion hosts: perchlorate uptake by G5-NH2 poly(propyleneimine) dendrimer in water and model electrolyte solutions

Perchlorate (ClO4-) has emerged as a major groundwater and surface water contaminant in the United States. Ion exchange (IX) is the most widely used technology for treating water containing lower concentrations of perchlorate (<100 ppb). However, a major drawback of IX is the need for frequent regeneration or disposal of the perchlorate-laden resins. As a first step toward the development of high-capacity, selective and recyclable dendritic ligandsforthe recovery of perchloratefrom aqueous solutions by dendrimer filtration, we tested the hypothesis that dendrimers with hydrophobic cavities and positively charged internal groups should selectively bind ClO4- over more hydrophilic anions such as Cl-, NO3-, SO4(2-), and HCO3-. We measured the uptake of ClO4- by the fifth generation (G5-NH2) poly(propyleneimine) (PPI) dendrimer with a diaminobutane core and terminal NH2 groups in deonized water and model electrolyte solutions as a function of (i) anion-dendrimer loading, (ii) solution pH, (iii) background electrolyte concentration, and (iv) reaction time. The ClO4- binding capacity of this dendrimer is comparable to those of perchlorate-selective IX resins. However, its ClO4- binding kinetics is faster and reaches equilibrium in approximately 1 h. Note also that only a high pH (approximately 9.0) aqueous solution is needed to release more than 90% of the bound ClO4- anions by deprotonation of the dendrimer tertiary amine groups. The overall results of this study suggest that dendritic macromolecules such as the G5-PPI NH2 dendrimer provide ideal building blocks for the development of high-capacity, selective and recyclable ligands for the recovery of anions such as perchlorate from aqueous solutions by dendrimer enhanced filtration.     

Dendrimer enhanced ultrafiltration. 1. Recovery of Cu(II) from aqueous solutions using PAMAM dendrimers with ethylene diamine core and terminal NH2 groups

This article discusses the feasibility of using dendrimer enhanced ultrafiltration (DEUF)to recover Cu(II) from aqueous solutions. Building upon the results of fundamental investigations of Cu(II) binding to PAMAM dendrimers with ethylenediamine (EDA) core and terminal NH2 groups, we combine (i) dead-end ultrafiltration (UF) experiments with (ii) atomic force microscopy (AFM) characterization of membrane fouling to assess the feasibility of using DEUF to recover Cu(II) from aqueous solutions. On a mass basis, the Cu(II) binding capacities of the EDA core PAMAM dendrimers are much larger and more sensitive to solution pH than those of linear polymers with amine groups. The dendrimer-Cu(II) complexes can be efficiently separated from aqueous solutions by ultrafiltration. The metal ion laden dendrimers can be regenerated by decreasing the solution pH to 4.0; thus enabling the recovery of the bound Cu(II) ions and recycling of the dendrimers. The UF measurements and AFM characterization studies show that EDA core PAMAM dendrimers with terminal NH2 groups have very lowtendency to foul the commercially available regenerated cellulose (RC) membranes evaluated in this study. The overall results of these experiments suggest that DEUF is a promising process for recovering metal ions such as Cu(II) from aqueous solutions.     

Suitability of bentonite-paste tailings mixtures as engineering barrier material for mine waste containment facilities

This study investigates the feasibility of using bentonite-paste tailings (BPT) as a barrier (liner, cover) material for mine waste containment facilities. Improvements of the hydraulic properties are realized by using compaction to densify the paste tailings in the first stage and mixing an additive-like natural bentonite to paste tailings to further reduce the voids that control hydraulic conductivity in the second stage. A significant decrease in hydraulic conductivity is observed with these transformations. Values that are as low as 1 × 10^?9 and 4 × 10^?9 cm/s are obtained in 8% and 4% bentonite and BPT, respectively. Based on these satisfactory values, additional investigations are conducted to evaluate the freeze–thaw and wet–drying performance of BPT up to 5 and 6 cycles, respectively. The results show that negligible to acceptable changes in hydraulic conductivity occur. None of the changes reach one order of magnitude. As a final step, a cost analysis is undertaken to evaluate the economical benefits that can be obtained from such new material. When compared to conventional compacted clay–bentonite barrier or sand–bentonite with 12% bentonite concentration, it is found that the 4% BPT is less expensive by 66%. The results place this recycled BPT material as a promising candidate for barrier design while reducing the amount of waste to be managed and the cost of surface tailings management.