Untersuchungen zur Betriebscharakteristik pulsierter Füllkörperkolonnen für die Flüssig/Flüssig-Extraktion

Studies on the operating characteristics of pulsed packed-columns for liquid/liquid extraction. The dependence of capacity limit and extraction efficiency on the operating conditions, the properties, and the packing material is illustrated with the aid of experiments on two test mixtures in pilot plant columns. The direction of mass transfer has a large influence on the capacity limit and extraction efficiency. From the practical point of view, the operating characteristics of pulsed packed-columns provide the chemical engineer with reference data for the estimation of column dimensions and rational planning of pilot plant experiments. Methods for the precalculation of capacity limits and extraction efficiencies of pulsed packed-columns are reported in the literature. A comparison of the results obtained by these methods with the experimental data indicates the feasibilities and limits of such a calculation.     

Lipoprotein lipase in cholesterol-fed and control guinea pigs

A study of the in vitro activity of lipoprotein lipase of guinea pigs has shown that (a) the lipolytic activity of activated post-heparin serum is depressed in hypercholesteremic guinea pigs compared to the serum of normocholesteremic guinea pigs; and (b) this depressed lipolytic activity in hypercholesteremic guinea pigs is not due to the presence of an inhibitor.     

Polyaluminum chloride with high Al30 content as removal agent for arsenic-contaminated well water

Polyaluminum chloride (PACl) is a well-established coagulant in water treatment with high removal efficiency for arsenic. A high content of Al₃₀ nanoclusters in PACl improves the removal efficiency over broader dosage and pH range. In this study we tested PACl with 75% Al₃₀ nanoclusters (PACl_Al30) for the treatment of arsenic-contaminated well water by laboratory batch experiments and field application in the geothermal area of Chalkidiki, Greece, and in the Pannonian Basin, Romania. The treatment efficiency was studied as a function of dosage and the nanoclusters’ protonation degree. Acid-base titration revealed increasing deprotonation of PACl_Al30 from pH 4.7 to the point of zero charge at pH 6.7. The most efficient removal of As(III) and As(V) coincided with optimal aggregation of the Al nanoclusters at pH 7-8, a common pH range for groundwater. The application of PACl_Al30 with an Al_tot concentration of 1-5 mM in laboratory batch experiments successfully lowered dissolved As(V) concentrations from 20 to 230 μg/L to less than 5 μg/L. Field tests confirmed laboratory results, and showed that the WHO threshold value of 10 μg/L was only slightly exceeded (10.8 μg/L) at initial concentrations as high as 2300 μg/L As(V). However, As(III) removal was less efficient (<40%), therefore oxidation will be crucial before coagulation with PACl_Al30. The presence of silica in the well water improved As(III) removal by typically 10%. This study revealed that the Al₃₀ nanoclusters are most efficient for the removal of As(V) from water resources at near-neutral pH.     

Experimental monitoring of chloride-induced reinforcement corrosion and chloride contamination in concrete with ground-penetrating radar

In this article, we present a laboratory experiment to monitor the accelerated corrosion in concrete using ground-penetrating radar (GPR). Four concrete test specimens were cast with rebars of different size and placed at different depths. The lifetime decades of reinforcement corrosion process were accelerated into 18 days by using the impress current technique. The electrochemical corrosion process was periodically monitored with GPR. Two control specimens were also prepared to investigate the influence of chloride contamination on GPR signal. The measured data were analysed both in time and frequency domains. In time domain, the peak-to-peak amplitude of a wave reflected by a rebar was calculated to investigate the relationship between an increase in signal amplitude and the degree of corrosion. In frequency domain, the time–frequency representations of the signal were computed by using S-transform. The results show that reinforce corrosion increased the amplitude of reflected signal in time domain but did not change the peak frequency in frequency domain while chloride contamination attenuates the signal to smaller amplitude and lower peak frequency. Based on the results, a novel process is finally proposed for GPR-based corrosion detection.     

Non-destructive detection of surface-bond defects in carbon composite-strengthened concrete structures

For almost 15 years, carbon fibre-reinforced polymer (CFRP) plates and sheets have been used for strengthening and repair of civil engineering structures. CFRP plates were applied to upgrade structures for change in use or increasing traffic load. CFRP laminates have also been used to repair deteriorated structures such as multi-storey parking or bridges. The execution quality and condition of the strengthening measure in terms of bond integrity were neither monitored nor tested systematically. Inspectors eventually applied simple hammer knocking during regular main inspection for subjective noise distinction as a measure for eventual insufficient bond. This paper presents the feasibility and the limitations of low-frequency transversal ultrasonic waves with dry-coupling point-contact sensors for inspection and defect detection between CFRP laminate and concrete surfaces. The German Centre of Competence in Civil Engineering (DIBt) has initiated a national research project [Helmerich et al. (2012). Condition analysis of bonded CFRP-applications on concrete structures by means of non-destructive testing [in German: Zustandsuntersuchung von CFK-Klebeverstärkungen an Betonbauteilen mittels zerstörungsfreier Prüfung (ZfP)]. Final, internal project report], carried out at the Federal Institute for Materials Research and Testing (BAM), Germany. The aim of the project was to present a potential non-destructive testing method for bond defect detection as a measure for the durability of the strengthening system more than 10 years after application.     

Die neue DAfStb‐Richtlinie “Vorbeugende Maßnahmen gegen schädigende Alkalireaktion im Beton”

The new DAfStb‐Guideline “Preventive Measures against detrimental Alkali‐Reaction in Concrete (Alkali‐Guideline)” In 2002 the German Committee for Structural Concrete decided to revise the Alkali‐Guideline. The motivation for the revision may be summarised as follows: – further developments in the german concrete technology – damage cases in concrete pavements – development of new rapid test methods – further specification of alkali reactive aggregates The contribution gives a detailed overview of the main amendments in the new Guideline and illustrates the background behind the key regulations.     

Eine Untersuchung zum Einfluss voll verfilterter Messstellen auf die Grundwasserbeschaffenheit

Advantages and disadvantages of fully screened and depth-orientated observation wells in porous aquifers are diversely evaluated in hydrogeological practice. Although guidelines refer to the risk of groundwater mixing downstream of fully screened wells, installation of fully screened wells continues. This paper includes an overview of guidelines for selection of suitable observation wells as well as results from an investigation on the impact of fully screened wells in two observation well installations. These results indicate that, after filling the fully screened wells, the measured groundwater quality changed drastically. The mean nitrate concentrations in the upper layer of the aquifer decreased from 90 to 14 mg/L within six weeks. Building new fully screened wells in porous aquifers is discouraged if vertical flow in the wells cannot be excluded.