Removal of emerging contaminants of concern by alternative adsorbents

The effective removal of emerging contaminants of concern (ECCs) such as endocrine-disrupting chemicals, pharmaceutically active compounds, personal care products, and flame retardants is a desirable water treatment goal. In this study, one activated carbon, one carbonaceous resin, and two high-silica zeolites were studied to evaluate their effectiveness for the removal of an ECC mixture from lake water. Adsorption isotherm experiments were performed with a mixture of 28 ECCs at environmentally relevant concentrations (200–900 ng/L). Among the tested adsorbents, activated carbon was the most effective, and activated carbon doses typically used for taste and odor control in drinking water (<10 mg/L) were sufficient to achieve a 2-log removal for most of the tested ECCs. The carbonaceous resin was less effective than the activated carbon because this adsorbent had a smaller volume of pores in the size range required for the adsorption of many ECCs (6–9 Å). For the removal of ECC mixture constituents, zeolites were less effective than the carbonaceous adsorbents. Because zeolites contain pores of uniform size and shape, a few of the tested ECCs with matching pore size/shape requirements were well removed, but the adsorptive removal of others was negligible, even at zeolite doses of 100 mg/L. The results of this study demonstrate that effective adsorbents for the removal of a broad spectrum of ECCs from water should exhibit heterogeneity in pore size and shape and a large pore volume in the 6–9 Å size range.     

Dauerhaftigkeitspotentiale selbstverdichtender Betone

The Potential Durability of Self‐Compacting Concrete Owing to its exceptional fresh concrete properties, the use of self‐compacting concrete SCC offers numerous technological and economical advantages. However, during the planning of constructions the question arises as to whether the special composition of SCC affects durability. Thus the potential durability of different SCC compositions was investigated systematically at the Centre for Building Materials (cbm) of the Technical University of Munich. In a first series of tests, attention was focused on the effect of the powder fraction and viscosity agents often used in SCC on durability. In addition, the effect of the special composition of SCC on the susceptibility to damaging alkali silica‐reactions ASR was investigated. The effectiveness of fly ash as a secondary cementitious material in avoiding damaging ASR when using reactive aggregate was clarified.     

Study of the catalytic combustion of lean hydrogen-air mixtures in a monolith reactor

This paper presents an experimental study of catalytic hydrogen combustion that used commercial catalysts containing Pt in a honeycomb monolith reactor in a plug flow configuration. The emphasis is on determining global kinetics in the case of low hydrogen content. Measurements of the temperature and composition of the reaction product at the outlet in the steady state condition at the different initial compositions of hydrogen and total volumetric feed rates were performed. The conversion of hydrogen was determined in parallel to the composition of the reaction product at the outlet using GC as well as by means of the thermodynamic approach using material and energy balances. The influence of the flow rate and initial molar fraction of hydrogen on hydrogen conversion is shown. A kinetic expression of the Arrhenius type is proposed with the reaction first order in hydrogen and zero order in oxygen for the overall process of the oxidation of hydrogen in lean hydrogen-air mixtures. The determined activation energy was in good agreement with the desorption activation energy for O₂ from graphene-covered Pt(111) surfaces using temperature-programmed desorption. This result shows transport-limitations for heterogeneous hydrogen conversion in catalytic hydrogen combustion.     

Intercomparison exercise of high pressure gas flow test facilities within GERG

Ten of the main European gas Companies decided to carry out the second intercomparison exercise of high pressure test facilities within GERG (Groupe Européen de Recherches Gazières). The survey has compared the performances of 8 high pressure gas flow laboratories in the period autumn 1998–autumn 1999.

The aim was to check to what extent results obtained at the various laboratories are comparable and to reveal possible ways of improving the performances. Tests have been carried out using three transfer standard packages of three different diameters. The considered performance parameters have been: (1) agreement of results between laboratories, (2) short term stability and (3) day to day reproducibility of the reference flow.

The following main conclusions have been drawn:

• The majority of the laboratories involved in the intercomparison produced very accurate results. Despite the involvement of five independent traceability chains, 92.5% of the test results are within a band of ±0.25%.

• For most facilities the short term fluctuations are of the order of ±0.1%. Individual facilities may perform even better.

• This exercise allowed us to confirm the good results of the previous campaign and to identify some items to improve future intercomparisons.

Impact of the Solvation State of Lead Iodide on Its Two‐Step Conversion to MAPbI3: An In Situ Investigation

Producing high efficiency solar cells without high‐temperature processing or use of additives still remains a challenge with the two‐step process. Here, the solution processing of MAPbI₃ from PbI₂ films in N,N‐dimethylformamide (DMF) is investigated. In‐situ grazing incidence wide‐angle X‐ray scattering (GIWAXS) measurements reveal a sol–gel process involving three PbI₂‐DMF solvate complexes—disordered (P₀) and ordered (P₁, P₂)—prior to PbI₂ formation. When the appropriate solvated state of PbI₂ is exposed to MAI (methylammonium Iodide), it can lead to rapid and complete room temperature conversion into MAPbI₃ with higher quality films and improved solar cell performance. Complementary in‐situ optical reflectance, absorbance, and quartz crystal microbalance with dissipation (QCM‐D) measurements show that dry PbI₂ can take up only one third of the MAI taken up by the solvated‐crystalline P₂ phase of PbI₂, requiring additional annealing and yet still underperforming. The perovskite solar cells fabricated from the ordered P₂ precursor show higher power conversion efficiency (PCE) and reproducibility than devices fabricated from other cases. The average PCE of the solar cells is greatly improved from 13.2(±0.53)% (from annealed PbI₂) to 15.7(±0.35)% (from P₂) reaching up to 16.2%. This work demonstrates the importance of controlling the solvation of PbI₂ as an effective strategy for the growth of high‐quality perovskite films and their application in high efficiency and reproducible solar cells.     

Room‐Temperature Partial Conversion of α‐FAPbI3 Perovskite Phase via PbI2 Solvation Enables High‐Performance Solar Cells

The two‐step conversion process consisting of metal halide deposition followed by conversion to hybrid perovskite has been successfully applied toward producing high‐quality solar cells of the archetypal MAPbI₃ hybrid perovskite, but the conversion of other halide perovskites, such as the lower bandgap FAPbI₃, is more challenging and tends to be hampered by the formation of hexagonal nonperovskite polymorph of FAPbI₃, requiring Cs addition and/or extensive thermal annealing. Here, an efficient room‐temperature conversion route of PbI₂ into the α‐FAPbI₃ perovskite phase without the use of cesium is demonstrated. Using in situ grazing incidence wide‐angle X‐ray scattering (GIWAXS) and quartz crystal microbalance with dissipation (QCM‐D), the conversion behaviors of the PbI₂ precursor from its different states are compared. α‐FAPbI₃ forms spontaneously and efficiently at room temperature from P₂ (ordered solvated polymorphs with DMF) without hexagonal phase formation and leads to complete conversion after thermal annealing. The average power conversion efficiency (PCE) of the fabricated solar cells is greatly improved from 16.0(±0.32)% (conversion from annealed PbI₂) to 17.23(±0.28)% (from solvated PbI₂) with a champion device PCE > 18% due to reduction of carrier recombination rate. This work provides new design rules toward the room‐temperature phase transformation and processing of hybrid perovskite films based on FA⁺ cation without the need for Cs⁺ or mixed halide formulation.     

Hydrothermische Behandlung von Stärke in Gegenwart von Maltosesirup. Teil 1. Einfluß auf DSC-Parameter und die Konsistenz von Kartoffelstärkegelen

Hydrothermal treatment of starch in presence of maltose syrup. Part 1. Effect on DSC Parameters and consistency of potato starch gels A hydrothermal modification of potato starch at water excess in presence of maltose syrup permits distinct changes of properties as paste consistency, gelatinization and gelation behaviour preserving the granular structure at the same time. Annealing in maltose syrup causes a drastic decrease in hot past consistency and an increase in consistency during the keeping phase at 96°C. 3.3% starch in pastes of such samples produces a set back of about 2300 BU at a Brabender final temperature of 50°C. Annealing of potato starch in maltose syrup doubles Brabender final consistency with minimal loss in yield (< 10%). Modified patterns show a gel elasticity of about 20%-sag measured in ridgelimeter. Gel bevels composed of 3.3% annealed starch modified in 6%ical maltose syrup up to a final temperature of 56°C are characterized by sag values of 17%. The alkaline stability measured in Brabender viscograph rises 4 fold in these samples and show a shift of the DSC swelling temperature T_max of 5.5 to 8 K. Annealing of potato starch in maltose syrup makes it possible to alter properties within a short time at very low energy consumption offering broad industrial application.     

Hydrothermische Behandlung von Stärke in Gegenwart von α-Amylase. Teil 3. Veränderung der rheologischen Eigenschaften von Weizenstärke durch hydrothermisch-enzymatische Behandlung

Hydrothermal Treatment of Starch in Presence of α-Amylase. Part 3: Changes of Rheological Properties of Wheat Starch by Hydrothermal Enzymatic Treatment . In order to change functional properties of wheat starch the feasibility for a hydrothermal enzymatic modification under conditions of excess water (annealing) has been tested. The granular structure of the starch should remain unchanged at the same time. Since wheat starch may be changed negligiblely at usual conditions of annealing (T=50°C) as a consequence of its rather low swelling temperature a bacterial α-amylase has been used for partial degradation of these portions of starch granules which gelatinize irreversiblely at higher levels of annealing temperatures. The resulting spectrum of saccharides consisting mainly of maltose (approx. 50%) allows the protection of the wheat starch matrix even at higher annealing temperatures (54°C). However, the gelatinization and gelation behaviour is changed in a characteristic way, in particular by a serious increase of the hot paste consistency at 95°C. In the following, the obtained consistency collapses significantly and arrives by cooling a level below the corresponding figures of the native starch. With respect to yield of annealed starch the reaction time at elevated temperature is of main importance. In order to demonstrate the protecting activity of the produced saccharides in particular with higher concentrations of maltose samples have been annealed in maltose sirups of varied concentration (6, 12, 25%m/m). Up to concentrations of 12%m/m and reaction temperatures of 50°C the Brabender consistency curves could be raised by 300 to 500BU. The application of 54°C limited the effect of modification. Using a 25%m/m maltose syrup allowed, of course, successfully the annealing at 54°C. As expected, yield losses remained low (< 10%). In applying a temperature-time-regime by steps together with a treatment by α-Amylase or alternatively 25%m/m maltose syrup the expected shifting of consistency curves could be observed as well, however, to a limited amount. Finally, pronounced differences could be found for the yield of modified starches.