Natural versus wastewater derived dissolved organic carbon: implications for the environmental fate of organic micropollutants

The interaction of organic micropollutants with dissolved organic carbon (DOC) can influence their transport, degradation and bioavailability. While this has been well established for natural organic carbon, very little is known regarding the influence of DOC on the fate of micropollutants during wastewater treatment and water recycling. Dissolved organic carbon-water partition coefficients (K_DOC) for wastewater derived and reference DOC were measured for a range of micropollutants using a depletion method with polydimethylsiloxane disks. For micropollutants with an octanol-water partition coefficient (log K_OW) greater than 4 there was a significant difference in K_DOC between reference and wastewater derived DOC, with partitioning to wastewater derived DOC over 1000 times lower for the most hydrophobic micropollutants. The interaction of nonylphenol with wastewater derived DOC from different stages of a wastewater and advanced water treatment train was studied, but little difference in K_DOC was observed. Organic carbon characterisation revealed that reference and wastewater derived DOC had very different properties due to their different origins. Consequently, the reduced sorption capacity of wastewater derived DOC may be related to their microbial origin which led to reduced aromaticity and lower molecular weight. This study suggests that for hydrophobic micropollutants (log K_OW > 4) a higher concentration of freely dissolved and thus bioavailable micropollutants is expected in the presence of wastewater derived DOC than predicted using K_DOC values quantified using reference DOC. The implication is that naturally derived DOC may not be an appropriate surrogate for wastewater derived DOC as a matrix for assessing the fate of micropollutants in engineered systems.     

Rationalisierung des Zeichnungswesens im Chemie-Apparatebau

Rationalizing drawings for chemical apparatus . For small and medium-sized manufacturers of apparatus, producing drawings may constitute a disproportionate waste of time and personnel, particularly when no new designs are involved but only modification or improvement of drawings supplied by the customer. One possibility for rationalizing drawing is to simplify the old-fashioned approach by using symbols for frequently drawn or standard items, or by listing alphanumerically. This presumes a kind of systematization permitting determination of those symbols and their reasonable use, as well facilitating rationalization by means of data processing. There are different approaches to computer-aided drawing (from computer controlled drawing-board to interactive screens); here a CAD programme is presented which was especially developed for graphic presentation of chemical apparatus, and which can be used without learning a programming language.     

A method for determination of length distributions of multiwalled carbon nanotubes before and after melt processing

A relatively simple method to determine the length distribution of carbon nanotubes (CNTs) before and after melt processing was developed. This involves the selection of a suitable solvent for dispersing pristine CNTs as well as to dissolve the matrix of melt mixed composites and the choice of an appropriate nanotube concentration. The length of suitably individualized CNTs was visualized using transmission electron microscopy and length distributions were measured using image analysis. Examples are shown for Baytubes® C150HP and Nanocyl™ NC7000 and their melt mixed composites with polycarbonate where the same procedure was applied to both, measuring the initial length distribution and the distribution after recovering from the composites. These results indicated a significant shortening after melt processing up to 30% of the initial length.     

Applying Model Predictive Control to Dividing Wall Columns

The technology of dividing wall columns can offer enormous energy savings compared to common distillation columns and configurations. The technology of model predictive control is also advantageous since such a controller minimizes the future deviation of the predicted controlled variable from the reference point. The practical application of model predictive controllers for dividing wall columns is still limited due to limited experience with high interactions among the process variables. The scope of this work is the development and analysis of a method for the design of model predictive controllers for dividing wall columns. An experimental investigation verifies the practicability of the applied approach. The methods generated are transferable to other applications. Thus, the industrial acceptance of model predictive controllers for dividing wall columns is enhanced.     

Modification of cotton fabrics with a hydrolysed organotrialkoxysilane/metal alkoxide system: multifunctionalisation and mordant dyeing

Untreated cotton fabrics and cotton samples pretreated with 1,2,3,4-butanetetracarboxylic acid were functionalised with an organotrialkoxysilane [(3-glycidyloxy)propyltrimethoxysilane] in conjunction with a metal alkoxide (aluminium isopropoxide, titanium tetraisopropoxide, or zircon tetrabutoxide). Evaluation of the physicomechanical properties revealed that the dry crease recovery angle was significantly increased in the case of aluminium isopropoxide, whereas the tensile strength and the tear strength were reduced. The application of alkyltrialkoxysilanes resulted in an enhanced contact angle. As the cotton samples were treated with hydrolysed metal alkoxides, which can function as mordants, the cotton fabrics were dyed with alizarin. The dyeing behaviour was determined from colorimetric data.     

Controlled p-doping of pigment layers by cosublimation: Basic mechanisms and implications for their use in organic photovoltaic cells

We present a systematic study on doping of vanadyl- and zinc-pathalocyanine by a fully fluorinated form of tetracyano-quinodimethane as an example of controlled doping of thin organic films by cosublimation of matrix and dopant. The films are characterized in situ by temperature dependent Seebeck and conductivity measurements. We observe a drastic increase of conductivity and a corresponding shift of the Fermi level towards the valence states with increasing dopant concentration. We thus conclude that doping has the potential of both reducing the series resistance and increasing the photovoltage of organic solar cells. As a first step to exploit this potential, we present two different ways of preparing diodes with rectification ratios in excess of 10⁴ using doped phthalocyanines. By adding an undoped interlayer between the contact and the doped layer, we have produced diodes which work already in the strict absence of oxygen and are stable in air. To increase the efficiency of charge carrier generation in photovoltaic cells, we need to use photoactive donor–acceptor-heterojunctions. We present here first examples of pn- and pin-type heterojunctions combining p-doped and nominally undoped layers.     

Sintering behavior,microstructure and thermoelectric properties of calcium cobaltite thick films for transversal thermoelectric multilayer generators

The sintering behavior and the thermoelectric performance of Ca₃Co₄O₉ multilayer laminates were studied, and a multilayer thermoelectric generator was fabricated. Compacts and multilayer samples with anisotropic microstructure and residual porosity were obtained after conventional sintering at 920 °C, whereas dense and isotropic multilayer samples were prepared by firing at 1200 °C and reoxidation at 900 °C. A hot-pressed sample has a dense and anisotropic microstructure. Samples sintered at 920 °C exhibit low electrical conductivity due to the low density, whereas the Seebeck coefficient is not sensitive to preparation conditions. However, thermal conductivity of multilayers is very low, and, hence acceptable ZT values are obtained. A transversal multilayer thermoelectric generator (TMLTEG) was fabricated by stacking layers of Ca₃Co₄O₉ green tapes, AgPd conductor printing, and co-firing at 920 °C. The TMLTEG has a power output of 3 mW at ΔT = 200 K in the temperature interval of 25 °C to 300 °C.