Milan J. Schwuger

Physicochemical interactions between atrazine and clay minerals

The aim of this work was to study the sorption behaviour of atrazine on clay minerals at low environmentally relevant concentrations. Adsorption and desorption isotherms of atrazine were determined on different clay minerals using the 14C tracer technique. The adsorption isotherms are linear at pH 5.8 in the low concentration range studied. The adsorption constant Kd is proportional to the external surface in Na+ layer silicates, such as kaolinite, illite and montmorillonite. This implies that atrazine molecules do not intercalate even in swelling Na+ clay minerals. The experiments with homoionic montmorillonites (Na+, Ca2+, Ni2+, Cu2+ and Fe3+) indicate a correlation between the adsorption constant and the hydrolysis constant of the exchangeable cation. This suggests a participation of the protonated atrazine molecules in sorption due to electrostatic interactions. It is assumed that adsorption shifts the chemical equilibrium to the side of the protonated form for Men+ montmorillonites with a low hydrolysis constant of Men+. In contrast, protonation clearly dominates in Fe3+ montmorillonite because of the high hydrolysis constant of the Fe(III) ion and the adsorption isotherm obtained is not linear. The desorption isotherms show a hysteresis on all the Men+ montmorillonites examined for the time interval of 3.5 weeks. It is suggested that only that fraction of the bound atrazine, which is adsorbed due to the relatively weak physical forces, can be desorbed. The larger the fraction of protonated atrazine molecules on the surface, the less is remobilized.

Environmental specimen banking in Germany — present state and further challenges

The program of the German Environmental Specimen Bank has been expanded recently and its current status is briefly described. Selected results which have been obtained during the long term permanent operation of this project since 1985 are presented. Moreover, further aspects of environmental data evaluation and assessment are discussed.

ON THE ADSORPTION OF HYDROPHOBIC POLLUTANTS ON SURFACTANT/CLAY COMPLEXES: COMPARISON OF THE INFLUENCE OF A CATIONIC AND A NONIONIC SURFACTANT

Abstract The adsorption of the cationic surfactant dodecyl trimethyl ammonium bromide (DTAB) and of the nonionic surfactant dodecyl octaethylene glycol ether (C12E8) on four different layer silicates and their influence on the sorption processes of the fungizide biphenyl were studied. Unexpectedly, no great differences were found in comparing the adsorption of the two surfactants on the basis of physicochemical investigations, although the adsorption mechanism up to monolayer formation is fundamentally different (ion exchange and physisorption). Thus, the plateau values of the adsorption isotherms and the molar enthalpies of displacement Δ 21h are of the same order of magnitude for both surfactants and the same basal spacing by intercalation is observed in the case of swelling clays. The isotherms of the hydrophobic contaminant biphenyl are of the linear Cl-type at all layer silicates and very low adsorption takes place approximately proportionally to the BET (N2) surface area. If the surface is weakly hy...

Adsorbents from Waste materials

The possibility of using pyrolyzed wastes produced in already working incineration plants, as adsorbents for waste water treatment, was studied. Showing very poor adsorption properties, they were improved by steam activation technique used in the conventional activated carbon manufacturing. It is concluded that various organic waste materials can be converted to carbonaceous final products with a character similar to activated carbon. Their adsorption properties and pore size distribution are determined by the structure of the starting material. Although most of these samples have a low specific surface area, their pore volume is not negligible in the meso-and micropore range. Adsorption tests with model waste waters confirmed that adsorption properties are strongly influenced by the character of the suface. The adsorption capacity of these samples can be utilized for the treatment of strongly polluted industrial waste waters. Considering that the raw material ‘needed’ to manufacture these adsorbent is produced permanently and the adsorbents do not have to be regenerated, it might be worthwhile using these kinds of adsorbents in the primary treatment of industrial waste waters.

Adsorption of nitrobenzene andn-pentanol from aqueous solution on hydrophilic and hydrophobic clay minerals

The sorption of nitrobenzene andn-pentanol from dilute aqueous solution on swelling clay minerals and their organophilized derivatives (organo clays) was studied. Adsorption excess isotherms were obtained by the immersion method. The basal spacings of the clay minerals were determined by X-ray diffraction measurements. By combining these two independent methods, composition and structure of the interlamellar space could be calculated. On the hydrophilic surface of montmorillonite negative adsorption of the organic component was observed at low molar fractions of nitrobenzene or pentanol, i.e., water was preferentially adsorbed. On organophilized montmorillonite and vermiculite adsorption of nitrobenzene and pentanol was positive over the whole range of liquid composition. The amount of interlamellar alkyl chains which is determined by the surface charge of clay mineral inversely affected the adsorption of both solutes.

The Jülich environmental specimen bank

The environmental specimen bank of the Federal Republic of Germany represents the modern form of a systematically designed archive for the preservative storage of selected environmental specimens. Major aims of environmental specimen banks are: (i) retrospective identification and quantification of environmental chemicals including those not known at the time of storage; (ii) retrospective replicate analysis of samples stored under preservative conditions for the determination of inorganic elements or organic compounds already examined; and (iii) retrospective control of the success of legislative environmental protection measures in handling chemicals regarded as hazardous for man and the environment. Results of the environmental specimen bank at Jülich by the Institute of Applied Physical Chemistry, Research Centre Jülich, KFA, obtaining the initiated legislative regulations providing environmental pollution, are already proved for various compartments.

Formation of octachloroacenaphthylene in the pyrolysis of decachlorobiphenyl

Abstract The pyrolytic degradation of decachlorobiphenyl (PCB 209) in the temperature range of 700 – 1000°C and at a pyrolysis time of 10 seconds generated one main chloroaromatic product. This Compound has been identified by HPLC-UV, GC-MS, GC-FTIR and 13 C-NMR as octachloroacenaphthylene (OCAN). The mechanism of the nearly quantitative formation of octachloroacenaphthylene (OCAN) occurs via a nonachlorobenzobarrylene radical (ZIR) as an intermediate followed by a rearrangement and further dechlorination to for OCAN. Calculations with the program THERM based on the Benson-group-theory indicated that this mechanism is not possible for lower nonchlorinated biphenyls.

Surfactants and complexing agents: new tasks for specimen banking?

Surfactants and complexing agents are chemical products that are released into the environment in large amounts after being used in cleaning processes, mineral flotation, pesticide formulations, etc. Although these compounds are largely degraded during sewage treatment in industrialized countries, significant amounts will be found in sediments or sewage sludges. Furthermore, large concentrations of these compounds can be found in small rivers and brooks in the vicinity of outfalls of sewage treatment plants. Since these compounds can be expected to alter the organic matrix of the soil (surfactants) or to remobilize heavy metals from soils or sediments (complexing agents), their occurrence in the environment and their effects have to be investigated to estimate their long-term risk potential. This could be a new task for specimen banking. To this end, (a) sensitive and specific detection methods for surfactants and complexing agents have to be developed at concentrations relevant to environmental occurrence, and (b) the effect of surfactants and complexing agents on the distribution of organic and inorganic pollutants in environmental compartments has to be investigated. Preliminary investigations show significant synergistic or antagonistic effects of various surfactants on the adsorption of pollutants at clay minerals.

In situ measurements on surfactant–mineral interactions by polarographic adsorption kinetics

Adsorption of surfactants at the mercury/electrolyte interface causes changes in electrode capacity. This phenomenon can be used for surfactant analysis in low and ultra-low concentration ranges. Tensammetry is carried out by alternating current or potential pulse techniques. Time-dependent concentration changes can be determined by adsorption kinetics at the mercury/electrolyte interface. As the interaction of surfactants with the mercury/electrolyte interface strongly depends on the potential of the electrode, repeated potential jumps can be used to generate adsorption–desorption cycles. This permits rapid determination of constant or time-dependent concentration. The adsorption kinetics of cationic and non-ionic surfactants on clay minerals were determined by Kalousek polarography. These two types of surfactant exhibit different behaviour. Many other adsorption phenomena might also be investigated by using the method described here.

Extraction and Separation of Pah from Fine Soil Materials by Microemulsions

Soils with more than 30–40% of fine particles (< 63 μm) contaminated with slightly water-soluble pollutants are still problematic for soil washing processes. In these cases the amount of contaminated fine particles which must be separated and rejected is so high that soil washing becomes uneconomical compared to direct disposal of the contaminated soil. Therefore methods for the separation of contaminants from fine particles are still being sought.