The degree and source of plastic recyclates contamination with polycyclic aromatic hydrocarbons.

In this research, the degree and source of recyclates contamination with polycyclic aromatic hydrocarbons (PAH) was studied in eight different polyolefin recyclate samples; four originating from post-consumer packaging waste and four originating from a mixed source (post-industrial, post-commercial, and post-consumer). The aim was to assess the applicability of these recyclates in the different products' categories. Furthermore, the impact of previous contamination with PAH was excluded by analysing pure plastics before and after undergoing simulated recycling processes. Polythene recyclates originating from post-consumer plastic packaging waste had lower concentrations of the 16-US-EPA PAH (922.15 ± 420.75 µg kg-1) in comparison to the ones of a mixed origin (2155.43 ± 991.85 µg kg-1), r = -0.35, p > 0.05. The degree of recyclates contamination with PAH was always within the REACH limits for consumer products (<1.0 mg kg-1). On the other hand, only polythene recyclate sample originating from post-commercial waste did not comply with the REACH limits for children articles (0.5 mg kg-1). Hence, the source of plastic waste defines the quality of recyclates. All in all, the results indicated that the contamination of polyolefin recyclates with PAH is attributed to the material's previous contamination, or the sorption of plastics to organic compounds from the surrounding environment. Exposing plastics containing PAH additives to heat during extrusion could result in further accumulation of PAH in plastics.

Reduction of fuel side costs due to biomass co-combustion.

The feasibility and influence of co-combustion of woody biomass on the fuel side costs is discussed for three hard coal power plants located in Berlin, Germany. Fuel side costs are defined as the costs resulting from flue gas cleaning and by-products. To have reliable data, co-firing tests were conducted in two power plants (i.e., slag tap furnace and circulating fluidising bed combustion). The amount of wood which was co-fired varied at levels below 11% of the fuel heat input. Wood chips originating from landscape management were used. The analyses show that co-combustion of woody biomass can lower the fuel side costs and that the co-combustion at a level below 10% of the thermal capacity is technically feasible without major problems. Furthermore, a flexible spreadsheet tool was developed for the calculation of fuel side costs and suggestions for operational improvements were made. For example, the adaptation of the Ca/S ratio (mass ratio of calcium in limestone to sulphur in the fuel) in one plant could reduce the fuel side costs up to 135 k€ yr(-1) (0.09 €M Wh(-1)).

Extent and mechanism of metal ion incorporation into precipitated ferrites.

The ability of many noniron metals to be incorporated into the structure of ferrites is being utilized in numerous industrial and environmental applications. The incorporation of some of these metals during Fe(II) oxidation-induced precipitation at moderate temperatures (80-100°C) appears to be limited, for reasons not fully understood, and to extents not always agreed (e.g., Ni(2+), Cr(3+)). In this paper, the incorporation maxima of six metals into the structure of precipitated ferrites (in terms of x in Me(x)Fe(3-)(x)O(4), Me represents a noniron metal) were concluded to be 1.0, 1.0, 0.78, 0.49, 0.35, and 0.0 for Zn(2+), Co(2+), Ni(2+), Al(3+), Cd(2+) and Cr(3+), respectively. With the exception of the much larger Cd(2+), these values were associated with kinetic considerations controlled by the H(2)O exchange rate between the hydration shells surrounding the dissolved metal ion.

Iron-oxidation processes in an electroflocculation (electrocoagulation) cell.

The processes of iron oxidation in an electroflocculation cell were investigated for a pH range of 5-9 and electric currents of 0.05-0.4A (equivalent current densities of 8.6-69 A/m(2)). At all pH values and electric currents investigated, it was demonstrated and proven that for all practical purposes, the form of iron that dissolves from the anode is Fe(2+) (ferrous). The difference between the amount of theoretical dissolution as calculated by Faraday's law and the amount of observed dissolved iron ions may indicate two phenomena in electrochemical cells. The first is possible dissolution of the anode even without the operation of an electric current; this led to higher theoretical dissolution rates at lower pH. The second is the participation of some of the electrons of the electric current in reactions other than anode dissolution which led to lower theoretical dissolution rates at higher pH. Those other reactions did not lead to an increase in the local oxidation saturation level near the anode and did not affect iron-oxidation rates in the electroflocculation processes. The oxidation rates of the dissolved Fe(2+) (ferrous) to Fe(3+) (ferric) ions in electroflocculation processes were strongly dependent on the pH and were similar to the known oxidation rates of iron in non-electrochemical cells.

Removal of Zn(II), Cu(II), Ni(II), Ag(I) and Cr(VI) present in aqueous solutions by aluminium electrocoagulation.

The performance of an electrocoagulation system with aluminium electrodes for removing heavy metal ions (Zn2+, Cu2+, Ni2+, Ag+, Cr2O7(2-)) on laboratory scale was studied systematically. Several parameters - such as initial metal concentration, numbers of metals present, charge loading and current density - and their influence on the electrocoagulation process were investigated. Initial concentrations from 50 to 5000 mg L(-1) Zn, Cu, Ni and Ag did not influence the removal rates, whereas higher initial concentrations caused higher removal rates of Cr. Increasing the current density accelerated the electrocoagulation process but made it less efficient. Zn, Cu and Ni showed similar removal rates indicating a uniform electrochemical behavior. The study gave indications on the removal mechanisms of the investigated metals. Zn, Cu, Ni and Ag ions are hydrolyzed and co-precipitated as hydroxides. Cr(VI) was proposed to be reduced first to Cr(III) at the cathode before precipitating as hydroxide.

Studies on electrochemical treatment of wastewater contaminated with organotin compounds.

Different anode materials were tested to evaluate their suitability to eliminate organotin compounds electrochemically from shipyard process waters. The capacity of two types of anode materials was investigated: niobium coated with boron-doped diamond (BDD) and titanium coated with iridium dioxide, (Ti/IrO(2)). The aim of this work was to characterize the performance of the process using both anode materials at different current densities, and also to evaluate the generation of by-products. A further objective of this work was to evaluate if operating at low potentials with BDD anodes (to avoid the generation of elemental oxygen) the consumption of energy for degradation of pollutants could be minimized. The processes were tested on synthetic and real shipyard water containing approximately 25,000ngL(-1) of tributyltin (TBT) (as Sn) and 5,000ngL(-1) dibutyltin. The range of current densities was between 6 and 70mAcm(-2). The results showed that electrochemical treatment is suitable to eliminate organotins down to very low concentrations following a stepwise debutylation mechanism. Both anode materials exhibited a similar performance with energy consumption in the range of 7-10kWhm(-3) in order to decrease organotins down to 100ngL(-1) (as Sn). For the water composition tested, BDD did not outperform Ti/IrO(2) as initially expected, most probably because organotins were not only oxidized by OH, but also by active chlorine compounds generated by the oxidation of chloride present in the wastewater (1.6gL(-1), Cl(-)) with both anode materials. It was also found that the residual oxidants remaining in the treated effluent had to be eliminated if the water is to be discharged safely in the aquatic environment.

Topics of water sciences and technology.

In the preceding series of contributions to ESPR typical examples from actual fields of water chemistry were presented on various topics: integrated water quality management, diagnosis of water bodies, therapy of aquatic systems, and fitness for aquatic systems. These contributions clearly showed the need and importance of more intensive research. In the principle committee III 'Basic Research' of the Water Chemical Society, various expert groups work on scientific backgrounds in these fields. Some relevant topics are selected in this outlook, mainly on interactions of solids with water, the role of environmental colloids, the development of modern biochemical methods for diagnosis, the impact of chemical speciation on bioavailability and water technology, and the development of advanced methods in water treatment technology. Innovative approaches to understand the interactions between pollutants, water and solids are crucial for assessment of contaminants with biochemical and analytical methods, for the development of new efficient technologies and for application of treatment methods with little or no waste and by-product formation.