Eliminierung und Rückgewinnung von Metallionen aus Abwässern — eine Übersicht

The present state and the trends of the recovery of heavy metals from wastewaters are presented. The classical precipitation techniques are insatisfactory due to increases of solubility in the presence of impurity ions and/or complexing agents. At present, ion-exchange processes constitute the most frequently used method of metal recycling with an effective enrichment of metal ions. For the effective separation of metals from solutions of a low concentration the electrolytic reduction demands large electrode surface areas. In cells with fixed-bed or fluidized cathodes one can obtain specific electrode surface areas of some 10³ m²/m^m3. For the future, processes of extraction and especially membrane separation will gain in importance. In the past few years, a large number of highly selective metal extracting agents as well as the liquid membrane permeation with suitable carriers were developed. Combinations of membrane separation processes with chemical reactions may attain the same importance, as e.g. ultrafiltration in connection with the fixation of metal ions to watersoluble polymers. In the long run, especially techniques will prevail which will not only result in metal enrichment but also in the recovery of the raw material water.     

Der Einfluß der Komplexierung auf die Kupfertoxizität bei Blaualgen

Some aspects of the influence of copper speciation on toxicity for blue-green algae are reviewed. The experimental part concentrates on Oscillatoria redekei and Aphanizomenon gracile. The two investigated species produce strong extracellular copper complexing ligands: Oscillatoria redekei in the exponential and stationary growth phase, and Aphanizomenon gracile has a distinct detoxification capacity. The detoxification of copper by synthetic agents was investigated using ethylene-diamine-tetraacetic acid. Simultaneous addition of Cu²⁺ and Na₂EDTA gives evidence for a slow complexation reaction. Hence an excess of Na₂EDTA is necessary for a fast and complete detoxification of copper. Model calculations are reported to show that the precipitation of copper compounds is not probable under the conditions used.     

Effect of Complexing Agents on the Acute Toxicity of Copper to Common Guppy Lebistes reticulatus (PETERS)

The acute toxicity of copper and copper plus complexing agents to common guppy Lebistes reticulatus was studied for 96 h by a static bioassay technique. The addition of complexing agents viz. disodium salt of EDTA, citric acid, sodium thiosulphate and glycine in Cu²⁺ solutions caused a great decrease in the per-cent mortality as compared to that of Cu²⁺ test solutions alone. 10 mg/l of complexing agent was added in each copper concentration in all the test series. The 96 h LC₅₀ values and 95% confidence limits in mg/l of Cu²⁺ plus were 1.23 (0.95…1.65) for Cu²⁺ alone; 4.30 (4.04 … 4.55) for Cu²⁺ plus EDTA; 1.94 (1.69 … 2.18) for Cu²⁺ plus citric acid; 3.44 (2.96 … 3.74) for Cu²⁺ sodium thiosulphate and 2.29 (2.22 … 3.02) for Cu²⁺ plus glycine.     

Equilibrium approaches to natural water systems—Part 4

The contribution of organic bases to the alkalinity of the anoxic hypolimnetic water of a small lake has been studied. By means of potentiometric titrations the presence of a protolyte, best described as a one-protonic acid (HL) could be shown. The pka of HL was found to be 4.24±0.08 (3σ) and it reached a concentration of 0.4 mM close to the sediment surface. Because of precipitation reactions titration experiments could not be performed above pH≈6.8, but indications of additional bases having a pka >8were found. The results indicate the presence of low molecular weight carboxylic acids and free amino acids originating from bacterial decomposition of organic material. Polarographically measured Fe²⁺ concentrations, in situ pH measurements and various model ligands were used to assess the metal speciation in the hypolimnion. Although strong metal complexing agents such as citrate and glutamine may be present, the total concentrations of both Fe²⁺ (up to 0.6 mM) and ligands are too low to bind more than at maximum 20% of the ferrous iron.     

Zum Einfluß von Rückständen von Zink- und Bleiverbindungen im Wasser auf die Assimilation von Fontinalis antipyretica

The carbon-dioxide assimilation of Fontinalis antipyretica is inhibited by 100 mg/1Zn²⁺ or Pb²⁺, without a lethal effect being caused. With increasing time of exposure from one to six days the threshold value of toxicity is lowered and at the same time the net assimilation is reduced within the range of concentration of 0.1 mg/1. In the ecological optimum of the environmental conditions the toxicity is weaker than under other unfavourable environmental conditions at the same time. Therefore, the photoecologically optimum illumination of 1200 lx is an effective bioprotector against phytotoxic lead ion concentrations, so that at 1200 lx also at a comparatively high load a positive photosynthesis balance can be maintained. In the dark, in the first hour after the application of the lead ions dissimilation is a function of concentration, subsequently the respiration differences decrease very much in the range between 0 and 100 mg/1 lead(II)-ions. Stimulating effects could be demonstrated only by 0.01 mg/1 Pb²⁺ and only for the carbondioxide assimilation.     

Hydrogeochemistry,contaminant transport and tectonic effects in the Okposi-Uburu salt lake area of Imo State,Nigeria

ABSTRACT

Hydrogeochemical data of groundwater samples from 35 boreholes drilled in the Okposi-Uburu salt lake area are analysed. The data reveal that concentrations of dissolved geochemical constituents such as calcium (Ca²⁺), manganese (Mn²⁺), magnesium (Mg²⁺), chloride (C1^?), and sulphate (SO²⁺ ₄) ions show significant areal variations. Dissolved solids, chloride and manganese ions have concentrations up to and above the objectionable limits for drinking water in the salt lake area. Concentrations of dissolved solids in this zone are about 1200 mg 1^?1. Concentrations of chloride and manganese ions are 350 mg 1^?1 and 1.0 mg 1^?1 respectively. These geochemical constituents and groundwater flow patterns show that transport of contaminants away from the source zone has been greatly influenced by advection, while in areas of high velocity dispersion is the controlling factor. Temperatures for the Okposi and Uburu salt springs are 34.4 and 37.5°C respectively. Bomb tritium indicated water of pre-1953 age. Deuterium and oxygen-18 showed high isotopic enrichment. The high concentrations of dissolved salts resulted from the combined effects of migration of dissolved salts through fractures at the lake floor and evaporation from the lake surface. These findings are related to the tectonic history of the Okposi-Uburu area.     

Effects of Alkali and Alkaline‐earth Cations on the Removal of Reactive Dyes with Cucurbituril

The sorption of reactive (textile) dyes onto cucurbituril, a cyclic polymer with hydrophobic cavity, was studied. Dye sorption is strongly enhanced by Ca²⁺ or Sr²⁺ concentrations up to 100 mmol/L for all studied dyes. Mg²⁺ and alkaline ions had similar effects for only one dye (Reactive Red 120), and only at higher concentrations. Concentrations above 100 mmol/L – depending on cation and dye – dissolve cucurbituril and prevent dye removal. As shown in previous studies by our group loadings obtained under suitable conditions (calcium concentration between 2 and 100 mmol/L, total salt concentration not exceeding 100 mmol/L) are 1 to 1.7 mol/mol or 0.9 to 1.8 g/g. The chemical mechanism responsible for the ionic influences is still under investigation. Generally, cucurbituril is a potent sorbent for reactive dyes. However, the technical application is still limited by the lack of a support material that would allow use in fixed bed filters.     

The Role of Particulate Matter in the Mobilization of Trace Metals during Anaerobic Digestion of Solid Waste Material Die Bedeutung der partikulären Substanz für die Mobilisierung von Spurenmetallen beim anaeroben Abbau fester Abfallstoffe

Metal ions bound to particulate matter represent the greatest portion (i.e. > 95%) of the total metal content found in leachate from reactor experiments where solid waste material was anaerobically digested. This seems true even though strong complexing agents are in solution which increase the solubility of Pb and Cu by a factor up to 10⁴… 10⁵ over that theoretically predicted according to the solubility of the corresponding sulfide mineral. A titrimetric characterization of the metal ion binding sites of the particulate matter suggests that the metal binding properties of the particulate matter are mainly due to organic, aminoacid-type compounds (amines. thio groups, carboxylic groups) probably of bacterial origin. The change of the concentration of the binding sites with time, together with the change of the composition of the particulate matter indicates that bacterial flocs are suspended in the leachate during the switch from acidogenic to methanogenic conditions — either due to the detachment of bacterial films from the solid material by the intensive gas production or due to the formation of syntrophic methanogenic bacterial associations or a combination of both. A combination of the two factors, strong affinity of bacterial mass to metal ions on the one hand, and suspending of the bacterial mass in the leachate on the other hand, will therefore imply a great mobilizing potential for trace metals. Consequently, the highest concentrations of particulate bound Cd were found in reactor experiments where sewage sludge contaminated with Cd was added to the waste material. An increase of the concentration of dissolved cadmium over the solubility of cadmium sulfide, however, could not be observed.     

Iron ions Fe<Superscript>2+</Superscript> and Fe<Superscript>3+</Superscript> in a magnetic model of the sedimentary medium

The concentration of rock-forming elements, the static magnetic susceptibility κ, spectra of electron paramagnetic resonance, and their relative intensities I are studied in samples from a borehole drilled in Cenozoic sedimentary deposits of southern Western Siberia. All measured values experience appreciable irregular variations with depth. A linear dependence exists between κ and I within the range of their medium and large values; κ and I have maximum values in the same sample, and κ_max = 1920 × 10^?6SI, κ_min = 210 × 10^?6 SI, and κ_av = 630 × 10^?6 SI. The magnetic properties of the samples are controlled by Fe²⁺ ions present in clastic material and by microphases (clusters) with Fe³⁺ ions of the goethite and lepidocrocite type present in the cement. The theoretically possible magnetic susceptibility of the Fe²⁺ ion system (provided that all iron exists in this form) is quite comparable with κ_min but, even with very high concentrations of Fe²⁺, does not reach half of κ_av: (154 < κ(Fe²⁺) < 254) × 10^?6 SI. Anomalously high values of κ are due to a large number of clusters with Fe³⁺ ions if structural units FeOOH do not dissociate and the interaction of the clusters with hydroxides of aluminum and precipitation medium impedes the process of their coagulation. Otherwise, the cluster sizes gradually increase, an antiferromagnetic structure develops in clusters, and the magnetic susceptibility decreases.     

Transformations of runoff chemistry in the Arctic tundra,Northwest Territories,Canada

The transformation of snowmelt water chemical composition during melt, elution and runoff in an Arctic tundra basin is investigated. The chemistry of the water flowing along pathways from the surface of melting snow to the 95·5 ha basin outlet is related to relevant hydrological processes. In so doing, this paper offers physically based explanations for the transformation of major ion concentrations and loads of runoff water associated with snowmelt and rainfall along hydrological pathways to the stream outlet. Late‐lying snowdrifts were found to influence the ion chemistry in adjacent reaches of the stream channel greatly. As the initial pulse of ion‐rich melt water drained from the snowdrift and was conveyed through hillslope flowpaths, the concentrations of most ions increased, and the duration of the peak ionic pulse lengthened. Over the first 3 m of overland flow, the concentrations of all ions except for NO increased by one to two orders of magnitude, with the largest increase for K⁺, Ca²⁺ and Mg²⁺. This was roughly equivalent to the concentration increase that resulted from percolation of relatively dilute water through 0·25 m of unsaturated soil. The Na⁺ and Cl^? were the dominant ions in snowmelt water, whereas Ca²⁺ and Mg²⁺ dominated the hillslope runoff. On slopes below a large melting snowdrift, ion concentrations of melt water flowing in the saturated layer of the soil were very similar to the relatively dilute concentrations found in surface runoff. However, once the snowdrift ablated, ion concentrations of subsurface flow increased above parent melt‐water concentrations. Three seasonally characteristic hydrochemical regimes were identified in a stream reach adjacent to late‐lying snowdrifts. In the first two stages, the water chemistry in the stream channel strongly resembled the hillslope drainage water. In the third stage, in‐stream geochemical processes, including the weathering/ion exchange of Ca²⁺ and Mg²⁺, were the main control of streamwater chemistry. Copyright © 2006 John Wiley & Sons, Ltd.     

Adsorption–Reduction Behavior of Co(NH3) on Activated Carbon

A novel method has been put forward to retrofit the wet ammonia desulfurization process to realize the combined removal of sulfur dioxide and nitric oxide by introducing soluble cobalt(II) salt into aqueous ammonia solution. The active constituent of scrubbing NO from the flue gases is the produced by ammonia coordinating with Co²⁺. The regeneration of can be realized under the catalysis of activated carbon so as to sustain a high NO removal efficiency for a long time. In this paper, the adsorption–reduction behavior of on activated carbon has been researched using scanning electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. A conclusion can be drawn from the results that cobalt ions in the aqueous solution are adsorbed by activated carbon and most of them are reduced to Co²⁺ ions, and some of the Co²⁺ ions are further reduced into metallic cobalt. The results also demonstrate that the functional groups on the surface of carbon take part in this redox reaction. The C? H groups on the carbon surface are oxidized into C? OH, and then some of the hydroxyl groups are further oxidized into carbonyl or carboxyl groups.     

Removal of Copper,Nickel and Zinc Ions from Aqueous Solution by Chitosan‐8‐Hydroxyquinoline Beads

In this work, 8‐hydroxyquinoline is used as the active sites in cross‐linked chitosan beads with epichlorohydrin (CT‐8HQ). The CT‐8HQ material was shaped in bead form and used for heavy metal removal from aqueous solution. The study was carried out at pH 5.0 with both batch and column methods and the maximum adsorption capacity of metal ions by the CT‐8HQ was attained in 4 h in the batch experiment. The adsorption capacity order was: Cu²⁺ > Ni²⁺ > Zn²⁺ for both mono‐ and multi‐component systems with batch conditions. From breakthrough curves with column conditions, the adsorption capacity followed the order Cu²⁺ > Zn²⁺ > Ni²⁺ for both mono‐ and multi‐component systems. The CT‐8HQ beads maintained good metal adsorption capacity for all five cycles with absorbent restoration achieved with the use of 1.0 mol L^–1 HCl solution, with 90% regeneration.     

Classification of hydrological regimes of northern floodplain basins (Peace–Athabasca Delta,Canada) from analysis of stable isotopes (δ18O, δ2H) and water chemistry

We used stable isotopes (δ¹⁸O and δ²H) and water chemistry to characterize the water balance and hydrolimnological relationships of 57 shallow aquatic basins in the Peace‐Athabasca Delta (PAD), northern Alberta, Canada, based on sampling at the end of the 2000 thaw season. Evaporation‐to‐inflow ratios (E/I) were estimated using an isotope mass‐balance model tailored to accommodate basin‐specific input water compositions, which provided an effective, first‐order, quantitative framework for identifying water balances and associated limnological characteristics spanning three main, previously identified drainage types. Open‐drainage basins (E/I < 0·4; n = 5), characterized by low alkalinity, low concentrations of nitrogen, dissolved organic carbon (DOC) and ions, and high minerogenic turbidity, include large, shallow basins that dominate the interior of the PAD and experience frequent or continuous river channel connection. Closed‐drainage basins (E/I ≥ 1·0; n = 16), in contrast, possess high alkalinity and high concentrations of nitrogen, DOC, and ions, and low minerogenic turbidity, and are located primarily in the relict and infrequently flooded landscape of the northern Peace sector of the delta. Several basins fall into the restricted‐drainage category (0·4 # E/I < 1·0; n = 26) with intermediate water chemistries and are predominant in the southern Athabasca sector, which is subject to active fluviodeltaic processes, including intermittent flooding from riverbank overflow. Integration of isotopic and limnological data also revealed evidence for a new fourth drainage type, mainly located near the large open‐drainage lakes that occupy the central portion of the delta but within the Athabasca sector (n = 10). These basins were very shallow (<50 cm deep) at the time of sampling and isotopically depleted, corresponding to E/I characteristic of restricted‐ and open‐drainage conditions. However, they are limnologically similar to closed‐drainage basins except for higher conductivity and higher concentrations of Ca²⁺ and Na⁺, and lower concentrations of SiO₂ and chlorophyll c. These distinct features are due to the overriding influence of recent summer rainfall on the basin water balance and chemistry. The close relationships evident between water balances and limnological conditions suggest that past and future changes in hydrology are likely to be coupled with marked alterations in water chemistry and, hence, the ecology of aquatic environments in the PAD. Copyright © 2006 John Wiley & Sons, Ltd.     

Characterization and Application of Dried Plants to Remove Heavy Metals,Nitrate, and Phosphate Ions from Industrial Wastewaters

Low cost adsorbents were prepared from dried plants for the removal of heavy metals, nitrate, and phosphate ions from industrial wastewaters. The efficiency of these adsorbents was investigated using batch adsorption technique at room temperature. The dried plant particles were characterized by N₂ at 77 K adsorption, scanning electron microscopy, energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy, and phytochemical screening. The adsorption experiments showed that the microparticles of the dried plants presented a good adsorption of heavy metals, phosphate, and nitrate ions from real wastewaters. This adsorption increased with increasing contact time. The equilibrium time was found to be 30 min for heavy metals and nitrate ions and 240 min for phosphate ions. After the adsorption process, the Pb(II) concentrations, as well as those of Cd(II), Cu(II), and Zn(II) were below the European drinking water norms concentrations. The percentage removal of heavy metals, nitrates, and phosphates from industrial wastewaters by dried plants was ～94% for Cd²⁺, ～92% for Cu²⁺, ～99% for Pb²⁺, ～97% for Zn²⁺, ～100% for ${\rm NO}_{{\rm 3}}^{{-} } $ and ～77% for ${\rm PO}_{{\rm 4}}^{3{-} } $ ions. It is proved that dried plants can be one alternative source for low cost absorbents to remove heavy metals, nitrate, and phosphate ions from municipal and industrial wastewaters.     

Hydrogeochemical Evolution of Interaction Between Surface Water and Groundwater Affected by Exploitation

Hydrogeochemical evolution of interactions between surface water and groundwater is crucial for guaranteeing water supply quality in a riverside water source area. This study focuses on the seasonal and spatial characteristics of hydrogeochemical evolution affected by groundwater exploitation in the Hulan water source area using hydrochemical analyses and stable isotope tracers. Results show that the concentrations of major ions and total dissolved solids (TDS) increase considerably during the dry season. A bicarbonate water type is primarily produced by the dissolution of calcite, dolomite and gypsum, as well as the cation exchange and human activities. Along the typical infiltration path, the proportions of surface water increase with proximity to the river from 8%-63% during the wet season to 11%-84% during the dry season, which are attributed to an increased hydraulic gradient by exploitation. The typical path is classified into two zones. The first is the intensive mixing zone (within 1 km) with increasing concentrations of major ions and TDS due to mixing effect. The second is the exploitation influence zone (1-3.3 km) with increased concentrations of Ca²⁺, Mg²⁺, SO₄²⁻, and HCO₃⁻ during the dry season due to two reasons of seasonal variations in evaporation, stronger water-rock interactions and mixing effects with increased surface water by exploitation.     

Präzipitation von Aluminium und Phosphat in Gewässern unter dem Einfluss von Versauerung

Precipitation of Aluminium and Phosphate Affected by Acidification Acidified waters often show elevated concentrations of Al (with up to 6 mg L^–1 being not unusual). A pH increase resulting e.g. from mixing with non‐acidified water or from biological activities may be linked with Al precipitation. Up to now, this phenomenon was described for acid mine drainages. This investigation focuses on a whitish precipitate naturally formed in a brook of an atmospherically acidified catchment in the Ore Mountains, Germany. Based on infrared spectra the precipitate was identified as an Al‐hydroxosulfate with crystal water. A simulation of natural conditions in the laboratory showed that Al precipitated only if sulfate or phosphate ions were added to the solution. In the case of sulfate being added, the infrared spectrum of the precipitate was similar to the natural precipitate. ²⁷Al NMR spectroscopy revealed tetrahedrally coordinated Al in some precipitates which evidences the participation of the tridecameric [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺ cation beside other polymeric Al cations. Precipitation experiments subjected to the given conditions showed that the phosphate elimination from solution with Al was much higher than with Fe. With Al and Fe added together, the P elimination rate was likewise high, and phosphate was bound onto Al in the precipitate. This was demonstrated by SEM‐EDX spectroscopy. Based on these results we present a possible reaction mechanism. The precipitation of Al together with P allows a significant retention of both elements in sediments because in contrast to Fe, Al immobilizes phosphate even under anoxic conditions.     

The location of Fe3+ ions in forsterite (Mg2SiO4)

The electron spin resonance spectrum of Fe³⁺ in a single crystal of forsterite was studied. Two distinct patterns of about equal intensities were observed which are due to Fe³⁺ at two distinct positions with 4a (M1)and4c (M2or Si) symmetry of Pbnm. The assignment of the 4c pattern to Fe³⁺ ions at the Si position cannot be excluded by symmetry but it is unlikely. The Hamiltonian parameters A and E/D are consistent with the conclusion that Fe³⁺ in this crystal is disordered over two distinct octahedral positions.     

Untersuchungen zur Adsorption von Spuren hydrolysierbarer Metallionen an Oberflächen

In static laboratory experiments there are determined quantities influencing the adsorption of selected metal ions on different surfaces (base metals, glass of instruments, quartz glass, plastic materials, precious metals). A great dependence on pH, ionic species, ionic concentration, material as well as temperature and presence of complexing agents is observed. Processes are proposed or confirmed by which the losses of material during the trace analysis are reduced.     

Qualitätsprobleme bei der Gewinnung von uferfiltriertem Grundwasser in Ungarn

Summary: In Hungary a large proportion of the drinking-water demand is met by bank filtration. Especially the middle section of the Danube stretch is used for drinking-water supply, also for the capital Budapest (310 · 10⁶ m³/a). The considerable pollutant load imported, anyhow, is increased by several Hungarian sources of contamination. The Danube has such a high self purifying capacity that, among other things, the annual COD-Mn load by the city of Budapest amounting to 140,000 t is degraded to such a level that the export of organic pollutants in the Danube from Hungary is not greater than the import. Heavy metals get into the bank filtrate through organic complexing agents. Also organochlorine compounds and their precursors were quantitatively determined. In Budapest water is treated with ozone, activated carbon and open high-rate filtration.