Removing metals from waste solutions with low rank coals and related materials

Ion exchange media were produced by contacting brown coal, peat or wood sawdust with a solution of calcium hydroxide, preferably as an aqueous slurry of lime. The resultant calcium loading on the media, which ranged up to 8% for sawdust, 12% for peat and to 19% for brown coal, was exchanged for many metals in solution.Preliminary work showed the method to be amenable to extraction of copper, nickel, chromium, cadmium, lead, zinc, mercury, cobalt, silver, iron, manganese, vanadium, germanium, gallium, aluminium, antimony and uranium. For most of the metals more than 99% was removed from I g 1⁻¹ solutions.In more detailed work, confined to calcium loaded brown coal and solutions having metal concentrations more typical of industrial operations, minimum residual metal concentrations of 0.0005 mg l⁻¹ mercury; 0.02 mg 1⁻¹ copper; 0.02 mg 1⁻¹ zinc; <0.05 mg l⁻¹ cadmium; 0.1 mg 1⁻¹ lead and 0.2 mg l⁻¹ manganese were obtained. These results compare favourably with those reported for other relevant processes and there might be operational advantages in the method.The method can be applied either by agitating the calcium loaded media in the solution and then filtering, or by passing the solution through packed beds of the media. Where appropriate, dilute solutions can be up-graded for re-use by stripping the metals from the media which can also be re-used. Alternatively, the loaded media can be combusted and the metals recovered from the residues.The method might be applicable to mine drainage and to effluents from metallurgical processing and electroplating, but more work is required to assess costs.It is suggested that the method is environmentally preferable to other common effluent treatment procedures because it enables collection and recycling of heavy metal pollutants.     

Preliminary studies on the leaching of some trace metals from kitchen faucets

Preliminary studies were carried out on the leaching of copper, zinc, chromium, cadmium and lead from eight kitchen faucets by samples of raw, filtered and distributed Ottawa water, a sample of well water and deionized water containing 2 mg l⁻¹ aqueous fulvic acid. Leaching was effected by allowing the test solutions to stand in the inverted faucets for two successive 24-h periods. Concentrations of the metals found in the leachates were copper: first leaching, 0.12–28.0 mg l⁻¹, second leaching, 0.08-3.54 mg l⁻¹; zinc: first leaching, 0.13-10.25 mg l⁻¹, second leaching, 0.06-2.85 mg l⁻¹; chromium: first leaching, < 1.0 × 10⁻³ − 0.395 mg l⁻¹, second leaching, < 1.0 × 10⁻³−0.032 mg l⁻¹; cadmium: first leaching, < 0.05 × 10⁻³−0.01 mg l⁻¹, second leaching, < 0.05 × 10⁻³−4 × 10⁻³ mg l⁻¹; and lead: first leaching, < 0.2−110.0 mg l⁻¹, second leaching, < 0.2−82.0 mg l⁻¹. The faucets containing lead-soldered copper joints released high concentrations of lead, particularly in the case of leaching with the aqueous fulvic acid solution. Under the conditions of the present investigations it is indicated that in some cases the concentrations of metals leached could lead to intakes in excess of the maximum permissible limits for these metals. However, further investigations will be required to determine the possible contribution of these faucets to metal intake under normal usage.     

Electrodeposition of six heavy metals on reticulated vitreous carbon electrode

Six heavy metals, copper, cadmium, chromium, lead, uranium and zinc were deposited on cathodes made of a newly developed form of carbon, Reticulated Vitreous Carbon, in a laboratory scale electrochemical reactor. Different metals varied in the extent of their removal with copper depositing 100% at a flow rate of 0.24 cm min⁻¹ in a single pass while it would require a maximum of 20 passes for 100% chromium deposition at a flow rate of 1.8 cm min⁻¹, initial concentrations for both metals being 50 μmol 1⁻¹.Experiments conducted using 0.5 × 10⁻³ M CuSO₄ in 0.5 M Na₂SO₄ supporting electrolyte resulted in a mass transfer coefficient of the order of 10⁻³ cm s⁻¹ and a current efficiency of 64% for the electrodeposition of copper at a cell voltage of 4.0V. Because of very high porosity, 97%, high specific surface area, up to 66 cm² cm⁻³ for RVC grade 100, and useful electrochemical characteristics, RVC can be advantageously used as electrode material for heavy metal removal from dilute industrial effluents.     

The influence of heavy metals on a mixed bacterial population of sewage origin in the chemostat

A reproducible mixed continuous bacterial population has been cultured in the chemostat at a low dilution rate. Four species originally isolated from activated sludge were used to provide an inoculum. The influence of cadmium, chromium, copper and lead as shock doses has been examined at concentrations of 50 mg l⁻¹ and the response of the population was found to vary for each metal. The most toxic metal was copper followed by cadmium, lead and chromium. Continuous doses of chromium and lead have been studied, the latter over a range of concentrations. It appears that concentrations of lead as low as 5 mg l⁻¹ cause modifications in the individual population sizes. Some of the species studied were found to be more resistant to heavy metal toxicity than others.     

The effect of surfactants on the extraction-atomic absorption spectrophotometric determination of copper, iron, manganese, lead, nickel, zinc cadmium and cobalt

Nine surfactants representing pure cationic, anionic and non-ionic detergents, three industrially prepared detergents. sodium pyrophosphate. sodium tripolyphosphate, and a soap were investigated for their effect on the extraction-atomic absorption spectrophotometric determination of copper. iron, manganese and lead. Some results are also given for nickel, zinc, cadmium and cobalt. Cations were extracted into 10 ml of MIBK as APDC chelates. To Avoid emulsion formation, maximum concentration of LAS was 1 mg 1⁻¹, and for formulated and non-ionic detergents and washing powders it was 5 mg 1⁻¹.A standard addition procedure was used to obtain correct results for copper and nickel. Two extractions of iron, cobalt and lead, and one extraction of manganese, zinc and cadmium gave a recovery of 100 ± 5%. Soap gave high recoveries for iron and copper. NTA in concentrations up to 25 mg l⁻¹ did not interfere. EDTA in concentrations up to 25 mg l⁻¹ interfered with iron and nickel determinations, but the addition of 3 mg of aluminium removed the EDTA interference in the determination of copper, manganese, lead, zinc, cadmium and cobalt.For the determination of trace metals in polluted natural waters the amount of 4% APDC was increased to 10 ml and for manganese to 25 ml. An addition of 3 mg aluminium as nitrate after the addition of buffer with subsequent 20 min reaction time is required for the determination of all eight metals by the recommended procedures. The effect of humic acid was also investigated.     

Effects of copper, zinc and cadmium on Selanastrum Capricornutum

The algicidal and algistatic effects of copper, zinc and cadmium on Selanastrum capricornutum, a unicellular green algae were analyzed by using a modification of the Algal Assay Procedures Bottle Test.Algicidal concentrations of copper, zinc and cadmium were 0.30, 0.70, and 0.65 mg 1⁻¹. Treatment of Selanastrum with various concentrations of the metals resulted in similar growth rates characterized by extended lag growth phases.Combinations of copper, zinc and cadmium were similar in toxicity to equal concentrations of zinc. Combinations of copper and cadmium resulted in a greater growth rate than equal concentrations of copper suggesting that cadmium inhibits copper toxicity.Selanastrum was able to exist in waters from the upper South Fork and North Fork of the Coeur d'Alene River where zinc and other metals were in low concentration. However, the algae was not able to tolerate zinc concentrations greater than 0·5 mg 1⁻¹ from waters of other parts of the drainage. These observations were consistent with laboratory findings where 0.7 mg 1⁻¹ zinc was algicidal and 0.1 mg 1⁻¹ inhibited the growth of Selanastrum.     

Levels of heavy metals in outdoor and indoor dusts in Muscat,Oman

The concentrations of lead, copper, nickel, zinc and chromium in outdoor and indoor dusts collected from different sites in Muscat, Oman, were determined by flame atomic absorption. Results showed a wide range of concentrations, the means in the outdoor dust being, 65?±?50, 124?±?316, 47?±?45, 930?±?666 and 64?±?26 mg kg^??1 for lead, zinc, copper, nickel and chromium, respectively. The 2001 Omani phasing out of leaded fuel resulted in low levels of lead in outdoor dust compared to those reported in the literature. Outstanding was the high nickel concentration in outdoor dust when compared to that in the literature, the reason being natural soil pollution due to the local geology of the northern parts of Oman. The concentrations of chromium, copper and zinc are lower than or comparable to these in other cities around the world. The results also showed that the industrial activities in Muscat do not contribute significantly to metal pollution in street dusts.

On the other hand, the mean concentrations of lead, zinc, copper, nickel and chromium in indoor dust were 108?±?65, 753?±?1162, 108?±?91, 130?±?125 and 34?±?14 mg kg^??1, respectively. In general, zinc and nickel levels are higher than those reported in the literature while lead, copper and chromium levels are lower or comparable.

When outdoor and indoor dusts were correlated, the ratios between indoor–outdoor mean concentrations revealed that lead, zinc, and copper were generated internally, while nickel and chromium were from external sources.     

Trace metals: Cd, Cu, Pb and Zn in gelatinous macroplankton from the Northwestern Mediterranean

Gelatinous macroplankton organisms were collected in May 1984 in Villefranche-sur-Mer Bay and analysed for cadmium, copper, lead and zinc. Analyses were carried out by polarography for Cd, Cu and Pb and by flame atomic absorption for Zn. Phosphorus was also measured in the samples as a biomass parameter due to difficulties inherent in measuring dry weight of gelatinous organisms. The samples belong to the Tunicates, the Cnidarians (Hydromedusae, Siphonophores and Scyphomedusae), the Ctenophores and the Molluscs. Crustaceans living on some Tunicates were also sampled.As regards cadmium, copper and lead, mean concentrations did not show significant differences among the phyla studied: especially for Tunicates with mean values of 0.1 ng Cd μg P⁻¹, 2.0 ng Cu μg P⁻¹ and 0.9 ng Pb μg P⁻¹ and for Cnidarians with mean values of 0.5 ng Cd μg P⁻¹, 2.0 ng Cu μg P⁻¹ and 0.9 ng Pb μg P⁻¹ and for Cnidarians with mean values of 0.5 ng Cd μg P⁻¹, 2.0 ng Cu μg P⁻¹, 1.0 ng Pb μg P⁻¹. On the other hand, mean zinc concentrations were significantly lower in Tunicates (7.9 ng Zn μg P⁻¹) than in Cnidarians (36.8 ng Zn μg P⁻¹).Zinc seems to be preferentially concentrated in organisms which are rich in collagen, constituting the mesoglea, such as the Cnidarians, the Ctenophore and the gelatinous Mollusc studied, rather than in organisms rich in tunicin such as the Tunicates.     

Environmental chemistry of copper in Lake Monona, Wisconsin

Lake Monona, located at Madison, Wisconsin, received over 1.5 × 10⁶ pounds of copper sulfate in the past 50 yr to control excessive algal growth. Dissolved copper on Lake Monona epilimnion is inversely related to pH which indicates possible control of dissolved copper by basic copper carbonate. Concentrations as high as about 4 μg Cu l⁻¹ were found in Lake Monona epilimnion, which also contains 3.3 me l⁻¹ (milliequivalents per liter) of alkalinity, mostly bicarbonate. Concentrations of dissolved copper were consistently lower (0.3 μg Cu l⁻¹) in the hypolimnion. Sulfide probably controls dissolved copper in the hypolimnion during anoxic conditions because of sulfide insolubility. Particulate copper concentrations of about 3 μg l⁻¹ increased slightly with depth. The highest concentrations of copper in Lake Monona sediments (650 mg kg⁻¹) were found approximately 60 cm below the current sediment surface. Surface sediments of Lake Monona contained approximately 250 mg Cu kg⁻¹ sediment dry weight.     

Zinc, cadmium and lead in water, sediments and submerged plants of the Derwent Reservoir, Northern England

A partial budget is presented of the zinc, cadmium and lead entering the Derwent Reservoir. The mean levels in the water column upstream of the site of inflow are: Zn, 0.216 mg 1⁻¹ ; Cd, 0.003 mg 1⁻¹; Pb, 0.065 mg 1⁻¹; the levels after passage through the 4.1 km² reservoir fall by: Zn, 70.3%; Cd, 98.3%; Pb, 89.2%. Most of these metals are deposited in sediments, the mean values for which are: Zn, 1035 μg⁻¹; Cd, 13μg⁻¹; Pb, 827μg⁻¹. Lead, a higher percentage of which occurs as particulate material, is deposited more rapidly than zinc; this effect is especially obvious when streaming of colder water along the bottom of the reservoir takes place at the time of floods. Macroscopic plants are only occasional in this reservoir, due perhaps in part to heavy metal toxicity. Of the two most common submerged species, Nitella flexilis probably accumulates almost all of its metal content directly from the water, but the data suggest that sediments are a source of some of the heavy metals accumulated by Glyceria fluitans.     

Note on heavy metal concentration in the aquatic environment of the Kitakyushu district in Japan, 1976–1977

The concentrations of cadmium, copper and lead, in the aquatic environment of the Kitakyushu district, Japan from 1976 to 1977 were investigated. This survey covered all rivers which run through the area, the bay, and the sea surrounding the district. The values obtained showed no significant heavy metal pollution, compared with values found in the literature for metal concentrations in other parts of the world, except for the concentrations of Dokai Bay. The concentrations of lead of the Dokai Bay showed an obviously high value, 40 μg 1⁻¹ (14–74 μg 1⁻¹, n = 32). This is due to the industrial activities of the surrounding area.     

Variation of sludge volume index with activated sludge characteristics

Activated sludge samples from 2 laboratory units and 12 sewage treatment plants were examined to determine the effect of filamentous microorganisms, floc size and suspended solids concentration on SVI. An attempt was also made to correlate SVI to zone settling velocity. At a suspended solids concentration range of 700–4800 mg 1⁻¹ there was no effect of filamentous microorganisms at filament length concentrations below 10⁷μm (mg SS)⁻¹. However, when it was over 10⁷ μm (mg SS)⁻¹ SVI increased sharply with increasing concentrations of filamentous microorganisms.At all suspended solids concentrations examined SVI varied with floc size at filament length concentrations below 10 μm (mg SS)⁻¹. But, at filament length concentrations higher than this level, no effect of floc size on SVI was observed.The effect of suspended solids concentration on SVI was examined at different levels of filament lengths. It was found that the shape of SVI-suspended solids concentration curve varied with the level of filament lengths. A well defined relationship was found between SVI and zone settling velocity at all suspended solids concentrations examined.     

Effects of manganese, copper and lead on Selenastrum capricornutum and Chlorella stigmatophora

Algal assays were conducted to observe the responses of Selenastrum capricornutum and Chlorella stigmatophora to the metals manganese, copper and lead, added singly or in combination to both artificial media and natural waters. A 50% reduction in the total algal cell volume of Selenastrum in standard algal assay medium (SAAM) occurred by the addition of either 3.1 mg manganese 1⁻¹ 85 μg copper 1⁻², or 140 μg lead 1⁻¹. For Chlorella grown in 28 ppt artificial seawater plus full SAAM nutrients, the corresponding numbers were 50mg manganese 1⁻¹, 70 μg copper 1⁻¹ or 700 μg lead 1⁻¹. Of the metals tested, only lead was found in higher concentrations in urban and agricultural runoff than at least one of these levels.Theoretical considerations show that a product model is a more reasonable reference for no-interaction than an additive model for experiments in which toxic metals are added in combination. Combination experiments, in which any combination of the three metals act at the same time, indicate (1) synergism between manganese and copper, (2) antagonism between manganese and lead, and (3) antagonism between copper and lead. As to the manganese-lead interaction, it is shown that the lead-induced inhibition of cell division is offset, partially for Selenastrum and completely for Chlorella by the addition of manganese.     

Studies on the toxicity of copper sulphate to stone loach Noemacheilus barbatulus (L.) in hard water

The toxicity of copper sulphate to Noemacheilus barbatulus was studied for 64 days in a water of total hardness 249 mg l⁻¹ as CaCO₃. The 63-day lc₅₀ was approximately 0.25 mg Cu l⁻¹. Larger fish survived longer, and at concentrations greater than 0.29 mg l⁻¹ fish hid less during daylight. Noemacheilus surviving 0.12 mg Cu l⁻¹ for 64 days shed copper when placed in clean water for 7 days: gill, muscle, eye and vertebrae lost significant amounts of copper during this period. The opportunity to shed copper during a short period when the poison supply to their tank failed, may have allowed fish exposed to 0.49 mg l⁻¹ to live 12 days longer than expected. The sensitivity of Noemacheilus to copper, cadmium and zinc was compared with that of rainbow trout. Salmo gairdneri.     

Removal of humic substances from natural waters by reverse osmosis

An investigation of the potential use of reverse osmosis for the removal of humic substances in order to remove colour and haloform precursors in small waterworks has been carried out, using three different laboratory scale reverse osmosis units and several different membranes.Membrane pore size was found to be the most important factor that influenced both the permeate quality and the product water flux. Pressure was found to have no significant influence on permeate quality, but was linearly related to product water flux. The concentration of humic substances in the influent was not found to affect product water flux but the transport of humics across the membrane was found to be dependent upon influent concentration. For the selected membranes, the removal of humic substances amounted to 80–100% in terms of colour removal, and 50–99% in terms of permanganate value reduction. The most suitable membranes for the different available units were found to be Osmonics SEPA 89 (permeate flux 251 m⁻² h⁻¹ at 15 bars), DDS 865 (permeate flux, 1201 m⁻²h⁻¹ at 40 bars) and PCI T2A (permeate flux 901 m⁻²h⁻¹ at 20 bars). At suspended solids concentrations higher than 100 mg 1⁻¹ of bentonite, product water flux was significantly reduced.     

Removal of zeolite type a during primary sedimentation and its effect on metal removal

Using two pilot plants operated in parallel, treating settled sewage the removal of the detergent builder zeolite type A during primary sedimentation has been studied. With one zeolite free pilot plant acting as a control to the other it was also possible to determine the effect of zeolite on suspended solids and heavy metal removal over a range of hydraulic loadings. At both influent concentrations of zeolite studied (30 and 60 mg l⁻¹) zeolite removal was substantial under all conditions. No evidence of enhanced removal of suspended solids in the presence of zeolite was observed. Removals of lead, zinc, copper and chromium were slightly enhanced in some experiments. The observed improvements in metal removal appeared to be strongly influenced by the sewage matrix.     

Accumulation de quelques metaux lourds (Cd, Cu, Pb et Zn) chez l'eperlan (Osmerus mordax) preleve sur la rive Nord de l'Estuaire du Saint-Laurent

Heavy metals in trace amounts are normal constituents of marine organisms. At sufficiently high concentrations, heavy metals are toxic to living organisms and so it is important to know by how much their concentration may be increased before effects on marine or estuarine populations can be detected or commercial species become unsuitable as food. A method of removing metals is by storage in a particular tissue. Several different sites for storing metals were investigated and concentrations of Cd, Cu, Pb and Zn were examined in muscle, liver and gonads of the smelt (Osmerus mordax) from the North shore of the St Lawrence estuary. Copper and zinc are constituents of several enzymes and are absolutely essential for normal growth and development, while cadmium and lead are not known to have necessary physiological function. A modified wet digestion procedure was used to prepare biological samples for the determination of trace elements by flameless atomic absorption spectrophotometry procedure, using calibration standards made up in a matrix of similar acidity (Table 1). NBS reference material bovine liver was analyzed along with the samples and the results were within the specified tolerance (Table 2). Analyses were reported on a dry weight basis (Table 3) and the correlations with total body weight were determined by regression analysis. Copper (range 0.3–3.3 μg g⁻¹) and zinc (range 19–38 μg g⁻¹) in muscle fillets were found to be negatively correlated with total body weight (Fig. 1). Apparent decreasing concentrations in these two metal levels in muscle sample with increasing body weight were possibly due to factor such as dilution with growth. Growth may dilute metal concentrations in an organism if tissue is added faster than metal. Livers and gonads contained greater levels of the four metals than somatic muscle. Liver metal concentrations of Zn (range 29–108 μg g⁻¹) and Cd (range 0.06–0.37 μg g⁻¹) increased with total body weight. All equations fit data at P < 0.01 (Fig. 2). Positive correlations between size and metal concentrations suggest that net uptake may occur. Inessential, slowly exchanging metals such as Cd appear to reflect an uptake which tend to become a cumulative process (age dependence of concentrations). The occurrence of insignificant correlation between liver concentrations of Cu (mean value: 4 μg g⁻¹) and environmental concentrations of this metal was consistent with equilibration. Since fish are known to possess the metal binding protein metallothionein, a sequestering agent, detoxification of these metals in fish liver may be by sequestration rather than elimination. Increasing metal concentrations in liver may represent storage of sequestered products in that organ. In the gonads, no significant relationship exists between total body weight and trace metal contents. Results of t-test indicated that females had significantly greater Cu and Zn concentrations, but no significant difference existed between males and females for Cd concentrations (Figs 3 and 4). Thus, the relation between concentration and total body weight appears to be specific as to the species, tissues analyzed and environmental conditions. The comparison of metal concentrations in fish to assess variations in contamination levels requires understanding the relationship between metal concentration and body size within each population.     

Effect of copper and hexavalent chromium on the specific growth rate of ciliata isolated from activated-sludge

After growing mass and monoxenic cultures of three species of Ciliata (Vorticella microstoma, Colpidium campylum, and Opercularia sp.) with Alcaligenes faecalis as the sole protozoan food, and confirming that copper and hexavalent chromium did not affect the bacterial growth, the effect of these metals on the specific growth rate of each protozoa was examined. The term IL_m (median inhibitory limit) was used to define the metal concentration required to reduce the specific growth rate of protozoa to one-half of that of a control. The IL_m for copper was: 0·25 mg 1⁻¹ (V. microstoma), 0·32 mg 1⁻¹ (C. campylum), and 0·27 mg 1⁻¹ (Opercularia sp.). Regarding hexavalent chromium, IL_m for V. microstoma, C. campylum, and Opercularia sp. were 0·53, 12·9 and 20·2 mg 1⁻¹, respectively. Acclimation of each protozoa to these metals for 96 h resulted in IL_m enhanced values of 1·2–2·2 times as large as that for the control.     

The effect of surfactants on the mixed chelate extraction-atomic absorption spectrophotometric determination of copper, nickel, iron, cobalt, cadmium, zinc and lead

Twelve surfactants representing pure cationic, anionic and non-ionic detergents, three commercial detergents, sodium pyrophosphate, sodium tripolyphosphate, a soap, nitrilotriacetic acid (NTA), EDTA, and humic acid were investigated for their effect on the extraction-atomic absorption spectrophotometric determination of copper, nickel, iron, cobalt, cadmium, zinc and lead. Cations were extracted into 10 ml of a solution containing diphenylthiocarbazone, 8-quinolinol and acetyl acetone in ethyl propionate. To avoid emulsion formation, the maximum concentration of linear alkylate sulphonate (LAS) was 10 mg l⁻¹ and for solid industrial LAS-type detergent was 50 mg l⁻¹, but washing powder did not interfere at 100 mg l⁻¹. Cationic and non-ionic detergents gave low recoveries for cobalt. Condensed phosphates at a concentration of 20 mg l⁻¹ did not cause significant interference. NTA interfered with nickel extraction and EDTA with all metals. Humic acid, however, gave no interference. A standard addition procedure can be used to correct the results.A comparison is made between the APDC-MIBK and the mixed chelate-ethyl propionate methods for the determination of trace metals in the presence of various surfactants in natural waters; the latter is preferable.     

Acute and chronic toxicity of lead to rainbow trout salmo gairdneri, in hard and soft water

Lead was found to be highly toxic to rainbow trout in both hard water (hardness 353 mg l⁻¹ as CaCO₃) and soft water (hardness 28 mg l⁻¹. Analytical results differ greatly with methods of analysis when measuring concentrations of lead in the two types of water. This is exemplified in LC50's and maximum acceptable toxicant concentrations (MATC's) obtained when reported as dissolved lead vs total lead added in hard water. Two static bioassays in hard water gave 96-h LC50's of 1.32 and 1.47 mg l⁻¹ dissolved lead vs total lead LC50's of 542 and 471 mg l⁻¹, respectively. In a flow-through bioassay in soft water a 96-h LC50 of 1.17 mg l⁻¹, expressed as either dissolved or total lead, was obtained. From chronic bioassays, MATC's of lead for rainbow trout in hard water were between 18.2 and 31.7 μg l⁻¹ dissolved lead vs 120–360 μg l⁻¹ total lead. In soft water, where exposure to lead was initiated at the eyed egg stage of development, the MATC was between 4.1 and 7.6 μg l⁻¹. With exposure to lead beginning after hatching and swim-up of fry, the MATC was between 7.2 and 14.6 μg l⁻¹. Therefore, fish were more sensitive to the effects of lead when exposed as eggs.