Zinc Wastes Research Articles

Physical and Chemical Fundamentals and Technical Solutions for Recovery of Non-ferrous and Rare Metals from Industrial Wastes


 
 
 The increasing demand for zinc and a range of zinc-related metals (for example: lead; indium; tin; cadmium; and copper) in the Russian Federation cannot be satisfied by the existing production plants due to the lack of raw materials. At the same time, ferrous and non-ferrous metallurgy and the chemical industry have accumulated hundreds of millions of tons of zinc wastes (falling into the hazard categories 2 to 4), the processing of which could not only make up the raw material base, but also improve the environmental situation. In the world, over 85% of ferrous dust is recycled using the Waelz process. The Waeltz process is used for distilling separation of elements under reducing conditions. In this study, a block diagram for production of the following elements from industrial wastes is proposed: zinc, cadmium and indium in form of massive metals; zinc and indium in the form of fine powders; and clinker as a raw material for cement production. The technical and scientific details of this new process have been patented in the Russian Federation and abroad. For the first time, the following operations have been implemented with the use of large-sized Waelz kilns: vapour-oxidized Waeltz treatment of polymetallic wastes; recycling of heat from gases and solid products with generation of process fumes; and implementation of alternative flux (dolomite) and alternative fuel (petroleum coke).
 Keywords: Waelz process, industrial wastes, heat recycling, vapour-oxidized Waelz processing
 
 

Nodulation of Retama monosperma by Ensifer aridi in an Abandonned Lead Mine Soils in Eastern Morocco.

Millions tons of lead and zinc wastes from the abandoned Touissit mine are stored in the open air as dikes in the vicinity of the villages in Eastern Morocco and pose a real danger to both the environment and local populations. To prevent the movement of minerals to the nearby villages and limit the damages to the environment and health, we proposed the nitrogen-fixing leguminous shrub Retama monosperma, as a model plant to use for phytostabilization experimentations. This plant species is known by its ability to grow in hard climatic conditions and in heavy metals contaminated soils. The isolation of bacterial strains nodulating R. monosperma in the abandoned mine soils will permit the selection of rhizobia to inoculate young plant seedlings before their use for the phytostabilization of the mine tailings. In this work, 44 bacteria were isolated from the root nodules of R. Monosperma grown in the Touissit abandoned mine. Twenty-four isolates were considered as true rhizobia as they possess a copy of the nodC symbiotic gene and were able to renodulate their original host. The phenotypic characterization showed that all the strains are tolerant in vitro to different concentrations of heavy metals. The analysis of the 16S rRNA sequences of two selected representative strains showed they were related to different strains of Ensifer aridi isolated from different legumes in three continents deserts. The glnII, recA, and gyrB housekeeping genes analysis confirmed the affiliation of the strains to E. aridi. Moreover, the phylogenic analysis of nodA, nodC, and nifH symbiotic genes showed that the strains are more related to E. aridi JNVUTP6 species isolated from Tephrosia purpurea root nodules in the Thar Desert in India. To our knowledge, this is the first report about the isolation of E. aridi from R. monosperma root nodules.

Metal content in fruit-bodies and mycorrhizas of Pisolithus arrhizus from zinc wastes in Poland

<i>Pisolithus arrhizus</i> has been selected for investigation as one of the ectomycorrhizal species most resistant to stress factors. Metal content in fruit-bodies and mycorrhizas was estimated to evaluate their role as bioindicators and to check whether mycorrhizas have any special properties for heavy metal accumulation. Fruit-bodies and mycorrhizas were collected from zinc wastes in Katowice-Wełnowiec and analyzed using conventional atomic absorption spectroscopy and energy dispersive spectroscopy accompanying scanning electron microscopy. Differences in tendencies to accumulate metals within sporophores and mycorrhizas were found. The fruit-bodies accumulated Al (up to 640 µg g<sup>-1</sup>), while high concentrations of Al, Zn, Fe, Ca and Si were noted in the outer mantle of the mycorrhizas. in the material secreted and in the mycelium wali. The content of elements varied depending on the agę of mycorrhizas. The ability of extramatrical mycelium and hyphae forming mycorrhizal mantle to immobilize potentially toxic elements might indicate biofiltering properties though thc next step should include investigations on ability of the fungus to prevent element uptake by the plant.

Heavy metal content and localization in mycorrhizal Euphorbia cyparissias zinc wastes in southern Poland

Arbuscular mycorrhiza (AM) development, heavy metal uptake by the plant and localization of heavy metals within plant and AM fungal structures, has been investigated in <em>Euphorbia cyparissias</em> collected from zinc wastes in Poland and from two other stands differing in soil parameters. The plant was selected on the basis of preliminary research on mycorrhiza of plants colonizing zinc wastes. <em>E. cyparissias</em> was strongly mycorrhizal and arbuscules were abundant except at the very beginning of the vegetation period. Light microscopy after rhodizoniate staining and SEM equiped with an EDS system have been used to localize heavy metals within the fungal mycelium and mycorrhizal roots. About 80% of the total intraradical mycelium show an increased content of heavy metals in comparison to the remaining 20% where heavy metals were under detection limit. At the same time the number of arbuscules formed by mycelium stained by rhodizoniate is slightly lower than in mycelium containing a low level of these elements. Using the rhodizoniate staining lead was found in epidermal cell walls, root hairs, in mycorrhizal mycelium and in crystaloids deposited within latex and inside cortical cells, around fungal hyphae. SEM observations with EDS system confirmed that these crystaloid depositions contained higher concentrations of Zn than root cell wall and fungal structures.

Arbuscular mycorrhiza and plant succesion on zinc smelter spoil heap in Katowice-Wełnowiec

Mycorrhizal status of plants colonising the zinc wastes in Katowice was surveyed. In total 69 vascular plant species (25 families) appearing on the investigated area have been noted. More than 60% of them were mycorrhizal. Non-mycorrhizal species, such as <em>Cardaminopsis arenosa</em> and <em>Silene vulgaris</em> dominated the early successional part of the zinc heap. <em>Tussilago farfara</em> was the only AM plant there, however, no arbuscules were developed at this stage. The number of AM species was increased on the 20 years old part of the zinc wastes and on the older 30-50 years old areas. AM plants constituted about 60% of the total number of species there. The frequency of particular AM species was the highest on the oldest part of the investigated area. The usefulness of the results for restoration practices was discussed.

Heavy metal binding properties of Pinus sylvestris mycorrhizas from industrial wastes

Mycorrhizas of <em>Pinus sylvestris</em>, collected from zinc wastes in Poland and France were investigated using transmission electron microscope (TEM) and scanning electron microscope (SEM) equipped with energy dispersion spectroscopy (EDS) and electron energy loss spectroscopy (EELS). At both sites, mycorrhizas of <em>Hebeloma</em> were the most frequent, however, they were often characterised by a sparse or only locally developed fungal mantle. Mycorrhizas formed by suilloid fungi were much less frequent, and usually produced a clearly defined fungal mantle characterised by abundant formation of pigments and crystals covering the hyphae of the outer mantle. These two groups of mycorrhizas differed in their heavy metal binding properties. A biofiltering effect of Pb and Zn by the fungal mantle was observed only in the case of suilloid mycorrhizas, which represented up to 10% of the total number of mycorrhizas. No statistical differences between the mantle, the cortical cell walls and the vascular tissue were demonstrated in mycorrhizas formed by other fungi dominating on industrial wastes. In the case of <em>Hebeloma</em> and <em>Inocybe</em>, however, elements such as Cu and Cd were present in higher amounts in the extra-matrical mycelium, whereas no or only low amounts of these elements were detected within fungal mantles, mainly in mycorrhizas from the French waste. Analysis of the root systems has shown relatively high percentage of nonmycorrhizal short roots, suggesting the inhibition of mycorrhiza formation or a decreased number of mycorrhizal propagules. The role of dead roots and mycorrhizas in biosorption and immobilization of heavy metals was discussed.

Arbuscular mycorrhiza of introduced and native grasses colonizing zinc wastes: implications for restoration practices

The analysis of mycorrhizal status of grasses introduced under conventional phytoremediation programmes (including covering of the waste area with a layer of uncontaminated soil and watering) and of grasses that spontaneously established in later successional stages, was carried out on the slopes of the 1- to 30-year-old tailings of ZG Trzebionka Mining Company located near Chrzanow (southern Poland). Most grasses were mycorrhizal and the parameters of mycorrhization were higher on the older parts of the waste. Grasses selected for restoration practices were well developed only if the waste was covered with a layer of soil and continuous irrigation took place, both being expensive practices. The field experiment showed that the introduction of standard inoculum containing mycorrhizal fungi indeed improved the development of grasses during early stages, but still was not effective enough due to high erosion of the substratum. A slight improvement was observed when AgroHydroGel was used to lock moisture in the soil, but the plants did not survive for longer time periods. On the contrary, much better results were obtained when vegetatively multiplied grasses selected from specimens originating from natural succession were used to stabilize the vegetation on the bare industrial waste.

Accumulation of copper by Acremonium pinkertoniae, a fungus isolated from industrial wastes

Acremonium pinkertoniae isolated from zinc wastes was studied to understand the mechanisms that allow living organisms to thrive in polluted environments and the possible role of the fungus in the redistribution and cycling of copper. The fungus was cultured on solid media supplemented with copper sulfate at increasing concentrations. At high doses it was observed that the mycelia acquired a characteristic blue color. This was accompanied by morphological changes and the formation of crystalloid structures within thickened cell walls. The material was further analysed with EDX, X-ray powder diffraction and IR spectroscopy. It was demonstrated that A. pinkertoniae is able to accumulate over 20% dry weight of copper by what probably is a chitin-glucan complex.

Effectiveness of arbuscular mycorrhizal fungal (AMF) strains in colonisation of plants involved in phytostabilisation of zinc wastes

The effectiveness of mycorrhizal colonisation of four fungal isolates of different origin was tested in roots of Festuca rubra L. and Plantago lanceolata L. cultivated on three zinc waste substrata of different toxicity. F. rubra showed a much better survival rate than P. lanceolata. The effectiveness of mycorrhizal colonisation varied between the fungal isolates introduced. The highest values of the mycorrhizal parameters were found in roots inoculated with the Glomus claroideum strain originating from the industrial waste. Arbuscular richness, assessed in roots stained for viable fungal structures, was demonstrated to be the most sensitive parameter, showing statistically important differences between plants, artificially inoculated and those colonised only by the indigenous mycorrhizal fungi. This parameter was also useful to compare the substrata concerning their toxicity, and the results of the viability tests correlated well with the “availability” of the heavy metals.

Nuclear microprobe studies of elemental distribution in seeds of Biscutella laevigata L. from zinc wastes in Olkusz, Poland

Biscutella laevigata L. ( Brassicaceae), a rare perennial metallophyte plant species known mainly from Central and Southern Europe, has a very restricted distribution in Poland. This investigation focuses on one known Polish lowland location of B. laevigata on zinc dumps near Olkusz, Upper Silesia. The results presented are a continuation of earlier studies, undertaken to understand mechanisms of plant adaptation to a hostile environment, rich in heavy metals. The analyses were performed with 3.0 MeV protons, using the National Accelerator Centre (NAC) nuclear microprobe. Two complementary techniques, proton-induced X-ray emission (PIXE) and proton backscattering spectrometry (BS), were simultaneously used. Quantitative elemental maps showed that seed tissue was defined by specific elemental allocation patterns. The highest concentration of Zn and other heavy metals was found in the endosperm. Within embryonic tissue, the highest amount of Zn was found in the radicle. Mapping artefacts, related to specimen shape, are discussed. The results show that plants strictly and actively select elements and their amounts taken up by different tissues. This mechanism is probably responsible for their survival.

Heavy metal distribution in Suillus luteus mycorrhizas – as revealed by micro-PIXE analysis

Suillus luteus/Pinus sylvestris mycorrhizas, collected from zinc wastes in Southern Poland, were selected as potential biofilters on the basis of earlier studies carried out with energy dispersive spectrometry (EDS) microanalytical system coupled to scanning electron microscope (SEM) and transmission electron microscope (TEM). Using the National Accelerator Centre (NAC) nuclear microprobe, elemental concentrations in the ectomycorrhiza parts were for the first time estimated quantitatively. Micro-proton-induced X-ray emission (PIXE) true elemental maps from freeze-dried and chemically fixed mycorrhizas revealed strong accumulation of Ca, Fe, Zn and Pb within the fungal mantle and in the rhizomorph. Vascular tissue was enriched with P, S and K, while high concentrations of Si and Cl were present in the endodermis. Cu was the only element showing elevated concentrations in the cortex region. Elemental losses and redistributions were found in mycorrhizas prepared by chemical fixation. Some problems related to elemental imaging are discussed.

Identification of arbuscular mycorrhizal fungi in soils and roots of plants colonizing zinc wastes in southern Poland

Analysis of the community of arbuscular mycorrhizal (AM) fungi in roots of Fragaria vesca growing in a heavy metal contaminated site was carried out on a Zn waste site near Chrzanow (southern Poland). The waste substratum was characterized by high contents of Pb, Zn, Cd, Cu and As, and by low levels of N, P and organic matter. Spores of Glomales were isolated by wet sieving and DNA was isolated from individual spores. Nested polymerase chain reaction (PCR) with taxon-specific primers was used to identify the species Glomus mosseae, Glomus intraradices and Glomus claroideum. Spores of other fungi were morphologically characterized and new taxon-discriminating molecular probes were developed for two of them (Glomus sp. HM-CL4 and HM-CL5) based on variations in the large ribosomal subunit (25S rDNA). High sequence similarities were found between Glomus sp. HM-CL4 and Glomus gerdemanii, and between Glomus sp. HM-CL5 and Glomus occultum. The designed primers were used to characterize the population of AM fungi colonizing the roots of F. vesca collected from the Zn waste site. The analysis, carried out on roots stained with trypan blue, showed that the most effective colonizer was closely related to G. gerdemannii. G. claroideum and the G. occultum-like fungus were slightly less common whilst frequencies of G. intraradices and G. mosseae in roots were much lower. The analysis of mycorrhiza stained with rhodizoniate to localize heavy metal accumulation showed that the stain does not influence the PCR reaction. Seventy percent of the root samples containing positively stained fungal hyphae were found to be colonized by G. mosseae. The data obtained demonstrate the usefulness of nested PCR for studies carried out in polluted areas. It will enable selection of AM fungi which are able to colonize plant roots under heavy metal stress conditions, as well as the identification of fungi showing high in situ accumulation of potentially toxic elements.