Processes of removing zinc from water using zero-valent iron

Zero-valent iron has received considerable attention for its potential application in the removal of heavy metals from water. This paper considers the possibility of removal of zinc ions from water by causing precipitates to form on the surface of iron. The chemical states and the atomic concentrations of solids which have formed on the surface of zero-valent iron as well as the type of the deposited polycrystalline substances have been analyzed with the use of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The BET surface area, the pH at point of zero charge (pHPZC), the ORP of the solutions, and the pH and chemical concentrations in the solutions have also been measured. Furthermore, the paper also considers the possibility of release of zinc from the precipitates to demineralised water in changing physicochemical and chemical conditions. In a wide range of pH values, Zn x Fe3 − x O4 (where x ≤ 1) was the main compound resulting from the removal of zinc in ionic form from water. In neutral and alkaline conditions, the adsorption occurred as an additional process

Processes of Removing Zinc from Water using Zero-Valent Iron

Zero-valent iron has received considerable attention for its potential application in the removal of heavy metals from water. This paper considers the possibility of removal of zinc ions from water by causing precipitates to form on the surface of iron. The chemical states and the atomic concentrations of solids which have formed on the surface of zero-valent iron as well as the type of the deposited polycrystalline substances have been analyzed with the use of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The BET surface area, the pH at point of zero charge (pH(PZC)), the ORP of the solutions, and the pH and chemical concentrations in the solutions have also been measured. Furthermore, the paper also considers the possibility of release of zinc from the precipitates to demineralised water in changing physicochemical and chemical conditions. In a wide range of pH values, Zn(x)Fe(3 − x)O(4) (where x ≤ 1) was the main compound resulting from the removal of zinc in ionic form from water. In neutral and alkaline conditions, the adsorption occurred as an additional process

Reactivity of nZVI in the removal of Cu(II) and Zn(II) from synthetic mine drainage

Adsorption properties, including isotherms and kinetics, of nano zero-valent iron (nZVI) for Cu(II) and Zn(II) removal from synthetic mine drainage were evaluated in batch tests. The influence of contact time, nZVI doses, pH, ionic strength, temperature, and concentration on nZVI adsorption properties was assessed. The removal of Cu(II) and Zn(II) increased with pH from 3 to 7 and then stabilized up to pH 10. Moreover, the increased Cu(II) adsorption capacity upon increasing temperature and a positive enthalpy change (ΔH) indicate that the adsorption process is endothermic. The results also showed that the adsorption equilibrium for Cu(II) and Zn(II) was achieved after 50 and 30 min, respectively. Kinetics were best described by a pseudo-nth order model, with the order of sorption of 2.231 and 1.363, and the rate constants of 0.0008 and 0.0679 mg1-n·gn-1/min, for Cu(II) and Zn(II), respectively. The correlation between the amount of metals adsorbed on nZVI surface and the residual amount of metals in water during isothermal tests was best described by the nonlinear Sips model. Using this model, high q maxS were found: 286.6 mg/g and 142.6 mg/g, for Cu(II) and Zn(II), respectively, as indication of their high sorption capacity

Impact of spiral separator geometrical parameters on the density separation of various fine-grained materials

The study aims at the assessment of the impact of geometrical parameters of spiral separators on the efficiency of density separation of fine-grained materials. Experiments were carried out on three spiral separators: Krebs 2.85, Reichert LD-4 and Reichert LG-7. Three materials were used for the tests: raw coal, coal waste and mix of sand and magnetite as the model material. Results of raw coal and coal waste upgrading showed that density separation was most efficient in Reichert LD-4 spiral. This is due to the fact that this device had the highest amount of coils, height of sluice as well as was equipped with additional dense product collector and additional water sluice for transport water. The lower slope of sluice and larger height made separation even more efficient. Analysis of separation of model material, that is the mix of sand and magnetite, showed that in this case the existence of additional water sluice does not have an impact on product separation and best results were obtained in the Reichert LG-7 spiral separator. The shape and width of sluices did not have a significant impact on the separation process

Stability of green tea nanoscale zero-valent iron

Colloidal suspension of nano zero-valent iron (nZVI), obtained as a result of mixing green tea (GT) solution with iron solutions (FeCl2 and FeSO4 separately to form two suspensions: GT-nZVIFeCl2 and GT-nZVIFeSO4) was assessed in terms of stability. The particles of suspensions had a tendency rapidly aggregation to form larger aggregates, and then settled. The absolute value of zeta potential (ζ) of suspensions did not exceed 17 mV. To prevent the aggregation of nZVI particles, the pHs were changed by the addition of Na2CO3 to obtain higher values of ζ. For both suspensions, the zeta potential at a satisfactory level was obtained at pH values higher than 7.5. Then, the potential was lower than −40 mV for GT-nZVIFeCl2 and lower than −25mV for GT-nZVIFeSO4. This means that the first suspension had a better stability than second. The isoelectric point (IEP) of GT-nZVIFeCl2 was in the range from 4.5 to 5, while in the case of GT-nZVIFeSO4 all measured ζ were negative. To investigate the effect of increased ionic strength (IS) on the stability of suspensions at different pH values, NaCl and MgSO4 were added to the irons solutions. The final IS in the GT-nZVI was 12 mM. In both of the suspensions the absolute values of ζ were lower than previous and were about 25 and 20 mV, for GT-nZVIFeCl2 and GT-nZVIFeSO4, respectively

Impact of spiral separator geometrical parameters on the density separation of various fine-grained materials

The study aims at the assessment of the impact of geometrical parameters of spiral separators on the efficiency of density separation of fine-grained materials. Experiments were carried out on three spiral separators: Krebs 2.85, Reichert LD-4 and Reichert LG-7. Three materials were used for the tests: raw coal, coal waste and mix of sand and magnetite as the model material. Results of raw coal and coal waste upgrading showed that density separation was most efficient in Reichert LD-4 spiral. This is due to the fact that this device had the highest amount of coils, height of sluice as well as was equipped with additional dense product collector and additional water sluice for transport water. The lower slope of sluice and larger height made separation even more efficient. Analysis of separation of model material, that is the mix of sand and magnetite, showed that in this case the existence of additional water sluice does not have an impact on product separation and best results were obtained in the Reichert LG-7 spiral separator. The shape and width of sluices did not have a significant impact on the separation process

Stability of green tea nanoscale zero-valent iron

Colloidal suspension of nano zero-valent iron (nZVI), obtained as a result of mixing green tea (GT) solution with iron solutions (FeCl2 and FeSO4 separately to form two suspensions: GT-nZVIFeCl2 and GT-nZVIFeSO4) was assessed in terms of stability. The particles of suspensions had a tendency rapidly aggregation to form larger aggregates, and then settled. The absolute value of zeta potential (ζ) of suspensions did not exceed 17 mV. To prevent the aggregation of nZVI particles, the pHs were changed by the addition of Na2CO3 to obtain higher values of ζ. For both suspensions, the zeta potential at a satisfactory level was obtained at pH values higher than 7.5. Then, the potential was lower than −40 mV for GT-nZVIFeCl2 and lower than −25mV for GT-nZVIFeSO4. This means that the first suspension had a better stability than second. The isoelectric point (IEP) of GT-nZVIFeCl2 was in the range from 4.5 to 5, while in the case of GT-nZVIFeSO4 all measured ζ were negative. To investigate the effect of increased ionic strength (IS) on the stability of suspensions at different pH values, NaCl and MgSO4 were added to the irons solutions. The final IS in the GT-nZVI was 12 mM. In both of the suspensions the absolute values of ζ were lower than previous and were about 25 and 20 mV, for GT-nZVIFeCl2 and GT-nZVIFeSO4, respectively

Testing the possibility of leaching salt debris obtained from underground excavations

For many years, the Salt Mine in Bochnia has conducted the extraction and restructuring of underground working to obtain new touristic routes. The works generate a large amount of rock salt material, colloquially called “salt debris”, containing a large part of silty minerals. Due to the large concentration of NaCl which constitutes a threat to the environment, the salt debris may only be stored at hazardous material dumps. This is why the mine works towards the industrial use of the material. Currently, the debris is used to produce a stabilizing backfill mixture that is used for filling the liquidated “Moszczenica” shaft. The liquidation shall be completed in the beginning of 2018 and to continue the management of the salt debris, the mine plans to leach it in a newly constructed system and the saturated brine obtained in the process shall be introduced to underground workings. The paper presents the results of semi-industrial tests of leaching intensity of salt debris, depending on the graining and the time taken by the process. The tests were conducted for three grain classes of the salt debris (0-6, 0-10 and 0-20 mm), at a temperature of 15 °C. The kinetic models of the process has been presented for the obtained results. The obtained results shall be used for the optimization of the operation of the future industrial system and shall be treated as input data for the automation control system

Ocena zastosowania flotacji w odzysku metali z rozdrobnionych płyt obwodów drukowanych

The paper presents an assessment of flotation efficiency in the separation of plastics from metals derived from printed circuit boards (PCBs). The PCBs were ground in a knife mill prior to flotation. The contact angles of various materials corresponding to the grains from ground PCBs were measured, and a series of flotation tests was carried out to obtain the best product. The impact of the following parameters were investigated: the reagent and its dose, the airflow rate through the flotation tank and the feed concentration. The highest efficiency of metal recovery from PCBs was achieved for Dimethoxy dipropyleneglycol at a concentration of 157 mg/dm3 and with an airflow of 200 dm3/h and a feed concentration of <50 g/dm3. In the hydrophilic product (concentrate), it was mainly Cu (40%) and Sn (7.8%) that were identified by means of XRF, but there were also trace amounts of precious metals such as Au (0.024%), Ag (0.5797%) and Pd (149 ppm). Impurities in the form of Si (5%), Ca (3.2) and Br (2.1) were also identified in this product. Small amounts of metals in their metallic form were identified in the hydrophobic product (waste), mainly Cu (2.3), Al (1.7) and Sn (1.1). As a result of the research, high recovery ratios were obtained for Cu (93%), Sn (84), Ag (83) and Au (69). The purity of obtained metal concentrate with this method was lower in comparison with the other methods of the recovery of metals from ground PCBs for the same feed, i.e. electrostatic or gravity separation. Also considering other factors such as the environmental impact of the flotation process, the number of facilities and their energy consumption, this process should not be used in the developed metal recovery technology. Using electrostatic separation for the same feed obtained much better results.W artykule przedstawiono ocenę zastosowania flotacji do rozdziału metali od tworzyw sztucznych z rozdrobnionych w młynie nożowym płyt obwodów drukowanych (PCBs). Zmierzono kąty zwilżania różnych materiałów odpowiadających ziarnom zmielonych PCBs oraz określono wypływy odczynników i ich stężeń, wydatków powietrza oraz zagęszczenia materiału na sprawność procesu flotacji. Najwyższą sprawność odzysku metali z PCBs uzyskano przy zastosowaniu eteru dimetylowego glikolu dipropylenowego w stężeniu 157 mg/dm3, wydatku powietrza 200 dm3/h i zagęszczeniu materiału poniżej 50 g/dm3. W produkcie hydrofilowym (metalach), wykorzystując metodę XRF, zidentyfikowano głównie Cu (40%) i Sn (7,8%) oraz śladowe ilości metali szlachetnych takich jak Au (0,024%), Ag (0,5797%) i Pd (0,015%). W produkcie tym rozpoznano również zanieczyszczenia takie jak Si (5%), Ca (3,2%) i Br (2,1%). W produkcie hydrofobowym (tworzywach sztucznych) występowały nieznaczne ilości metali, głównie były to Cu (2,3%), Al (1,7%) i Sn (1,1%). W wyniku przeprowadzonych badań uzyskano wysokie wskaźniki odzysku dla Cu (93%), Sn (84%), Ag (83%) i Au (69%). Niemniej jednak, w porównaniu do separacji elektrostatycznej, która była prowadzona dla tej samej nadawy, czystość produktów uzyskanych za pomocą flotacji była mniejsza. Biorąc pod uwagę również inne czynniki, między innymi takie jak oddziaływanie procesu flotacji na środowisko naturalne, ilość urządzeń oraz ich energochłonność, stwierdzono w konkluzji artykułu, że proces ten nie powinien być stosowany w tworzonej technologii odzysku metali z PCBs. Znacznie lepsze efekty rozdziału uzyskano bowiem dla tej samej nadawy, stosując proces separacji elektrostatyczny, który ma niewielki wpływ na środowisko przyrodnicze, a powstające produkty mogą być w pełni wykorzystywane

The sorption of metal ions on nanoscale zero-valent iron

The injection of the colloidal suspensions of nano-iron (nZVI) into an aquifer is a novel method of removing metal ions from acidic water. In the batch tests, the equilibrium study of the sorption of metal ions, Cu(II) and Zn(II), on Green Tea nanoscale Zero-Valent Ion (GT-nZVI) was carried out. The sorption of metal ions on this reactive material was described using the Langmuir, Freundlich and Sips models. This last model described in a better way the sorption equilibrium in the tested range of concentrations and temperature. The value of determination coefficient (R2) for the Sips model, for copper and zinc, was 0.9735 to 0.9995, respectively. GT-nZVI has very good properties in removing Cu(II) and Zn(II) from acidic water. The high values of qmaxS, the maximum adsorption capacity in the Sips model, amounting to 348.0 and 267.3 mg/g for Cu(II) and Zn(II), indicate the high adsorption capacity of GT-nZVI. The analyzed metals have good or very good affinity with GT-nZVI