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1

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

Suponik Tomasz, Neculita Carmen Mihaela

Environment Protection Engineering

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2021

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Vol. 47, nr 2

93--108

EN

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.

2

Chemical degradation of PCDD/F in contaminated sediment

Hrabák P., Homolková M., Wacławek S., Černík M.

Ecological Chemistry and Engineering. S

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2016

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Vol. 23, nr 3

473--482

EN

Due to the extreme toxicity of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), the remediation of PCDD/F aquifer source zones is greatly needed; however, it is very difficult due to their persistence and recalcitrance. The potential degradability of PCDD/F bound to a real matrix was studied in five systems: iron in a high oxidation state (ferrate), zero-valent iron nanoparticles (nZVI), palladium nanopowder (Pd), a combination of nZVI and Pd, and persulfate (PSF). The results were expressed by comparing the total toxicity of treated and untreated samples. This was done by weighting the concentrations of congeners (determined using a standardized GC/HRMS technique) by their defined toxicity equivalent factors (TEF). The results indicated that only PSF was able to significantly degrade PCDD/F. Toxicity in the system decreased by 65% after PSF treatment. Thus, we conclude that PSF may be a potential solution for in-situ remediation of soil and groundwater at PCDD/F contaminated sites.

3

Arsenic immobilization by nanoscale zero-valent iron

Rodová A., Filip J., Černík M.

Ecological Chemistry and Engineering. S

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2015

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Vol. 22, nr 1

45--59

EN

Contaminated mine water from the Kank site (Czech Republic) containing arsenic at a concentration of approximately 85 mg/dm3 was tested in a reaction with elemental iron nanoparticles. In a reductive environment there was a reduction of As to the more soluble and toxic form of As(III) depending on the pH of the solution. Oxidation of elemental iron creates oxyhydroxides which incorporate As into their structure in the form of mixed complexes and thereby remove and bind dissolved As from the solution. The addition of 0.5 g/dm3 nZVI to the contaminated water leads to a significant decrease in ORP and concentrations of As to around the detection limit. The pH of the solution is not significantly affected by the addition of nZVI. The main competing anion for co-precipitation is represented by phosphates whose concentration after the addition of nZVI was reduced to 6.5% of the original value. The resulting precipitates were analyzed by XPS, XRF, XRD, SEM-EDX and Mössbauer spectroscopy. The presence of jarosite, Schwertmannite and also arsenic probably in the form of skorodite was confirmed.

PL

W Kaňk (Czeska Republika) znajduje się zanieczyszczona woda z kopalni, zawierająca arsen o przybliżonym stężeniu 85 mg/dm3. Została ona poddana reakcji z nanocząteczkami żelaza na zerowym stopniu utlenienia (nZVI). W zależności od pH roztworu w środowisku redukcyjnym przebiegła reakcja redukcji As do bardziej rozpuszczalnej i toksycznej formy As(III). Poprzez utlenienie elementarnego żelaza powstają tlenowodorotlenki, łączące się z As w postać kompleksów mieszanych, tym samym usuwając As z zanieczyszczonego roztworu. Dodatek 0,5 g/dm3 nZVI do zanieczyszczonej wody prowadzi do znaczącego spadku wartości ORP i obniżenia stężenia As do granic wykrywalności. Dodatek nZVI nie ma znaczącego wpływu na wartość pH roztworu. Głównym anionem konkurującym we współstrąceniu As jest anion fosforanowy, którego stężenie po dodaniu nZVI zmniejszyło się do 6,5% w porównaniu do wartości wyjściowej. Powstały osad został poddany analizie metodami: XPS XRF, XRD, SEM-EDX i spektroskopią Mössbauerowską. Została potwierdzona obecność jarosytu, schwertmannitu oraz arsenu prawdopodobnie w postaci skorodytu.

4

In-Situ Combination of Bio and Abio Remediation of Chlorinated Ethenes

Lacinová L., Černíková M., Hrabal J., Černík M.

Ecological Chemistry and Engineering. S

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2013

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Vol. 20, nr 3

463--473

EN

This article deals with combined abio-bioreductive methods for in-situ removal of chlorinated ethenes. The method is based on the use of bioremediation supported by lactate and chemical reduction using nZVI. The method is compared with the use of the individual methods alone, mainly with nZVI. In an environment with very low permeability a poor contaminant removal efficiency was achieved during repeated application of nZVI (about 50% of the original content of contamination). Separate application of lactate resulted in conversion of PCE to 1,2-cis-DCE, whose degradation occurred very slowly. When using the combined abio-bioreductive method, based on consecutive application of lactates and nZVI, over 75% of the original content of contamination was removed. This article discusses not only the changes in concentrations of contaminants but also pH and ORP. Both methods are also compared from an economic point of view.

PL

Przedstawiono metodę abio-bioredukcji usuwania in-situ chlorowanych etenów. Metoda ta polega na połączeniu bioremediacji, wykorzystującej redukcję mleczanu, i metody chemicznej nZVI. Wyniki tych badań porównano z danymi otrzymanymi z wykorzystaniem jedynie metody chemicznej. W środowisku o bardzo małej przepuszczalności uzyskano stosunkowo niską skuteczność usuwania zanieczyszczeń podczas wielokrotnego stosowania nZVI (około 50% pierwotnej zawartości zanieczyszczeń). Oddzielna aplikacja mleczanu spowodowała konwersję PCE do 1,2-cis-DCE, którego degradacja następowała bardzo powoli. Przy użyciu połączonej metody abio-bioredukcji, opartej na stosowaniu kolejno mleczanów i nZVI, usunięto ponad 75% pierwotnej zawartości zanieczyszczeń. W artykule omówiono nie tylko zmiany w stężeniu zanieczyszczeń, ale również pH i ORP. Oba sposoby porównano również pod względem ekonomicznym.