• Energy Research

Abstract The purpose of the study was to evaluate the possibility of removing heavy metal cations from single-metal spiked soil samples, which were pretreated with nanoscale zero-valent iron (nZVI) particles. Sandy soil was artificially contaminated with copper (Cu), cadmium (Cd), nickel (Ni), and lead (Pb). Contaminated soil samples were amended with different doses of nZVI (0.35, 0.70 and 1.05 %). A sequential extraction method was used to determine the fractionation of heavy metal cations in the control and nZVI amended soil samples. A solution of 0.1 M acetic acid (pH 3.0) was used to investigate the removal of heavy metals from control and nZVI-amended soil samples. The results showed that nZVI reduced the amount of metals in the exchangeable form and increased the proportion of these metals associated with amorphous iron (Fe) oxides. The results also showed that the removal efficiencies of heavy metals increased with increasing nZVI dose, that is, from 46.9 %, 5.77 %, 33.5 %, and 2.70 % to 55.9 %, 12.3 %, 46.2 %, and 3.79 % for Cd, Cu, Ni, and Pb, respectively. The study indicated that the application of nZVI in soil could be beneficial for subsequent removal of heavy metals from soil using 0.1 M acetic acid solution.

The aim of this research is to determine metal leaching from concrete specimens containing different quantities of waste recovered from copper indium selenide (CIS) solar module by replacing a certain share of sand aggregate. During the first stage of research the CIS solar module was shredded and leaching tests were performed on recovered waste by analysing six metals – Na, Mg, Fe, Cd, Cu and Zn. It has been determined that out of all metals analysed, the highest leaching was observed for sodium, while the highest leaching out of the heavy metals was found for zinc. In Phase II of the study concrete specimens with shredded CIS module waste were made and the physical properties of these specimens as well as the leaching of the same metals was determined. The results have shown that three metals, namely Fe, Cd, Zn, were successfully immobilised and did not leach from the specimens.

Abstract In this study, a commercial aqueous dispersion of nZVI was applied for the removal of Cd(II), Cu(II), Ni(II), and Pb(II) ions from their aqueous solutions. The removal efficiency was studied using two mass ratios of nZVI to heavy metal: 7–9:1 and 140–180:1. In the first case, the capacities of heavy metals removal were found to be 79.33–102.00 mg per g of nZVI for Cd, 111.11-142.85 mg per g of nZVI for Cu, 107.30–137.96 mg per g of nZVI for Ni, and 110.97–142.68 mg per g of nZVI for Pb. In this treatment, nanoparticles formed larger structures with heavy metals and they were easily removed from water by filtration. In the second case, the removal efficiencies of heavy metals were lower. There were more discrete nanoparticles that not formed larger structures and could not be easily filtered. In this treatment, the acidification of the filtered solutions caused the formation of deposits and subsequent re-dissolution of some heavy metals back to solutions.

Sewage sludge was treated with nanoscale zero-valent iron (nZVI) to enhance biogas and methane (CH4) production, and the influence of key parameters on the material’s anaerobic digestion (AD) efficiency was analyzed using sigmoidal mathematical models. In this study, three dosages of nZVI (0.5%, 1.5% and 3%) were added to the anaerobic sludge digestion system to enhance and accelerate the sludge decomposition process. The results showed that cumulative biogas yield after 41 days of digestion increased by 23.9% in the reactor with a nZVI dosage of 1.5%. Correspondingly, the highest CH4 production enhancement by 21.5% was achieved with a nZVI dosage of 1.5% compared to the control. The results indicated that this nZVI dosage was optimal for the AD system, as it governed the highest biogas and CH4 yields and maximum removal of total and volatile solids. Additionally, to predict biogas and CH4 yields and evaluate kinetic parameters, eight kinetic models were applied. According to the results of the modified Gompertz, Richards and logistic models, the nZVI dosage of 1.5% shortened the biogas lag phase from 11 to 5 days compared to the control. The Schnute model provided the best fit to the experimental biogas and CH4 data due to highest coefficients of determination (R2: 0.9997–0.9999 at 1.5% and 3% nZVI dosages), as well as the lowest Akaike’s Information Criterion values and errors. This demonstrated its superior performance compared to other models.

In the present study, we aimed to determine the changes of indoor radon concentrations depending on various environmental parameters, such as the outdoor temperature, relative humidity, and air pressure, in university building premises of different applications and heights. The environmental parameters and indoor radon concentrations in four different premises were measured each working day over an eight-month period. The results showed that the indoor radon levels strongly depended on the outside temperature and outside relative humidity, whereas the weakest correlations were found between the indoor radon levels and indoor and outdoor air pressures. The obtained indoor radon concentration and environmental condition correlations were different for the different premises of the building. That is, in two premises where the ventilation effect through unintentional air leakage points prevailed in winter, positive correlations between the radon concentration and outside temperature were obtained, reaching the values of 0.94 and 0.92, respectively. In premises with better airtightness, negative correlations (R = −0.96 and R = −0.62) between the radon concentrations and outside temperature were obtained. The results revealed that high quality air isolation in premises could be an important factor for higher indoor radon levels during summer compared to winter.