Soil pollution with hydrocarbons is a consequence of activities associated with the petroleum industry and related sectors. The effects of petroleum pollution are devastating, making the remediation of contaminated sites imperative. Consequently, soil decontamination represents a significant and costly challenge for the petroleum industry. The article proposes a dual-recovery bioremediation solution that is both efficient and cost-effective, exploring the potential use of dehydrated sewage sludge from municipal wastewater treatment plants to treat petroleum-contaminated soils. Over the three-month bioremediation experiment, changes in the density of indigenous bacteria in petroleum-contaminated soil samples, treated or untreated with sludge, were monitored along with the reduction in petroleum hydrocarbon concentrations. In parallel, the evolution of other contaminants, such as heavy metals, was monitored during the bioremediation experiment. Geotechnical tests were also conducted to evaluate the feasibility of returning the treated soil to its original location after the bioremediation experiment. Our results demonstrate that the proposed method effectively addresses both the remediation of petroleum-contaminated soils (hazardous waste) and the reuse of sewage sludge from municipal wastewater treatment plants.

Romania has some huge ferrous slag stockpiles that are secondary resources of minerals. Although a sizable portion of ferrous slags is recycled for use in building roads and other infrastructure, a sizable portion is still dumped. By November 2026, Member States must submit information on the quantity of critical raw materials (CRMs) in their secondary resources, as well as the quantification techniques employed, in accordance with Regulation (EU) 2024/1252. Therefore, the XRFS reliable measurements carried on ferrous slags were addressed to prevent dissipative loss of CRMs in cases where an improper slag recycling route is operated. The main novelty of this paper is the method of ensuring the reliability of the XRFS results based on weighted arithmetic mean and on the maximum likelihood approach. Secondly, the XRFS measurements carried on ferrous slags demonstrate that they contain CRMs like Ba, Sr, Y, etc.; however, below the minimum cut-off grade for CRMs, recovery XRFS cannot detect light CRMs. Our preliminary LIBS measurements on ferrous slags disclosed the presence of Li and Be. The drawbacks of the XRFS technique impose further research to develop an integrated XRFS, LIBS, and XRD procedure for comprehensive and trustworthy CRMs screening in extractive waste piles.

Solid waste treatment and resourceization critically depend on waste characterization. Heavy metals and critical raw materials are found as trace elements in solid waste dumps, and their reliable quantification plays a critical role for decision risk regarding effective waste management. The reliable quantification of trace elements is a very challenging issue. Hence, in this study, a new conservative approach for data analysis in screening for trace elements in waste dumps is presented. We propose a theoretical model for statistical data interpretation to overcome the drawbacks of conventional approaches based on unproven hypotheses, such as binomial, Poisson, or Gaussian distributions of the particles carrying the analyte. Our model addresses concentration values close to the limit of quantification (LOQ) of an analytical method. This model fills the gap of data analysis when a set of analytical results are uniformly distributed. Our approach deals with results reported as being lower than the LOQ. The model was applied on XRFS results from studies carried out on tailings to emphasize the differences among classic, robust, and conservative data analyses. Classical analyses overestimate the concentration values and underestimate the associated uncertainties increasing the decision risk. This study demonstrates that a conservative approach is mandatory when screening for trace elements if the concentration values are uniformly distributed. The proposed model can be applied to any solid waste dump, regardless of the analytical method used for trace element screening.

The use of sewage sludge for the bioremediation of hydrocarbon-contaminated soils remains insufficiently documented, particularly regarding microbial dynamics and material behavior during treatment. Although petroleum-hydrocarbon contamination severely disrupts soil functions, sewage sludge—through its high organic matter content, active bacterial communities, and fine mineral fraction—offers potential for the sustainable remediation of such soils. Three soil–sludge mixtures (P1:N1, P2:N1, P1:N2) were monitored to assess hydrocarbon degradation, bacterial community dynamics, and material behavior. Hydrocarbon-degrading and hydrocarbon-tolerant bacteria remained active, while sludge-derived Enterobacteriaceae declined below detection limits. Enrichment cultures of the sludge yielded three hydrocarbon-degrading strains (Providencia alcalifaciens IBBN1, Klebsiella pneumoniae IBBN2, Acinetobacter tandoii IBBN3), highlighting the metabolic potential of the active microbial communities. A moderate increase in surfactant concentrations reflected both residual anionic surfactants and biosurfactant production by these consortia, facilitating hydrocarbon mobilization. Total petroleum hydrocarbons (TPH) decreased by 45–60% (IR), and GC-FID analysis showed preferential degradation of C10–C40 fractions. Heavy-metal concentrations remained stable, indicating no geochemical changes or inhibitory effects on bacterial activity. Overall, the results confirm the potential of sewage sludge as a sustainable amendment that accelerates hydrocarbon biodegradation and supports integrated soil-restoration strategies.

The production of a ton of steel in an integrated steel plant generates of approximately 1 ton of ferrous slag. A great part of ferrous slags is recycled in civil and road construction etc., but a huge amount is still dumped. Recycling ferrous slag as cement precursor was considered the upcycling route. Regulation (EU) 2024/1252 requires the Member States to provide information, until November 2026, on the critical raw materials (CRM) amount in their secondary resources and on quantification methods used for. This study addresses two synergic objectives: ensuring the reliability of XRFS results and screening for CRM in ferrous slags based on XRFS outcomes. The main novelty of the paper is the way of ensuring the reliability of the XRFS results based on weighted arithmetic mean and on the maximum likelihood approach. Secondly, the XRFS measurements carried on ferrous slags demonstrate that they contain significant amounts of CRM like Ba, Sr, Y, etc. XRFS cannot detect light CRM. Our preliminary LIBS measurements on ferrous slags disclosed the presence of Li and Be. The drawbacks of the XRFS technique impose further research to develop an integrated XRFS, LIBS and XRD procedure for comprehensive and trustworthy CRM screening in extractive waste piles.

The Bi-Sn, Bi-Sn-Ag, and Bi-Sn-Sb solder alloy systems represent lead-free, environmentally friendly alternatives for reliable electronic assembly. These alloys comply with increasingly strict environmental and health regulations, while offering low melting points suitable for soldering temperature-sensitive components. The addition of Ag or Sb improves mechanical strength, hardness, wear resistance, and thermal stability. Microstructural analysis confirmed homogeneous, defect-free surfaces. Comprehensive microstructural characterization using optical microscopy, SEM, EDS, and BSE imaging revealed refined, heterogeneous microstructures with distinct phase segregation. Dendritic growth, eutectic formations, and intermetallic compounds were observed. Sb addition promoted granular intermetallics, while Ag induced needle-like precipitates along phase boundaries. EDS confirmed expected compositions, and BSE imaging enhanced contrast between Bi-, Sn-, Sb-, and Ag-rich regions. The study also reports the thermal and electrical conductivities of Bi60Sn40, Bi60Sn35Ag5, and Bi60Sn35Sb5 alloys over the 25–140 °C range. Bi60Sn40 showed an increase in thermal conductivity from 16.93 to 26.93 W/m·K, while Bi60Sn35Ag5 reached 18.28 W/m·K at 25 °C, and Bi60Sn35Sb5 exhibited 13.89 W/m·K. These findings underline the critical influence of alloying elements on microstructure, phase stability, and thermophysical behavior, supporting their application in low-temperature soldering technologies.