ZVI-Fenton, which is the combination of zero-valent iron (metallic Fe) and H₂O₂ is a relatively cheap advanced oxidation process for the elimination of contaminants from wastewater. Here we experimentally tested the ZVI-Fenton reaction at pH 4 towards two crucial goals in the treatment of secondary (partially treated) urban wastewater: (i) degradation of pharmaceuticals such as anti-inflammatory drugs (ibuprofen) and antibiotics (cefazolin, sulfamethoxazole), and (ii) elimination of a considerable fraction of bacteria through a combination of acidic pH and strongly oxidising conditions. In detail, ZVI-Fenton at pH 4 achieved degradation of both primary contaminants and potentially problematic transformation intermediates. The latter include toxic 4-isobutylacetophenone from ibuprofen and compounds potentially retaining antibiotic properties, namely cefazolin products with an intact β-lactam ring and sulfamethoxazole products retaining the p-amino sulfonic acid moiety. Furthermore, the ZVI-Fenton process significantly lowered the total abundance of bacteria, greatly aiding the final disinfection stage. Overall, both objectives were successfully achieved demonstrating that ZVI-Fenton at pH 4 is an efficient treatment against chemical and microbiological contaminants.

The definition of reliable equilibrium constants is an essential step in speciation studies, as the uncertainty and the consistency of the estimated values concur to define the reliability of the speciation model. It is therefore necessary to evaluate the uncertainty contribution of all factors involved at each step of the data acquisition procedure and to be aware about the consequences of systematic errors on the best-estimated values of experimentally measured equilibrium constants. In this work, a series of computer-generated H⁺-ion selective electrode titration curves simulating the alkalimetric titration of equimolar mixtures of Zn²⁺-EDTA in aqueous solutions have been processed by different equilibrium data fitting software. Hence, the uncertainties of the refined stability constants of the Zn²⁺-EDTA complexes could be derived, while excluding the experimental variability that intrinsically affects all practical experiments. The sensitivity of a given chemical system to different data processing strategies and to possible errors in the input data was evaluated. The systematic errors considered relate to the potential reading, the concentration of the titrant and solution components, and ionic strength variations during titrations. The outcomes highlight how unsuitable decisions taken at the stage of nonlinear least squares fitting of the data can affect the results and underline that the main error contribution is related to the measurement of the glass-electrode potential. The processing of simulated data sets can be a useful tool to alert the researchers to the sensitivity of a given chemical system to different strategies and to possible errors in the input data.

Biosurfactants account for about 12% of the global value of the surfactant market, which is currently dominated by synthetic surfactants obtained from fossil sources. Yet, the production of biosurfactants from renewable feedstock is bound to increase, driven by the increasing pressure from both society and governments for chemistry-based industries to become more ecofriendly and economically sustainable. A photo-chemical oxidation process is reported here, yielding new biosurfactants from urban biowaste in water that perform as a solvent and terminal oxidant reagent at room temperature without the addition of conventional oxidants and catalysts. Products with 200–500 kDa molecular weight are obtained. They lower the surface tension of water down to 34 mN/m at 0.5–2 g/L concentration. The estimated cost is rather low (0.1–1.5 EUR/kg), which is competitive with the cost of synthetic surfactants but much lower than the cost of the best-performing bacterial surfactants. For the implementation of the photo-chemical oxidation process at the industrial level, the results suggest that the new biosurfactants obtained in the present work may not reach the performance level of the best-performing bacterial surfactants capable of lowering the surface tension of water down to 28 mN/m. Yet, the biosurfactants produced by the photo-chemical process have a greater chance of being marketed on large scales.

The chemical composition of the soluble fraction of atmospheric particulate matter (PM) and how these components can combine with each other to form different species affect the chemistry of the aqueous phase dispersed in the atmosphere: raindrops, clouds, fog, and ice particles. The study was focused on the analysis of the soluble fraction of Arctic PM₁₀ samples collected at Ny-Ålesund (Svalbard Islands, Norwegian Arctic) during the year 2012. The concentration values of Na⁺, K⁺, NH₄⁺, Ca²⁺, Mg²⁺, Mn²⁺, Cu²⁺, Zn²⁺, Fe³⁺, Al³⁺, Cl⁻, NO₂⁻, NO₃⁻, SO₄²⁻, PO₄³⁻, formate, acetate, malonate, and oxalate in the water-soluble fraction of PM₁₀ were determined by atomic spectroscopy and ion chromatography. Speciation models were applied to define the major species that would occur in aqueous solution as a function of pH (2–10). The model highlights that (i) the main cations such as Na⁺, K⁺, Mg²⁺, and Ca²⁺ occur in the form of aquoions in the whole investigated pH range; (ii) Cu²⁺, Zn²⁺, and, in particular, Fe³⁺ and Al³⁺ are mostly present in their hydrolytic forms; and (iii) Al³⁺, Fe³⁺, and Cu²⁺ form solid hydrolytic species that precipitate at pH values slightly higher than neutrality. These latter metals show interesting interactions with oxalate and sulfate ions, too. The speciation models were also calculated considering the seasonal variability of the concentration of the components and at higher concentration levels than those found in water PM extracts, to better simulate concentrations actually found in the atmospheric aqueous phase. The results highlight the role of oxalate as the main organic ligand in solution. Graphical Abstract

The toxicity of atmospheric particulate matter (PM) depends not only on its burden in air, but also on its chemical composition, which affects its ability to induce oxidative stress at the cellular level through reactive oxygen species (ROS) formation. The oxidative potential (OP) of PM has been proposed as an integrative metric for PM toxicity; however, standardized analytical protocols are still lacking. In this study, the performance of the ascorbic acid (AA) assay was evaluated for the determination of PM oxidative potential. A total of 32 filters were analysed, corresponding to 16 filters per site (urban traffic and rural background) and eight filters per year (2020 and 2021). For each selected month (January, May, August, and November), the daily filters corresponding to the minimum and maximum PM₁₀ mass concentrations within that month were chosen. Ascorbic acid depletion was monitored spectrophotometrically at 265 nm under physiological conditions (phosphate buffer, PB, 37 °C). The method was tested using aqueous solutions containing individual metals considered to play a major role in the oxidative behaviours of PM (Cu, Cr, Fe, Mn, Ni and Zn) and four standard reference materials (SRMs). This acellular test was then applied to atmospheric PM₁₀ collected in 2020–2021 at the two monitoring sites in the Turin metropolitan area (Italy). Among the individual metals, Cu showed the highest oxidative activity, consistent with the literature data; BCR 176 showed the highest oxidative activity. Urban PM₁₀ samples exhibited higher oxidative potential (0.12–0.60 nmol AA min⁻¹ m⁻³) than suburban samples (0.10–0.38 nmol AA min⁻¹ m⁻³). Metal concentrations in the PM₁₀ samples were determined by ICP-OES and ICP-MS in both acid-digested samples and PB extracts used for OP determination, allowing for comparison between the total and bioaccessible metal fractions. To the best of our knowledge, this is the first study to investigate the relationship between PM₁₀ oxidative potential and its total and bioaccessible elemental composition in the Turin metropolitan area. Site characterization was expanded by quantifying PM₁₀ carbon fractions (EC/OC and brown carbon) through multiwavelength thermal/optical carbon analysis following the EUSAAR_2 protocol. Because of the sampling strategy adopted and the limited number of processed samples, the seasonal and between-site comparisons reported in this study refer specifically to the analysed samples. The combined evaluation of OP and ICP-based elemental composition provides insights into the role of transition metals in PM-induced oxidative stress and supports the integration of OP measurements into air quality assessment frameworks.