Imidacloprid is still a widely used neonicotinoid insecticide that is banned in many countries because of the associated environmental risks. Due to the inefficiency of conventional wastewater treatments for pesticide removal, new treatment methods are being investigated. Electrochemical methods, including electrocoagulation (EC), seem to be promising alternatives considering their effectiveness in removing various pollutants from wastewater. The aim of this study was to investigate the effects of electrode material, current density, ultrasound, and operation time on the efficiency of imidacloprid removal from a model solution by EC. The combination of aluminum electrodes and 20 A of applied current for 20 min resulted in total imidacloprid degradation. A simplified energy balance was introduced as a form of process evaluation. Combining ultrasound with EC resulted in 7% to 12% greater efficacy than using only EC.

The growing amounts of sewage sludge (SS) and water pollution caused by heavy metals are major environmental concerns. This study addresses both issues by investigating the potential of biochar derived from SS gasification at an experimental plant as an effective adsorbent for the removal of selected heavy metals, cadmium, chromium, copper, and lead, from synthetic wastewater. A Box–Behnken design was used to determine the influence of the biochar mass, initial heavy metal concentration, pH, and time on the heavy metal removal. For the statistical analysis, 104 experiments were performed. The pristine SS biochar demonstrated an adsorption capacity reaching up to 46.64 mg/g for Cd, 43.89 mg/g for Cr, 42.42 mg/g for Cu, and 72.66 mg/g for Pb from single-component synthetic solutions in acidic-to-neutral conditions, with an over 99% removal efficiency for all four heavy metals under optimal conditions. The removal of all the tested metals followed pseudo-second-order kinetics, with Cd fitting the Langmuir model and Pb, Cr, and Cu fitting the Freundlich model. This paper also provides suggestions for further research focused on the multiple uses of biochar as an adsorbent and later as a substitute material in the construction industry, aiming to achieve an integrated approach and maximizing the overall sustainability of wastewater treatment and waste management by utilizing waste as a resource.

Due to its high solubility in water, a large amount of the neonicotinoid insecticide acetamiprid persisting in the soil of treated crops enters surface water or groundwater. The aim of this study was to investigate the photocatalytic degradation of acetamiprid in an aqueous medium. The experiments were carried out in an annular suspension reactor operating in recirculated batch mode and using a UV-A lamp as the radiation source. An appropriate modification of the commercial TiO₂-P25 photocatalyst was carried out to reduce its band gap energy and electron–hole recombination as well as to extend the visible light range of TiO₂. The photodegradation study was carried out using a three-factor two-stage Box–Behnken experimental design to investigate the main effects and interactions between the operating variables, such as solution pH, initial concentration of acetamiprid, and amount of photocatalyst. The efficiency of the processes was determined by high performance liquid chromatography. The first-order pseudo-reaction kinetic model, as a simplification of the models of Langmuir–Hinshelwood under conditions of relatively low acetamiprid concentration, was applied and the reaction rate constants were estimated. The results of the study showed that the initial concentration of the pollutant was the most influential factor for the photocatalytic degradation process. Using ANOVA analysis, a linear model was established to predict the system behaviour at different operating conditions. The highest conversion and rate constant of acetamiprid degradation were recorded in the experiment with the lowest tested concentration of acetamiprid (2 mg/L), the average concentration of photocatalyst (60 mg) and at pH 8. GRAPHICAL ABSTRACT

This study investigated the removal of selenium (Se) and strontium (Sr) from water using a three-stage electrochemical reactor with integrated pH control. A total of 102 experiments were performed following a Box–Behnken design that varied the electrode material, applied current, number of electrodes, operating time, and initial pH to evaluate their effects on the Se and Sr removal efficiencies. The complete removal of Se was achieved under multiple conditions, even without pH control, while effective Sr removal required a high current and initial pH adjustment. The top performance for both elements was achieved with a 25 A current, four Fe electrodes, 15 min of operational time per phase (cycle), and a middle range of pH values, which resulted in 97.92% and 99.96% removals of Sr and Se, respectively. This research highlighted the novel approach of using electrochemical pH control to achieve high removal efficiencies of Se and Sr from water in a short operating time, which surpassed the efficiencies reported in previous studies.

Cilj ovog rada bio je istražiti strujanje kapljevine u trima različitim modelnim cijevima: ravnoj praznoj cijevi, cijevi ispunjenoj staklenim kuglicama i praznoj spiralnoj cijevi. Pri tome je osnovni koncept sadržan u pojmu raspodjele vremena zadržavanja kapljevine (RVZ). Kako bi se dobile RVZ krivulje, eksperimentalno je mjerena koncentracija inertne tvari (engl. tracer) na izlasku iz cijevi tijekom vremena. Kao inertna tvar upotrijebljena je otopina vodljive soli KCl. Pomoću modela aksijalne disperzije izračunate su vrijednosti srednjeg vremena zadržavanja i disperzijskog broja za različite protoke (100 – 600 ml min–1) i volumene inertne tvari (0,3 i 1 ml) te je dan kvantitativan opis odstupanja od idealnog strujanja.

Sulfate is a soluble and chemically stable anion that cannot be destroyed, only separated, concentrated or transformed, and its removal from mine water and industrial effluents is increasingly driven by site-specific discharge limits, commonly of 250–1000 mg L⁻¹. This systematic review critically evaluates chemical precipitation, membrane, sorptive, biological and electrochemical technologies in terms of removal mechanism, achievable residual sulfate and unit treatment cost. Web of Science Core Collection and Scopus were searched on 20 June 2026 (publications 1999 to May 2026) and supplemented by citation searching, publisher platforms and regulatory sources. Eligible sources reported sulfate as an explicit target species with a removal mechanism, performance, operating or cost figure, whereas sources in which sulfate was only a background electrolyte, or which studied sulfide or sulfite without a sulfate figure, were excluded. Evidence was appraised by scale, water matrix and cost basis, without a formal risk of bias tool, and synthesized narratively. Search reproducibility, identification routes, screening and a random 20% sample of the data extraction were cross-checked by a second reviewer. A broadened sensitivity search indicated that relevant studies on matrices other than mine water and wastewater were under-retrieved. Reported and stoichiometrically derived costs were normalized per cubic metre and per kilogram of sulfate removed. Ninety-three sources were included (59 from the database searches and 34 from other sources), mostly journal articles, with evidence ranging from laboratory to full scale. Under representative mine water conditions, gypsum solubility limits inexpensive lime and limestone treatment to residuals of approximately 1200–1800 mg L⁻¹. Unit costs span nearly three orders of magnitude, from about 0.02 USD m⁻³ for constructed wetlands to about 18 USD m⁻³ for single-pass barium chloride precipitation and the heterogeneous evidence indicates an apparent tradeoff between cost and achievable residual. No technology combines low cost with low residual. Crossing the gypsum ceiling raises cost roughly three- to tenfold for mainstream polishing routes. In four common reference scenarios, treating concentrated water to 250 mg L⁻¹ costs about two to five times as much as partial treatment to about 1500 mg L⁻¹ for mainstream treatment trains at the range midpoints, with widely overlapping ranges. The evidence is limited by heterogeneous matrices, scarce standardized cost reporting and, for several technologies, laboratory-scale data. Hybrid trains pairing low-cost bulk removal with selective polishing and resource recovery emerge as the most defensible strategy. This review was not registered. Funding: European Union—NextGenerationEU.