On‐site wastewater treatment using reactive filter media

The aim of this study is to reduce the phosphate concentration in treated wastewater using a small amount of the reactive filter media, Filtralite P. Biologically treated wastewater was passed through a filter with 215 g of Filtralite P. In the laboratory, the phosphate removal efficiency was 51% at a flow speed of 0.87 m/h. Under real conditions, in an experimental stand filled with 0.5 m³ of Filtralite P, the phosphate removal efficiency was 85% and the removal efficiency of total suspended solids was 57% after a 5‐month period. The residual phosphate concentration in the filtrate from the experimental stand was 1 mg/L of PO₄‐P after the 5‐month period. The experimental filtration plant was buried in the ground, and it did not freeze and worked well under winter conditions. The results of this study can be useful in the design and development of tertiary wastewater treatment plants in view of their sustainability potential.     

Impact of precursor preparation on density of gadolinium iron garnets synthesized via reactive sintering

Gadolinium iron garnet was obtained from two different precursors, homogenized in isopropyl alcohol and in an aqueous environment with a fixed pH. In the first case, it was a mixture of goethite (FeO(OH)) and gadolinium oxide (Gd₂O₃); in the second, a mixture of GdIP (GdFeO₃) and α-Fe₂O₃. Conditions of homogenization in the aqueous environment were selected based on the zeta (ξ) potential measurements as the function of pH. DSC measurements of the output powder mixtures allowed the identification of the effects observed during the temperature rise. In the case of the material obtained from a mixture of goethite (FeO(OH)) and gadolinium oxide, with the increasing temperature, we observe three effects, the first of which corresponds to the phase transformation of goethite into α-Fe₂O₃, the second corresponds to the reaction of gadolinium iron perovskite (GdIP) formation, and the third to the reaction in which a gadolinium iron garnet (GdIG) is formed. However, in the case of heat treatment of the mixture of GdIP and α-Fe₂O₃, we only observe the effect responsible for a solid state reaction leading to the formation of gadolinium iron garnet. Dilatometric measurements allowed to determine the changes in linear dimensions at various stages of reaction sintering. The resulting materials were sintered at temperatures of 1200, 1300, and 1400 °C. In the case of the material obtained from a mixture of perovskite and iron (III) oxide, already at the temperature of 1300 °C, a density has been obtained at around 95% of the theoretical density, and the temperature of 1400 °C allowed achieving a density of 97% of the theoretical density. Whereas, for the material obtained from a mixture of goethite (FeO(OH)) and gadolinium oxide, a density above 95% of theoretical density was achieved only at 1400 °C.     

Properties of gas detonation ceramic coatings and their effect on the osseointegration of titanium implants for bone defect replacement

An optimal performance of bone implants with bioceramic coatings is closely related to the surface modification technology. For the first time, we have evaluated a gas detonation deposition (GDD) approach to obtain biocompatible ceramic coatings based on bioglass (BG) and calcium phosphates on Ti-based alloys as prospective materials towards their application for the development of bone implants. For the production of the coatings, hydroxyapatite (HA), HA metal-substituted (containing Ag⁺, Cu²⁺, or Zn²⁺) and tricalcium phosphate (TCP) were synthesized and characterized. Pure powders and their combination with BG were used to obtain coatings on a Ti–6Al–4V alloy using the developed automatized GDD setup. The microstructure, phase and chemical composition of the produced coatings were studied using XRD, SEM-EDS and Raman spectroscopy. The produced coated materials were evaluated in vivo in Wistar rats to analyze a reparative osteogenesis over a period of 12 weeks. The results regarding the optimization of the GDD method indicate its high productivity, as confirmed by high deposition rates. The highest deposition rate was observed for the coatings obtained from the HA metal-substituted powders. The results revealed a partial transformation of a HA phase to an α-TCP phase during the deposition, with a prevalence of the HA-phase in the coatings. According to the histological evaluation, the reparative osteogenesis occurs through the perimeter of the titanium implants, whereas the regeneration level increases from the 4th to the 12th week. The highest osteointegration level was detected for the implants coated with a biocomposite consisting of BG, HA and TCP. The results of the current study demonstrate an effectiveness of the GDD method to produce biocompatible coatings on Ti-based alloys. This provides excellent prerequisites towards the application and standardization of the GDD technology to manufacture bone implants for bone fixation and defect replacement, as well as the development of dental implants.     

Tailored-Made Polydopamine Nanoparticles to Induce Ferroptosis in Breast Cancer Cells in Combination with Chemotherapy

Ferroptosis is gaining followers as mechanism of selective killing cancer cells in a non-apoptotic manner, and novel nanosystems capable of inducing this iron-dependent death are being increasingly developed. Among them, polydopamine nanoparticles (PDA NPs) are arousing interest, since they have great capability of chelating iron. In this work, PDA NPs were loaded with Fe³⁺ at different pH values to assess the importance that the pH may have in determining their therapeutic activity and selectivity. In addition, doxorubicin was also loaded to the nanoparticles to achieve a synergist effect. The in vitro assays that were performed with the BT474 and HS5 cell lines showed that, when Fe³⁺ was adsorbed in PDA NPs at pH values close to which Fe(OH)₃ begins to be formed, these nanoparticles had greater antitumor activity and selectivity despite having chelated a smaller amount of Fe³⁺. Otherwise, it was demonstrated that Fe³⁺ could be released in the late endo/lysosomes thanks to their acidic pH and their Ca²⁺ content, and that when Fe³⁺ was co-transported with doxorubicin, the therapeutic activity of PDA NPs was enhanced. Thus, reported PDA NPs loaded with both Fe³⁺ and doxorubicin may constitute a good approach to target breast tumors.     

Influence of aluminum phosphate on the tribocorrosion performance of chemically bonded phosphate ceramic coatings

In this study, chemically bonded phosphate ceramic coatings (CBPCCs) with different contents of aluminum phosphate (AP) are prepared on stainless steel (AISI 304L). Differential scanning calorimetry, X-ray diffraction, contact angle test, and a tribocorrosion experiment are carried out to clarify the role of AP in the tribocorrosion performance of CBPCCs. The results show that, with the increase in the AP content, the enthalpy of curing increases because of the greater formation of the bonding phase AlPO₄. Both in static corrosion and in tribocorrosion, the corrosion current density of CBPCCs achieves the lowest value when the weight ratio of AP to polytetrafluoroethylene is about 0.78. Additionally, the influence mechanism of AP on tribocorrosion is clarified. AlPO₄ from the reaction between AP and Al₂O₃ has excellent mechanical properties and can enhance the wear resistance of CBPCCs by reducing the mechanical wear and the increased wear due to corrosion. The alumina particles wrapped by AlPO₄ can form a dense and smooth surface and change the direction of electrolyte propagation, which leads to the increase in the tribocorrosion resistance of CBPCCs.     

A theoretical and experimental study of phosphate ester inhibitors for AISI 1018 in carbon dioxide-saturated 3.5 wt% NaCl solution

Phosphate ester was investigated as a corrosion inhibitor for AISI 1018 carbon steel in carbon dioxide-saturated chloride solutions at different temperatures and pressures. The corrosion tests were realized by electrochemical techniques, weight loss measurements, bubble tests, and a high-pressure/high-temperature autoclave system. The corrosion tests demonstrated that the investigated molecule is an excellent corrosion inhibitor. The inhibiting effect is even bigger at high pressure and temperature than at atmospheric pressure and room temperature. The thermodynamic parameters were calculated and determined to obey the Langmuir isotherm. Polarization studies revealed that the evaluated inhibitor is a mixed type.     

Enhancement effect of zero-valent iron nanoparticle and iron oxide nanoparticles on dark fermentative hydrogen production from molasses-based distillery wastewater

This study investigates the effect of two different iron compounds (zero-valent iron nanoparticle: nZVI and iron oxide nanoparticles: nIO) and pH on fermentative biohydrogen production from molasses-based distillery wastewater. The nZVI and nIO of optimum particle sizes of 50 nm and 55 nm respectively were synthesized and applied for fermentative hydrogen (H₂) production. The addition of nIO & nZVI at (0.7 g/L, pH: 6) resulted in the highest H₂ yield, H₂ production rate, H₂ content and COD reduction. Moreover, the kinetic parameters of H₂ production potential (P) and H₂ production rate (R_m) increased to 387 mL, and 22.2 mL/h, respectively for nZVI, these values were 363 mL and 21.8 mL/h for nIO. The results obtained indicated the positive effect of nZVI and nIO addition on enhanced fermentative H₂ production. The addition of nZVI & nIO resulted in 71% and 69.4% enhancement in biohydrogen production respectively.     

A comparison of two hydrogen storages in a fossil-free direct reduced iron process

Hydrogen direct reduction has been proposed as a means to decarbonize primary steelmaking. Preferably, the hydrogen necessary for this process is produced via water electrolysis. A downside to electrolysis is the large electricity demand. The electricity cost of water electrolysis may be reduced by using a hydrogen storage to exploit variations in electricity price, i.e., producing more hydrogen when the electricity price is low and vice versa. In this paper we compare two kinds of hydrogen storages in the context of a hydrogen direct reduction process via simulations based on historic Swedish electricity prices: the storage of gaseous hydrogen in an underground lined rock cavern and the storage of hydrogen chemically bound in methanol. We find the methanol-based storages to be economically advantageous to lined rock caverns in several scenarios. The main advantages of methanol-based storage are the low investment cost of storage capacity and the possibility to decouple storage capacity from rate capacity. Nevertheless, no storage option is found to be profitable for historic Swedish electricity prices. For the storages to be profitable, electricity prices must be volatile with relatively frequent high peaks, which has happened rarely in Sweden in recent years. However, such scenarios may become more common with the expected increase of intermittent renewable power in the Swedish electricity system.     

The role of Al2O3, MgO and CeO2 addition on steam iron process stability to produce pure and renewable hydrogen

Steam iron process represents a technology for H₂ production based on iron redox cycles. Fe_xO_y are reduced by syngas/carbon to iron, which is subsequently oxidized by steam to produce pure H₂. However, the system shows low stability.In this work, the effect of promoters (Al₂O₃, MgO and CeO₂) on Fe_xO_y stability is investigated (10 consecutive redox cycles). Bioethanol is used as a reducing agent. The particles are synthesized by coprecipitation method, analysed by BET, XRD, SEM and tested in a fixed bed reactor (675 °C, 1 bar). Pure H₂ is obtained controlling the Fe_xO_y reduction degree feeding different amounts of ethanol (4.56–1.14 mmol) until no CO is detected in oxidation. The results show that the promoters not only improve the thermal stability of Fe_xO_y but also affect its redox activity and react with iron forming spinel structures. MgO led to the highest activity and cyclability (H₂ = 0.15 NL; E = 35%).