Evaluation of initial pH and urea hydrogen peroxide (UHP) co-pretreatment on waste-activated sludge.

Wastewater treatment and conversion into renewable energy sources have been of great interest in recent times due to growing environmental pollution concerns and need for sustainable energy sources. Sewage sludge treatment can convert sludge into renewable energy. In this study, the impact of initial pH and urea hydrogen peroxide (UHP) co-pretreatment on sludge hydrolysis and anaerobic digestion was investigated. The pH of sludge was initially adjusted to 7, 9, and 11 before the addition of 8 mmol/g VS UHP. Under 24 h pretreatment, alkaline medium and UHP effectively enhanced sludge solubilization and hydrolysis. The combination of chemical, sonication, and centrifugation improved the extraction of extracellular polymerase substances released in soluble state. Secondly, anaerobic digestion was performed for 11 days to determine the influence of a lower mesophilic temperature (20 °C) and retention time on the pretreated sludge. The highest NH4+-N concentration of 5.32 g/L was recorded in pH 7+UHP. The most significant total VFA concentration of 13.1 g COD/L was observed in pH 7+UHP on day 9. Acetic acid, isovaleric acid and propionic acid accounted for 80%-83% of the total VFA composition in all pretreated reactors. Lower mesophilic temperature efficiently optimized UHP and VFA production in the pretreated reactors. Microbial metabolism was stabilized under a longer retention time. Alkaline pH and longer retention time elevated NH4+-N and VFA concentration. The results showed that initial pH and UHP co-pretreatment of waste activated sludge offer an alternative pathway for enhancing sludge hydrolysis and VFA production applicable in sludge treatment.

Water-Triggered Transformation of Ligand-Free Lead Halide Perovskite Nanocrystal-Embedded Pb(OH)Br with Ultrahigh Stability.

Lead halide perovskite (LHP) nanomaterials have attracted tremendous attention owing to their remarkable optoelectronic properties. However, they are extremely unstable under moist environments, high temperatures, and light illumination due to their intrinsic structural lability, which has been the critical unsolved problem for practical applications. To address this issue, we propose a facile and environmentally friendly ligand-free approach to design and synthesize rod-like CsPb2Br5-embedded Pb(OH)Br with excellent stability under various harsh environments such as soaking in water, heating, and ultraviolet (UV) illumination. Plate-like CsPbBr3- and Cs4PbBr6-embedded Pb(OH)Br powders are first formed by evaporating the solvent in a dispersion of ethanol (or methanol, isopropanol), Cs2CO3, and PbBr2. Upon soaking in water, the plate-like sample undergoes phase transformation from CsPbBr3 and Cs4PbBr6 to CsPb2Br5 and shape conversion from nanoplate to a microrod, leading to the formation of rod-like CsPb2Br5-embedded Pb(OH)Br. The stable Pb(OH)Br coating effectively prevents the luminescent CsPb2Br5 nanocrystals from reacting with water, leading to extremely high aqueous stability of the CsPb2Br5-embedded Pb(OH)Br. The photoluminescence (PL) intensity of the representative CsPb2Br5-embedded Pb(OH)Br sample can maintain 92.2% of the initial PL intensity value even after soaking in room-temperature water for 165 days; in the meantime, the phase and shape are preserved. The typical sample also shows outstanding stability under hot water, UV illumination, and annealing conditions. The ultrahigh aqueous stability, thermal stability, and photostability of the CsPb2Br5-embedded Pb(OH)Br nanomaterials suggest an effective, facile, and environmentally friendly technique to grow perovskite-based nanomaterials for promising practical applications in the optoelectronic field.

Ambient temperature sulfonated carbon fiber reinforced PEEK with hydroxyapatite and reduced graphene oxide hydroxyapatite composite coating.

30% carbon fiber reinforced polyetheretherketone (CFR-PEEK) has in recent times, become significant in the orthopedic industry because its elastic modulus can be engineered to match that of the human bone. But it is bioinert and does not integrate well with the immediate bone tissue environment. In this study, a combined surface modification technique involving ambient temperature sulfonation and surface coating of (hydroxyapatite (HA), 5%reduced graphene oxide hydroxyapatite(5%RGO/HA) and 10%reduced graphene oxide hydroxyapatite(10%RGO/HA) composites) on 30%CFR-PEEK was achieved with an appropriate temperature treatment at 345°C in nitrogen. The coatings adhered unto the surface of S30%CFR-PEEK with an improved hydrophilicity and bioactivity. With the sample S30%CFR-PEEK+HA, having the highest enhanced hydrophilicity from 112.5 ± 2.5° to 20 ± 2° and bioactivity. An improvement in hydrophilicity and bioactivity depicts a change in surface chemistry which will have a positive impact in the interaction of the materials surface with immediate bone environment for a successful application in the orthopedic industry.

Hexamethyldisilazane-triggered room temperature synthesis of hydrophobic perovskite nanocrystals with enhanced stability for light-emitting diodes.

A novel facile room-temperature, hexamethyldisilazane (HMDS)-mediated strategy is demonstrated for the synthesis of all-inorganic perovskite colloidal nanocrystals (NCs). As a unique reaction-triggering and morphology-directing agent, HMDS is introduced for the first time to trigger the room-temperature reaction for generating perovskite NCs with controlled morphology and optical properties. Particularly, the stability of the resulting NCs is greatly enhanced due to the surface modification by hydrophobic -CH3 groups from HMDS. The typical CsPbBr3 perovskite NCs films are highly stable without significant decrease in photoluminesence (PL) intensity after being exposed to 60% relative humidity for 720 h. Moreover, no noticeable change of phase and morphology occurs even after 100 days of exposure. The representative CsPbBr3 NCs are employed in a prototype white-light-emitting diodes (WLEDs) on 365 nm commercial GaN chip. The present strategy provides a facile and versatile route not only to control the morphology and optical properties of perovskites nanomaterials at room temperature but also enhance their stability, which will bring promising potential application for optoelectronics.