Sustain. Chem., Volume 6, Issue 4 (December 2025) – 4 articles

The substitution of hazardous, environmentally persistent solvents (NMP and DMAc) with more sustainable alternatives (ETAc and GBL) in fabricating flat sheet polyactic acid (PLA) membranes via nonsolvent-induced phase separation for air filtration applications was the focus of this study. The polymer-solvent affinity was first evaluated using Hansen solubility parameters, confirming suitable Relative Energy Difference (RED) values (<1) for all solvent candidates. Dope solutions prepared with biodegradable solvents demonstrated higher viscosity compared to those prepared with environmentally persistent solvents. These biodegradable solvent systems also exhibited slower precipitation rates during membrane formation. This resulted in spongelike cross-sectional morphologies, contrasting with the combined fingerlike and spongelike structures observed in membranes fabricated with environmentally persistent NMP and DMAc. Thermal analysis revealed that membranes fabricated with biodegradable solvents exhibited superior thermal stability with higher glass transition temperatures (Tg = 54.39–55.34 °C) compared to those made with environmentally persistent solvents (Tg = 49.97–50.71 °C). Membranes fabricated with ethyl acetate (ETAc) showed the highest hydrophobicity (contact angle = 115.1 ± 9°), airflow rate (12.7 ± 0.28 LPM at 0.4 bar) and maintained filtration efficiency at values greater than 95% for 0.3-μm aerosols. Full article

Rare earth elements (REEs) make up integral components in personal electronics, healthcare instrumentation, and modern energy technologies. REE leaching with organic acids is an environmentally friendly alternative to traditional extraction methods. Our previous study demonstrated that batch ultrasound-assisted organic acid leaching of REEs can significantly decrease environmental impacts compared to traditional bioleaching. The batch method is limited to small volumes and is unsuitable for industrial implementation. This study proposes a novel approach to increase reaction volume using a continuous ultrasound-assisted organic acid leaching method. Laboratory experiments showed that continuous ultrasound-assisted leaching increased the leaching rate (µg/h) 11.3–24.5 times compared to our previously reported batch method. Techno-economic analysis estimates the cost of the continuous approach using commercially purchased organic acids is $9465/kg of extracted REEs and $4325/kg of extracted REEs, using gluconic acid and citric acid, respectively. The sensitivity analysis reveals that substituting commercially purchased organic acids with microbially produced biolixiviant can reduce the process cost by approximately 99% while minimally increasing energy consumption. Environmental assessment shows that most of the emissions stemmed from the energy required to power the ultrasound reactor. We concluded that increased leaching capacity using a continuous ultrasound-assisted approach is feasible, but process modifications are needed to reduce the environmental impact. Full article

The confectionery industry produces effluents with diverse and complex compositions and high organic loads, which are typically not treated by conventional treatment plants. In this context, the Fenton process presents itself as an advanced chemical treatment alternative due to its ease of application, cost-effectiveness, and ability to improve the degradability of challenging effluents. This study addressed the question: How can Fenton’s reagent be applied as a pretreatment to reduce the organic load in real effluents from the food industry? The research evaluated this chemical pretreatment for effluents from a starch-based gummy candy production process, aiming to reduce the organic load and aid subsequent conventional treatments. Parameters such as COD, total dissolved solids (TDS), temperature, pH, electrical conductivity, dissolved oxygen, and degrees Brix (°Bx) were monitored before and after 2 and 4 h of pretreatment. The results showed that Fenton pretreatment reduced COD by more than 31%, with efficiency influenced by effluent composition and concentration. This removal can reduce discharge rates and operating costs, providing an economic advantage. The process proved to be a promising pretreatment option, contributing to the initial removal of pollutants and improving the performance of wastewater treatment systems, thus supporting sustainable industrial practices. Full article

Bimetallic mesoporous photocatalysts were synthesized via a wet impregnation method using SBA-15 as a support, and characterized by UV–visible diffuse reflectance spectroscopy, low-angle X-ray diffraction and N₂ physisorption. Among the tested materials, the Ti/Mn combination exhibited the highest photocatalytic activity in azo dye degradation. To understand this enhanced performance, catalysts with varying Mn loads and calcination ramps were evaluated. Additionally, experiments with radical scavengers (isopropanol, chloroform) and under N₂ insufflation were conducted to identify the active radical species. Catalysts prepared with low Mn content and higher calcination ramps showed the greatest activity, which significantly decreased with isopropanol, indicating hydroxyl radicals as the main reactive species. In contrast, samples with higher Mn content and quicker heating displayed reduced activity in the presence of chloroform, suggesting superoxide radical involvement. Spectroscopic analyses (XPS, UV–Vis DRS) revealed that increasing Mn load promotes the formation of Mn²⁺ over Mn⁴⁺ species and lowers the band gap energy. These findings highlight the direct correlation between synthesis parameters, surface composition and optical properties, providing a strategy for fine-tuning the performance of a photocatalyst. Full article