Sustain. Chem., Volume 5, Issue 3 (September 2024) – 4 articles

For a long time, the leather industry has considered the chromium tanning process to be the easiest and fastest way to treat raw hides and transform them into valuable products. In the last few decades, increasing attention has been paid to the potential oxidation of the trivalent chromium in tanned leather. This happens for many reasons, such as the quality of the tanning agent or the adoption of good manufacturing practices. Anyway, the main problem, which is difficult to solve, is the sensibility of the free residual chromium tanned leather, which is high enough for possible harmful activity. Given this scenario, this work proposes a solution to decrease hexavalent chromium formation by using antioxidants during the leather tanning process. In this regard, a screening work was started, to find the worst-case scenario for trivalent chromium oxidation. To do this, commercial tanning products were employed, especially fatliquoring agents, which, in some cases, are the main source that could easily react with ROS (Reactive Oxygen Species) to drive chromium oxidation. After the determination of conditions, different groups of common antioxidants were tested to analyse the antioxidation performances and their possible use in the chromium-based tanning process. The results underline the efficient action of the antioxidants studied, paving the way for some interesting perspectives to limit the drawbacks of chromium tanned leather. Full article

Cross-linked polymers synthesized through inverse vulcanization of unsaturated vegetable oils (biopolymers) were used as matrices for incorporating gentamicin (GEN) to form a biocomposite that can amplify GEN antimicrobial activity against Pseudomonas aeruginosa. Two different biopolymers were synthesized using soybean (PSB) and sunflower (PSF) oils by inverse vulcanization cross-linked with sulfur in a 1:1 weight ratio. The study involves the synthesis and characterization of these biopolymers using FTIR and SEM as well as measurements of density and hydrophobicity. The results reveal the formation of biopolymers, wherein triglyceride molecules undergo cross-linking with sulfur chains through a reaction with the unsaturated groups present in the oil. Additionally, both polymers exhibit a porous structure and display hydrophobic behavior (contact angle higher than 120°). The biopolymers swell more in GEN solution (PSB 127.7% and PSF 174.4%) than in pure water (PSB 88.7% and PSF 109.1%), likely due to hydrophobic interactions. The kinetics of GEN sorption and release within the biopolymer matrices were investigated. The antibacterial efficacy of the resulting biocomposite was observed through the analysis of inhibition growth halos and the assessment of P. aeruginosa viability. A notable enhancement of the growth inhibition halo of GEN (13.1 ± 1.1 mm) compared to encapsulated GEN (PSF-GEN 21.1 ± 1.3 and PSB-GEN 21.45 ± 1.0 mm) is observed. Also, significant bactericidal activity is observed in PSF-GEN and PSB-GEN as a reduction in the number of colonies (CFU/mL), more than 2 log₁₀ compared to control, PSF, and PSB, highlighting the potential of these biopolymers as effective carriers for gentamicin in combating bacterial infections. Full article

The plant-mediated synthesis of therapeutic metal nanoparticles is an intensively exploited field in the last decade. In particular, Salvia officinalis, considered one of these plants, was used in this work to synthesize silver particles. Here, we have used harmless substances to obtain silver particles and common characterization methods for quickly estimating sizes and shapes. Thus, UV–Visible spectroscopy helped us online-monitor and optimize the synthesis of silver particles and estimate the size of metallic particles in the stock solutions. The resulting eco-friendly synthesized silver particles were then separated and re-dispersed in water, to be analyzed by laser light scattering, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to prove their nanometric size and shape polydispersity. Furthermore, the role of citric acid in stabilizing colloidal solutions of silver nanoparticles was studied. Full article

The aim of this research was to separate the over-the-counter nonsteroidal anti-inflammatory drug (NSAID), ibuprofen, from an aqueous solution using the adsorption method, as this NSAID is one of the most globally consumed. An adsorbent was crafted from the Agave angustifolia bagasse, a byproduct of the bacanora industry (a representative alcoholic beverage of the state of Sonora, in northwestern Mexico). Three bioadsorbents (BCT1, BCT2, and BCT3) were produced via pyrolysis at a temperature of 550 °C, with slight variations in each process for every bioadsorbent. The bioadsorbents achieved material yields of 25.65%, 31.20%, and 38.28% on dry basis respectively. Characterization of the bagasse and adsorbents involved scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The biomass morphology exhibited a cracked surface with holes induced via the bacanora production process, while the surface of the bioadsorbents before ibuprofen adsorption was highly porous, with a substantial surface area. After adsorption, the surface of the bioadsorbents was transformed into a smoother grayish layer. The macromolecules of cellulose, hemicellulose, and lignin were present in the biomass. According to functional groups, cellulose and hemicellulose degraded to form the resulting bioadsorbents, although traces of lignin persisted after the pyrolysis process was applied to the biomass. In an adsorption study, BCT1 and BCT2 bioadsorbents successfully removed 100% of ibuprofen from aqueous solutions with an initial concentration of 62.6 mg/L. In conclusion, the biocarbon derived from Agave angustifolia bagasse exhibited significant potential for removing ibuprofen via adsorption from aqueous solutions. Full article