In the industrial production of aluminum through the Bayer process, two main pollutants are generated, red mud and carbon dioxide (CO₂). Conventional processes for treating polluting waste include the neutralization of red mud with hydrochloric acid (HCl) and the capture of CO₂ with ethanolamine (CH₂(NH₂)CH₂OH). However, the CO₂ generated can be used to neutralize the red mud, allowing the simultaneous treatment of two harmful substances and reducing the amount of HCl required to neutralize the red mud. The solvent present in red mud is the residual alkaline liquor from the Bayer process, which absorbs CO₂ in a secondary stage, but is not yet considered as a pollutant treatment process. From this perspective, the treatment of two polluting substances (red mud and CO₂) can be carried out in aluminum production plants with lower energy consumption. In the present study, bench and pilot-scale tests were carried out to verify the efficiency of CO₂ adsorption by red mud at a temperature of 25 °C. Among the results of bench tests, 84.05% CO₂ absorption by red mud was obtained. And on a pilot scale, using a bubble column and continuous flow, an efficiency of 96.80% CO₂ absorption was observed with red mud. The study also found that among the most significant variables in this type of treatment are the solid content and mechanical speed.

This study investigated the chemical recycling of poly(ethylene terephthalate) (PET) fiber residues from two sources—high-molar mass mooring ropes and low-molar mass textile-grade fibers—to produce functional oligomers. Glycolysis was carried out using polyethylene glycol (PEG400) as the depolymerizing agent, and two catalysts were assessed, zinc acetate and lithium octoate, with the latter reported on for the first time in this application. Reactions were performed for 180 min under mechanical stirring, inert atmosphere, reflux, and controlled heating. The resulting oligomers were characterized by Fourier-transform infrared spectroscopy (FTIR), hydroxyl and acidity indices, and thermogravimetric analysis (TGA). Both PET feedstocks showed high reactivity toward glycolysis. Monitoring the reactions by acidity index indicated that conversion reached equilibrium at approximately 120 min. ATR-FTIR confirmed the formation of ester and hydroxyl groups, consistent with oligomer structures. Glycolysis of PET derived from mooring ropes produced oligoesters with hydroxyl values of 228 and 242 mgKOH/g for zinc acetate and lithium octoate, respectively, and molar masses of 1296 and 1338 g/mol for zinc acetate and lithium octoate, respectively. These values are suitable for subsequent syntheses such as polyester polyol production.

This study produces and characterizes immiscible blend systems made with high-density polyethylene (HDPE) and post-industrial polyamide 11 (PA11) obtained from offshore. Blends were prepared at an 80/20 (wt.%) HDPE/PA11 ratio. To enhance phase compatibility, high-density polyethylene grafted with maleic anhydride (HDPE-g-MA) was employed as a conventional compatibilizer at 1.5 wt.% content. In addition, the effect of silicon dioxide nanoparticles (nSiO2) incorporated at 2 and 4 wt.% contents was evaluated. The compositions were analyzed in the presence and absence of the compatibilizer. Mechanical, thermal, rheological, and morphological analyses showed that HDPE-g-MA led to a slight improvement in the interfacial interaction between the immiscible polymer phases. Moreover, the addition of nSiO2, in the presence of the traditional compatibilizer, led to the most favorable balance of thermal and mechanical performance, suggesting that nSiO2 nanoparticles may act as effective co-compatibilizers in HDPE/HDPE-g-MA/PA11 systems.