Waste biomass (agave bagasse) and native birch wood were used as raw materials for a novel fractionation and derivation process to produce cellulose acetates (CAs). During the first stage of the fractionation process, a significant amount of hemicelluloses and lignin were dissolved from the biomass using a natural deep eutectic solvent (NADES) that consisted of a mixture of choline chloride and lactic acid with the molar ratio of 1:9. Then, the residual solid material was delignified by bleaching it with a mixture of acetic acid and sodium chlorite. The fractionation process generated differently purified pulps (celluloses) which were converted to CAs. The crystallinity index, polymerization degree, chemical composition, and thermal properties of the differently purified pulps and CAs were analyzed to evaluate the efficacy of the acetylation process and to characterize the CAs. The chemical derivation of the differently purified cellulose samples generated CAs with different degrees of substitution (DSs). The more purified the cellulose sample was, the higher its DS was. Moreover, some differences were observed between the acetylation efficiencies of birch and agave bagasse. Typically, cellulose purified from birch by treating it with NADES followed by bleaching was acetylated more completely (DS = 2.94) than that derived from agave bagasse (DS = 2.45). These results revealed that using green solvents, such as NADES, to treat both agave bagasse (waste biomass) and birch wood, allowed pure fractions to be obtained from biomass, and thus, biomass could be valorized into products such as CAs, which present a wide range of applications.

End-of-life (EoL) thin-film composite (TFC) reverse osmosis membranes were converted into ultrafiltration-like (UF) membranes in an accelerated degradation process of the polyamide (PA) using an oxidant (NaOCl) in the presence of either MgCl₂ or CaCl₂. The PA degradation was evaluated by measuring pure water permeability (PWP), MgSO₄ passage and molecular weight cut-off; the more PWP increased, and the less MgSO₄ was retained after treatment, the more the PA was degraded. By adding 10 mM of metal ions, PWP increased 2.1 (MgCl₂) and 3.1 (CaCl₂) times compared to the increase achieved with hypochlorite alone (2560 ppm∙h of free chlorine). Changes in the membranes after treatment were analyzed by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and by measuring their surface charge and contact angle. FTIR and FE-SEM confirmed the PA layer degradation. FE-SEM micrographs showed that full removal of the PA layer can be achieved by using an oxidation dose of 12,700 ppm∙h when Ca²⁺ is used but doses as high as 300,000 ppm*h are needed without catalyst. The results proved that by controlling the oxidation process it was possible to control the cut-off (MWCO) value of the membrane from 16,100 g∙mol^-1 to 27,100 g∙mol^-1. Before treatment, EoL membranes showed a MWCO of approximately 1200 g∙mol^-1, meaning that molecules with that size could be retained in a 90%. In summary, the presented method enables reducing waste by the conversion EoL membranes into tailored UF-like membranes and by decreasing the amount of oxidant used in the conversion process.

Commercially available ultrafiltration membranes were coated with cellulose nanofibers (CNFs) produced from softwood pulp by a two-step process: a non-derivatizing DES treatment and a simple mechanical treatment (high-speed homogenization and sonification). The CNFs coating aimed at enhancement of the removal of methylene blue (MB) from water and was investigated at different concentrations of the coating, quantified in grams of CNFs per square meter of the membrane (1.3, 6.5, 13, and 19.5 g/m²). The pure water permeability (PWP) was unaffected up to the concentration of 6.5 g/m² but the dye retention increased approximately 2.5-fold. Even higher improvement of MB removal, about 4-fold, was observed when 19.5 g/m² were used, however, the pure water permeability also decreased by about 30%. In addition, it was proved that the coating can be removed and created again several times which shows that the concept could be used to improve the retention of organic compounds when high permeability membranes are used.

Industries that require water with low hardness consume large amounts of NaCl for water softening. In this work, water softener spent brines were recovered and used as raw material in an electrolysis cell with cationic exchange membrane (CEM) to yield both sodium hypochlorite and sodium hydroxide amounts, which are the most common disinfectants used to sanitize production areas. Spent brines contained mainly an average of 4.5% NaCl, 650 mg L⁻¹ Ca²⁺, and 110 mg L⁻¹ Mg²⁺, the last two cations adversely affect the CEM and must be treated prior to the electrolytic process. Two hardness removal methods were evaluated separately—lime-soda ash and sodium hydroxide-soda ash softening—the last one being the most effective as total hardness was decreased by 99.98%. This pretreated spent brine was then introduced into the electrolysis cell. Experimental design comprised five level variations for current intensity, % NaCl, and time. The best operation conditions yielded 2800 mg L⁻¹ NaOCl for a 5% NaCl solution. By incorporating chlorine gas trap to increase OCl⁻ concentration a maximum of 7400 mg L⁻¹ NaOCl was achieved. Finally, biocidal activity was tested following sanitation protocols (NaOCl dilution level) on workbenches and a decrease in bacterial count of at least 5 logs under laboratory-controlled conditions.

End-of-life (EoL) reverse osmosis (RO) membranes were regenerated by an extended alkaline cleaning treatment (ACT) followed by polyelectrolyte (PE) deposition (coating). The effect of time delay between the ACT and PE coating on the membranes' stability and filtration properties was investigated. The permeance of the membranes increased more than twofold compared to the value exhibited by the EoL membrane before the ACT. Additionally, the surface charge decreased from -45 mV to -99 mV at pH 7.7, due to the ACT. However, the ACT-induced effects were predominantly time-dependent and were partially reversed over time. When the membrane was coated with one layer of polydiallyldimethylammonium chloride (PDADMAC) immediately after the ACT, the resulting membrane had approximately 800 g/mol molecular weight cut-off (MWCO) value and 30 L/(m² h bar) pressure-corrected flux (PCF). In comparison, if the membrane was stored in deionized (DI) water for five hours between the ACT and coating, the resulting membrane had again approximately 30 L/(m² h bar) PCF but a much higher 2,900 g/mol MWCO. Furthermore, the promptly coated membranes showcased better replicability and stability during storage, in comparison to the samples that were kept in water prior to coating.