The present study was conducted to impregnate the surface of a carbon of vegetable origin with copper nanoparticles by the green synthesis method with the aqueous extract of Hibiscus sabdariffa flowers, rich in phenolic compounds, which are responsible for the reduction and impregnation of metal nanoparticles. Batch adsorption assays were conducted aimed at nitrate removal with pure (GAC) and impregnated (IGAC) carbon, for comparative purposes. It was found that impregnation increases the efficiency of the carbon by four times in terms of the maximum adsorption capacity, which was 10.13 mg g⁻¹ at 45°C for GAC and 45.01 mg g⁻¹ at 15°C for IGAC, indicating that this is a promising material for the removal of nitrate in waters with an excess of this ion.

A novel modification technique employing a layer-by-layer (LbL) self-assembly method, integrated with a pressure-assisted filtration system, was developed for enhancing a commercial polyethersulfone (PES) microfiltration (MF) membrane. This modification involved the incorporation of tannic acid (TA) in conjunction with graphene oxide (GO) nanosheets. The effectiveness of the LbL method was confirmed through comprehensive characterization analyses, including ATR-FTIR, SEM, water contact angle (WCA), and mean pore size measurements, comparing the modified membrane with the original commercial one. Sixteen variations of PES MF membranes were superficially modified using a three-factorial design, with the deposited amount of TA and GO as key factors. The influence of these factors on the morphology and performance of the membranes was systematically investigated, focusing on parameters such as pure water permeability (PWP), blue corazol (BC) dye removal efficiency, and flux recovery rate (FRR). The membranes produced with the maximum amount of GO (0.1 mg, 0.55 wt%) and TA as the inner and outer layers demonstrated remarkable FRR and significant BC removal, exceeding 80%. Notably, there was no significant difference observed when using either 0.2 (1.11 wt%) or 0.4 mg (2.22 wt%) in the first layer, as indicated by the Tukey mean test. Furthermore, the modified membrane designated as MF/TA_0.4GO_0.1TA_0.4 was evaluated in the filtration of a simulated dye bath wastewater, exhibiting a BC removal efficiency of 49.20% and a salt removal efficiency of 27.74%. In conclusion, the novel PES MF membrane modification proposed in this study effectively enhances the key properties of pressure-driven separation processes.

The aim of the present work was to evaluate the adsorption behaviour of tartrazine yellow dye using Moringa oleifera (moringa) seeds in a fixed bed, through the variation of operational parameters and evaluation of mathematical models. The results showed that the biosorption process showed higher efficiency when the column was operated at 1 mL min⁻¹ flow, with a height of 14 cm and pH 5 of the dye solution, which had a removal percentage of 44.89% and removal capacity of 0.504 mg g ⁻¹. When the adsorption models were applied, it was found that the Adams–Bohart model best represents the initial part of the rupture curve, whereas the Dose-Response model best reproduces the entire rupture curve. The regeneration experiments demonstrate that it is possible to regenerate the biosorbent and its removal capacity remains at approximately 33% from the 4th cycle, satisfactory results for the reuse of the moringa seeds in the removal of tartrazine dye.

A modified microfiltration membrane was prepared by flow-through coating method. Firstly the sulfuric acid solution was vacuum filtered on the polyethersulfone (PES) microfiltration membrane, providing the introduction of a sulfonic acid group to the backbone of PES. Sequentially, the polyethyleneimine solution was vacuum filtered to provide amine groups on the membrane surface. Finally, the graphene oxide solution, functionalized with different masses of tannic acid, was vacuum filtered on the membrane surface, producing the cross-linked modified membranes. These were efficient in the removal of anionic food coloring, achieving high removal rates and low fouling, compared to unmodified membrane. The best membrane in terms of bright blue dye removal was the MF PEI₅GO₁TA₄, capable of removing all the feed solution, and demonstrating its possibility of reuse in 5 cycles of operation.