This research focused on the synthesis of a functional alginate-based material via chemical modification processes with two steps: oxidation and reductive amination. In previous alginate functionalization with a target molecule such as cysteine, the starting material was purified and characterized by UV-Vis, ¹H-NMR and HSQC. Additionally, the application of FT-IR techniques during each step of alginate functionalization was very useful, since new bands and spiked signals around the pyranose ring (1200–1000 cm⁻¹) and anomeric region (1000–750 cm⁻¹) region were identified by a second derivative. Additionally, the presence of C₁-H₁ of β-D-mannuronic acid residue as well as C₁-H₁ of α-L-guluronic acid residue was observed in the FT-IR spectra, including a band at 858 cm⁻¹ with characteristics of the N-H moiety from cysteine. The possibility of attaching cysteine molecules to an alginate backbone by oxidation and post-reductive amination processes was confirmed through ¹³C-NMR in solid state; a new peak at 99.2 ppm was observed, owing to a hemiacetal group formed in oxidation alginate. Further, the peak at 31.2 ppm demonstrates the presence of carbon -CH₂-SH in functionalized alginate—clear evidence that cysteine was successfully attached to the alginate backbone, with 185 μmol of thiol groups per gram polymer estimated in alginate-based material by UV-Visible. Finally, it was observed that guluronic acid residue of alginate are preferentially more affected than mannuronic acid residue in the functionalization.

Aiming to mitigate disposal and water pollution problems, biochars were prepared from cocoa pod husk (CPH) waste for application in artificial wastewater simulating real conditions of textile effluents. Therefore, the morphological properties of biochars obtained via one/two step NaOH activation were compared and characterized by XRD, Raman spectroscopy, FESEM/EDS and the BET technique. According to these results, biochar obtained from the one-step method (AQ₁) was chemically characterized by Boehm titration as well as the point of zero charge and used for the removal of a mixture of brilliant green (BG), rhodamine B (RB) and methyl orange (MO) as artificial wastewater. To evaluate the remaining concentration of each dye after adsorption without previous separation, a derivative spectrophotometry method was applied because some overlap will occur. In order to overcome this problem, adequate wavelengths for each dye in the mixture were established: BG = 631, RB = 592 and MO = 377 nm. Additionally, optimum conditions were determined such as pH 6 and a dosage of 50 mg and the effect of the initial dye concentration was studied in the range of 5–20 mg L⁻¹. The adsorption rate of the ternary dye mixture was fitted to the pseudo second-order model and the affinity of AQ₁ towards each dye was in the following order: BG > RB > MO. Furthermore, the adsorption isotherm data were described by multi-component Langmuir and Freundlich models. Finally, the presence of sodium chloride was explored and the synergetic effect in the removal of BG and MO was demonstrated, whereas the adsorption of RB was not promoted under the influence of this salt widely used in the textile industry.