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Methylene blue is a cationic dye used for dyeing cotton, wool, and silk. This dye can cause impacts when reaching water resources due to the reduction of sunlight infiltration, besides the health problems if ingested. Therefore, the complete removal of this contaminant in industrial effluents is indispensable. Currently, soybean hulls residues are used in animal feed supplementation; however, since soybean oil production is large, expressive quantities is discarded in landfills. Thus, the present study aim is to evaluate the adsorption capacity of methylene blue onto soybean hulls as an alternative use of this agroindustrial residue. The material was characterized through morphological and chemical analysis which showed porosity, heterogeneity, and functional groups that favor the adsorption. Due to the mainly negative charge of the surface, the pH did not affect the cationic dye uptake, enabling a wide pH range. After the adsorption studies, the best experimental conditions were at temperatures of 298 K, mass of 0.025 g, and contact time of 180 min, resulting in the maximum adsorption capacity of 169.90 mg g−1. When compared with other low‐cost biosorbent and activated carbons, it can be perceived a potential applicability of soybean hulls in wastewater treatment as an alternative use.

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Industrial effluents are sewage from industrial processes, such as polluted cooling waters and waters used for cleaning. It is extremely important that these contaminated waters undergo treatment to allow for water reuse or safe disposal, without damage to the environment. In the present work, the efficacy of coagulating/flocculating aqueous solutions containing reactive black 5 (RB5) dye was evaluated using protein fractions derived from Moringa oleifera seeds (albumin and globulin) as natural coagulants functionalized with iron oxide magnetic nanoparticles. The application of a magnetic field during sedimentation allowed for faster settlement of the dye particles and their separation. Variations in parameters such as the protein concentration, nanoparticle concentration, solution pH, dye concentration, and the presence or absence of an alkalizing agent were assessed. Moreover, the sedimentation time was analyzed with and without the magnetic field and with the reuse of iron oxide nanoparticles. The functionalized magnetic coagulants were able to remove more than 90 % of RB5 dye within 5 min of sedimentation. Figure 11. Influence of the presence of an alkalizing agent (concentration of AlbFe (a): 115 mg L À1 ; concentration of GloFe (b): 200 mg L À1 ; pH: 6; and dye concentration: 20 mg L À1 ).