Methylene Blue (MB) is a dye widely used in the industrial sector and in human and veterinary pharmacology. This dye, if improperly disposed of, can cause a significant environmental impact due to its low biodegradability, as it is a stable and complex substance. Additionally, it may affect human health and generate highly toxic byproducts. Hence, the purpose of this work is to assess the removal efficiency of MB from a synthetic effluent using a ionic flocculation process. Such a process consists of the dissolution of a biodegradable anionic surfactant (obtained from soybean oil used for frying food) in the synthetic effluent and the subsequent addition of calcium to the system. The addition of Ca leads to the formation of insoluble surfactant flocs with a high capacity to adsorb organic pollutants. The FTIR testing showed the presence of OH⁻ and C=O groups in the surfactant flocs, which favor the removal of MB by an adsorption process. The maximum adsorption capacity of MB was 101.38 mg g⁻¹. The process is in fact a chemisorption and has an exothermic nature. Desorption studies showed a desorption efficiency of up to 47.81% using an ethanol 1:2 solution. An MB removal efficiency of up to 93.71% was attained in just 0.5 min for an initial MB concentration of 100 mg L⁻¹, showing that ionic flocculation is a very fast and effective process for the treatment of effluents.

Emerging pollutants (EPs) have recently been reported to affect the quality of water and pose high risks to human health. The recalcitrant behavior of the drug hydrochlorothiazide (HCT) in wastewater, for example, highlights the need to develop new treatments that are more efficient in removing this pollutant. In this study, the removal of hydrochlorothiazide from a synthetic pharmaceutical effluent through micellar ionic flocculation was evaluated, using a biodegradable anionic surfactant, derived from natural materials such as coconut oil and animal fat. The effects of different parameters, such as contact time, stirring speed, temperature, surfactant concentration and pH on drug removal efficiency were assessed. Under optimal processing conditions: [HCT] = 20 ppm, [surfactant] = 300 ppm, 1:2 calcium/surfactant ratio, temperature 30 °C, contact time 5 min, fast stirring speed 100 rpm, slow stirring speed 50 rpm and pH 10, HCT removal efficiency reached 88%, indicating that ionic flocculation using base soap is a promising technique in the treatment of pharmaceutical effluents contaminated by hydrochlorothiazide. The desorption kinetics of HCT from the floc surface were also analyzed, confirming that desorption is governed by the pseudo-second order, where interactions between the polar group of the base soap (COOH⁻), Ca⁺² ions and HCT (C₇H₈ClN₃O₄S₂) detach the HCT molecules present in the flocs. Moreover, 15% of HCT was spontaneously desorbed after 40 min. Graphical Abstract

The impacts of inadequate disposal of industrial wastewater cause environmental, economic, social and human health damage. The search for innovative and viable methodologies from a technical and economic standpoint aims to promote suitable management of effluents produced by different industrial activities. The objective of this paper was to study phenol, aromatic alcohol and aromatic amine removal using cloud point extraction based on analysis of extraction capacity, miscibility curves, equilibrium lines, distribution coefficients and mass transfer solubilisation diffusion. The oxo-C₁₀E₃P₄E₂ surfactant produced the best results, exhibiting smaller coacervate volume fractions, low concentration in the diluted phase and efficient extraction (E%) of phenol (81.79%), 1-phenylethanol (67.88%), 2-phenylethanol (65.41%), benzyl alcohol (57.01%), aniline (56.91%), p-toluidine (73.96%) and 2,4-dimethylaniline (84.87%). The ternary phase diagrams revealed a large miscibility area favourable to extraction, with equilibrium lines showing a pronounced slope in favour of the coacervate, indicating high compound concentration factors. Equilibrium isotherms were used to obtain the distribution and solubilisation constants (Log K_C/D K_S), in the following order: aniline (1.05; 9.15) < p-toluidine (1.35; 20.40) < 2,4-dimethylaniline (1.76; 45.10) and benzyl alcohol (1.07; 8.19) < 2-phenylethanol (1.22; 14.04) < 1-phenylethanol (1.28; 15.23) < phenol (1.59; 36.72). These parameters show a linear correlation with Log K_O/W, revealing that micellar solubilisation is governed by the hydrophobic nature of aromatic organic compounds. The evolution of pH demonstrated that the ionised forms of phenol and 2,4-dimethylaniline do not establish interactions (electrostatic, van der Waals, hydrogen bonds) with surfactants. Mass transfer diffusion is governed by hydrophobic compounds, slightly compromising phenol due to its high solubility in water.

The textile industry is one of the main generators of industrial effluent due to the large volumes of water containing a wide variety of pollutants, including dyes. Thus, the present study aimed to remove the Disperse Blue 56 dye present in synthetic textile effluent using ionic flocculation through surfactant flocs produced from animal/vegetable fat, assessing the system at different surfactant concentrations and temperatures. The process kinetics, adsorption mechanism and equilibrium were evaluated. The results show that the kinetics was better described by the Elovich model when compared to pseudo-first order and pseudo-second order models, indicating that chemical adsorption occurs during the process. The study of the adsorption mechanism obtained lower outer layer diffusivities than their intra-particle counterparts, demonstrating that the dye transport to the surfactant floc is controlled through the outer layer. The Langmuir isotherm was suitable for equilibrium data and the separation factor calculated showed that the isotherm is classified as favorable. Dye removal efficiency reached 87% after 360 minutes of contact between the effluent and the surfactant flocs, indicating that ionic flocculation is an efficient alternative in the treatment of textile effluent containing disperse dye.