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.

Most dyes are complex organic molecules that are highly resistant to degradation and may cause severe damage to live organisms and photosynthetic activities. In this respect, the aim of the present study was to assess the influence of interfacial, thermodynamic and hydrophobic parameters on Acid Red 57 removal from aqueous media by ionic micellar flocculation using surfactants sodium dodecanoate (C12), sodium tetradecanoate (C14) and sodium hexadecanoate (C16). The results demonstrate that an increase in the hydrophobic nature of the surfactant provokes different Krafft (T_krafft) temperature and critical micelle concentration behaviors, and the greater the hydrophobicity the higher the solubilization temperature and lower the concentration needed for micelle formation. It was also found that long-chain surfactants cause an increase in the area of the polar part of the surfactant and change the micelle shape from lamellar (C12, C14) to cylindrical (C16), interfering in the solubilization capacity of the micelles. Micelle diameter determination aimed at demonstrating that the dye is solubilized inside the micelles via hydrophobic interactions. The dye removal tests showed that an increase in surfactant concentration improves process efficiency, surfactant C12 exhibiting the best dye removal indices (around 90%). Thermodynamic parameters showed that ionic micellar flocculation is exothermic and non-spontaneous.

Diclofenac is a highly toxic anti-inflammatory detected in effluents and wastewater treatment plants. Adsorption is one of the most widely applied technologies to remove micropollutants using activated carbon, but requires a costly and inefficient separation stage, compromising adsorption. In this respect, a novel process is proposed based on ionic micellar flocculation-assisted adsorption (IMFA) using the surfactant sodium dodecanoate to increase adsorption capacity and facilitate phase separation. The efficiency of adsorption and IMFA was assessed based on a kinetic study, equilibrium isotherms, thermodynamic and kinetic separation properties. Adsorption kinetics followed the pseudo-second model indicating a process governed by ionic exchange between sodium diclofenac and the ions present in the activated carbon layers and dodecanoate, with velocity constants of 8.51 and 5.24 g.mg⁻¹.min⁻¹, respectively. Based on the equilibrium isotherms, the maximum adsorption capacity obtained was 49.43 and 51.85 mg.g⁻¹ in adsorption and IMFA, respectively, best represented by the Langmuir adsorption model, assuming adsorption on homogeneous surfaces in the form of monolayers. Thermodynamic analysis revealed that the processes occurred spontaneously, exothermically and that randomness declines at the solid-solution interface. Sedimentation analysis showed that the higher the surfactant concentration the greater the compaction height, higher the decantation speed, and shorter the wastewater clarification time.

Liquid-liquid equilibrium data were measured and analyzed for two ternary systems (biodiesel + methanol + glycerol and methyl palmitate + methanol + glycerol). Biodiesel, produced by the conventional chemical route at 60 °C for 60 min, using methanol and soybean oil at a molar rate of 10:1 and potassium hydroxide concentration (KOH) of 1 wt% exhibited thermal decomposition at temperatures between 100 and 250 ºC, reaching mass loss of approximately 98.8%, confirming soybean oil conversion into biodiesel by gas chromatography and thermogravimetry. Tie line composition quality was verified using Othmer-Tobias and Hand correlation equations. The distribution and selectivity coefficients were calculated for the immiscibility regions. The experimental tie line data exhibited good correlation in the UNIQUAC and NRTL thermodynamic models. The biodiesel system displayed deviations of 0.66 and 0.53% for the UNIQUAC and NRTL models, respectively. In addition, the methyl palmitate system showed a 1.23 and 0.48% deviation for the UNIQUAC and NRTL model, respectively. The individual behavior of the main biodiesel esters , based on the UNIQUAC model parameters, demonstrated that the type of fatty acid does not interfere in model correlation, likely due to the similarity between their composition and properties.