Environmental issues related to greenhouse gases (GHG) emissions have pushed the development of new technologies that will allow the economic production of low-carbon energy vectors, such as hydrogen (H₂), methane (CH₄) and liquid fuels. Dry reforming of methane (DRM) has gained increased attention since it uses CH₄ and carbon dioxide (CO₂), which are two main greenhouse gases (GHG), as feedstock for the production of syngas, which is a mixture of H₂ and carbon monoxide (CO) and can be used as a building block for the production of fuels. Since H₂ has been identified as a key enabler of the energy transition, a lot of studies have aimed to benefit from the environmental advantages of DRM and to use it as a pathway for a sustainable H₂ production. However, there are several challenges related to this process and to its use for H₂ production, such as catalyst deactivation and the low H₂/CO ratio of the syngas produced, which is usually below 1.0. This paper presents the recent advances in the catalyst development for H₂ production via DRM, the processes that could be combined with DRM to overcome these challenges and the current industrial processes using DRM. The objective is to assess in which conditions DRM could be used for H₂ production and the gaps in literature data preventing better evaluation of the environmental and economic potential of this process.

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.