Hollow fiber membrane contactors have several advantages that make them a good alternative to conventional absorption processes in the gas industry, and they have attracted the interest of many researchers. However, critical issues such as wetting hinder applications of membranes on a wide scale. Wetting is the penetration of the liquid absorbent through membrane pores, reducing mass transfer and consequently affecting the CO2 absorption efficiency and lowering the effectiveness of the separation process. The availability of membranes that can maintain a high efficiency and remain stable over a long period of operation is the main factor that is required in order to implement membranes in the industry for absorption processes. The wetting phenomenon in hollow fiber membranes is the focus of this review, which offers a critical examination of the literature published on membrane wetting, highlighting the main factors that control the effectiveness of the membrane separation process. These factors include the liquid absorbent, the membrane morphology represented by pore size and porosity, and the mutual interaction between liquid absorbents and the membranes. All of these factors are discussed in detail in view of a better understanding of the wetting phenomenon. Furthermore, methods and approaches to prevent wetting in addition to perspectives for future research in the area are presented.

Carbon dioxide conversion into useful products has been gaining considerable attention as a global‐warming‐mitigation technique. The electrochemical conversion of CO2 into high‐value chemicals involves the utilization of electrical energy in the presence of an effective catalyst. The process products depend on the number of transferred electrons during the reaction and the characteristics of the electrode. Recently, electrodes coupled with active catalysts have been used to convert CO2 into valuable products including formic acid, hydrocarbons, and syngas. This review offers an overview of the recent literature on the electrochemical conversion of CO2 to valuable products, with an emphasis on the production of formate/formic acid. In addition, it compares the main features of electrochemical conversion to other techniques and summarizes their key advantages. It also provides future perspective for research and development, such as the need for novel and selective catalysts to obtain high conversion and product yield with low energy consumption.

The treatment of tannery effluent is of great interest as it contains a complex mixture of pollutants, primarily chromium. The disposal of this wastewater can have adverse effects on the environment and aquatic life, which is an emerging problem for the environment. In this work, electrocoagulation is used to remove chromium from real tannery wastewater, focusing on performance optimization and sludge characterization. Electrocoagulation experiments were conducted using an electrochemical cell with iron electrodes immersed in a specific volume of tannery wastewater. Operating parameters, such as the initial chromium concentration, pH and current density as well as power consumption were evaluated to determine optimum chromium removal. The optimization was performed using Response Surface Methodology combined with central composite design. Analysis of variance (ANOVA) was used to determine the response, residual, probability, 3D surface and contour plots. The maximum chromium removal was 100% at the optimum values of 13 mA/cm2, 7 and 750 ppm for current density, pH and concentration, respectively.

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Carbon capture and sequestration (CCS) is taking the lead as a means for mitigating climate change. It is considered a crucial bridging technology, enabling carbon dioxide (CO2) emissions from fossil fuels to be reduced while the energy transition to renewable sources is taking place. CCS includes a portfolio of technologies that can possibly capture vast amounts of CO2 per year. Mineral carbonation is evolving as a possible candidate to sequester CO2 from medium-sized emissions point sources. It is the only recognized form of permanent CO2 storage with no concerns regarding CO2 leakage. It is based on the principles of natural rock weathering, where the CO2 dissolved in rainwater reacts with alkaline rocks to form carbonate minerals. The active alkaline elements (Ca/Mg) are the fundamental reactants for mineral carbonation reaction. Although the reaction is thermodynamically favored, it takes place over a large time scale. The challenge of mineral carbonation is to offset this limitation by accelerating the carbonation reaction with minimal energy and feedstock consumption. Calcium and magnesium silicates are generally selected for carbonation due to their abundance in nature. Industrial waste residues emerge as an alternative source of carbonation minerals that have higher reactivity than natural minerals; they are also inexpensive and readily available in proximity to CO2 emitters. In addition, the environmental stability of the industrial waste is often enhanced as they undergo carbonation. Recently, direct mineral carbonation has been investigated significantly due to its applicability to CO2 capture and storage. This review outlines the main research work carried out over the last few years on direct mineral carbonation process utilizing steel-making waste, with emphasis on recent research achievements and potentials for future research.