Water scarcity is a pressing global issue driving the need for efficient and sustainable water reuse and desalination technologies. In the last two decades, humidification–dehumidification (HDH) has emerged as a promising method for small-scale and decentralized systems. This paper presents a comprehensive review of recent scientific literature highlighting key advancements, challenges, and potential future directions of HDH research. Because the HDH process suffers from low heat and mass transfer, as well as thermodynamic limitations due to the mild operating conditions, this work indicates three main strategies for HDH enhancement: (1) Advanced Heat and Mass Transfer Techniques, (2) Integration with Other Technologies, and (3) Optimization of System Operative Conditions. Particularly for advanced HDH systems, the reference GOR values exceed 3, and certain studies have demonstrated the potential to achieve even higher values, approaching 10. In terms of recovery ratio, there appear to be no significant process constraints, as recycling the brine prepared in innovative schemes can surpass values of 50%. Considering electricity costs, the reference range falls between 1 and 3 kWh m^–3. Notably, multi-stage processes and system couplings can lead to increased pressure drops and, consequently, higher electricity costs. Although consistent data are lacking, a baseline SEC reference value is approximately 360 kJ kg^–1, corresponding to 100 kWh m^–3. For comparable SEC data, it is advisable to incorporate both thermal and electric inputs, using a reference power plant efficiency of 0.4 in converting thermal duty to electrical power. When considering the utilization of low-temperature solar and waste heat, the proposed exergy-based comparison of the process is vital; this perspective reveals that a low-carbon HDH desalination domain, with II-law efficiencies surpassing 0.10, can be achieved.

Climate change necessitates urgent actions to mitigate carbon dioxide (CO₂) emissions from fossil fuel-based energy generation. Among various strategies, the deployment of carbon capture and storage (CCS) solutions is critical for reducing emissions from point sources such as power plants and heavy industries. In this context, cryogenic carbon capture (CCC) via desublimation has emerged as a promising technology. While CCC offers high separation efficiency, minimal downstream compression work, and integration potential with existing industrial processes, challenges such as low operating temperatures and equipment costs persist. Ongoing research aims to address these hurdles in order to optimize the desublimation processes for widespread implementation. This review consolidates diverse works from the literature, providing insights into the strengths and limitations of CCC technology, including the latest pilot plant scale demonstrations. The transformative potential of CCC is first assessed on a theoretical basis, such as thermodynamic aspects and mass transfer phenomena. Then, recent advancements in the proposed process configurations are critically assessed and compared through key performance indicators. Furthermore, future research directions for this technology are clearly highlighted.

As a triatomic allotrope of oxygen, ozone has many industrial and consumer applications because of its high oxidation potential and disinfectant properties. Most of the ozone is currently produced by corona discharge reactors using high-purity oxygen as the feed gas, where the conversion to ozone is typically 6−15 wt%. Given the high operating costs associated with the unreacted oxygen, it is essential to recover the oxygen for recycling to the ozone generator. This paper aims for the first time to design, simulate and assess cyclic adsorption processes for recovering oxygen from a mixture of ozone and oxygen (O₃:O₂ = 10:90 wt%) produced by a commercial ozone generator. A 2-bed, 2-step cycle was first investigated in which ozone is selectively adsorbed at high pressure and then desorbed by dry air used as a sweep gas. However, it was found that the O₂ purity in the recycle stream was too low because of the nitrogen build up from air. Thus, two additional cycles, namely a 3-bed, 3-step cycle incorporating an oxygen purge step and a 3-bed, 4-step cycle incorporating a vacuum blowdown step, were evaluated with the purpose of removing nitrogen from the bed after the desorption step. Both adsorption cycles achieved a satisfactory O₂ purity of 98+% in the recycle stream with a sacrifice of O₂ recovery and an increase in energy consumption, respectively. As a result, the adsorption processes devised in this study could serve to significantly reduce the oxygen consumption in industrial ozone generators.

: Climate change necessitates urgent actions to mitigate carbon dioxide (CO2) emissions from fossil fuel-based energy generation. Among various strategies, the deployment of carbon capture and storage (CCS) solutions are critical for reducing emissions from point sources such as power plants and heavy industries. In this context, cryogenic carbon capture (CCC) via desublimation has emerged as a promising technology. While CCC offers high separation efficiency, minimal downstream compression work, and integration potential with existing industrial processes, challenges such as low operating temperatures and equipment costs persist. Ongoing research aims to address these hurdles in order to optimize the desublimation processes for widespread implementation. This review consolidates diverse literature works, providing insights into the strengths and limitations of CCC technology, including the latest pilot plant scale demonstrations. The transformative potential of CCC is first assessed on a theoretical basis, such as thermodynamic aspects and mass transfer phenomena. Then, recent advancements in the proposed process configurations are critically assessed and compared through key performance indicators. Furthermore, future research directions for this technology are clearly highlighted.