Laser-induced graphene (LIG) has recently gained significant attention for its potential application in various fields.Here, we show that the laser ablation of Kevlar fabric, polyimide (PI), and poly(ether)sulfone (PES) substrates results in the formation of a highly porous graphene with different physicochemical features. LIG powder was used as an adsorbent for the dye removal. The LIG materials obtained from each substrate exhibited a different macroporous structure and demonstrated relatively high efficiency in the adsorptive removal of cationic dye. The generation of graphene from each polymeric substrate was confirmed by characterizing the LIGs. We found that the laser power had a large influence on the formation and quality of the LIG; higher laser power increased the degree of graphitization and resulted in a more porous graphene structure, which eventually led to an increase in the adsorption capacity. The LIG's adsorption capability is hypothesized to be primarily due to the highly porous structure of LIG, while π−π and hydrophobic interactions were found to have a marginal influence on the adsorbent−adsorbate interactions. LIG derived from PI displayed the highest sorption capacity among different polymeric substrates tested. The maximum equilibrium methylene blue adsorption capacity was found to be 153.3 mg/g using the Langmuir model.

The worldwide push toward the reduction of carbon dioxide emissions has been the main motivation for finding a sustainable alternative to the conventional Haber–Bosch ammonia production process that has a significant carbon footprint. In this work, we focused on ammonia separation by replacing the condenser with an absorber column packed with metal halide solid absorbents. These salts had shown promise in selective separation of NH3 in the past, but more information on the cyclic operation and ammonia desorption conditions was needed. We used an automated apparatus equipped with an absorption column packed with either silica, supported CaCl2, or supported MgCl2 to explore the optimal absorption/desorption conditions (pressure and temperature swings). Primarily, we are reporting on the working capacity of various sorbents for cyclic ammonia separation. Additionally, we investigated the effect of sweep gas on the desorption efficiency and compared the absorbent performance among each other in terms of absorption working capacity and the purity of the ammonia product stream. We were able to achieve an NH3 stream with a purity of over 95%; in some of the tests, we achieved a coordination number as high as 2.5 molNH3 /molsalt, which is the highest ever reported for a dynamic flow breakthrough test. Our experiments further prove the significant potential that these salts possess to replace phase change condensation in the conventional ammonia synthesisnot only in a greener fashion but also more efficiently with a decreased equipment size, with reduced energy input in smaller scales, and with more flexibility to follow intermittent renewables.

Laser-induced graphene (LIG) materials have great potential in water treatment applications. Herein, we report the fabrication of a mechanically robust electroconductive LIG membrane with tailored separation properties for ultrafiltration (UF) applications. These LIG membranes are facilely fabricated by directly lasing poly­(ether sulfone) (PES) membrane support. Control PES membranes were fabricated through a nonsolvent-induced phase separation (NIPS) technique. A major finding was that when PES UF membranes were treated with glycerol, the membrane porous structure remained almost unchanged upon drying, which also assisted with protecting the membrane’s nanoscale features after lasing. Compared to the control PES membrane, the membrane fabricated with 8% laser power on the bottom layer of PES (PES (B)-LIG-HP) demonstrated 4 times higher flux (865 LMH) and 90.9% bovine serum albumin (BSA) rejection. Moreover, LIG membranes were found to be highly hydrophilic and exhibited excellent mechanical and chemical stability. Owing to their excellent permeance and separation efficiency, these highly robust electroconductive LIG membranes have a great potential to be used for designing functional membranes.

Ammonia separation using metal halide absorbents has been shown to be a viable path for ammonia production at lower pressure. This work reports on optimizing the operating parameters of the reaction−absorption process that can be adapted for large-scale processing. The experiments were executed in three different modes. First, the effect of reaction parameters on the production rate was studied. Then, the absorption conditions were investigated in a single-pass reaction-then-absorption mode to evaluate the effectiveness of the absorbent at different temperatures, pressures, and space velocities. Finally, fed-batch reactionabsorption tests were conducted in constant pressure to evaluate the process performance with optimized conditions and gain more in-depth understanding of the transient behavior of this process. Results suggest that the recycle flow rate and absorber temperature significantly influence the ammonia production rates. These findings were then used to optimize the performance of a continuous fed-batch ammonia production process at constant pressure. A production rate upward of 27 μmol g cat s −1 was obtained under the most optimized conditions, which is a factor of 14 greater than the best result reported earlier. The optimized conditions were then used to study the cyclic operation of the fed-batch reaction− absorption process in a cyclic process. A transient behavior was observed for the ammonia production, which could be attributed to the partial saturation of the absorber column. Stable performance of reaction-absorption process was demonstrated for more than nine cycles, with no decay in the performance of the absorber after relatively short regeneration cycles.

Ammonia is one of the most widely produced chemicals in the world. It is synthesized by reacting hydrogen and nitrogen gases at high temperature and high pressure. Over 180 million metric tonnes of ammonia produced annually accounts for 1%−2% of all global greenhouse gas (GHG) emissions, mainly due to the production of hydrogen via fossil fuel feedstocks. As such, making this process cheaper, more efficient, and less energy intensive has been a major focus of research for scientists and engineers throughout the past century. Modern research on ammonia production largely focuses on decarbonizing this process through a myriad of techniques, such as improving energy efficiency via intensification or electrification. This perspective provides insights into the progress made toward the intensification of thermocatalytic processes for ammonia synthesis under milder conditions, including alternative ammonia separation methods and better catalysts. We first review ammonia separation methods that can enable the transition from high-pressure to low-pressure ammonia manufacturing, including ammonia-selective membranes and sorbents. The performance of membranes for ammonia separation is discussed in terms of ammonia selectivity and permeance for a wide range of temperatures, with the focus on the strengths and limitations of both organic and inorganic materials. Recently developed sorbents that selectively uptake ammonia from gas mixtures are also discussed, with a special emphasis on the performance of absorbents at various experimental conditions. Since one of the potential prospects for decarbonizing ammonia synthesis lies in creating a catalyst that can operate at a lower temperature, catalytic materials that have been reported in the last two decades and can sustain production rates at temperatures below 400 °C are reviewed.