Estimating the phase diagrams of deep eutectic solvents within an extensive chemical space.

Assessing the formation of a deep eutectic solvent (DES) necessitates a solid-liquid equilibrium phase diagram. Yet, many studies focusing on DES applications do not include this diagram because of challenges in measurement, leading to misidentified eutectic points. The present study provides a practical approach for estimating the phase diagram of any binary mixture from the structural information, utilizing machine learning and quantum chemical techniques. The selected machine learning model provides reasonably high accuracy in predicting melting point (R2 = 0.84; RMSE = 40.53 K) and fusion enthalpy (R2 = 0.84; RMSE = 4.96 kJ mol-1) of pure compounds upon evaluation by test data. By pinpointing the eutectic point coordinates within an extensive chemical space, we highlighted the impact of the mole fractions and melting properties on the eutectic temperatures. Molecular dynamics simulations of selected mixtures at the eutectic points emphasized the pivotal role of hydrogen bonds in dictating mixture behavior.

Amino Acid Leaching of Critical Metals from Spent Lithium-Ion Batteries Followed by Selective Recovery of Cobalt Using Aqueous Biphasic System.

To reduce the exploitation of mine resources and decrease the harm to the environment caused by urban electronic wastes, the recovery of critical metals in secondary resources is crucial. In this study, we have successfully developed an eco-friendly process to integrate the leaching and separation of cobalt (Co) from a spent lithium-ion battery (LIB) cathode using an amino acid-based aqueous biphasic system (ABS). We, for the first time, demonstrated a simple method for leaching a LIB cathode using only amino acids. In addition, we have investigated the leaching mechanism using the typical cathode active material lithium cobalt oxide (LiCoO2). Then, the Co was selectively extracted by a biphasic system (amino acid-PPG400-H2O). This novel process has an excellent prospect in the field of spent-battery recycling because of its eco-friendly and process-simplified advantages.

Revisiting the seed-assisted synthesis of zeolites without organic structure-directing agents: insights from the CHA case.

Herein, the crystallization behaviour of the CHA zeolite synthesized via the seed-assisted method and in the absence of an organic structure-directing agent has been revisited. To date, the working hypothesis of the seed-assisted synthesis method is that the parent gel and seed share the common composite building unit (cbu) of the targeted zeolite crystal. In the case of the CHA zeolite, we reveal that the parent gel in the absence of CHA seeds leads to the formation of the MER zeolite, which does not follow the cbu working hypothesis. It appears that smaller, but essential common units, i.e., 4-membered ring (4-MR) aluminosilicate, play a key role, instead of a larger cbu. The parent gel contains 4-MRs, which can grow into MER and/or CHA, depending on several factors, i.e. alkalinity, Si/Al ratio, synergistic effects of Na+ and K+, and the seeds. In this study, the CHA zeolite with an Si/Al ratio of up to 15 was selectively crystallized in the presence of CHA seeds at suitable alkalinity ((Na2O + K2O)/SiO2 < 0.4) with a fixed point at the tie line of Na2O/SiO2 = 0.3 with K2O/SiO2 = 0.1. Subsequently, the ternary phase diagram was drawn as high alkalinity with (Na2O + K2O)/H2O > 0.4 showing the formation of an MER zeolite, a thermodynamically more stable phase than the CHA zeolite, whereas low alkalinity with (Na2O + K2O)/SiO2 < 0.4 showed the less crystalline CHA zeolite or amorphous products with MER as a competing phase. The crystallization of the CHA zeolite was found to be strongly dependent on the synergistic effects of sodium and potassium ions. The former appears to organize the 4-MRs into essential double-six rings (d6rs), while the latter arranges the formed d6rs into cha cages. The seeds are partially dissolved and provide the outer surface for the crystal growth of CHA. We anticipate that these results may provide useful insight for understanding the crystallization of zeolites and stimulate versatile design in the synthesis of zeolites, particularly for the industrially demanding seed-assisted technique.

Highly crystalline mesoporous SSZ-13 zeolite obtained via controlled post-synthetic treatment.

The generation of mesoporosity in SSZ-13 zeolite by means of desilication via post alkaline treatment normally results in severe damage to the microporous framework hence giving an undesirable decline in catalytic performance. Herein, we propose a post-synthetic desilication treatment that is controllable with an aim to preserve the high crystallinity of SSZ-13 zeolite during the formation of mesopores. The extent of desilication in alkaline media is controlled by deliberately leaving the organics within SSZ-13 frameworks as they can effectively hinder the attack of hydroxyl ions on siloxane bonds. The resulting SSZ-13 exhibits substantial development of mesoporosity with preserved high crystallinity and microporosity that can then be used to relieve the mass transport issues and lead to an increased activity of LDPE pyrolysis.