This study explores the production of adsorbents from grape pomace (Vitis vinifera L.) via subcritical water hydrolysis (SWH) and their application as sustainable materials for removing fermentation inhibitors. Grape pomace, an abundant lignocellulosic byproduct of the wine industry, underwent SWH to yield a hydrolysis residue, which was subsequently chemically and thermally modified to generate various adsorbents (C2-C4). Among these, the C4 material, activated with phosphoric acid and treated under autoclave conditions, exhibited the most favorable properties, including a high surface area (777.2 m2 g-1), microporosity, surface acidity, and negative surface charge. Batch and fixed-bed adsorption experiments confirmed C4's superior capacity to selectively adsorb inhibitory compounds such as acetic acid, 5-hydroxymethylfurfural (5-HMF), and furfural, while preserving fermentable sugars. The adsorption mechanisms were comprehensively analyzed using kinetic, equilibrium, and thermodynamic models. Adsorption was determined to be spontaneous and endothermic, primarily governed by physisorption, as evidenced by low activation energies and favorable thermodynamic parameters. Regeneration studies demonstrated that C4 could be effectively reused for over five cycles with minimal loss of adsorption capacity, particularly for furfural and 5-HMF, using alkaline water as the eluent. The practical utility of C4 was validated through fermentability tests, which demonstrated significantly improved performance in detoxified hydrolysates, including a 3.2-fold increase in ethanol production compared to nondetoxified samples, as well as xylitol production. Overall, this study highlights the promise of subcritical hydrochar produced from water as an affordable, effective, and eco-friendly adsorbent suitable for biorefinery processes.
This article provides a comparative analysis of sustainable polymer membranes based on biopolymers and Nafion in the context of proton exchange membrane (PEM) for water electrolyzers. Nafion, a perfluorinated polymer, has been a standard choice for PEM applications due to its excellent proton conductivity and chemical stability. However, the sustainability challenges associated with its production, lifecycle and cost necessitate the exploration of alternative materials that may offer comparable performance while being environmentally friendly. The most promising alternative polymer for PEM electrolyzers appears to be cellulose with good thermal stability at 200 °C and a water absorption of 35%, which is slightly higher compared to Nafion membranes with a water absorption value of around 30%. Sustainable PEMs also have much lower hydrogen permeability, e.g., chitosan has been determined to have a permeability of 7 barrers, while Nafion is characterized by a value of more than 100 barrers. The biggest drawbacks of sustainable membranes are proton conductivity and durability, where Nafion membranes are still superior. This review also focuses on mechanical properties, chemical resistance, preparation methods and cost-effectiveness. Sustainable polymers show promising properties for supporting efficient hydrogen production, especially in dynamic operating environments facilitated by renewable energy sources.
Resilient chemistry is becoming a major theme of sustainable chemistry and is being incorporated into innovative curriculum tools. We propose an initial set of ten principles with the acronym RESILIENCE, to help accelerate development of this theme.
In our previous work, we introduced a new notation system for chemical formulas that was intended to address common misconceptions in chemistry education. This notation helps to clarify the differences between chemical entities and species, which is often a challenge for students and educators. We recommend writing molecular substances always as molecular formulas and never as empirical formulas, and chemical species considering their structure, using slashes (//) to indicate layered structures, and curly brackets ({}) for reticulums to enhance the comprehension of chemical structures in educational contexts. For example, boron trichloride is noted as BCl3, gallium trichloride as Ga2Cl6, aluminum trichloride as /AlCl3/, and sodium chloride as {NaCl}. We now propose to expand this notation by incorporating coordination numbers. In general, we propose the substance /A m B n / is a layered structure, and {A m Bn } is a reticulum in which A has a coordination number of n, and B has a coordination number of m. Thus, chemical formulas can provide deeper insights into the crystalline structures of both mono- and polyelemental substances. Our testing with professors and students demonstrated that this approach significantly improves our understanding of chemical structures. Furthermore, we discuss the scope and limitations of this notation system, acknowledging its potential shortcomings when applied to more complex structures, such as wollastonite, and the limitation of distinguishing among the different titanium oxide structures. Nonetheless, this refined notation system holds promise for advancing the study of solid-state chemistry and enhancing the teaching of advanced inorganic chemistry courses.
MID1sc10 is an engineered zinc esterase that was evolved to high activity (k cat/K m similar to 106 M-1s-1) and enantiospecificity over ten rounds of mutagenesis and screening. Although its evolutionary trajectory had stagnated, there is potentially room for further augmenting this enzyme's catalytic efficiency. As atomistic details could provide valuable insights for developing an even more efficient enzyme, we used quantum mechanics/molecular mechanics calculations to characterize MID1sc10's reaction mechanism. Our data suggest that the reaction occurs via a two-step process, involving metal ion-mediated ester cleavage followed by regeneration of the zinc coordination site. The initial step is rate-limiting, with a Gibbs energy barrier of 15.1 kcalmol-1, in good agreement with the experimental value (k cat = 1.64 s-1, Delta G double dagger = 17.3 kcalmol-1). Additionally, detailed atomistic and energetic information was used to retrospectively rationalize how the introduction or removal of charged residues during directed evolution optimized MID1sc10. Applying the same method to predict mutations to increase the efficiency of MID1sc10 suggested that mutating Asp25, Glu26, Asp74, or Glu81 to neutral polar or positively charged residues, or replacing Val62 or Gln66 with negatively charged residues, would help stabilize the rate-limiting transition state.
