Activation of waste paper: Influence of varied chemical agents on product properties

Chemical activation of willow with co-presence of FeCl3 tailors pore structure of activated carbon for enhanced adsorption of phenol and tetracycline

FeCl3 is a Lewis acid catalyzing condensation reaction, which might be beneficial for enhancing mass yield of activated carbon (AC) if used as a co-activator. Herein, this was verified by conducting activation of willow with various activators (ZnCl2, K2C2O4, H3PO4) in the presence/absence of FeCl3. The results indicated that FeCl3 competed with acid-catalyzed reactions induced by ZnCl2 or H3PO4, interfering aromatization and diminishing AC yields (from 40.8 % to 37.0 % with ZnCl2). In the activation with K2C2O4 + FeCl3, In-situ IR measurement showed that FeCl3 catalyzed polymerization reactions, but polymeric products were not stable and were further cracked with K2C2O4, reducing AC yield drastically from 27.6 % to 7.1 %. The co-presence of FeCl3 in the activation reduced overall specific surface area (1201.6 versus 1127.2 m2 g-1 for K2C2O4) by merging of micropores to form a higher percentage of mesopores (i.e. 2.0 % to 17.1 % for K2C2O4, and 9.2 % to 41.4 % for H3PO4). This pore restructuring significantly enhanced tetracycline adsorption (99.9 % removal for AC- K2C2O4 + FeCl3 versus 61.1 % for AC-K2C2O4 alone), while compromising phenol adsorption (48.7 % versus 96.1 %) due to reduced micropore availability. The reduced specific surface area was also attributed to the retention of inorganics by solid phase reactions between FeCl3 and K2C2O4 or H3PO4. Additionally, the presence of FeCl3 resulted in more fragmented surface of ACs generated from all activators.

Progress of 0D Biomass-Derived Porous Carbon Materials Produced by Hydrothermal Assisted Synthesis for Advanced Supercapacitors

Supercapacitors are garnering considerable interest owing to their high-power density, rapid charge-discharge capability, and long cycle life. Among the various materials explored, biomass-derived carbon nanomaterials stands out as a sustainable and cost-effective choice, thanks to its natural abundance and eco-friendly characteristics. This review delineates recent advances in the synthesis of zero-dimensional (0D) carbon nanomateirlas from various biomass precursors via hydrothermal assisted synthesis. It offers a comprehensive discussion on the factors affecting the synthesis of 0D carbon nanomaterials, including precursor type, concentration, reaction temperature, and time. Furthermore, the review underscores the impact of different activation methods on the morphology and electrochemical performance of 0D carbon nanomaterials. Finally, we outline the challenges and future prospects of utilizing biomass-derived carbon nanomaterials in supercapacitor applications, emphasizing the importance of optimizing synthesis parameters to attain the desired material properties.

Chemical activation of cotton fibers with varied regents induces distinct morphology of activated carbon and adsorption capacity of methylene blue

Some biomasses like cotton contain natural fibrous structures. This is a desirable structural feature for exposure of adsorption sites on cotton-derived activated carbon (AC). This was verified herein by conducting activation of cotton with ZnCl2, H3PO4, K2C2O4, or KOH, probing whether structural transformation during activation could be confined inside a cotton fiber. The results indicated that ZnCl2 showed the highest capability for generating pores (1432.8 m2·g-1), especially mesopores (> 50 %). This resulted from its highest activity for catalyzing the aromatization reactions associated with deoxygenation during the activation (C/O of 13.1 versus C/O of ca. 3.6 for counterparts). The intensive cracking from the potassium activators interfered with aromatization, retaining more oxygen but diminished pore development (ca. 1000 m2·g-1), especially mesopores (< 7 %). Furthermore, ZnCl2 catalyzed condensation of intermediates bearing CO and C-O-C, but KOH or K2C2O4 could not. ZnCl2 activation retained the fibrous structure of resulting activated carbon but induced the merge of fiber with the help of the formed reactive carbon cation, while H3PO4 led to the full deformation of fibers. Reactive "fiber intermediates" could also form in activation with KOH but not with K2C2O4, as K2C2O4 only catalyzed the transformation of inner structures. This work supports cotton pretreatment and chemical activation as a promising technique for creating porous AC with high adsorption capacity.

Waste paper-derived porous carbon via microwave-assisted activation for energy storage and water purification

The reuse of waste papers by conversion into valuable carbon materials has received considerable attention for diverse applications such as energy storage and water purification. However, traditional methods for converting waste papers into materials with suitable properties for specific applications are often complex and ineffective, involving consecutive carbonization and activation steps. Herein, we propose a simple one-step microwave (MW)-assisted synthesis for preparing waste paper-derived porous carbons (WPCs) for energy storage and water purification. Through a 30-min synthesis, WPCs with graphitic structure and high specific surface area were successfully produced. The fabricated WPCs exhibited outstanding charge storage capability with a maximum specific capacitance of 237.7 F g-1. Additionally, the WPC demonstrates a high removal efficiency for various dyes, achieving a maximum removal efficiency of 95.0% for methylene blue. The developed one-step MW synthesis not only enables the production of porous carbon from waste paper, but also offers a viable approach to address solid waste management challenges while simultaneously yielding valuable materials.