Preparing a magnetic activated carbon with expired beverage as carbon source and KOH as activator

In-situ synthesis of ZIF-8 on magnetic pineapple leaf biochar as an efficient and reusable adsorbent for methylene blue removal from wastewater

The presence of organic dyes in aquatic systems poses a significant threat to ecosystems and human well-being. Due to recycling challenges, traditional commercial activated carbon is not cost-effective. To address this, an imidazolate acid zeolite framework-8 (ZIF-8)-modified magnetic adsorbent (ZMPLB-800) was synthesized through the in-situ formation of ZIF-8 and subsequent carbonization at 800 °C, using magnetic pineapple leaf biochar (MPLB) as a carrier. The porous structure of ZMPLB-800 facilitates the rapid passage of dye molecules, enhancing adsorption performance. ZMPLB-800 exhibited remarkable adsorption capacity for methylene blue (MB) across a pH range of 3-13, with a maximum adsorption capacity of 455.98 mg g-1. Adsorption kinetics and thermodynamics followed the pseudo-second-order kinetic model and Langmuir isotherm model. Mechanisms of MB adsorption included pore filling, hydrogen bonding, electrostatic interactions, π-π interactions, and complexation through surface functional groups. Additionally, ZMPLB-800 demonstrated excellent regeneration performance, recording a removal efficiency exceeding 87% even after five adsorption/desorption cycles. This study provides a novel strategy for treating dye wastewater with MOF composites, laying the foundation for waste biomass utilization.

Production of Activated Carbons from Food/Storage Waste

This paper deals with the adsorption of organic and inorganic pollutants on the surface of carbonaceous adsorbents prepared via the chemical activation of expired or broken food products-the solid residue of the "cola-type" drink as well as spoilt grains of white rice and buckwheat groats. The activation process was conducted in the microwave furnace with the use of two activating agents of different chemical nature-potassium carbonate and orthophosphoric acid. The activated carbons were characterized based on the results of elemental analysis, low-temperature nitrogen adsorption/desorption, Boehm titration, thermal analysis, and scanning electron microscopy. Additionally, the suitability of the materials prepared as the adsorbents of methylene blue and iodine from the aqueous solutions was estimated. The materials obtained via chemical activation with H₃PO₄ turned out to be much more effective in terms of both model pollutant adsorptions. The maximum sorption capacity toward iodine (1180 mg/g) was found for the white-rice-based activated carbon, whereas the most effective in the methylene blue removal (221.3 mg/g) was the sample obtained from the solid residue of the expired "cola-type" drink. For all carbonaceous materials, a better fit for the experimental adsorption data was obtained with the Langmuir isotherm model than the Freundlich one.

Advances in Micro-/Mesopore Regulation Methods for Plant-Derived Carbon Materials

In recent years, renewable and clean energy has become increasingly important due to energy shortage and environmental pollution. Selecting plants as the carbon precursors to replace costly non-renewable energy sources causing severe pollution is a good choice. In addition, owing to their diverse microstructure and the rich chemical composition, plant-based carbon materials are widely used in many fields. However, some of the plant-based carbon materials have the disadvantage of possessing a large percentage of macroporosity, limiting their functionality. In this paper, we first introduce two characteristics of plant-derived carbon materials: diverse microstructure and rich chemical composition. Then, we propose improvement measures to cope with a high proportion of macropores of plant-derived carbon materials. Emphatically, size regulation methods are summarized for micropores (KOH activation, foam activation, physical activation, freezing treatment, and fungal treatment) and mesopores (H3PO4 activation, enzymolysis, molten salt activation, and template method). Their advantages and disadvantages are also compared and analyzed. Finally, the paper makes suggestions on the pore structure improvement of plant-derived carbon materials.

Enhanced removal of bisphenol A using pine-fruit shell-derived hydrochars: Adsorption mechanisms and reusability

We synthesized NaOH-activated hydrochars via hydrothermal carbonization (HTC) of Brazilian pine fruit shells at HTC residence times of 24, 48, and 72 h. The hydrochars were used as adsorbents to remove bisphenol A (BPA) from aqueous solutions. The surface area of the samples can reach up to 2220 m² g^-1, and the maximum adsorption of BPA onto the surfaces was achieved at a pH of 7.0 (708 mg g^-1). Adsorption occurred mainly via monolayer formation with a low retention time of the adsorbate (τ) on the surfaces, indicating that the BPA molecules reached the already occupied active sites and returned after undergoing heat exchange (τ > 0). Adsorption is an endothermic spontaneous process that results in a balance between entropic and enthalpic contributions. In such a reaction, ΔG°< 0, even with ΔH°> 0, the process occurs with an important increase in the entropy. The desorption was more efficient with ethanol and methanol than with HCl, NaOH, and NaCl owing to the dipole-dipole forces between the adsorbate and the alcohols. Additionally, the low desorption efficiency using acid, base, and salts can be attributed to competitive effects between the desorption agents and the active sites of the adsorbents.

Rapid iodine capture from radioactive wastewater by green and low-cost biomass waste derived porous silicon–carbon composite

The effective and safe capture and storage of radioactive iodine (¹²⁹I or ¹³¹I) are of significant importance during nuclear waste storage and nuclear energy generation. Herein, a porous silicon–carbon (pSi–C) composite derived from paper mill sludge (PMS) is synthesized and used for rapid iodine capture. The influences of the activator type, the impregnation ratio of the paper mill sludge to the activator, carbonization temperature, and carbonization time on the properties of the pSi–C composite are investigated. The pSi–C composite produced in the presence of ZnCl₂ as the activator and at an impregnation ratio of 1 : 1, a carbonization temperature of 550 °C, and a carbonization time of 90 min has a surface area of 762.13 m² g⁻¹. The as-synthesized pSi–C composite exhibits promising iodine capture performance in terms of superior iodine adsorption capacity (q_t) of around 250 mg g⁻¹ and rapid equilibrium adsorption with in 15 min. The devised method is environmentally friendly and inexpensive and can easily be employed for the large-scale production of porous silicon-activated carbon composites with excellent iodine capture and storage from iodine-contaminated water.

The effective and safe capture and storage of radioactive iodine (¹²⁹I or ¹³¹I) are of significant importance during nuclear waste storage and nuclear energy generation.

Synthesis and Adsorption Performance of a Hierarchical Micro-Mesoporous Carbon for Toluene Removal under Ambient Conditions

Ordered mesoporous carbons (OMCs) were synthesized in this study through a soft template method and then activated by employing different mass ratios of KOH/OMCs to obtain KOH-activated ordered mesoporous carbons (KOMCs) with hierarchical pore structures. To verify the adsorption capacity, the KOMCs have been subjected to toluene emission-reduction experiments. The KOMCs were characterized by TEM, XRD, N2 adsorption-desorption isotherms, and Raman spectroscopy. The pore structure of OMCs was found to be effectively optimized by the activation with KOH, with the BET-area and total pore volume values reaching as high as 2661 m2 g-1 and 2.14 cm3 g-1 respectively. Then, the dynamic adsorption capacity of toluene on KOMCs was investigated via breakthrough curves, which can be well described by the Yoon and Nelson (Y-N) model. The dynamic adsorption capacities of toluene exhibit the following order: OMC < KOMC-1 < KOMC-5 < KOMC-3. The sample activated by KOH/OMC with a mass ratio of 3:1 (KOMC-3) demonstrated the highest toluene adsorption capacity of 355.67 mg g-1, three times higher in comparison with the untreated carbon (104.61 mg g-1). The modified hierarchical porous carbons also exhibited good recyclability. The KOMCs with rich pore structure, high toluene adsorption capacity, and superior reusability thus display a huge potential for volatile organic compound (VOC) elimination.

Ultra-high adsorption of tetracycline antibiotics on garlic skin-derived porous biomass carbon with high surface area

A porous carbon material with ultra-high specific surface area was prepared from waste garlic skin, and exhibited excellent adsorption properties to TCs in a water environment.

Magnetic Behavior of Carbon Materials Made from Biomass by Fe-Assisted Hydrothermal Carbonization

Biomass magnetic materials were synthesized by several hydrothermal carbonization methods, by which iron was provided in different ways: as FeCl₃ prior to or during hydrothermal carbonization, as pure Fe particles, or as magnetic ferrofluid, followed or not by pyrolysis processes. The materials were thoughtfully characterized in terms of elemental composition, thermal degradation, porosity (N₂ adsorption, SEM micrography), surface chemistry (FTIR spectroscopy, XRD diffraction), and magnetization curves on a self-made installation. The results indicated that the process design can significantly improve the structure and chemistry of the material, as well as the magnetization effect induced on the adsorbent. Fe as FeCl₃ was more interesting in regards to the development of porosity, mainly creating micropores, although it did not provide magnetism to the material unless a further pyrolysis was applied. Thermal treatment at 600 °C did not only increase the BET-specific surface (S_BET) (262 m² g⁻¹) of the hydrochar, but also involved the transformation of Fe into magnetite, providing magnetic behavior of the hydrochar. Increasing pyrolyisis temperature to 800 °C even enhanced a better development of porosity (S_BET of 424 m² g⁻¹) and also increased the specific magnetic susceptibility of the hydrochar as a result of the further transition of Fe into wustite and hydroxi-ferrite.

Thermal conversion of pineapple crown leaf waste to magnetized activated carbon for dye removal

Pineapple crown leaf was successfully converted to the magnetized activated carbon (MAC) as an attractive solution to overcome separation problems. The activated carbon (AC) was produced by an innovative method combining KOH activation and microwave heating while the magnetization process was prepared by a co-precipitation method. In this sense, the activation stage was studied at different impregnation ratio. The resulted magnetic adsorbent was further tested its feasibility for methyl violet dye removal. The result shows that MAC consists of both micropores and mesopores with more oxygen-containing functional groups, indicating it can be used to remove dye from contaminated water. The increase of impregnation ratio led to an increase in the MAC porosity and a decrease in the magnetic property. The adsorption behavior of methyl violet dye onto MAC was well described by the Redlich-Peterson isotherm model.