The Analysis of Pore Development and Formation of Surface Functional Groups in Bamboo-Based Activated Carbon during CO2 Activation

Cellulose-Amine Porous Materials: The Effect of Activation Method on Structure, Textural Properties, CO2 Capture, and Recyclability

CO2 capture via physical adsorption on activated porous carbons represents a promising solution towards effective carbon emission mitigation. Additionally, production costs can be further decreased by utilising biomass as the main precursor and applying energy-efficient activation. In this work, we developed novel cellulose-based activated carbons modified with amines (diethylenetriamine (DETA), 1,2-bis(3-aminopropylamino)ethane (BAPE), and melamine (MELA)) with different numbers of nitrogen atoms as in situ N-doping precursors. We investigated the effect of hydrothermal and thermal activation on the development of their physicochemical properties, which significantly influence the resulting CO2 adsorption capacity. This process entailed an initial hydrothermal activation of biomass precursor and amines at 240 °C, resulting in C+DETA, C+BAPE and C+MELA materials. Thermal samples (C+DETA (P), C+BAPE (P), and C+MELA (P)) were synthesised from hydrothermal materials by subsequent KOH chemical activation and pyrolysis in an inert argon atmosphere. Their chemical and structural properties were characterised using elemental analysis (CHN), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The calculated specific surface areas (SBET) for thermal products showed higher values (998 m2 g-1 for C+DETA (P), 1076 m2 g-1 for C+BAPE (P), and 1348 m2 g-1 for C+MELA (P)) compared to the hydrothermal products (769 m2 g-1 for C+DETA, 833 m2 g-1 for C+BAPE, and 1079 m2 g-1 for C+MELA). Carbon dioxide adsorption as measured by volumetric and gravimetric methods at 0 and 25 °C, respectively, showed the opposite trend, which can be attributed to the reduced content of primary adsorption sites in the form of amine groups in thermal products. N2 and CO2 adsorption measurements were carried out on hydrothermal (C) and pyrolysed cellulose (C (P)), which showed a several-fold reduction in adsorption properties compared to amine-modified materials. The recyclability of C+MELA, which showed the highest CO2 adsorption capacity (7.34 mmol g-1), was studied using argon purging and thermal regeneration over five adsorption/desorption cycles.

Unraveling the multifaceted mechanisms and untapped potential of activated carbon in remediation of emerging pollutants: A comprehensive review and critical appraisal of advanced techniques

The rapid global expansion of industrialization has resulted in the discharge of a diverse range of hazardous contaminants into the ecosystem, leading to extensive environmental contamination and posing a pressing ecological concern. In this context, activated carbon (AC) has emerged as a highly promising adsorbent, offering significant advantages over conventional forms. For instance, AC has demonstrated remarkable adsorption capabilities, as evidenced by the successful removal of atrazine and ibuprofen using KOH and KOH-CO2-activated char, achieving impressive adsorption rates of 90% and 95%, respectively, at an initial dosage of 10 mg L-1. Moreover, AC can effectively adsorb aromatic compounds through π-π stacking interactions. The aromatic rings in organic molecules can align and interact with the carbon atoms in AC's structure, leading to effective adsorption. In this review, by employing a systematic analysis of recent research findings (majorly from 2015 to 2023), an in-depth exploration of AC's evolution and its wide-ranging applications in adsorbing and remediating emerging pollutants, including dyes, organic contaminants, and hazardous gases and mitigating the adverse impacts of such emerging pollutants on ecosystems have been discussed. It serves as a valuable resource for researchers, professionals, and policymakers involved in environmental remediation and pollution control, facilitating the development of sustainable and effective strategies for mitigating the global impact of emerging pollutants.

Obtaining bio-oil and activated carbon from waste pomegranate peels by pyrolysis

This study aims to produce beneficial products with pomegranate peel waste through pyrolysis. For this purpose, the usability of the liquid product as a biofuel and the solid product as an adsorbent for dye removal was investigated. To characterize the bio-oil and biochar produced under the best pyrolysis conditions, Fourier transforms infrared spectroscopy (FT-IR), Gas chromatography-mass spectrometry (GC-MS), calorific value, Brunauer-Emmett-Teller (BET), and Scanning electron microscopy (SEM) analyses were conducted. When we examine the FT-IR spectrum of the bio-oil, the presence of phenol, alcohol, ketone, and aldehyde groups is seen in the structure. The GC-MS analysis demonstrated that phenol content was 27.9%, aldehyde content was 19%, acid compound content was 18.28%, ketone content was 8.7%, and aromatic compound content was 8.4%. The lower calorific value of bio-oil was determined as 27.33 MJ/kg. It was observed that activated carbon produced from biochar at a 3:1 KOH/biochar impregnation ratio and a carbonization temperature of 800 °C exhibited the highest surface area (1307 m2/g). In adsorption analysis, it was observed that the adsorption efficiency was higher at pH 9 and 35 °C and with 150 ppm initial concentration. Langmuir and Freundlich adsorption isotherms were determined, and the high R2 (0.99) was consistent with the Langmuir methylene blue (MB) adsorption model.

Bamboo-derived adsorbents for environmental remediation: A review of recent progress

The bamboo family of plants is one of the fastest-growing species in the world. As such, there is an abundance of bamboo residues available for exploitation, especially in southeast Asian, central African and south American regions. The preparation of efficient adsorbents from bamboo residues is an emerging exploitation pathway. Biochars, activated carbons or raw bamboo fibers embedded with nanoparticles, each class of materials has been shown to be highly efficient in adsorption processes. This review aims to summarize recent findings in the application of bamboo-based adsorbents in the removal of organic, inorganic, or gaseous pollutants. Therefore, this review first discusses the preparation methods and surface modification methodologies and their effects on the adsorbent elemental content and other basic properties. The following sections assess the recent progress in the adsorption of heavy metals, organics, and gaseous substances by bamboo-based adsorbents, focusing on the optimum adsorption capacities, adsorption mechanisms and the optimum-fitting kinetic models and isotherms. Finally, research gaps were identified and directions for future research are proposed.

Influence of Different Activators on the Structure and Properties of Activated Carbon Based on Bamboo Fiber

In order to explore the influence of different activators on the structure and properties of the prepared activated carbon, bamboo fiber-based activated carbons (BFACs) were prepared by four activators of phosphoric acid, pyrophosphoric acid, zinc chloride, and diammonium biphosphate (BFAC-H₃PO₄, BFAC-H₄P₂O₇, BFAC-ZnCl₂, and BFAC-(NH₄)₂HPO₄) and BFACs adsorption performance and electrochemical properties were investigated. The main conclusions were: the specific surface area of the four BFACs varies greatly, among which BFAC-ZnCl₂ was the highest, at 1908.5074 m²/g, and BFAC-(NH₄)₂HPO₄ was the lowest, at 641.5941 m²/g. In terms of the pore structure, BFAC-H₃PO₄ and BFAC-H₄P₂O₇ are mainly mesopores and BFAC-ZnCl₂ and BFAC-(NH₄)₂HPO₄ are mainly micropores. The BFAC-ZnCl₂ sample had the largest specific capacitance, with a specific capacitance of 121.2730 F/g at a current density of 0.2 A/g, with a small internal resistance and good electrochemical reversibility and capacitance performance. The adsorption properties were better for BFAC-ZnCl₂ and BFAC-H₃PO₄ and the adsorption amounts were 648.75 and 548.75 mg/g, respectively.

The Application of the Activated Carbon from Cordia africana Leaves for Adsorption of Chromium (III) from an Aqueous Solution

The objective of this study is to investigate the adsorption performance of activated carbon derived from the leaves of Cordia africana for the removal of Cr (III) from an aqueous solution. The plant sample was collected, washed, dried, grounded, and sieved at 125 μm mesh size. Adsorbent activation was done using H3PO4 at concentrations of 25–85% and pyrolysis temperature of 400–500°C. The activated carbon was characterized by proximate, SEM, BET, and FTIR analyses. A batch adsorption study was conducted to determine the effect of contact time, adsorbent dose, initial chromium concentration, and mixing speed on Cr (III) removal. The regeneration of the activated carbon was investigated by using 1 M of HNO3 as a desorbing solution for seven cycles. At optimum acid concentration and pyrolysis temperature, a surface area of 700 m2/g was recorded. The moisture content, volatile matter, ash composition, fixed carbon, and bulk density of the activated carbon were found to be 5.3%, 24.2%, 6.2%, 64.3%, and 0.75 g/mL, respectively. The SEM and FTIR analyses indicated that the surface morphology was full of cracks and different peaks were associated with plenty of functional groups, respectively. The maximum Cr (III) removal was attained at a contact time of 180 min (89%), adsorbent dose of 1.5 g (54%), initial concentration of 0.6 g/L (47%), and mixing speed of 300 rpm (64%). The equilibrium data were better described by Freundlich isotherm at R2 value of 0.88, which implies that the adsorption process is conducted on a heterogeneous surface. The pseudo-first-order kinetics model with R2 value of 0.99 best fits with the equilibrium data, which implies that physisorption controls the adsorption kinetics. Generally, it can be concluded that this locally prepared adsorbent is promising for the removal of chromium from industrial wastewater, but further factorial approach assessment has to be checked.

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.

Noble-metal-free single-phase Co3V2O8 with the structural integrity of nanofibers for the selective detection of ascorbic acid

Single-phase Co3V2O8 with the structural integrity of nanofiber exhibits high electrocatalytic activity for the oxidation of ascorbic acid (AA).

The Use of High Surface Area Mesoporous-Activated Carbon from Longan Seed Biomass for Increasing Capacity and Kinetics of Methylene Blue Adsorption from Aqueous Solution

Microporous- and mesoporous-activated carbons were produced from longan seed biomass through physical activation with CO2 under the same activation conditions of time and temperature. The specially prepared mesoporous carbon showed the maximum porous properties with the specific surface area of 1773 m2/g and mesopore volume of 0.474 cm3/g which accounts for 44.1% of the total pore volume. These activated carbons were utilized as porous adsorbents for the removal of methylene blue (MB) from an aqueous solution and their effectiveness was evaluated for both the adsorption kinetics and capacity. The adsorption kinetic data of MB were analyzed by the pseudo-first-order model, the pseudo-second-order model, and the pore-diffusion model equations. It was found that the adsorption kinetic behavior for all carbons tested was best described by the pseudo-second-order model. The effective pore diffusivity (De) derived from the pore-diffusion model had the values of 4.657 × 10-7-6.014 × 10-7 cm2/s and 4.668 × 10-7-19.920 × 10-7 cm2/s for the microporous- and mesoporous-activated carbons, respectively. Three well-known adsorption models, namely the Langmuir, Freundlich and Redlich-Peterson equations were tested with the experimental MB adsorption isotherms, and the results showed that the Redlich-Peterson model provided the overall best fitting of the isotherm data. In addition, the maximum capacity for MB adsorption of 1000 mg/g was achieved with the mesoporous carbon having the largest surface area and pore volume. The initial pH of MB solution had virtually no effect on the adsorption capacity and removal efficiency of the methylene blue dye. Increasing temperature over the range from 35 to 55 °C increased the adsorption of methylene blue, presumably caused by the increase in the diffusion rate of methylene blue to the adsorption sites that could promote the interaction frequency between the adsorbent surface and the adsorbate molecules. Overall, the high surface area mesoporous carbon was superior to the microporous carbon in view of the adsorption kinetics and capacity, when both carbons were used for the removal of MB from an aqueous solution.