Activated Carbon Research Articles

Synthesis and characterisation of superior AC/ZnO NPs biocomposite for hexavalent chromium Cr(VI) adsorption

This study aims to synthesize biocomposite by combining banana stem activated carbon (AC) and ZnO Nanoparticles (NPs) to evaluate their adsorption potential towards hexavalent chromium (Cr (VI)) (20 mg/L). The AC used was successfully synthesized by an impregnation method using phosphoric acid (H3PO4) for 24 h, followed by a carbonization method. ZnO NPs were synthesized using the direct precipitation method using zinc acetate dihydrate (0.2 M) and KOH (0.4 M) as precursors. The AC/ZnO NPs biocomposite was fabricated using the mechanical alloying method at a frequency of 10 Hz for 30 min. The FTIR results show that both adsorbents, namely pure AC and AC/ZnO NPs have abundant functional groups. XRD results show the adsorbent is amorphous with pure AC at 89.95% and AC/ZnO NPs biocomosite at 56.49%. SEM results showed that the morphology of AC resembled crushed bovine bone marrow, and the morphology of ZnO NPs showed a marshmallow-like shape. The UV–vis spectrometer test results show that at the absorption peak of 350 nm the Cr (VI) removal efficiency slowly decreases and disappears at a dose variation of 1.5 g pure AC, 2 g biocomposite AC/ZnO NPs, and 2 g pure AC with Cr (VI) removal efficiency of 99.61%, 99.64%, and 99.83% respectively. Finally, we can report that the high degradation ability for Cr (VI) can be related to thesharp peak of –C=O group, reduced ΔLO−TO, and smaller average crystallite size in AC/ZnO NPs biocomposite.

Microwave catalytic co-pyrolysis of microalgae and high density polyethylene over activated carbon supported bimetallic: Characteristics and bio-oil analysis

Three activated carbon (AC) supported bimetallic catalysts (Ce-Fe/AC, Ce-Ni/AC, Ce-Cu/AC) were prepared, and the catalysts' impacts on the microwave co-pyrolysis of Chlorella vulgaris (C. vulgaris) and high density polyethylene (HDPE) (mixing ratio of 1:1, C1HP1) were explored. The findings indicated that the catalysts promoted the co-pyrolysis of C1HP1 substantially at 40 % and 50 % additions. The minimum reaction time (2945 s) was observed at 40 % Ce–Fe/AC. Compared to the C1HP1 group, Ce-Fe/AC groups exhibited a pronounced promotional impact on bio-oil production, with the maximum bio-oil yield (25.8 %) catalyzed by 30 % Ce–Fe/AC. Furthermore, the catalyst's high hydrogenation activity and deoxygenation promoted the formation of H2O, NH3 and HCN, achieving over 40 % efficiencies in deoxygenation and denitrification for bio-oil. 40 % Ce–Cu/AC exhibited superior performance with the highest hydrocarbon (67.43 %) and aromatic hydrocarbon content (50.75 %), as well as leading deoxygenation (44.38 %) and nitrogen removal (58.63 %) efficiency among the AC supported bimetallic catalysts.

β-Lactoglobulin Enhances Clay and Activated Carbon Binding and Protection Properties for Cadmium and Lead.

The removal of heavy metals from wastewater remains a challenge due to the limitations of current remediation methods. This study aims to develop multicomponent composites as inexpensive and environmentally friendly sorbents with enhanced capture of cadmium (Cd) and lead (Pb). The composites are based on calcium montmorillonite (CM) and activated carbon (AC) because of their proven effectiveness as sorbents for diverse toxins in environmental settings. In this study, we used a combination of computational and experimental methods to delineate that β-lactoglobulin enhances CM and AC binding and protection properties for Cd and Pb. Modeling and molecular dynamics simulations investigated the formation of material systems formed by CM and AC in complex with β-lactoglobulin and predicted their capacity to bind heavy metal ions at neutral pH conditions. Our simulations suggest that the enhanced binding properties of the material systems are attributed to the presence of several binding pockets formed by β-lactoglobulin for the two heavy metal ions. At neutral pH conditions, divalent Cd and Pb shared comparable binding propensities in all material systems, with the former being consistently higher than the latter. To validate the interactions depicted in simulations, two ecotoxicological models (L. minor and H. vulgaris) were exposed to Cd, Pb, and a mixture of the two. The inclusion of CM-lactoglobulin (β-lactoglobulin amended CM) and AC-lactoglobulin (β-lactoglobulin amended AC) at 0.05-0.2% efficiently and dose-dependently reduced the severe toxicity of metals and increased the growth parameters. This high efficacy of protection shown in the ecotoxicological models may result from the numerous possible interaction pockets of the β-lactoglobulin-amended materials depicted in simulations. The ecotoxicological models support the agreement with computations. This study serves as a proof of concept on how computations in tandem with experiments can be used in the design of multicomponent clay- and carbon-based sorbent amended systems with augmented functionalities for particular toxins.

Molecular-level insight into the effect of fertilization regimes on the chemodiversity of dissolved organic matter in tropical cropland

Fertilization is a critical agronomic measure for croplands in tropical regions, owing to their low fertility. However, the effects of fertilization on the quantity and chemodiversity of latosolic dissolved organic matter (DOM) in tropical regions remain largely unknown. Therefore, in this study, the variations in latosol DOM concentrations and chemodiversity induced by inorganic fertilization and the co-application of inorganic fertilization with straw return, sheep manure, biochar, and vermicompost fertilizers at a molecular level were systematically investigated using multispectral techniques and ultrahigh-resolution mass spectrometry. In line with our expectations, the results showed that combined inorganic-organic fertilization improved soil quality by increasing soil organic carbon content compared to that under inorganic fertilization. However, as the most active and bioavailable organic carbon pool, dissolved organic carbonconcentrations between the fertilization treatments were not significantly different (p = 0.07). However, the dissolved organic carbon concentrations under combined inorganic-organic fertilization treatment (NPK plus straw return, 263.45 ± 37.51 mg/kg) were lower than those under inorganic fertilization treatment (282.10 ± 18.57 mg/kg). Spectral analysis showed that the DOM in the combined inorganic-organic fertilization treatments had a higher degree of humification and lower autogenetic contributions. Furthermore, Fourier transform ion cyclotron resonance mass spectrometry analysis indicated that the combined inorganic-organic fertilization increased the chemodiversity of latosolic DOM and promoted the production of large, oxidized, and stable molecules, including lignin, aromatic, and tannin compounds, which potentially benefits soil carbon sequestration in tropical regions. This study could provide a theoretical basis for elucidating on the potentially relevant ecological functions and environmental effects of DOM under fertilization regimes.

Significant performance enhancement of Zn-ion hybrid supercapacitors based on microwave-assisted pyrolyzed active carbon via synergistic effect of NaHCO3 activation and CNT networks

Zinc-ion hybrid supercapacitors (ZIHSCs) represents a promising technological approach for large-scale energy storage with the combined advantages of supercapacitors and zinc-ion batteries. Unfortunately, it is still challengeable to quickly fabricate low-cost, high-performance carbonaceous cathode materials at relatively low temperature. To address such issues, herein, taking waste Eucommia ulmoides Oliver (EUO) wood as an example, we present a novel microwave-assisted carbonization (MWC) approach at relatively low temperature to quickly prepare active carbon, and we present a synergistic strategy to significantly enhance the electrochemical performance by introducing sodium bicarbonate activation (SA) and constructing conductive carbon nanotubes (CNT) networks. The MWC-SA@CNT hybrid exhibits outstanding specific capacitance of 344.2 F/g at 0.2 A/g within three-electrode system, much better than conventional high-temperature pyrolyzed AC, MWC carbon, and MWC-SA carbon. The superior performance of MWC-SA@CNT can be attributed to the synergistic effect of its large specific surface area of 1102.7 m2/g, high mesoporous percentage of 53.5%, and rich –OH and CO groups due to microwave-assisted carbonization and sodium bicarbonate activation, and rich electron transport paths due to the presence of CNT networks. Furthermore, ZIHSCs assembled by MWC-SA@CNT cathode could delivers impressive performance with excellent capacity (194.37 mA h/g at current density of 1 A/g), energy density (142.30 Wh/kg), and durability (capacitance retention rate of 97.65% after 5000 cycles). This work offers a rapid and low-temperature method for preparing wood-based active carbon with rich nanopores and strong conductivity to improve performance of Zinc ion storage.

Waste biomass-derived activated carbons for selective oxygen adsorption

Activated carbons (ACs) derived from waste rice husk ash (RHA) exhibit remarkable potential for selective oxygen adsorption. The pore morphology of the prepared materials was characterized utilizing BET measurement, t-plot, and BJH-plot suggesting a linear relation between activation temperature and mesopore volume, whereas, micropore volume decreases at activation beyond 550 °C. FT-IR spectroscopy confirms their non-polar surface. Notably, AC-600 achieves an outstanding O2/N2 (0.21/0.78) of 152.7 at 0.01 bar at 25 °C, owing to the non-polar nature of the surface, favouring oxygen adsorption due to its low quadrupole moment. Additionally, the mixed micro and mesoporous structure of AC-600 significantly enhance the oxygen adsorption, showing an ∼18.4% (or 1.2-fold) increase compared to AC-500. However, a ∼32.3% decrease in oxygen uptake was observed for AC-800 due to excessive “burn-off”. Adsorption selectivity, assessed with Ideal Adsorption Solution Theory (IAST) and fitted to the Freundlich isotherm model, and adsorption kinetics, analysed using the pseudo-second-order Lagergren and Webber-Morris intraparticle diffusion models, highlighted the impact of activation temperature on the porosity of the material. Understanding the surface chemistry and pore morphology of activated carbon offers deeper insights to enhance oxygen uptake capacity, advancing the development of sustainable, industrially viable materials for oxygen production.

Systematic screening and evaluation for an optimal adsorbent in a facade-integrated adsorption-based solar cooling system for high-rise buildings

Solar-powered adsorption chillers are a climate-friendly solution for building cooling, but costs and space requirements limit their widespread adoption. Recently developed adsorption cooling facade systems (ACFS) save installation space and further reduce CO2 emissions. The performance of ACFS depends on the implemented adsorbent. To achieve low costs and high performance of ACFS, this study systematically screened and scored adsorbents using the analytic hierarchy process (AHP) method, focusing on price, stability, driving temperature and adsorption capacity. This method narrowed down 293 adsorbents to top 10 scored adsorbents including 4 silica gels, 4 active carbons and 2 molecular sieves. The adsorbent-specific performance is evaluated by numerical simulation, revealing silica gel Type A++, Type 2560, Siogel and molecular sieve AQSOA-FAM-Z02 have peak adsorber temperatures 1.5–9.3 °C lower and increase solar cooling efficiency (SCE) by 25–27 % compared to reference adsorbent Zeolite 13X. A sensitivity analysis of the Dubinin-Astakhov equation shows increasing E and decreasing V leads to an only minor adsorber temperature decrease and minor system efficiency increase. Lower temperatures and higher capacity cannot guarantee better system performance. This underscores that improving system performance cannot be achieved solely through adsorbent optimization but requires system optimization in parallel.

Inclusion Strategy for Constructing S/N Orbital Hybridization-Regulated sp3/sp2 Carbon toward Boost Electrocatalysis.

Metal-free carbon-based electrocatalysts have gained significant attention in the field of zinc-air batteries (ZABs) due to their affordability, good conductivity and chemical stability. However, unmodified carbon materials typically fall short in adsorbing and activating the substrates and intermediates involved in oxygen reduction reactions (ORR). Here, a metal-free carbon-based electrocatalyst with S atom p orbital hybrid modified N-sp3/sp2 carbon structure (C/NS) were prepared by cyclodextrins inclusion. The catalyst demonstrates impressive ORR activity (E1/2=0.885 V vs. RHE) and robust ZABs performance with a power density of 171.3 mW cm-2 and a specific capacity of 781.2 mAh g-1. Density functional theory (DFT) calculation reveals that S atom effectively regulates the charge distribution and p-band center of active site carbon atom in the N-sp3/sp2 carbon structure. This modification prompts the adsorption and dissociation of O2 and intermediates, resulting in higher reactive activity. This work provides a valuable and practical strategy for preparing cost-effective metal-free carbon-based electrocatalysts for ORR with high performance.

Waste Bakelite Board Derived Activated Carbon for Supercapacitor Electrode

The low biodegradability of Bakelite waste raises concerns for the environment as it is typically dumped in landfills. Herein we present regenerated activated carbon (AC) prepared from waste Bakelite board. Preparation of the ACs involves carbonization and KOH activation. Afterwards, the as-made AC were doped with N urea and subsequently pyrolyzed at high temperature. The resulting AC, with and without N-doping have been evaluated in supercapacitor. We demonstrate an N-doped AC that exhibits a specific capacitance (Csp) as high as 203.0 F g−1 at 0.5 A g−1 and retains 93.1% of the Csp after 5000 galvanostatic charge discharge (GCD) cycles at 3 A g−1. We also show that a symmetric supercapacitor exhibits a maximum energy density of 10.3 Wh kg−1 at 250 W kg−1. In general, our work shows a cost-effective approach towards high-performance waste-regenerated ACs.

SO2 removal performance and breakthrough prediction of activated carbon-based chemical filters for electronics cleanroom air purification

Electronic cleanrooms have strict control requirements for SO2 concentration due its significant influence on product yield, and application of chemical filters is the main measure of SO2 control. In this study, 8 activated carbon (AC)-based chemical filters were collected and tested for their SO2 purification performance and resistance. These filters had very similar initial efficiencies (all >95 %) but large differences in 20 % breakthrough adsorption capacity (49–294 g at 9 ppm and 0.35 m/s). The adsorption capacity is found to be positively correlated with pleat density, which is a main structural parameter of pleated chemical filter. Meanwhile, the filter resistance (9.3–34 Pa at 0.35 m/s) demonstrates a decreasing and then increasing trend with increasing pleat density. This indicated the existence of an optimal range of pleat numbers that can be used to achieve a balance between resistance and adsorption capacity. A comprehensive performance evaluation index (Z′-index) is proposed for assessing the integrated resistant and adsorption capacity performance of chemical filters (19–210 g/W for 8 samples). A lumped parameter model was proposed for predicting the breakthrough curves at low concentration based on the traditional semi-empirical breakthrough models. The prediction deviation of the breakthrough curve at real cleanroom scenario (2 ppb) is less than 15 %. In addition, a rapid filter life prediction method based on filter design parameters is developed from the lumped parameter model. This work helps the understanding of the impact of filter structure parameters on performance and facilitate the development of high-performance chemical filters for SO2 contaminant control in electronic cleanrooms.

Effects of Pre-Fermentative Treatments with Non-Synthetic Ternary Component Fining Agents Based on Pea Protein on the Volatile Profiles of Aromatic Wines of Tămâioasă Românească

To remove oxidizable polyphenolic compounds from wines, fining treatments with products of various origins are applied before or after fermentation. Seeking alternatives to the treatments with animal proteins or synthetic materials such as polyvinylpolypyrrolidone (PVPP), vegetal and mineral products are tested. One of these alternative agents is pea protein (P), which can be combined with chitosan (K), yeast cell walls (Y), active carbon (C), and/or Ca-bentonite (B). Aside from the proven polyphenol removal effect, these products can also have an impact on aroma. This research evaluates the effect of P and ternary combinations with P on the volatile compounds of aromatic wines from the Tămâioasă românească variety. Several variants of treatments with P and with ternary mixtures involving P were prepared in triplicate with a total dose of 20 g/hL of fining agent applied during the pre-fermentative phase. Volatile profiles were determined using a flash gas chromatograph with two short columns of different polarities. The chromatographic peak areas for the identified ethylic esters, acetates and terpenes were used to compare the fining treatment effects. To test the significant differences between experimental variants, the Analysis of Similarity (ANOSIM) was used. The influences of P used alone and PVPP used alone were both significantly different compared to control (untreated), but based on the dissimilarity index R, PVPP affected the volatile profile about twice as much as P, showing that pea protein is a good alternative for PVPP. The ethyl esters were especially reduced by PVPP, while P especially reduced the terpenes. From all the tested pea protein ternary agents, those containing bentonite (PCB and PYB) showed a significant reducing effect on all classes of compounds and therefore are not recommended. The combinations containing yeast cell walls, PCY and PKY, are the most interesting alternatives to both PVPP and P used independently, PCY being the least aggressive of all treatments on overall aroma, preserving well the aroma compounds of all determined classes, including terpenes.

Oxalate-derived porous C-doped NiO with amorphous-crystalline heterophase for supercapacitors

Constructing amorphous/crystalline heterophase structure with high porosity is a promising strategy to effectively tailor the physicochemical properties of electrode materials and further improve the electrochemical performance of supercapacitors. Here, the porous C-doped NiO (C-NiO) with amorphous/crystalline heterophase grown on NF was prepared using NF as Ni source via a self-sacrificial template method. Calcining the self-sacrificial NiC2O4 template at a suitable temperature (400 °C) was beneficial to the formation of porous heterophase structure with abundant cavities and cracks, resulting in high electrical conductivity and rich ion/electron-transport channels. The density functional theory (DFT) calculations further verified that in-situ C-doping could modulate the electronic structure and enhance the OH− adsorption capability. The unique porous amorphous/crystalline heterophase structure greatly accelerated electrons/ions transfer and Faradaic reaction kinetic, which effectively improved the charge storage. The C-NiO calcined at 400 °C (C-NiO(400)) displayed a markedly enhanced specific charge, outstanding rate property and excellent cycling stability. Furthermore, the hybrid supercapacitor assembled by C-NiO(400) and active carbon achieved a high energy density of 49.0 Wh kg−1 at 800 W kg−1 and excellent cycle stability (90.9 % retention at 5 A/g after 10 000 cycles). This work provided a new strategy for designing amorphous/crystalline heterophase electrode materials in high-performance energy storage.

Catalytic conversion of biomass pyrolysis volatiles over composite catalysts of activated carbon and HY zeolite

Bio-oil has complex compositions and high oxygen content, which restricts its high-value utilization. Commercial activated carbon (AC) and HY zeolite were used as composite catalysts to study their effect on pyrolysis volatiles from rice straw and poplar sawdust by changing the mixing modes of two catalysts. The results showed that the loading modes of AC and HY zeolite obviously affected the products distribution and bio-oil components. The lowest yield of bio-oil was obtained when HY zeolite and AC were mechanically mixed at a mass ratio of 1:1 (YACM). But the loading mode of YACM was beneficial to the deoxidation and aromatic hydrocarbon generation. Under the mode of YACM, the aromatics content in rice straw and poplar sawdust bio-oil can be increased from 13.8% and 8.0% without catalyst to 56.4% and 53.1%, respectively. However, the layered loading with upper HY zeolite and lower AC (YTACL) was favorable for formation of phenolic compounds. The selectivity to monocyclic and bicyclic aromatic hydrocarbons followed the order of YTACL > ACTYL > YACM, and YACM > ACTYL > YTACL, respectively. Compared with HY zeolite, AC catalyst possessed smaller pore size and fewer acidity, and the active sites of AC were conducive to rearrangement of furan compounds to generate cyclopentanone, 2-cyclopentenone and methyl-cyclopentenone, and further rearrangement to form phenol. Therefore, the loading mode of YTACL exhibited a promotion effect on the formation of phenol, cresol, toluene, ethylbenzene and p-xylene. The strong acidic sites of HY zeolite were favorable for the aromatization, so the loading mode of ACTYL had good selectivity to the formation of naphthalene, methylnaphthalene, anthracene and pyrene. This work will provide a guide for products regulation from biomass pyrolysis and enrich aromatics and phenols in bio-oil.

Adsorption of cadmium from wastewater with activated carbons derived from pig fur biowaste: A comparative study of in-situ and ex-situ activation routes

The environmental challenges associated with cadmium contamination in wastewater have necessitated the development of high-performing activated carbons (ACs) for effective wastewater treatment. Adsorption capacity depends on both the surface area and the adsorption-active functional groups developed on the adsorbent's surface during activation. Proper manipulation of key process variables using the appropriate activation route produces highly efficient and economically viable ACs. This research investigates the viability of pig fur biowaste as a novel precursor for activated carbons using two distinct activation methods—in-situ and ex-situ. Using a central composite design (CCD) of the Response Surface Methodology (RSM), the study systematically examines the effects of impregnation ratio, carbonization temperature, and carbonization time on the cadmium adsorption capacities of the resulting ACs. The optimal conditions for in-situ activation were found to be 691 °C, 175.11 min, and an impregnation ratio of 1.784 g/g, resulting in a cadmium adsorption capacity of 91.57 %. For ex-situ activation, the optimal conditions were 468.8 °C, 80.81 min, and an impregnation ratio of 2.915 g/g, which achieved a higher cadmium adsorption capacity of 91.21 %. Both types of activated carbons maintained high efficiency after five regeneration cycles, indicating they are suitable for long-term applications requiring repeated regeneration. Although both methods produced ACs with comparable cadmium removal efficiency, the ex-situ activation route proved to be more economically viable due to its lower temperature and shorter processing time. This study demonstrates the potential of pig fur biowaste as a sustainable and underutilized resource for AC production and highlights the ex-situ activation route as the more cost-effective approach for producing high-performance adsorbents.

Chemically Stable NiMoO4/NRGO Asymmetric Capacitor

AbstractIn this work, a chemically stable NiMoO4/NRGO nanocomposite was prepared via a facile hydrothermal method. The flower‐like structure of NiMoO4 (NMO) nanoparticles is randomly distributed on the surface of nitrogen‐doped reduced graphene oxide (NRGO) sheets, as observed in FESEM images. Compared to related reports, the NMO/NRGO (II) nanocomposite exhibits an excellent high surface area of 368.9 m2 g−1 and a mesoporous nature, as shown in N₂ adsorption‐desorption isotherms. The specific capacitance of the NMO/NRGO (II) electrode is 721 F g−1 at 1 A g−1 using a 6 M KOH electrolyte, retaining 91.2 % of its initial value after 5000 cycles. Electrochemical impedance spectroscopy (EIS) reveals that the electrode has a lower charge‐transfer resistance, indicative of good electrochemical behavior. An asymmetric device consisting of NMO/NRGO (II) || activated carbon (AC) electrodes exhibits a high energy density of 49.1 Wh kg−1 at 524.4 W kg−1 within a voltage range of 1.4 V, retaining 89 % of its initial capacitance after 5000 cycles, demonstrating good cyclic durability. These results suggest that the NMO/NRGO (II) electrode is a promising active material for supercapacitor devices.

Enhanced nitrogen removal and greenhouse gas reduction via activated carbon coupled iron-based constructed wetlands

Constructed wetlands (CWs) have been widely used to remove nitrogen in the effluent from sewage plants. Still, the removal capacity of nitrate (NO3−-N) in CWs is unsatisfactory due to the insufficient electron donor. This study explored the role of activated carbon (AC) in nitrogen removal and greenhouse gas (GHG) emissions reduction in different iron-based CWs. Long-term experimental results showed that pyrite and sponge iron-based CWs had higher NO3−-N removal rates (98.18 % and 94.10 %). Compared with the control group, AC promoted their total nitrogen (TN) removal efficiency (78.87–87.59 %) and reduced GHG emissions (CO2: 3.79–4.11 %, N2O: 2.97–8.78 %, CH4: 9.93–10.73 %). Moreover, AC not only promoted the values of electron transfer system activity (ETSA), the activity of nitrate reductase and nitrite reductase, but also significantly increased the microbial diversity and abundance of the substrate layer in pyrite/SI- based CWs. The relative abundance of the dominant bacteria in CWs with pyrite coupling with AC (PC-CW) was the highest (nirS: 77.60 %, nosZ: 88.98 %) compared with the other CWs. The higher relative abundance of Dechloromonas and Thiobacillus in PC-CW indicated that the composite substrates of pyrite and AC promoted the extracellular electron transfer of denitrifying microorganisms. This study provides new insights into optimizing inorganic electron donors to improve the removal of NO3−-N and the reduce of GHG emissions in CWs for low C/N wastewater treatment.

Bioorganic activated carbon from cashew nut shells for H2 adsorption and H2/CO2, H2/CH4, CO2/CH4, H2/CO2/CH4 selectivity in industrial applications

This research explores the production of activated carbon (AC) from cashew nut shells using a potassium hydroxide (KOH) activation method, with a focus on its application in high-pressure gas adsorption. Among the synthesized samples, AC850 demonstrated the highest efficiency, displaying a specific surface area of 1972 m2/g and total and micropore volumes of 0.847 cm3/g and 0.724 cm3/g, respectively. The bioorganic activated carbon exhibited significant sorption capabilities for H2, with uptake values of 13.34 mmol/g (2.69 wt%) at 10 bar and 25 °C, and a H2/CH4 selectivity range between 43.4 and 2.6. Calculations were also conducted for selectivity in a mixture of three gases (H2, CO2, and CH4) in industrial settings. Advanced characterization methods such as N2/CO2 adsorption isotherms, FT-IR, Raman spectroscopy, SEM, and TGA were employed to analyze the structural and chemical properties of the produced AC, including its functional groups and molecular structure. The research underscores the potential of utilizing agricultural waste, particularly cashew nut shells, to develop efficient materials for H2 storage and purification. The high-pressure adsorption capability and eco-friendly nature of the manufactured activated carbon make it suitable for both environmental and industrial applications.

Removal of metals and assimilable organic carbon by activated carbon and reverse osmosis point-of-use water filtration systems

Activated carbon (AC) systems and reverse osmosis (RO) systems are commonly used point-of-use (POU) water filtration systems for removing trace-level contaminants in tap water to protect human health. However, limited research has been done to evaluate their effectiveness in removing heavy metals like manganese (Mn) and uranium (U), or to assess the potential for undesired microbial growth within POU systems, which can reduce their treatment efficiency. This study aimed to systematically evaluate the removal of metals and assimilable organic carbon (AOC) in POU systems. AC systems were operated to 200% of their designed treatment capacities and RO systems were run for three weeks. The results showed that AC systems were generally ineffective at removing metals from drinking water, while RO systems effectively removed them. Both Mn and U were poorly removed by AC systems. Calcium (Ca) and magnesium (Mg) were poorly removed by AC systems, with efficiencies of less than 1%. Iron (Fe) removal by AC systems varied between 61% and 84%. Copper (Fe), likely due to its low influent concentration (<30 μg L−1), was effectively removed by AC systems with efficiencies over 95%. In contrast, RO systems consistently removed all metals effectively. Mn and U removal in RO systems exceeded 95%, while Ca, Mn, Fe, and Cu were all removed with efficiencies greater than 98%. AOC was effectively removed from all AC and RO systems, but with high variability in removal efficiency, which is likely attributed to the heterogeneity of biofilm and microbial growth within the POU systems. The new knowledge generated from this study can improve our understanding of chemical contaminant removal in POU systems and inform the development of better strategies for designing and operating POU systems to remove chemical contaminants in drinking water and mitigate their associated health risks.

Removal of sulphur and nitrogen compounds from model fuel by adsorption of modified activated carbon

This study aimed to achieve the highest percentage removal of dibenzothiophene (DBT), quinoline (QUI), and indole (IND) adsorbed by double-impregnated modified activated carbon (MAC). Modification of commercial activated carbon (AC) by sulphuric acid (H2SO4) of 15%, 30%, 45%, 60%, and 75% w/v followed by subsequent 1 zinc chloride (ZnCl2): 1 AC impregnation ratio and activated at 500 oC in a muffle furnace under self-generated atmosphere for an hour. The determination of optimized MAC was identified through the highest removal rate of DBT, QUI, and IND from adsorption experiments which were analysed using an ultraviolet-visible (UV-Vis) spectrophotometer. It was found that DBT and IND showed a removal high percentage of up to 86.23% and 82.77% respectively by using 75% H2SO4 with ZnCl2 MAC. Meanwhile, QUI favoured 30% H2SO4 with ZnCl2 MAC with a removal percentage of 33.17% which was still higher than unmodified AC. Physical and chemical properties such as the morphological structure, elemental analysis, porosity, pore size, surface functional group, percentage yield, pH, bulk density, content, ash content, and iodine number were studied for the optimized MAC. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to characterize the MAC. Both MACs showed high percentage yields of 72.08% and 71.13% for 30% and 75% H2SO4 and ZnCl2 MAC respectively. Meanwhile, the pH was between the ranges of 5.36-5.53 for both MACs. Bulk densities were also favourable while the moisture and ash content were within acceptable limits. Iodine numbers for 30% and 75% H2SO4 and ZnCl2 MAC were 857 and 861 mg/g respectively, hence indicating that the MAC achieved high porosity and good adsorption performance. Langmuir, Freundlich, and Temkin adsorption isotherm models as well as pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models were considered for understanding the adsorption mechanisms. The study revealed that DBT, QUI, and IND removal processes, followed the Langmuir adsorption isotherm model with correlation coefficients, R2 of 0.9905, 0.9791, and 0.9964 respectively. Moreover, the adsorption kinetic data of DBT, QUI, and IND provided a better fitting to the PSO kinetic model with R2 of 0.9992, 0.9987, and 0.9998 respectively. According to the Langmuir isotherm model and PSO kinetic model, the adsorption mechanisms of DBT QUI and IND were chemisorbed under monolayer formations.

In-situ synthesis of synergistic ZnMn2O4/MnOOH nanocomposite as a cutting-edge pseudocapacitive electrode material for all-solid-state asymmetric supercapacitors

Currently, there has been a growing interest in constructing metal oxide composite structures through the in-situ synthesis method, especially for fabricating electrode materials for supercapacitors. This approach offers several advantages, such as improved contact between different materials, enhanced conductivity, efficient ion diffusion, and better overall electrochemical performance. This work investigates the synthesis of zinc manganese oxide and manganese oxyhydroxide (ZnMn2O4/MnOOH) composite using a solvothermal method. The structure, surface morphology, and composition of the ZnMn2O4/MnOOH composite were elucidated using standard physicochemical characterization techniques where the presence of ZnMn2O4 and MnOOH phases was confirmed and the ZnMn2O4/MnOOH nanocomposite behaved as a pseudocapacitive electrode with a notable specific capacitance of 1039.2 F g⁻1 at a current density of 1 A g⁻1. When subjected to a 10-fold increase in current density, the ZnMn2O4/MnOOH electrode maintained 50 % of its initial capacity, registering 513.4 F g⁻1. Additionally, the electrode showcased excellent cyclic stability, preserving 95 % of its initial capacity after 5000 cycles at 10 A g⁻1. Moreover, the constructed ZnMn2O4/MnOOH//activated carbon (AC) asymmetric supercapacitor (ASC) device attained a high energy density of 29.45 Wh kg⁻1 at a power density of 1384.5 W kg⁻1. The results confirm that the ZnMn2O4/MnOOH composite, prepared in a single synthesis step, shows great potential as a phenomenal pseudocapacitive electrode for energy storage applications.