Phosphoric Acid Activation Research Articles

Activated carbon from Camellia oleifera shells for adsorption of Y(iii): experimental and DFT studies.

Yttrium is an important rare earth element and is widely used in fields such as special glass preparation, metallurgy, and materials science. However, it is difficult to recover yttrium ion waste from dilute solutions with traditional processes, resulting in a significant waste of rare earth resources. The simple, effective, and easy-to-operate adsorption method is the most promising method for recovering yttrium, which is of great significance for sustainable development of the rare earth industry. In this study, activated carbon was prepared from Camellia oleifera fruit shells (COS) using phosphoric acid activation, and efficient recovery of Y(iii) from the Camellia oleifera fruit shell activated carbon was studied. Adsorption equilibrium data showed that this activated carbon had a Y(iii) adsorption capacity of 35.41 mg g-1, indicating significant potential for recovery of yttrium ions. The adsorption of Y(iii) by the activated carbon prepared from COS was consistent with the Langmuir model, and the adsorption data were consistent with the pseudo second-order kinetic model, indicating that the adsorption process was primarily chemical adsorption. After adsorption, the surface of the activated carbon contained large amounts of N, O, and Y, indicating that Y(iii) was stably adsorbed. The mechanisms for adsorption of Y(iii) on three types of activated carbon were studied through DFT calculations. The results showed that Y(iii) interacted with the carbon atoms on the surfaces to form new chemical bonds. The yttrium ion adsorption capacities for the three different activated carbons decreased in the order C I > C II > C.

Efficient dye adsorption of mesoporous activated carbon from bamboo parenchyma cells by phosphoric acid activation.

In order to solve the environmental damage caused by the discharge of dyes as industrial wastewater, the development of efficient and sustainable adsorbents is the key, while most of the previous studies on bamboo parenchyma cells have focused on their microstructural, functional and mechanical properties, and few of the properties in adsorption have been investigated. To evaluate the role of the unique microstructure of bamboo parenchyma cells on adsorption after carbonization and activation, PC-based activated carbon (PPAC) was fabricated by the phosphoric acid activation method and tested for adsorption using methylene blue (MB). The effect of mesoporous structure on MB adsorption was investigated in detail using PPAC-30C impregnated with phosphoric acid at a concentration of 30%. The results showed that the adsorption performance was influenced by single-factor experiments (e.g., pH, activated carbon dosing). The adsorption isotherms and kinetics could conform to the Langmuir model (R2 = 0.983-0.994) and pseudo-second-order kinetic model (R2 = 0.822-0.991) respectively, and the maximum MB adsorption capacity of adsorbent was 576 mg g-1. The adsorption mechanism of MB on PPAC-30C includes physical adsorption, electrostatic attraction, hydrogen bonding, and the π-π conjugation effect, which was dominated by physical adsorption. The results of this study show that PPAC has good application prospects for cationic dye removal.

High efficiency removal of ibuprofen in water using activated carbon derived from Radix Angelica Dahurica residue

AbstractThe exploitation and utilization of Traditional Chinese medicine have annually produced 30 million tons of waste residues including Radix Angelica Dahurica residue (RAR), which raised environmental concerns. Meantime, the non‐steroidal anti‐inflammatory drug of ibuprofen (IBP) is an emerging contaminant in the aquatic environment, annually producing up to 9000 tons in China. After extracting the active substance, RAR is prepared as activated carbon (AC) for the purification of IBP wastewater. Two kinds AC modified without (RAR‐AC) and with phosphoric acid (M‐RAR‐AC) were characterized by FT‐IR, TG, BET and SEM. The phosphoric acid activation contributed to the high BET surface area (564.9914 m2 g−1) and large total pore volume (0.4894 cm3 g−1). M‐RAR‐AC showed 7.7 folds (15 min) and 2.7 folds (30 min) higher extent of IBP removal compared to commercial activated carbon (C‐AC). The enhancement of IBP removal with M‐RAR‐AC was investigated further by varying initial pollutant concentration, absorbent dosage, temperature, pH and rotating speed. Especially, temperature nearly has no effect on IBP removal by M‐RAR‐AC. Isotherm and kinetic studies suggested IBP was adsorbed on the heterogeneous surface in multilayer form and chemisorption played the dominant role in IBP removal. IBP removal of 93.3 ± 0.1% and 64.2 ± 2.8% was achieved for first and fifth cycle, respectively. The IBP removal on M‐RAR‐AC may be accomplished by a variety of interactions such as electrostatic attraction, pore‐filling, hydrogen bonding, and π‐π interaction. These findings provide new insights into the utilization of RAR for preparing AC and highlight the potential applications for treating industrial wastewater.

Elimination of malachite green from aqueous and saline water by laterite-derived Na-polyferrosialate and polyferrophosphosialate geopolymers: A comparative study

In this study, two laterites (LA)-based geopolymers were synthesized using alkalination (GPAL) and phosphoric acid-activation (GPAC) approaches and applied to scavenge malachite green (MG) dye from aqueous (non-saline) and saline water. The precursor (LA) and geopolymers were characterized by XRF, XRD, TG/DTA SEM, and FTIR techniques. Alkalination and acid-activation resulted in morphologically distinguishable geopolymers with different porosity structures. The dissolution of mineral phases and chemical composition was dependent on the activation medium, resulting in Na-polyferrosialate and polyferrophosphosialate geopolymers for GPAL and GPAC, respectively. The adsorption kinetics data were best described by the pseudo-first-order (PFO) model wherein the adsorption rate, denoted by rate constant (k1), increased with an increase in ionic strength (salinity). The equilibrium data were best modelled by the Sips isotherm. GPAL had a higher maximum adsorption capacity (Qms) than GPAC in both aqueous (non-saline) and saline water. The adsorption capacities were increased in saline solution relative to aqueous solutions without NaCl, from 12.4 to 54.1 mg/g and from 57.1 to 92.0 mg/g for GPAC and GPAL, respectively. The adsorption mechanism entailed electrostatic interactions, hydrogen bonding and hydrophobic interactions. Salinity decreased the solubility of MG and increased the hydrophobic interactions and affinity of MG, implied by apparent equilibrium constant (Ka), resulting in increased adsorption density (Qms). These results indicate that alkaline-based geopolymers are better candidates for scavenging MG dye from water, especially in saline environments.

Toward pulping process for enhancing the RS-black liquors as precursor of activated carbons for aqueous adsorbent purposes

This work deals with providing a green pulping process of rice straw with zero waste discharged, via valorization of its by-product as a promising precursor for production of carbon nanostructures. The carbon nanostructures (BL-CNSs) from rice straw pulping liquors (BLs) are prepared in one step with phosphoric acid activation. The carbon nanostructures (BL-CNSs) from rice straw pulping liquors (BLs) are prepared in one step with phosphoric acid activation. The optimal pulping approach for achieving effective adsorbent (BL-CNSs) of cationic and anionic dyes is recommended from using different BLs precursors resulting from different reagents (alkaline, neutral, and acidic reagents). The carbon precursors are characterized by elemental, thermal (TGA and DTG) and ATR FTIR analyses. While the impact of pulping route on performance of CNSs is evaluated by their adsorption of iodine, cationic dye and anionic dye, as well as ATR-FTIR, textural characterization, and SEM. The data of elemental analysis displayed a high Carbon content ranges from 57.85 to 66.69% suitable for CNSs preparation, while the TGA showed that Sulphur-containing BLs (Kraft, neutral sulfite and acidic sulfite) have higher degradation temperature and activation energies as compared with other BLs. The optimum BL-CNSs adsorbent is prepared from the disposed neutral sulfite black liquor, with the following characteristics: cationic dye adsorption capacity 163.9 mg/g, iodine value 336.9 mg/g and SBET 310.6 m2/g. While the Kraft-CNSs provided highest anionic adsorption (70.52 mg/g). The studies of equilibrium and kinetic adsorption of dyes showed that the adsorption equilibrium of all investigated BL-CNSs toward MB follow the Langmuir and mainly Freundlich models for BB adoption. Their adsorption kinetics are a good fit with the pseudo-second-order model. The textural characterization and SEM revealed the CNSs exhibit a mixture of mesoporous and microporous structure.

Phosphoric acid activation of cow dung biochar for adsorbing enrofloxacin in water: Icing on the cake

In this study, we used different concentrations of H3PO4 to activate pristine biochar (BC) derived from cow dung (BC and BC modified with phosphoric acid at concentrations of 10% (10P-BC), 30% (30P-BC), and 50% (50P-BC)) in order to obtain cheap, high-performance adsorbents. Brunauer–Emmett–Teller analysis, scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, organic element composition determination, and other analyses showed that activation with H3PO4 increased the porosity and hydrophilicity compared with the original BC, thereby enhancing the adsorption properties. The Langmuir isotherm model obtained the best fit and the maximum capacities for adsorbing enrofloxacin by BCs were 12.66 mg/g for BC, 51.90 mg/g for 10P-BC, 63.61 mg/g for 30P-BC, and 26.79 mg/g for 50P-BC. The main mechanisms responsible for antibiotic loading on BC were hydrogen bonding, π–π electron donor–acceptor interactions, pore filling, and electrostatic interactions. Calculations of fixed carbon retention before and after pyrolysis, and adsorption showed that activated BC had a good carbon fixation capacity and it was more capable of adsorbing enrofloxacin compared with the original BC, thereby providing a new method for removing organic pollutants from the environment and reducing carbon emissions. The cost efficiency was analyzed using the improved fuzzy comprehensive evaluation model based on the entropy method. Removal efficiency and utilization efficiency indicators were calculated for the different phosphoric acid activated BCs. The pollutant removal efficiencies were better for 10P-BC and 30P-BC, and the optimal removal efficiency was determined for 30P-BC. Given the current global climate change situation, using 10P-BC and 30P-BC could also help to meet China's carbon neutrality goals by reducing emissions of pollutants containing carbon.

Investigation of the usability of activated carbon as a filling material in nitrile butadiene rubber/natural rubber components and modeling by regression analysis

Activated carbon is a versatile material with a wide range of applications due to its porous structure and large surface area. In this study, activated carbon was manufactured from cellulose using zinc chloride and phosphoric acid activation agents, and it was characterized using Brunauer-Emmett-Teller (BET), Field-Emission Scanning Electron Microscopes (FE-SEM), Energy Distribution Spectroscopy (EDS), mapping, and Fourier Transform Infrared Spectrophotometer (FTIR). Two different types of activated carbon utilized as a filler in Nitrile Butadiene Rubber (NBR)/Natural Rubber (NR) blends at different proportions (%0, %5, %10, %15 and 20%), and compared its properties to those of carbon black. The results showed that the addition of activated carbon improved the mechanical properties of the rubber blends, including hardness, tensile strength, and unit elongation. Furthermore, the experimental data obtained were used to examine the effects of carbon black, activated carbon salt, and activated carbon acid values on density, hardness, tensile strength, and percentage elongation variables using Multiple Linear Regressions (MLR). These models provided successful results in predicting the data with fewer experiments. The results have the potential to contribute to the promotion of the use of environmentally friendly materials in future research and to be an important step towards a sustainable industry.

Novel insight into the behavior of carbon in the positive active material of the lead-acid battery

Low-cost wood sawdust was investigated as a primary source for preparing active carbon to enhance the lead-acid battery. This can give a scope to determine the suitable active functional groups required to develop that battery. The fraction, −1.0 mm in size, was a potential feedstock for the active carbon preparation using phosphoric acid activation. The resulting precursor/H3PO4 mixture was pre-activated by solidifying at 150 °C for 2 h to eliminate water, leaving it a black adhesive solid. The hardened mixture was heated at 450 °C for an hour at a rate of 10 °C min−1 to complete the carbonization process. The produced active carbon was washed repeatedly with deionized water, dried at 105 °C, and saved in plastic for analysis and use, it was called (oxid-AC). The resulting active carbon has been identified using different analytical methods such as; XRD, SEM, FTIR, and BET. Results obtained revealed that the activated carbon additive, with a 2.5 % weight percentage, can reduce effectively the accumulation of PbSO4 at the positive active material (PAM) of the lead-acid battery. The role of the active carbon in improving the PAM behavior can be explained based on lead (II) ion adsorption on the carbon surface.

Selenite Adsorption and Reduction via Iron(II) Impregnated Activated Carbon Produced from the Phosphoric Acid Activation of Construction Waste Wood.

Chemical activation of waste materials, to form activated carbon, (AC) is complicated by the large amounts of chemical activating agents required and wastewater produced. To address these problems, we have developed an optimized process for producing AC, by phosphoric acid activation of construction waste. Waste wood from construction sites was ground and treated with an optimized phosphoric acid digestion and activation that resulted in high surface areas (> 2000 m2/g) and a greater recovery of phosphoric acid. Subsequently the phosphoric acid activated carbon (PAC), was functionalized with iron salts and evaluated for its efficacy on the adsorption of selenite and selenate. Total phosphoric acid recovery was 96.7% for waste wood activated with 25% phosphoric acid at a 1:1 ratio, which is a substantially higher phosphoric acid recovery, than previous literature findings. Post activation impregnation of iron salts resulted in iron(II) species adsorbed to the PAC surface. The iron(II) chloride impregnated AC removed up to 11.41 ± 0.502mg selenium per g Iron-PAC. Competitive ions such as sulfate and nitrate had little effect on selenium adsorption, however, phosphate concentration did negatively impact the selenium uptake at high phosphate levels. At 250ppm, approximately 75% of adsorption capacity of both the selenate and the selenite solutions was lost, although selenium was still preferentially adsorbed. Peak adsorption occurred between a pH of 4 and 11, with a complete loss of adsorption at a pH of 13.

The Influence of Activation Technique on the Adsorption of Coconut Coir-Activated Carbon in Four Potentially Dangerous Liquids

Coconut coir is one of the agricultural waste. According to the research it was utilized as an activated carbon. Activated carbon is produced by high temperatures and chemical. Activation process will be carried out by two types of chemical activators i.e. phosphoric acid and potassium hydroxide in 10%. The temperature at 750°C and using three time activation is about 60, 90 and 120 minutes. The result showed that phosphoric acid give the highest yield (42%) with a greater fixed carbon content (69%) than potassium hydroxide activation. As a result of activation with phosphoric acid and potassium hydroxide, the iod absorption value of activated carbon from coconut coir was 770 mg/g and 736 mg/g, respectively. Four potentially hazardous liquids, which revealed that activated carbon derived from phosphoric acid activation had the greatest adsorption capacity for chloroform. In contrast, activated carbon produced from potassium hydroxide activation has greater formaldehyde, ammonia, and benzene adsorption capacities. The findings of the study revealed that the iodine adsorption capacity of activated carbon obtained from the activation of phosphoric acid and potassium hydroxide was comparable (770 and 736 mg/g), indicating a different adsorption preference. Although the adsorption capacity of activated carbon iodine produced by phosphoric acid activation was greater, it was only superior to chloroform compared to the adsorption capacity of activated carbon produced by potassium hydroxide activation at the same concentration, temperature, and activation period. The results of the investigation indicate that the activator has a considerable effect on the adsorption preference of the activated carbon that is produced.

Highly effective removal of perfluorooctanoic acid (PFOA) in water with DBD-plasma-enhanced rice husks

Adsorption is regarded as an efficient method to eliminate per- and polyfluoroalkyl substances from an aqueous solution. In the present investigation, an adsorbent based on rice husks (RHs) was successfully prepared by phosphoric acid (PA) activation and dielectric barrier discharge (DBD) plasma treatment, and it was used to adsorb perfluorooctanoic acid (PFOA) from water. The electrodes employed in the experiment were planar type. This research investigated RH surface properties and adsorption capacity before and after modification using DBD plasma. The results revealed that the He–O2 plasma modification introduced oxygen-containing functional groups and increased the PFOA removal efficiency. Increasing the oxygen content and total gas flow rate to 30 vol.% and 1.5 L/min, respectively, with 10 min of RH plasma treatment time at 100 W plasma discharge power enhanced the PFOA removal efficiency to 92.0%, while non-treated RH showed the removal efficiency of only 46.4%. The removal efficiency of the solution increased to 96.7% upon adjusting the pH to 4. The adsorption equilibrium isotherms fitted the Langmuir model, and the adsorption kinetic followed the pseudo-second-order model. The maximum adsorption capacity was 565 mg/g when the Langmuir isotherm model was applied.

The production of activated carbon from Acacia erioloba seedpods via phosphoric acid activation method for the removal of methylene blue from water

Wastewater treatment requires a lot of granular activated carbon to absorb the dissolved organic components. This article describes a low-cost process for making highly active adsorption activated carbons from biomass, which could be used for wastewater treatment. A one-step carbonization and chemical activation with phosphoric acid at 500 °C produced low-cost acacia-derived porous activated carbons. The activated carbons' moisture, ash, volatile matter, and fixed carbon content were determined using proximate analysis. The activated carbon's adsorption qualities were also determined by studying its bulk density, surface morphology, power of hydrogen, iodine number, and methylene blue number index. To test the produced activated carbons for water treatment, batch adsorption dynamics were performed at room temperature for the removal of methylene blue from aqueous solution. Compared to activation using H2SO4, H3PO4 proves superior in generating well-developed pores, leading to a mesoporosity and microporosity structure with a larger surface area and high adsorption capacity. Brunauer–Emmett–Teller determined the sample's specific surface area, which was found to be 387 m2/g. The iodine number for 50, 100, and 200 μm activated carbon particles size was 620, 592, and 632 mg/g, respectively. The adsorption of MB on AC material better fits with Langmuir's adsorption isotherm; hence, particles are adsorbed on well-pronounced heterogeneous surfaces. The sips model is found to best represent the equilibrium data with R2 values of 0.994, suggesting the heterogeneous surface adsorption of MB on AC. Therefore, the adsorption of AC by MB involves physical and chemical processes. The produced AC hence appears to remove dissolved organic contaminants from raw water.

The valorization of rosemary waste as a new biosorbent to eliminate the rhodamine B dye

The widespread use of dyes is one of the leading causes of water contamination. Activated carbon is a common adsorbent used in water treatment by one of the most efficient physicochemical techniques: adsorption. As an agricultural waste, the conversion of unwanted rosemary biomass (stems and roots) into activated carbon material (RS-AC) was investigated using varied phosphoric acid activation ratios at 400 °C. Rhodamine B was utilized as a model dye in water in this work to understand better dye depolluting by RS-AC. Many standard methods were used to characterize the materials, including XRD, FTIR, Boehm titration, SEM/EDX, and pHzpc. The effects of RS-AC dosage, adsorption temperature, adsorption duration, and solution pH on the adsorption of Rhodamine B by RS-AC were studied better to understand the process's kinetic and thermodynamic characteristics. The thermodynamic study revealed that the adsorption process is endothermic, the pseudo-second-order kinetic model adequately explains the experimental data, and the equilibrium data showed an excellent fit to the Langmuir isothermal model for a maximum monolayer's adsorption capacity of Rhodamine B (Qmax = 65.78 mg/g). The density of function theory (DFT) was employed with the B3LYP/6-311G(d,p) base to get an idea for the activated sites on Rhodamine B and to explain the process of adsorption; eventually, the results agree with the experimental results.

Recycling waste by manufacturing biomaterial for environmental engineering: Application to dye removal

There are several disposal and governance difficulties due to rapid bio-waste growth. Therefore, recycling and repurposing them for environmental purposes is garnering increasing attention. Hydrothermal carbonization (HTC) followed by phosphoric acid activation was used in this investigation to synthesize a novel activated hydrochar (AHPP) from pomegranate peels. X-Ray Diffraction, Fourier-transform infrared spectroscopy, Scanning electron microscopy with energy dispersive X-ray spectroscopy, Brunauer, Emmett and Teller (BET) surface area analysis and Barrett-Joyner-Halenda (BJH) pore size distribution, and pH of zero charge were exploited to define the characteristics of AHPP, which was then used to assess the uptake of Basic Red 46 (BR46) dye in the batch mode. Isothermal and kinetic investigations were accomplished with pH = 6, 0.5 g.L−1 of adsorbent, 400 rpm at 298 K upon 60 min. The Freundlich model accurately presented the equilibrium curves with an adsorption capacity of 998.95 mg g−1, while the PSO kinetic model adequately corresponded to the experimental data. Furthermore, thermodynamic data disclosed that the process was spontaneous, endothermic, and linked to a growing disorder at the adsorbent-adsorbate interface. Lastly, the reuse investigation using HCl ascertained that AHPP might be recycled ten times, whereas a probable adsorption mechanism was proffered. Overall, it is possible to conclude that activated hydrochar generated from pomegranate peels as cost-effective waste could be employed as an alternative sorbent in dining substantial effluents retaining BR46.

High capacity adsorption of oxytetracycline by lignin-based carbon with mesoporous structure: Adsorption behavior and mechanism

In this study, an adsorbent with mesoporous structure and PO/PO bonds is prepared by hydrothermal and phosphoric acid activation from industrial alkali lignin for the adsorption of oxytetracycline (OTC). The adsorption capacity is 598 mg/g, which is three times higher than that of the adsorbent with microporous structure. The rich mesoporous structure of the adsorbent provides adsorption channels and filling sites, and π-π attraction, cation-π interaction, hydrogen bonds, and electrostatic attraction provide adsorption forces at the adsorption sites. The removal rate of OTC exceeds 98 % over a wide range of pH values (3–10). It has high selectivity for competing cations in water, with higher than 86.7 % removal rate of OTC from medical wastewater. After 7 consecutive adsorption-desorption cycles, the removal rate of OTC remains as high as 91 %. This efficient removal rate and excellent reusability indicate the strong potential of the adsorbent for industrial applications. This study prepares a highly efficient, environmentally friendly antibiotic adsorbent that can not only efficiently remove antibiotics from water but also recycle industrial alkali lignin waste.

Metal-free hybrid composite particles with phosphorus and oxygen-doped graphitic carbon nitride dispersed on kaolin for catalytic activity toward efficient hydrogen release

Here, hybrid kaolin-g-C3N4 heterostructure particles were fabricated by calcination in the first step, followed by hydrothermal phosphoric acid activation in the second step, and phosphorus (P) and oxygen (O) doped kaolin-g-C3N4 metal-free catalyst was synthesized. This hybrid metal-free catalyst was used for the first time for the production of effective hydrogen (H2) from sodium borohydride (NaBH4) methanolysis. The hydrogen generation rate (HGR) value of 5500 ml min−1g−1 was obtained with the P and O doped kaolin-g-C3N4 catalyst. The activation energy (Ea) of 31.90 kJ mol−1 by P and O doped kaolin-g-C3N4 for the production of H2 was obtained. The kaolin-g-C3N4 and P and O doped kaolin-g-C3N4 metal-free catalysts were systematically characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). Based on the results obtained, the mechanism of P and O-doped kaolin-g-C3N4 catalyst on H2 production from NaBH4 methanolysis was also proposed.

Regeneration of methylene blue-saturated biochar by synergistic effect of H2O2 desorption and peroxymonosulfate degradation

Biochar, as an adsorbent, is widely used for the removal of organic pollutants in water body. Hence, after saturated adsorption, regeneration treatment is required to recover the adsorption performance of biochar. In this study, a biochar (P-GBC) prepared by phosphoric acid activation showed high adsorption capacity for methylene blue (MB) with the maximum adsorption capacity (Qm) of 599.66 mg/g. Then, regeneration treatments using 4 mM peroxymonosulfate (PMS), 0.2 M hydrogen peroxide (H2O2) and their mixture were used to regenerate MB-saturated biochar with regeneration efficiencies of 58.24%, 66.01% and 94.88%, respectively. Combining with degradation and quenching experiments, it is found that synergistic effect of H2O2 desorption and PMS degradation is responsible for the enhancement of regeneration efficiency of P-GBC in H2O2-PMS system and enables a high mineralization rate of 82.68% for the MB adsorbed on P-GBC. Furthermore, EPR tests indicate that singlet oxygen (1O2) is assigned as the primary activate species for the degradation of MB and XPS analyses confirm that graphite nitrogen and carbonyl on P-GBC are the main active sites for the activation of PMS. Compared with conventional regenerants, H2O2-PMS system has the advantages of low dosage, high mineralization efficiency, and easy accessibility, and is also effective, sustainable and environmentally friendly for the regeneration of organic pollutants-saturated biochar.

Valorization of solid digestate into activated carbon and its potential for CO2 capture

Anaerobic digestion of agricultural waste for producing biogas as a renewable energy source is an established and promising technological option, producing a huge quantity of solid digestate as residue waste. Valorization of solid digestate into high-value products is necessary to make the anaerobic digestion process more cost-effective and enhance environmental benefits. In this study, activated carbon was fabricated from solid digestate with phosphoric acid activation in the fixed bed reactor. The physicochemical properties of the activated carbons have been analyzed by elemental analysis, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and N2 adsorption and desorption isotherms. The effect of H3PO4/digestate char impregnation ratio on structural and morphological change of the produced activated carbon was tested, and the function of H3PO4 in the activation procedure was discussed. The results indicated that an appropriate H3PO4/digestate char ratio was useful for the creation of pore structure. The highest surface area of 201 m2/g was attained at H3PO4/char ratio of 2 and at 600 °C. The potential for the use of the prepared activated carbon for CO2 capture was also evaluated thermogravimetrically under dynamic conditions, indicating good cyclic stability. This study provides the feasibility of integrating anaerobic digestion for biogas with subsequent activated carbon production from solid digestate.

Enhanced capacitance of phosphorus, nitrogen, and oxygen tri-doped balsa wood-based porous carbon for supercapacitors

Porous activated carbons derived from ultra-low density biomass of balsa wood are prepared by a one-step phosphoric acid activation method under different impregnation ratios without using dopants or post-treatments. These carbon materials are investigated and evaluated in terms of their morphology, texture structure, surface properties, chemical properties, and physical properties, as well as their electrochemical performance. The results indicate that the prepared phosphorus, nitrogen, and oxygen tri-doped balsa activated Carbons (PNOACs) exhibited hierarchical pore structures (micro-, meso-, and macropores). The surface area, pore size distribution, and also the heteroatoms (P/N/O) content of balsa wood active materials can be effectively controlled by the phosphoric acid activation process. Using PNOAC600-2, the active material electrode in the three-electrode system possesses a maximum specific capacitance of 263 F g−1 at 0.5 A g−1. The corresponding specific surface area and total pore volume are 1191.65 m2 g−1 and 1.19 cm3/g, respectively; while the heteroatom contents of nitrogen, phosphorus, and oxygen are 0.62, 3.43 %, and 15 %, respectively. Both the hierarchical pore structures and the heteroatoms have great influence and contribution to the specific capacitance performance. The assembled symmetric supercapacitor also exhibits a good capacitance retention rate (91.48 %), long-term charge/discharge cycling stability, and energy density (9.2 Wh kg−1). Using the one-step phosphoric acid activation method, a new method for developing and utilizing high-value balsa wood in the field of electrochemical energy storage is provided.

Mesoporous Activated Carbon from Leaf Sheath Date Palm Fibers by Microwave-Assisted Phosphoric Acid Activation for Efficient Dye Adsorption.

Remazol Brilliant Blue R (RBBR) is a common dye used in the industry, and its presence in wastewater and discharge into the environment can create a serious concern for the ecosystem and human health. Activated carbon produced from crop residues has emerged as a promising technique for removing contaminants from wastewater. In this study, leaf sheath date palm fiber-based activated carbon (LSDAC) was synthesized via phosphoric acid, H3PO4, treatment, followed by a microwave-induced carbonization process. The produced LSDAC was found to have a BET surface area of 604.61 m2/g, a Langmuir surface area of 922.05 m2/g, a total pore volume of 0.35 cm3/g, and an average pore size of 2.75 nm. The highest removal of RBBR was achieved at a solution pH of 3 (92.56 mg/g) and a solution temperature of 50 °C (90.37 mg/g). Adsorption of RBBR onto LSDAC followed the Langmuir isotherm model with a maximum monolayer capacity, Q m, of 243.43 mg/g, whereas in terms of kinetics, this adsorption system was best described by the pseudo-first-order (PFO) model. The calculated thermodynamic parameters ΔH°, ΔS°, ΔG°, and Arrhenius activation energy, E a, were 4.71 kJ/mol, 0.10 kJ/mol·K, -26.25 kJ/mol, and 5.88 kJ/mol, respectively, indicating that the adsorption of RBBR onto LSDAC was endothermic in nature, exhibited increased randomness at the solid-liquid interface, and was spontaneous and controlled by physisorption.