The effect of adsorbent textural and functional properties on model naphthenic acid adsorption.

Naphthenic acids, NAs, are a major contaminant of concern and a focus of much research around remediation of oil sand process affected waters, OSPW. Using activated carbon adsorbents are an attractive option given their low cost of fabrication and implementation. A deeper evaluation of the effect NA structural differences have on uptake affinity is warranted. Here we provide an in-depth exploration of NA adsorption including many more model NA species than have been assessed previously with evaluation of adsorption kinetics and isotherms at the relevant alkaline pH of OSPW using several different carbon adsorbents with pH buffering to simulate the behaviour of real OSPW. Uptake for the NA varied considerably regardless of the activated carbon used, ranging from 350 mg/g to near zero highlighting recalcitrant NAs. The equilibrium data was explored to identify structural features of these species and key physiochemical properties that influence adsorption. We found that certain NA will be resistant to adsorption when hydrophobic adsorbents are used. Adsorption isotherm modelling helped explore interactions occurring at the interface between NA and adsorbent surfaces. We identified the importance of NA hydrophobicity for activated carbon uptake. Evidence is also presented that indicates favorable hydrogen bonding between certain NA and surface site hydroxyl groups, demonstrating the importance of adsorbent surface functionality for NA uptake. This research highlights the challenges associated with removing NAs from OSPW through adsorption and also identifies how adsorbent surface chemistry modification can be used to increase the removal efficiency of recalcitrant NA species.

Adsorption of typical NDMA precursors by superfine powdered activated carbon: Critical role of particle size reduction.

Control of N-nitrosodimethylamine (NDMA) in drinking water could be achieved by removing its precursors as one practical way. Herein, superfine powdered activated carbons with a diameter of about 1 µm (SPACs) were successfully prepared by grinding powdered activated carbon (PAC, D50=24.3 µm) and applied to remove model NDMA precursors, i.e. ranitidine (RAN) and nizatidine (NIZ). Results from grain diameter experiments demonstrated that the absorption velocity increased dramatically with decreasing particle size, and the maximum increase in k2 was 26.8-folds for RAN and 33.4-folds for NIZ. Moreover, kinetic experiments explained that rapid absorption could be attributed to the acceleration of intraparticle diffusion due to the shortening of the diffusion path. Furthermore, performance comparison experiments suggested that the removal of RAN and NIZ (C0=0.5 mg/L) could reach 61.3% and 60%, respectively, within 5 min, when the dosage of SAPC-1.1 (D50=1.1 µm) was merely 5 mg/L, while PAC-24.3 could only eliminate 17.5% and 18.6%. The adsorption isotherm was well defined by Langmuir isotherm model, indicating that the adsorption of RAN/NIZ was a monolayer coverage process. The adsorption of RAN or NIZ by SAPC-1.1 and PAC-24.3 was strongly pH dependent, and high adsorption capacity could be observed under the condition of pH > pka+1. The coexistence of humic acid (HA) had no significant effect on the adsorption performance because RAN/NIZ may be coupled with HA and removed simultaneously. The coexistence of anions had little effect on the adsorption also. This study is expected to provide an alternative strategy for drinking water safety triggered by NDMA.

Engineering Electrode Polarity for Enhancing In Situ Generation of Hydroxyl Radicals Using Granular Activated Carbon.

Recently, granular activated carbon (GAC) has shown its effectiveness as a cathode material for in situ ROS generation. Here, we present an electrochemically modified GAC cathode using electrode polarity reversal (PR) approach for enhanced H2O2 decomposition via 2-electron oxygen reduction reaction (2e-ORR). The successful GAC modification using PR necessitates tuning of the operational parameters such as frequency, current, and time intervals between the PR cycles. This modification enhances the GAC hydrophilicity by increasing the density of surface oxygen functionalities. After optimization of the electrode polarity, using the 20 (No PR)-2 (PR) interval and 140 mA current intensity, the •OH concentration reaches 38.9 µM compared to the control (No PR) (28.14 µM). Subsequently, we evaluated the enhanced •OH generation for the removal of glyphosate, a persistent pesticide used as a model contaminant. The modified GAC using PR removed 67.6% of glyphosate compared to 40.6% by the unmodified GAC without PR, respectively. The findings from this study will advance the utilization of GAC for in situ ROS synthesis, which will have direct implications on increasing the effectiveness of electrochemical water treatment systems.

NaCl aerosol filtration over filter media with intrafiber porosity: Can filtrate capacity be increased by wicking into this pore volume?

This paper investigates a novel fiber-based filter media wherein a NaCl filtrate is collected and reservoired not only onto the surfaces of the fibers and within their inter-fiber voidage but also within the internal porosity of high pore volume nanoporous fibers or VGCF floc used to fabricate the media. This transport process is shown to occur through a NaCl dissolution into the water-filled nanopores of the fiber and a subsequent intra-fiber wicking phenomenon. The study further elucidates two distinct NaCl accommodation mechanisms which are uniquely available to filter media containing nanoporous intrafiber porosity: 1) wicking and capillary condensation of liquid NaCl aerosols directly into the intrafiber pores at high RH, and 2) dissolution of otherwise solid NaCl aerosols deposited onto fiber surfaces (at low RH) into the interior nanopores of the fiber because these pores (when hydrophilic) are saturated with water (even at low RH). To investigate these two mechanistic regimes, various media were fabricated possessing multiscale porosity in the form of: (i) embedded flocs of Vapor Grown Carbon Nanofibers (VGCFs) (4.108 cm3/gm pore volume), (ii) hydrophilic and high pore volume Activated Carbon Fibers (ACFs, 0.950 cm3/gm) and (iii) solid graphite fibers. These media were then comparatively evaluated toward NaCl aerosol filtration at different relative humidities. Pressure drop measurements versus filtrate accumulation and SEM-EDAX VGCF demonstrated the location and transport of NaCl into the intrafiber voidage. Media containing both VGCF floc and ACF accumulated 1200% more NaCl at low RH (and a specified pressure drop) than similar media prepared from non-porous graphite fibers, with an additional 315% increase from low to high RH. A Gibbs free energy driving force model is provided to illustrate the driving forces favoring water condensation into the nanopores and solid NaCl aerosol dissolution into the water phase. Filtration efficiency and Quality Factor assessments for the various media are also systematically evaluated to demonstrate the observed mechanistics.

Removal of Amoxicillin From Wastewater Onto Activated Carbon: Optimization of Analytical Parameters by Response Surface Methodology.

Antibiotics are widely used in veterinary and human medicine, but these compounds, when released into the aquatic environment, present potential risks to living organisms. In the present study, the activated carbon (AC) used for their removals is characterized by FT-IR spectroscopy, BET analysis and Scanning Electron Microscopy (SEM) to determine the physicochemical characteristics. Response surface methodology (RSM) and Box-Behnken statistical design (BBD) were used to optimize important parameters including pH (2-12), temperature (20-45°C), and AC dose (0.05-0.20 g). The experimental data were analyzed by analysis of variance (ANOVA) and fitted to second-order polynomial using multiple regression analysis. The optimal conditions for maximum elimination of Amoxicillin (Amox) are (Dose: 0.124 g, pH 5.03 and 45°C) by applying the desirability function (df). A confirmation experiment was carried out to evaluate the accuracy of the optimization model and maximum removal efficiency (R = 89.999%) was obtained under the optimized conditions. Several error analysis equations were used to measure goodness of fit. Pareto analysis suggests the importance of the relative order of factors: pH > Temperature > AC dose in optimized situations. The equilibrium adsorption data of Amox on Activated Carbone were analyzed by Freundlich, Elovich, Temkin and Langmuir models. The latter gave the best correlation with qmax capacities of 142.85 mg/g (R2 = 0.999) at 25°C is removed from solution. The adsorption process is dominated by chemisorption and the kinetic model obeys a pseudo-second order model (R2 = 0.999).

Calcium Oxide Adsorption of Gas Phase PCDD/Fs and Its Impact on the Adsorption Properties of Activated Carbon.

Calcium oxide (CaO), utilized in semi-dry/dry desulfurization systems at municipal solid waste incineration (MSWI) plants, demonstrates some capability to remove polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study assessed the gas-phase PCDD/F removal performance of CaO, activated carbon (AC) and CaO-AC mixtures. Alone, CaO achieved removal efficiencies of only 31.9% for mass and 50.8% for I-TEQ concentration. However, CaO-AC mixtures exhibited significantly higher efficiencies, reaching 96.0% and 92.5% for mass and I-TEQ concentrations, respectively, surpassing those of AC alone, which were 74.7% and 58.5%. BET analysis indicated that CaO's limited surface area and pore structure are major constraints on its adsorption performance. Density functional theory (DFT) calculations revealed that the π-π electron donor-acceptor (EDA) interaction enhances the adsorption between AC and PCDD/F, with adsorption energies ranging from -1.02 to -1.24 eV. Additionally, the induced dipole interactions between CaO and PCDD/F contribute to adsorption energies ranging from -1.13 to -1.43 eV. Moreover, with increasing chlorination levels, PCDD/F molecules are more predisposed to accept electron transfers from the surfaces of AC or CaO, thereby facilitating adsorption. The calculation for mixed AC and CaO showed that CaO modifies AC's properties, enhancing its ability to adsorb gas phase PCDD/Fs, with the higher adsorption energy and more electrons transfer, aligning with gas phase PCDD/Fs adsorption experiments. This study provides a comprehensive understanding of how CaO influences the PCDD/F adsorption performance of AC.

Comparison of surface adsorption efficacies of eco-sustainable agro/animal biomass-derived activated carbon for the removal of rhodamine B and hexavalent chromium.

Effective management and remediation strategies are crucial to minimize the impacts of both organic and inorganic contaminants on environmental quality and human health. This study investigates a novel approach utilizing cotton shell activated carbon (CSAC), rice husk activated carbon (RHAC), and wasp hive activated carbon (WHAC), produced through alkali treatment and carbonization under N2 atmosphere at 600 °C. The adsorption capacities of biomass-derived mesoporous activated carbons (CSAC, RHAC, WHAC) alongside macroporous commercial activated carbons (CAC) were evaluated for removing rhodamine B (Rh B) and hexavalent chromium (Cr6+). The CSAC exhibits remarkable adsorption efficiency (255.4 mg.g-1) for Cr(VI) removal, while RHAC demonstrates superior efficacy (174.2 mg.g-1) for Rh B adsorption. Investigating various optimal parameters including initial pH (pH 3 for Cr and pH 7 for Rh B), catalyst dosage (200 mg.L-1), and initial concentration (20 mg.L-1), the Redlich-Peterson isotherm model is applied to reveal a hybrid adsorption mechanism encompassing monolayer (chemisorption) and multilayer (van der Waals adsorption) processes. Kinetic analysis highlights the pseudo-second-order and Elovich models as the most suitable, suggesting physiochemisorption mechanisms. Thermodynamic analysis indicates the endothermic nature of the adsorption process, with increased randomness at the solid-solution interface. Isosteric heat investigations using Clausius-Clapeyron, Arrhenius, and Eyring equations reveal a heterogeneous surface nature across all activated carbons. Further confirmation of Rh B and Cr(VI) adsorption onto activated carbons is provided through FTIR, FESEM, and EDAX analysis. This study highlights the innovation and promise of utilizing biomass-derived activated carbons for effective pollutant removal.

Preparation of magnetic activated carbon fibers@Fe3O4 by electrostatic self-assembly method and adsorption properties for methylene blue.

Nano-Fe3O4 was loaded onto coconut-based activated carbon fibres (CACF) using an electrostatic self-assembly method. The effects of the mass ratio of CACF to nano-Fe3O4, loading time, pH and temperature on the loading effect were investigated and ideal loading conditions were determined. To study the adsorption performance of MACF@Fe3O4 for methylene blue, the effects of the initial concentration, pH and time on the adsorption were investigated and the working conditions of adsorption were established. MACF@Fe3O4 was systematically characterized. Adsorption kinetics were investigated under ideal conditions. The ideal loading conditions for MACF@Fe3O4 were as follows: mass ratio of 1:1, 20 min, pH 9.36, 22.5°C. The saturation magnetization of MACF@Fe3O4 was 48.2263 emu·g-1, which could be quickly separated under an external magnetic field. When the dosage was 0.010 g, the adsorption rate reached 97.29% and the maximum adsorption capacity was 12.1616 mg·g-1. The adsorption process conformed to pseudo-first-order kinetics during the first 15 min and pseudo-second-order kinetics during 20-120 min. The equations were ln( Q e - Q t )=2.2394-0.0689t and t Q t =0.0774 + 0.5295t , respectively. The isothermal adsorption model showed that MACF@Fe3O4 was more in line with the Langmuir model, indicating that the adsorption process was mainly monolayer adsorption. The thermodynamic analysis results showed that the adsorption process of MB by MACF@Fe3O4 was an endothermic process. In this study, MACF@Fe3O4 with high adsorption capacity and easy separation from coconut palm fibres has good application prospects in the field of adsorption, which can promote the high-value utilization of coconut palms.

New biocatalyst produced from fermented biomass: improvement of adsorptive characteristics and application in aroma synthesis.

This study presents a novel approach to producing activated carbon from agro-industrial residues, specifically cocoa fruit peel, using solid-state fermentation (SSF) with Aspergillus niger. The process effectively degrades lignin, a major impediment in traditional activated carbon production, resulting in a high-quality carbon material. This carbon was successfully utilized for enzyme immobilization and aroma synthesis, showcasing its potential as a versatile biocatalyst. The study meticulously evaluated the physical and chemical attributes of activated carbon derived from fermented cocoa peel, alongside the immobilized enzymes. Employing a suite of analytical techniques-electrophoresis, FTIR, XRD, and TG/DTG the research revealed that fermentation yields a porous material with an expansive surface area of 1107.87 m2/g. This material proves to be an excellent medium for lipase immobilization. The biocatalyst fashioned from the fermented biomass exhibited a notable increase in protein content (13% w/w), hydrolytic activity (15% w/w), and specific activity (29% w/w), underscoring the efficacy of the fermentation process. The significant outcome of this research is the development of a sustainable method for activated carbon production that not only overcomes the limitations posed by lignin but also enhances enzyme immobilization for industrial applications. The study's findings have important implications for the agro-industrial sector, promoting a circular economy and advancing sustainable biotechnological processes.

N-doped lignin-based activated carbon aerogel derived from bamboo black pulp liquor for efficient removal of malachite green in wastewater.

In this study, a lignin-based aerogel (LA) was prepared through acid precipitation of BPBL, followed by sol-gel method and freeze-drying. Additionally, a one-step activation-carbonization method was used to acquire nitrogen-doped lignin-based activated carbon aerogel (NLACA). The adsorption and catalytic degradation performance for malachite green (MG) were examined. The specific surface area of NLACA after N-doping was 2644.5 m2/g. The adsorption capacity for MG was increased to 3433 mg/g with the presence of nitrogenous functional groups on surface of NLACA compared without N-doping. Meanwhile, non-radical singlet oxygen is the primary active substance and degradation efficiency arrives at 91.8% after the catalytic degradation within 20 min and it has good stability and reuse. Three possible degradation pathways during degradation were analyzed by LC-MS technique. The adsorption isotherm and kinetic data demonstrated conformity with both the Langmuir model and the pseudo-second-order kinetic model. The primary mechanisms of the adsorption for MG dyes on NLACA include hydrogen bonding, π-π interactions, attraction of electrostatic and pore filling. Hence, NLACA derived from BPBL acts as a cost-effective and high-performance adsorbent and catalyst for removal of MG in dye wastewater. This concept introduces an innovative approach of "treatment of waste with waste" for developing a low-consumption, high-efficiency dye wastewater treatment and provides significant reference to treatment dye wastewater.

Chlorinated volatile organic compounds (CVOCs) and 1,4-dioxane kinetics and equilibrium adsorption studies on selective macrocyclic adsorbents.

Chlorinated volatile organic compounds (CVOCs) are often found in combination with 1,4-dioxane which has been used as a solvent stabilizer. It would be desirable to separate these compounds since biodegradation of 1,4-dioxane follows an aerobic pathway while anaerobic conditions are needed for biodegrading CVOCs. Conventional adsorbents such as activated carbon (AC) and carbonaceous resins have high adsorption capacities for 1,4-dioxane and CVOCs but lack selectivity, limiting their use for separation (Liu et al., 2019). In the current work, two macrocyclic adsorbents, ß-CD-TFN and Res-TFN, were examined for selective adsorption of chlorinated ethenes in the presence of 1,4-dioxane. Both adsorbents exhibited rapid adsorption of the CVOCs and minimal adsorption of 1,4-dioxane. Res-TFN had a higher adsorption capacity for CVOCs than ß-CD-TFN (measured linear partition coefficient, Kd 2140 -9750 L⋅kg-1 versus 192-918 L⋅kg-1 for 1,1, DCE, cis-1,2-DCE and TCE, respectively) and was highly selective for CVOCs(TCE Kd ~117 Kd for 1,4-dioxane). By comparison, TCE and 1,4-dioxane adsorption on AC was approximately equal at 100 µg⋅L-1 and approximately 1/3 of the adsorption of TCE on the Res-TFN. The greater adsorption and selectivity of Res-TFN suggest that it can be used as a selective adsorbent to separate CVOCs from 1,4-dioxane to allow separate biodegradation.

Monitoring carbon-based remediation of DNAPL-contaminated groundwater via spectral induced polarization.

Colloidal activated carbon (CAC) is an emerging remedial enhancement fluid that is injected into the subsurface to adsorb hazardous industrial compounds for subsequent removal. CAC-enhanced remediation relies on accurate subsurface characterization and monitoring to ensure CAC reaches intended treatment locations. The objective of this study was to assess the effectiveness of the spectral induced polarization (SIP) technique to track CAC migration within porous media and its adsorption of the chlorinated solvent, tetrachloroethylene (PCE). Dynamic column experiments were performed with cyclic injection and flow of groundwater, CAC, and PCE within porous media, and simultaneous measurements of SIP and effluent quality. Results showed an increase in both the real and imaginary conductivities of the SIP response during injection/flow of CAC within porous media. Real conductivity returned to pre-CAC levels during subsequent flushing of CAC with groundwater, which had left behind only carbon-coated soil grains; however, imaginary conductivity identified the change in polarizability due to the alterations on the grain surface. The subsequent adsorption of aqueous phase PCE did not generate a distinctive change in SIP response, mainly due to the low 50 mg/L concentrations used. Overall, this study suggests that SIP can be a valuable tool to effectively and non-invasively track the migration of injected CAC within porous media for contaminant adsorption, suggesting it can be used to enhance the implementation and management of environmental remediation programs.

Benchmarking produced water treatment strategies for non-toxic effluents: Integrating thermal distillation with granular activated carbon and zeolite post-treatment.

The management of produced water (PW) generated during oil and gas operations requires effective treatment and comprehensive chemical and toxicological assessment to reduce the environmental risks associated with reuse or discharge. This study evaluated a treatment train that included a low-temperature thermal distillation pilot system followed by granular activated carbon (GAC) and zeolite post-treatment for processing hypersaline Permian Basin PW. Our study provides a unique and comprehensive assessment of the treatment efficiency considering a targeted chemical scheme together with whole effluent toxicity (WET) tests across four trophic levels regarding aquatic critical receptors of concern (ROC): Raphidocelis subcapitata, Vibrio fischeri, Ceriodaphnia dubia, and Danio rerio. The distillate from the thermal distillation process met various numeric discharge standards for salinity and major ions. However, it did not meet toxicity requirements established by the United States National Pollutant Discharge Elimination System program. Subsequent post-treatment using GAC and zeolite reduced the concentration of potential stressors, including volatile organics, NH3, Cd, Cr, Zn, and Mn in the final effluent to below detection limits. This resulted in a consistent toxicity reduction across all WET tests, with no observable adverse effects for R. subcapitata, C. dubia, and D. rerio (no observed effect concentration >100%), and V. fischeri effects reduced to 19%. This study realizes the feasibility of treating PW to non-toxic levels and meeting reuse and discharge requirements. It underscores the importance of implementing integrated treatment trains to remove the contaminants of concern and provides a systematic decision framework to predict and monitor environmental risks associated with PW reuse.

Exploration of the adsorption and desorption performance of volatile organic compounds by activated carbon with different shapes based on fixed-bed experiments.

Activated carbon (AC) has been widely used in volatile organic compounds (VOCs) treatment of industrial exhaust gases. Rather than modifying specific pore size distributions and surface properties, altering the shape of AC offers a more feasible approach to enhance its adsorption performance. This study investigates the adsorption-desorption performance of two different shaped ACs with highly similar properties for the removal of VOCs. The clover-shaped AC (CSAC) has a 27.46% lower internal void fraction and a 39.10% higher external void fraction compared to cylindrical AC (CAC), resulting in denser packing and longer contact time with VOCs. Adsorption experiments showed the CSAC has 40% longer adsorption breakthrough (BT) times for ethanol, ethyl acetate, and n-hexane on average, and 20% higher saturation adsorption capacity per unit volume. CSAC also has higher partition coefficients, with the highest values for ethanol, ethyl acetate, and n-hexane being 0.0187, 0.0382, and 0.0527 mol·kg-1·Pa-1, respectively. The desorption process for selected VOCs is non-spontaneous and endothermic. Optimal desorption conditions were identified as an inlet space velocity of 3535 h-1, a desorption temperature of 150 °C, and a pulsed inlet method. To investigate the possibility of the application of CSAC in real-world scenarios, xylene was chosen as a representative industrial VOC. Results showed CSAC has 20% higher BT time and saturation adsorption capacity for xylene compared to CAC under different bed heights. The desorption efficiency for xylene on both ACs is below 40%. With increasing xylene inlet concentration, the mass transfer zone (MTZ) height initially increases but stabilizes beyond 1704 mg·m-3. At identical bed heights, the MTZ height of CSAC is 29% shorter than CAC, indicating a higher bed utilization efficiency.

Removal of Rhodamine-B dye from Aqueous Solutions Using Alkaline-Modified Activated Carbon from Cocoa Pod Husk.

Rhodamine-B (RhB) dye in wastewater poses health and environmental risks due to respiratory and eye infections, neurotoxicity, and carcinogenicity, necessitating proper disposal for risk mitigation. This study investigates RhB removal from water using NaOH-modified activated carbon derived from cocoa pod husk (CPHAC). Employing a face-centered central composite design, operational variables were optimized to achieve maximum RhB dye removal efficiency. The study reveals a removal efficiency of 98.87 ± 0.84% under optimized conditions: adsorbent dose of 1.34 g, contact time of 71.59 min, and an initial RhB concentration of 6.61 ppm. The Freundlich isotherm model demonstrated a good fit, suggesting that RhB removal is governed by heterogeneity and multilayer adsorption. Kinetic experiments revealed that adsorption follows a pseudo-second-order model, indicating likely irreversible adsorption with dye molecules forming chemical bonds on CPHAC's surface. Overall, this study demonstrates the effectiveness of CPHAC as an efficient adsorbent for RhB removal from water.

Electrochemical oxidation of ethanol on NiO/MoO2 hybridized wheat husk derived activated carbon.

The Ethanol oxidation process in fuel cells is most efficient when conducted by Platinum based catalysts. Our research team endeavored to find affordable and efficient catalysts, synthesizing catalysts based on metal oxides of nickel and molybdenum in the form of NiO/ MoO2 and NiO/ MoO2 hybridized with activated carbon obtained from the wheat husk (ACWH) through a hydrothermal method. After precise physical characterization, the capability of these catalysts in the ethanol oxidation process was measured through electrochemical analyses in an alkaline environment. The presence of ACWH in the catalyst structure significantly improves the active surface and electrocatalytic activity. NiO/MoO2/ACWH with a current density of 16 mA/cm2 at a peak potential of 0.55 V and 93% cyclic stability after 5000 alternate CV cycles, can be an appealing, relatively efficient, and stable option in ethanol oxidation. .

Enhanced Adsorption of Gaseous Naphthalene by Activated Carbon Fibers at Elevated Temperatures.

This study utilized activated carbon fibers (ACFs) as adsorbents to investigate the removal efficiency of naphthalene and toluene at elevated temperatures and their competitive adsorption behavior. Three types of ACFs, inlet concentrations of naphthalene (343, 457, and 572 mg·Nm-3), and toluene (2055, 2877, and 4110 mg·Nm-3) were investigated to determine the adsorption capacities of naphthalene and toluene. To study the reaction mechanisms of naphthalene and toluene on the ACFs, the BET, SEM, FTIR, and TGA methods were used to examine the physical and chemical characteristics of ACFs. Results showed ACF-A's superior adsorption capacity for naphthalene that was attributed to its mesoporous structure and hydrophobicity. Adsorption equilibrium studies indicated multilayer adsorption behavior. Competitive adsorption experiments demonstrated the displacement of toluene by naphthalene on ACF-A, highlighting its higher selectivity for naphthalene. Functional group analysis revealed changes in ACF surfaces after naphthalene adsorption, suggesting π-π dispersion and electron donor-acceptor interactions. Overall, this study underscores the importance of pore structure and surface properties in designing ACFs for the efficient adsorption of high-boiling-point organic pollutants.

Upcycling waste polyethylene terephthalate (PET) bottles into high-performance activated carbon for electrochemical desalination.

Upcycling waste polyethylene terephthalate (PET) bottles has attracted intensive research interests. This simultaneously alleviates plastic pollution and achieves a waste-to-resource strategy. Waste PET water bottles were used to fabricate value-added activated carbon (AC) electrodes for capacitive deionization (CDI). The KOH activation temperature (greater than 700 °C) prominently affected the physi-chemical properties and desalination performance of PET-derived activated carbons (PET-AC). Profiting from a large Brunauer-Emmet-Teller specific surface area (1448 m2 g-1) with a good mesoporous structure (the ratio of the mesopore volume to the total pore volume was 41.3%), PET-AC-1000 (activated at 1000 °C) possessed a huge specific capacitance of 108 F g-1 for capacitive ion storage. Moreover, when utilized as the electrode material in single-pass CDI, PET-AC-1000 exhibited a maximum electrosorption capacity of 10.82 ± 0.11 mg g-1 and a low level of energy consumption (0.07 kWh mol-1), associated with good electrochemical charging-discharging cyclic stability. The results provide a promising facile approach to tackle the challenge of plastic pollution and promote the advancement of electrode materials for economic affordable and energy-efficient electrochemical desalination process, which meets the United Nations (UN) sustainable development goals (SDGs).

A highly efficient modified nano-activated carbon adsorbent for separation of ammonia from water: Experimental and kinetics elucidations.

Water is essential for the survival of all living things; however, its extensive use in agriculture, high-tech manufacturing, energy production, and the rapid development of the chemical and petroleum industries has led to significant contamination, making water pollution a major concern today. Ammonia is one of the most harmful contaminants present in water, posing significant environmental and health risks that require appropriate remediation methods. To remove ammonia from contaminated water, we employ Carbon Nanotubes (CNTs) and Activated Carbon (AC). To ensure appropriate metal impregnation on the adsorbents, Fe, Al, Ag, and Cu were impregnated into both CNT and AC, followed by extensive characterization using Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), and Energy Dispersive X-rays (EDX). To optimize ammonia removal from water, several parameters were adjusted, including pH, dose amount, contact time, shaking speed, and temperature. Astonishingly, the highest removal efficiency of 40% was achieved with a 1 g dosage at pH 10.5 and 200 RPM, while silver oxide had a lower removal rate of 10% under the same conditions. Temperature additionally had a significant impact, with removal percentages reaching 40% at 70 °C as compared to 21.5% at 25 °C. Adsorption isotherms were used to analyze the experimental data, along with Langmuir and Freundlich's models. Notably, Langmuir produced superior curve fitting, resulting in a correlation factor close to one. Furthermore, kinetic modeling was carried out with 2nd-order and pseudo-2nd-order equations, with the latter responding better according to curve analysis. Because the ammonia removal rate was low, this study indicates the feasibility of implementing an adsorption technique using CNT and AC as a pre-treatment method for this purpose. This approach has the potential for future optimization and deployment in tackling water contamination concerns effectively.

Efficient sequestration of cesium ions using phosphoric acid-modified activated carbon fibers from aqueous solutions.

In this study, acid-modified activated carbon fibers (ACF-Ps) were synthesized by phosphorylation. Three different types of ACF-based adsorbents functionalized with PO43-, P2O74-, or P3O105- ions, namely, ACF-P1, ACF-P2, and ACF-P3, were prepared by phosphorylating ACF with trisodium phosphate (Na3PO4), sodium dihydrogen pyrophosphate (Na2H2P2O5), and sodium tripolyphosphate (Na5P3O10), respectively, and utilized as adsorbents to remove cesium ions (Cs+) from aqueous solutions. Among the tested adsorbents, ACF-P3 exhibited the highest Cs+ adsorption capacity of 37.59 mg g-1 at 25 °C and pH 7 which is higher than that of ACF (5.634 mg g-1), ACF-P1 (19.38 mg g-1), and ACF-P2 (30.12 mg g-1) under the same experimental conditions. More importantly, the Cs+ removal efficiencies of ACF-P3 (82.90%), ACF-P2 (66.2%), ACF-P1 (34.2%) were 29.3-, 23.4-, and 12.11-fold higher than that of un-treated ACF (2.83%). The results suggested that the phosphorylation with Na5P3O10 is highly suitable for Cs+ adsorption which effectively functionalizes ACF with a greater number of phosphate functional groups. Adsorption and kinetic data well-fitted the Langmuir isotherm and pseudo-second-order model, respectively, which indicated the monolayer adsorption of Cs+ onto ACF-P1, ACF-P2, and ACF-P3 which were largely controlled by chemisorption. Overall, phosphoric acids containing different phosphate-based polyanions (PO43-, P2O74-, or P3O105-) enriched -OH and/or -COOH surface functional groups of ACF in addition to P-containing surface groups (PO, C-P-O, C-O-P, and P-O) and facilitated the Cs+ adsorption through surface complexation and electrostatic interactions.