Carbon Adsorption Research Articles

Extensive investigation of seasonal and spatial fluctuations of BTEX in an industrial city with a health risk assessment

There are many pollutants in the air that can be harmful to human health. Their impact varies based on factors such as the kind of pollutant, duration of exposure, and concentration levels. Volatile organic compounds are particularly significant carcinogens among the various pollutants present in the air. Consequently, people who are exposed to these harmful airborne pollutants suffer permanent consequences. This study examines the properties of BTEX compounds—benzene, toluene, ethylbenzene, and xylene—as well as their sources and risk assessments throughout a one-year period from March 21, 2019, to March 20, 2020, in Karaj, Iran’s largest industrialized city. First, utilizing a geographical information system that covered the entire city, 17 locations within Karaj were chosen for this purpose. Then, samplings were carried out in the spring, summer, autumn, and winter months with the NIOSH 1501 method. During the research period, 68 samples of BTEX compounds were collected. The adsorption of these contaminants on the activated carbon adsorbents was performed using an environmental sampling pump with a flow rate of 0.2 L/min for 1 h. The samples were subsequently prepared using a carbon disulfide solution and injected into a GC-FID for analysis. In this research, the average annual concentration of BTEX compounds in the air of Karaj city was obtained at 33.01 µg/m3. Autumn and spring had the highest and lowest average concentrations of BTEX compounds, respectively. In addition, sites 5 and 8 had the highest average annual concentrations of these pollutants. The sourcing conducted in this study showed that transportation and fuel consumption, as well as industries, were the primary sources of pollution in the city. In addition, the excess lifetime cancer risk was higher than the guideline value in some sites and lower in others. Furthermore, the Hazard Quotients were lower than 1, but in general, the citizens of Karaj were at serious risk from exposure to this group of pollutants.

Integrated spectral based monitoring, optimization and control of the combined ozonation and powdered activated carbon adsorption process to remove organic micropollutants from secondary effluent

In this study, an innovative approach for the integrated monitoring, optimization and control of the combined ozonation (O3) and powdered activated carbon (PAC) adsorption process is introduced making use of spectral surrogates (UVA254 and EEM-PARAFAC components). The combined O3-PAC process is designed to remove organic micropollutants (µP) from secondary effluent. Therefore, the removal of 6 µP with varying ozone reactivity was systematically studied in both O3 and PAC as stand-alone systems and in the combined O3-PAC system. For the latter, adsorption experiments were performed with µP spiked into ozonated secondary effluent (sequential system) and with µP spiked into the initial secondary effluent before ozonation (integrated system). In accordance with Swiss standards, the goal was to achieve 80% atrazine removal (as a model O3 recalcitrant compound) at optimized O3 and PAC doses. An ozone dose ranging from 0.45 to 0.65 mg O3/mg DOC was more cost-effective in promoting subsequent PAC adsorption (less than 40%), particularly at low PAC doses (1-2 mg PAC/mg (initial (DOC))). The classical ideal adsorbed solution theory (IAST) model could not be used to predict the subsequent PAC dose after ozonation in the integrated system. Therefore, correlation models were established between (i) the reduction of spectral surrogates during both O3 and PAC dosing and µP removal, (ii) the reduction of spectral surrogates during ozonation and the related PAC dose of the subsequent adsorption process and (iii) between the reduction of spectral surrogates during ozonation and the integrated process. Based on these correlation models, an online spectral control strategy was developed and implemented. Finally, the optimal dosing strategy for 80% atrazine removal was determined as 0.5 mg O3/mg DOC and 1.4 mg PAC/mg (initial) DOC.

Adsorption of Carotenoids, Chloride, and Sulfate from Annatto Dye Agro-Industrial Effluent

<p>Natural dyes, such as annatto, are widely used in the food and pharmaceutical industries. However, the effluents from annatto dye production pose environmental challenges due to the presence of residual dye components, organic matter, and dissolved inorganic species (chloride and sulfate). This study, the first attempt in the literature to deal with real annatto dye effluent, aimed to evaluate the use of activated carbon for the removal of carotenoids (norbixin), chloride, and sulfate. A 2³ full-factorial design was employed to optimize the adsorption process parameters (temperature, pH, and adsorbent mass). The results showed that up to 90% of carotenoids and chloride could be removed under optimized conditions (low temperature and pH). Sulfate removal was more strongly influenced by the pH of the medium, with a maximum removal of 53%. The adsorption process was well-described by empirical models, though traditional isotherm models did not adequately represent the experimental data. Hypotheses that support isotherm models such as pore homogeneity, monolayer formation, constant internal diffusion were not satisfied. This study demonstrates the potential of activated carbon adsorption as a feasible method for treating food industry effluents containing high loads of carotenoids and inorganic salts.</p>

Towards a high-rate operation of contact stabilization process: A microscopic view of carbon capture properties

Carbon capture performance is a key factor determining the chemical energy recovery potential of the high-rate contact stabilization (HiCS) process. However, the mechanisms of organic carbon capture are complex, involving surface adsorption, extracellular adsorption, and intracellular storage. A unique characteristic of the HiCS process is its low sludge residence time (SRT). Unfortunately, the influence of SRT on carbon capture has not been thoroughly studied, especially in terms of the underlying mechanisms. In this study, the microscopic changes in carbon capture performance during the transition from a conventional contact stabilized (CS) system to a high-rate mode of operation were demonstrated using intracellular carbon sources, extracellular polymeric substances (EPS), signaling molecules, and microbial community assays. The results showed that the extracellular carbon adsorption and intracellular carbon storage performance increased, and the microbial community structure changed significantly with converting the CS system to the high-rate operation mode. The enhancement of extracellular carbon adsorption performance mainly relied on the growth of EPS, which was accomplished by the strong growth of the relative abundance of the dominant bacterial group Cloacibacterium within the HiCS system, offsetting the negative effect produced by the decline of acyl-homoserine lactones. 98 mgCOD/gSS, 343 mgCOD/gSS, and 500 mgCOD/gSS of polyhydroxyalkanoates (PHAs) per sludge unit were obtained at SRT-24d, 8d, and 2d, respectively, suggesting that the HiCS system is more advantageous for rapid PHAs production.

Effect of nitrogen- and oxygen-containing functional groups on adsorption of styrene by activated carbon: A theoretical study by density functional theory

Activated carbon adsorption is one of the mainstream technologies for controlling VOCs emissions such as styrene, with surface functional groups significantly influencing its adsorption capacity. The adsorption mechanism of styrene on functionalized AC was studied using DFT calculations. Results show that nitrogen and oxygen doping altered the local electrostatic potential of AC, reduced the average LOLIPOP index of the internal ring, and enhanced styrene adsorption to varying degrees. AC with hydroxyl and pyrrolic groups significantly improved styrene adsorption (Ead = -13.76, -12.86 kcal/mol). Styrene adsorption on AC is a physisorption process, primarily dominated by π-π stacking, with dispersion interactions as the main contributor (61–70 %). In addition to π-π stacking, weak hydrogen bonds between styrene and AC functionalized with hydroxyl, amino, and pyrrolic N groups further enhance the adsorption capacity. Enhancing the synergistic effect of hydrogen bonding and π-π stacking is key to significantly improving adsorption capacity.

Exploring Electrolyte Adsorption on the Different Types of Layered Cathode Surfaces in Lithium-Ion Batteries via a Universal Neural Network Potential Method.

LiNi x Mn y Co z O2 (NCM) is a promising cathode material for lithium-ion batteries. Their long-term stability and impedance growth as cycles are strongly influenced by the properties of the cathode electrolyte interface (CEI), formed by the reaction between the electrolyte and electrode surface. Understanding of these interactions at the atomic level of the NCM electrode surface and electrolyte will provide a new strategic approach for the design of a highly functional CEI layer. In this study, we explored the influence of Ni content in transition metal layers on surface energies under different synthetic conditions and terminations using a density functional theory (DFT) validated universal neural network potential (UNNP) method. Furthermore, we investigated the adsorption of ethylene carbonate (EC) and dimethyl carbonate (DMC) on the most favorable NCM surfaces. EC and DMC displayed similar adsorption energy trends; however, differences were observed in the preferred configurations, which can affect the formation of the CEI.

Oil removal using agricultural wastes adsorbents in a fixed bed column as a pretreatment in RO systems

Oil removal from seawater is an essential pre-treatment in Reverse Osmosis desalination plants to mitigate membrane fouling. The present paper investigates the feasibility of oil removal from water using agricultural wastes as low-cost adsorbents. Three wastes, rice husk, sugarcane bagasse, and sawdust were tested using two types of water, oily seawater and oily distilled water. For comparison, activated carbon adsorbent was included in the tests as a reference case. The experiments were conducted in a fixed bed column (10 cm diameter and 55 cm height), at an initial oil concentration of 1000, 3000, and 5000 mg/L, bed height of 10, 15, and 20 cm, and flow rate of 75, 145, and 290 mL/min. The parametric study indicated that the breakthrough time and the percentage of oil removal increased with the decrease in initial oil concentration and flow rate, but the breakthrough time increases with increasing the bed height. The oil removal percentage using rice husk was higher than sawdust and sugar cane bagasse and it was 18.9 % lower than that of activated carbon. Thus, rice husk can be a cheap alternative to activated carbon. The effect of oil type and water type was not significant. Additionally, the 50 % breakthrough time was 1388 min for activated carbon, 912 min for rice husk, 580 min for sawdust and 421 min for sugar cane bagasse. Assessing the dynamics models indicated that the non-linear forms of the Thomas, Bohart-Adams, and Yoon-and-Nelson kinetic models perform better than their linear forms, and the difference in performance among these models was not so big, i.e., any of these models can be used to predict the breakthrough curve.

Tailored microporous graphitic carbon adsorbents from the urea-assisted method for efficient selective gas adsorption and separation of CH4/N2 and CH4/H2

Currently, the adsorption and separation of methane (CH4) from CH4/N2 and CH4/H2 have attracted global attention as an essential technique for the utilization of unconventional natural gas and to meet energy demand. This technique completely relies on the adsorbent; the development of the adsorbent can achieve selective CH4 adsorption and separation. In this context, microporous graphitic carbon adsorbents were tailored using hydrothermal and calcination methods. The textural features of adsorbents were precisely tailored using a hydrothermal approach by optimizing the glucose-urea ratio, and they were then activated with the non-corrosive reagent K2CO3, which gives a specific pore structure that aids in performance. Adsorbents’ textural characteristics, such as surface area and porosity, were significantly influenced by the glucose-urea ratio, which plays an essential role in gas adsorption and separation. A series of tailored microporous graphitic carbon adsorbents named 0.5-HTAC, 1-HTAC, 1.5-HTAC, 2-HTAC, 1.5-HTAC-a, 1.5-HTAC-b, and 1.5-HTAC-c. Among them, 1.5-HTAC adsorbent displayed superior CH4 gas adsorption (36.86 cm3/g) and excellent selectivity of CH4/N2 (6.29) at room temperature, owing to its microporosity, good surface area, and morphological effect. Meanwhile, H2 gas adsorption was not detected at room temperature, indicating that the 1.5-HTAC adsorbent is extremely selective for CH4 gas. However, an additional study of H2 uptake performed at 77 K revealed excellent H2 adsorption of about 314.3 cm3/g. Furthermore, the 1.5-HTAC adsorbent exhibited a low heat of CH4 adsorption as well as impressive reversibility, indicating that it can be reused more effectively.

Solvent-free synthesis of highly dispersed zinc-doped porous carbons as efficient dibenzothiophene adsorbents

Designing efficient adsorbents for the deep removal of refractory dibenzothiophene (DBT) from fuel oil is vital for addressing environmental issues such as acid rain. Herein, zinc gluconate and urea-derived porous carbons SF-ZnNC-T (T represents the carbonization temperature) were synthesized without solvents. Through a temperature-controlled process of “melting the zinc gluconate and urea mixture, forming H-bonded polymers, and carbonizing the polymers,” the optimal carbon, SF-ZnNC-900, was obtained with a large surface area (2280 m2 g), highly dispersed Zn sites, and hierarchical pore structures. Consequently, SF-ZnNC-900 demonstrated significantly higher DBT adsorption capacity of 43.2 mg S g−1, compared to just 4.3 mg S g−1 for the precursor. It also demonstrated good reusability, a fast adsorption rate, and the ability for ultra-deep desulfurization. The superior DBT adsorption performance resulted from the evaporation of residual zinc species, which generated abundant mesopores that facilitated DBT transformation, as well as the formation of Zn-Nx sites that strengthened the host-guest interaction (ΔE = −1.466 eV). The solvent-free synthesized highly dispersed Zn-doped carbon shows great potential for producing sulfur-free fuel oil and for designing metal-loaded carbon adsorbents.

Preparation of hydrilla verticillata activated carbon adsorbent for remediation of wastewater containing the active metal chromium

Abstract This research aims to determine the capacity of Hydrilla Verticillata activated carbon adsorbent in absorbing the heavy metal chromium. The method used in making Hydrilla Verticillata activated carbon is by carbonization at a temperature of 3000C and chemically activated. Activated carbon was contacted with a solution of the heavy metal chromium with a concentration of 100 ppm with contact times of 15, 30, 45, 60, 90 and 120 minutes. The structure of hydrilla verticillata active carbon from the XRD results is graphite and BET BJH characterization data shows that activated carbon has a surface area of 53.143 m2/g, an average pore size of 0.2764 nm and a pore volume of 0.0789 cc/g. The SEM- Edx characterization results show that the size distribution is not homogeneous but forms agglomerations like plate particles consisting of slitted pores. Test results using AAS show that the ability of hydrilla verticillata activated carbon to remediate the heavy metal chromium based on contact time is around 47.35%, 46.77%, 49.08%, 54.85%, 61.30% and 69.69% and the adsorption capacity is around 13.94 mg/g.

Dodecylphosphonic acid for the separation of spodumene and albite: flotation behavior and adsorption mechanism

Spodumene is an important lithium-bearing mineral, that is associated with albite and difficult to separate because of their similar surface chemical properties. Traditional fatty acid collectors often have issues, such as poor selectivity or weak collector ability, and thus developing efficient spodumene collectors is essential. In this study, the phosphonic acid surfactant dodecylphosphonic acid (DDPA) was first used as a single collector for the flotation separation of spodumene and albite, showing good selectivity and collection performance. Then, separation and adsorption mechanisms were studied using various characterization methods, including diffuse reflectance infrared Fourier transform spectroscopy, total organic carbon adsorption measurements, X-ray photoelectron spectroscopy, and zeta potential tests. Flotation tests showed that the recovery for spodumene can reach approximately 80% through single-mineral flotation under the following conditions: activation without metal ion, neutral pulp pH of 6.5–7.0, and DDPA dosage of 4 × 10−4 mol/L. By contrast, the recovery of albite was only approximately 10%. The recovery for Li2O in the artificial mixed ore test was 75.03%, and the grade was 6.30%. The separation of spodumene and albite was due to the selective adsorption of DDPA on the surface of spodumene, and more DDPA were adsorbed on the surface of spodumene than on albite under the same conditions. Adsorption mechanism analysis indicated that Al and O on the mineral surface were the active sites for DDPA adsorption. Combined with the species distribution, DDPA existed in various forms in different aqueous environments, indicating that DDPA was mainly adsorbed onto the mineral surface through chemisorption and hydrogen bonding. In summary, DDPA can be used as an effective collector for spodumene.

Kinetic study of the simultaneous removal of ibuprofen, carbamazepine, sulfamethoxazole, and diclofenac from water using biochar and activated carbon adsorption, and TiO2 photocatalysis

The growing number of pharmaceuticals released into the environment poses a threat not only to the aquatic environment but also to human health. This work introduces a novel approach for the simultaneous analysis of four pharmaceuticals—ibuprofen, carbamazepine, sulfamethoxazole, and diclofenac—each with distinct chemical structures. The study explores the kinetic behavior of these compounds during their removal from water, employing biochar and activated carbon as adsorbents, as well as titanium dioxide (TiO2) for photocatalytic degradation. This utilizes two distinct approaches incorporating adsorption mechanisms. The concentrations of pharmaceuticals were simultaneously measured using High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD). In addition to adsorption, photocatalysis with varying dosages of TiO2 was investigated as an alternative method for pharmaceutical removal. The HPLC- DAD analysis enabled the simultaneous monitoring of all four pharmaceuticals in a single analysis. The Langmuir-Hinshelwood model was applied to the photocatalysis data to assess reaction kinetics. The results demonstrate the efficacy of both adsorption methods in removing pharmaceutical contaminants from water. Integrating both adsorption and photocatalysis experiments in one manuscript allows for a comprehensive evaluation of these methods' individual strengths in water treatment applications, providing insights into their combined potential for addressing pharmaceutical contamination in water resources. The calculated removal efficiencies, Langmuir-Hinshelwood kinetics, half-life values, and equilibrium adsorption capacities provide a comprehensive understanding of the efficiency and mechanisms involved in the removal processes, emphasizing the importance of addressing pharmaceutical contamination in water treatment strategies.

Cation-Doped Nanocarbons for Enhanced Perfluoroalkyl Substance Removal: Exotic Bottom-Up Solution Plasma Synthesis and Characterization.

Perfluorinated alkyl substances (PFAS), such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), are pervasive organic contaminants that are widespread in aquatic environments, posing significant health risks to humans and wildlife. Due to their persistent nature, urgent removal is necessary. Conventional adsorbents are inefficient at removing PFOS and PFOA, highlighting the need for alternative materials. Herein, we present a synthetic method for quaternary ammonium cation-doped carbon nanoparticles (QACNs) using a solution plasma process for the efficient removal of PFOS and PFOA. QACN is formed simultaneously through a one-step discharge of nonequilibrium plasma at the interface of benzene and pyridinium chloride. The resulting material exhibited a high surface electrical charge and enhanced hydrophilicity as well as an amorphous structure of a nonporous nature, involving nanoparticles with an undefined shape. The obtained adsorbent demonstrated high adsorption efficiency and stability, adsorbing 998.45 and 889.37 mg g-1 of PFOS and PFOA, respectively, exceeding the efficiencies of conventional carbon-based adsorbents (80.89-313.15 mg g-1). The adsorption performance was dependent on the adsorbent dosage, pH of the solution, and the coexisting ionic species. Adsorption studies, including adsorption kinetics, isotherms, and thermodynamics, revealed that PFOS and PFOA were chemisorbed to the QACN surface, forming multilayers endothermically and spontaneously. Experimental and computational analyses revealed that adsorption primarily occurs via electronic interactions between the PFAS active sites and the quaternary ammonium group in the carbon framework. The slightly lower adsorption potential of the PFOS and PFOA fluorocarbon chains on the adsorbent was elucidated. Furthermore, the dispersibility of the adsorbent in solution significantly affected the adsorption performance. These findings highlight the potential of the novel synthetic method proposed in this study, offering a pathway for the development of highly effective carbon adsorbents for environmental remediation.

In-depth analysis of natural organic matter fractions in drinking water treatment performance: Fate and role of humic substances in trihalomethanes formation potential

In this study we investigate the compositional changes in dissolved organic matter (DOM) fractions across diverse water sources and treatment processes in three Drinking Water Treatment Plants (DWTPs). High-Performance Size Exclusion Chromatography coupled with Diode Array Detection and Organic Carbon Detection (HPSEC-DAD-OCD) was employed to characterize DOM fractions, offering insights into treatment optimization. We examine bulk water parameters, DOM distributions, and the efficiency of treatment trains in reducing DOM fractions. Results reveal distinct DOM composition profiles in river-sourced versus reservoir-sourced waters, with implications for treatment processes. Coagulation, Granular Activated Carbon (GAC) adsorption, Electrodialysis Reversal (EDR), and Ion Exchange (IEX) were evaluated for their efficacy in removing DOM fractions. The analysis highlights the effectiveness of coagulation in reducing high molecular weight (MW) fractions, while GAC filtration targets lower MW fractions. EDR shows significant removal of anions and aromatics, while IEX demonstrates high removal efficiencies for removing humic substances (HS) fractions. Spectroscopic analysis further elucidates changes HS sub-fractions and their role in disinfection by-products (DBP) formation. To quantitatively assess the relationship between HS sub-fractions and trihalomethane formation potentials (THMFP), Pearson correlation analysis were conducted, unveiling robust associations between HS sub-fractions and THM-FP that can be predicted by surrogate parameters such as A254.

Synthetic and natural antibacterial carbon adsorbents for clinical nuclear waste management

Patients undergoing high-dose radioiodine ablation (RAI) therapy in Nuclear Medicine Department need to be isolated in a special designed ward for a few days. Large amount of clinical radioactive wastewater from patient body is produced during high-activity RAI therapy. The radioactive wastewater needs to store in a delay tank until the radioactivity decayed below acceptable limit before being discharged and indirectly limit the patient admission and treatment. This study is to propose an alternative antibacterial adsorbent for I-131 extraction from clinical radioactive wastewater at the nuclear medicine department using graphene oxide silver (GOAg) and bamboo activated carbon (BAC). The synthesised adsorbents and their sediments (filtered sample) were analysed using field emission scanning electron microscopy (FESEM) for morphological analysis and analysed using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and X-ray diffraction (XRD). XPS spectra for C 1s adsorbents show intensity peaks at 284.45 eV (C=C) and 285.3 eV (C–C) for GOAg and its sediments, and 284.35 eV (C–C), 287.00 eV (C=O), and 290.07 eV (π–π∗ transitions) for BAC and its sediments. FTIR spectra reveal various functional groups of adsorbents: C=C (1637.50772 cm−1), C=O (1340.48041 cm−1), and C–O–C (1031.88060 cm−1) for GOAg and its sediments, and C=C (1635.57897 cm−1), C–C (1257.54421 cm−1), and C–O (1188.10925 cm−1) for BAC and its sediments. XRD patterns exhibit peaks at 2θ = 27.82°, 29.39°, 32.24°, and 46.22°, which can be attributed to the (002) diffraction plane, (220) crystallographic plane, (111) plane of Ag2O, and (200) crystallographic plane, respectively, for GOAg and its sediments. Meanwhile, the peaks at 2θ = 26.56° and 42.41°, which correspond to (002) and (100) planes, respectively, for BAC and its sediments. The d-spacing and the crystallinity index of each adsorbent were also determined. The estimation of the remaining β− particles during the adsorption of I-131 was carried out using PHITS. The finding of this study is beneficial for alternative radionuclide extractions technique from clinical radioactive wastewater in nuclear medicine.

Unveiling the competitive mechanism between SO2 and PCDD/Fs on activated carbon adsorption

In municipal solid waste incineration (MSWI) plants, activated carbon (AC) adsorption is the key technique for eliminating Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from flue gases. This research thoroughly investigates the potential competitive adsorption between SO2 and PCDD/Fs and examines how adsorption at the center and the edge of the AC layer impacts the adsorption process. The findings show a decline in the removal efficiency of PCDD/Fs from 86.8 % to 84.2 % and further to 74.4 % when using SO2 pre-treated (AC-A3) and H2SO4-impregnated (AC-B2) activated carbon, respectively. Multiple characterization methods reveal that sulfur elements occupy active sites within the inner pores of the activated carbon, reducing the availability of its pore structure, particularly affecting microporous more than mesoporous structures. DFT calculations suggest that the π-π EDA effect facilitates the adsorption of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), whereas dispersion force drive SO2 adsorption. Comparisons among various oxygenated functional groups show that the organic acid anhydride (CO-CO) has better adsorption selectivity toward TCDD and less adsorption to SO2. This study provides a novel perspective on the adsorption mechanisms of PCDD/Fs on AC and the competitive dynamics of sulfur in the flue gas.

Unveiling bisphenol A toxicity: human health impacts and sustainable treatment strategies

Abstract Introduction The widespread presence of bisphenol-A (BPA) in consumer goods like water bottles and eyeglass frames raises serious concerns about the chemical’s ability to accumulate in human tissues. Molecular filtration and activated carbon adsorption are two of the many BPA treatment technologies that have emerged in response to these issues; both are essential in the removal or degradation of BPA from water sources and industrial effluents. Content To secure the long-term health and environmental advantages of BPA treatment approaches, sustainable development is essential. Both the efficient elimination or destruction of BPA and the reduction of the treatment operations’ impact on the environment are important components of a sustainable approach. Different search engines like Pub-Med, MEDLINE, Google Scholar and Scopus are used for these systematic reviews and analyzed accordingly. This can be accomplished by making treatment facilities more energy efficient and using environmentally friendly materials. Greener ways to deal with BPA pollution are on the horizon, thanks to innovative techniques like bioremediation and improved oxidation processes. Reducing dependence on conventional, resource-intensive procedures can be achieved by investigating the use of bio-based materials and natural adsorbents in treatment processes. Summary and Outlook This review article tackling the health and environmental concerns raised by BPA calls for an integrated strategy that incorporates sustainable development principles and technology progress. We can reduce the negative impacts of BPA contamination, improve environmental stewardship in the long run, and ensure human health by combining cutting-edge treatment technologies with sustainable behaviours.

Regeneration of conventional and emerging PFAS-selective anion exchange resins used to treat PFAS-contaminated waters

Anion exchange resins (AERs) have emerged as a promising separation technology to remediate PFAS-contaminated waters due to their improved selectivities and capacities in comparison to legacy activated carbon adsorbents. Presently, site managers choose between AER systems employing resins defined as being ‘regenerable’ with relatively low PFAS selectivity, and PFAS-selective resins that are marketed as ‘single-use’ media intended for disposal upon PFAS breakthrough. However, the potential for these highly-selective adsorbents to be regenerated and/or reused remains poorly characterized. This study presents a comprehensive evaluation of the efficacy of various regenerant solution constituents, mixtures, and operational considerations on the regenerability of both ‘regenerable’ and ‘PFAS-selective’ AERs that were loaded during a pilot treatment study of PFAS-contaminated groundwater. Batch screening of regenerant solution constituents found that both classes of resins may be effectively regenerated using combinations of salt brine and organic cosolvent, with high cosolvent fractions being necessary for PFAS-selective AERs. While neither brine-only nor solvent-only regenerant solutions led to effective PFAS desorption, the efficacy of regeneration with brine/cosolvent mixtures varied with salt type and cosolvent composition. Chloride salts outperformed sulfate and bicarbonate salts, cosolvent efficacy depended on the volume fraction and type used, and highly non-polar solutions led to optimal PFAS desorption. Continuous-flow regeneration experiments showed near-complete PFAS desorption from regenerable AERs using 10 bed volumes (BVs) of 70 % methanolic brine solutions, whereas PFAS-selective resins required more bed volumes (30) of brines with higher methanol content (90 %) or a more hydrophobic cosolvent (n-propanol); increasing regenerant empty-bed contact time had minimal effect on PFAS desorption. > 90 % methanol recovery from the resulting waste regenerant mixtures was accomplished with negligible PFAS contamination using distillation, leaving a minimal volume of a PFAS-concentrated still bottoms waste that may be further treated for PFAS destruction. Life cycle analyses revealed that groundwater treatment using PFAS-selective AERs operated in a regenerable mode have lower environmental impacts and costs than systems using conventional regenerable AERs, and lower treatment costs than systems operated using PFAS-selective resins in a single-use mode. Although counterintuitive, these findings stem from the fact that higher cosolvent requirements for regeneration of PFAS-selective resins lead to greater internal recycling of regenerant solutions and much lower volumes of residual waste still bottoms that require off-site incineration or disposal.

Etching physicochemical adsorption sites of biochar by steam for enhanced hydrogen storage

Enhancing the hydrogen storage capacity of carbon-based materials requires the precise synthesis of strong hydrogen adsorption sites. Consequently, this work suggests improving hydrogen storage capacity by employing H2O low-temperature etching technology. First, the simulation methods investigated the pore structure and oxygen-containing groups’ adsorption properties on hydrogen. The results showed that the oxygen-containing group could increase the adsorption energy of biochar on hydrogen, and the carboxyl group had the greatest effect. A suitable coupling of pores and oxygen-containing groups can improve the microporous region’s hydrogen storage capacity. Moreover, biochar may form a new ultra-microporous region (less than 0.5 nm) by etching it at 700 °C and 30 vol% H2O. After etching 90 min, the surface oxygen concentration remained stable at 14 at.%. In conjunction with results from mass spectrometry, we discovered that the process influencing pore growth was the heterogeneous interaction between CO and H2 to create CH4. At 25 ℃ and −196 ℃, the KSBC-30–60 showed superior hydrogen storage capacity compared to KSB. Its total adsorption capacity was 0.49 wt% and 5.28 wt%, respectively, and increased by 1.32 and 1.2 times. This study proposes a novel approach to improving hydrogen storage by etching porous carbon structures with H2O. The strategy has the potential for large-scale application and can be further utilized in the design and optimization of related carbon adsorbents.

Modified Cellulose-Based Waste for Enhanced Adsorption of Selected Heavy Metals from Wastewater.

Due to industrial growth and its impact on the environment, the increasing amount of industrial waste requires a comprehensive approach aligned with the principles of sustainable development. The main goals are not only to preserve natural resources but also to encourage innovation in the reuse of waste materials. In an attempt to reduce the problems regarding waste disposal and wastewater treatment in the textile industry, fibrous textile waste was used as a starting material to obtain carbon adsorbents for the removal of pollutants from wastewater. Waste cotton and mixed yarns, mainly consisting of polysaccharide cellulose, were hydrothermally carbonized and activated with KOH to convert them into efficient carbon adsorbents for heavy metal removal from water. Characterization of carbonized material showed that after activation, an increase in specific surface area (up to 872 m2/g) and content of surface oxygen groups (6.04 mmol/g) leads to a higher affinity towards heavy metal ions, especially lead ions, and high adsorption capacity of 19.98 mg/g obtained for activated cotton yarns. The results of this research represent a contribution to the reduction of waste materials by modifying them into adsorbents, while the regeneration of adsorbents is an example of the practical application of polysaccharide-based materials in the purification of wastewater containing various heavy metal ions.