Evaluation of the adsorption behavior of mixed perfluoroalkyl and polyfluoroalkyl substances onto granular activated carbon and styrene-divinylbenzene resins

Because of the remarkable chemical structure of perfluoroalkyl and polyfluoroalkyl substances (PFAS), as well as the complex conditions of water, selecting an appropriate adsorbent for treating PFAS is critical. Adsorption needs to be environmentally friendly, low cost, and consider the types of adsorbents that work well in mixed PFAS solutions. In the present study, we used mixed PFAS to estimate the PFAS activity. This research aimed to evaluate and compare the efficacy of the adsorption of PFAS from water using different adsorbents: granular activated carbon (GAC), IRA 910 (strong anion resin), and DOWEX MB-50 (mixed exchange resin). Batch adsorption isotherms and kinetic studies were performed for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and perfluorohexane sulfonic acid (PFHxS). Freundlich models consistently described the kinetic behavior with a high correlation coefficient (R² > 0.98). PFAS adsorption capacities on GAC and IRA910 were dependent on the chain length (PFOS > PFOA > PFHxS). The adsorption capacity of DOWEX MB-50 decreased because of the sulfonate effects (PFOS > PFHxS > PFOA). The rate constants (k₂) that represented the adsorption of PFAS on different adsorbents observed within 96 h were accurately determined by the pseudo-second-order (PSO) model. GAC achieved followed the relationship k₂(PFOS) > k₂(PFOA) > k₂(PFHxS). Furthermore, k₂ of IRA910 decreased in the order of k₂(PFOA) > k₂(PFOS) > k₂(PFHxS), implying that IRA910 promoted hydrophobicity more significantly on the adsorption of PFCAs than perfluoroalkane (-alkyl) sulfonic acids. The kinetics of DOWEX MB-50 revealed k₂(PFHxS) > k₂(PFOS) > k₂(PFOA) because gel-type resins like DOWEX MB-50 are more suitable for shorter-chain PFAS. Further investigation is needed to determine the effect of organic matter under natural conditions and evaluate adsorptive selection caused by operational complexities.     

Influence of groundwater conditions and co‐contaminants on sorption of perfluoroalkyl compounds on granular activated carbon

Per and polyfluoroalkyl substances (PFAS) are emerging and persistent organic pollutants that have been detected in many environmental media, humans, and wildlife. A common method to effectively remove PFAS from water is adsorption by activated carbon. Preliminary sorption experiments were conducted using five characterized Calgon Corporation coal‐based granular activated carbon (GAC; F100, F200, F816, F300, and F400), one coconut‐based GAC (CBC‐OLC 12 × 30), and one Jacobi Corporation coal‐based GAC (Omni‐G 12 × 40). Sorption of four representative PFAS onto each GAC was measured to select the most favorable carbon sources. F400 and CBC were chosen based on their performance in preliminary PFAS sorption experiments and contrasting properties. Freundlich and Langmuir isotherm models were developed for perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonate (PFOS) at an initial concentration of 1 mg/L. Sorption capacities were determined for PFOA and PFOS individually and in the mixture. Individual compounds showed higher sorption than when present in the mixture for both PFOA and PFOS. PFOS showed higher sorption than PFOA both individually and in the mixture and F400 showed higher sorption capacity than CBC. The presence of co‐contaminants (kerosene, trichloroethylene, and ethanol), and variations in groundwater conditions (pH, presence of anions, naturally occurring organic matter, and iron oxides) demonstrated limited impact on the sorption of PFAS onto GAC under the experimental conditions tested.     

Pore structure and adsorption properties of activated carbon prepared from granular molded waste paper

We have previously manufactured activated carbon using waste paper board, which was prepared by adding 8% phenol resin adhesive to torn waste newspaper and hot-pressing. In this study, the pretreatment process of the raw material was simplified; the waste paper was extruded to form granules. The activated carbon was manufactured by the carbon dioxide activation method using the granules as the raw material. The properties of the activated carbon were evaluated based on the pore structure, the iodine adsorption number, and the adsorption of toluene vapor in a sealed chamber. The activated carbon, which was manufactured at an activation temperature of 1100°C and a treatment time of 60min, exhibited a specific surface area of 1241m²/g and an iodine adsorption number of 1120mg/g. These results were similar to those obtained for two commercially available activated carbons. The extent of toluene vapor adsorption by this activated carbon was similar to that observed for the two commercial activated carbons over a period of 130min.     

Tailoring mesoporosity of poly(furfuryl alcohol)-based activated carbons and their ability to adsorb organic compounds from water

In this work it was shown that polymers can be recycled into a promising adsorbent for organic dyes and phenols waste removal. For this, a series of activated carbons (ACs) were produced from mixture of ferrocene or titanium acetylacetonate with poly(furfuryl alcohol) (PFA) by steam activation. The introduction of ferrocene as Fe precursor was found to be an efficient catalyst in mesoporosity development during carbonization and subsequent steam activation at 850 °C, whereas the polymer based only and titanium-doped ACs are typically microporous. The porous structure parameters were determined from nitrogen adsorption isotherms measured at 77 K. Scanning electron microscopy was applied to monitor the metal distribution of metal-loaded char and the surface morphology of activated carbons. The adsorption capacity was found to be dependent mainly on pore size distribution. In the case of phenol adsorption, the adsorption was defined by volume of pore with size 0.8–1.4 nm; whereas, for Congo red best fit was observed for volume of pore with size 2–5 nm.

     

Adsorption of SO2 and NO from incineration flue gas onto activated carbon fibers

Activated carbon fibers (ACFs) were used to remove SO(2) and NO from incineration flue gas. Three types of ACFs in their origin state and after pretreatment with HNO(3), NaOH, and KOH were investigated. The removal efficiencies of SO(2) and NO were determined experimentally at defined SO(2) and NO concentrations and at temperatures of 150, 200 and 260 degrees C. Experimental results indicated that the removal efficiencies of SO(2) and NO using the original ACFs were <56% and <27%, respectively. All ACFs modified with HNO(3), NaOH, and KOH solution could increase the removal efficiencies of SO(2) and NO. The mesopore volumes and functional groups of ACFs are important in determining the removal of SO(2) and NO. When the mesopore volumes of the ACFs are insufficient for removing SO(2) and NO, the functional groups on the ACFs are not important in determining the removal of SO(2) and NO. On the contrary, the effects of the functional groups on the removal of SO(2) and NO are more important than the mesopore volumes as the amount of mesopores on the ACFs is sufficient to remove SO(2) and NO. Moreover, the removal efficiencies of SO(2) and NO were greatest at 200 degrees C. When the inlet concentration of SO(2) increased to 600ppm, the removal efficiency of SO(2) increased slightly and the removal efficiency of NO decreased.     

Utilization of turkey manure as granular activated carbon: physical, chemical and adsorptive properties

The high availability of large quantities of turkey manure generated from turkey production makes it an attractive feedstock for carbon production. Pelletized samples of turkey litter and cake were converted to granular activated carbons (GACs) by steam activation. Water flow rate and activation time were changed to produce a range of activation conditions. The GACs were characterized for select physical (yield, surface area, bulk density, attrition), chemical (pH, surface charge) and adsorptive properties (copper ion uptake). Carbon physical and adsorptive properties were dependent on activation time and quantity of steam used as activant. Yields varied from 23% to 37%, surface area varied from 248 to 472 m(2)/g and copper ion adsorption varied from 0.72 to 1.86 mmol Cu(2+)/g carbon. Copper ion adsorption greatly exceeded the values for two commercial GACs. GACs from turkey litter and cake show considerable potential to remove metal ions from water.     

Biosorptive removal of Pb(II) and Cu(II) from wastewater using activated carbon from cassava peels

The ability of activated carbon from cassava peels to remove heavy metals like Cu(II) and Pb(II) from hospital wastewater was investigated. The study showed that a pH of 8 was the best for the sorption of both metal ions onto the biosorbent. The time-dependent experiments for the metal ions showed that the binding of the metal ions to the biomass was rapid and occurred within 20–120 min. Sorption efficiency increased with a rise in adsorbent dosage. It increased from 12 to 73 % for Pb(II) and 26 to 79 % for Cu(II) when the adsorbent dose increased from 2 to 12 g. An increase in temperature led to an increase in sorption for both metal ions. The Langmuir model showed that the biomass has a higher sorption capacity for Cu(II) than Pb(II), with q _m = 5.80 mg g^?1 for Pb(II) and 8.00 mg g^?1 for Cu(II). The Freundlich isotherm K _f was 1.4 for Pb(II) and 1.8 for Cu(II), indicating a preferential sorption of Cu(II) onto the biosorbent. Adsorption capacity was found to decrease with an increase in particle sizes. Sorption occurred by physical mechanisms and was mainly controlled by intraparticle diffusion.     

Regeneration performance of spent granular activated carbon for tertiary treatment of dyeing wastewater by Fenton reagent and hydrogen peroxide

Journal of Material Cycles and Waste Management - The efficacy of Fenton reagent and hydrogen peroxide for the regeneration of saturated granular activated carbon with biological effluent of dyeing...     

Removal of fluoride from water using aluminum-modified activated carbon prepared from khat (Catha edulis) stems

This study investigated the fluoride removal efficiency and adsorption of a low-cost adsorbent prepared using aluminum-modified activated carbon from khat (Catha edulis) in a batch-mode reactor. The operating factors, including pH, adsorbent dose, and fluoride initial concentration, were optimized using the Box Behnken design of response surface methodology. The correlation coefficient (R²) for the removal of fluoride was found to be 0.93, showing the validity of the developed quadratic model. The results showed that, under optimized conditions of an adsorbent dose of 2.47 g/L, an initial fluoride concentration of 2.1 mg/L, an initial pH 6.08, and 60 min, 90% fluoride reduction was achieved. Meanwhile, the adsorption isotherm and kinetics followed the Langmuir adsorption model and the Pseudo second model, respectively, with a monolayer adsorption capacity of 0.3065 mg/g. On the other hand, Fourier transform infrared spectroscopy and scanning electron microscopy analyses revealed the formation of major peaks of components such as hydroxyl and carboxylic acids. The same optimum treatment conditions (adsorbent dose of 2.47 g/L, initial pH 6.08, and treatment time of 60 min) managed to remove low initial fluoride concentrations of 3.67 and 4.33 mg/L from real groundwater by 72.84% and 70.37%, respectively. The modified adsorbent prepared in this study successfully treat the low fluoride concentration to a level recommended by WHO for drinking water.     

Production of hydrogen by steam gasification of dehydrochlorinated poly(vinyl chloride) or activated carbon in the presence of various alkali compounds

Steam gasification of dehydrochlorinated poly(vinyl chloride) (PVC) or activated carbon was carried out in the presence of various alkali compounds at 3.0 MPa and 560°C–660°C in a batch reactor or in a semi-batch reactor with a flow of nitrogen and steam. Hydrogen and sodium carbonate were the main products, and methane and carbon dioxide were the minor products. Yields of hydrogen were high in the presence of sodium hydroxide and potassium hydroxide. The acceleration effect of the alkali compounds on the gasification reaction was as follows: KOH > NaOH > Ca(OH)₂ > Na₂CO₃. The rate of gasification increased with increasing partial steam pressure and NaOH/C molar ratio. However, the rate became saturated at a molar ratio of NaOH/C greater than 2.0.     

Removal of ammoniacal nitrogen (N-NH3) from municipal solid waste leachate by using activated carbon and limestone.

The presence of ammoniacal nitrogen (N-NH3) in leachate is one of the problems normally faced by landfill operators. Slow leaching of wastes producing nitrogen and no significant mechanism for transformation of N-NH3 in the landfills causes a high concentration of ammoniacal nitrogen in leachate over a long period of time. A literature review showed that the removal of ammoniacal nitrogen from leachate was not well documented and to date, there were limited studies in Malaysia on this aspect, especially in adsorption treatment. The main objective of the present study was to investigate the suitability of activated carbon, limestone and a mixture of both materials as a filtering medium, in combination with other treatments capable of attenuating ammoniacal nitrogen which is present in significant quantity (between 429 and 1909 mg L(-1)) in one of the landfill sites in Malaysia. The results of the study show that about 40% of ammoniacal nitrogen with concentration of more than 1000 mg L(-1) could be removed either by activated carbon or a mixture of carbon with limestone at mixture ratio of 5:35. This result shows that limestone is potentially useful as a cost-effective medium to replace activated carbon for ammoniacal nitrogen removal at a considerably lower cost.     

Effects of functionality and textural characteristics on the removal of Cd(II) by ammoniated and chlorinated nanoporous activated carbon

Virgin activated carbon (VAC) was chemically activated by hydrochloric acid and aqueous ammonia to obtain different surface functionalities and nanopore distributions. The N-tailored AC (NAC) acquired by alkali treatment significantly enhanced the cadmium sorption capacity, while the Cl-tailored AC obtained by acidic modification decreased the sorption capacity compared with that of VAC. With increasing ammonia concentration in the basic treatment, the NAC surface area was increased with declining pore volume and diameter, which increased the adsorption capacity for Cd(II) removal. However, increasing HCl concentration in the acidic modification decreased the surface area, with increasing pore volume and diameter, which decreased the cadmium adsorption capacity. The basic treatment created more alkaline-rich sites such as nitrogen-containing functional groups, on the carbon surface, thereby improving cadmium removal efficiency. However, the acidic treatment generated a stronger acidic chemical structure and much more the formation of the acyl- and alkyl chloride groups that greatly inhibited the Cd(II) sorption capacity.     

Occupational hygiene in terms of volatile organic compounds (VOCs) and bioaerosols at two solid waste management plants in Finland

Factors affecting occupational hygiene were measured at the solid waste transferring plant at Hyvinkää and at the optic separation plant in Hämeenlinna. Measurements consisted of volatile organic compounds (VOCs) and bioaerosols including microbes, dust and endotoxins.The most abundant compounds in both of the plants were aliphatic and aromatic hydrocarbons, esters of carboxylic acids, ketones and terpenes. In terms of odour generation, the most important emissions were acetic acid, 2,3-butanedione, ethyl acetate, alpha-pinene and limonene due to their low threshold odour concentrations. At the optic waste separation plant, limonene occurred at the highest concentration of all single compounds of identified VOCs. The concentration of any single volatile organic compound did not exceed the occupational exposure limit (OEL) concentration. However, 2,3-butanedione as a health risk compound is discussed based on recent scientific findings linking it to lung disease.Microbe and dust concentrations were low at the waste transferring plant. Only endotoxin concentrations may cause health problems; the average concentration inside the plant was 425 EU/m³ which clearly exceeded the threshold value of 90 EU/m³. In the wheel loader cabin the endotoxin concentrations were below 1 EU/m³. High microbial and endotoxin concentrations were measured in the processing hall at the optic waste separation plant. The average concentration of endotoxins was found to be 10,980 EU/m³, a concentration which may cause health risks. Concentrations of viable fungi were quite high in few measurements in the control room. The most problematic factor was endotoxins whose average measured concentrations was 4853 EU/m³.     

Characterization and removal of dissolved organic matter (DOM) from landfill leachate rejected by nanofiltration

Dissolved organic matter (DOM) from wastewater rejected by nanofiltration from a landfill leachate treatment plant was fractionated into humic acid (HA), fulvic acid (FA) and hydrophilic (HyI) fractions. It was found that humic substances (HA and FA) composed 75% of the total dissolved organic carbon (DOC) concentration of the DOM, with an average molecular weight of about 1000 Da. Elemental analysis, infrared spectroscopy, UV-visible spectroscopy and acid-base titration observations showed that the HA and FA of the DOM exhibited lower fractions of condensed aromatic functional groups but larger fractions of acidic groups compared with other aquatic DOMs. The properties of HA and FA were similar, but HA exhibited more complete humification, while the HyI fraction had more acidic groups. An aminated polymeric adsorbent NDA-8 was used to adsorb the DOM in the wastewater along with primary coagulation. Results of bench-scale experiments indicated that the treatment process could effectively remove the DOM and heavy metals while desorption liquid was 10 times more condensed than raw wastewater. Results of desorption and reproducibility tests consolidated the strong application potential of this treatment process as an advanced landfill leachate treatment technology.     

Effect of temperature and organic nutrients on the biodegradation of linear alkylbenzene sulfonate (LAS) during the composting of anaerobically digested sludge from a wastewater treatment plant

Limits on the application of biosolids (anaerobically processed sludges from wastewater treatment plants) as fertilizers for the amendment of soil are becoming greater because of the accumulation of recalcitrant substances, making necessary the use of techniques that bring the concentration of xenobiotics to lower concentrations than those permitted. In general, the biosolids composting process is sufficient to reduce the usual concentration of linear alkylbenzene sulfonates (LAS) to low levels. In this work, an assessment is made on the effect of temperature in the capacity of enriched bacterial populations to biodegrade LAS, together with the influence that the available nutrients may have in the biodegradation of these compounds. The results show that the microbial metabolism of LAS was not observed in the thermophilic range. The optimum temperature for the biodegradation of LAS appears to be around 40 degrees C, this is, the lowest assayed here, and at this temperature the differences in the biodegradation of LAS among the nutritionally supplemented cultures are small.     

Assessment of chemical and biochemical stabilization of organic C in soils from the long-term experiments at Rothamsted (UK)

Biological and chemical stabilization of organic C was assessed in soils sampled from the long-term experiments at Rothamsted (UK), representing a wide range of carbon inputs and managements by extracting labile, non-humified organic matter (NH) and humic substances (HS). Four sequentially extracted humic substances fractions of soil organic matter (SOM) were extracted and characterized before and after a 215-day laboratory incubation at 25 degrees C from two arable soils, a woodland soil and an occasionally stubbed soil. The fractions corresponded to biochemically stabilised SOM extracted in 0.5M NaOH (free fulvic acids (FA) and humic acids (HA)) and chemically plus biochemically stabilised SOM extracted from the residue with 0.1M Na4P2O7 plus 0.1M NaOH (bound FA and HA). Our aim was to investigate the effects of chemical and biochemical stabilization on carbon sequestration. The non-humic to humic (NH/H) C ratio separated the soils into two distinct groups: arable soils (unless fertilised with farmyard manure) had an NH/H C ratio between 1.05 and 0.71, about twice that of the other soils (0.51-0.26). During incubation a slow, but detectable, decrease in the NH/H C ratio occurred in soils of C input equivalent or lower to 4Mgha(-1)y(-1), whereas the ratio remained practically constant in the other soils. Before incubation the free to bound humic C ratio increased linearly (R2=0.91) with C inputs in the soils from the Broadbalk experiment and decreased during incubation, showing that biochemical stabilization is less effective than chemical stabilization in preserving humic C. Changes in delta13C and delta15N after incubation were confined to the free FA fractions. The delta13C of free FA increased by 1.48 and 0.80 per thousand, respectively, in the stubbed and woodland soils, indicating a progressive biological transformation. On the contrary, a decrease was observed for the bound FA of both soils. Concomitantly, a Deltadelta15N of up to +3.52 per thousand was measured after incubation in the free FA fraction and a -2.58 Deltadelta15N in the bound FA. These changes, which occurred during soil incubation in the absence of C inputs, indicate that free FA fractions were utilised by soil microorganisms, and bound FA were decomposed and replaced, in part, by newly synthesized FA. The 13CPMAS-TOSS NMR spectra of free HA extracted before and after 215 days of incubation were mostly unchanged. In contrast, changes were evident in bound HA and showed an increase in aromatic C after incubation.