Adsorption Capacity Of Granular Activated Carbon Research Articles

Electrochemical regeneration of carbendazim-loaded granular activated carbon

ABSTRACT This study explores the use of in situ electrochemical process to regenerate granular activated carbon (GAC) loaded with carbendazim (CBZ) and simultaneously oxidize the contaminant. The experiment optimized the flow rate ( Q ), current density ( j ), cathodic or anodic chamber, and electrolyte type to achieve the best results. The study found that using GAC in the cathodic chamber and NaCl as a supporting electrolyte, with a j = 0.5 mA cm−2, and Q = 100 L h−1, led to a 64% regeneration with an energy consumption of 0.15 kWh kg−1, which is at least 16× lower than those found in the literature for electrochemical, microwave and thermal processes. Consecutive regeneration tests revealed a decrease in GAC adsorptive capacity over time due to blockage by transformation products, and mainly by oxidation-induced changes in pore structure, as confirmed in dissolved organic carbon (DOC), scanning electron microscopy (SEM), and surface area results. The results also showed that in all tested conditions, residual CBZ was not found in the electrolyte solution. Overall, electrochemical regeneration proved to be an energy-efficient method for extending the lifespan of GAC and minimizing disposal in landfills.

Biodegradable dissolved organic carbon profiling reveals capacity of carbon‐based potable reuse treatment over a range of operating conditions

AbstractBiological treatment is gaining ground as a means to enhance removal of total organic carbon (TOC) as part of a multi‐barrier treatment train for water reuse. Here we applied biodegradable dissolved organic carbon (BDOC) analysis to evaluate the extent of removal of various TOC fractions through a pilot‐scale water reuse train employing flocculation/sedimentation, ozone, biologically active carbon (BAC), and granular activated carbon (GAC). BDOC analysis highlighted GAC and ozone treatments as critical to non‐biodegradable dissolved organic carbon removal and the need to optimize BAC performance to maximize GAC adsorption capacity. BDOC analysis was further applied to benchmark process performance to operational conditions, such as empty bed contact time (EBCT), occurrence of nitrification, and operational upsets. The lower EBCT proved to be less resilient to nonideal conditions. Overall, BDOC analysis proved an asset for understanding and improving operation of ozone/BAC/GAC treatments for water reuse.

Adsorption of Toxic Tetracycline, Thiamphenicol and Sulfamethoxazole by a Granular Activated Carbon (GAC) under Different Conditions.

Activated carbon can be applied to the treatment of wastewater loading with different types of pollutants. In this paper, a kind of activated carbon in granular form (GAC) was utilized to eliminate antibiotics from an aqueous solution, in which Tetracycline (TC), Thiamphenicol (THI), and Sulfamethoxazole (SMZ) were selected as the testing pollutants. The specific surface area, total pore volume, and micropore volume of GAC were 1059.011 m2/g, 0.625 cm3/g, and 0.488 cm3/g, respectively. The sorption capacity of GAC towards TC, THI, and SMZ was evaluated based on the adsorption kinetics and isotherm. It was found that the pseudo-second-order kinetic model described the sorption of TC, THI, and SMZ on GAC better than the pseudo-first-order kinetic model. According to the Langmuir isotherm model, the maximum adsorption capacity of GAC towards TC, THI, and SMZ was calculated to be 17.02, 30.40, and 26.77 mg/g, respectively. Thermodynamic parameters of ΔG0, ΔS0, and ΔH0 were obtained, indicating that all the sorptions were spontaneous and exothermic in nature. These results provided a knowledge base on using activated carbon to remove TC, THI, and SMZ from water.

GAC Adsorption of Dissolved Organic Matters for CSOs Treatment and Bioregeneration of Spent-GAC Using Denitrification

The capability of a laboratory-scale reactor packed with granular activated carbon (GAC) was evaluated in the removal process of organic matter dissolved in Combined Sewer Overflows (CSOs). First, the capacity of adsorption was recorded by six types of organic matter passing through the GAC reactor. Second, the breakthrough period was investigated when the CODcr adsorption ratio fell below 30% by varying the input intensity of CODcr into the GAC reactor from high, medium, to low. Lastly, the possibility of regenerating GAC through the denitrification process was examined. As a result, GAC adsorption capacity was ranked in order of sewage > sodium acetate > methanol > LB broth ≒ Glucose. Uniquely, glucose, being easily removed in the biological wastewater treatment process, had a low GAC adsorption capacity in this process. Thus, GAC showed the best adsorption for sewage among tested organic matters. Secondly, the breakthrough periods of the GAC adsorption reactor were 21, 28, and 32 days under high, medium, and low CODcr conditions, respectively. Lastly, the organic matter adsorbed in the GAC micro-pore was reused as an external organic carbon source to denitrifying bacteria in CSOs. However, the re-adsorption capacity was not at a satisfactory level which needs further research.

Removal of pharmaceutical compounds from synthetic hydrolysed urine using granular activated carbon: Column study and predictive modelling

Human urine contains high concentration of pharmaceuticals, a concern that must be addressed if used as a fertiliser. This study systematically evaluated granular activated carbon (GAC) adsorption in removing five most commonly found pharmaceuticals in the environment – naproxen (NAP), carbamazepine (CBZ), ibuprofen (IBP), acetaminophen (APAP) and metronidazole (MTZ) from hydrolysed urine. Fixed-bed column experiments were conducted to obtain breakthrough curves and assess GAC (1000 m2g−1) performance in the adsorption of pharmaceuticals at different adsorbent mass (4–12 g·L−1), flow rate (1.15–4.32 L·d−1) and adsorption/contact time at ambient room temperature and pH 9. The highest adsorption capacity was observed at a lower adsorbent mass (4 g·L−1) and lower flow rate (1.15 L·d−1) for all micropollutants. The breakthrough curves showed the highest GAC adsorption capacity for CBZ (56.1 mg·g−1) while MTZ (32.2 mg·g−1) with the lowest adsorption will be the design limiting for column adsorption application. Thomas and Yoon-Nelson models fitted well for predicting empirical breakthrough curves for fixed-bed GAC column adsorption. The artificial neural network (ANN) modelling was able to predict the removal effectiveness of over 99% except for APAP at 84.5%. The study showed that the potential application of GAC column adsorption for micropollutant removal is significant although this study was limited in the range of parameters studied.

Enhanced removal of per- and polyfluoroalkyl substances in complex matrices by polyDADMAC-coated regenerable granular activated carbon

Granular activated carbon (GAC) has been used to remove per- and polyfluoroalkyl substances (PFASs) from industrial or AFFF-impacted waters, but its effectiveness can be low because adsorption of short-chained PFASs is ineffective and its sites are exhausted rapidly by co-contaminants. To increase adsorption of anionic PFASs on GAC by electrostatic attractions, we modified GAC's surface with the cationic polymer poly diallyldimethylammonium chloride (polyDADMAC) and tested its capacity in complex water matrices containing dissolved salts and humic acid. Amending with concentrations of polyDADMAC as low as 0.00025% enhanced GAC's adsorption capacity for PFASs, even in the presence of competing ions. This suggests that electrostatic interactions with polyDADMAC's quaternary ammonium functional groups helped bind organic and inorganic ions as well as the headgroup of short-chain PFASs, allowing more overall PFAS removal by GAC. Evaluating the effect of polymer dose is important because excessive addition can block pores and reduce overall PFAS removal rather than increase it. To decrease the waste associated with this adsorption strategy by making the adsorbent viable for more than one saturation cycle, a regeneration method is proposed which uses low-power ultrasound to enhance the desorption of PFASs from the polyDADMAC-GAC with minimum disruption to the adsorbent's structure. Re-modification with the polymer after sonication resulted in a negligible decrease in the sorbent's capacity over four saturation rounds. These results support consideration of polyDADMAC-modified GAC as an effective regenerable adsorbent for ex-situ concentration step of both short and long-chain PFASs from real waters with high concentrations of competing ions and low PFAS loads.

Adsorption isotherms and kinetics for the removal of algal organic matter by granular activated carbon

Seasonal algal blooms in surface water release a significant amount of algal organic matter (AOM), which alters the composition of dissolved organic matter (DOM). AOM affects the drinking water treatment processes and finished water quality. In this study, the relative removal efficiency of AOM and humic acid by granular activated carbon (GAC) adsorption was determined. Batch experiments were conducted to evaluate the adsorption capacity of GAC, which varied from 4.235–31.45 mg/g for AOM originated from different algae. Freundlich isotherm models fitted the adsorption equilibrium data, and the adsorption kinetics data were fitted well using a pseudo-second order kinetic model. The calculated thermodynamics parameters (∆G0, ∆H0 and ∆S0) indicated that GAC adsorption for DOM removal was endothermic and spontaneous in nature.

Adsorption of Salicylic Acid from Aqueous Solutions on Microporous Granular Activated Carbon

The kinetics of adsorption of salicylic acid from aqueous solutions on microporous granular activated carbon (GAC) was studied. The high adsorption capacity of GAC for this substance was shown. The order of adsorption of salicylic acid and the activation energy of adsorption were determined.

Melamine degradation to bioregenerate granular activated carbon

The industrial chemical melamine is often detected in surface water used for drinking water production, due to its wide application and insufficient removal in conventional wastewater treatment plants. Melamine can be removed from water by adsorption onto granular activated carbon (GAC), nevertheless, GAC needs periodic reactivation in costly and energy intense processes. As an alternative method, GAC can also be regenerated using biomass capable of degrading melamine in a process called bioregeneration. We assessed melamine biodegradation in batch experiments in fully oxic and anoxic, as well as in alternating oxic and anoxic conditions. Additionally, we studied the effect of an additional carbon source on the biodegradation. The most favourable conditions for melamine biodegradation were applied to bioregenerate GAC loaded with melamine. We demonstrate that melamine can be biodegraded in either oxic or anoxic conditions and that melamine degrading biomass can restore at least 28% of the original GAC adsorption capacity. Furthermore, our results indicate that bioregeneration occurs mainly in the largest pore fraction of GAC, impacting adsorption kinetics. Overall, we show that bioregeneration has a large potential for restoring GAC adsorption capacity in industrial wastewater.

Optimization of the adsorption of diclofenac by activated carbon and the acidic regeneration of spent activated carbon

Diclofenac sodium (DCF) is a non-steroidal anti-inflammatory drug. It has been classified as ecotoxic even at low concentrations. In this study, adsorption of DCF on coconut shell-based granular activated carbon (GAC) and regeneration of spent GAC with hydrochloric acid (HCl) were investigated. The results showed that GAC with heterogeneous surface structure adsorbs DCF endothermically with both chemical and physical forces. Adsorption and regeneration processes were optimized with Taguchi Experimental Design. The effects of all parameters affecting the adsorption and regeneration processes were determined by analysis of variance and Pareto analyses. DCF removal of 79.80% was obtained at optimum conditions and the most effective parameter was evaluated as GAC size. At optimum regeneration conditions, 6.85 mg DCF/g GAC adsorption capacity was found with an operating cost of €0.05 g GAC. The amount of HCl was the most effective parameter. It was determined that the regenerated GAC had an adsorptive capacity higher than the adsorptive capacity of the raw GAC during at least three regeneration cycles. Raw, spent and regenerated GACs were characterized by Fourier transform infrared spectrometry and scanning electron microscopy analysis.

Biochar and GAC intensify anaerobic phenol degradation via distinctive adsorption and conductive properties

The roles of biochar and granular activated carbon (GAC) in the enhancement of anaerobic phenol degradation were characterized through batch tests conducted at different phenol concentrations, coupled with adsorption kinetics, microbial community, and in-situ electrochemical analysis. Both biochar and GAC (15 g/L) led to markedly shorter lag times (t0) by adsorbing dissolved phenol, and faster maximum CH4 production rate (Rmax) by triggering direct interspecies electron transfer (DIET) during a two-stage (adsorption then degradation) anaerobic phenol degradation. The high adsorption capacity of GAC helped achieve a shorter t0, but less affected Rmax of subsequent phenol degradation. Compared with GAC, which showed higher conductivity but no redox activity, biochar exhibited higher electron exchange capacity (6.57 μmol e−/g). This higher electron exchange capacity stemmed from the diverse redox-active moieties, which resulted in a more efficient DIET. Meanwhile, the formation of wire-like appendages which linked the enriched DIET partners (such as Syntrophorhabdus and Methanosaeta) on biochar probably futher enhanced the electron transfer. However, hydrogenotrophic methanogenesis was still the main pathway for syntrophic phenol degradation in the suspended sludge. The in-situ analysis also confirmed that biochar and GAC acted as geobatteries and geoconductors, respectively, and that the stimulation of DIET was persistent.

Pilot-scale combined adsorption columns using activated carbon and zeolite for hazardous trace elements removal from wastewater of entrained-flow coal gasification

When entrained-flow gasification technology is applied on a large scale, the release of hazardous trace elements (HTEs) from the use of coal in gasification poses a potential threat to environmental and human health. An adsorption method combining granular activated carbon (GAC) and zeolite as adsorbents to remove the HTEs is proposed. A pilot-scale experiment proved that this method can effectively remove HTEs, especially, the removal rate for mercury and beryllium achieved 99%. Additionally, adsorption studies using GACs were conducted through laboratory batch experiments employing several kinetic and isotherm models. The results show favorable levels of mercury, arsenic, and beryllium adsorption by GAC. GAC derived from low rank bituminous coal has the good comprehensive adsorption performance of HTEs. Langmuir presented the best fit of arsenic and beryllium adsorption, and Freundlich presented the best fit of mercury. The kinetics studies showed that experimental data follow Pseudo-second order. Zeolite’s capacity for ion exchange greatly affects its adsorption performance, which supplements the adsorption capacity of GAC for metal and metalloid ions. This study provides an approach that is fast, and easily integrates with existing processes for removing HTEs in entrained-flow coal gasification wastewater.

Enhancement of the adsorption of hexacyanoferrate (III) ion on granular activated carbon by the addition of cations: A promissory application to mining wastewater treatment

The influence of the addition of cations on the adsorption of [Fe(CN)6]3− on granular activated carbon (GAC) was evaluated. The tests were performed at three pH values (3, 8.2, and 13) to determine the repulsion or electrostatic affinity between the adsorbent and adsorbate. Afterward, the cations (K+, Ca2+, and Al3+) at three pollutant-cation molar ratios (1:1, 1:10, and 1:50) were added to the system, and the influence of those was identified by the changes in the adsorption efficiency. The results show that the higher removal (%) was obtained at pH 13 without neither the presence of iron precipitates nor the liberation of HCN. The adsorption of [Fe(CN)6]3- was enhanced by the addition of K+ at 1:10 and 1:50 mol ratio since higher removals were achieved (75.27 % and 76.81 % respectively) than those obtained in the absence of cations (64.18 %) or in the presence of Ca2+ (67.58 %) and Al3+ (65.13 %) at a 1:10 mol ratio. The behavior in adsorption in the presence of cations shows that the ion-pair adsorption mechanism can describe the physical phenomenon, showing an increase in the fraction removed and the rate of adsorption with increasing cation charge. The adsorption kinetics using K+ with a 1:10 pollutant-cation molar ratio was fitted to the Lagergren pseudo-first-order model. The GAC adsorption capacity describes the pollutant adsorption rate with the predominance of physical interactions. The experimental data were fitted by the Langmuir and Freundlich isotherms, indicating a monolayer adsorption phenomenon consistent with the previously proposed ion-pair adsorption mechanism.

Removal of chlorhexidine gluconate in presence of a cationic surfactant using acid functionalized activated carbon: Validation of multicomponent models

Abstract Commercial antiseptic solutions containing a mixture of antibacterial agents such as, chlorhexidine gluconate, in presence of a cationic surfactant like cetrimide, are commonly used as floor, toilet and kitchen cleaning agents. Although a specific composition may be beneficial for disinfecting human beings, these are toxic to aquatic organisms, the plant biota and useful microorganisms present in soil and in municipal sewer pipes. In this study, functional modification of granular activated carbon (GAC) is carried out with hydrochloric and hydrofluoric acids in order to enhance the adsorption capacity of GAC for simultaneous removal of both chlorhexidine gluconate and cetrimide. Hydrofluoric acid functionalized activated carbon shows highest removal of both cetrimide and chlorhexidine gluconate (maximum adsorption capacitypure component chlorhexidine gluconate =349.0 g/g; maximum adsorption capacitypure component cetrimide =23.0 g/g). Average removal of cetrimide by GAC, FAC-HCl and FAC-HF are 36.64 %, 47.09 % and 75.74 % respectively. Surface charge of modified activated carbons is significantly altered as compared to unmodified GAC which provided an enhanced net available driving potential for the positive cetrimonium ions to reach the surface much faster as compared to the bulky chlorhexidine gluconate molecules. Cetrimide then undergoes pure physical adsorption through pore diffusion. However, chlorhexidine gluconate forms surface complexes with the functional groups as confirmed by the relative quantities of oxygenated surface functional groups and Fourier Transform Infrared (FT-IR) analysis. Intraparticle diffusion and Boyd plots show that film diffusion and not intraparticle diffusion is the rate controlling step.

Biodegradation and adsorption of micropollutants by biological activated carbon from a drinking water production plant

The presence of micropollutants in surface water is a potential threat for the production of high quality and safe drinking water. Adsorption of micropollutants onto granular activated carbon (GAC) in fixed-bed filters is often applied as a polishing step in the production of drinking water. Activated carbon can act as a carrier material for biofilm, hence biodegradation can be an additional removal mechanism for micropollutants in GAC filters. To assess the potential of biofilm to biodegrade micropollutants, it is necessary to distinguish adsorption from biodegradation as a removal mechanism. We performed experiments at 5 °C and 20 °C with biologically active and autoclaved GAC to assess the biodegradation of micropollutants by the biofilm grown on the GAC surface. Ten micropollutants were selected as model compounds. Three of them, iopromide, iopamidol and metformin, were biodegraded by the GAC biofilm. Additionally, we observed that temperature can increase or decrease adsorption, depending on the micropollutant studied. Finally, we compared the adsorption capacity of GAC used for more than 100,000 bed volumes and fresh GAC. We demonstrated that used GAC shows a higher adsorption capacity for guanylurea, metformin and hexamethylenetetramine and only a limited reduction in adsorption capacity for diclofenac and benzotriazole compared to fresh GAC.

Adsorption of 2,4-Dichlorophenoxyacetic Acid on Granular Activated Carbon

The adsorption of a typical herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), from its aqueous solution on granular activated carbon (GAC) was studied. The kinetics of adsorption of 2,4-D on GAC and its porosimetric characteristics and microstructure were studied. A high adsorption capacity of GAC for 2,4-D was found.

Removal of THM Precursors by Adsorption, Coagulation and UV Irradation

The general characteristics of humic substances (HS) and their negative effect on water quality and its treatment are described. The paper presents the results from the removal of humic substances from the Hriňová (Slovakia) water reservoir using 1) granular activated carbon (GAC) from two producers (Chemviron, Cabot) at three different pH levels, 2) by coagulation with two coagulants (aluminum sulfate and ferric sulfate), and 3) by an advanced oxidation process using UV radiation with the addition of the oxidizing agent hydrogen peroxide. The effectiveness of the removal of humic substances (expressed by the TOC parameter) from water with adsorption by GAC, depending on the contact time with the water, ranged from 14 % for one hour to 50% for eight hours of contact time. The calculated GAC adsorption capacity of the humic substances ranged from 0.05 mg/g for one hour to 0.19 mg/g for eight hours of contact time. The pH of the water had no significant effect on the level of efficiency. A high level of efficiency (50%) and the lowest value of TOC are obtained at a pH of 6.5. The humic substances remain in the water though the optimal dose of the coagulant was used. The ferric sulfate coagulant is more suitable for removing of humic substances from water as aluminum sulfate. A dose of 16 mg/L of 1% solution Fe2(SO4)3, which is the equivalent of 4.47 mg/L Fe3+, is sufficient for the reduction of humic substances below 1 mg/L. The effectiveness of the removal of humic substances with coagulation using iron sulfate was 83% for a parameter of HS and 50% for TOC or CODMn. The iron sulfate has the influence on a reduction in pH of water, therefore pH of water should be adjusted after coagulation. A laboratory study of removal of humic acids from surface water by UV radiation and addition of hydrogen peroxide in order to increase the oxidation of organics are presented. The results showed that UV radiation and addition of H2O2 during the first few minutes of irradiation increases the concentration of the humic substances, CODMn and TOC in water. After 3 minutes of exposure to UV radiation, these values were reduced to baseline, and in the next irradiation phase the values of the monitored parameters decreased. The highly reactive OH radicals with a high oxidation potential oxidize humic substances to various intermediates (a lower molecular weight substances). After 20 minutes of irradiation, a decrease in the parameters of approx. 39% for TOC, 62% for CODMn and 37% for humic substances was observed.

A comparison study of granular activated carbon modification by FeCl3 under the acidic and basic condition for arsenic removal from water

The present study deals with the effect of two different conditions for modification of raw granular activated carbon (GAC) with FeCl3 under acidic granular activated carbon (AGAC) and basic granular activated carbon (BGAC) conditions for removal of arsenic As(V) from aqueous solution. X-ray diffraction, scanning electron microscopy, and Brunauer Emmett Teller (BET) were used for structural properties. Obtained images show that for raw GAC most of the peaks are related to SiO2 and graphite, but, for AGAC related to Fe2O3, Fe3O4, and SiO2, and for BGAC related to Fe3O4 and hydrogen aluminum silicate. Surface area and total pore volume of raw GAC > AGAC > BGAC. Kinetics study for arsenic removal by raw GAC and BGAC obeyed pseudo-first-order model, but, AGAC obeyed pseudo-second-order model. Isotherm study showed that raw GAC has a good fit with Langmuir model, and AGAC and BGAC have a good fit with Freundlich model. The adsorption capacity of AGAC, BGAC, and raw GAC (As(V) concentration = 0.3 mg/L) was 22.7, 18.33, and 14.35 mg/g, respectively. It was concluded that modified raw GAC under the acidic condition had better than basic condition.

Alkaline functionalization of granular activated carbon for the removal of Volatile Organo Sulphur Compounds (VOSCs) generated in Sewage Treatment Plants

Adsorption, using Granular Activated Carbon (GAC), is an effective technique for the removal of mal-odorous Volatile Organo Sulphur Compounds (VOSCs) originating from sewage waste water collected from various Sewage Treatment Plants (STPs). Adsorption capacity of GAC is enhanced by functionalization with various alkaline solution. Alkali functionalized activated carbons (FACs), having higher surface area and pore volume and reduction of oxygen containing functional groups, perform much better in removing VOSCs in comparison to precursor GAC. Different adsorbed odorants (VOSCs), being concentrated and in close proximity to each other on the surface or in the pores of the adsorbent, may interact. The adsorption capacity of GAC and FACs increases in the order FAC-NH3 > FAC-KOH > FAC-NaOH > GAC. FAC-NaOH or FAC-KOH may react with ambient CO2 thereby forming carbonates. This effectively decreases the removal efficiency. Odour concentration is measured simultaneously by two techniques: panel olfactometry (sensory measurement based) and component specific analytical measurement (GC–MS based). Time variant olfactometry based odour concentration data correlated well with the time variant concentration of VOSCs (GC–MS based) for all four malodorous compounds like methyl mercaptan, ethyl mercaptan, dimethyl sulphide and carbon disulphide. Linearization of the percentage removal of overall odour (olfactometry based) versus percentage removal of relative concentrations of the four VOSCs reveals that methyl mercaptan has a very large odour contributing potential (R2 = 0.967) representing the most obnoxious component of the tested sewage waste water as compared to other three compounds. Simultaneous conversion of methyl mercaptan to dimethyl disulphide leads to its faster removal by FAC-NH3.

Regeneration of granular activated carbon loaded with toluene – Comparison of microwave and conductive heating at the same active powers

This paper presents a comparison of the microwave and conductive heating regeneration of granular activated carbon loaded with toluene at the same active powers. The purpose of this research was to compare desorption efficiencies and local temperature profiles for the both regeneration methods. Mass balance in the adsorbent bed was carried out by automatic sampling of the outlet gas for the GC analysis instead of weighting the adsorbent bed itself. Five experimental series were performed at constant active power of 12W and at changing active power in the two-stage program (24W+12W). It was found that the mass profiles of desorbed toluene versus time were practically overlapped for the two regeneration methods when the same active power was applied and the non-insulated vessels were used. Moreover, another comparison demonstrated that proper thermal insulation can be a decisive factor when choosing a particular regeneration method in terms of its economic viability. A comparison of the textural properties of the fresh and regenerated (after 10 successive adsorption/desorption cycles) granular activated carbon (GAC) revealed only slight differences between them. Therefore, it was concluded that the adsorption capacity of GAC is only slightly affected by the both regeneration methods.