Activated Carbon Adsorption Research Articles

The Effectiveness of Active Carbon Adsorbent of Cassava Peel (Manihot Esculenta Cranzts) in Reduce Level of Chromium Metal in Tannery Liquid Waste

This study aims to determine the characteristics, the effect of mass variation, the percentage of adsorption effectiveness of cassava peel activated carbon activated with 0.5 M HCl and activated with 0.5 M H2SO4 on the adsorption of Cr metal in leather tanning wastewater and its morphology. The subject of this research is the adsorbent of cassava peel before it is asctivated, activated by chloric acid 0,5 M, and activated by sulfuric acid 0,5 M. meanwhile the object of this research is the effectiviness of cassava peel adsorbeny in reduscing chromium metal content in tannery liquid waste. Cassava pell was carbonized at 500 oC for 1 hour. The cassava peel carbon was characterized according to SNI 06-3730-1995. The adsorption process is performed by batch method. Analysis was performed by Atomic Adsorption Spectrophotometer, PSA, and SEM-EDX. The result of the characterization of cassava peel carbon showed that the moisture content, ash content, adsorption capacity of I2 met SNI, meanwhile the carbon contenr and volatile matter conten did not met SNI. The adsorption efficiency of kromium metal is 95.97% for carbon before activated, 95.33% for carbon activated by chloroc acid, and 96.65% for carbon activated by sulfuric acid. The result of PSA size of cassava peel adsorbent before activated by chloric acid and sulfuric acid were 34.484 µm, 42.504 µm, and 37.059 µm respectively. Cassave peel adsorbent has a Langmuir adsorption type. The SEM-EDX result showed that the adsorbent from cassava peel had a dissimiliar pore shape

Evaluation of Preparation and Detoxification of Hemicellulose Hydrolysate for Improved Xylitol Production from Quinoa Straw.

Quinoa straw is rich in hemicellulose, and it could be hydrolyzed into xylose. It is a promising energy resource alternative that acts as a potential low-cost material for producing xylitol. In this study, quinoa straw was used as a substrate subjected to the hydrolysis of dilute sulfuric acid solution. Based on the production of xylose and inhibitors during hydrolysis, the optimal conditions for the hydrolysis of hemicellulose in quinoa straw were determined. Detoxification was performed via activated carbon adsorption. The optimal detoxification conditions were determined on the basis of major inhibitor concentrations in the hydrolysate. When the addition of activated carbon was 3% at 30 °C for 40 min, the removal of formic acid, acetic acid, furfural, and 5-HMF could reach 66.52%, 64.54%, 88.31%, and 89.44%, respectively. In addition to activated carbon adsorption, vacuum evaporation was further conducted to perform two-step detoxification. Subsequently, the detoxified hydrolysate was used for xylitol fermentation. The yield of xylitol reached 0.50 g/g after 96 h of fermentation by Candida tropicalis (CICC 1779). It is 1.2-fold higher than that obtained through the sole vacuum evaporation method. This study validated the feasibility of xylitol production from quinoa straw via a biorefinery process.

Synergistic and Antagonistic Effects of the Co-Pyrolysis of Plastics and Corn Stover to Produce Char and Activated Carbon.

The physicochemical properties of char and activated carbon produced from the co-pyrolysis of corn stover (CS) and plastics, polystyrene (PS) and polyethylene terephthalate (PET), were studied. Non-isothermal gas analysis of the volatiles was conducted using an online mass spectrometer to correlate the thermal degradation of gaseous byproducts to the formation of pores in the char materials. The findings determined that the addition of PS or PET promotes the formation of the solid char product with either higher than average pore sizes or surface areas compared to control samples. The addition of PET to corn stover increases the surface area of the char formed. The char formed from a CS:PET mass ratio of 1:1 produced char with a surface area of 423.8 ± 24.8 m2/g at 500 °C and a duration of 2 h. The surface area of the chars formed from CS and PET decreased as the amount of PET decreased, showing a tendency for PET to increase the surface area of the char materials synergistically. The addition of PS to corn stover promoted the formation of chars with, on average, larger pore sizes than the control char samples. The chars were chemically activated with potassium hydroxide, and the activated carbon that formed had lower surface areas but comparable surface functional groups to the control samples. Vanillin adsorption testing showed that activated carbon from corn stover performed the best at removing 95% of the vanillin after 2 h. In contrast, the activated carbon from the chars produced from the co-pyrolysis of corn stover and polystyrene or corn stover and polyethylene terephthalate removed 45% and 46% of vanillin after 2 h, respectively. The findings suggest that plastics have a synergistic relationship in producing char precursors with improved porosity but antagonistically affect the activated carbon adsorbent properties.

Water-soluble carbon nitride as phase-convertible adsorbents for removing heavy metals from water

Current adsorption technologies suffer from inferior interfacial mass transfer and slow reaction rates of heterogeneous adsorbents for water decontamination. By far, it remains challenging to explore a solid material with homogeneous dispersion for reusable applications. Herein, we present a proof-of-concept demonstration of using water-soluble carbon nitride (w-C3N4) as a phase-convertible adsorbent, which will combine the advantages of homogeneous adsorption and heterogeneous separation. The w-C3N4 with various hydrophilic and cyano groups exhibit a high Pb2+ adsorption capacity of 302.3 mg/L, together with fast adsorption kinetics, which is much better than bulk g-C3N4 and activated carbon adsorbents. After the adsorption reaction, the soluble adsorbents can be easily separated from water by increasing the ionic strength of the homogeneous solution, which can be effectively regenerated by diluted acid. The creative integration of homogeneous and heterogeneous processes provides a new avenue for breaking through the limits in host–guest interactions of current adsorption technologies by reversible phase conversion.

Adsorption of Chromium (VI) Using an Activated Carbon Derived from Petroleum Coke Feedstock

This study aims to determine the main adsorption mechanism by which chromium (VI) is adsorbed onto the surface of a petroleum-coke sourced activated carbon, a feedstock not prevalent in current literature. The study also aims to produce an activated carbon adsorbent that is both cost-effective and efficient for the removal of chromium (VI) in neutral waters. The efficacy of thermally-treated petroleum coke-activated carbon and nitrogenated petroleum coke-activated carbon using ammonium chloride is compared to the efficacy of commercially available activated carbon. X-ray photoelectron spectroscopy of the activated carbons was obtained both before and after exposure to chromium (VI) for characterization of the materials and confirmation of chromium adsorption. The thermally-treated and nitrogenated activated carbons showed significant enhancement of chromium (VI) removal compared to the non-treated petroleum coke-activated carbon (22.4 mg/g, 21.9 mg/g, and 17.0 mg/g, respectively). However, there was no significant difference observed between the thermally-treated and nitrogenated materials. This indicates that the nitrogenation of the surface does not improve the adsorption capacity of the activated carbon, but rather the thermal treatment itself. X-ray photoelectron spectroscopy showed a significant increase in the alcohol functional groups on the surface of the activated carbon material as a result of the heat-treatment process; from 16.02 atomic percent in the non-treated activated carbon to 26.3 atomic percent in the thermally-treated activated carbon. The alcohol functional groups present on the surface allow for chromium (VI) to undergo reduction to chromium (III) under a similar mechanism to the well-known Jones Oxidation Reaction where the reduced chromium (III) species are then physisorbed to the surface of the activated carbon. XPS results are consistent with this as the chromium species present on the surface of the adsorbent is primarily Cr(OH)3 (85.6% in the standard AC and 82.5% in the thermally-treated AC). Pseudo-first-order and pseudo-second-order kinetic modeling of the adsorbents indicate that they follow a pseudo-second-order reaction where the rate-limiting step is the chemical sorption of the adsorbate itself.

Removal of Pb(II) ion by activated carbon synthesised from Musa Acuminate stem waste: surface properties, kinetics, adsorption mechanism, and reusability

ABSTRACT We present the synthesis of Activated Carbon (AC) by pyrolysis of Banana (Musa Acuminate) Stem Waste (BSW), and the ability of obtained AC for adsorptive removal of Pb(II) ions from water. Importantly, pyrolysis was performed at 750°C for 2.0 h in the presence of high surface area producing chemical activators such as NaOH, LiOH, H3PO4, ZnCl2, and KOH. BET-surface areas of AC produced with activators NaOH, LiOH, H3PO4, ZnCl2, and KOH were determined to be 908, 1531, 1670, 2245, and 2485 m2 g−1, respectively. Pore volume ascending order was determined as 0.59 (NaOH) < 0.68 (LiOH) < 0.86 (H3PO4) < 0.97 (ZnCl2) <1.18 (KOH) cm3 g−1. SEM and TEM images revealed the porous nature of the ACs. ACs produced with H3PO4, ZnCl2, and KOH exhibit type I adsorption isotherms, indicating their microporous nature. ACs prepared with NaOH and LiOH exhibit type II adsorption isotherms, indicating their macroporous nature. X-ray diffraction, X-Ray photoelectron, and Raman spectroscopy analysis revealed the graphitic structure of ACs. Pb(II) ion adsorption onto ACs surface obeyed the Langmuir model. It was found that the Pb(II) adsorption capacities of the ACs produced with NaOH, LiOH, H3PO4, ZnCl2, and KOH as the chemical activators were 220, 283, 326, 329, and 435 mg g−1, respectively, at the optimised conditions (pH = 6.6, contact time = 100 min, [ACs] = 0.125 g L−1, at 30°C). The interaction between surface functional groups of ACs and Pb(II) ions was confirmed by X-Ray photoelectron and FT-Infrared spectroscopy. The negative values of ΔGo and ΔHo reveal that the Pb(II) ion adsorption onto the ACs surface is spontaneous and exothermic. The Pb(II) ion adsorption capacity increased with an increase in BET-SA and pore volume of ACs, with AC obtained from BSW with KOH exhibiting the highest adsorption capacity of 435 mg g−1. Thus, the study highlights BSW, agricultural biomass waste is a low-cost and abundantly available carbon precursor to synthesise potential AC adsorbent for water treatment.

Sequential combination of pre-chlorination and powdered activated carbon adsorption on iodine removal and I-THMs control in drinking water

Combining pre-oxidation with activated carbon adsorption was explored as an ideal approach for removing iodine from water source to eliminate the formation of Iodinated trihalomethanes (I-THMs). Compared with permanganate and monochloramine, chlorine is more suitable as pre-oxidant to obtain higher active iodine species (HOI/I2). Active iodine species adsorption using both powdered activated carbon (PAC) and granular activated carbon (GAC) can be well fitted the pseudo-second-order kinetic model indicating that chemical adsorption was the dominant mechanism for HOI/I2 adsorption. The average pore size of activated carbons was the most strongly correlated with the adsorption capacity (R2 > 0.98), followed by methylene blue (R2 > 0.76), pore volume (R2 > 0.70) and iodine number (R2 > 0.67). Moreover, three models, including intraparticle diffusion, Byod kinetic, and diffusion-chemisorption were used to illustrate the mechanisms of HOI/I2 adsorption. Chemical adsorption was the dominant mechanism for HOI/I2 adsorption. In summary, at the molar ratio of [NaClO] and [I−] as 1.2, pre-chloriantion time of 5 min, subsequently dosage of 15 mg/L of PAC E with 20 min adsorption can remove 79.8% iodine. In addition, the combined process can eliminate 61%–87.2% of I-THMs in the subsequent chlor(am)ination. The results indicate that pre-chlorination combined with PAC can effectively removed HOI/I2 and attenuate I-THMs formation in the subsequent disinfection process.

Activated carbon from melamine-impregnated paper

Activated carbon was prepared from waste melamine-impregnated paper (MIP) by pyrolysis with activation by NaOH. The adsorption parameters such as carbonization temperature (300, 350, 400, 450 °C), NaOH to C ratio (2:1, 3:1, 4:1, 5:1), and initial methylene blue (MB) dye concentration (20 to 600 mg/L) were studied. The adsorption results were fit by the Langmuir isotherm model and pseudo-second order kinetics. It was found that the activated carbon from MIP had a maximum adsorption capacity of 497 mg/g at 400 °C (carbonization temperature) and NaOH to C ratio (2:1). The highest removal of methylene blue (MB) via activated carbon was 99.4%. The π-π interaction between dye molecules and MIP active carbon was proposed to be a primary driving force for dye adsorption. This activated carbon adsorbent based on MIP was shown to be highly promising for water decontamination applications.

Recent progress in the combination of activated carbon adsorption and electrolysis for the treatment of wastes

This work describes the recent progress in the development of processes that combine activated carbon adsorption and electrolysis. Three different approaches were identified, and their recent progress and innovations are described. The first approach consists of the use of activated carbon as electrode and adsorbent simultaneously, either in monopolar or bipolar connection, to retain and oxidize directly pollutants on its surface. In the second approach, activated carbon does not act as an electrode, but merely provides heterogeneous catalytic sites for the destruction of pollutants with electrochemically produced oxidants. Finally, in the third approach, activated carbon is used in a two-phase process, first acting as an adsorbent to retain pollutants contained in a gaseous or aqueous stream and then releasing them into a methanol solution that is electrochemically regenerated in a second phase. Possible applications are also discussed not only for the treatment of liquid wastes, but also for gaseous polluted streams. • Several possibilities of combining electrolysis and adsorption for removal of pollutants. • Technology applicable to liquid and gaseous polluted streams. • Activated carbon as simultaneous adsorbent/electrode. • Activated carbon as heterogeneous catalysts for electrogenerated oxidants. • Activated carbon regenerated with methanol that in turn is electrochemically regenerated.

A Novel Method for Removal of Iron Ion Contamination in Patchouli Essential Oil

Nowadays, in the aromatic and cosmetics industries, as well as an additive for food flavoring, patchouli essential oil (PEO) is a significantly crucial raw material. This oil is extracted from Pogostemon cablin, a plant from the Lamiaceae family. The standard method to obtain this oil is steam distillation. However, applying this method, the oil has a relatively high iron content. A contaminated iron ion can arise in the PEO for some reasons, i.e., the distillation practice used in a non-stainless steel tank, the PEO stored in an iron drum, or even the water for steam production was not appropriately treated. Activated carbon adsorbents can be used to remove contaminants from liquids or gasses by adsorbing ions, complexes, and molecules from aqueous solutions. Although fine adsorbent particles offer advantages in terms of adsorption capacity and kinetics, the application of the adsorbent to remove iron ions contaminated in PEO is not simple work. It is because a problem with these particles is widely dispersed in the oil and challenging to recover and contaminates the final product of PEO. This study developed a novel method to remove iron ions contaminated in a PEO using a modified activated carbon, i.e., magnetic activated carbon (MAC). For practical applications, using MAC material will reduce operating costs and solve the problems related to the quality of the end product, i.e., contamination by the adsorbent. The result shows that the MAC material improved the quality of PEO by reducing iron ion concentration in the oil from the initial concentration of 194 mg/L to around 87 mg/L. As expected, the adsorbent allows rapid removal from the PEO by using a magnetic source. Based on this study, MAC material enables the reduction of iron ion contamination in PEO and produces a free-adsorbent in the final product.

The properties of electric double layer at activated carbon surface and their effect on gold and silver adsorption from cyanide solutions

This paper looks at the properties of electric double layer (EDL) found at the surface of activated carbons. The study relied on the electrical conductivity method, which is based on simultaneous use of polarization dependences at direct current and conductometric measurements at alternating current. It was found that the adsorption of gold and silver intensifies in the anode region of carbon surface polarization. Two regions with peak adsorption were identified in the following ranges of potentials: +0.2&divide;+0.25 and +0.6&divide;+0.8 V. EDL diffusion helps improve the environment for the adsorption of cyanide complexes of gold and silver by active centres of the adsorbent surface. The authors believe that an increased mass transfer in the first range of potentials can be attributed to a decreased diffusion resistance caused by changed zero charge polarity, while in the second range of potentials it can be attributed to the cyan-ion oxidation reaction and an easier access of the negatively charged cyanide complexes of gold and silver to the positively charged surface of the carbon adsorbent. The polarization dependences by direct current in the anode region tend to monotonously rise, which is indicative of a lower EDL density, an increased conductivity at the adsorbent surface/solution boundary and improved adsorption conditions. Graphs showing a relationship between alternating current and carbon adsorbent potential helped determine maximum conducti vity values, which almost match the peak values of gold and silver adsorption. The authors established that the adsorbent&rsquo;s potential has a significant effect on the activated carbon adsorption of cyanide complexes of gold and silver. The use of the electrical conductivity method for examining the EDL helps explain certain features typical of the activated carbon adsorption of gold and silver from cyanide solutions.

Efficient Purification of 2′-Fucosyllactose by Membrane Filtration and Activated Carbon Adsorption

With the rapid development of synthetic biology, the production of 2′-fucosyllactose by biological fermentation gradually has the basis for industrialization. However, the lack of efficient downstream technology of biological fermentation, especially purification technology, has become the main factor limiting its commercialization. In this study, based on the general E. coli biosynthesis of 2′-fucosyllactose fermentation broth, most of the impurities were removed and concentrated using membrane filtration technology after simple flocculation. The target 2′-fucosyllactose was eluted in a targeted manner using activated carbon adsorption and ethanol gradient elution technology. The 2′-fucosyllactose product with 90% or even higher purity could be prepared efficiently. This study explored a new direction for the industrial production of 2′-fucosyllactose.

Study on the influence of sampling methods for measuring soil radon exhalation rates

Soil is the primary source of radon in the atmosphere, and soil radon exhalation rate (E) is a key indicator to evaluate the radon hazard in soil. Radon can also be used as a tracer to analyze atmospheric processes and monitor greenhouse gas emissions. Therefore, improving the accuracy of measuring E is significant for radon protection and radon pollution management as well as public health. In this study, three different sampling methods were compared to determine the most suitable sampling method for E measurement under different conditions. The results indicated that the closed-loop gas-flow method can be used to measure E and required correction for leakage and counterdiffusion; E was found to vary from 13.25 ± 1.44 to 30.46 ± 2.19 mBq·m−2 s−1. For the open-loop gas-flow method, a low sampling flow rate was selected, and the sampling flow rate derived from this experiment was less than 0.2 l min−1; E varied from 36.11 ± 0.99 to 52.67 ± 1.68 mBq·m−2 s−1. For the activated-carbon adsorption method, the counterdiffusion effect had a negligible influence on the measurement results, and the measurement error due to the uneven distribution of radon in the carbon layer could be eliminated by changing the waiting time for the measurement; the measurement showed E of about 23 mBq·m−2 s−1. Moreover, the influence of water absorption of the activated carbon on the measurement results should be considered, and the water absorption rate should be less than 9%. The obtained values will serve as a reference for the rapid and accurate measurement of E.

Reed Rhizome Residue-Based Activated Carbon Adsorption Ultrafiltration Membranes for Enhanced MB Removal.

Novel adsorption ultrafiltration (ADUF) membrane was designed for the removal of methylene blue (MB) by introducing Chinese herbal waste-based activated carbon (AC) into the ultrafiltration membrane. We prepared AC particles from Chinese herbal medicine waste residue (reed rhizome residue) as a raw material by ZnCl2 activation and introduced them into the ultrafiltration membrane by phase inversion to prepare a reed rhizome residue-based activated carbon adsorption ultrafiltration (RAC-ADUF) membrane. The RAC-ADUF-0.1 membrane was characterized by a series of physical structures and chemical properties, which showed that the prepared membrane has a more hydrophilic surface and high porosity. The RAC-ADUF-0.1 membrane showed an excellent pure water flux of 255.77 L·m-2·h-1 and a high bovine serum albumin rejection of 99.3%. The RAC-ADUF membranes also possessed excellent antifouling performance. Notably, the RAC-ADUF-0.1 membrane provides excellent removal of MB (99% retention) compared to conventional ultrafiltration membranes. The static adsorption capacity was up to 238.48 mg/g. The significant increase in dynamic adsorption capacity on the RAC-ADUF membrane is due to the three-dimensional distribution of RAC particles on the PSF membrane cross section, which provides more active sites and increases the contact time between RAC and MB. By fitting the adsorption kinetics and isothermal adsorption curves, the results showed that the pseudo-second-order kinetic model and the Langmuir isothermal model were more accurate in explaining the adsorption process. Further kinetic analysis showed that the adsorption process of MB molecules on RAC-ADUF membranes is controlled by both external mass transfer and intraparticle diffusion, with intraparticle diffusion playing a dominant role. In addition, the RAC-ADUF membrane exhibited outstanding adsorption and regeneration abilities, and the MB removal rate stayed at about 95% after 8 adsorption regeneration experiments. In conclusion, this study provides a new idea for the preparation strategy of an adsorption ultrafiltration membrane with high rejection and high permeability and the reuse of Chinese herbal medicine waste residue.

Effect of granular activated carbon adsorption and size of microbial aggregates in inoculum on stimulating direct interspecies electron transfer during anaerobic digestion of fat, oil, and grease

To investigate the effect of granular activated carbon (GAC) adsorption and size of microbial aggregates in inoculum on stimulating direct interspecies electron transfer (DIET) during anaerobic digestion of fat, oil, and grease (FOG), seed sludge was divided into two inocula (big (>0.85 mm)/small (0.15–0.85 mm)) for FOG digestion with/without GAC. More long-chain fatty acids (LCFAs) were adsorbed on GAC in the reactor with small aggregates than that with big aggregates, corresponding to 57 % and 10 % decreased methane production, respectively. Adsorption of unsaturated LCFAs (e.g., oleic acid) on GAC was found to reduce LCFA bioavailability, hinder DIET via GAC, and change community structure. Compared to pre-adsorption of oleic acid on GAC, pre-attachment of microbes on GAC resulted in 5.6-fold higher methane yield for oleic acid digestion. Together, competition of LCFA adsorption between GAC and microbial aggregates is essential for enhanced methane recovery from FOG digestion via GAC-induced DIET.

A Process for removing toxic heavy metals to produce the high purity NH4H2PO4 and KH2PO4 from a crude phosphoric acid

The use of chemical fertiliser, in particular a phosphate, in the agricultural sector is an essential in a modern production of crops. However, low grade fertilisers containing toxic heavy metals could be accumulated in soil and introduced into our food chain eventually. For sustainability, it is important to use the high purity fertilisers in the agricultural sector. In this context, we propose a hydrometallurgical process to remove impurities, including toxic heavy metals, to produce the high purity monoammonium phosphate (MAP) and monopotassium phosphate (MKP) from a crude phosphoric acid (approx. 50% P2O2). The proposed process is incorporated with a series of precipitations, ion exchange, activated carbon adsorption, and evaporating to crystallise the final product. All impurities in final products were removed by over 90% and controlled under marketable specifications. As and Cr were removed further below to less than 1 mg/L in the final solution for adjusting the capacity of carbon was identified. Optimised conditions identified were then utilised in 40 L size pilot-scale reactors and produced the high purity MAP and MKP, respectively. The proposed process is expected to contribute for producing the high purity MAP and MKP by relatively simple technique and cost-effective than a conventional solvent extraction process from the crude phosphoric acid. The use of high purity phosphate fertilisers can aid sustainability for the agricultural industry by reducing accumulating the toxic heavy metals in soil in a wide sense.

Study on treatment of city tail water by constructed wetland with corn straw biochar substrate

Constructed wetland (CW) has obvious advantages in city tail water treatment. The biochar preparation from corn straw is an effective measure for improving the straw utilization. In order to improve the pollutant removal rate of CW, the city tail water treatment based on straw biochar substrate was studied. The thermogravimetric experiment of straw, characteristics test (scanning electron microscope, pore structure, element, adsorption) of biochar and city tail water treatment experiment by CW was carried out. The results show that the carbon fixation rate of straw biochar prepared at 450 °C (10 °C ⋅ min −1 , 2 h, N 2 ) was 67.72%, and the adsorption capacity of biochar exceeded 40% of the requirements of wood activated carbon adsorption standard. When the proportion of biochar in substrate was 2.95%, the mean removal rates of ammonia nitrogen, total nitrogen and nitrate nitrogen was more than 85%. This study will be conducive to reducing straw carbon emissions and improve CW technical level. • The carbon fixation rate of biochar prepared at 450 °C (10 °C ⋅ min −1 , 2 h,) was 67.72% • The adsorption of straw biochar for NH4+-N was greater than that of TP and NO3–N • Elovich equation was good to simulate the dynamic adsorption of NH4+-N, NO3–N and TP • The nitrogen removal rate was over 85% when the mass ratio of biochar was 2.95% in CW.

Migration and diffusion of unsteady-state flow of volatile organic compounds on activated carbon adsorption beds under reverse ventilation

Despite increasing attention to the influence of unsteady-state volatile organic compounds (VOCs) on the adsorption of activated carbon, studies in this regard are rare. Therefore, in this study, an investigation into the migration and diffusion of unsteady-state VOCs on activated carbon adsorption beds under reverse ventilation was conducted. Here, reverse clean air was introduced when the activated carbon bed reached the penetration point. The influence of reverse ventilation temperature, reverse superficial gas velocity, activated carbon filling height, and different ventilation modes on the adsorption of unsteady toluene by activated carbon were studied. Our experimental results show that when the reverse ventilation temperature increased from 20 °C to 60 °C, the quasi-first-order desorption rate constant increased from 0.00356 min−1 to 0.00807 min−1, an increase in the reverse superficial gas velocity led to a higher rate constant, and at greater reverse superficial gas velocities, the stripping capacity increased. It was observed that the maximum stripping capacity was achieved at a reverse superficial gas velocity of 0.3 m/s. For different activated carbon filling heights, following reverse ventilation, the stripping capacity of a 5 cm and 30 cm activated carbon bed accounted for 41.43% and 65.85% of the original adsorption capacity, respectively. The study concludes that concentration of toluene first increased and then decreased with time under forward ventilation, whereas the concentration gradually decreased under reverse ventilation.

Removal of algae and algogenic odor compounds via combined pre-chlorination and powdered activated carbon adsorption for source water pretreatment

This study investigated the combination sequence and time interval of chlorination and powdered activated carbon (PAC) adsorption for the control of algae inactivation, algogenic odor removal, and disinfection by-product (DBP) formation. Results indicated that pre-chlorination/post-PAC exhibited the highest algae removal efficiency in all sequential combinations of PAC adsorption and chlorination, while it had displayed slight effect on the removal of DBPs. The evaluated sequential combinations all had significant effect on the removal of odor. Nevertheless, prolonged time interval between chlorination and PAC adsorption exhibited enhanced control of algae and odor compounds in all experiments; with increasing time interval from 0 to 15 min in pre-chlorination/post-PAC process, the removal efficiency of Chl-a, algal cell viability, GSM, and 2-MIB increased by 46%, 15%, 15% and 23%, respectively. In the combined processes, the odor removal efficiency was positively correlated with PAC dosage but negatively correlated with chlorine dosage. Furthermore, PAC addition could effectively reduce the total DBP yields, especially the N-DBPs. This study can provide a better understanding of improving in-situ operation of the pre-chlorination and PAC dosing systems for source water pretreatment.

Performance of TSA and VSA post-combustion CO2 capture processes with a biomass waste-based adsorbent

Carbon capture in post-combustion flue gases is vital on the grounds that most of the energy requirement of the world is supplied by non-renewable energy sources. Biomass-based CO2 adsorbents are of interest due to their high potential of adsorption capacity and contribution to the sustainable circular economy. In the current study, Temperature Swing Adsorption (TSA) and Vacuum Swing Adsorption (VSA) configurations were carried out to evaluate the CO2 capture performance of a hazelnut shell-based activated carbon adsorbent from dry simulated flue gases in cyclic operation. A fixed-bed reactor with a single column is used to test the adsorption performance for CO2 concentrations of 14% and 30% and temperatures of 30 °C and 50 °C at atmospheric pressure, which resemble the conditions of industrial processes. Various TSA and VSA configurations are designed and the influence of cyclic steps on the product (CO2) purity, recovery, productivity, and specific energy consumption at different CO2 concentration and temperature are evaluated. For the VSA process, the highest purity and recovery obtained are 92% and 100%, respectively; while they are 86% and 82% for TSA process, revealing the highest TSA cycle CO2 adsorption performance of a biomass-based adsorbent reported in literature.