Carbonaceous Adsorbents Research Articles

Removal of copper ions from wastewater by adsorption onto a green adsorbent from winemaking wastes

Copper ion adsorption was studied using an activated carbon from winemaking wastes. The pH, temperature, activated carbon amount, and initial copper concentration were varied based on a full factorial 2k experimental design. Kinetic and thermodynamic studies were also performed. The adsorption kinetics followed a pseudo-second-order model. The adsorption data fit best to the Langmuir isotherm, compared with the Freundlich and Temkin models. The analysis of variance demonstrated that the pH and the activated carbon dosage had the greatest influences on the copper adsorption. The obtained activation energy suggested that the copper adsorption was physisorption. The best fit to a linear correlation was the moving boundary equation, which controls the kinetics of the adsorption of copper ions onto the activated carbon. X-ray photoelectron spectroscopy revealed the existence of different copper species (Cu2+, and Cu+ and/or Cu0) on the surface of the carbonaceous adsorbent after the adsorption, which could suggest a simultaneous reduction process.

The role of the oxygen functional groups in adsorption of copper (II) on carbon surface

The effect of carbon surface oxidation on the adsorption of Cu(II) ions from aqueous solution was studied in order to explain the role of the oxygen functional groups in the binding of copper ions. Pristine carbonaceous adsorbent was oxidized to a various extent of oxygen uptake (Fenton-like oxidation < persulphate in H2SO4 < H2O2 in HNO3). Equilibrium adsorption tests were performed in acetate buffer at pH ≈ 5. The results show that the adsorption capacity of pristine adsorbent is expectable low (~0.1 mmol g−1). The oxidized samples adsorb Cu(II) at a considerably higher level of ~1.4 mmol g−1 despite the degree of surface oxidation. Analysis of the surface groups (FTIR, TPD) and surface charge (zeta potential) of used adsorbents and their Cu(II) saturated counterpart lead to the finding that Cu(II) ions are mostly bonded by complexation with the dissociated carboxylic groups (partly formed by anhydrides hydrolysis) probably in the form of Cu(Ac)+ formed in the acetate buffer. The extent of dissociation is given by equilibrium pH during the adsorption and does not depend on the total amount of the surface groups. Thus, the content of active sites and consequently adsorption capacity is independent on the degree of oxidation when pH is kept constant. The results indicate that even moderate oxidation treatment of carbonaceous materials can produce highly effective adsorbents for Cu(II) immobilization.

Valorizing Waste Bamboo Tar to Novel Bead Carbonaceous Adsorbent for Volatile Organic Compound Removal

AbstractActivated phenol-formaldehyde (PF) beads were successfully synthesized using waste bamboo tar as the raw material via suspension polymerization method and adequate carbonization and activat...

Highly Effective Removal of Tetracycline from Water by Hierarchical Porous Carbon: Batch and Column Adsorption

To improve the removal efficiency of pharmaceutical antibiotics from water by adsorption technologies, it is vital to optimize the porous geometrical structure of carbonaceous adsorbents. In this study, a hierarchical porous carbon that possesses micro/meso bimodal pores (MMC) is synthesized and is employed in the adsorption of tetracycline in both batch mode and column mode. In comparison, microporous carbon, mesoporous carbon, and commercial activated carbon (AC) are induced as carbonaceous adsorbents. In batch mode adsorption, the maximum adsorbed amount of tetracycline on MMC reaches 701.31 mg/g, which is twice as much as that on AC. While in the column adsorption process, the treatment capacity and the total adsorbed amount of MMC toward tetracycline are found 10 times greater than those of AC. The porous geometrical structure of the adsorbent is revealed to play an important role in determining the adsorption efficiency in the column adsorption process with a limited contact time. The surface utiliz...

Conversion of lignocellulosic agricultural wastes into adsorbents for pharmaceutical drugs

Lignocellulosic agricultural wastes e.g. corn cobs, straws and corn stalks were converted into carbonaceous adsorbents using a sequence of thermal and chemical activation processes. The derived solids obtained after each type of activation were characterized by determination of fix carbon content, iodine number, Boehm titration and DRIFT spectrometry. The results obtained at the adsorption tests were well correlated to those of the characterization, showing that the most promising adsorbents for amoxicillin removal were those submitted to a thermal treatment followed by a chemical alkaline activation, followed by washing and a secondary thermal treatment. The most promising bio-based adsorbent was the one derived from corn stalks (90.6% adsorption efficiency).

Recent advances in carbon-based renewable adsorbent for selective carbon dioxide capture and separation-A review

Abstract In terms of net intensification in the greenhouse effect ie., rise of global temperature which has triggered melting of glacier thus increasing sea level and acidification of sea, carbon dioxide alone contributes approximately three-fourth of the net greenhouse radiative forcing by man-made (anthropogenic) greenhouse gases emissions. Carbon dioxide capture and storage (CCS) technology; a promising strategy for capturing of carbon dioxide from point sources before its release to atmosphere by using various sorbents is gaining global interest. In this study, the established carbon capture technologies with methods of carbon dioxide separation along there pros and cons are discussed. Carbon-based adsorbents are considered as the most versatile adsorbents for carbon dioxide due to their extraordinary physical and chemical properties. In this manuscript, recent developments on carbonaceous adsorbents (biochar, activated carbons, and graphene-based adsorbents) and their role in carbon dioxide capture during different combustion processes and conditions have been comprehensively focused.

Environmental remediation by microporous carbon: An efficient contender for CO2 and methylene blue adsorption

Nitrogen-doped microporous carbons with extremely narrow pore size distribution were derived from sucrose and melamine with the molten LiCl/KCl salts acting as a template to generate pores. A high CO2 uptake of up to 197 mg/g at 273 K and 1 bar was observed, revealing the significance of the pore size (0.84 nm) for CO2 capture. Our findings demonstrate that the nitrogen-doped SMLK-1 has a large surface area (951 m2/g) and large micropore volume (0.42 cm3/g) with high nitrogen-content (11.2 at.%), but the adsorption capacity (180 mg/g at 273 K, 1 bar) is comparable to that of un-doped SMLK-0 (SBET = 520 m2/g, Vmicro = 0.26 cm3/g). The CO2 uptake capacity per pore volume and volume fraction of the pores (<0.84 nm) in total pore volume exhibit a straight-line graph with a high correlation coefficient of 0.93 revealing that the adsorption capacity of the carbonaceous adsorbents may strongly rely upon the fine pore size distributions. Moreover, the prepared materials were also investigated as adsorbents for methylene blue from an aqueous solution. The sample with a melamine-to-sucrose ratio of 0 (SMLK-0) exhibited the excellent dye adsorption, 134.7 mg/g for an initial methylene blue concentration of 25 × 10−2 mM and 31.1 mg/g for an initial concentration of 5 × 10−2 mM. Therefore, the fabrication method presented here permits the fine-tuning of the pore network to exploit the prepared materials both as CO2 and dye adsorbents for environmental remediation.

Prediction of adsorption capacity for pharmaceuticals, personal care products and endocrine disrupting chemicals onto various adsorbent materials

Adsorption is a common process used to remove pharmaceuticals, personal care products and endocrine disrupting chemicals (PPCPs/EDCs) from water. However, as PPCPs/EDCs cover a wide range of molecules and chemical structures, prediction of the adsorption capacity is very challenging. In this study, a novel model was developed to predict adsorption isotherms of PPCPs/EDCs onto various types of adsorbents using a combination of Polanyi potential theory, molecular connectivity indices (MCIs) and molecular characteristics. Polanyi theory provided the basic mathematical form for the correlation. MCIs, hydrophobicity and H-bond count were used to normalize the Polanyi equation based on the molecular structure and interactions among the chemicals, the adsorbents, and the solution. In total, adsorption data were collected from 158 reports for 55 PPCPs/EDCs onto 306 different adsorbent materials. The correlation was first trained with 46 PPCPs/EDCs adsorbed onto 162 carbonaceous adsorbents (CAs), with 44.8% SDEV. Then the model was employed to predict 46 PPCPs/EDCs onto 118 other CAs and 9 new PPCPs/EDCs onto 23 CAs in ultrapure water, with error from 42 to 48% SDEV. When applying to non-carbonaceous adsorbents, the models can still predict the adsorption of PPCPs/EDCs with 90.09% SDEV. For the first time, a model, the PD – MCI – hydrophobic – H bond model, was developed to predict adsorption of a wide group of complicated PPCPs/EDCs onto a big variety of carbonaceous and non-carbonaceous adsorbents. The proposed model approach may provide a simple means for predicting adsorption capacities of PPCPs/EDCs onto various adsorbents.

Facile fabrication of nitrogen doped carbon from filter paper for CO2 adsorption

The preparation and application of heteroatom doped carbons have attracted lots of attention in the past years. In the current work, a facile synthesis of nitrogen doped carbon with filter paper as the carbon source and urea as the nitrogen source was presented. Filter paper was first impregnated with urea solution, and was then carbonized and activated. The carbons’ physical and chemical properties were studied. For the application in CO2 adsorption, impacts from porous characteristics and nitrogen doping were discussed and differentiated. The results suggested that nitrogen doping was beneficial to the improvement of CO2 uptake, but suitable porous properties were the most important factors. Nitrogen doping showed more significant effects on enhancing the adsorption heat and selectivity. The research of carbonaceous CO2 adsorbent should focus on nitrogen doped carbons with high porosity.

Fast adsorption of BPA with high capacity based on π-π electron donor-acceptor and hydrophobicity mechanism using an in-situ sp2 C dominant N-doped carbon

In this study, a high capacity (qm = 1351 mg g−1) with fast adsorption process (t < 5 min) towards bisphenol A (BPA) from water was achieved by an in-situ sp2 C dominant N-doped carbon (polydopamine-carbon, PDA-C). The adsorption mechanism facilitating to the superior removal performance of PDA-C was systematically investigated by relationship study (adsorption capacity VS physiochemical property) and theoretical calculation. It could be concluded that the dominant sp2 C (ID/IG = 0.92–1.02) and N-heteroatom (2.26–5.09 at. %) in PDA-C contributed to enhancing the adsorptive interactions of π-π electron donor-acceptor and hydrophobic effect between the PDA-C and BPA, thus realized a ~1.8 times enhancement of qm in comparison with the conventional carbon (PRF-C). Calculated adsorption energy from the density functional theory (DFT) further demonstrated that the adsorption potential of N-doped carbon towards BPA increased linearly with increasing doping of N-heteroatom, especially for the pyridinic N which determined the hydrophobic effect of carbon. This finding firstly points out the dominant strengthening mechanism of N-heteroatom for carbonaceous adsorbent. The synthesized PDA-C showed a promising environmental application potential as revealed from the stable BPA adsorption efficiency in the interferences (H+/OH−, NaCl and HA), dynamic adsorption operation and multiple cycling test.

Novel Use of Dairy Processing Sludge Derived Pyrogenic Char (DPS-PC) to Remove Phosphorus in Discharge Effluents

Pyrogenic char (PC) materials derived from the pyrolysis of dairy processing sludge (DPS) could be a cost effective option to develop carbonaceous adsorbent for phosphorus (P) removal from wastewater. The main objectives of the present work were to: (1) determine the efficacy of DPS derived PC (DPS-PC) to remove P from synthetic and dairy wastewater samples, (2) identify possible P removal mechanisms, and identify parameters that could be used to quickly identify the P removal capacity of a char and (3) propose a ranking system for the selection of DPS-PC which includes energy, char yield and P removal criterion. DPS-PC samples were obtained from the pyrolysis process (700 °C) of two sludge streams: (1) bio-chemically treated mixed sludge and (2) lime treated dissolved air floatation (DAF) sludge. Herein, 12 DPS-PC samples were assessed and pre-screened in batch experiments to determine the P removal efficacy from both synthetic and dairy wastewater solutions. The effect of solid to liquid dosage, contact time, pH and P concentration was investigated. Statistical regression and correlation analyses were performed to understand P removal mechanism. The quantitative assessment of char yield, energy balance and P removal performance were combined to propose a ranking system for DPS feedstock selection. P removal varied across DPS-PC type and composition, with mixed sludge derived char exhibiting 85–98% P removal at a dose of between 10 and 50 g/L, whereas, those from DAF sludge removed > 99% at 3 g/L. The P removal process was associated with a number of strongly significant mineral phase correlations pertaining to mineral composition (i.e. availability of Ca, Mg and Si) of the DPS-PC samples. A quick water extractible P test together with knowledge of the major P locking minerals can be used to pre-screen the potential of PC for P removal application. This study also provides a physicochemical reference and ranking of DPS feedstock selection, which will be useful for future investigation on the pyrolysis of DPS at pilot-scale and subsequently, to develop PC based efficient adsorbent for application in wastewater treatment.

Surface modification and characterization of carbonaceous adsorbents for the efficient removal of oil pollutants.

In this study, the impact of different oxidizing agents on the structural integrity of activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) was studied for the removal of BTX from aqueous solution. Seven different combinations of green oxidizing agents (mild organic acids) in conjugation with NaOCl (basic oxidizing agent) were used. The modified adsorbents were analyzed by Brunauer, Emmett, and Teller (BET) surface area analyzer, Fourier transform infrared spectroscopy (FTIR), Boehm titration, Raman spectroscopy, thermal gravimetric analysis (TGA), x-ray diffraction (XRD), zeta potential, and variable pressure field emission scanning electron microscope (VPFESEM). The results suggested that the carbonaceous sorbents modified with combination of citric acid tartaric acid, malic acid and salicylic acid (CTMS-I) showed increased surface area (O-AC: 871.67 m2/g, O-MWCNTs: 336.37 m2/g) and total pore volume (O-AC: 0.59 cm3/g, O-MWCNTs: 0.04 cm3/g), with the significantly improved thermal stability. Preliminary batch adsorption experiments conducted using the present prepared O-AC and O-MWCNTs, showed an improved performance towards the adsorption of BTX, compared with other available reported adsorbents in the literature.

Combination of alkalinity and porosity enhances formaldehyde adsorption on pig manure -derived composite adsorbents

Abstract Carbonaceous porous adsorbents of a high content of an inorganic phase (40–80%) were prepared by the zinc chloride activation of waste bio-char from the liquefication of pig manure at 900 °C. To increase both the content of the carbon phase and conductivity 10% nanographite was added to bio-char before the carbonization/activation process. Even though no strong effect of a char/activation agent ratio on the materials' porosity was found, they slightly differ in the surface areas and in the contents of the inorganic phase, which was found to be rich in calcium and magnesium. The synthesized materials were used as formaldehyde adsorbents from its low concentration of ∼2 ppm. The measured breakthrough capacity reached 0.78 mg/g and was higher than those measured on commercial carbons of high porosities. Since upon exposure to formaldehyde a marked surface acidification was found, the good performance of the composite adsorbents was linked not only to the porosity of the carbon phase but also to the effect of an alkaline environment in mesopores and to that of transition metals oxides on formaldehyde oxidation to formic acid. That acid likely formed salts with alkaline and alkaline earth metals present in our adsorbents. There was an indication that nanographite increased the extent of the formaldehyde oxidation reaction, which was demonstrated in a marked decrease in the surface pH of the spent adsorbent with the moderate amount of formaldehyde adsorbed.

Adsorption kinetics and aggregation for three classes of carbonaceous adsorbents in the presence of natural organic matter

In this study, adsorption kinetics of phenanthrene (PNT) and trichloroethylene (TCE) by a graphene nanosheet (GNS), a graphene oxide nanosheet (GO), a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube (MWCNT), and two coal based activated carbons (ACs) (F400 and HD3000) were examined in distilled and deionized water (DDW) and under natural organic matter (NOM) preloading conditions. The results showed the times needed for the adsorption of PNT and TCE to reach apparent equilibrium (i.e., ≤3% change per day) followed the order of GO ≥ MWCNT > GNS > SWCNT ∼ HD3000∼F400 and SWCNT > GNS ∼ HD3000 > F400 ∼ MWCNT > GO, respectively. The pseudo second order model successfully represented kinetics data for three classes of carbonaceous adsorbents. The Weber-Morris intraparticle diffusion model indicated three steps adsorption process for PNT and two step adsorption for TCE. In addition, the times needed to reach apparent equilibrium for the adsorption of PNT and TCE in the presence of hydrophobic (HPO) and hydrophilic (HPI) NOM solutions increased for all adsorbents (except for GO). In general, both NOM showed similar impacts on the adsorption rates of PNT and TCE. Aggregation of both GNS and CNTs rapidly occurred during initial couple hours of contact time during preloading, and spiking both PNT and TCE further increased their aggregation.

An insight into the adsorption of three emerging pharmaceutical contaminants on multifunctional carbonous adsorbent: Mechanisms, modelling and metal coadsorption

Pharmaceuticals (PhCs) are a specific group of emerging environmental contaminants, because there are designed to influence biochemical processes in non-target organisms even at low concentrations. In this study, phosphorised carbonaceous adsorbent (CScPA) was prepared from lignocellulosic biomass through thermochemical functionalisation. Phosphorus (P) doped microparticles were evaluated for the removal of emerging pharmaceutical contaminants such as sulfamethoxazole (SMX), carbamazepine (CBZ) and ketoprofen (KP) from aqueous solution. Characterisation of the adsorbent with the detailed mechanism study was carried out using pHpzc, SEM, BET, FTIR and XRD instruments. The influence of initial pH, adsorbent dose, contact time, initial pharmaceutical concentration and temperature on adsorption efficiency and capacity was evaluated in batch studies. CScPA exhibited excellent removal efficiency (≈99%) for all tested pharmaceuticals. According to FTIR results, the P containing groups showed obvious positive effects on pharmaceutical removal. The Langmuir isotherm (with maximal adsorption capacity of 19.181, 21.895 and 19.675 mg/g for SMX, CBZ, and KP, respectively) and the pseudo second-order kinetic model were suitable for describing the adsorption process. Adsorption mechanisms were mainly governed by π-π and n-π EDA interactions and H-bonds. It was demonstrated that presence of metal ions did not significantly influence pharmaceutical removal.

Enhancement Effect of Ordered Hierarchical Pore Configuration on SO2 Adsorption and Desorption Process

Carbonaceous adsorbents with both high sulfur capacity and easy regeneration are required for flue gas desulfurization. A hierarchical structure is desirable for SO2 removal, since the micropores are beneficial for SO2 adsorption, while the mesopore networks facilitate gas diffusion and end-product H2SO4 storage. Herein, an ordered hierarchical porous carbon was synthesized via a soft-template method and subsequent activation, used in SO2 removal, and compared with coal-based activated carbon, which also had a hierarchical pore configuration. The more detailed, abundant micropores created in CO2 activation, especially the ultramicropores (d &lt; 0.7 nm), are essential in enhancing the SO2 adsorption and the reserves rather than the pore patterns. While O2 and H2O participate in the reaction, the hierarchical porous carbon with ordered mesopores greatly improves SO2 removal dynamics and sulfur capacity, as this interconnecting pore pattern facilitates H2SO4 transport from micropores to mesopores, releasing the SO2 adsorption space. Additionally, the water-washing regeneration performances of the two types of adsorbents were comparatively determined and provide a new insight into the mass-transfer resistance in the pore structure. The ordered hierarchical carbon promoted H2SO4 desorption efficiency and cycled SO2 adsorption–desorption performance, further indicating that interconnecting micro- and mesopores facilitated the diffusion of adsorbates.

Chemically activated nanoporous carbon adsorbents from waste plastic for CO2 capture: Breakthrough adsorption study

Abstract This paper describes the preparation of O-enriched porous carbonaceous adsorbents derived from low cost, abundantly available polyethylene terephthalate (PET) waste with high carbon content by directly carbonising at different temperatures (500–800 °C) and then chemically activating using variable impregnation ratios of KOH to carbon. The prepared carbon adsorbents were characterized for their textural and surface chemical properties using nitrogen sorption, CHN, FTIR, XRD, SEM, HRTEM, and XPS techniques. Further, to assess their CO2 adsorption-desorption performance under dynamic conditions, breakthrough experiments were conducted in a fixed-bed adsorption set up. Porous carbon obtained at 700 °C with KOH to carbon mass ratio of 3 (Act-3-700) exhibited best textural properties with BET surface area of 1690 m2g-1 and micropore volume of 0.78 cm3 g−1 and showed highest CO2 uptake of 1.31 mmol g−1 at 30 °C and 12.5% CO2 concentration. Four adsorption–desorption cycles establish the adsorbent's remarkable stability and regeneration. Furthermore, fractional order kinetic model explained the CO2 adsorption kinetics and Freundlich isotherm showed superior fit with the adsorption equilibrium data suggesting heterogeneous nature of the adsorbent surface. Negative values of Gibbs free energy ΔG° and adsorption enthalpy ΔH° indicate the spontaneous and exothermic nature of adsorption process.

Adsorption of nitrate from aqueous phase onto nitrogen-doped activated carbon fibers (ACFs)

Rayon-based activated carbon fiber (ACF) was modified with several methods: acetonitrile thermal chemical vapor deposition at 800 °C (8AN) to dope nitrogen element on carbon surface, heat treatment at 950 °C (9.5HT) to convert doped nitrogen species into quaternary nitrogen (N-Q) and steam activation at 800 °C (8ST) to additionally develop pore structure. The modified samples were evaluated as adsorbents for the removal of nitrate from NaNO3 aqueous solution at equilibrium solution pH (pHe) around 3.0. Sequential modification of ACF with 8AN, 9.5HT and 8ST achieved the greatest adsorption capacity at 0.7 mmol/g in all prepared samples. The modified adsorbent was probably included in the greatest group in nitrogen-doped carbonaceous adsorbents for nitrate removal. To inspect the high adsorption capacity, specific surface area, elemental analysis and X-ray photoelectron spectroscopy measurements were conducted comparing with the other prepared adsorbents. Based on the data analysis, some specific surface area and N-Q might play an important role in the adsorptive removal of nitrate.

Regional variance in patterns of prescriptions for chronic kidney disease in Japan.

This study aims to describe the regional variance in prescriptions for chronic kidney disease (CKD) medications and to analyze regional characteristics to identify the sources of these differences by utilizing the National Database of Health Insurance Claims, which provides more than 95% of nationwide claim information for Japan. Data regarding the total claimed amount for phosphate binders (PBs), erythropoiesis-stimulating agents (ESAs), carbonaceous adsorbents, and potassium-lowering agents in fiscal year 2015 were obtained. Correlation coefficients were calculated for the claimed amount of these drugs per CKD patient and social and medical variables, including the percentage of the population aged ≥ 65years and the numbers of hospital beds and certified nephrologists. Subsequent multiple regression analysis was performed using explanatory factors affecting the amount of PB or ESA prescriptions per CKD patient. The total claimed amounts were 585,485,115 for PBs and 2,373,777 for ESAs. Variations in the claimed amount per CKD patient among 47 prefectures were 4.9-, 6.1-, 6.6-, and 6.0-fold for PBs, ESAs, carbonaceous adsorbents and potassium-lowering agents, respectively. The number of nephrologists per CKD patient was positively correlated with the prescribed amount for PBs and ESAs per CKD patient, and independently associated with the prescribed amount also in regression analysis. Substantial regional variation in CKD-related drug prescriptions exists even within a uniform health care system. The number of certified nephrologists was associated with the prescribed amount for PBs and ESAs. Further studies are needed to clarify whether geographic distribution of certified nephrologist may affect clinical practice pattern.

The effect of demineralization on the physicochemical and sorption properties of activated bio-carbons

Residues after supercritical extraction of hops were chosen as activated bio-carbons precursor. The actual adsorbent was prepared by physical activation of the starting material. Some amount of the activated bio-carbon was divided into two parts. One of them was washed with distilled water, while the other part of the activated bio-carbon was washed first with a 5% solution of HCl and then with distilled water. The activated bio-carbons obtained were subjected to textural characterization and determination of pH and the content of surface oxygen groups. Carbonaceous adsorbents obtained were tested for removal of gas pollutant of acidic character (nitrogen dioxide) and liquid organic (methylene blue) and inorganic (iodine) pollutants. The maximum sorption capacity of the carbonaceous adsorbents towards iodine was 1395 mg/g, while towards methylene blue it was 238 mg/g. The results have shown that physical activation of the residue after supercritical extraction of hops is possible to be used as precursor of activated bio-carbons showing high adsorption capacity towards nitrogen dioxide reaching a maximum of 72.1 mg/g. The effectiveness of nitrogen dioxide removal depends on bio-carbons preparation and the conditions of adsorption.