Acidic Oxygen-containing Groups Research Articles

Revealing the Key Role of Acidic Oxygen-Containing Groups on Activated Carbon for Low-Temperature NH3-SCR Denitration

Revealing the Key Role of Acidic Oxygen-Containing Groups on Activated Carbon for Low-Temperature NH3-SCR Denitration

Binding of Cd(II) to birnessite and fulvic acid organo-mineral composites and controls on Cd(II) availability

Manganese oxide minerals (MnOs) are major controls on cadmium (Cd) mobility and fate in the environment. However, MnOs are commonly coated with natural organic matter (OM), and the role of this coating in the retention and availability of harmful metals remains unclear. Herein, organo-mineral composites were synthesized using birnessite (BS) and fulvic acid (FA), during coprecipitation with BS and adsorption to preformed BS with two organic carbon (OC) loadings. The performance and underlying mechanism of Cd(II) adsorption by resulting BS-FA composites were explored. Consequently, FA interactions with BS at environmentally representative (5 wt% OC) increase Cd(II) adsorption capacity by 15.05–37.39% (qm = 156.5–186.9 mg g−1), attributing to the enhanced dispersion of BS particles by coexisting FA led to significant increases in specific surface area (219.1–254.8 m2 g−1). Nevertheless, Cd(II) adsorption was notably inhibited at a high OC level (15 wt%). This might have derived from the supplementation of FA decreased pore diffusion rate and generated Mn(II/III) competition for vacancy sites. The dominant Cd(II) adsorption mechanism was precipitation with minerals (Cd(OH)2), and complexation with Mn–O groups and acid oxygen-containing functional groups of FA. In organic ligand extractions, the exchange Cd content decreased by 5.63–7.93% with low OC coating (5 wt%), but increased to 33.13–38.97% at a high OC level (15 wt%). These findings help better understand the environmental behavior of Cd under the interactions of OM and Mn minerals, and provide a theoretical basis for organo-mineral composite remediation of Cd-contaminated water and soil.

Removal mechanisms of Cd from water and soil using Fe–Mn oxides modified biochar

The development of remediation materials simultaneously suitable for Cd-contaminated water and soil is of great significance. In this study, the functional biochar (FM-RBC and FM-DBC) was prepared using branch and durian shell biochar (RBC and DBC, respectively) with iron-manganese oxide (Fe–Mn oxide) modification. The behaviors and mechanisms of Cd adsorption and stabilization in water and alkaline soil treated with FM-RBC and FM-DBC were explored. The results showed that the adsorption capacities of RBC and DBC for Cd had increased by 40–80 mg/g after the Fe–Mn oxide modification. The Cd adsorption was conformed to pseudo-second-order kinetic and the Langmuir isothermal models. After 35 days of soil cultivation, the maximum reduction rate of DTPA-Cd occurred in 3% FM-DBC treatments (37.73%), followed by in 3% FM-RBC (30.08%), all of which were significantly higher than that observed in 3% BC treatments (12.55–18.91%). Notably, the FM-RBC and FM-DBC treatments promoted the conversion of the exchangeable to the carbonate-bound and Fe/Mn oxyhydroxide fractions of Cd. The XRD, FTIR, and XPS analyses demonstrated that the loading amount of Fe–Mn oxide was positively correlated with the oxygen-containing functional group of biochar. CdO, Cd2Mn3O8 and CdCO3 were loaded on the FM-BC, indicating the existence of two main adsorption mechanisms: (1) the complexation with M-O (M: Fe, Mn) and acid oxygen-containing functional groups, (2) the precipitation with carbonate of Cd. In this work, we prepared two functional biochar that rapidly removes Cd from water and effectively fixes Cd in alkaline soil, thus, debasing the risk of Cd entry into the food chain.

Fabrication of environmentally-friendly composited sponges for efficient removal of fluoroquinolones antibiotics from water

In this study, two environmentally-friendly macroscopically formal (PVF) composited sponges (PL and PLS) functionalized with lignin and lignosulfonate, respectively, were fabricated by a one-step mechanical foaming method. PLS, obtained with the fed mass ratio of 0.3:1 lignosulfonate to PVF in the preparation process, possessed a large specific surface area of approximately 22.396 m2/g, a three-dimensional skeleton structure with a skeletal density of 3.236 g/cm3, and 0.338 mmol/g of acidic oxygen-containing groups. Thus, it showed a high adsorption capacity of 0.16–0.24 mmol/g in removing seven antibiotics, of the popular fluoroquinolones (FQs) family from water. The contributions of hydrogen bonding, electrostatic attraction (EA) and π-π electron donor-acceptor interaction to the adsorption of FQs onto the PL and PLS sponges were analyzed systematically by investigating the pH dependence of the adsorption capacity, and the changes in adsorption of two sub structural analogs of FQs as molecular probes, and by performing theoretical calculations. The EA between the acidic oxygen-containing groups on the sponges and the amino groups of FQs played a dominant role in adsorption in near neutral conditions, leading to a superior adsorption performance for PLS. Overall, the composited sponges have the advantages of simple production, environmental-friendliness, convenient recycle, and low cost, which renders them potentially viable in treating real wastewater containing FQs.

More octahedral Cu+ and surface acid sites in uniformly porous Cu-Al2O3 for enhanced Fenton catalytic performances

Porous Cu-doped alumina (P-Cu-Al2O3) has been synthesized using ammonium chloride as a green gaseous template. The unique pore-forming agent endows the catalyst a large surface area and homogenous pore structure. According to the characterization results by multi-technologies, the highly dispersed framework Cu+/Cu2+ was incorporated in octahedral sites with the formation of the Cu-O-Al bonds. Compared with bulk Cu-doped Al2O3 (B-Cu-Al2O3), more surface acidic oxygen-containing groups and Lewis acid sites existed in P-Cu-Al2O3, resulting in the production of surface adsorbed •OH, which is helpful for the removal of surface adsorbed organic intermediates. In addition, O2 more easily participate in surface reaction to promote the •OH generation in P-Cu-Al2O3 system than that in B-Cu-Al2O3. As a result, the representative endocrine disruptor bisphenol A can be more efficiently mineralized by P-Cu-Al2O3. This work provides a facile route to develop porous active heterogenous Fenton-like catalysts and a unique perspective to insight into the structure-activity relationship.

Sulfur-doped porous carbon derived from waste polyphenylene sulfide for efficient adsorption removal of Cd2+ from simulated wastewater

Sulfur-doped porous carbon materials were prepared from waste polyphenylene sulfide (PPS) by chemical activation using potassium hydroxide as activator. The elemental composition (sulfur content) and the number of acid oxygen-containing groups on the surface of the samples were determined by elemental analysis and Boehm method, respectively. The effects of preparation temperature and adsorption conditions on the removal of Cd2+ from simulated wastewater were studied according to the amount of cadmium removal. The results showed that the sulfur-doped porous carbon materials prepared under the optimal preparation conditions had better adsorption properties as compared to HNO3 modified bamboo-derived biochar. This result is mainly due to the Lewis acid-base interaction between sulfur and Cd2+ in addition to the coordination of Cd2+ and oxygen-containing groups on the surface. Under the optimal adsorption conditions, the removal of cadmium in simulated wastewater can reach 98.74%. In conclusion, this cheap porous carbon material may be a useful adsorbent for cadmium.

A lignin-biochar with high oxygen-containing groups for adsorbing lead ion prepared by simultaneous oxidization and carbonization

A lignin-biochar with high acidic oxygen-containing groups was produced via a facile simultaneous oxidization and carbonization of pulping lignin by using sulfuric acid for the first time. The lignin-biochars were investigated by 13C NMR, FTIR and XPS, and results demonstrated that treatment by sulfuric acid could oxidize part of aromatic ring side chain to introduce high acidic oxygen-containing group, especially carboxyl group. Their total acidic oxygen-containing groups of lignin-biochar including COOH and Ar-OH reached 8.64 mmol/g. Adsorption experiments were carried and the maximum adsorption capacity of lignin-biochar for Pb2+ reached 679 mg/g, which was significantly higher than other lignin-based or carbon adsorbents. Moreover, it could maintain high removal rate at high adsorption capacity. It also demonstrated that adsorption capability was proportional to the accessible carboxyl groups.

The interaction of perrhenate and acidic/basic oxygen-containing groups on biochar surface: A DFT study

Biochar has a good adsorption ability for perrhenate (ReO4−), which can be attributed to its abundant oxygen-containing groups, yet the effects of oxygen-containing groups on ReO4− adsorption are still unclear. Here, the interaction of ReO4− and acidic/basic oxygen-containing groups (hydroxyl, carboxyl, pyrone and chromene) on biochar were investigated by density functional theory (DFT) calculation with conductor-like screening model (COSMO). According to the calculated results, it was evidenced that the adsorption of oxygen-containing group functionalized BC towards ReO4− was gradually strengthened as decreased pH, and the protonated positively charged oxygen-containing groups presented stronger chemisorption to ReO4− mainly through electrostatic interaction, complexation and atomic orbital hybridization. The protonated hydroxyl and carboxyl and the protonated etheric oxygen of pyrone and chromene can offer favorable binding sites to ReO4−. Compared with the acidic oxygen-containing groups, the higher adsorption energy values, and the larger Mayer bond order indexes of interacting atoms identified that the basic oxygen-containing groups have stronger affinity with ReO4−. Pyrone had the strongest adsorption stability toward ReO4−. Our results can provide new ideas into the design and preparation of separation materials for ReO4− or the other anions capture from the aqueous solution.

Adsorptive removal of strontium ions from aqueous solution by graphene oxide.

Graphene oxide (GO) was prepared, characterized, and applied for adsorption of Sr(II) in aqueous solution. The adsorption capacity was calculated to be 137.80 mg/g according to the Langmuir model. The observation by scanning electron microscope with energy dispersive X-ray detector (SEM-EDX), high-resolution transmission electron microscope (HRTEM), and X-ray diffraction (XRD) revealed the crystal structure of Sr compound on the surface of graphene sheets. The analyses by the Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated the involvement of O-C=O, C-O, and C-O-C groups during the adsorption. The X-ray absorption fine structure (XAFS) analysis provided the detail information of GO-Sr composites, and the fitting results were given by Sr(HCOO)2 and SrCO3 model, and the coordination numbers (CN) and interatomic distances (R) of Sr-O shell and Sr-C shell were calculated. The adsorption mechanism of Sr(II) was attributed to complexation between Sr and the acidic oxygen-containing groups, which lead to the agglomeration of graphene oxide. Two types of crystals were proposed. Type 1 was formed by coordination between Sr(II) and O-C=O groups, and type 2 was formed by coordination between Sr(II) and C-O/C-O-C groups.

Platinum supported cellulose-based carbon with oxygen-containing functional groups for benzyl alcohol oxidation

Porous carbon was prepared through a simple and efficient method using microcrystalline cellulose as carbon source. Compared with pristine carbon (C-1), nitric acid treated carbon (C-2) has more acidic oxygen-containing groups on its surface (acid density: 0.14 mmol/g for C-1 and 2.13 mmol/g for C-2). Pt supported Pt/C-2 behaves a substantially enhanced catalytic oxidation activity of benzyl alcohol (conversion of 71.7%) compared with Pt/C-1(conversion of 37.2%) under the same conditions. Further characterizations and experiments indicate that the excellent dispersion of Pt nanoparticles and strong hydrogen bonding interaction between benzyl alcohol and Pt/C-2 are crucial for the enhanced catalytic activity. Our experimental results also show that mild temperature (60 °C) and non-polar solvents are more beneficial for the reaction, and O2 atmosphere is a necessity for benzyl alcohol oxidation.

Behavior of activated carbons by compound modification in high gravity for toluene adsorption

The rotating packed bed is a chemical apparatus that strengthens mass transfer between phases to enhance their reactivity. It can be used to modify adsorbent materials, greatly improving their chemical properties. This article studies the effect of compound modification of activated carbons in a high-gravity environment on their toluene adsorption. The compound modification includes physical (N2) and chemical modification (HNO3), and the effect of modification is compared between traditional fixed-bed and rotating packed bed modification. The physical characteristics of the activated carbons, including pore size, specific surface area, and morphology are tested by Brunauer–Emmett–Teller and scanning electron microscopy, and the surface functional groups of the activated carbons are determined by Fourier transform infrared spectroscopy and Boehm titration. The results indicate that the activated carbons modified by rotating packed bed have a larger specific surface area (871.5 m2/g) and smaller pore size (0.524 nm), and the content of acidic oxygen-containing groups is 1.5 times that of unmodified activated carbons. The adsorption capacity of the activated carbons compound-modified by rotating packed bed increases by 69% compared with the unmodified activated carbons. The adsorption by the rotating packed bed-compound-modified activated carbons obeys the Freundlich model. The modification of activated carbons by rotating packed bed greatly enhances their specific surface area, pore size, and surface content of oxygen-containing functional groups, markedly improving the adsorption performance and increasing the utilization rate.

Characteristics of activated carbon modified with alkaline KMnO4 and its performance in catalytic reforming of greenhouse gases CO2/CH4

Different potassium permanganate oxidation processes were used to modify activated carbon, and then surface structure and chemical properties of modified activated carbon with different preparation methods as well as their influences on carbon dioxide reforming of methane were studied. BET and SEM surface structure analysis indicated that after modification with potassium permanganate under alkaline condition, specific surface area of activated carbon increased, microspore and mesoporous capacities enlarged, but the pore diameter of activated carbon slightly reduced. XPS and FT-IR characterization indicated that after modification with potassium permanganate under alkaline condition, acid oxygen-containing functional groups dropped and new alkaline active substances like ionic OH− and manganite were generated on the activated carbon surface. Increased specific surface area and pore capacity of activated carbon, reduced acid oxygen-containing groups and generated alkaline active substances like ionic OH− and manganite exerted significant influences on methane activation and carbon dioxide reforming of methane. Under alkaline condition, the activity of the potassium permanganate modified activated carbon and reforming conversion slightly increased because of interaction between alkaline functional groups and acid carbon dioxide; In the meantime, newly generated ionic OH− on the surface and manganite participated in reforming reaction, which also improved activity of potassium permanganate-modified activated carbon for carbon dioxide reforming of methane. Under acid condition, CO2-CH4 reforming conversion and catalyst activity decreased because of interaction between acidic functional groups and acid carbon dioxide.

Role of the functional groups in the adsorption of bisphenol A onto activated carbon: thermal modification and mechanism

Surface properties of activated carbons play vital roles in adsorption of contaminants. Aiming to improve the adsorption of phenolic endocrine disrupting chemicals (EDCs), commercially activated carbon (W20) was modified via thermal treatment to obtain a carbon sample (W20N) with different characteristics. The content of acidic oxygen-containing groups of W20 was obviously reduced by the thermal modification. Bisphenol A (BPA) was chosen as the target compound. The adsorption results indicated that the acidic oxygen-containing groups (especially carboxyl groups) on the surface of activated carbons weakened the ability of carbon acting as π-donors that lead to the reduction of BPA adsorption. Compared to W20, W20N with a greater number of phenyl groups exhibited higher adsorption capacity for BPA in a wide range of pH (4.0–10.0). Therefore, thermal modification improved BPA adsorption onto activated carbon. Furthermore, thermodynamic analysis and effect of solution pH revealed that BPA adsorption onto W20 and W20N probably followed face-to-face π–π dispersion interactions. Coexisting tannic acid (TA) formed BPA–TA complexes and played a negative role in BPA adsorption onto carbon based on the π–π dispersion interaction. This study should help broaden the scope of modification methods and the application of activated carbons to enhance the removal of phenolic EDCs.

Adsorption of creatinine on active carbons with nitric acid hydrothermal modification

The adsorption of creatinine on active carbons was studied. Original active carbon (AC) and AC samples modified by nitric acid hydrothermal modification were assessed for their ability to adsorb creatinine. The pore structure and surface properties of the AC samples were characterized by N2 adsorption, temperature programmed desorption (TPD), Fourier Transform Infrared spectroscopy (FTIR), and X-ray photoelectron spectrometer (XPS). It indicated that 4M HNO3 hydrothermal modification with 180 °C was an efficient method in improvement of the creatinine adsorption. The improved adsorption capacity can be attributed mainly to an increase in the acidic oxygen-containing functional groups. The adsorption of creatinine over AC may involve an interaction with the acidic oxygen-containing groups on AC. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherm and isotherm constants. Equilibrium data fitted very well to the Freundlich model in the entire saturation range (3.58–59.08mg L−1). The maximum adsorption capacities of AC modified with 180 °C is 62.5mg g−1 according to the Langmuir model. Pseudo first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model, which indicates that the chemical adsorption was the rate-limiting step, instead of mass transfer.

Preparation and characterization of semi-carbonized rice straw fiber

The semi-carbonization method is a kind of waste treatment to carbonize rice straw fiber at low semi-carbon temperature. The rice straw fiber is carbonized incompletely, which serves as building materials additive. The results reveal that the optimized carbonization condition is at 313 °C for 20-40 min with H3PO4 as activator. The structure of semi-carbonized straw fiber displays a large quantity of micropores, with which the wall thickness and the pore diameter are in the range of 1-4 μm, presenting the iodine sorption value of 1 320-1 470 mL/g and the methylene blue sorption value of 1 330-1 460 mg/g, respectively. Moreover, the acidic oxygen-containing groups impart the structure higher sorption of polar molecules. The semi-carbonized rice straw fiber with open and closed micro-mesopores demonstrates good hygroscopicity, implying the potential application as a functional additive in building materials.

The effect of functional groups on the SO2 adsorption on carbon surface I: A new insight into noncovalent interaction between SO2 molecule and acidic oxygen-containing groups

For the aim to give a new insight into the interactions between SO2 molecule and carbon surface and the effect of acidic oxygen-containing groups, density functional theory and noncovalent interaction analysis in terms of reduced density gradient were employed to investigate both the intensity and type of the interactions. The results indicate that the physisorption of SO2 molecule mainly occurs on the basal plane of pure carbon surface due to van der Waals interactions, however, when acidic oxygen-containing groups were decorated on the carbon surface, they would facilitate SO2 adsorption as a result of hydrogen bonding and dipole–dipole interactions. What's more, these groups could not affect the chemisorption of SO2 remarkably, no matter they are near the adsorption sites or not. In addition, calculation results show that the interactions between SO2 and acidic oxygen-containing groups are in physisorption nature, which challenges a long-held the viewpoint of irreversible chemisorption. Acidic oxygen-containing groups could boost the effective surface area of carbon by enhancing the physisorption on edge positions.

Adsorption of acetaldehyde onto carbide-derived carbon modified by oxidation

The adsorption of acetaldehyde over carbide-derived carbon (CDC) modified with nitric acid, hydrogen peroxide, or air was investigated. The physicochemical properties of the original and modified CDCs were characterized by N2 adsorption, Fourier transform infrared spectrometer, temperature programmed desorption and X-ray photoelectron spectroscopy. It was observed that the oxidation modification, especially the nitric acid treatment, could significantly enhance the adsorption performance of CDC for acetaldehyde. The increase of acidic oxygen-containing groups like carboxylic acids and anhydrides in the modified CDCs results in the increase of adsorption performance. The density functional theory calculations and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy show that these acidic oxygen-containing groups display strong hydrogen bonding interactions with acetaldehyde molecule, leading to the enhanced adsorption performance.

Study on the Impact of Degummed on Pineapple Leaf Fiber’s Structures and Formaldehyde Adsorptions

The micro-structural and formaldehyde adsorption abilities of pineapple leaf raw and degummed fibers are characterized by using SEM, FT-IR, chemical composition analysis and determination of acidic oxygen-containing functional groups and more other methods. Test results show that after being degummed, pineapple leaf fibers possess smoother surfaces, obvious grooves, better single-fiber separations and non-significant cross-sectional cavities. Hemicellulose’s characteristic absorption peaks disappear basically and their contents are reduced from 20.62% to 2.65%. The intensities of lignins’ characteristic absorption peaks drop and their contents are decreased from 3.68% to 1.20%. The locations of celluloses’ characteristic absorption peaks do not change too significantly and their contents are increased from 61.18% to 84.45%. The numbers of carboxyl, lactone and phenolic hydroxyl in acid oxygen-containing functional groups are reduced. Pineapple leaf raw fibers have higher formaldehyde adsorption abilities. After degumming, formaldehyde adsorption abilities of pineapple leaf fibers are similar, but all slightly lower than raw fibers.

Activated carbon-enhanced ozonation of oxalate attributed to HO oxidation in bulk solution and surface oxidation: Effects of the type and number of basic sites

The objective of this work is to study the influence of the type and number of basic sites of activated carbon (AC) on the AC-enhanced ozonation of oxalate. A commercial activated carbon (AC) was thermally treated with N-2, H-2, and NH3 at different temperatures. The results of chemical and textural characterization of the original and modified ACs show that the specific surface area and number of basic sites generally increased with increasing treatment temperature, whereas the acidic oxygen-containing groups decreased. Nitrogen-containing groups formed after NH3 treatment. The oxalate removal rate increased in ozonation systems with modified ACs compared with that of systems with the original AC. Oxalate degradation increased when ACs with higher numbers of basic sites and larger specific surface areas were used, except for the AC treated under NH3 at 900 degrees C. Oxalate removal was attributed to surface oxidation and HO. oxidation in bulk solution. The former process was dominant in the ozonation system with 0.2 g/L AC at pH 7. The experimental results indicate pyrrole groups may enhance ozone decomposition to generate HO. in bulk solution, while pyridine groups possibly decreased the surface oxidation of oxalate. Other basic sites, such as basal planes and basic oxygen-containing groups, enhanced oxalate removal through surface oxidation, and indirectly weakened HO. oxidation of oxalate in bulk solution. (C) 2014 Elsevier B.V. All rights reserved.

Sustainable Energy Recovery in Wastewater Treatment by Microbial Fuel Cells: Stable Power Generation with Nitrogen-doped Graphene Cathode

Microbial fuel cells (MFCs) recover energy sustainably in wastewater treatment. Performance of non-noble cathode catalysts with low cost in neutral medium is vital for stable power generation. Nitrogen-doped graphene (NG) as cathode catalyst was observed to exhibit high and durable activity at buffered pH 7.0 during electrochemical measurements and in MFCs with respect to Pt/C counterpart. Electrochemical measurements showed that the oxygen reduction reaction (ORR) on NG possessed sustained activity close to the state-of-art Pt/C in terms of onset potential and electron transfer number. NG-MFCs displayed maximum voltage output of 650 mV and maximum power density of 776 ± 12 mW m(-2), larger than 610 mV and 750 ± 19 mW m(-2) of Pt/C-MFCs, respectively. Furthermore, long-time test lasted over 90 days, during which the maximum power density of NG-MFCs declined by 7.6%, with stability comparable to Pt/C-MFCs. Structure characterization of NG implied that the relatively concentrated acidic oxygen-containing groups improved such long-time stability by repelling the protons due to the same electrostatic force, and thus the C-N active centers for ORR were left undestroyed. These findings demonstrated the competitive advantage of NG to advance the application of MFCs for recovering biomass energy in treatment of wastewater with neutral pH.