Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry and FTIR studies) Part I Primary phenolic antioxidants

The surface activity of different types of carbon black with phenolic antioxidants is examined using flow micro-calorimetry (FMC), X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FTIR). Significant differences in both the overall adsorption activity and the levels of probe adsorption are observed. Differences in behaviour between types of carbon black are evident and show that the specific surface area is not the most important factor affecting the adsorption activity, but also the chemical nature of its surface. Essentially, two factors were found to affect the behaviour of phenolic stabilisers: Phenolic hydroxyl and ester groups were found to form the strongest interactions with carbon black. Furthermore, steric hinderance of phenolic hydroxyls by alkyl groups is the main factor which influences adsorption activity. In order to characterise different carbon blacks, FTIR and XPS analysis have been used in an attempt to determine the nature of functional groups present on the surface of the carbon blacks. FTIR analysis also shows that some adsorbed antioxidants on the surface of the carbon black could be successfully detected. This provides valuable information regarding the adsorption mechanisms on to carbon black surfaces. Other techniques included thermogravimetric analysis (TGA), N₂ BET adsorption studies and Karl Fisher analysis. The latter were performed in order to determine differences in the volatile and water contents, respectively, of the carbon black samples.     

Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry studies) Part III Surface activity study using acid/base model probes

The first and second part of this series of papers investigated the interaction between carbon black and stabilisers (phenolic antioxidants and HALS, respectively) and showed that the mechanism was dependent on both the chemical nature of the carbon black surface and the molecular structure of stabilisers. In this third part, the interactions between model compounds, of varying acidity, and the same four carbon blacks, are investigated using flow micro-calorimetry (FMC) and Fourier transform Infrared spectroscopy (FTIR). As with the first and second parts, differences in adsorption behaviour between the four types of carbon black were evident and were principally related to the chemical nature of the surfaces and the adsorbates. In this study further insight in to the nature of the interactions between the carbon black surface functional groups and the acidic and basic probes has been acquired. The main forms of interaction are hydrogen bonding and Lewis and Bronsted acid/base interactions, formation of proton transfer complexes was also considered possible in cases of strong adsorption. The adsorption behaviour of acid and basic aromatic probes, together with octadecanol and stearic acid, was also found to be dependant on the carbon black surface topography. Flat graphene layers containing minimal heteroatoms favoured adsorption of the latter species as flat adsorption and/or structural ordering was permissable.     

办公废纸脱墨中表面活性剂吸附作用研究

目的基于表面活性剂与油墨及废纸纤维之间的交互作用对于浮选脱墨的重要意义,研究办公废纸脱墨中表面活性剂的吸附行为。方法选取十二烷基苯磺酸钠(C12H25Na O4S,SDBS)和全氟辛酸钠(SPFOF15Na O2,SPFO)等2种常用的阴离子表面活性剂,以及疏水性炭黑和亲水性办公室废纸纤维等2种典型物质,通过润湿实验,研究它们在浮选脱墨时的吸附性能。同时,通过在表面活性剂中添加钙,进一步探索钙和表面活性剂的结合作用对炭黑和废纸纤维表面吸附性的影响。结果在不添加钙形成聚集时,随着SDBS或SPFO平衡浓度的增加,炭黑或废纸纸纤维表面的SDBS或SPFO吸附密度将增加,SPFO在废纸纤维和炭黑表面及SDBS在纸纤维表面能形成双分子层吸附,但SDBS在碳黑表面是单层吸附;在表面活性剂溶液中添加钙时,随着钙离子浓度的增加,炭黑表面的SDBS或SPFO吸附均增加,当溶液p H值为9时,纸纤维上SPFO最大吸附密度高于SDBS,在纸纤维上的SPFO吸附存在"钙排斥"效应;炭黑上的SDBS吸附性与p H值无关。结论钙在办公废纸脱墨中是有效的催化剂,可以与阴离子表面活性剂产生协同吸附作用,提高废纸脱墨效果。     

Structure and antibacterial activity of silver-supporting activated carbon fibers

In this paper, several kinds of silver supporting activated carbon fibers (ACF-Ag) were prepared by the reduction adsorption on activated carbon fiber (ACF) activated with steam or H₃PO₄ using sisal, viscose and pitch fiber as precursors. Their pore structure and surface chemistry were characterized using nitrogen adsorption, XPS, WXRD and ICP quantitative analysis. Their antibacterial activities were tested. The results showed that metallic silver particle in micron or nano-scale size could be easily and dispersedly supported onto the surface of ACF using reduction property of ACF without largely decreasing their specific surface area. The ACF-Ag showed strong antibacterial activity against Escherichia coli and Staphylococcus aureus. The antibacterial activity has closed relationship with the precursors, the method of activation, silver content and the specific surface area of the ACFs. Generally, higher silver content and higher specific surface area provide the materials stronger antibacterial activity. ACF activated with phosphoric acid, due to the presence of certain amount of organic phosphoric groups on the surface, showed stronger antibacterial activity than those activated with steam. The antibacterial materials can be easily regenerated without decreasing their antibacterial activity and without releasing large amount of silver from the solid phase.     

Adsorption Properties of Multi‐wall Carbon Nanotubes

Abstract

Preparation of multi‐wall carbon nanotubes by means of arc‐discharge in He atmosphere was worked out and optimized. Electron micrographs show that electrode deposit consists of crossed multi‐wall carbon nanotubes. For study of adsorption properties of multi‐wall carbon nanotubes, the thermodynamic characteristics of adsorption of different classes organic compounds at small coverage were determined by gas chromatography and compared with those for graphitized carbon black and molecular crystals of fullerene C₆₀ (fullerite). The comparison of adsorption data for organic compounds with different functional groups on multi‐wall carbon nanotubes, on graphitized carbon black and fullerene C₆₀ shows the similarity of adsorption properties of multi‐wall carbon nanotubes and graphitized carbon black and the differences in molecular interaction of adsorbed molecules with crystal C₆₀.     

Adsorption of methyl tert-butyl ether (MTBE) from aqueous solution by porous polymeric adsorbents

MTBE has emerged as an important water pollutant because of its high mobility, persistence, and toxicity. In this study, a postcrosslinked polymeric adsorbent was prepared by postcrosslinking of a commercial chloromethylated polymer, and a nonpolar porous polymer with comparable surface area and micropore volume to the postcrosslinked polymer was prepared by suspended polymerization. The postcrosslinked polymer, nonpolar porous polymer and chloromethylated polymer were characterized by N2 adsorption, FTIR and XPS analysis. Results showed that postcrosslinking reaction led to the generation of a microporous postcrosslinked polymer with BET surface area 782m2g(-1), average pore width 3.0nm and micropore volume 0.33cm3g(-1). FTIR and XPS analysis indicated the formation of surface oxygen-containing groups on the postcrosslinked polymer. The three polymers were used as adsorbents to remove aqueous methyl tert-butyl ether (MTBE). Adsorption of MTBE over the postcrosslinked polymeric adsorbent was found to follow the linear adsorption isotherm, whereas MTBE adsorption onto the nonpolar porous polymer and chloromethylated polymer followed Langmuir adsorption model. Comparison of adsorption capacities of the postcrosslinked polymer, chloromethylated polymer and nonpolar porous polymer revealed that the adsorption of MTBE from aqueous solution is dependent on both pore structure and surface chemistry of polymeric adsorbents, and the high adsorption efficiency of the postcrosslinked polymer towards MTBE is attributed to its high surface area, large micropore volume and moderate hydrophility. The process of MTBE adsorption onto the adsorbents can be well described by pseudo-second-order kinetics, and the rate of adsorption decreased at higher MTBE initial concentration.     

Efficient removal of Cr (VI) from aqueous solution by halloysite/poly(amidoamine) dendritic nano-hybrid materials: kinetic,isotherm and thermodynamic studies

This paper demonstrates functionalization of a new hybrid nanoclay for effective adsorption of chromium(VI) ions from wastewater. Halloysite nanotubes (HNTs) were functionalized by poly(amidoamine) dendritic polymers (HNTs-(DEN-NH₂)) via a convergent synthetic route by carboxylic acid as a linkage. Various characterization methods confirm that poly(amidoamine) dendritic groups were effectively grafted onto the surface of HNTs that found a high specific surface area of 75 m²/g, as measured by micrometric BET analyzer. Moreover, the adsorption activity of HNTs-(DEN-NH₂) for Cr(VI) was systematically investigated using a batch solution that reveals the removal efficiency of 98% for HNTs-(DEN-NH₂) comparing to 23% for pristine HNTs, at optimum conditions. The enhancement of Cr(VI) removal for HNTs-(DEN-NH₂) comparing to HNTs was mainly ascribed to be due to the electrostatic interaction, that was confirmed by the results of Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Moreover, regeneration studies display that HNTs-(DEN-NH₂) can maintain removal Cr(VI) with high efficiency after four consecutive cycles.     

Change in the chemical structures of carbon black and active carbon caused by CF4 plasma irradiation

Carbon black and active carbon were fluorinated by exposure to CF₄ plasma. Their surface chemical structures were studied by means of elemental analysis, X-ray photoelectron spectroscopy, and inverse gas chromatography as a function of treatment time. Fluorine is mainly introduced onto the carbon black and active carbon surfaces during the CF₄ plasma treatment. The amount and type of carbon-fluorine (C-F) functionality formed on the surfaces of the carbon materials depends on the C-C framework structure as well as the plasma treatment time. C1s chemical shifts caused by C-F bonds on the fluorinated active carbon and carbon black surfaces are slightly different from those reported on the various types of fluorinated organic polymers, and have a somewhat ionic character. For the fluorinated active carbon the C-F bond is relatively stable, whereas for the fluorinated carbon black the C-F bond is unstable and has a significant ionic character. In addition, CO₂ gas adsorption characteristics on the fluorinated active carbon can be controlled by the surface C-F functionality.     

Removal of lead (II) and nickel (II) ions from aqueous solution using activated carbon prepared from rapeseed oil cake by Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> activation

In this study, rapeseed oil cake as a precursor was used to prepare activated carbons by chemical activation with sodium carbonate (Na₂CO₃) at 600 and 800 °C. The activated carbon with the highest surface area of 850 m² g^?1 was produced at 800 °C. The prepared activated carbons were mainly microporous. The activated carbon having the highest surface area was used as an adsorbent for the removal of lead (II) and nickel (II) ions from aqueous solutions. The effects of pH, contact time, and initial ion concentration on the adsorption capacity of the activated carbon were investigated. The kinetic data of adsorption process were studied using pseudo-first-order, pseudo-second-order kinetic models and intraparticle diffusion model. The experimental data were well adapted to the pseudo-second-order model for both tested ions. The adsorption data for both ions were well correlated with Langmuir isotherm. The maximum monolayer adsorption capacities of the activated carbon for the removal of lead (II) and nickel (II) ions were determined as 129.87 and 133.33 mg g^?1, respectively.     

Pore development process according to burn-off of activated carbon black with CO2 gas

Abstract

This study examined the pore development of carbon black according to burn-off (BO) ratio of carbon black activated in CO₂atmosphere. A horizontal tube furnace was charged with carbon black when the internal temperature reached 1000?°C, and activation time was adjusted to obtain BO ratios of 7.2%, 15.4%, 30.4%, 48.2%, 59.9%, and 83.2%. SEM observations showed that the primary particles of carbon black were aggregated, and varying BO ratios did not cause significant differences in shape and size. Carbon black was presumed to contain pores since the size of primary particles remained largely the same with varying BO ratios, and TEM observation revealed that pores existed within primary particles. The nitrogen adsorption isotherms were of type IV, which is characterized by a hysteresis loop. The specific surface area of raw carbon black was 61.4 m²/g, while that of BO at 83.2% increased 18.0 times to 1107.6 m²/g.     

Preparation of carbon supported platinum catalysts: role of π sites on carbon support surface

The role of the π sites in the adsorption of anionic platinum precursor (PtCl₆²⁻) on the carbon surface was studied. A set of carbon supports was prepared by the oxidative treatments of a commercial carbon black in liquid or thermal treatment in a nitrogen gas flow. The supports obtained had similar physical structure, but were different in their surface chemistry, e.g., the types and the amount of the surface functional groups. The Pt/C catalysts were prepared by the impregnation of the supports with an aqueous solution of hexachloroplatinic acid. N₂ adsorption, acid-base titration, X-ray photoelectron spectrometry (XPS), ICP, and TEM were used to characterize the supports and the catalysts. It was found that the absence of the surface acidic groups led to a higher platinum loading amount on the supports; and platinum loading amount would decrease when the higher H₂PtCl₆ impregnating solution concentration was used. The π sites in the basal planes play a more important role than the surface acidic groups in PtCl₆²⁻ ions adsorption on the carbon surface. Upon impregnation, the delocalized π electrons form coordination bonds with the platinum precursors, and further cause the reduction of Pt(IV) complex to Pt(II) complex, which was strongly chemisorbed on the surface of the supports. PtCl₆²⁻ ions adsorbing at the surface acidic groups would easily desorb during the washing process. However, when the impregnating solution was used at a higher concentration, a large amount of H₃O⁺ was firstly adsorbed in the π sites, leading to a decrease of the amount of strong PtCl₆²⁻ ions adsorption on the supports.     

Influence of sulfur-crosslinking in vulcanized rubber chips on mercury(II) removal from contaminated water

The adsorption of Hg(II) by natural rubber chips was investigated. First, the effect of chip size (5 mmx5 mm and 10 mmx10 mm) on the adsorption kinetics was studied. The pseudo-second-order modeling was found to explain the kinetics well. The smaller chips had higher adsorption rate so they were used for the rest of the research. Next the effects of sulfur, zinc oxide and carbon black on the adsorption capacity of Hg(II) at equilibrium conditions were investigated. The effect of sulfur was studied through different standard vulcanizing systems. The amount of zinc oxide was varied to be 3, 4 and 5 part per hundred parts of rubber (phr) while the carbon black (N-330) loading was varied to be 0, 30 and 50 phr, respectively. It was found that adsorption capacity increased with the degree of crosslink density, generated by sulfur reacting with rubber molecules. In addition, the adsorption capacities of various amounts of zinc oxide corresponded with their crosslink densities while the addition of carbon black seemed to obstruct Hg(II) adsorption.     

SOME IMPLICATIONS OF THE RADIATION-TREATMENT OF GRAPHITE AND CARBON BLACK

Graphite and carbon black N234 radiation damaged with γ radiation or with neutron bombardment have been studied with Raman spectroscopy. The radiation damaging results completely evident in the case of graphite with the development of the I_D band, but it is less evident in the case of an already disordered material like carbon black. The radiation damage caused by γ radiation appears comparable to that caused by neutrons, at least for the radiation dose used. Moreover, in both cases there are evidences that the radiation-induced defects appear in carbon material under the form of fullerene-like sites (onion-like carbon and carbon nanotubes) as well as under the form of hexagonal diamond and hence sp³ hybridized carbon.

Neutron damaged carbon black once treated with laser light at 782 nm shows a featureless Raman spectrum with a maximum at 2287 cm^?1 suggesting that neutron bombardment followed by laser light annealing causes the formation of carbyne (polyyne) domains.

The radiation treatment of graphite, carbon black and even amorphous precipitated silica enhances in a spectacular way their natural rubber adsorption power. This has been measured through the “bound rubber phenomenon” which is the irreversible rubber grafting reaction on filler surface. This enhancement has been attributed to the increased concentration of “defective” sites on filler surface induced by radiation treatment which improves the rubberfiller interaction. Another macroscopic consequence of this increased interaction can be manifested in SBR-based or in natural rubber based vulcanizates filled with radiation pre-treated carbon blacks. In both cases a dramatic improvement in the reinforcing effect as measured by stress-strain curve can be observed.     

Simulated body fluid (SBF) adsorption onto a-SiC:H thin films deposited by hot wire chemical vapor deposition (HWCVD)

Hydrogen amorphous silicon carbon (a-SiC:H) film deposited by the Hot Wire Chemical Vapor Deposition (HWCVD) technique on silicon substrates were soaked in simulated body fluid (SBF). Characterization of the film with different soaking durations in SBF was carried out by Fourier Transform Infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and contact angle measurements. It was found that the relative amounts of carbon in the a-SiC:H film surface decreases with increase in soaking period. XPS results showed the adsorption of Ca and Mg on the a-SiC:H surface. This indicates the formation of negatively charged surface possibly due to formation of silanol groups or dissolution of carbon to SBF confirming the bioactivity of the material. Contact angle decreased from 74° to 65° during 30 days of soaking in the body fluid. Present study is an attempt to observe the interaction of a-SiC:H film prepared by HWCVD technique with the body environment for its future suitability as artificial heart valve and stent coating materials.     

Fenton-like oxidation of Rhodamine B in the presence of two types of iron (II,III) oxide

The catalytic efficiency of iron (II, III) oxide to promote Fenton-like reaction was examined by employing Rhodamine B (RhB) as a model compound at neutral pH. Two types of iron (II, III) oxides were used as heterogeneous catalysts and characterized by XRD, Mössbauer spectroscopy, BET surface area, particle size and chemical analyses. The adsorption to the catalyst changed significantly with the pH value and the sorption isotherm was fitted using the Langmuir model for both solids. Both sorption and FTIR results indicated that surface complexation reaction may take place in the system. The variation of oxidation efficiency against H₂O₂ dosage and amount of exposed surface area per unit volume was evaluated and correlated with the adsorption behavior in the absence of oxidant. The occurrence of optimum amount of H₂O₂ or of exposed surface area for the effective degradation of RhB could be explained by the scavenging effect of hydroxyl radical by H₂O₂ or by iron oxide surface. Sorption and decolourization rate of RhB as well as H₂O₂ decomposition rate were found to be dependent on the surface characteristics of iron oxide. The kinetic oxidation experiments showed that structural Fe^II content strongly affects the reactivity towards H₂O₂ decomposition and therefore RhB decolourization. The site density and sorption ability of RhB on surface may also influence the oxidation performance in iron oxide/H₂O₂ system. The iron (II, III) oxide catalysts exhibited low iron leaching, good structural stability and no loss of performance in second reaction cycle. The sorption on the surface of iron oxide with catalytic oxidation using hydrogen peroxide would be an effective oxidation process for the contaminants.     

单宁改性酚醛基炭气凝胶的制备及其CO2吸附性能

基于绿色低成本的单宁所具有的大量反应性羟基,其与醛类反应具有与苯酚或间苯二酚相似的机制。在传统的酚醛树脂基(苯酚-尿素-甲醛)炭气凝胶的基础上,通过添加单宁进行改性,成功制备出新型高效的CO₂吸附用酚醛基炭气凝胶。通过扫描电子显微镜(SEM)、傅里叶红外光谱(FTIR)和氮气吸脱附测试对其表面化学和孔隙结构进行了系统表征,同时通过CO₂吸脱附测试对其CO₂吸附量、选择性吸附及吸附热等进行了研究。结果表明：以绿色可再生的生物质原料单宁对原料进行部分取代,不仅可以显著降低产品成本,还可以明显改善其CO₂的吸附性能。当单宁的添加量(15 g)为苯酚用量的50wt%时,样品具有最大的比表面积(1 376.31 m2·g^-1)和微孔体积(0.55 cm3·g^-1),是一种极具潜力的气体吸附材料。其相应的CO₂吸附量高达5.36 mmol·g^-1,选择性吸附和吸附热则分别为16.84和34.49 kJ·mol^-1<...     

Preparation of a silica gel–carbon black composite by the sol–gel process in the presence of polymer-grafted carbon black

This paper is concerned with the preparation of a silica gel–carbon black composite by the sol–gel process, which consists of tetraethoxysilane and polymer-grafted carbon black. Polymer-grafted carbon black was synthesized by three methods: (1) cationic polymerization of N-vinyl-2-pyrrolidone, (2) cationic ring-opening polymerization of 2-methyl-2-oxazoline, and (3) radical polymerization of glycidyl methacrylate followed by reaction of glycidyl groups in the grafted polymer chains with 3-aminopropyltriethoxysilane. The polycondensation of tetraethoxysilane proceeded under acidic conditions in the presence of polymer-grafted carbon black to give a deep black silica gel–carbon black composite. The more the content of untreated carbon black was increased, the more the gelation time was shortened. On the contrary, gelation was retarded by grafted polymer chains on the carbon black surface in the case of polymer-grafted carbon black. The scratch hardness of the resulting silica gel–carbon black composite was almost equal regardless of the carbon black content in the presence of untreated carbon black, whereas it was liable to decrease as the content of polymer-grafted carbon black increased. The solvent adsorption properties of the silica gel–polymer-grafted carbon black composite varied with the solubility of grafted polymer chains on the carbon black surface towards the immersion solvent. © 1998 Chapman & Hall     

Carbon spheres/activated carbon composite materials with high Cr(VI) adsorption capacity prepared by a hydrothermal method

Glucose and commercial activated carbon (AC) were used as starting materials to hydrothermally synthesize carbon spheres on the surface of AC, producing new carbon sphere–AC hybrid carbon materials. It was found that micrometer-sized carbon spheres, rich in oxygen-containing functional groups, can be effectively anchored to, and well-dispersed on, the surface and at the entrance to the macropores of AC. As the glucose concentration increased, the size and dispersion of carbon spheres changed, the porosity of the AC decreased, the number of oxygen-containing functional groups increased, and COH gradually became the dominant functional group. The carbon composites that were obtained exhibited a remarkably enhanced adsorption capacity for Cr(VI) per unit mass and per unit surface area. The highest adsorption capacity per unit mass achieved was 0.4834 mmol g^?1, about 4 times that of unmodified AC. The abundant surface oxygen-containing functional groups and relatively well-developed pore structure were the main causes of the high specific adsorption capacity of the carbon sphere/AC composites.     

水热法制备炭球—活性炭复合材料

以商品活性炭和葡萄糖为原料, 采用水热合成方法, 在活性炭表面和孔内合成纳米炭球, 制得富含含氧官能团的炭球—活性炭复合材料. 通过低温液氮(N₂/77K)吸附测定了炭球—活性炭复合材料的比表面积和孔容、孔径分布. 以SEM观测材料表面形貌. 采用FTIR、XPS分析复合材料的表面官能团结构. 以水相中无机Cr(VI)的去除测试材料的吸附性能. 结果表明：葡萄糖水热处理后在活性炭表面生成炭球, 活性炭孔隙结构降低, 炭球尺寸和分布受葡萄糖溶液浓度影响较大, 活性炭表面生成以—OH为主的含氧官能团. 炭球—活性炭复合材料对Cr(VI)的单位质量和单位面积吸附容量最高分别为原料活性炭的近4倍和95倍.     

Carbonization chemistry of heating carbon composites containing novolac/furfuryl alcohol resins and carbon black or mesophase pitch as additives

Carbon composites containing novolac/furfuryl alcohol resins with hexamethylene tetramine (HMTA) as a crosslinker and carbon black or mesophase pitch as an additive, were heated to 1000 °C under Argon atmosphere. Carbonization chemistry was studied including the nitrogen-containing structures in the final carbons. The volatiles released during the heating were furfuryl, phenol-benzene species, methane, ethane and other small molecular species such as moisture, CO₂, CO and ammonia. When carbon black was used as an additive in the composite, a considerable amount of furfuryl and phenolic species were “trapped” on the surface of carbon black particles, resulting in a higher carbon yield. Certain carbonization reactions also occurred at lower temperatures, and the dimensional shrinkage was reduced as compared to the resin-only system. On the other hand, the mesophase pitch additive formed homogeneous morphologies with the resin binder, participated in the carbonization process of the resin binder and formed amorphous carbons with porous structures and dimensional expansion. Manipulating the composition and variety of the additives could produce carbon composites with designed performance.