Nitrogen-Doped Porous Carbon Materials Derived from Graphene Oxide/Melamine Resin Composites for CO2 Adsorption

CO₂ adsorption in porous carbon materials has attracted great interests for alleviating emission of post-combustion CO₂. In this work, a novel nitrogen-doped porous carbon material was fabricated by carbonizing the precursor of melamine-resorcinol-formaldehyde resin/graphene oxide (MR/GO) composites with KOH as the activation agent. Detailed characterization results revealed that the fabricated MR(0.25)/GO-500 porous carbon (0.25 represented the amount of GO added in wt.% and 500 denoted activation temperature in °C) had well-defined pore size distribution, high specific surface area (1264 m²·g⁻¹) and high nitrogen content (6.92 wt.%), which was mainly composed of the pyridinic-N and pyrrolic-N species. Batch adsorption experiments demonstrated that the fabricated MR(0.25)/GO-500 porous carbon delivered excellent CO₂ adsorption ability of 5.21 mmol·g⁻¹ at 298.15 K and 500 kPa, and such porous carbon also exhibited fast adsorption kinetics, high selectivity of CO₂/N₂ and good recyclability. With the inherent microstructure features of high surface area and abundant N adsorption sites species, the MR/GO-derived porous carbon materials offer a potentially promising adsorbent for practical CO₂ capture.     

One-Pot Synthesis of N-Rich Porous Carbon for Efficient CO2 Adsorption Performance

N-enriched porous carbons have played an important part in CO₂ adsorption application thanks to their abundant porosity, high stability and tailorable surface properties while still suffering from a non-efficient and high-cost synthesis method. Herein, a series of N-doped porous carbons were prepared by a facile one-pot KOH activating strategy from commercial urea formaldehyde resin (UF). The textural properties and nitrogen content of the N-doped carbons were carefully controlled by the activating temperature and KOH/UF mass ratios. As-prepared N-doped carbons show 3D block-shaped morphology, the BET surface area of up to 980 m²/g together with a pore volume of 0.52 cm³/g and N content of 23.51 wt%. The optimal adsorbent (UFK-600-0.2) presents a high CO₂ uptake capacity of 4.03 mmol/g at 0 °C and 1 bar. Moreover, as-prepared N-doped carbon adsorbents show moderate isosteric heat of adsorption (43–53 kJ/mol), acceptable ideal adsorption solution theory (IAST) selectivity of 35 and outstanding recycling performance. It has been pointed out that while the CO₂ uptake was mostly dependent on the textural feature, the N content of carbon also plays a critical role to define the CO₂ adsorption performance. The present study delivers favorable N-doped carbon for CO₂ uptake and provides a promising strategy for the design and synthesis of the carbon adsorbents.     

Preparation of Bamboo-Based Hierarchical Porous Carbon Modulated by FeCl3 towards Efficient Copper Adsorption

Using bamboo powder biochar as raw material, high-quality meso/microporous controlled hierarchical porous carbon was prepared—through the catalysis of Fe³⁺ ions loading, in addition to a chemical activation method—and then used to adsorb copper ions in an aqueous solution. The preparation process mainly included two steps: load-alkali leaching and chemical activation. The porosity characteristics (specific surface area and mesopore ratio) were controlled by changing the K₂CO₃ impregnation ratio, activation temperature, and Fe³⁺ ions loading during the activation process. Additionally, three FBPC samples with different pore structures and characteristics were studied for copper adsorption. The results indicate that the adsorption performance of the bamboo powder biochar FBPC material was greatly affected by the meso/micropore ratio. FBPC _2.5-900-2%, impregnated at a K₂CO₃: biochar ratio of 2.5 and a Fe³⁺: biochar mass ratio of 2%, and activated at 900 °C for 2 h in N₂ atmosphere, has a very high specific surface area of 1996 m² g⁻¹ with a 58.1% mesoporous ratio. Moreover, it exhibits an excellent adsorption capacity of 256 mg g⁻¹ and rapid adsorption kinetics for copper ions. The experimental results show that it is feasible to control the hierarchical pore structure of bamboo biochar-derived carbons as a high-performance adsorbent to remove copper ions from water.     

氧化多壁碳纳米管对Pb2+的吸附性能研究

该文研究了氧化多壁碳纳米管(o-MWNTs)对Pb2+的吸附性能,考察了平衡时间、溶液pH值、溶液体积等因素对吸附行为的影响。在静态吸附条件下:Pb2+能大量并快速地被o-MWNTs吸附,45 min内即可达到吸附平衡,而活性炭(ACs)的吸附平衡时间为90 min。溶液pH值在1.0~7.0范围对吸附量有显著影响,在pH5.0~6.0时o-MWNTs对Pb2+的静态吸附容量为17.43 mg.g-1。o-MWNTs对铅离子的吸附量随着溶液体积的增加而增加,并逐渐趋于稳定,最大吸附量可达25 mg.g-1。在动态吸附实验中,30 mg.L-1的铅离子溶液在SPE小柱的穿透体积为235 mL,溶液体积为400 mL时可完全穿透。动态吸附实验表明,o-MWNTs对铅离子具有较大的吸附容量且萃取回收率高达94%。研究表明,氧化碳纳米管装填的固相萃取小柱可用于中药提取物中Pb2+的残留分析。     

香蕉皮对重金属离子铅的吸附性能研究

建立了香蕉皮快速、高效对重金属离子铅吸附性能的方法。采用分光光度法测定重金属离子铅的浓度,分别研究了7种不同形态的吸附剂对废水中重金属离子铅的吸附性能。在优化的实验条件下,重金属离子铅浓度与吸光度的线性相关系数R=0.999 83,且方法相对标准偏差(RSD)低于3%。结果表明,香蕉皮对废水中的重金属离子铅有良好的吸附效果,吸附率达到91.3%。利用香蕉皮去除废水中的重金属离子,可以变废为宝,且方法吸附率高、准确可靠、精密度高,可用于吸附废水中重金属离子铅。     

A fluorescence reagent for the highly selective recognition and separation of lead ion (II) from aqueous solutions

A new fluorescence reagent, N,N-bi[4(1-pyrene)-butyroyl]-lysine (1) was synthesized. The new fluorescence sensor showed high sensitivity (detection limit up to 20.7 μg L⁻¹) and specific selectivity for Pb²⁺ over other metal ions examined in aqueous solutions. It could also be used to remove Pb²⁺ from aqueous solutions by filtering the insoluble 1–Pb²⁺ complex with sufficient reversibility.     

孔结构对活性炭吸附水溶液中铅离子的影响

选取三种表面化学性质相近的活性炭(AC),通过等温吸附实验考察活性炭对水溶液中铅离子的吸附性能,利用扫描电子显微镜(SEM)观察活性炭的表面微观形貌,通过低温(77 K)液氮吸附测定活性炭的比表面积和孔容,并分别以密度泛函理论(DFT)和Barrett-Joyner-Halenda (BJH)法计算微孔和中孔的孔径分布.结果表明:选用的三种活性炭AC1、AC2、AC3在比表面积和总孔容上呈依次下降的趋势,但表面开放孔均匀分布的AC2,具有最高的饱和吸附量,孔结构类似颗粒堆积孔的AC3,具有与表面开放孔分布集中的AC1相近的饱和吸附量;通过对孔结构与吸附量的关联分析可知,在活性炭吸附铅离子的过程中, 0.4-0.6 nm的孔是有效吸附孔, 10.5-20.6 nm、20.6-55.6 nm、5.2-10.5 nm三个区间的孔则会对吸附产生阻碍作用.     

Turn-on ratiometric fluorescent sensor for Pb detection

We report a ratiometric lead fluorescent sensor (LFS-1) with high affinity to Pb²⁺ that shows considerable selectivity over 12 other physiological related metal cations in aqueous media. Binding induces excimer formation, providing a highly sensitive ratiometric measure of lead concentrations.     

Preparation of Magnetic-Activated Carbon Nanocomposite and Its Application for Dye Removal from Aqueous Solution

A nanocomposite of activated carbon and iron oxide was prepared and characterized by x-ray diffraction and scanning electron microscopy methods. The prepared magnetic nanocomposite can be separated easily from water by an external magnet. The prepared magnetic nanocomposite was used as adsorbent for removal of Bismarck Brown (B.B.) as a dye pollutant from water. The adsorption studies include both equilibrium and kinetic aspects, and the results were modeled with different equations. The obtained results indicate that the prepared magnetic nanocomposite of iron oxide and activated carbon is one of the best adsorbents for the removal of B.B. from aqueous solution.     

Pb2+-Containing Metal-Organic Rotaxane Frameworks (MORFs)

The metal-organic rotaxane framework (MORF) structures with the advantage of mechanically interlocking molecules (MIMs) have attracted intense interest from the chemical community. In this study, a set of MORFs (i.e., MORF-Pb-1 and MORF-Pb-2) are constructed using Pb²⁺, a tetraimidazolium macrocycle (Texas-sized molecular box; 1⁴⁺), and aromatic dicarboxylate (p-phthalate dianions (PTADAs; 2) or 2,6-naphthalene dicarboxylate dianions (3)) via a one-pot three-layer diffusion protocol. In particular, an unusual Pb…Pb weak interaction was shown in MORF-Pb-1 (charactered with distance of 3.656 Å).     

Activated Carbon/Pectin Composite Enterosorbent for Human Protection from Intoxication with Xenobiotics Pb(II) and Sodium Diclofenac

The use of enterosorbents—materials which can be administered orally and eliminate toxic substances from the gastrointestinal tract (GIT) by sorption—offers an attractive complementary protection of humans against acute and chronic poisoning. In this study, we report the results of developing a microgranulated binary biomedical preparation for oral use. It was designed with a core-shell structure based on pectin with low degree of esterification as the core, and nanoporous activated carbon produced from rice husk, AC-RH, as the shell, designated as AC-RH@pectin. The adsorption properties of the synthesized materials were studied in aqueous solutions for the removal of lead (II) nitrate as a representative of toxic polyvalent metals and sodium diclofenac as an example of a medicinal drug. The composite enterosorbent demonstrated high adsorption capacity for both adsorbates studied. Adsorption kinetics of lead and diclofenac adsorption by AC-RH, pectin, and AC-RH@pectin, fitted well a pseudo-second-order model. According to the Langmuir adsorption isotherm model, the best fitted isotherm model, the maximum adsorption capacity, q_max, of AC-RH@pectin for diclofenac and for lead (II) was 130.9 mg/g and 227.8 mg/g, respectively. Although q_max of AC-RH for diclofenac, 537.6 mg/g, and q_max of pectin for lead (II), 245.7 mg/g, were higher, the maximum adsorption capacity of AC-RH for lead (II), 52.7 mg/g, was much lower than that of the composite AC-RH@pectin and the adsorption capacity of pectin for diclofenac was negligible. Therefore, the composite material AC-RH@pectin demonstrated substantial efficiency of removing both species which potentially defines it as a more universal enterosorbent suitable for treating poisoning caused by substances of different chemical nature.     

A squaraine-based chemosensor for Hg and Pb

A novel unsymmetrical cationic squaraine dye (USqH⁺), absorbing in the near-infrared region (600-850 nm), was synthesized by reacting a semi-squaric acid derivative 3-[4-(N,N-dioctylamino)phenyl]-4-hydroxycyclobutene-1,2-dione with the squarylium dye, bis(3-methylbenzothiazol-2-ylidene)squaraine. Addition of micromolar amounts of Hg²⁺ and Pb²⁺ to solutions of USqH⁺ in dichloromethane brings about significant changes in its absorption spectrum, resulting in a change in colour of the solution from green to pink. The absorption spectrum of the dye is relatively insensitive to other environmentally relevant metal ions, making it possible to visually detect Hg²⁺ and Pb²⁺ in the presence of other metal ions. Molecular modeling of the complexes at the density functional theory (DFT) and semiempirical PM3 levels strongly suggests that the oxygen atoms are the most likely choice for cation binding. The calculations also indicate a high affinity of Hg²⁺ and Pb²⁺ toward the formation of 2:1 complexes, which is in good agreement with the experimental results.     

Adsorption of Pb(II) and Ni(II) From Aqueous Solution by a High-Capacity Industrial Sewage Sludge-Based Adsorbent

In the present study, adsorption of Ni(II) and Pb(II) from aqueous solution was investigated using activated carbon synthesized with industrial wastewater sludge. The synthesized adsorbent was analyzed using nitrogen adsorption–desorption and Fourier transfer infrared (FTIR) techniques. Batch adsorption mode was used to evaluate the effect of solution pH, contact time, adsorbent dose, initial metal ion concentration, and temperature on the adsorption capacity of the synthesized adsorbent. The kinetic data were analyzed using different kinetic models. The pseudo-second-order equation gave the best fit to the experimental data for both metal ions. The equilibrium isotherm data were analyzed using the Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm models. The results showed that the data obtained for the Ni(II) and Pb(II) adsorption are in good agreement with the Langmuir model. The Langmuir mono-layer maximum adsorption capacities for Ni(II) and Pb(II) ions were estimated to be 74.06 and 88.76 mg g^?1 at 25°C, respectively. In addition, the thermodynamic studies proved that the adsorption process of both metals could be considered endothermic.     

Synthesis and characterization of Pb(II) compounds constructed from N-tosyl-L-glutamic acid

{[Pb(tsgluo)]?·?H₂O} _n (1), [Pb₂(tsgluo)₂(phen)₂] (2), and [Pb₂(tsgluo)₂(bipy)₂] (3) (H₂tsgluo?=?N-p-tolylsulfonyl-L-glutamate, phen?=?1,10-phenanthroline, bipy?=?2,2′-pyridine) have been synthesized in the absence or presence of phen or 2,2′-bipy and structurally characterized by elemental analysis, IR, and X-ray crystallography. Single-crystal X-ray analyses reveal that tsgluo exhibits two coordination modes to link lead ions. Complex 1 gives a 2-D layer structure while 2 and 3 exhibit monomolecular structures; 3 is further connected into a double-chain structure by hydrogen bonds. Phen and 2,2′-bipy are very important for the crystal structure. Fluorescence of the compounds is also discussed.     

Poly(vinyl chloride)-membrane ion-selective bulk optode based on 1,10-dibenzyl-1,10-diaza-18-crown-6 and 1-(2-pyridylazo)-2-naphthol for Cu and Pb ions

An ion-selective bulk optode (ISBO) for sensing Cu²⁺ and Pb²⁺ ions based on plasticized poly(vinyl chloride) containing 1,10-dibenzyl-1,10-diaza-18-crown-6 (DBzDA18C6) as ionophore and 1-(2-pyridylazo)-2-naphthol (PAN) as chromoionophore was prepared. The effects of DBzDA18C6/PAN and NaTPB/PAN mole ratios on the response behavior of the ISBO were investigated. The ISBO membrane shows enhanced selectivities for Cu²⁺ (at 530 nm) and Pb²⁺ (at 467 nm) over alkali, alkaline earth and other transition metal ions. The optical selectivity coefficients were measured using the separate solution method (SSM) in the two corresponding wavelengths at pH=5. The detection limit for Cu²⁺ and Pb²⁺ are 3.2×10⁻⁷ and 1.0×10⁻⁸ M, respectively.     

Cobalt(II), nickel(II) and zinc(II) coordination compounds derived from aromatic amines

The structural and spectroscopic characterization of coordination compounds of four aromatic amines derived from benzimidazole, 2-aminobenzimidazole (L1), 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2), 2-(2-aminophenyl)-1H-benzimidazole (L3) and 6,6-dimethyl-5H-benzimidazolyl[1,2-c]quinazoline (L4) are reported. Cobalt(II) [Co(L1)₂(CH₃COO)₂] (1) and nickel(II) [Ni(L1)₂(CH₃COO)₂] (2) acetate coordination compounds of L1 are discussed. The synthesis and the X-ray crystal structure of the new 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2) is informed, together with its cobalt(II) [Co(L2)₂Cl₂] (3), [Co(L2)₂Br₂] (4) and zinc(II) [Co(L2)₂Cl₂] (5), [Zn(L2)₂Br₂] (6) coordination compounds. In these compounds the imidazolic nitrogen is coordinated to the metal center, while the ArNH₂ and the S-methylcarbodithioate groups do not participate as coordination sites. A co-crystal of L1 and L2 is analyzed. Structural analyses of the coordination compounds of L3 showed that this ligand behaves as a bidentate ligand through the aniline and the imidazole groups forming six membered rings in the cobalt(II) [Co(L3)Cl₂] (7) and zinc(II) [Zn(L3)Cl₂] (8) compounds, as well as the nickel(II) nitrate [Ni(L3)₂(H₂O)₂](NO₃)₂ (9). The quinazoline L4 was produced by insertion of one acetone molecule and water elimination in L3, its X-ray crystal diffraction analysis, as well as that of its zinc(II) coordination compound [Zn(L4)₂Cl₂] (10), are discussed.     

Solid-phase extraction of Pb2+ ion from environmental samples onto L-AC-Ag-NP by flame atomic absorption spectrometry (FAAS)

The development of a solid-phase extraction (SPE) procedure for the pre-concentration of trace amounts of Pb²⁺ ion on 2-furan-2-yl-1-furan-2-ylmethyl-1H-benzoimidazole loaded on activated carbon modified with silver nanoparticles (L-AC-Ag-NP) was presented. The metal ion retained on the sorbent was quantitatively determined via complexation with the ligand. The complexed metal ion was efficiently eluted using 10 mL of 4 mol L^?1 sulphuric acid in 10 w/v% acetone. The influences of the analytical parameters, including pH, amounts of the ligand and the solid phase, eluent conditions and sample volume, on the recoveries of the metal ion were optimised. Using the optimised parameters, the linear response of the SPE method for Pb²⁺ ion were in the ranges of 0.2–160 µg L^?1, and the detection limit for Pb²⁺ ion was 0.034 µg L^?1. The proposed method exhibits a pre-concentration factor (PF) of 80 and an enhancement factor of 30 for Pb²⁺ ion. The presented results demonstrate the successful application of the proposed method for the determination of Pb²⁺ ion in some real samples with high recoveries (>93%) and reasonable relative standard deviation (RSD < 2%).     

源自密胺基多孔聚合物的富氮微孔炭及选择性吸附CO_2

以间苯二甲醛和三聚氰胺为原料,通过Schiff碱缩合反应合成了密胺基多孔聚合物(POP),经高温炭化后得到富氮微孔炭(NMC).利用N2吸脱附和傅里叶变换红外(FTIR)光谱表征了POP和炭化后产物NMC的结构和组成,与POP相比,NMC的官能团数量减少,比表面积和微孔孔容大幅增加.元素分析表明NMC含氮量高达12.5%(w).采用体积法测定了CO2、CH4和N2在NMC上的单组分吸附平衡等温线,NMC展示出良好的CO2吸附性能,298 K、100 kPa下CO2平衡吸附量可达2.34 mmol·g-1.双位Langmuir(DSL)模型和单位Langmuir(SSL)模型分别较好地描述了CO2、CH4和N2在NMC上的吸附平衡数据,在此基础上,应用理想吸附溶液理论(IAST)预测了双组分混合气在NMC上的吸附等温线,结果表明NMC对CO2-N2和CO2-CH4有非常高的CO2吸附选择性,分别为144.9和12.8.     

Flow injection potentiometry by a new coated graphite ion-selective electrode for the determination of Pb(2+)

A new graphite coated electrode for the determination of Pb²⁺ based on a recently synthesized ionophore 1-hydroxy-2-{2-[2-(2-hydroxy-ethoxy)-ethoxy]-ethoxy methyl}-anthracene-9,10-dione (L) has been developed. The electrode was used in flow injection potentiometry by a home-made flow cell. Under both the batch and flow conditions, the electrode revealed a near Nernstian response over a wide lead ion concentration range (10⁻⁶ to 10⁻¹ M) and very low limit of detection. In flow injection potentiometry, excellent reproducibility (RSD%=0.49%), very high sampling rate (170 injections h⁻¹) and stable baseline was observed in the presence of 10⁻³ M KCl as ionic strength adjuster. The electrode showed high sensitivity and good selectivity for Pb²⁺ over a wide variety of alkali, alkali earth and transition metal ions and the electrode can be used for at least 3 months without any considerable change in potential response. The proposed sensor was successfully applied to the direct determination of lead in real samples and also used for the titrimetric determination of phosphate ions by both batch and flow injection potentiometry.     

Efficient Adsorption and Recovery of Pb(II) from Aqueous Solution by a Granular pH-Sensitive Chitosan-based Semi-IPN Hydrogel

A series of granular pH-sensitive semi-interpenetrating polymer network (semi-IPN) hydrogels based on chitosan (CTS), acrylic acid (AA) and gelatine (GE) were utilized for the adsorption and recycle of Pb(II) from aqueous solutions. The composite hydrogels have been characterized by FT-IR and TGA. The effects of contact time, pH value and initial Pb(II) concentration on the adsorption were investigated. Results indicated that the adsorption capacity of the hydrogel increased with increasing pH value and initial Pb(II) concentration, and a pH-sensitive adsorption characteristic was presented. The adsorption rate of the semi-IPN hydrogels on Pb(II) is fast with an adsorption rate constant of 14.9790 mg/(g·s), and adsorption equilibrium could be reached within 10 min. The adsorption isotherms of the hydrogels for Pb(II) could be described well by the Langmuir equation, rather than the Freundlich equation. The as-prepared hydrogels showed good reusability with 0.05 mol/l HNO₃ solutions as the desorbing agent and 0.1 mol/l NaOH solutions as the regeneration agent, respectively. After five consecutive adsorption-desorption processes, the semi-IPN hydrogel with 20 wt% GE may reach 85.26% of its initial adsorption capacity. In addition, the adsorbed Pb(II) can be quantitatively recovered by simply eluting the hydrogel with dilute HNO₃ solution, and a recovery ratio of 89.27% was reached for the semi-IPN hydrogel. The satisfactory adsorption amount is mainly derived from the chelating of functional groups (i.e. –COO^? and –NH₂) with Pb(II) ions. The hydrogel adsorbents exhibited excellent affinity for Pb(II), and can be applied to treat wastewater containing heavy metal ion and simultaneously recover the valuable metal sources.