CO2-hierarchical activated carbon prepared from coal gasification residue: Adsorption equilibrium,isotherm, kinetic and thermodynamic studies for methylene blue removal

Mineral matter in a residue(RC G) from coal gasification(CG) was removed by two-stage acid leaching. Hierarchical activated carbon(HAC) was prepared by activating RC Gwith CO_2. The performance of HAC on removing methylene blue(MB) from an aqueous solution was investigated. HAC was characterized by N_2 adsorption–desorption isotherm, Fourier transform infrared spectroscopy, and scanning electron microscopy. The results show that HAC exhibits hierarchical pore structure with high specific surface area(862.76 m~2·g~(-1)) and total pore volume(0.684 cm~3·g~(-1)), and abundant organic functional groups. The adsorption equilibrium data of MB on HAC are best fitted to the Redlich-Peterson. The kinetic data show that the pseudo-first-order model is more suitable at low MB concentration, while the advantages of the pseudo-second-orderand the Elovich models are more obvious as the concentration increases. According to the thermodynamic parameters, the HAC-MB adsorption process is spontaneous and endothermic.     

硝酸浓度对橄榄石基活性炭特性的影响(英文)

In this work we investigated the effect of nitric acid concentration on the pore structure, surface chemistry and liquid phase adsorption of olive stone based activated carbon prepared by mixing process using phosphoric acid and steam as activating agents. Chemicals and textural characterization show that the increase of HNO3 concentration increases considerably the total acidic groups but decreases specific surface area and pore volume. The study of adsorption in aqueous solutions of two organics, phenol and methylene blue, on raw and oxidized activated carbon indicates that the treatment of mixed activated carbon with different concentrations of nitric acid improves the adsorbent capacity for methylene blue at HNO3 concentrations less or equal to 2 mol·L 1, while it has a negative effect on phenol adsorption.     

Adsorption of congo red on mesoporous activated carbon prepared by CO2 physical activation

This research demonstrates the production of mesoporous activated carbon from sargassum fusiforme via physical activation with carbon dioxide. Central composite design was applied to conduct the experiments at different levels by altering three operating parameters. Activation temperature(766–934 ℃), CO_2 flow rate(0.8–2.8 L·min(~-1)) and activation time(5–55 min) were the variables examined in this study. The effect of parameters on the specific surface area, total pore volume and burn-out rate of activated carbon was studied,and the influential parameters of methylene blue adsorption value were identified employing analysis of variance. The optimum conditions for maximum methylene blue adsorption value were: activation temperature = 900 ℃, activation time = 29.05 min and CO_2 flow rate = 1.8 L·min(~-1). The activated carbon produced under optimum conditions was characterized by BET, FTIR and SEM. The adsorption behavior on congo red was studied. The effect of parameters on the adsorbent dosage, temperature, PH and initial congo red concentration was investigated. The adsorption properties of the activated carbon were investigated by kinetics. The equilibrium removal rate and maximum adsorption capacity reaches up to 94.72%, 234 mg·g-1,respectively when initial congo red concentration is 200 mg·L~(-1) under adsorbent dosage(0.8 g · L~(-1)),temperature(30℃), PH7.     

交联氧化铝-壳聚糖新杂化吸附剂的制备及去除废水中Cu(Ⅱ)(英文)

A novel biosorbent was developed by coating chitosan,a naturally and abundantly available biopolymer,on to activated alumina based on oil shale ash via crosslinking.The adsorbent was characterized by various techniques,such as Fourier transform infrared spectroscopy,scanning electron microscopy,thermogravimetric-differential thermal analysis,and X-ray photoelectron spectroscope.Batch isothermal equilibrium adsorption experiments were condcted to evaluate the adsorbent for the removal of Cu(Ⅱ) from wastewater.The effect of pH and agitation time on the adsorption capacity was also investigated,indicating that the optimum pH was 6.0.The equilibrium adsorp-tion data were correlated with Langmuir and Freundlich models.The maximum monolayer adsorption capacity of chitosan coated alumina sorbent as obtained from Langmuir adsorption isotherm was found to be 315.46 mg·g-1 for Cu(Ⅱ).The adsorbent loaded with Cu(Ⅱ) was readily regenerated using 0.1 mol?L?1 sodium hydroxide solution.All these indicated that chitosan coated alumina adsorbent not only have high adsorption activity,but also had good stability in the wastewater treatment process.     

污泥含炭吸附剂的制备及其吸附模拟烟气中汞蒸汽的应用(英文)

The carbonaceous adsorbent was prepared from mixtures of dewatered sludge and sawdust with enhanced ZnCl2 chemical activation.Characteristics of the adsorbent were studied using scanning electron microscope(SEM) ,Fourier transform infrared spectroscopy(FT-IR) ,and adsorption of nitrogen.The surface analysis showed that the carbonaceous adsorbent had good specific surface and porosity(394 m 2 ·g-1of BET surface,0.12 and 0.10 ml·g-1of microporous and mesoporous volume,respectively) .The oxygen functional groups such as OH,C O and C O were found on the surface by FTIR and XPS(X-ray photoelectron spectroscopy) .The adsorption of elemental mercury(Hg0) on the carbonaceous adsorbent was studied in a fixed bed reactor.The dynamic adsorption capacity of carbonaceous adsorbent increased with influent mercury concentration,from 23.6μg·g-1at 12.58μg·m-3to 87.9μg·g-1at 72.50μg·m-3,and decreased as the adsorption temperature increased,from 246 μg·g-1 at 25°C to 61.3μg·g-1 at 140°C,when dry nitrogen was used as the carrier gas.The carbonaceous adsorbent presented higher dynamic adsorption capacity than activated carbon,which was 81.2μg·g-1and 53.8μg·g-1respectively.The adsorption data were fitted to the Langmuir adsorption model.The physical and chemical adsorption were identified on the adsorbent.     

不同膨润土对模拟酒溶液中蛋白质的吸附

The adsorption of protein from model wine was investigated under different temperatures, pH values, contact times, and concentrations of ethanol, by certain bentonites. The results showed that ethanol molecules could broaden the protein molecules＇ channel to the interlayer of bentonite, and the maximum protein adsorption amount occurred under an ethanol concentration of 12% （by volume） and a pH value of 3.56. The increased single point Brunauer-Emmitt-Teller （BET） surface area （SBET） and adsorption pore volume （VAds） suggested a larger amount of active adsorption sites of the bentonite surface and a wider protein channel from the surface to the inner adsorption sites of bentonite, respectively. At the same time, higher methylene blue test （MBT） and swelling index （Sw） indicated that it was easy for the entrance of water and the absorbance of protein. Higher temperature was found favorable to eliminate more proteins and it took about 20 to 40min to arrive at the maximum adsorption.     

Characterization and adsorption behaviors of a novel synthesized mesoporous silica coated carbon composite

A novel mesoporous silica coated carbon composite(denoted SEG) with hierarchical pore structure has been successfully prepared in an aqueous solution that contains triblock copolymer template, aluminum chloride, siliceous source and expanded graphite. Textural property and morphology of the SEG composite were characterized by the combination of X-ray diffraction, N_2 adsorption–desorption, scanning electron microscopy,transmission electron microscopy and Fourier transform infrared measurements. Results show that mesoporous silica is steadily and uniformly grown on the surface of the graphite slices and the thickness of the silica layer can be finely tuned according to the silica/C molar ratio in the initial reaction solution. This newly synthesized SEG composite shows greatly increased adsorption capacity to methylene blue than the pristine expanded graphite in the batch tests. Both Langmuir and Frendlich models were further used to evaluate the adsorption isotherms of methylene blue over expanded graphite and SEG samples with different silica contents. Finally, pseudosecond-order model was used to describe the kinetics of methylene blue over expanded graphite and the silica-carbon composites.     

Surface modification of polypiperazine-amide membrane by self-assembled method for dye wastewater treatment☆

Polypiperazine-amide membranes were modified with poly(ethyleneimine) (PEI) by self-assembled method, through which PEI molecules were fixed on the membrane surface by ionic interaction. In the experiments, the PEI concentration ranged from 50 to 2000 mg·L?1 while the depositing time was fixed at 20 min. The results showed that low PEI concentration resulted in a slight increase of pure water flux, which was attributed to the enhanced membrane surface hydrophilicity. The PEI adsorption on membrane surface had less effect on the re-jections to neutral PEG and sucrose, but improved the rejections to divalent cationic ions and methylene blue as the result of reversion of the membrane surface charge from negative to positive according to the XPS analysis and zeta potential measurements. The membrane modified at PEI=1500 mg·L?1 exhibited high rejection to methylene blue (MB) and is potential to be applied in the treatment of effluents containing positively charged dyes.     

Interfacial potassium induced enhanced Raman spectroscopy for single-crystal TiO2 nanowhisker

Structural control and element doping are two popular strategies to produce semiconductors with surface enhanced Raman spectroscopy(SERS) properties. For TiO_2 based SERS substrates, maintaining a good crystallinity is critical to achieve excellent Raman scattering. At elevated temperatures(N600 °C), the phase transition from anatase to rutile TiO_2 could result in a poor SERS performance. In this work, we report the successful synthesis of TiO_2 nanowhiskers with excellent SERS properties. The enhancement factor, an index of SERS performance, is 4.96 × 10~6 for methylene blue molecule detecting, with a detection sensitivity around 10~(-7) mol·L~(-1).Characterizations, such as XRD, Raman, TEM, UV–vis and Zeta potential measurement, have been performed to decrypt structural and chemical characteristics of the newly synthesized TiO_2 nanowhiskers. The photo absorption onset of MB adsorbed TiO_2 nanowhiskers was similar to that of bare TiO_2 nanowhiskers. In addition, no new band was observed from the UV–vis of MB modified TiO_2 nanowhiskers. Both results suggest that the high enhancement factor cannot be explained by the charge-transfer mechanism. With the support of ab initio density functional theory calculations, we reveal that interfacial potassium is critical to maintain thermal stability of the anatase phase up to 900 °C. In addition, the deposition of potassium results in a negatively charged TiO_2 nanowhisker surface, which favors specific adsorption of methylene blue molecules and significantly improves SERS performance via the electrostatic adsorption effect.     

Adsorption of Hg(Ⅱ) from aqueous solution using thiourea functionalized chelating fiber

A fast and selective adsorbent for Hg(II) from aqueous solutions using thiourea(TU) functionalized polypropylene fiber grafted acrylic acid(PP-g-AA),PP-g-AA-TU fibers,was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The adsorption behavior of the functionalized chelating fibers for Hg(II) was investigated by static adsorption experiments,and the effects of some essential factors on adsorption of Hg(II) were examined,such as pH,initial concentration,adsorption time,coexisting cations,and temperature.The results showed that the adsorptive equilibrium could be achieved in 10 min,and the equilibrium adsorption quantity of PP-g-AA-TU fibers was 20 times that of PP-g-AA fibers.The PP-g-AA-TU fibers showed a very high adsorption rate and a good selectivity for Hg(II) over a wide range of p H.The adsorption isotherm can be well described with Langmuir model,with the maximum adsorption capacity for Hg(II) up to52.04 mg·g~(-1)and the removal of Hg(II) more than 97%.The kinetic data indicate that the adsorption process is best-fitted into the pseudo-second-order model.     

新型炭黑材料对亚甲基蓝吸附性能的研究

研究了XC-72型炭黑材料对亚甲基蓝的吸附。实验结果表明：亚甲基蓝在XC-72上的吸附在3h达到平衡,吸附行为符合拟二级动力学方程和Langmuir方程。当温度为20％,pH为6．5时,最大吸附量为40．11mg·g^-1。溶液pH值的升高有利于提高吸附效果。XC-72对亚甲基蓝的吸附是一个自发熵增的吸热过程。     

电子废弃物中银的生物吸附研究

研究了生物吸附剂壳聚糖和丝胶在单一Ag+体系、二组分体系(Ag+-Cu2+)及某废电路板四组分体系(Ag+-Cu2+-Zn2+-Ni2+)中对Ag+的吸附性能。结果表明,在单一Ag+溶液中,丝胶对Ag+的吸附容量(1.5 mmol/g)优于壳聚糖(0.9 mmol/g);在四组分体系(Ag+-Cu2+-Zn2+-Ni2+)中,壳聚糖和丝胶对Ag+具有选择性吸附,且壳聚糖选择性(SelAg=2.16)优于丝胶(SelAg=0.91)。吸附动力学研究表明,液膜扩散为吸附过程的主控步骤。     

Synthesis of activated carbon from spent tea leaves for aspirin removal

Adsorption capacity of activated carbon prepared from spent tea leaves(STL-AC) for the removal of aspirin from aqueous solution was investigated in this study. Preliminary studies have shown that treatment with phosphoric acid(H_3PO_4) increased removal efficiency of STL-AC. Characterizations on STL-AC revealed excellent textural properties(1200 m~2·g~(-1), 51% mesoporosity), as well as distinctive surface chemistry(1.08 mmol·g~(-1) and 0.54 mmol·g~(-1) for acidic and basic oxygenated groups, pH_(pzc)= 2.02). Maximum removal efficiency of aspirin observed was 94.28% after 60 min when the initial concentration was 100 mg·L~(-1), 0.5 g of adsorbent used,pH 3 and at a temperature of 30 ℃. The adsorption data were well fitted to the Freundlich isotherm model and obeyed the pseudo-second order kinetics model. The adsorption of aspirin onto STL-AC was exothermic in nature(ΔH~Θ=~(-1)3.808 k J·mol~(-1)) and had a negative entropy change, ΔS~Θ(-41.444 J·mol~(-1)). A negative Gibbs free energy, ΔG~Θ was obtained indicating feasibility and spontaneity of the adsorption process. The adsorption capacity of AC-STL(178.57 mg·g~(-1)) is considerably high compared to most adsorbents synthesized from various sources, due to the well-defined textural properties coupled with surface chemistry of STL-AC which favors aspirin adsorption. The results demonstrate the potential of STL-AC as aspirin adsorbent.     

山竹壳活性炭吸附亚甲基蓝性能研究

以山竹壳为原料,采用磷酸—硫酸活化法制备了比表面积为1730m~2·g~(-1)的活性炭。研究了山竹壳活性炭吸附亚甲基蓝的吸附性能,考察了亚甲基蓝溶液的pH、不同初始浓度、吸附时间、温度等条件对吸附效果的影响。应用准一级动力学方程、准二级动力学方程模拟了山竹壳活性炭吸附亚甲基蓝的动力学过程,结果表明准二级动力学方程适合描述整个吸附过程。用Langmuir和Freundlich模型模拟吸附等温线,Langmuir方程更适合描述此吸附过程,在298K下最大单层吸附量为526.31mg·g~(-1)。计算了吉布斯自由能(ΔG~0)、焓变(ΔH~0)、熵变(ΔS~0)等热力学参数,ΔG~0、ΔH~0、ΔS~0均小于0,说明此吸附过程是一个自发进行的、放热的、趋于有序的吸附过程。     

Silk Sericin Enrichment through Electrodeposition and Carbonous Materials for the Removal of Methylene Blue from Aqueous Solution

The recycling and reuse of biomass waste for the preparation of carbon-based adsorbents is a sustainable development strategy that has a positive environmental impact. It is well known that a large amount of silk sericin (SS) is dissolved in the wastewater from the silk industry. Utilizing the SS instead of discharging it into the environment without further treatment would reduce environmental and ecological problems. However, effective enrichment of the SS from the aqueous solution is a challenge. Here, with the help of carboxymethyl chitosan (CMCS), which can form a gel structure under low voltage, an SS/CMCS hydrogel with SS as the major component was prepared via electrodeposition at a 3 V direct-current (DC) voltage for five minutes. Following a carbonization process, an SS-based adsorbent with good performance for the removal of methylene blue (MB) from an aqueous solution was prepared. Our results reveal that the SS/CMCS hydrogel maintains a porous architecture before and after carbonization. Such structure provides abundant adsorption sites facilitating the adsorption of MB molecules, with a maximum adsorptive capacity of 231.79 mg/g. In addition, it suggests that the adsorption is an exothermic process, has a good fit with the Langmuir model, and follows the intra-particle diffusion model. The presented work provides an economical and feasible path for the treatment of wastewater from dyeing and printing.     

木焦油基活性碳的制备及其对亚甲基蓝的吸附性能研究

木焦油是木质生物质材料的高温裂解产物。以木焦油为碳源,以甲醛化处理后的木焦油为前体,通过碳化-活化制备木焦油基活性碳材料。并以制备的木焦油基活性碳为吸附剂,研究了其对模拟水体中亚甲基蓝的吸附性能。结果表明,以木焦油为前驱体经高温碳化活化制备的多孔活性碳,比表面积可达1373Sm_²?g_^-1,表面含有丰富的含氧官能团。木焦油基活性碳对亚甲基蓝具有良好的吸附性能,准二级动力学模型能更准确的描述木焦油基活性碳吸附亚甲基蓝的动力学过程。吸附等温线更符合Langmuir等温吸附模型,木焦油基活性碳对亚甲基蓝的最大吸附容量可达559 mg?g_^-1。热力学分析表明亚甲基蓝在木焦油基活性碳上的吸附是放热和自发的。利用木焦油制备的活性碳材料对亚甲基蓝具有较高的吸附容量,是一种具有潜在应用前景的吸附材料。     

一步法制备富氧木质素活性炭及其亚甲基蓝吸附性能

以硫酸盐造纸黑液木质素为原料,分别采用磷酸活化和磷酸、硫酸混合酸活化制备了两类不同结构的木质素活性炭,对其进行了扫描电镜（SEM）、红外光谱（FTIR）、氮气吸附脱附、元素分析和Boehm酸值滴定等表征分析,并将制备的活性炭应用于模拟亚甲基蓝（MB）染料废水的吸附。结果表明,混合酸活化制备的木质素活性炭比单独磷酸活化的木质素活性炭的比表面积、总孔体积、介孔体积、氧含量分别增加了27.9%、26.4%、29.3%和29.2%,并且孔径分布更趋集中。混合酸活化活性炭在pH为2~9的范围内对亚甲基蓝均有优异的吸附性能,最大饱和吸附量达到1118.90 mg·g^-1,比磷酸活化木质素活性炭的吸附量增加了20.3%,表现出良好的吸附性能。吸附速率快,吸附过程遵循Langmuir等温线和伪二级动力学方程,颗粒内扩散不是唯一的决速步骤。     

Effect of the chelating agents on bio-sorption of hexavalent chromium using Agave sisalana fibers

The current work is focused on the study of the bio-sorption of hexavalent chromium from aqueous solution using sisal natural fiber(Agave sisalana) treated by various chelating agents(ligands) such as urea(UR),thiocarbamide(TC), ethylenediaminetetraacetic acid(EDTA), and diphenyl carbazide(DCZ). The fiber treatments were investigated using Fourier Transform Infrared Spectroscopy(FTIR) and Scanning electron microscope(SEM). The kinetics of chromium bio-sorption was studied in batch presses under the effect of some physicochemical factors such as the nature of chelating agent(F@UR, F@TC, F@DCZ, and F@EDTA),adsorbent dose(2–10 g·L~(-1)), chromium initial concentration(100–500 mg·L~(-1)), solution pH(1–6), and batch temperature(20 ℃–50 ℃). This study resulted in an optimum adsorption at a chromium initial concentration of 100 mg·L~(-1), at pH 2, and at 20 ℃. The obtained results showed clearly that the treatment with chelating agent boosts the adsorptive capacity of A. sisalana fibers Cr(VI) 10.9 mg·g~(-1) to 58.6 mg·g~(-1). The modeling study showed that the adsorption kinetics obey the pseudo-second-order model, with an R2 in the range of 0.991 and 0.999. The bio-sorption isotherms followed the Langmuir model; the maximum uptake capacity of(F@N, F@UR,F@TC, F@DCZ, and F@EDTA) was found to be respectively, 12.3 mg·g~(-1), 25.33 mg·g~(-1), 28.73 mg·g~(-1),42.54 mg·g~(-1), and 61.45 mg·g~(-1). The determined adsorption thermodynamics parameters such as enthalpy,free energy, and entropy showed that the adsorption process is exothermic, spontaneous, and has a stable configuration.     

Removal of methylene blue from aqueous solutions by using cold plasma‐ and formaldehyde‐treated onion skins

In this paper, the use of cold plasma‐treated and formaldehyde‐treated onion skins as a biosorbent has been investigated to remove methylene blue dye from aqueous solutions. The surface characteristics of the treated onion skins were investigated using Fourier Transform–infrared spectroscopy. The influence of process variables such as adsorbent dosage, initial dye concentration and pH were studied. Equilibrium isotherms were analysed by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The results indicated that the data for adsorption of methylene blue onto onion skins fitted well with the Langmuir isotherm model. The sorption capacities for cold plasma‐treated and formaldehyde‐treated onion skins by Langmuir isotherm were found to be 250 and 166.67 mg/g, respectively. The equilibrium time was found to be 150 min for 50 mg/l dye concentrations. The maximum removals for cold plasma‐treated and formaldehyde‐treated onion skins obtained were 90.94 and 95.54% at natural pH 10.0 for adsorbent doses of 0.15 g/200 ml, respectively. The rates of sorption were found to conform to pseudo‐first‐order kinetics. Results indicated that onion skins could be used as a biosorbent to remove methylene blue dye from contaminated waters.     

Dyeing properties of silk produced by silkworms reared on artificial and mulberry leaf diets

The dyeing properties were investigated for silk proteins produced by silkworms reared entirely on an artificial diet (A) and a mulberry leaf diet (M). The dyeing experiments were carried out with CI acid orange 7 at pH 3.9 and 60°C. The sericin contents of the A and the M raw silk samples were determined to be 26.0% and 23.7%, respectively. The equilibrium dye uptake and the dyeing rate of the A silk fibroin were almost the same as those of the M silk fibroin. The equilibrium dye uptake on each silk sericin was 3–4 times higher than that of the silk fibroin. On the other hand, the equilibrium dye uptake of the A silk sericin was higher than that of the M silk sericin, but the dyeing rate of the former was slower than that of the latter.