Microwave-Assisted Extraction of Phenolic Compounds from Spent Coffee Grounds. Process Optimization Applying Design of Experiments

In this study, sustainable technology microwave-assisted extraction (MAE) in association with green solvents was applied to recover phenolic compounds from spent coffee grounds (SCGs). A design of experiments (DOE) was used for process optimization. Initially, a 2⁴⁻¹ two level Fractional Factorial Design was used and ratios “solvent to solute” and “ethanol to water” were identified as the significant experimental factors. Consequently, Central Composite Design (CCD) was applied to analyze the effects of the significant variables on the response yield, total polyphenols content (TPC), and antioxidant activity (AA) by the DPPH assay method, and quadratic surfaces to optimize those responses were generated. The values of the significant factors of 16.7 (solvent/solute) and 68.9% (ethanol/water) were optimized simultaneously the yield (%) at 6.98 ± 0.27, TPC (mg GAE/g) at 117.7 ± 6.1, and AA (µmol TE/g) at 143.8 ± 8.6 and were in excellent agreement with those predicted from the CCD model. The variations of the compositions of the lipids, caffeine, pentacyclic diterpenes, and FAME as a function of the dominant factor % ethanol in the solvent mixture were analyzed by applying NMR and GC-FID, and the results obtained confirmed their determinative significance.     

有机络合剂去除活化法生产活性炭的回收磷酸液中铁离子

用磷酸液活化活性炭,磷酸液可重复回收利用,由于木屑、炭屑等原材料的影响,用于反复活化浸渍的磷酸液中铁含量将从小于10 μg/g上升到几百μg/g,甚至更高,不能满足医药、食品等行业对活性炭中铁离子含量低的要求。对回收来的磷酸液进行除铁纯化具有一定的经济意义。探讨了一种通过用二甲胺(33%)、氢氧化钠(15%)（或氢氧化钾）、二硫化碳三种药品于一定条件下,制得的有机络合沉淀剂,常温下可将回收来的磷酸母液中铁离子除去,除铁效果显著,达到50 μg/g以下,从而使回收的磷酸液能满足医药、食品等行业用活性炭的生产之需。方法工艺简单、成本低,是一种值得推广的应用技术。     

Bioactive Compounds and Antioxidant Activity from Spent Coffee Grounds as a Powerful Approach for Its Valorization

Coffee is one of the world’s most popular beverages, and its consumption generates copious amounts of waste. The most relevant by-product of the coffee industry is the spent coffee grounds, with 6 million tons being produced worldwide per year. Although generally treated as waste, spent coffee grounds are a rich source of several bioactive compounds with applications in diverse industrial fields. The present work aimed at the analysis of spent coffee grounds from different geographical origins (Guatemala, Colombia, Brazil, Timor, and Ethiopia) for the identification of bioactive compounds with industrial interest. For this purpose, the identification and quantification of the bioactive compounds responsible for the antioxidant activity attributed to the spent coffee grounds were attempted using miniaturized solid-phase extraction (µ-SPEed), combined with ultrahigh-performance liquid chromatography with photodiode array detection (UHPLC-PDA). After validation of the µ-SPEed/UHPLC-PDA method, this allowed us to conclude that caffeine and 5-caffeoylquinic acid (5-CQA) are the most abundant bioactive compounds in all samples studied. The total phenolic content (TPC) and antioxidant activity are highest in Brazilian samples. The results obtained show that spent coffee grounds are a rich source of bioactive compounds, supporting its bioprospection based on the circular economy concept closing the loop of the coffee value chain, toward the valorization of coffee by-products.     

从速溶咖啡中提取咖啡因

学生做完从茶叶中提取咖啡因的实验,还想了解从咖啡中提取咖啡因的方法,而相关的文献极少。为了解决学生的困惑,介绍了从速溶咖啡中提取咖啡因的实验,即通过抽滤、萃取、干燥、蒸馏、升华等操作获得纯净的咖啡因。学生可以结合提供的信息,通过2种不同物质提取咖啡因方法的比较,更好地理解物质性质与实验方法、操作步骤的对应关系,从而提高对提取物质实验的认识和操作方法的理解,增强创新能力和实践能力。     

Adsorption of Carbon Dioxide on Activated Carbon

The adsorption of CO2 on a raw activated carbon A and three modified activated carbon samples B, C, and D at temperatures ranging from 303 to 333 K and the thermodynamics of adsorption have been investigated using a vacuum adsorption apparatus in order to obtain more information about the effect of CO2 on removal of organic sulfur-containing compounds in industrial gases. The active ingredients impregnated in the carbon samples show significant influence on the adsorption for CO2 and its volumes adsorbed on modified carbon samples B, C, and D are all larger than that on the raw carbon sample A. On the other hand, the physical parameters such as surface area, pore volume, and micropore volume of carbon samples show no influence on the adsorbed amount of CO2. The Dubinin-Radushkevich (D-R) equation was the best model for fitting the adsorption data on carbon samples A and B, while the Preundlich equation was the best fit for the adsorption on carbon samples C and D. The isosteric heats of adsorption on carbon samples A, B, C, and D derived from the adsorption isotherms using the Clapeyron equation decreased slightly increasing surface loading. The heat of adsorption lay between 10.5 and 28.4 kJ/mol, with the carbon sample D having the highest value at all surface coverages that were studied. The observed entropy change associated with the adsorption for the carbon samples A, B, and C (above the surface coverage of 7 ml/g) was lower than the theoretical value for mobile adsorption. However, it was higher than the theoretical value for mobile adsorption but lower than the theoretical value for localized adsorption for carbon sample D.     

蜂巢状多孔明胶制备高性能超级电容器用活性炭

近年来,以生物质为前驱体来制备碳材料因其资源丰富、廉价易得、无污染且可再生等优点而引起人们的广泛关注。本文将生物质明胶制备成呈蜂巢状的多孔结构,并以此为前驱体经碳化、活化制备活性炭。研究表明,与商品化明胶相比,由多孔明胶所制备的活性炭其比表面积(可高达3692 m~2?g1)及超级电容器性能均有明显提升。在6 mol?L~(-1) KOH水溶液中,由多孔明胶经600°C碳化、700°C KOH活化所制备的活性炭,在1 A?g~(-1)的放电容量为357 F?g~(-1),即使在100 A?g~(-1)的大电流密度下,其比电容仍可维持在227 F?g~(-1)。活性炭样品也表现出优异的循环稳定性,在10 A?g~(-1)下经7500圈循环稳定性测试后,其初始容量保持率高达93.0%。而且,以该活性炭组装的对称型超级电容器,在250、2500及25000 W?kg~(-1)的功率密度下,其能量密度分别为10.3、9.7和8.2 Wh?kg~(-1);在10 A?g~(-1)下经10000次循环后,容量保持率高达97.6%。这些研究结果表明由蜂巢状多孔明胶所制备的活性炭在高性能超级电容器中具有巨大的应用潜力。     

Study of Water Adsorption on Activated Carbons with Different Degrees of Surface Oxidation

A carbon of wood origin was oxidized with different oxidizing agents (nitric acid, hydrogen peroxide, and ammonium persulfate). The microstructural properties of the starting material and the oxidized samples were characterized using sorption of nitrogen. The surface acidity was determined using Boehm titration and potentiometric titration. The changes in the surface chemistry were also studied by diffuse reflectance FTIR. Water adsorption isotherms were measured at three different temperatures close to ambient (relative pressure from 0.001 to 0.3). From the isotherms the heats of adsorption were calculated using a virial equation. The results indicated that the isosteric heats of water adsorption are affected by the surface heterogeneity only at low surface coverage. In all cases the limiting heat of adsorption was equal to the heat of water condensation (45 kJ/mol).     

Determination of the Porous Structure of Activated Carbons Using the IAE Concept. Influence of the Local Adsorption Model

In this paper we study a method for the determination of the micropore volume distribution function of activated carbons. This method is based on the Integral Adsorption Equation concept (IAE). The micropore volume distribution function is assumed to be a Gaussian of which the parameters are unknown. These parameters are determined using adsorption isotherms of carbon dioxide on a given activated carbon (F30/470 CHEMVIRON CARBON) at 278, 288, 298, 303, 308, 318 and 328 K and for pressures up to 100 kPa. Several local adsorption models are used (Langmuir, Volmer, Fowler-Guggenheim, Hill-de Boer). The influence of the choice of the local model on the pore volume distribution function is discussed. The physical validity of this function and the performances of the different models are presented. It appears that the effect of the temperature on the adsorption isotherms is difficult to model over a wide range of relative pressure. The Hill-de Boer and the Langmuir local models are the most efficient (average errors respectively equal to 3.53% and 2.80% in the studied range of temperature and pressure). They provide the most meaningful parameters for the pore volume distribution function.     

Gd掺杂TiO2/活性炭纤维复合材料的制备及表征

以TiCl4和Gd(NO3)3·6H2O为主要原料,采用酸催化水解法制备Gd掺杂TiO2光催化剂并通过浸涂法将其负载在活性炭纤维(ACF)表面,制得Gd掺杂TiO2/ACF复合材料。 以气相苯为模型物,考察材料的光催化活性。 利用XRD、FTIR及GC-MS对催化剂的晶相结构、光谱特征等进行了表征。 结果表明,Gd掺杂能有效抑制TiO2的晶粒生长。 Gd掺杂量、浸涂次数影响TiO2/ACF光催化活性,Gd2O3掺杂质量分数为0.48%、浸涂2次的TiO2/ACF活性最高。 在苯光催化氧化后的Gd掺杂TiO2/ACF复合材料表面未发现醌类中间产物的存在。 Gd的掺入能减缓催化剂失活,光催化反应100 min后仍能表现出较高活性。     

粉末活性炭基复合材料制备及净化含油污水的性能和机制

针对粉末活性炭对亲水小分子有机物吸附效率低和固液分离速度慢的问题, 本研究以粉末活性炭(PAC)、腐植酸盐(HS)、聚合氯化铝(PACl)为原料, 通过融合法成功制备了粉末活性炭基复合材料PACMC (powdered activated carbon matrix composites), 将其作为含油污水的净化吸附剂. 扫描电子显微镜-X射线能量色散谱仪(SEM-EDS)和傅里叶红外光谱(FT-IR)等表征分析确认了PACMC的微观形貌和化学组成, 证实了PAC、HS和PACl是通过化学反应生成了PACMC. PACMC具有层状多孔结构和活性官能团, 有利于含油污水分子的传输扩散和化学吸附. 通过静态吸附实验研究了PACl、PAC和PACMC对含油污水中有机物的吸附性能, 结果表明: PACMC对含油污水中有机污染物的吸附能力是PAC和PACl的2~3倍(q_e=23.04 mg•g^‒1, C₀=300 mg•L^‒1); 当吸附时间达到120 min 时, PACMC上的活性位点与含油污水中有机污染物的结合已基本达到饱和(q_e=23.04 mg•g^‒1, C₀=300 mg•L^‒1). 溶液pH值对PACMC吸附去除含油污水中有机物的影响显著, pH=3时, 吸附效果最好(q_e=27.6 mg•g^‒1, C₀=300 mg•L^‒1); 伪二级动力学方程能很好地描述含油污水中有机物在PACMC上的吸附行为, 动力学拟合结果表明其吸附过程分多步进行, 化学吸附和内扩散均具有重要作用. 等温吸附数据符合Dubinin-Radushkevich模型, 证明其吸附机理为化学吸附. 因此, PACMC吸附含油污水的机理包括化学结合/螯合作用、疏水力作用和静电吸附作用.     

K_2CO_3活化制备花椒籽废渣的活性炭及其对对硝基苯酚的吸附性能

采用花椒籽废渣(RPS)为原料,K_2CO_3为活化剂制备了花椒籽废渣活性炭(KAC),以期实现农业废弃物的再利用。采用傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)、热重分析仪(TGA)、能量散射光谱(EDS)、X射线衍射仪(XRD)和气体吸附法等技术手段对其进行表征。分析了浸渍比(m(K_2CO_3)∶m(RPS))、浸渍时间、活化温度和活化时间对制备花椒籽废渣活性炭的影响,并且测试了花椒籽废渣活性炭对对硝基苯酚的吸附行为。研究结果表明,在浸渍比为0.8,浸渍时间为12 h,活化温度为550℃,活化时间为60min的条件下,活性炭的产率为29.3%,比表面积为1210 m~2/g,碘值为1002 mg/g,对亚甲基蓝的平衡吸附容量为362 mg/g,灰分为2.2%,水分为6.6%。对对硝基苯酚的吸附性能研究表明,293 K,pH=8.0,吸附180min后可达到吸附平衡,对硝基苯酚的吸附容量为406 mg/g,吸附可用Langmuir等温方程较好模拟,吸附为自发的放热过程。动力学研究表明该吸附符合准二级动力学模型。K_2CO_3活化法制备花椒籽废渣活性炭原料廉价,工艺简单,制得的活性炭吸附性能优异,具有较好的应用前景。     

Antibiotic Removal from the Aquatic Environment with Activated Carbon Produced from Pumpkin Seeds

Antibiotics are among the most critical environmental pollutant drug groups. Adsorption is one of the methods used to eliminate these pollutants. In this study, activated carbon was produced from pumpkin seed shells and subsequently modified with KOH. The adsorbent obtained through this procedure was used to remove ciprofloxacin from aqueous systems. Fourier Transform-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), elemental, X-ray Photoelectron Spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and Zeta analyses were used to characterize the adsorbent. The surface area, in particular, was found to be a very remarkable value of 2730 m²/g. The conditions of the adsorption experiments were optimized based on interaction time, adsorbent amount, pH and temperature. Over 99% success was achieved in removal operations carried out under the most optimal conditions, with an absorption capacity of 884.9 mg·g⁻¹. In addition, the Langmuir isotherm was determined to be the most suitable model for the adsorption interaction.     

Activated Carbon Adsorption of Some Phenolic Compounds Present in Agroindustrial Wastewater

Single solute and simultaneous experimental adsorption isotherms of three phenolic compounds: gallic acid, p-hydroxybenzoic acid and syringic acid, have been investigated at 20, 30 and 40°C, using a bituminous coal based activated carbon. Regardless of temperature, the capacity of the activated carbon used to adsorb these compounds presented the following order: syringic acid > p-hydroxybenzoic acid > gallic acid. The increase of temperature slightly favored the adsorption capacity of the phenolic compounds. In binary and ternary component adsorption, experimental data suggest that interactions between adsorbates improve the adsorption capacity of some of the phenolic acid compounds. On the contrary, at high organic concentrations, adsorbed gallic acid was partially removed from the activated carbon surface because of the presence of the other components.     

Removal of H2S from Exhaust Gas by Use of Alkaline Activated Carbon

The purpose of this research was to select an activated carbon and alkaline solution blend that generated the best H₂S adsorption on alkaline-activated carbon. RB₂ (activated carbon) impregnated with NaOH solution was shown to have the optimum H₂S removal efficiency. The optimum NaOH concentration was 50 mg per gram of carbon. H₂S adsorption via RB₂-NaOH₅₀ was five times that of a corresponding fresh-activated carbon. The adsorption equivalent of H₂S is nearly 1 (mol-H₂S/mol-AOH), therefore, H₂S + AOH AHS + H₂O was the major reaction. The H₂S adsorption isotherm corresponded to the Freundlich isotherm.     

Role of Microporosity of Activated Carbons on Their Adsorption Abilities for Phenols and Dyes

The amounts of adsorption of two commercial dyes, phenol, and 4-chlorophenol from water on activated carbons were measured at 30°C. The carbons were prepared from cane (bagasse) piths and were activated by steam. The activation temperature and time were in the ranges of 750–840°C and 2 h, respectively. It was shown that the isotherm data of all four solutes could be well fitted by the Langmuir equation under the conditions studied. The adsorption capacities of the solutes were correlated with the microporosity properties of the activated carbons including micropore volume and external surface area. Finally, the adsorption characteristics of the present carbons was compared with those prepared from various agricultural wastes.     

Competitive Adsorption of Chloroform and Iron Ion onto Activated Carbon Fiber

Chloroform in tap water has been a significant problem because it may be a carcinogenic substituent. Iron ion exists in tap water because of dissolution from iron water pipes. Iron ions in tap water cause discoloration and a bad odor. The isotherms of chloroform and iron ion adsorption onto activated carbon fibers in a single solution (chloroform or iron ion) and in a binary mixture solution (chloroform and iron ion) were investigated to estimate the competitiveness between chloroform and iron ions. The amount of adsorbed iron ions increased with increasing pore volume of the activated carbon fibers, while that of chloroform decreased. The amount of chloroform adsorbed onto the activated carbon fibers in the binary mixture solution was greater than that in the single solution. These results indicate that the adsorption of chloroform and iron ion onto activated carbon fibers could be competitive.     

萃取温度对无灰煤结构及煤基活性炭电化学性能的影响

以内蒙古褐煤为原料,N-甲基吡咯烷酮为萃取剂,在不同温度下萃取制备无灰煤,进而利用KOH活化法制备活性炭,探究萃取温度对活性炭电化学性能的影响。结果表明,无灰煤萃取温度对煤基活性炭电化学性能有显著影响。对无灰煤及原料褐煤的灰分含量,表面官能团含量和对应活性炭的比表面积、孔结构及其电化学性能进行对比发现,330℃下萃取制备出的无灰煤在碱煤质量比3∶1,活化温度650℃,活化时间2h的活化过程中具备最适宜的反应性,对应活性炭比表面积高达1 252 m~2·g~(-1),表面官能团含量适中,在3 mol·L~(-1)KOH电解液中50 mA·g~(-1)电流密度下比电容高达322 F·g~(-1),2 A·g~(-1)的电流密度下比电容保持率仍可接近90%。     

Preparation of Corn Stalk-Walnut Shell Mix-based Activated Carbon and Its Adsorption of Malachite Green

The mix-based activated carbon derived from corn stalk and walnut shell was prepared by chemical activation method using phosphoric acid as the activator. The optimized conditions for preparation were obtained by the orthogonal experiment, the characterizations of the activated carbon were performed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy(FTIR), Boehm's titration method and nitrogen adsorption. For the prepared mix-based activated carbon, the highest iodine number, methylene blue number and BET surface area are 720.5 mg/g, 195.0 mg/g and 1187 m²/g, respectively, and the pores are mainly mesopores. The mix-based activated carbon shows the higher adsorption capacity for malachite green than the raw materials, the activated carbons prepared only from corn stalk or walnut shell and the commercial activated carbon. The kinetics and thermodynamics of the adsorption can be satisfactorily described by the pseudo-second-order kinetic model and the Langmuir isotherm model, separately.     

KOH活化木屑生物炭制备活性炭及其表征

以木屑热裂解的生物质炭为原料,氢氧化钾为活化剂,采用化学活化法制备活性炭,探讨了碱炭比、活化温度和活化时间对活性炭吸附亚甲基蓝吸附值的影响。 利用N2吸附实验、XRD和FTIR等实验技术,对原料与制备活性炭的结构与性能进行了表征。 结果表明,在碱炭质量比为1.5、活化温度750 ℃、活化时间2 h的条件下,所制备的活性炭对亚甲基蓝吸附值为255 mg/g,BET总比表面积为1514 m2/g,中孔比表面积为110 m2/g,吸附总孔容为0.821 cm3/g,中孔孔容为0.117 cm3/g,吸附平均孔径为2.170 nm。     

活性炭负载杂多酸催化剂的研究进展

介绍了以活性炭为载体的负载型杂多酸催化剂的研究进展,包括制备方法、影响负载量的因素、负载催化剂的性质、吸附模型和脱附作用。总结了杂多酸在活性炭上的吸附形态研究以及杂多酸与活性炭表面含氧基团的化学键合作用的研究成果,展望了该催化剂未来的研究方向。