Evaluation of kinetics and mechanism properties of CO2 adsorption onto the palm kernel shell activated carbon

Environmental Science and Pollution Research - The volumetric adsorption kinetics of carbon dioxide (CO2) onto the synthesized palm kernel shell activated carbon via single-stage CO2 activation and...     

Characterization and Cu sorption properties of humic acid from the decomposition of rice straw

Humic acid (HA) derived from rice straw decomposed for 1 (HA-1), 3 (HA-3), 6 (HA-6) and 12 (HA-12) months was characterized by potentiometric titration and solid-state cross-polarization magic-angle spinning ¹³C nuclear magnetic resonance spectroscopy (CPMAS ¹³C NMR). The sorption of Cu on examined HA was investigated using a combination of batch sorption, isothermal titration calorimetry (ITC) and sequential desorption. Results showed that the functional group content and the humification degree of HA tended to increase with increasing decomposition time especially in the latter stage of examined decomposition period. Cu sorption on HA was a rapid process that occurred within the first 1 h and the sorption capacity increased from 245.4 mmol kg⁻¹ on HA-1 to 294.6 mmol kg⁻¹ on HA-12. The sorption of Cu was endothermic, spontaneous and the randomness was increased during Cu sorption. Sorbed Cu on examined HA can be hardly released by NH₄Ac but nearly fully released by EDTA. Forming inner-sphere complexes was the main mechanism of Cu sorption on examined HA. This study could provide valuable information for a better understanding on the environmental impacts of the decomposition of organic waste.

     

风化煤中腐殖酸的提取及其性能表征

以陕西黄陵风化煤为原料,分别采用碱溶酸析、氧解法和催化法提取腐殖酸,确定提取的最佳工艺条件,并通过测定腐殖酸灰分、红外光谱、凝胶色谱和E4/E6值对提取的腐殖酸进行性能表征,考察不同的提取方法对腐殖酸的提取率及结构的影响。结果显示, 3种方法制备的腐殖酸在官能团结构方面没有明显的差异,腐殖酸中含有大量的-COOH和-CO官能团;催化法提取的腐殖酸灰分最多,分子量最大。实验得到最佳提取腐殖酸的实验方法为催化法,最佳提取工艺为催化剂选用NHPI、1∶8的固液比、0.5 mol·L-1NaOH碱液和30 min的沸水浴时间。     

Effects of production conditions on yield and physicochemical properties of biochars produced from rice husk and oil palm empty fruit bunches

Biochar is the bio-solid material produced by pyrolysis. The biochar properties are controlled by feedstock and pyrolysis variables. In this study, the impacts of these production variables on biochar yield and physicochemical properties including pH, cation exchange capacity (CEC), total organic carbon (TOC) content, surface area, and pore volume and size were investigated. Rice husk (RH) and oil palm empty fruit bunches (EFB) were used as biomass. The biochars were produced at temperature range of 300 to 700 °C, heating rate of 3 to 10 °C/min and retention time of 1 to 3 h. The pyrolysis conditions were optimized using response surface methodology (RSM) technique to maximize the values of the responses. Analysis of variance (ANOVA) of the results demonstrated that the data fitted well to the linear and quadratic equations. Temperature was found to be the most effective parameter on the responses followed by retention time and heating rate, sequentially. CEC, TOC, surface area, and pore characteristics were evaluated as biochar properties determining their sorption potential. The optimum conditions for the maximum values of the properties were temperatures of 700 and 493.44 °C and time of 3 and 1 h for RH and EFB biochars, respectively. Heating rate at 3 °C/min was found to be the best rate for both biochars. The structure of EFB biomass was more sensitive to heating than rice husk. The biomass type and the production variables were demonstrated as the direct effective factors on biochar yield and physicochemical properties.     

油茶果壳炭对油烟的吸附性能

利用油茶果壳为原料,采用直接炭化法制备油茶果壳炭,主要讨论自制油烟吸附装置中油烟入口浓度、体积空速和吸附床层高度3个因素对穿透曲线和吸附容量的影响。结果表明,在油烟浓度为50 mg/m3,体积空速为1.7 h-1,吸附剂床层高度为40 cm的条件下,最大吸附量可达到122.6 mg/g;保护作用时间随油烟浓度的升高、体积空速的增大、吸附剂床层高度的减小而变短。SEM分析表明,油茶果壳炭含有众多孔径不一的孔隙,有利于油烟这种含有多种组分污染物分子的吸附作用。     

Spectroscopic and conformational properties of size-fractions separated from a lignite humic acid

A lignite humic acid (HA) was fractionated by preparative high performance size-exclusion chromatography (HPSEC) in seven different size-fractions. The size-fractions were characterized by cross polarization (CP) magic angle spinning (MAS) (13)C NMR spectroscopy and a further analytical HPSEC elution under UV and fluorescence detection. The alkyl hydrophobic components mainly distributed in the largest molecular-size-fraction, whereas the amount of oxidized carbons increased with decreasing size of fractions. Cross polarization time (T(CH)) and proton spin-lattice relaxation time in the rotating frame (T(1rho)(H)) were measured from variable contact time (VCT) experiments. The bulk HA was characterized by the shortest T(CH) values and the longest T(1rho)(H) values which suggested, respectively, one. an aggregation of components in a large conformation that favored a fast H-C cross polarization, and, two. consequent steric hindrances that prevented fast local molecular motions and decreased proton relaxation rates. Conversely, the separated size-fractions showed longer T(CH) values and shorter T(1rho)(H) values than the bulk HA, thereby indicating that they were constituted by a larger number of mobile molecular conformations. The UV and fluorescence absorptions were both low in the large size-fractions that mainly contained alkyl carbons, whereas they increased in the olephinic- and aromatic-rich fractions with intermediate molecular-size, and decreased again in the smaller fractions which were predominantly composed by oxidized carbons. These results support the supramolecular structure of humic substances and indicate that the observed variation in conformational distribution in humic association may be used to explain environmental processes with additional precision.     

长柄扁桃核壳活性炭的制备及表征

以长柄扁桃核壳为原料采用磷酸活化法制备活性炭,分别研究了温度、时间、浸渍比和磷酸浓度对活性炭吸附性能的影响;进而采用氮气吸附曲线和SEM对最佳工艺条件下的活性炭进行了表征。结果表明,长柄扁桃核壳是一种优质的活性炭原料;当温度为400℃,活化时间2 h,浸渍比2：1,磷酸浓度60%时,得到产率为46.46%,碘吸附值和亚甲基蓝吸附值分别为1 073 mg/g、255 mg/g,比表面积高达1 740 m²/g,中孔率为73.12%的孔隙发达的高中孔率活性炭。     

椰壳颗粒活性炭活化过硫酸钠预处理促进高固污泥水解产酸性能

为探究椰壳颗粒活性炭活化过硫酸钠(PS)预处理对高固污泥厌氧发酵水解产酸性能的影响,通过调节挥发性脂肪酸(VFAs)产量、溶解性化学需氧量(SCOD)、溶解性蛋白质及多糖等指标,探究了不同剂量颗粒活性炭(GAC)与PS预处理对高固污泥产酸发酵的最佳条件。结果表明,当PS和GAC投加量分别为1.50 mmol·g⁻¹(以总固体计)和0.65 g g⁻¹(以总固体计)时,在发酵前期产酸速率相比于对照组提高了341.43%,后续发酵过程中,VFAs最大产量相比于对照组提高了28.43%。其中,乙酸作为优质碳源,其质量浓度增加了48.98%;继续增加GAC剂量时,反应器厌氧发酵性能下降,其原因可能是过量GAC会消耗已生成的SO₄⁻·,降低污泥水解作用,同时GAC表面对VFAs的吸附也导致产酸量下降。三维荧光分析表明,在产酸量较高的反应器中,氨基酸、芳香族蛋白质等溶解性有机物的质量浓度较低,这说明适量椰壳颗粒活性炭活化PS预处理方式可提高高固厌氧发酵中微生物对于水解底物的利用率,从而提高污泥的厌氧产酸性能。本研究结果可为炭活化PS预处理技术在高固污泥厌氧消化中的应用提供参考。     

The adsorption properties of microporous activated carbon prepared from pistachio nut shell for low-concentration VOCs under low-medium temperatures

Environmental Science and Pollution Research - The control of low-concentration VOCs in coal-fired flue gas is one of the research hotspots at present. In this work, K2CO3 and K2CO3-KCl were...     

Effects of mussel shell addition on the chemical and biological properties of a Cambisol

The use of a by-product of the fisheries industry (mussel shell) combined with cattle slurry was evaluated as soil amendment, with special attention to the biological component of soil. A wide number of properties related to soil quality were measured: microbial biomass, soil respiration, net N mineralization, dissolved organic carbon, dissolved organic nitrogen, dissolved inorganic nitrogen, dehydrogenase, β-glucosidase, urease and phosphomonoesterase activities. The amendments showed an enhancement of soil biological activity and a decrease of aluminium held in the cation exchange complex. No adverse effects were observed on soil properties. Given that mussel shells are produced in coastal areas as a by-product and have to be managed as a waste and the fertility constraints in the local soils due to their low pH, our research suggest that there is an opportunity for disposing a residue into the soil and improving soil fertility.     

Ganoderma sp. SYBC L48漆酶酶学性质及其对酸性红1的脱色性能

对灵芝菌Ganoderma sp. SYBC L48漆酶进行了纯化和酶学性质分析,并利用该漆酶对偶氮染料酸性红1进行脱色处理;考察了脱色体系中各因素对脱色效率的影响;采用小麦种子和水稻种子对酶处理后的染料进行了毒性测试。结果表明,以ABTS为底物时,该酶的最适pH为2.5,最适温度为60 ℃,在pH 5~9和20~60 ℃具有良好的稳定性,Co2+、Cr3+和Fe3+离子对酶活性有较强的抑制作用。在染料浓度100 mg·L-1,酶浓度0.5 U·mL-1,介体HOBT浓度0.25 mmol·L-1,pH为4,50 ℃的条件下反应30 min后,该漆酶对酸性红1的脱色率可达90.3%;1 mmol·L-1的Cr3+、Cu2+、Al3+和Ni2+存在下,漆酶仍能催化酸性红1脱色;脱色后染料的植物毒性下降。上述结果表明该漆酶在纺织废水处理中具有一定的应用前景。     

油茶果壳炭对低浓度油烟的吸附行为

利用油茶果壳直接炭化法制备油茶果壳炭,其BET比表面积和孔容积测定结果分别为1 244 m2·g-1和1.02 cm3·g-1,SEM的分析表明,油茶果壳炭含有不同孔径的孔隙和裂缝,有利于油烟这种含有复杂组分污染物分子的吸附作用;等温吸附实验结果表明,低温低油烟浓度有利于油茶果壳炭对油烟的吸附作用,吸附量可达378.79 mg·g-1,其吸附等温线符合Langmuir吸附模型,热力学参数ΔG0、ΔH0、ΔS0均为负值,表明油茶果壳炭对油烟的吸附是一个自发的放热的物理过程。     

Characterization of water reservoirs affected by acid mine drainage: geochemical,mineralogical, and biological (diatoms) properties of the water

This work presents a combination of geochemical, mineralogical, and biological data obtained in water reservoirs located in one of the most paradigmatic mining regions, suffering from acid mine drainage (AMD) problems: the Iberian Pyrite Belt (IPB). Four water reservoirs located in the Spanish sector of the IBP, storing water for different purposes, were selected to achieve an environmental classification based on the effects of AMD: two mining dams (Gossan and Águas Ácidas), a reservoir for industrial use (Sancho), and one with water used for human supply (Andévalo). The results indicated that the four reservoirs are subject to the effect of metallic loads from polluted rivers, although with different levels: Águas Ácidas > Gossan > Sancho ≥ Andévalo. In accordance, epipsammic diatom communities have differences in the respective composition and dominant taxa. The dominant diatoms in each reservoir indicated acid water: Pinnularia acidophila and Pinnularia aljustrelica were found in the most acidic dams (Gossan and Águas Ácidas, with pH <3), Pinnularia subcapitata in Sancho (pH 2.48–5.82), and Eunotia exigua in Andévalo (pH 2.34–6.15).     

Kinetic, equilibrium isotherm and thermodynamic studies of Cr(VI) adsorption onto low-cost adsorbent developed from peanut shell activated with phosphoric acid

A particular agricultural waste, peanut shell, has been used as precursor for activated carbon production by chemical activation with H₃PO₄. Unoxidized activated carbon was prepared in nitrogen atmosphere which was then heated in air at a desired temperature to get oxidized activated carbon. The prepared carbons were characterized for surface area, surface morphology, and pore volume and utilized for the removal of Cr(VI) from aqueous solution. Batch mode experiments were conducted to study the effects of pH, contact time, particle size, adsorbent dose, initial concentration of adsorbate, and temperature on the adsorption of Cr(VI). Cr(VI) adsorption was significantly dependent on solution pH, and the optimum adsorption was observed at pH 2. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to analyze the kinetic data obtained at different initial Cr(VI) concentrations. The adsorption kinetic data were described very well by the pseudo-second-order model. Equilibrium isotherm data were analyzed by the Langmuir, Freundlich, and Temkin models. The results showed that the Langmuir adsorption isotherm model fitted the data better in the temperature range studied. The adsorption capacity which was found to increase with temperature showed the endothermic nature of Cr(VI) adsorption. The thermodynamic parameters, such as Gibb’s Free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were evaluated.     

Distribution and desorption of perfluorinated compounds in fractionated sediments

This study provides particle-scale understanding of perfluorinated compounds (PFCs) distribution in sediments collected from two locations in Tianjin, China. The sediments were fractionated according to particle size and density. Even though lower density carbonaceous fractions contributed only 17.8-22.3% of the total sediment mass, they displayed stronger affinity to PFCs with much higher PFC concentrations than in the heavy fractions. Hydrophobic interaction predominated the partition of longer chain PFCs while electrostatic interaction could affect the sorption of short chain PFCs in sediment fractions. The individual PFC concentrations increased with increasing perfluorocarbon chain length, and the concentrations of perfluoroalkanesulfonates (PFSAs) in the same sediment fraction were higher than perfluorocarboxylates (PFCAs) with the same chain length. Log K(oc) was in the range of 1.70-3.80 for C5-C12 PFCAs and 1.75-2.97 for C4-C8 PFSAs. Desorption experiments indicated desorption became difficult as the chain length increased, and PFSAs were harder to be desorbed than the corresponding PFCAs.     

Characterization of metal adsorption kinetic properties in batch and fixed-bed reactors

Copper adsorption kinetic properties in batch and fixed-bed reactors were studied in this paper. The isothermal adsorption experiments showed that the copper adsorption capacity of a granular activated carbon (Filtrasorb 200) increased when ionic strength was higher. The presence of EDTA diminished the adsorption. An intraparticle diffusion model and a fixed-bed model were successfully used to describe the batch kinetic and fixed-bed operation behaviors. The kinetics became faster when the solution pH was not controlled, implying that the surface precipitation caused some metal uptake. The external mass transfer coefficient, the diffusivity and the dispersion coefficient were obtained from the modeling. It was found that both external mass transfer and dispersion coefficients increased when the flow rate was higher. Finally effects of kinetic parameters on simulation of fixed-bed operation were conducted.     

生物炭质吸附剂对硝基苯的吸附

以花生壳为生物炭质（P-BC）原料,ZnCl2为活化剂,采用化学活化法制备生物炭质吸附剂（Z-BC）,并以其吸附水中的硝基苯,考察了pH值、吸附剂投加量和吸附时间等因素对Z-BC吸附硝基苯过程的影响。分别采用吸附动力学模型和吸附等温模型对吸附动力学和等温线进行了系统分析。结果表明：pH值对吸附的影响不大,吸附剂适宜投加量为2 g·L-1,吸附平衡时间为120 min;Z-BC对硝基苯的吸附动力学过程用准一级动力学模型能很好地描述,其计算平衡吸附量与实验值相符;颗粒内扩散模型表明,吸附过程受液膜扩散与颗粒内扩散联合控制,并以颗粒内扩散为主要速率控制步骤;Langmuir吸附等温模型能更好地描述硝基苯在Z-BC上的吸附平衡;吸附热力学方程计算得到吸附焓变（ΔH）G）S）>0,表明Z-BC对水中硝基苯的吸附为放热和熵值增加的自发过程。     

Fractionation and spectroscopic properties of fulvic acid and its extract

Novel results were obtained when a fulvic acid was isolated from Acros humic acid and fractionated by traditional preparative thin-layer chromatography. Eight colorful bands were directly viewed and analyzed showing very different fluorescence and absorption properties. The fluorescence quantum yield of the bands ranged from 2% to 9.4%, significantly higher than that of natural humic substances. An aqueous fulvic acid solution was also extracted with methylene chloride (CH(2)Cl(2)) by continuous liquid-liquid extraction. The CH(2)Cl(2) extract was further fractionated by thin-layer chromatography. Eleven highly fluorescent colorful bands and six weakly fluorescent bands were observed and examined. UV-vis absorption and fluorescence (including 3D matrix) spectra and fluorescence quantum yields revealed that each band still represented a mixture of compounds. Moreover, substantial differences in optical properties were observed among bands. A single band possessed the highest fluorescence quantum yield (6%) and highest specific fluorescence (fluorescence/mass), and accounted for 21% of the total fluorescence of the extract. The mass of individual bands varied from 1.6% to 14.1% of the total materials recovered. Components of all fractions were grouped into 11 fluorophore families according to their maxima on 3D matrix fluorescence spectra. No component is dominant in the whole fulvic acid or extracted portion in terms of optical properties. Over 40 natural products are proposed for model chromophores.     

虾壳粉对水溶液中阴、阳离子型染料的吸附

采用废弃虾壳制备吸附剂处理含刚果红或亚甲基蓝的溶液。考察了温度、吸附时间、初始浓度、吸附剂投加量和初始溶液pH对吸附效果的影响并构建了去除率预测模型,并对吸附等温线、吸附动力学和吸附热力学进行系统研究。结果表明：虾壳粉对刚果红和亚甲基蓝的吸附分别在24 h和4 h时达到平衡,平衡吸附量随吸附时间、初始浓度及吸附剂投加量的增加而增大;刚果红平衡吸附量随pH升高而增大,亚甲基蓝平衡吸附量几乎不随pH变化。在15 ℃下,吸附剂投加量为1 g·L-1,刚果红吸附的最优条件为接触时间24 h、pH=4,在该条件下,虾壳粉对刚果红的饱和吸附量为276.64 mg·g-1;亚甲基蓝吸附的最优条件为接触时间4 h、pH=12,在该条件下,虾壳粉对刚果红的饱和吸附量为1.44 mg·g-1;虾壳粉对2种染料的吸附过程以物理吸附为主,符合准二级动力学方程。虾壳粉对阴离子型染料的吸附效果较优,对阳离子型染料有一定吸附性能,是一种经济高效的染料废水吸附材料。