Simultaneous Adsorption of Aqueous Pb2+, Cu2+, Zn2+, and Cd2+ Using Surfactant-Modified and Unmodified Activated Carbon in a Fixed Bed Column

The goal of this work is to improve the simultaneous removal of Pb2+, Cu2+, Zn2+, and Cd2+ ions from synthetic wastewater in a fixed bed column by incorporating sodium dodecyl sulfate (SDS) onto the surface of activated carbon made from coconut shells. The activated carbons were characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy-energy dispersive x-ray (SEM-EDX). The adsorption column dynamics were studied by varying the flow rates (5, 10 and 15 mL/min), bed heights (10, 15 and 20 cm), and initial concentrations (50, 150, and 250 mg/L). The activated carbon has a pore volume of 0.715 cm3/g and a BET-specific surface area of 1410 m2/g. Sodium dodecyl sulfate (SDS) surfactant incorporation onto the surface of the activated carbon enhances its capacity for simultaneous adsorption of Pb2+, Cu2+, Zn2+, and Cd2+ from the aqueous medium. The affinity of the heavy metals to both unmodified (AC) and modified (AC-SDS) activated carbons followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The dynamic adsorption of the column depends on the flow rate, bed height, initial metal concentration, and SDS surface modification. With a 5 mL/min flow rate, a 20 cm bed height, and a 50 mg/L initial metal concentration, a maximum break-through time of 150 minutes for the unmodified activated carbon (AC) and 180 minutes for the SDS-modified activated carbon (AC-SDS) was reached.

Distributions of chlorophyll a and carbon fixed strength of phyto-plankton in autumn of the southern Huanghai Sea waters

Chlorophyll a （Chl a） concentration and primary productivity （PP）, namely, carbon fixed strength of phytoplankton along four transects in the southern Huanghai Sea （SHS） were studied for their distribution features and controlling mechanisms based on the investigations from 17 October to 3 November 2005. The Chl a concentration in the study waters dynamically changed spatially. Surface Chl a concentrations ranged from 0.11 to 2.38 mg/m^3 with higher and lower values observed in the nutrient-laden inshore waters and central part of the SHS occupied by oligotrophic current, respectively. The vertical distribution of Chl a concentration showed a predominant pattern of subsurface concentration maximum profile. It followed the previous result of the deep dissolved oxygen concentration maximum profile, which was significantly correlated with phytoplankton and regional water mass. The primary productivity of carbon in autumn of the SHS, ranging from 95 to 1 634 rag/（ m^2· d） mainly varied with nutrient condition, especially phosphate concentration in seawater and hydrological condition. Furthermore, associating the present study results together with previous studies, the annual value of carbon fixed production of phytoplankton in the entire marginal seas of East China （including the Bohai Sea, the Huanghai Sea and the East China Sea） was estimated to be 222 Mt, which accounted for 2% of that in the global margins. Besides, it was as 16.2 times as the annual value of apparent carbon sink strength （ 13.96 Mt） in the marginal seas of East China. This multiple was different in different sea areas （ 3.0 in the Bohai Sea, 6. 7 in the Huanghai Sea and 81.6 in the East China Sea）.

Photodegradation of Methylene Blue in a Batch Fixed Bed Photoreactor Using Activated Carbon Fibers Supported TiO2 Photocatalyst

A batch fixed bed photoreactor,using felt-form activated carbon fibers(ACF)supported TiO2 photocatalyst(TiO2/ACF),was developed to carry out photocatalytic degradation of methylene blue(MB)solution.The effects of TiO2 particle size,loaded TiO2 amount,initial MB concentration,airflow rate and successive run on the decomposition rate were investigated.The results showed that photodegradation process followed a pseudo-first-order reaction kinetic law.The apparent first-order reaction constant kapp was larger than 0.047 min- 1 with half reaction time t1/2 shorter than 15 min,which was comparable to reported data using suspended Degussa P-25 TiO2 particles.The high degradation rate was mainly attributed to adsorption of MB molecules onto the surface of TiO2/ACF.The photocatalytic efficiency still remained nearly 90%after 12 successive runs,showing that successive usage of the designed photoreactor was possible.The synergic enhancement effect in combination of adsorption with ACF and photodegradation with TiO2 was proved by comparing MB removal rates in the successive degradation and adsorption runs,respectively.

Interposition fixing structure of TiO_2 film deposited on activated carbon fibers

The immobilized photocatalyst, TiO2 film supported on activated carbon fibers (TiO2/ACFs) prepared with molecular adsorption-deposition (MAD), exhibits high stability in cyclic photodegradation runs. The interposition fixing structure between TiO2 film and carbon fiber was investigated by means of SEM-EDX, XRD, XPS and FTIR, and a model was proposed to explain this structure. With SEM examination of carbon fiber surface after removing the deposited TiO2 film, a residual TiO2 super-thin film was found to exist still. By determining surface groups on ACFs, titanium sulfate (Ti2(SO4)3) in burnt remainders of the TiO2/ACFs was thought to be formed with an interfacial reaction between TiO2 film and carbon fibers. These provide some evidence of firm attachment of TiO2 film to carbon fiber surface. In the consideration of characteristics of the MAD, the deposition mechanism of TiO2 film on ACFs was proposed, and the interposition fixing structure was inferred to intercrossedly form between TiO2 film and ACFs’ surface. This structure leaded to firm attachment and high stability of the TiO2 film.

Production of single-walled carbon nanotubes from methane over Co-Mo/MgO nanocatalyst:A comparative study of fixed and fluidized bed reactors

In this study,the performances of fixed and fluidized bed reactors in the production of single-walled carbon nanotubes（SWNTs）have been investigated.In both reactors,single-walled carbon nanotubes were grown by catalytic chemical vapor decomposition（CCVD）of methane over Co-Mo/MgO nanocatalyst under two different operating conditions.The synthesized samples were characterized by TEM,TGA and Raman spectroscopy.It is found that the performance of a fluidized bed in the synthesis of carbon nanotubes is much better than that of a fixed bed.The quality of carbon nanotubes obtained from the fluidized bed was significantly higher than that from the fixed bed and the former one with the ID/IG ratio of 0.11 while the latter one with the ID/IG ratio of 0.71.Also,the yield of SWNTs in the fluidized bed was 92 wt%,while it was 78 wt%in the fixed bed.These advantages of fluidized bed reactors for the synthesis of carbon nanotubes can be attributed to more available space for the growth of carbon nanotubes and more uniform temperature and concentration profiles.

Treatment of coke plant wastewater by SND fixed biofilm hybrid system

In this article, coke plant wastewater was treated by a simultaneous nitrifying and denitrifying （SND） fixed biofilm hybrid system. The results showed that suitable parameters of the system were important for the performance of the bio-degradation system. The chemical oxygen demand （COD） removal efficiency in this system was satisfactory, higher than 94%, and ammonia nitrogen was higher than 95%. The effluent COD concentration could meet the discharge standard, except for very few situations. The results showed that a sufficient carbon source was important for making ammonia nitrogen concentration meet the discharge standard. Then the TiN removal efficiency in this system can be brought higher than 94%. Dissolved oxygen （DO） is very important to the performance of the SND bio-degradation system, and the suitable DO is about 3.5-4.0 mg/L at the forepart of reactor. In addition, the performance of the system was almost not affected by pH value. The results show that the system is feasible to treat coke plant wastewater.

水土保持碳汇内涵与测算方法

水土保持深刻改变着地表覆被和结构、土地利用方式和陆地生态系统结构等,是增强陆地碳汇能力的重要途径。以水土保持林草、工程和耕作措施为切入点,按照“机理阐述—模型构建—分类测算”的总体思路,阐明水土保持碳汇内涵,明确了水土保持碳汇途径,构建水土保持碳汇测算方法,估算全国水土保持碳汇量。结果表明:水土保持具有垂向碳增汇、横向保土固碳(减少侵蚀土壤横向输移导致的碳流失)与减蚀减碳(避免碳排放)的多重功能。2021年,全国现存水土保持措施垂向碳增汇总量为1.54亿t,对陆域碳汇的贡献约43.5%~56.5%,其中林草措施植被和土壤碳汇量超过95%。水土保持保土固碳作用显著,2021年全国水土保持措施保土固碳总量为3 040.86万t,且具有明显的累积效应和长效作用。总体来说,2021年水土保持碳增汇(不包括水土保持林草措施植被碳汇量和土壤碳汇量)和减碳量为5 115万~6 230万t CO_(2),约占到全国现有陆地生态系统碳中和总量的4%~6%,这一部分尚未纳入国家碳汇核算体系,其应是实现“双碳”目标的重要环节。

Dynamic adsorption of Xe on a fixed-bed adsorber at 77 K

In designing a fixed-bed adsorber, it is vital to understand dynamic adsorption properties of the unit. Temperature is an important effect on adsorbent performance, as the dynamic adsorption coefficients tend to increase with decreasing temperature. To minimize the volume of the fixed-bed adsorber, the dynamic adsorption characteristics of Xe were studied at 77 K by employing a variety of adsorbents under different operational conditions. The carbon molecular sieve performed better than that of activated carbon. Both operational conditions and the presence of gaseous impurities were found to affect the adsorption properties.

Examining the Effects of Common Laboratory Methods on the Sensitivity of Carbon Fiber Electrodes in Amperometric Recordings of Dopamine

Carbon fiber microelectrodes (CFEs) are useful when combined with electrochemical techniques for measuring changes in neurotransmitter concentrations. We addressed conflicting details regarding the use of CFEs. Experimental groups consisted of CFEs at different ages (1 week, 1 month, or 2 months), cleaned in solvents (isopropanol or xylene), and exposed to in vitro use (flow cell calibrations) or in vivo use (in brain tissue). In order to determine if any of these factors affect CFE sensitivity, the present study utilized fixed potential amperometry and a flow injection system to calibrate CFEs for the measurement of dopamine. The sensitivity index (nA/μM per 100 μm of exposed carbon fiber) was not affected by the age of CFEs or pre-cleaning with xylene or isopropanol. CFE sensitivity of the in vitro exposure group also did not differ from untreated CFEs, indicating the calibration process did not alter sensitivity. However, in vivo use in brain tissue did reduce sensitivity. This effect was negated and sensitivity restored by cleaning CFEs in isopropanol or xylene following in vivo brain recordings. Given that variations in CFE sensitivity can skew results, our findings can help standardize CFE use and explain discrepancies between researchers.

Carbon Dioxide/Methane Separation by Adsorption on Sepiolite

In this work, the use of sepiolite for the removal of carbon dioxide from a carbon dioxide/methane mixture by a pressure swing adsorption （PSA） process has been researched. Adsorption equilibrium and kinetics have been measured in a fixed-bed, and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained. A model based on the LDF approximation has been employed to simulate the fixed-bed kinetics, using the Langmuir equation to describe the adsorption equilibrium isotherm. The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied. The experimental results were compared with the ones predicted by the model adapted to a PSA system. Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle. These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.

Characterization of P-nitrophenol Adsorption Kinetic Properties in Batch and Fixed Bed Adsorbers

P-nitrophenol（PNP） adsorption in batch and fixed bed adsorbers was studied. The homogeneous surface diffusion model（HSDM） based on external mass transfer and intraparticle surface diffusion was used to describe the adsorption kinetics for PNP in stirred batch adsorber at various initial concentrations and activated carbon dosages. The fixed bed model considering both external and internal mass transfer resistances as well as axial dispersion with non-linear isotherm was utilized to predict the fixed bed breakthrough curves for PNP adsorption under the conditions of different flow rates and inlet concentrations. The equilibrium parameters and surface diffusivity（Ds） were obtained from separate experiments in batch adsorber. The obtained value of Ds is 4.187×1012 m2/s. The external film mass transfer coefficient（kf） and axial dispersion coefficient（DL） were estimated by the correlations of Goeuret and Wike-Chang. The Biot number determined by HSDM indicated that the adsorption rate of PNP onto activated carbon in stirred batch was controlled by intraparticle diffusion and film mass transfer. A sensitivity analysis was carried out and showed that the fixed bed model calculations were sensitive to Ds and kf, but insensitive to DL. The sensitivity analysis and Biot number both confirm that intraparticle diffusion and film mass transfer are the controlling mass transfer mechanism in fixed bed adsorption system.

PROPERTIES AND SYNTHESIS OF NEW SUPPORTS FOR IMMOBILIZATION OF ENZYMES BY COPOLYMERIZATION OF VINYLENE CARBONATE AND METHACRYLIC ACID

Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH = 6.0 similar to 7.0, vinylene carbonate (VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reverse-phase suspension polymerization and hydrophilic copolymeric supports were prepared. The properties of the supports were determined using trypsin and results show that the amount of enzymes coupled to the supports and the specific activity of immobilized trypsin are related to the content of VCA structure units, reaction time and concentration of enzyme solution, etc.

数字经济发展对黄河流域碳排放的影响研究

基于2010-2020年中国黄河流域75个地级市数据,采用固定效应模型,实证分析数字经济发展对黄河流域碳排放的影响。研究发现:数字经济发展对黄河流域碳排放的影响呈先促进后抑制的倒“U”型非线性关系;异质性分析发现数字经济发展对黄河流域中的大城市和省会城市碳排放影响呈显著的倒“U”型非线性关系;机制分析发现数字经济发展能够通过推动经济发展与促进城镇化,从而显著抑制黄河流域碳排放。

“双碳”目标下油气行业固定资产投资对碳排放的影响研究

为了厘清油气行业固定资产投资与碳排放之间的关系,本文将2002—2021年我国油气行业面板数据作为研究样本,通过构建固定效应模型实证研究了油气行业固定资产投资对碳排放的影响作用,并采用中介效应模型,运用逐步回归方法验证了油气行业固定资产投资、人均研发投入与碳排放之间的作用关系及其影响机制。研究结果表明:1)油气行业固定资产投资显著降低了碳排放比值,其影响系数为-1.913,表明通过加大油气行业的固定资产投资能够显著降低该行业的二氧化碳排放。本文在运用替换被解释变量、替换解释变量,以及增加控制变量等方法开展进一步回归分析后发现,上述检验结果依然稳健。2)人均研发投入在固定资产投资与碳排放比值之间发挥着部分中介作用,其中介效应值为24.7%。此外,油气行业的固定资产投资还显著降低了人均研发投入,而人均研发投入通过推动绿色技术创新则可以有效抑制碳排放比值。3)油气行业固定资产投资对碳排放的影响作用是短期的且影响系数较小,对主营业务收入的影响作用是长期的且影响系数较大。4)在我国油气行业的稳定增长时期与转型升级时期之内,固定资产投资对碳排放比值的影响作用具有明显的差异性。异质性检验结果表明,在油气行业的稳定增长期内,固定资产投资与碳排放比值之间并无显著的相关关系,而在油气行业的转型升级期内,固定资产投资则显著抑制了碳排放比值。

“双碳”目标引领下我国《可再生能源法》的再修改

“双碳”目标背景下,再次修改《可再生能源法》是适应产业发展变化的现实需要,也是引导产业未来健康发展、保障电力体制改革顺利进行的需要。《可再生能源法》应在立法目标的指引下,按照“法目的-法原则-法制度”的思路再次修改。其中,固定电价制度向可再生能源配额制度转型是《可再生能源法》再次修改的重点。可再生能源配额制度设计存在复杂的经验选择,涉及可再生能源配额目标的确立、配额的分配、配额的履行以及现有固定电价制度规则如何与配额制度衔接等问题,这些内容都是《可再生能源法》再次修改的重点和难点。

农地流转对种植业低碳化发展水平的影响机制研究

【目的】研究农地流转对种植业低碳化发展水平的影响机制及效应,为尽早实现农业“双碳”目标以及推进农业全面绿色转型提供经验借鉴。【方法】基于2005—2020年30个省级面板数据,从碳源减控和产业发展二元视角构建种植业低碳发展水平评价指标体系,运用熵权—TOPSIS模型测度种植业低碳化发展水平,并采用双固定效应、中介效应及工具变量模型探究农地流转对种植业低碳化发展水平的影响机制。【结果】国内种植业低碳化发展水平不高,种植业低碳化发展水平排名前5位的省份为山东、河南、广东、江苏和福建,排名后5位省份为安徽、青海、吉林、江西和内蒙古;农地流转正向驱动种植业低碳化发展水平提升;种植业化学化水平与机械化水平在农地流转影响种植业低碳化发展过程中有中介效应。【结论】通过持续推进农地制度改革、提升种植业化学物资利用效率和机械化水平、实施差异化配套政策以提升种植业低碳化发展潜力,推进中国式农业现代化绿色高效发展。

介质阻挡放电诱导固定碳基还原床低温脱除NO的研究

针对低温脱硝的技术需求,本文建立了介质阻挡放电(DBD)诱导固定碳基还原床(FCRB)负载锰催化剂的新型原位还原脱硝系统(DBD-Mn/FCRB),与单DBD和DBD-FCRB系统相比,该系统具有最佳的脱硝性能,NO转化率和N_(2)选择性可分别达到90.9%和79.9%。该系统具有较强的抗氧冲击性能和抗水性。此外,结合表面微观特性分析,提出了3种可能的脱硝反应路径。研究结果可为低温脱硝提供参考思路。

数字经济与碳减排的耦合协调及影响因素研究

在数字经济高速发展和“双碳”约束趋紧的背景下,数字经济和碳减排的融合发展无疑是实现经济发展和生态环境保护双赢的关键突破口。基于2011—2021年中国30个省份的面板数据,运用熵值法、含非期望产出的SBM模型、耦合协调度模型、固定效应模型,通过构建数字经济与碳减排两个子系统的评价指标体系,系统分析中国数字经济与碳减排耦合协调发展的现状、差异以及影响因素。结果表明:(1)数字经济发展水平整体呈现上升趋势,碳排放效率水平较为稳定,数字经济—碳减排系统的耦合协调度总体呈上升趋势,随时间的递进逐渐由失调衰退阶段向协调阶段转变;(2)数字经济—碳减排系统的耦合协调度存在较大的区域差异性,经济发达地区的耦合协调度相对更高,绝大多数省份的耦合协调度仍没有达到初级协调阶段;(3)数字经济与碳减排的耦合协调效应受到经济发展水平、产业结构、城镇化水平、环境规制以及对外开放水平的显著正向影响,该结论在通过稳健性检验后依然成立;(4)不同影响因素对数字经济—碳减排系统的耦合协调效应具有区域异质性。

优化碱酸法提纯石墨的研究

【目的】优化天然石墨提纯效果,降低酸在提纯过程中的过多使用对环境造成的影响,满足各行各业对高品质石墨的需求,实现更环保、高效的石墨提纯。【方法】以鳞片石墨为原料,采取NaOH-HCl-HF联合处理的工艺对石墨进行提纯研究,提高石墨的固定碳含量(质量分数,下同),降低石墨中的主要杂质元素如Si、Fe、Al、Cu等的含量,详细考察NaOH的用量以及焙烧温度2个关键因素对该工艺提纯效果的影响;通过扫描电子显微镜(SEM)观察石墨形貌特征,X射线荧光光谱仪(XRF)和电感耦合等离子体原子发射光谱仪(ICP)测定提纯处理前后石墨的杂质含量,X射线衍射仪(XRD)确定石墨及其灰分的晶体结构。【结果】当焙烧温度为500℃、焙烧时间为2.5h,HCl的体积与石墨的质量比为2∶1,氢氟酸的体积与石墨的质量比为2∶1时,石墨的平均固定碳含量从原来的95.3%提高到99.93%;当NaOH与石墨的质量比分别为0.5∶1和0.6∶1时,石墨的平均固定碳含量为99.91%和99.93%;考虑到成本效益等因素,确定当NaOH与石墨的质量比设定为0.5∶1时为理想工艺条件;经过提纯处理后的石墨层结构并不会出现明显的变化,基本性能不变,提纯处理后的石墨相比于提纯处理前的石墨,杂质含量明显地降低。【结论】该碱酸工艺不仅能有效地去除石墨中的杂质,盐酸和氢氟酸的组合还可以显著地提升提纯效果,可有望应用在石墨提纯处理和新能源材料领域。

喀斯特洞穴沉积物中可培养固碳和固氮细菌多样性分析

微生物固碳和固氮作用在生物地球化学循环和能量流动中具有重要作用.洞穴黑暗和寡营养极端环境中蕴藏丰富独特的微生物资源.为了解喀斯特洞穴固碳细菌和固氮细菌群落结构组成和多样性,利用9种分离培养基,分离筛选喀斯特洞穴沉积物固碳细菌和固氮细菌,并基于16S rDNA序列测定,分析分离菌株的系统发育和多样性.共分离获得230株固碳细菌,隶属于3门、16属和64种,优势属为假单胞菌属(Pseudomonas)和不动杆菌属(Acinetobacter).固碳细菌Shannon-Wiener多样性指数为3.65,Margalef丰富度指数为11.58,Pielou均匀度指数为0.88.共分离获得425株固氮细菌,分别属于3门、14属和68种,优势属为假单胞菌属、不动杆菌属和贪铜菌属(Cupriavidus).固氮细菌Shannon-Wiener多样性指数为3.43,Margalef丰富度指数为11.07,Pielou均匀度指数为0.81.此外,无碳培养基CFMD和无氮培养基NFb分离获得的菌株多样性最高.以上结果表明,荔波喀斯特洞穴沉积物中存在丰富的固碳和固氮细菌类群,这些结果为进一步研究固碳和固氮微生物在喀斯特洞穴生态系统中的功能以及农业应用提供了菌种资源.