Adsorption of oxytetracycline from aquaculture wastewater by modified carbon nanotubes: kinetics,isotherms and thermodynamics

Abstract

In the present study, lanthanum modified carbon nanotubes (La-CNTs) were prepared by the impregnation method and used as adsorbents to remove oxytetracycline (OTC) from aquaculture wastewater. La-CNTs were characterized by SEM, EDS, XRD, BET analysis. The effects of adsorbent dosage, concentration of OTC, adsorption time, pH and interfering ions on the adsorption of OTC by La-CNTs were investigated. The optimum adsorbent dosage, OTC concentration, adsorption equilibrium time and pH for OTC adsorption by La-CNTs are 0.03?g, 20?mg/L, 180?min and 7, respectively. The outcome of the kinetics studies showed a significant linear correlation between the experimental results and the quasi-second-order kinetics model. As an adsorption isotherm model, the Langmuir model showed a very good consistency with the adsorption of OTC by La-CNTs, as the maximum adsorption quantity reached 117.23?mg/g. Through the thermodynamic analysis showed that the adsorption of OTC by La-CNTs was an endothermic process of entropy increase, which occurs spontaneously. The predominant forces promoting this adsorption were van der Waals force, π-π electron donor-acceptor interaction, and electrostatic interaction.     

Elucidation of the naproxen sodium adsorption onto activated carbon prepared from waste apricot: kinetic, equilibrium and thermodynamic characterization

In this study, activated carbon (WA11Zn5) was prepared from waste apricot, which is waste in apricot plants in Malatya, by chemical activation with ZnCl(2). BET surface area of activated carbon is determined as 1060 m(2)/g. The ability of WA11Zn5, to remove naproxen sodium from effluent solutions by adsorption has been studied. Equilibrium isotherms for the adsorption of naproxen sodium on activated carbon were measured experimentally. Results were analyzed by the Langmiur, Freundlich equation using linearized correlation coefficient at 298 K. The characteristic parameters for each isotherm have been determined. Langmiur equation is found to best represent the equilibrium data for naproxen sodium-WA11Zn5 systems. The monolayer adsorption capacity of WA11Zn5 for naproxen sodium was found to be 106.38 mg/g at 298 K. The process was favorable and spontaneous. The kinetics of adsorption of naproxen sodium have been discussed using three kinetic models, i.e., the pseudo first-order model, the pseudo second-order model, the intraparticle diffusion model. Kinetic parameters and correlation coefficients were determined. It was shown that the pseudo second-order kinetic equation could describe the adsorption kinetics for naproxen sodium onto WA11Zn5. The thermodynamic parameters, such as DeltaG degrees , DeltaS degrees and DeltaH degrees, were calculated. The thermodynamics of naproxen sodium-WA11Zn5 system indicates endothermic process.     

微波多元醇法制备单分散Ni1-xZnxFe2O4/MWCNTs与磁性能

以多壁碳纳米管(MWCNTs)为模板,三乙二醇(TREG)为溶剂,采用微波多元醇法制备MWC-NTs负载组成可控的Ni1-xZnxFe2O4(x=0.4、0.5、0.6)纳米复合材料Ni1-xZnxFe2O4/MWCNTs。其结构和形貌通过XRD、SEM、TEM和EDX进行表征,用VSM测试样品的磁性,并探讨了微波功率、微波时间对镍锌铁氧体负载的影响。结果表明立方系尖晶石结构的单分散Ni1-xZnxFe2O4磁性纳米粒子均匀负载在碳纳米管表面,平均粒径约为6nm;其磁性能与镍锌铁氧体的组成有关,随着Zn含量的增加,饱和磁化强度(Ms)先增大后减小,当x=0.5时Ms达到最大值。矫顽力(Hc)都比较小,在室温下表现为超顺磁性。     

A novel,eco-friendly and green synthesis of PPAC-ZnO and PPAC-nZVI nanocomposite using pomegranate peel: Cephalexin adsorption experiments,mechanisms, isotherms and kinetics

In the present work, powdered activated carbon coated by nanoparticles ZnO and nZVI was derived from pomegranate peel extracts and finally applied for removal of cephalexin (CEX (from aqueous solutions. This experimental research was conducted discontinuously. The effects of pH of solution, reaction time, PPAC-nZVI and PPAC-ZnO composites dose, and initial concentration of cephalexin and composite recovery on process efficiency were investigated. The removal efficiency in optimal conditions for cephalexin with PPAC-nZVI and PPAC-ZnO (CEX = 50 mg L⁻¹, composite dose = 1.25 g L⁻¹, reaction time = 45 min and pH = 5) was obtained 96.06% and 94.17%, respectively. The results of the study of isotherm and absorption kinetics for both composites showed that the absorption process follows Langmuir isotherm and pseudo second-order kinetics. The present study showed that the composites could be used as an effective and bio-friendly absorbent to remove cephalexin from aqueous solutions.     

Adsorption of Reactive Red M-2BE dye from water solutions by multi-walled carbon nanotubes and activated carbon

Multi-walled carbon nanotubes and powdered activated carbon were used as adsorbents for the successful removal of Reactive Red M-2BE textile dye from aqueous solutions. The adsorbents were characterised by infrared spectroscopy, N₂ adsorption/desorption isotherms and scanning electron microscopy. The effects of pH, shaking time and temperature on adsorption capacity were studied. In the acidic pH region (pH 2.0), the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium at 298 K was fixed at 1 h for both adsorbents. The activation energy of the adsorption process was evaluated from 298 to 323 K for both adsorbents. The Avrami fractional-order kinetic model provided the best fit to the experimental data compared with pseudo-first-order or pseudo-second-order kinetic adsorption models. For Reactive Red M-2BE dye, the equilibrium data were best fitted to the Liu isotherm model. Simulated dyehouse effluents were used to check the applicability of the proposed adsorbents for effluent treatment.     

Sunflower seed shells: a novel and effective low-cost adsorbent for the removal of the diazo dye Reactive Black 5 from aqueous solutions

In this paper, the potential of two low-cost adsorbents such as sunflower seed shells (SS) and mandarin peelings (MP) in the removal of the synthetic anionic dye Reactive Black 5 (RB5) from aqueous solutions was investigated. SS led to a percentage of dye removal higher than MP (85% and 71% after 210min, respectively, for an initial RB5 concentration of 50mgL(-1) and an initial pH of 2.0). The rate of adsorption followed a pseudo-second-order kinetic model and the intra-particle diffusion was found to be the rate-controlling stage. In addition, the equilibrium data fitted well both the Freundlich and multilayer adsorption isotherm equations indicating the heterogeneity of the adsorbent surface. This was also corroborated by the SEM photographs. On the whole, the results in this study indicated that SS were very attractive materials for removing anionic dyes from dyed effluents.     

Mesoporous magnetic biochar composite for enhanced adsorption of malachite green dye: Characterization,adsorption kinetics,thermodynamics and isotherms

This study aimed to prepare a corn straw-derived biochar supported nZVI magnetic composite (nZVI/BC) and evaluate its efficiency in adsorption of malachite green dye (MG). The prepared nZVI/BC composite was characterized by XRD, FTIR, TEM, TEM-EDS, VSM, XPS, TGA, zeta potential and BET surface area. The prepared mesoporous composite showed enhanced efficiency for the adsorption of MG dye. Adsorption models and kinetic results indicated that the adsorption of MG onto nZVI/BC composite was more fitted to Langmuir isotherm and follows second order kinetics. Intraparticle diffusion model indicated that the adsorption follows a three steps mechanism. The maximum adsorption capacity of nZVI/BC composite (515.77 mg MG/g composite) was much higher than most of reported biochar adsorbents. The removal process of MG onto nZVI/BC composite does not only proceed via adsorption mechanism, but also through an oxidative degradation mechanism. The Magnetic character of the biochar enables its easy separation and reuse for many cycles.     

Kinetics and equilibrium studies of methylene blue adsorption on 2D nanolamellar Fe3O4

ABSTRACT

Nanolamellar Fe₃O₄ as magnetic adsorbents was prepared using sodium dodecyl sulfonate as a template. Thermogravimetric measurements characterisation showed that the as-synthesised product contained about 6 wt% sodium dodecyl sulfonate. The adsorption performance of nanolamellar Fe₃O₄ for the removal of organic dye from aqueous solution was evaluated using methylene blue as a model dye. The product exhibited an excellent ability to adsorb methylene blue from aqueous solutions with a maximum methylene blue removal rate of 96.8%. The adsorption kinetics can be described by a pseudo-second-order equation, and the adsorption isotherm agreed well with Langmuir adsorption equation. Furthermore, the dye saturated nanolamellar Fe₃O₄ could be regenerated using acidic ethanol solution, and the nanolamellar Fe₃O₄ showed excellent reusability. The results indicate the potential use of the adsorbent for the removal of methylene blue from aqueous solution.     

水热法制备棒状纳米氧化铁及其在碳纳米管制备中的应用

用水热法在不添加任何改性剂的条件下,以FeCl3·6H2O为原料制备出了直径在60～80nm,长度在200nm左右、均匀分散的棒状Fe2O3.将其应用于化学气相沉积法制备碳纳米管中,制备出了直径约30nm,长度在微米级的碳纳米管.对纳米氧化铁的形成机理及其在碳纳米管制备中的作用进行了讨论.     

CoFe2O4-Co3Fe7纳米粒子及CoFe2O4/多孔碳的制备及其电磁性能研究

在5% H₂+95% N₂气氛下,还原CoFe₂O₄纳米粒子制备了CoFe₂O₄-Co₃Fe₇纳米粒子;以焙烧黄麻纤维得到的多孔碳纤维为碳源用水热法将CoFe₂O₄纳米粒子负载到多孔碳中,制备出CoFe₂O₄/多孔碳。使用X射线衍射仪、扫描电子显微镜、透射电子显微镜、拉曼光谱仪、同步热分析仪等手段对材料进行表征,并使用矢量网络分析仪测量了复合材料的电磁参数和微波吸收性能。结果表明,CoFe₂O₄-Co₃Fe₇纳米粒子和CoFe₂O₄/多孔碳的微波吸收性能明显优于CoFe₂O₄纳米粒子。CoFe₂O₄-Co₃Fe₇纳米粒子的有效频宽(反射损耗<-10 dB的频率宽度)可达4.8 GHz。CoFe₂O₄/多孔碳的有效频宽可达6 GHz,覆盖了整个Ku波段(12~18 GHz)。这些材料优异的微波吸收性能,可归因于合适的介电常数、大的介电损耗、多孔结构以及介电损耗和磁损耗的协同作用。     

Pseudo second order kinetics and pseudo isotherms for malachite green onto activated carbon: comparison of linear and non-linear regression methods

Pseudo second order kinetic expressions of Ho, Sobkowsk and Czerwinski, Blanachard et al. and Ritchie were fitted to the experimental kinetic data of malachite green onto activated carbon by non-linear and linear method. Non-linear method was found to be a better way of obtaining the parameters involved in the second order rate kinetic expressions. Both linear and non-linear regression showed that the Sobkowsk and Czerwinski and Ritchie's pseudo second order model were the same. Non-linear regression analysis showed that both Blanachard et al. and Ho have similar ideas on the pseudo second order model but with different assumptions. The best fit of experimental data in Ho's pseudo second order expression by linear and non-linear regression method showed that Ho pseudo second order model was a better kinetic expression when compared to other pseudo second order kinetic expressions. The amount of dye adsorbed at equilibrium, q(e), was predicted from Ho pseudo second order expression and were fitted to the Langmuir, Freundlich and Redlich Peterson expressions by both linear and non-linear method to obtain the pseudo isotherms. The best fitting pseudo isotherm was found to be the Langmuir and Redlich Peterson isotherm. Redlich Peterson is a special case of Langmuir when the constant g equals unity.     

Fe_2O_3/ZnFe_2O_4/C复合材料的制备及其电化学性能

本文以葡萄糖作为碳源,采用溶剂热法进行原位碳包覆合成了Fe_2O_3/ZnFe_2O_4/C材料,研究了材料的结构及电化学性能。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、循环伏安扫描(CV)和恒流充放电技术对材料结构及电化学性能进行了表征。结果表明,采用此法合成的Fe_2O_3/ZnFe_2O_4/C复合材料呈现多孔结构,粒径约为250nm,经历40次循环后材料的可逆容量依然能保持在645.7mAh/g,较未包覆碳材料的电极提高了19.0%,其可逆容量和循环稳定性能得到了显著提升。     

SiO_2-MWNTs/聚乳酸复合材料的冷结晶动力学及球晶形态

为研究多壁碳纳米管(MWNTs)对聚乳酸(PLA)冷结晶动力学和球晶形态的影响,分别以PLA和表面包覆纳米SiO2并接枝硅烷偶联剂的纳米SiO2改性MWNTs(SiO2-MWNTs)为基体和改性剂,经溶液共混法制备了SiO2-MWNTs/PLA复合材料。采用DSC、偏光显微镜、Jeziorny模型和Johnson-Mehl-Avrami模型研究了复合材料的非等温冷结晶动力学和球晶形态。结果表明:SiO2-MWNTs可作为异相成核剂,能有效降低SiO2-MWNTs/PLA复合材料的冷结晶温度,提高晶核生成速率和晶体生长活化能。SiO2-MWNTs/PLA复合材料的冷结晶过程主要由成核作用控制,加入SiO2-MWNTs可同时提高复合材料的结晶速率和结晶度。冷结晶时,PLA球晶尺寸小于熔体冷却结晶时的,且SiO2-MWNTs含量对冷结晶球晶尺寸的影响远小于其对熔体冷却结晶球晶尺寸的。所得结论对优化PLA的结晶结构和性能、制备高性能PLA复合材料具有指导意义。     

Simple method for synthesis of carbon nanotubes over Ni-Mo/Al2O3 catalyst via pyrolysis of polyethylene waste using a two-stage process

Synthesis of valuable multi-walled carbon nanotubes (MWCNTs) by thermal pyrolysis of low-density polyethylene (LDPE) waste was investigated via a two-stage process. The first stage was the thermal pyrolysis of LDPE to gaseous hydrocarbons, and the second stage was the catalytic decomposition of the pyrolysis gases over Ni-Mo/Al₂O₃ catalysts. Two catalysts with the compositions of 5.2%Ni-10.96%Mo/Al₂O₃ and 10%Ni-9.5%Mo/Al₂O₃ were tested for carbon nanotubes (CNTs) formation. The catalyst containing 10%Ni showed better activity in terms of CNTs production. Accordingly, the impact of either pyrolysis or decomposition temperatures was investigated using the 10%Ni-9.5%Mo/Al₂O₃ catalyst. TEM, XRD, Raman spectroscopy, TGA, TPR, and BET analysis tools were used to characterize the fresh catalysts as well as the obtained carbon nanomaterials. TEM images proved that MWCNTs with various morphological structures were obtained at all pyrolysis and decomposition temperatures. Moreover, cup-stacked carbon nanotubes (CS-CNTs) were observed at the decomposition temperature of 600°C. MWCNTs with the best quality were produced at decomposition temperature of 750°C. The optimum pyrolysis and decomposition temperatures in terms of CNTs production were at 700 and 650°C, respectively.     

Laser-assisted preparation of C3N4/Fe2O3/Au nanocomposite: a magnetic reusable catalyst for pollutant degradation

Clean Technologies and Environmental Policy - Assorted common contaminants namely organic dyes and nitro compounds are generated by various industries and have caused alarming problems for the...     

花瓣状Fe_3O_4/Bi_2O_3复合粒子的制备及光催化活性

用共沉淀法制备的Fe3O4纳米粒子作为种子,通过水热法获得了微米尺寸的Fe3O4/Bi2O3复合粒子。X射线衍射和X光电子能谱表征结果说明复合粒子是由Fe3O4和Bi2O3组成。扫描电子显微镜照片表明复合粒子形貌基本呈规则球形,并且具有花瓣状的三维多级结构。以罗丹明B的催化降解实验为模型考察了不同反应组成、不同反应介质、不同反应温度条件下制备的复合粒子的催化活性。结果表明,当反应条件中m(Bi(NO3)3·5H2O)/m(Fe3O4)为1.9 g∶0.2 g,水作反应介质在160℃时,所制备的复合粒子催化活性最高,对罗丹明B的降解率达95.4%。降解完成后,用磁铁吸附,Fe3O4/Bi2O3很快从体系中分离,可以重新催化降解罗丹明B,实现磁场控制的循环催化。实验发现,Fe3O4/Bi2O3经6次循环利用后,对罗丹明B的降解率仍达88.5%。     

纳米Fe_3O_4/PS-EDTA功能微球的制备及对Cu~(2+)的吸附性能

以磁性纳米Fe3O4为核,利用苯乙烯(St)聚合对其进行包覆,并进一步对表面进行氯取代、乙二胺取代及氯乙酸取代反应,制备了Fe3O4/PS-EDTA纳米磁性复合微球。利用扫描电子显微镜(SEM)、X射线衍射分析(XRD)、热重(TGA)分析、傅里叶变换红外(FT-IR)光谱仪、紫外分光光度计等对Fe3O4/PSEDTA微球性能进行了表征。结果表明,EDTA有效地以化学键合方式连接到纳米磁性Fe3O4/PS表面,且粒径均匀。Fe3O4/PS-EDTA对Cu2+表现出了良好的吸附性能,饱和吸附量为98.59mg/g,吸附等温数据符合Langmuir模型,吸附动力学符合拟二级反应动力学模型。     

MgFe2O4/Fe2O3纳米粉的溶胶-凝胶法合成及电磁波吸收特性

用热分解柠檬酸盐凝胶的方法制备了MgFe2O4／Fe2O3复合纳米粉体,用综合热分析仪、X射线衍射仪、透射电镜、纳米粒度测量仪、电磁测量仪对所制备样品的结构、粒径分布、电磁波吸收特性等进行表征。结果表明,产物为平均粒径44nm的MgFe2O4和Fe2O3的混合物,在0．1、1．0和1．8GHz处tgδ（ε″＋μ″/μ′）分别为0．206、0．265及0．614。     

Heterostructure design of Fe3N alloy/porous carbon nanosheet composites for efficient microwave attenuation

The self-dissipation and attenuation capacity of materials play an important role in realizing efficient electromagnetic absorption,in this case,the roles of macroscopic composition and micro-structure should be emphasized simultaneously in the reasonable design of microwave absorbent.Given that,Fe₃N alloy embedded in two-dimensional porous carbon composites were fabricated via facile sol-gel and sacrificial template methods.Satisfactorily,the magnetic/dielectric materials combination and porous structure introduction are conductive to the optimization of impedance matching property,as result of the enhancement of microwave absorption capacity.In addition,sufficient magnetic loss capacity,strong conductivity as well as polarization attenuation bring about the outstanding microwave absorbing performance with an effective absorption bandwidth of 6.76 GHz and a minimum reflection loss value of-65.6 d B.It is believed that this work not only lay a foundation to achieve microwave response materials in a wide frequency range,but also emphasize the significant role of the component selection and structural design.     

碳纳米管负载Fe2O3催化剂的制备及其乙苯脱氢催化活性

采用FeSO4-H2O2体系对碳纳米管氧化修饰的同时,氢氧化铁被吸附在碳纳米管管壁上,然后分别通过氢气、氮气、空气在723K下处理2h,制备了碳纳米管负载的γ-Fe2O3催化剂、γ-Fe2O3和α-Fe2O3复合催化剂和非晶态Fe2O3催化剂。采用XRD、TEM和TG-DSC表征了催化剂结构,采用连续流动乙苯气相脱氢生成苯乙烯反应对催化剂性能进行评价,结果表明：热处理条件对催化剂乙苯脱氢的催化性能影响明显,碳纳米管负载的晶态Fe2O3纳米催化剂对乙苯脱氢具有高的活性与选择性。