Adsorption removal of methyl violet from aqueous solution by chromium phosphovanadate

An effective adsorbent for methyl violet (MV), chromium phosphovanadate (named as Cr‐PV) nanomaterials, was prepared by a simple coprecipitation strategy. The microstructure and morphology of as‐synthesized Cr‐PV were characterized by SEM, X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR), respectively, which was confirmed as nanosheet shapes. The adsorption behavior for MV from aqueous solutions was systematically investigated. The kinetic and equilibrium results indicate that the adsorption process follows pseudo‐second‐order kinetic model and Langmuir isotherm, respectively. Compared with PV and commercially available activated carbon, Cr‐PV has preferable adsorption property to MV. The maximum adsorption capacity can reach 123.81 mg g^?1 at room temperature. The thermodynamic parameters such as Gibbs free energy (ΔG^ο), enthalpy (ΔH^ο), and entropy change (ΔS^ο) show that the adsorption of MV is an endothermic and spontaneous process. Moreover, the adsorptive behavior between Cr‐PV and MV is monolayer adsorption and electrostatic interaction mechanism. Cr‐PV, as a promising adsorbent with high adsorption capacity and fast adsorption rate, shows great potential for the removal of MV from wastewater.     

介孔L材料CMK-3对甲基紫的吸附性能

合成了高度有序的具有二维六方(P6mm)结构的介孔碳材料CMK-3;利用X射线衍射分析了CMK-3的晶体结构,利用氮气吸脱附(BET)试验测定了孔体积;测定了CMK-3对水溶液中甲基紫的吸附行为,考察了不同pH、温度及浓度下水溶液中甲基紫的静态吸附行为,并分析了酸性、中性、碱性条件下吸附剂对甲基紫和罗丹明B混合溶液的竞...     

Removal of methyl orange from aqueous solution using bentonite-supported nanoscale zero-valent iron

Zero-valent iron (ZVI) nanoparticles tend to agglomerate, resulting in a significant loss in reactivity. To address this issue, synthesized bentonite-supported nanoscale zero-valent iron (B-nZVI) was used to remove azo dye methyl orange (MO) in aqueous solution. Batch experiments show that various parameters, such as pH, initial concentration of MO, dosage, and temperature, were affected by the removal of MO. Scanning electron microscopy (SEM) confirmed that B-nZVI increased their reactivity and a decrease occurred in the aggregation of iron nanoparticles for the presence of bentonite (B). Using B-nZVI, 79.46% of MO was removed, whereas only 40.03% when using nZVI after reacting for 10 min with an initial MO concentration of 100 mg/L (pH=6.5). Furthermore, after B-nZVI reacted to MO, XRD indicated that iron oxides were formed. FTIR showed that no new bands appeared, and UV-vis demonstrated that the absorption peak of MO was degraded. Kinetics studies showed that the degradation of MO fitted well to the pseudo first-order model. A degradation mechanism is proposed, including the following: oxidation of iron, adsorption of MO to B-nZVI, formation of Fe(II)-dye complex, and cleavage of azo bond. Finally, the removal rate of MO from actual wastewater was 99.75% when utilizing B-nZVI.     

Removal of radiocobalt from aqueous solution by oxidized MWCNT

The study was undertaken to evaluate the feasibility of oxidized multiwalled carbon nanotube (oxidized MWCNT) for the removal of radiocobalt (⁶⁰Co) from aqueous solutions. The oxygen functional groups of oxidized MWCNT were characterized by FT-IR and XPS. Batch experiments were performed to study the sorption of cobalt as a function of contact time, solid contents, pH, ionic strength, foreign ions, and temperature. Two kinetic models viz. pseudo-first-order and pseudo-second-order were used to determine kinetic sorption parameters, and the kinetic sorption could be described more favorably by the pseudo-second-order model. The thermodynamic parameters (∆G°, ∆S°, ∆H°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on oxidized MWCNT was an endothermic and spontaneous processes. The results suggest that oxidized MWCNT can be used efficiently in the treatment of industrial effluents containing radioactive and heavy metal ions.     

Microwave assisted preparation of efficient activated carbon from grapevine rhytidome for the removal of methyl violet from aqueous solution

Grapevine rhytidome (the outer layer of bark on trunk), as an abundant and low-cost precursor, was used to prepare granular activated carbon with high surface area for the removal of methyl violet from aqueous solution. Microwave heating source was used to reduce the treatment time and energy consumption. To optimize the preparation, the effects of the different parameters, such as phosphoric acid concentration, acid/precursor weight ratio, impregnation time, microwave power, radiation time, and oven heating time on the ability of the samples for removal of methyl violet were studied. The obtained activated carbon was characterized by N₂ adsorption/desorption, SAXS, TEM and SEM methods. The adsorption of methyl violet onto the activated carbon was studied from both equilibrium and kinetic point of view and the results were compared with the commercial granular activated carbon. The rate of adsorption onto the prepared activated carbon was faster than commercial activated carbon. Different kinetic models were used to analyze the experimental kinetic data. The obtained activated carbon showed higher adsorption capacity (more than twice) for the adsorption of methyl violet in comparison with the commercial one. The equilibrium data were analyzed using different isotherm models. Adsorption was found to be maximum in the pH range 7-9.     

Removal of methylene blue from aqueous solution by graphene oxide

Graphene oxide (GO) is a highly effective absorbent of methylene blue (MB) and can be used to remove MB from aqueous solution. A huge absorption capacity of 714 mg/g is observed. At initial MB concentrations lower than 250 mg/L, the removal efficiency is higher than 99% and the solution can be decolorized to nearly colorless. The removal process is fast and more efficient at lower temperatures and higher pH values. The increase of ionic strength and the presence of dissolved organic matter would further enhance the removal process when MB concentration is high. The results indicate that GO can be applied in treating industrial effluent and contaminated natural water. The implications to graphene-based environmental technologies are discussed.     

Removal of phosphate from aqueous solution by zeolite synthesized from fly ash

Fifteen Chinese fly ashes were converted hydrothermally into zeolites, and phosphate immobilization capacity (PIC) of the synthesized zeolites and the corresponding raw fly ashes were determined using an initial phosphate concentration of 1000 mg/L. Results showed that there was a remarkable increase in PIC (from 1.2 to 7.6 times) following the synthesis process. Fractionation of immobilized phosphorus indicated that Fe+Al-P increased most significantly and consistently among all the phosphorus fractions following the conversion of fly ash to zeolite. The PIC and Ca+Mg-P were closely related to Ca content (with r values of 0.9683 and 0.9651, respectively) rather than Mg content (with r values of 0.3920 and 0.3212, respectively). The r values of PIC and Fe+Al-P with Fe content (with r values of 0.4686 and 0.6385, respectively) were higher than those with Al content (with r values of -0.7857 and -0.3770, respectively). Although calcium and iron components were mainly involved in phosphate immobilization, there was no significant change of Ca and Fe content following the conversion of fly ash to zeolite. Increase in dissociated Fe(2)O(3) and specific surface area probably accounted for the enhancement in PIC of synthesized zeolites compared with corresponding fly ashes. The PIC value of zeolites showed a significant correlation with dissociated Fe(2)O(3) (r=0.6186). The specific surface area increased 26.0-89.4 times as a result of the conversion of fly ash to zeolite. The maximum removal of phosphate occurred within different pH ranges for zeolites which were synthesized from high, medium and low calcium fly ashes and this behavior was explained by the reaction of phosphate with calcium and iron components.     

Removal of 2,4-dichlorophenol from aqueous solution by static-air-activated carbon fibers

Static-air-activated carbon fibers (ACFs) with lotus-root-like axially porous structure were used to adsorb 2,4-dichlorophenol (2,4-DCP) from aqueous solution. The adsorption isotherm was evaluated in the pH range 3.0-11.0. Results indicated that both Langmuir and Redlich-Peterson adsorption isotherms were appropriate for describing the adsorption characteristics of 2,4-DCP at various pH values and that lower pH values were favorable for adsorption. The adsorption of 2,4-DCP was controlled by the synergetic effects of pi-pi interaction and electrostatic attraction, and the former was dominant. Breakthrough curve results showed that the 2,4-DCP removal efficiency increased with an increase in the empty-bed contact time (EBCT). An EBCT of 0.660 min was sufficient for the adsorption of 2,4-DCP onto ACF, indicating a high adsorption rate. Desorption experiment results revealed that the ACF saturated with 2,4-DCP could be regenerated effectively by a 0.001 M NaOH solution.     

Removal of radiocobalt from aqueous solution by different sized carbon nanotubes

Batch adsorption technique was applied to study the adsorption of radiocobalt on multiwalled carbon nanotubes (CNTs) with deferent sizes. The aim of this work was to examine the effect of contact time, pH, solid content, foreign ions and CNT particle sizes on the removal of Co(II) ions from aqueous solutions by CNTs. The results indicated that the adsorption of Co(II) was strongly dependent on pH and the adsorption capacity was in inverse proportion to the particle sizes of CNTs. The adsorption of Co(II) was weakly affected by ionic strength and foreign ions. Ion exchange and surface complexation were the main adsorption mechanisms. The kinetics of Co(II) adsorption on CNTs was described well by pseudo-second-order model. The Langmuir and Freundlich models were applied to interpret the adsorption data. The results are important to understand the physicochemical behavior of Co(II) with CNTs, and for the application of CNTs in the preconcentration of radiocobalt from large volumes of aqueous solutions.     

生物炭去除水中四环素的研究进展

随着抗生素药物(如四环素)的大量使用,近几年抗生素的环境行为和毒性已经成为人们的研究焦点和热点.我国的地表水、地下水、市政污水、养殖废水等不同水体中都检测到了四环素等抗生素药物,引发的水生态问题受到了众多学者的广泛关注.生物炭因具有制备来源广泛且易得廉价、比表面积大、孔隙发达、官能团种类较多等优点被学者们重点关注,已有众多文献报道发现不同种生物炭对四环素的吸附具有优越的性能.本文综述了近年来不同生物质制备的生物炭对四环素的吸附影响以及不同水化条件对四环素对生物炭吸附特征的影响,并阐述了生物炭吸附四环素过程中所涉及的机理.对进一步探究生物炭对四环素吸附的影响具有一定的指导意义.     

Removal of boron from aqueous solution by clays and modified clays

In order to increase the adsorption capacities of bentonite, sepiolite, and illite for the removal of boron form aqueous solution, the clay samples were modified by nonylammonium chloride. Specific surface areas of the samples were determined as a result of N2 adsorption-desorption at 77 K using the BET method. X-ray powder diffraction analysis of the clays and modified clays was used to determine the effects of modifying agents on the layer structure of the clays. The surface characterization of clays and modified clay samples was conducted using the FTIR technique before and after the boron adsorption. For the optimization of the adsorption of boron on clays and modified clays, the effect of pH and ionic strength was examined. The results indicate that adsorption of boron can be achieved by regulating pH values in the range of 8-10 and high ionic strength. In order to find the adsorption characteristics, Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherms were applied to the adsorption data. The data were well described by Freundlich and Dubinin-Radushkevich adsorption isotherms while the fit of Langmuir equation to adsorption data was poor. It was reached that modification of bentonite and illite with nonylammonium chloride increased the adsorption capacity for boron sorption from aqueous solution.     

Removal and recovery of uranium from aqueous solution by tea waste

Experiments on the removal and recovery of U(VI) from aqueous solution by tea waste were conducted. The adsorbent was characterized by scanning electron microscope and energy dispersive spectrometer before and after the adsorption treatment. The removal of U(VI) amounts to 86.80?% at optimum pH 6. The adsorption process reaches its equilibrium in 12?h at 308?K, and the kinetic characteristic can be described by the pseudo-second-order kinetic equation. The amount of adsorption increases from 22.92 to 142.21?mg?g^?1 with the decrease of tea waste dosage from 100 to 10?mg for solution with an initial uranium concentration of 50?mg?L^?1. Desorption for the four strippants is higher than 80?%. The equilibrium data are more agreeable with Freundlich isotherm than Langmuir isotherm.     

溶剂气浮法分离水中的Zn离子的研究

以双硫腙为配体,溴化十六烷基三甲基铵（CTAB）为表面活性剂。对Zn离子在无机相中形成的Zn-双硫腙-CTAB体系的溶剂气浮进行了研究。研究表明表面活性剂与Zn离子的物质的量之比为5：1,约1h水中的锌离子去除率可达98％。0．5mol／L NaCl大大提高体系的溶剂气浮的去除率,溶剂气浮的速率随着气流速率的增加而增加,共存溶质乙醇存在会使去除率降低,有机溶剂的量对溶剂气浮影响较小,溶剂气浮过程遵从假一级动力学。考察了不同温度下溶剂气浮的回收速率,计算了该过程中的气浮表观活化能为9．037kJ／mol。     

Removal of thorium from aqueous solution by ordered mesoporous carbon CMK-3

The ability of ordered mesoporous carbon CMK-3 has been explored for the removal and recovery of thorium from aqueous solutions. The textural properties of CMK-3 were characterized using small-angle X-ray diffraction and N₂ adsorption–desorption, and the BET specific surface area, pore volume and the pore size were 1143.7 m²/g, 1.10 cm³/g and 3.4 nm. The influences of different experimental parameters such as solution pH, initial concentration, contact time, ionic strength and temperature on adsorption were investigated. The CMK-3 showed the highest thorium sorption capacity at initial pH of 3.0 and contact time of 175 min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm. The thermodynamic parameters, △G°(298 K), △H° and △S° were determined to be -0.74 kJ·mol^?1, 9.17 kJ·mol^?1 and 33.24 J·mol^?1·K^?1, respectively, which demonstrated the sorption process of CMK-3 towards Th(IV) was feasible, spontaneous and endothermic in nature. The adsorbed CMK-3 could be effectively regenerated by 0.02 mol/L HCl solution for the removal and recovery of Th(IV).     

Removal of Co(II) from aqueous solution by using hydroxyapatite

Herein, hydroxyapatite (HAP) was prepared by aqueous precipitation technique and was characterized by using FT-IR and XRD to determine its chemical functional groups and micro-structure. The removal of cobalt from aqueous solution to HAP was studied by batch technique as a function of various environmental parameters such as contact time, pH, ionic strength, foreign ions, fulvic acid (FA), and temperature under ambient conditions. The results indicated that the sorption of Co(II) on HAP was strongly dependent on pH and ionic strength. The presence of FA enhanced the sorption of Co(II) on HAP at low pH, whereas reduced Co(II) sorption on HAP at high pH. The Langmuir, Freundlich and D-R models were used to simulate the sorption isotherms at three different temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature dependent sorption isotherms indicated that the sorption process of Co(II) on HAP was spontaneous and endothermic. The sorption of Co(II) was dominated by outer-sphere surface complexation and ion exchange at low pH, whereas inner-sphere surface complexation or surface precipitation was the main sorption mechanism at high pH values. The results suggest that the HAP is a suitable material in the preconcentration and solidification of Co(II) from large volumes of aqueous solutions.     

Adsorption of methyl violet in aqueous solutions by poly(N-vinylpyrrolidone-co-methacrylic acid) hydrogels

N-vinylpyrrolidone(VP)/methacrylic acid (MAA) monomer mixtures containing different quantities of methacrylic acid were irradiated with gamma-radiation to form hydrogels. Mixtures which contain 5, 10, 15% and irradiated with 3.4 kGy were used for swelling and diffusion studies in water and solutions of methyl violet and for the adsorption of methyl violet from aqueous solutions. Diffusion of water and methyl violet within hydrogels were found to be of non-Fickian character. In the dye adsorption experiments, the effects of pH, concentration of aqueous solution of dye and the composition of hydrogels on the adsorption process were investigated. When the pH and concentration of aqueous solutions of dye and the MAA content in hydrogels increased, the adsorption increased.     

Removal of acidic dyestuffs in aqueous solution by nanofiltration

Separation of acidic dyestuffs, including Acid red 4, Acid orange 10, and Acid red 27, from aqueous solution by nanofiltration (NF) was shown to be a feasible process to accomplish an effective removal over a broad operational range. For most experiments conducted in this study, dyestuff rejections of greater than 98% were achieved. The permeate flux for experiments conducted with various dyestuffs was increased with increasing operating pressure and solution temperature. The permeability was increased and the rejection of dyestuffs was slightly decreased with increasing cross-flow velocity of solution. The effect of solution pH on the rejection of dyestuff was elucidated by the electrostatic characteristics between the species of dyestuff and the membrane surface. Maximum permeability was obtained for experiments operated in aqueous solution of pH 5, which was close to the isoelectric point of the membrane.     

Removal of zinc and mercury ions from aqueous solution by hydrous ceric oxide

The present work deals with study of uptake behavior of zinc and mercury ions by hydrous ceric oxide applying a radiotracer technique. The influence of various parameters such as concentration, temperature and pH have been examined. It was observed that the amount of zinc and mercury ions adsorbed at equilibrium increases with increase of adsorptive concentration (1.0·10⁻⁷ to 1.0·10⁻²M), temperature (303–333K) and pH (ca. 3–10). Concentration dependence data agree well with the classical Freundlich isotherm. The radiation stability of hydrous ceric oxide was also investigated by exposing it to a 11.1 GBq (Ra−Be) source associated with γ-dose of 1.72 Gy·h⁻¹ and also using a⁶⁰Co source (4.66 kGy·h⁻¹). Adsorption of these metal ions in the presence of some monovalent and divalent cations and complexing agents has also been included in the study.     

Removal and enrichment of copper ions from aqueous solution by 1,8-diaminonapthalene polymer

Microparticles of poly(1,8-diaminonapthalene) (PDAN) were prepared by chemically oxidative polymerization by (NH₄)₂S₂O₈. The effect of pH on the sorption of Cd(II), Cu(II), Ni(II), Mn(II), Zn(II) and Pb(II) on PDAN was examined by the batch procedure. PDAN showed good sorption capacity and high selectivity towards Cu(II) in comparison with the very popular chelating sorbent Chelex 100 containing iminodiacetic functional groups. The on-line preconcentration system containing the knotted reactor with the obtained polymer was examined for the sorption and desorption processes of copper ions. The applicability of this system was checked by analysis of Cu(II) content in standard reference material (NIST 1643e) and some natural water samples.     

Removal of UO2 2+ from aqueous solution by plasma functionalized MWCNTs

The study was undertaken to evaluate the feasibility of functionalized multi-walled carbon nanotubes (MWCNTs) for the removal of UO₂ ²⁺ from aqueous solutions. The MWCNTs was treated by oxygen plasma and characterized by FTIR and XPS. The characterization indicates that MWCNTs is successfully functionalized of oxygen groups such as –COOH on its surface (denote as P-MWCNTs). The sorption of UO₂ ²⁺ from aqueous solution on P-MWCNTs was studied as a function of contact time, solid contents, pH, ionic strength and temperature under ambient conditions using batch experiment. Two simplified kinetic models of pseudo-first-order and pseudo-second-order were tested to determine kinetic parameters such as rate constants, equilibrium sorption capacities and related correlation coefficients for kinetic models of the sorption process. It can be seen that the UO₂ ²⁺ sorption on P-MWCNTs could be described more favorably by the pseudo-second-order model. The thermodynamic parameters (?G°, ?S°, ?H°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of UO₂ ²⁺ on P-MWCNTs were an endothermic and spontaneous processes. The results of the present study suggest that P-MWCNTs can be used beneficially in treating industrial effluents containing radioactive and heavy metal ions.