Synthesis of graphene oxide decorated with strontium oxide (SrO/GO) as an efficient nanocomposite for removal of hazardous ammonia from wastewater

ABSTRACT

In this research, graphene oxide decorated with strontium oxide (SrO/GO) is introduced as a new adsorbent material for the efficient removal of ammonia from industrial wastewater. The new adsorbent was thoroughly studied in terms of morphology, crystallography and chemical composition using characterization techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and zeta potential analysis. Several parameters such as pH, adsorbent dosage, contact time, and ammonia initial concentration were investigated and optimized. Ammonia adsorption onto SrO/GO was validated with kinetics and adsorption isotherms by adopting different models. The results revealed that ammonia adsorption kinetic was of pseudo-second order (R² = 0.999) implying that chemisorption behavior and the equilibrium isotherm follows Langmuir model. This behavior shows a high maximum monolayer sorption capacity of 90.1 mg g^?1 at pH equal to 7 and contact time of 120 min pointing out the synergism advantageous effect. The abundant oxygen functional groups on the graphene oxide surface and the integrated Sr-O nanoparticles could efficiently interact with ammonia species creating a surface for more favorable and efficient removal of ammonia.     

Removal of methylene blue (aq) using untreated and acid‐treated eucalyptus leaves and GA‐ANN modelling

In the present batch study, eucalyptus leaves (EUL), H₂SO₄‐treated eucalyptus leaves (SEUL), and H₃PO₄‐treated eucalyptus leaves (PEUL) are used as bio‐adsorbents for the removal of methylene blue (MB). The bio‐adsorption is executed to inspect the results of the variation between different experimental variables such as pH (2–10), adsorbent dose (1–10 g/L), contact time (5–360 min), and temperature (298–318 K) on the bio‐adsorption of MB. The Langmuir isotherm (R² = 0.99) fitted adequately to the bio‐adsorption data for the initial MB concentrations of 10–300 mg/L. It is also necessary to mention that the MB bio‐adsorption occurred in the order of a monolayer on the EUL, SEUL, and PEUL. The bio‐adsorption kinetics have been fitted by the pseudo‐second‐order model (R² ≥ 0.99) for various MB concentrations. The maximum bio‐adsorption capacity was 194.34 mg/g and was achieved for the H₃PO₄‐treated eucalyptus leaves (PEUL). These results showed that EUL, SEUL, and PEUL may be utilized as a favourable low‐cost bio‐adsorbent to eliminate MB from aqueous solutions. With safe disposal methods in mind, this investigation has revealed the eco‐friendliness of the bio‐adsorbents. A prediction of the removal percentage of methylene blue using a genetic algorithm (GA) from the data collected from the experiment has also been tested. The results related to the prediction using the GA‐ANN are accurate.     

EFFECT OF TEMPERATURE ON THE ADSORPTION OF METHYLENE BLUE DYE ONTO SULFURIC ACID–TREATED ORANGE PEEL

The present study explains the preparation and application of sulfuric acid–treated orange peel (STOP) as a new low-cost adsorbent in the removal of methylene blue (MB) dye from its aqueous solution. The effects of temperature on the operating parameters such as solution pH, adsorbent dose, initial MB dye concentration, and contact time were investigated for the removal of MB dye using STOP. The maximum adsorption of MB dye onto STOP took place in the following experimental conditions: pH of 8.0, adsorbent dose of 0.4 g, contact time of 45 min, and temperature of 30°C. The adsorption equilibrium data were tested by applying both the Langmuir and Freundlich isotherm models. It is observed that the Freundlich isotherm model fitted better than the Langmuir isotherm model, indicating multilayer adsorption, at all studied temperatures. The adsorption kinetic results showed that the pseudo-second-order model was more suitable to explain the adsorption of MB dye onto STOP. The adsorption mechanism results showed that the adsorption process was controlled by both the internal and external diffusion of MB dye molecules. The values of free energy change (ΔG ^o) and enthalpy change (ΔH ^o) indicated the spontaneous, feasible, and exothermic nature of the adsorption process. The maximum monolayer adsorption capacity of STOP was also compared with other low-cost adsorbents, and it was found that STOP was a better adsorbent for MB dye removal.     

Removal of methylene blue from aqueous solution by adsorption onto zeolite synthesized from coal fly ash and its thermal regeneration

BACKGROUND: The removal of cationic dyes from wastewater is of great importance. Three zeolites synthesized from coal fly ashes (ZFAs) were investigated as adsorbents to remove methylene blue (MB), a cationic dye, from aqueous solutions. Experiments were conducted using the batch adsorption technique under different conditions of initial dye concentration, adsorbent dose, solution pH, and salt concentration. RESULTS: The adsorption isotherm data of MB on ZFAs were fitted well to the Langmuir model. The maximum adsorption capacities of MB by the three ZFAs, calculated using the Langmuir equation, ranged from 23.70 to 50.51 mg g^?1. The adsorption of MB by ZFA was essentially due to electrostatic forces. The measurement of zeta potential indicated that ZFA had a lower surface charge at alkaline pH, resulting in enhanced removal of MB with increasing pH. MB was highly competitive compared with Na⁺, leading to only a < 6% reduction in adsorption in the presence of NaCl up to 1.0 mol L^?1. Regeneration of used ZFA was achieved by thermal treatment. In this study, 90–105% adsorption capacity of fresh ZFA was recovered by heating at 450 °C for 2 h. CONCLUSION: The experimental results suggest that ZFA could be employed as an adsorbent in the removal of cationic dyes from wastewater, and the adsorptive ability of used ZFA can be recovered by thermal treatment. Copyright © 2010 Society of Chemical Industry     

Graphene oxide impregnated with iron oxide nanoparticles for the removal of atrazine from the aqueous medium

ABSTRACT

The present study proposes development of an adsorbent based on combination of graphene oxide (GO) and iron oxide (α-γ-Fe₂O₃) nanoparticles for atrazine removal from water. The synthesized adsorbent (GO@ α-γ-Fe₂O₃) was characterized using different techniques. Magnetic measurements proved that the adsorbent has superparamagnetic characteristics, thus facilitating its magnetic separation from the working suspensions. The maximum adsorption capacity was 42.5 mg g^?1. The Langmuir isotherm and the pseudo-second order kinetic models correlated adequately with the experimental data. The thermodynamic data showed that atrazine adsorption was spontaneous, endothermic and thermodynamically favorable.     

磁性三乙烯四胺氧化石墨烯对Cu2+的吸附行为

为了提高氧化石墨烯(GO)的吸附能力和分离效果,采用恒温搅拌法和水热法制备磁性三乙烯四胺氧化石墨烯(M-T-GO)复合吸附剂。通过X射线衍射(XRD)、傅里叶红外光谱(FT-IR)和透射电镜(TEM)测试方法对其进行表征,并对M-T-GO对Cu²⁺的pH、吸附动力学、吸附等温线和吸附热力学进行研究。结果表明,M-T-GO对Cu²⁺的吸附符合二级反应动力学和Langmuir吸附等温式描述,吸附反应为自发吸热过程,饱和吸附量为245.09 mg·g^-1,同时具有快速分离和易再生的优点。采用X射线光电子能谱(XPS)推测M-T-GO对Cu²⁺的吸附机理,结果表明M-T-GO主要通过螯合作用和静电引力对Cu²⁺进行吸附。     

Radiation synthesis of graphene oxide/composite hydrogels and their ability for potential dye adsorption from wastewater

A high yield of graphene oxide (GO) was chemically synthesized from graphite powder utilizing adjusted Hummer's method. The contents of acidic functional groups in GO were determined using potentiometric titration. Composite hydrogels dependent on graphene oxide/poly(2-acrylamido-2-methylpropanesulfonic acid)/polyvinyl alcohol (GO/PAMPS/PVA) were synthesized utilizing a ⁶⁰Co gamma irradiation source at different doses. The synthesized graphene oxide and composite hydrogels were portrayed via X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared analysis. The morphology of composite hydrogels was characterized by scanning electron microscope. The gel % and swelling % for the prepared hydrogel demonstrated that the swelling % of hydrogel increased with raising AMPS content. Whereas the increment of GO and increasing the irradiation dose lead to a reduction in the swelling %. The influences of pH, GO percentage, initial dye concentration, the adsorbent dosage, contact time, and temperature on the adsorption of basic blue 3 dye were evaluated and the adsorption capacity was 194.6 mg/g at optimum conditions; pH = 6, GO/PAMPS/PVA composite hydrogels with 5 wt% of GO, initial dye concentration = 200 mg/L, adsorbent dose = 0.1 g, solution volume = 50 mL after 360 min at room temperature (25°C). The adsorption of dye onto the GO/PAMPS/PVA composite hydrogels follows Pseudo-second-order adsorption kinetics, fits the Freundlich adsorption isotherm model.     

Equilibrium and kinetics of adsorption of methylene blue on Ti‐modified volcanic ashes

Volcanic ashes (VAs) and Ti‐modified volcanic ashes (TVA) were investigated as inexpensive adsorbents to remove methylene blue (MB) from aqueous solutions. TVA displayed higher and faster MB adsorption than VA. Adsorption studies were carried out in a batch system at room temperature. In this work, several variables were studied: contact time, pH, initial MB concentration, and adsorbent dosage. The equilibrium data of MB adsorption were analyzed according to the Langmuir and Freundlich adsorption isotherm models. Optimum adsorption performance for TVAs particles, prepared using a hydrothermal method, was obtained at pH = 10 and 3 g/l adsorbent dose. MB adsorption isotherm data can be described satisfactorily by the Langmuir equation, whereas adsorption kinetic data fit a pseudo second‐order kinetics model. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

金刚烷胺/氧化石墨烯复合材料的制备及其吸附性能

以氧化石墨烯和金刚烷为原料，通过水相合成法制备了金刚烷胺功能化氧化石墨烯复合材料A/GO，以FT-IR、XRD和XPS对A/GO进行了结构表征，并考察了A/GO对有机染料的吸附性能。结果表明，与氧化石墨烯相比，A/GO对甲基蓝（AB93）表现出高效吸附性，其吸附动力学和吸附等温模型分别符合拟二级动力学和Langmuir模型，理论最大吸附容量（qm）为1250.0 mg/g。热力学分析表明，A/GO吸附AB93是自发的放热过程。A/GO吸附AB93对盐（NaCl和KCl）表现出良好的耐盐性，而CaCl2能有效地促进A/GO吸附AB93。对于刚果红和AB93等的混合染料体系，A/GO能选择性吸附AB93。     

Adsorption behavior of crystal violet from aqueous solutions with chitosan–graphite oxide modified polyurethane as an adsorbent

A series of chitosan (Ch)–graphite oxide (GO)‐modified polyurethane foam (PUF) materials as adsorbents were synthesized by a foaming technique. The adsorbent was characterized through IR spectroscopy, scanning electron microscopy, and thermogravimetric analysis (TGA). Batch adsorption experiments of the cationic dye crystal violet (CV) were carried out as a function of the Ch–GO content (1.0–8.0 wt %), solution pH (2–10), dye concentration (100–300 mg/L), adsorbent dosage (10–60 mg/mL), and temperature (20–45°C). At a lower pH value, the surface of Ch–GO/PUF acquired positive charge by absorbing H⁺ ions; this resulted in a decreasing adsorption of the cationic CV dye because of electrostatic repulsion. As the pH of the aqueous system increased, the numbers of negatively charged sites increased by absorbing OH⁻ ions, and a significantly high electrostatic attraction existed between the negatively charged surface of Ch–GO/PUF and the cationic dye (CV) molecules. This led to maximum dye adsorption. The kinetics, thermodynamics, and equilibrium of CV adsorption onto Ch–GO/PUF were investigated. The equilibrium data for CV adsorption fit the Langmuir equation, with a maximum adsorption capacity of 64.935 mg/g. The adsorption kinetics process followed the pseudo‐second‐order kinetics model. Thermodynamic parameters analysis revealed that the adsorption of CV from an aqueous solution by a Ch–GO modified PUF material was a spontaneous and endothermic process. We concluded that Ch–GO/PUF is a promising adsorbent for the removal of CV from aqueous solutions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41828.     

Adsorption characteristics of methylene blue on poplar leaf in batch mode: Equilibrium,kinetics and thermodynamics

Adsorption characteristics of methylene blue (MB) from aqueous solution on natural poplar leaf were investigated. Batch experiments were carried out to study the effects of initial pH, contact time, adsorbent dosage, and initial MB concentration, salt concentration (Ca²⁺ and Na⁺) as well as temperature on MB adsorption. The optimum condition for adsorption was found at pH 6–9 and adsorbent dosage of 2 g L⁻¹. The equilibration time was 240 min. The salt concentration had a negative effect on MB removal. The equilibrium data were analyzed with Langmuir, Freundlich and Koble-Corrigan isotherm models using nonlinear regression method. The adsorption process was more effectively described by Langmuir isotherm based on the values of the correlation coefficient R² and chi-square statistic x². The maximum monolayer adsorption capacity of poplar leaf from the Langmuir model was 135.35 mg g⁻¹ at 293 K. The pseudo second order equation provided a better fit to experimental data in the kinetic studies. Intraparticle diffusion was involved in adsorption process, but it was not the only rate-controlling step. Thermodynamic quantities such as ΔG, ΔH and ΔS were calculated, indicating that the adsorption process was spontaneous and endothermic. Dye-adsorbent interactions were examined by FTIR and SEM analysis. The FTIR results suggested that there were hydroxyl and carboxyl groups on the surface of poplar leaf, which would make MB adsorption possible. The SEM images showed effective adsorption of MB molecules on the adsorbent surface.     

Fast Removal of Sr(II) From Water by Graphene Oxide and Chitosan Modified Graphene Oxide

Graphene oxide is a unique material that can be used for adsorption of radioactive waste because it contains various function groups such as epoxide, carbonyl, carboxyl and hydroxyl in addition to its high specific surface area. The as-prepared GO and the modified one (GO-chitosan composite) have been prepared then characterized and used as adsorbent for radioactive metal ions [Strontium, Sr(II)]. The results showed that the prepared materials are efficient adsorbents for removal of Sr(II) from water. The effect of contact time, pH and temperature on adsorption have been studied. The results indicated that the maximum adsorption capacity was about 140 and 179.6 mg/g for GO and GO-chitosan composite respectively. It was found that pH?~?6 and temperature?~?40 °C are the best condition for removal of Sr(II) from water. Two isotherm models (Langmuir and Freundlich) and three kinetic models (Pseudo-first-order, pseudo-second-order, and intra-particle particle diffusion model) have been applied. Based on the calculated isotherm parameters (R²), it can be concluded that Langmuir model fits the adsorption equilibrium data better than Freundlich model, the results also indicated that the second order kinetic model is the best representative for adsorption of Sr(II) on GO, Chitosan and GO-Chitosan. Based on the regressions of intraparticle diffusion model, experimental data showed that the adsorption process involved intraparticle diffusion, which was not the only rate-controlling step.     

Synthesis and adsorption performance of fly ash/steel slag-based geopolymer for removal of Cu (II) and methylene blue

In order to realize the value-added resource utilization of solid waste, geopolymer particle adsorbents were prepared at low temperatures using silica-aluminum-rich fly ash and steel slag powders as raw materials. In order to investigate the mechanism of their adsorption of dyes and heavy metal ions from wastewater, the effects of steel slag/fly ash ratio, adsorbent dosage, initial concentration of methylene blue (MB) and Cu²⁺ solution, adsorption time and temperature on the adsorption performance of the fly ash/steel slag-based geopolymer adsorbents were investigated, systematically. Results presented that the adsorption capacities of MB and Cu²⁺ were 33.30 and 24.15 mg/g, and the removal efficiencies were 99.90% and 96.59% with the dosages of 3 and 4 g/L geopolymer adsorbents (steel slag/fly ash ratio of 20 wt.%), respectively. The adsorption processes of MB and Cu²⁺ on the adsorbents were in accordance with the proposed pseudo-second-order and Langmuir isotherm models, which mainly included physical and chemical adsorption mechanisms. The adsorption was a spontaneous endothermic process. The fly ash/steel slag-based geopolymer had good removal ability for dyes and heavy metal ions, and it could maintain good adsorption performance after three cycles of regeneration. It had potential application in wastewater treatment.     

Least square-support vector (LS-SVM) method for modeling of methylene blue dye adsorption using copper oxide loaded on activated carbon: Kinetic and isotherm study

A multiple linear regression (MLR) model and least square support vector regression (LS-SVM) model with principal component analysis (PCA) was used for preprocessing to predict the efficiency of methylene blue adsorption onto copper oxide nanoparticle loaded on activated carbon (CuO-NP-AC) based on experimental data set achieved in batch study. The PCA-LSSVM model indicated higher predictive capability than linear method with coefficient of determination (R²) of 0.97 and 0.92 for the training and testing data set, respectively. Firstly, the novel nanoparticles including copper oxide as low cost, non-toxic, safe and reusable adsorbent was synthesized in our laboratory with a simple and routine procedure. Subsequently, this new material properties such as surface functional group, homogeneity and pore size distribution was identified by FT-IR, SEM and BET analysis. The methylene blue (MB) removal and adsorption onto the CuO-NP-AC was investigated and the influence of variables such as initial pH and MB concentration, contact time, amount of adsorbent and pH, and temperature was investigated. The results of examination of the time on experimental adsorption data and fitting the data to conventional kinetic model show the suitability of pseudo-second order and intraparticle diffusion model. Evaluation of the experimental equilibrium data by Langmuir, Tempkin, Freundlich and Dubinin Radushkevich (D-R) isotherm explore that Langmuir is superior to other model for fitting the experimental data in term of higher correlation coefficient and lower error analysis.     

Arsenic adsorption using copper (II) oxide nanoparticles

Arsenic poisoning is a major problem in today's life. To reduce its concentration in drinking water, different metal based compounds were explored as arsenic adsorbents. In the present study, copper (II) oxide nanoparticles were prepared by thermal refluxing technique and used as an adsorbent for arsenic removal from water. Characterization of the adsorbent using TEM, BET, XRD and FTIR implied that the prepared adsorbent was in nano size and had excellent adsorption behavior with surface area of 52.11 m²/g. Systematic adsorption experiments were carried out with different process parameters such as contact time, adsorbent mass, pH, temperature and stirring speed and found that copper (II) oxide had very good efficiency towards arsenic adsorption. Thermodynamic parameters and adsorption kinetics were studied in detailed to know the nature and mechanism of adsorption. Results showed that the adsorption process followed pseudo second order kinetic and endothermic behavior. Adsorption equilibrium was studied with Langmuir and Freundlich isotherm models. The adsorption process followed Langmuir isotherm with an adsorption capacity of 1086.2 μg/g. A regeneration study was proposed in order to reuse the adsorbent for better economy of the process. Finally, a process design calculation is reported to know the amount of adsorbent required for efficient removal of arsenic from aqueous medium.     

Enhanced removal of naproxen from wastewater using silica magnetic nanoparticles decorated onto graphene oxide; parametric and equilibrium study

The present study describes the synthesis of silica and magnetic nanoparticle-decorated graphene oxide (GO-MNPs-SiO₂) and its application as an adsorbent for the removal of naproxen from wastewater. Nanocomposite was characterized utilizing FT-IR spectroscopy, FESEM microscopy, EDX and XPS spectroscopy. Under the optimum conditions, a high adsorption capacity (31 mg g^?1) was obtained toward naproxen at pH 5. The adsorption process was evaluated using isotherms; the Freundlich isotherm suggested a multilayer adsorption pattern for naproxen. Free energy confirmed a physisorption mechanism between naproxen and adsorbent. Lastly, the field application was performed in wastewater which obtained high removal efficiency percentages (83–94%).     

Sodic and Acidic Crystalline Lamellar Magadiite Adsorbents for the Removal of Methylene Blue from Aqueous Solutions: Kinetic and Equilibrium Studies

The present study reports the feasibility of two synthetic crystalline lamellar nano-silicates, sodic magadiite (Na-mag) and its converted acidic form (H-mag), as alternative adsorbents for the removal of the dye methylene blue (MB) from aqueous solutions. The ability of these adsorbents for removing the dye was explored through the batch adsorption procedure. Effects such as the pH and the adsorbent dosage on the adsorption capacities were explored. Four kinetic models were applied, the adsorption being best fitted to a fractionary-order kinetic model. The kinetic data were also adjusted to an intra-particle diffusion model to give two linear regions, indicating that the kinetics of adsorption follows multiple sorption rates. The equilibrium data were fitted to Langmuir, Freundlich, Sips, and Redlich-Peterson isotherm models. The maxima adsorption capacities for MB of Na-mag and H-mag were 331 and 173 mg g^?1, respectively.     

PDA/RGO复合材料对水中Fe（Ⅲ）的吸附行为

将多巴胺与氧化石墨烯纳米片层接枝复合制备了聚多巴胺/还原氧化石墨烯（PDA/RGO）复合材料,通过XRD、FTIR、FESEM和XPS等对该复合材料的结构和表面性质进行表征,并研究了其对水中Fe（Ⅲ）的吸附性能,考察了pH、吸附剂用量、吸附时间、Fe（Ⅲ）浓度和温度对其吸附性能的影响。结果表明：通过多巴胺与氧化石墨烯的仿生复合成功制备出具有优良吸附性能的PDA/RGO复合材料。pH为2,293 K时,该吸附材料对水中Fe（Ⅲ）的最大吸附量为59.1 mg·g^-1,其吸附等温线符合Freundlich方程,吸附动力学可用准二级动力学方程来描述。吸附热力学研究表明该复合材料对Fe（Ⅲ）的吸附过程为自发吸热过程,呈现非均质吸附特性。作为一种新型吸附材料,该复合材料在Fe（Ⅲ）等金属污染废水处理中将具有潜在的应用前景。     

Brij30/β-FeOOH/GO复合材料的可控构筑及其对盐酸四环素吸附性能

抗生素滥用已经成为全世界面临的公共卫生问题,去除环境中残留的抗生素刻不容缓。采用聚氧乙烯月桂醚(Brij30)对β-FeOOH进行表面改性,辅助水热法制备Brij30/β-FeOOH/GO复合材料。通过X-射线粉末衍射仪(XRD)、透射电子显微镜(TEM)、X-射线光电子能谱仪(XPS)、红外光谱仪(FT-IR)和Zeta电位对其组成及微观结构表征。考察了吸附剂投加量、溶液的pH值和共存离子对盐酸四环素(TCH)吸附性能的影响,研究了吸附机理。结果表明,在优化反应条件(Brij30/β-FeOOH/GO投加量0.01 g、溶液pH=5、吸附10 h、TCH初始浓度40 mg/L)下,吸附量达65.97 mg/g,吸附行为符合伪二级动力学方程和Freundlich吸附等温线模型,属于化学吸附并存的多分子层吸附。存在的吸附机理为π-π键堆积、氢键结合、螯合作用和电荷转移。     

Comparative study of methylene blue dye adsorption onto activated carbon,graphene oxide,and carbon nanotubes

Three different carbonaceous materials, activated carbon, graphene oxide, and multi-walled carbon nanotubes, were modified by nitric acid and used as adsorbents for the removal of methylene blue dye from aqueous solution. The adsorbents were characterized by N₂ adsorption/desorption isotherms, infrared spectroscopy, particle size, and zeta potential measurements. Batch adsorption experiments were carried out to study the effect of solution pH and contact time on dye adsorption properties. The kinetic studies showed that the adsorption data followed a pseudo second-order kinetic model. The isotherm analysis indicated that the adsorption data can be represented by Langmuir isotherm model. The remarkably strong adsorption capacity normalized by the BET surface area of graphene oxide and carbon nanotubes can be attributed to π–π electron donor acceptor interaction and electrostatic attraction.