Lightweight geopolymer-expanded glass composites for removal of methylene blue from aqueous solutions

In this work, monolithic geopolymer-expanded glass composites were prepared for the purpose of methylene blue removal from wastewaters. Zeolite A was found to form during geopolymerization process, e.g. sodium hydroxide solution alkali-activation of metakaolin and metakaolin with expanded glass aggregates blends, and curing at 80 °C for 24 h. The effect of expanded glass content on density and compressive strength of the obtained samples was examined and showed the decrease from 1.1 g/cm³ and 20.4 MPa (sample without expanded glass) to 0.5 g/cm³ and 1.6 MPa (sample with a 50%-replacement of metakaolin with expanded glass). The addition of expanded glass positively affected sorption capacity and removal efficiency. The sample without expanded glass reached 3.4 mg/g and 70%, while sample with a 50%-replacement of metakaolin with expanded glass reached 4.9 mg/g and 99%, respectively. The influence of methylene blue initial concentration and sorption time on the dye uptake and removal efficiency was also analyzed.     

High surface area benzimidazole based porous covalent organic framework for removal of methylene blue from aqueous solutions

In this study, a highly thermally stable benzimidazole based covalent organic framework (bCOF) was synthesized by the reaction of perlin‐tetracarboxylic anhydride, 5‐aminoisophthalic acid and diaminobenzidine in polyphosphoric acid medium. The synthesized porous bCOF was identified by different techniques. From CO₂ adsorption, the micropore surface area of the bCOF was found to be 856 m² g^?1; this synthesized bCOF has a widespread netting construction, and it has various porosity. The TGA results displayed the high thermal strength of the synthesized bCOF. After characterization, the bCOF was used for the removal of methylene blue from aqueous solution, and the essential parameters such as pH of the solution, contact time and initial concentration were assessed. The maximum adsorption capacity of the bCOF for removal of methylene blue was 63.29 mg g^?1 after only 40 min contact time at a pH of 6. Two kinetics and adsorption models were used for interpretation, and the outcomes showed that the pseudo‐second‐order and Langmuir models respectively were better fitted to the results. According to the results, the novel bCOF can be applied to remove methylene blue from aqueous solution. © 2020 Society of Chemical Industry     

Kinetics of zirconium ions adsorption on activated charcoal from aqueous solutions

The batch kinetics of adsorption of the zirconium ions from aqueous solutions on activated charcoal has been investigated over a wide range of concentration of zirconium ions (1.0–5.0 g/l) and temperatures (10–50°C). The adsorption process of zirconium ions proceeds via two stages; the first stage is rather fast, followed by a much slower one. The Bangham equation was used to study the kinetics of the zirconium ions' adsorption on activated charcoal. It is observed that the diffusion of zirconium ions into the pores of the activated charcoal controls the kinetics of the adsorption process. Moreover, zirconium ion adsorption obeys the Freundlich and Langmuir isotherms in the concentration range studied. The adsorption equilibrium constant (k_c) values for zirconium ions adsorption on activated charcoal have also been calculated at different temperatures. Various thermodynamic quantities, ΔG, ΔH, and ΔS were computed from k_c values. The results showed that the adsorption of zirconium ions on activated charcoal is an endothermic process.     

Removal of methylene blue from aqueous solutions by adsorption onto chemically activated halloysite nanotubes

This study examines the adsorption behavior of methylene blue (MB) from aqueous solutions onto chemically activated halloysite nanotubes. Adsorption of MB depends greatly on the adsorbent dose, pH, initial concentration, temperature and contact time. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms and the Langmuir model agrees very well with experimental data. The maximum adsorption capacities for MB ranged from 91.32 to 103.63 mg·g⁻¹ between 298 and 318 K. A comparison of kinetic models applied to the adsorption data was evaluated for pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion equation. The results showed the adsorption process was well described by the pseudo-second-order and intra-particle diffusion mode. Thermodynamic parameters suggest that the adsorption is spontaneous and endothermic. The obtained results indicated that the product had the potential to be utilized as low-cost and effective alternative for dye removal in wastewater.     

An economically viable removal of methylene blue by adsorption on activated carbon prepared from rice husk

Application of an agricultural waste material, rice husk, has been investigated for preparation of activated carbon. The rice husk‐activated carbon (RHAC) was successfully utilised for the removal of a cationic dye, methylene blue (MB) from aqueous solutions. The activated carbon was prepared in presence of ZnCl₂ as an activating agent under inert nitrogen atmosphere. RHAC was characterised for surface area, pore structural parameters, and point zero charge (pH_ZPC). The activated carbon was further characterised by Fourier transformation infrared (FT‐IR) spectrometer, X‐ray diffractometer (XRD), and scanning electron microscope (SEM). The effect of different parameters such as contact time and initial concentration, adsorbent dose, and temperature on removal of the dye from aqueous solutions was investigated. The experimental data fitted well in both the Freundlich and Langmuir isotherm models. The maximum adsorption capacity for MB was found to be 9.73 mg g⁻¹ at 303 K. During the study of effect of adsorbent dose, almost a 100% removal was achieved at a higher dose of RHAC. Most of the experiments were carried out at an initial concentration of MB of 60 mg/L and at 303 K. Different thermodynamic parameters, viz., changes in free energy (G°), enthalpy (H°), and entropy (S°) have also been determined to explain feasibility of the process of removal. The sorption of MB on RHAC was found to be feasible, spontaneous, and endothermic in nature.     

Silkworms’ feces-based activated carbons as cheap adsorbents for removal of cadmium and methylene blue from aqueous solutions

Activated carbon samples, ACs, were obtained from silkworms’ feces via chemical activation method. Many activating agents including the new ones KCl, CrCl₃ and TiCl₄ were compared. Acidic and basic oxidic groups in addition to aromatic tertiary and secondary amines have been detected on the surface of produced ACs. Furthermore, microporous solids furnishing high internal specific surface area, ranging between 1000 and 2000 m²/g, and total pore volume up to 0.85 cm³/g were obtained. TiCl₄ resulted in the solid possessing the highest area and pore volume. The obtained solids showed high efficiency in removing methylene blue and cadmium from their aqueous solutions. Adsorption capacity of sample AC/TiCl₄ is 461 mg/g of MB at pH = 10, and 62.6 mg/g of Cd²⁺ at pH = 8. The nature of the formed microporous texture and the prevailing surface oxidic groups are the main controlling parameters for the observed high efficiency toward both adsorbates.     

超声波辅助粉煤灰去除水中亚甲基蓝染料的动力学分析

为了开发更多的粉煤灰用途,采用粉煤灰去除水中的染料污染物,达到以废治废的目的。采用超声波辅助粉煤灰的方法,以亚甲基蓝染料作为模拟污染物,考察此工艺的可行性,讨论亚甲基蓝的去除效果,分析其动力学。研究结果证明,超声波-粉煤灰联合体系（US-FA体系）具有良好的去除染料污染物的能力,超声波的引入能提高粉煤灰对染料污染物的去除率,协同效应非常明显,粉煤灰投加量0.3、0.5、1.0和2.0 g的情况下,协同因子分别达到1.05、1.32、1.55和2.27。在本实验体系内,经过恒温控制后,超声波的热效应可以忽略,主要通过粉煤灰吸附和羟基自由基降解两大主要途径去除污染物,超声波对去除性能的促进作用主要体现在以下几个方面：一是超声波空化作用产生羟基自由基,超声波和粉煤灰表面相互作用产生更多的羟基自由基;二是超声波能促进粉煤灰表面产生更多的活性位,促进了吸附过程的化学反应步骤,由于粉煤灰对亚甲基蓝的吸附过程以化学反应为控制步骤,所以超声波能大为促进粉煤灰的吸附性能;三是超声波的引入加剧了固液混合,促进污染物向固相表面移动,促进更多的污染物进入到吸附剂颗粒内部,改善了传质。     

Citric acid modified waste cigarette filters for adsorptive removal of methylene blue dye from aqueous solution

Waste cigarette filters (CFs) were recycled and modified with a nontoxic and low-cost citric acid (CA). The modified CFs were employed in the adsorptive removal of methylene blue (MB) dye from aqueous medium. The influence of pH, contact time, initial dye concentration, and adsorbent dose on adsorption of MB dye was evaluated. The adsorption studies were conducted by employing linear and nonlinear Langmuir and Freundlich isotherm models. The adsorption capacity of CF obtained through linear and nonlinear Langmuir model were 88.02 and 94 mg g⁻¹, which improved up to 163.93 and 168.81 mg g⁻¹, respectively, after the introduction of functional groups in CF-CA. The adsorption kinetics data were well fitted by pseudo-second order kinetics with coefficient of regression (R²) closed to unity. The removal efficiency of CF-CA was 97% at equilibrium time of 4 h. Desorption studies indicated that CF-CA could be regenerated by using HCl (0.1 M) and desorption efficiency was up to 82% upon second cycle of reusability experiment. This study proposed a green and economical use of recycled CFs in dyes wastewater treatment, simultaneously reducing the negative environmental impact due to their improper disposal.     

Equilibrium modeling for the adsorption of methylene blue from aqueous solutions on activated clay minerals

This work reports the application of an activated clay mineral as adsorbent for the removal of a basic dye, methylene blue (MB), from aqueous solutions. The thermal treatment at 300 °C for 2 h and the acid activation with nitric acid of 0.5 mol/dm³ under reflux conditions improve the adsorption capacity of the raw clay mineral. A maximum of 500 mg/g of MB at equilibrium is achieved. Equilibrium data are mathematically modelled using the Freundlich, Langmuir and Toth isotherm adsorption models.     

软锰矿-含油污泥基活性炭对亚甲基蓝的吸附特性

以含油污泥为原料,添加适量软锰矿制备活性炭,用于吸附水中的亚甲基蓝并探究其吸附性能与吸附机制。采用SEM、BET、XPS、FTIR表征活性炭的微观形貌和物相结构,利用二维红外相关光谱探究活性炭与亚甲基蓝的吸附点位及吸附机制。结果表明,活性炭是比表面积达464.409m²/g的介孔材料,且表面含有大量的含氧官能团,活性炭吸附亚甲基蓝的过程符合准二级动力学方程和Langmuir模型,主要受化学吸附控制的单分子层吸附。结合移动窗口二维红外相关光谱分析发现,在活性炭吸附亚甲基蓝的过程中吸附较低浓度的亚甲基蓝参与的官能团较多,以各种含氧官能团为主,当亚甲基蓝浓度升高,以π-π相互作用为主;吸附机制包括氢键作用、含氧官能团参与和π-π相互作用等。     

Adsorption of methylene blue from aqueous solutions by modified expanded graphite powder

The modified expanded graphite (MEG) powder was used as a porous adsorbent for the removal of the cationic dye, methylene blue (MB), from aqueous solutions. The dye adsorption experiments were carried out with the bath procedure. Experimental results showed that the basic pH, increasing initial dye concentration and high temperature favored the adsorption. The dye adsorption equilibrium was attained rapidly after 5 min of contact time. Experimental data related to the adsorption of MB on the MEG under different conditions were applied to the pseudo-first-order equation, the pseudo-second-order equation and the intraparticle diffusion equation, and the rate constants of first-order adsorption (k₁), the rate constants of second-order adsorption (k₂) and intraparticle diffusion rate constants (k_int) were calculated, respectively. The experimental data fitted very well in the pseudo-second-order kinetic model. The thermodynamic parameters of activation such as Gibbs free energy, enthalpy, and entropy were also evaluated. The results indicated that the MEG powder could be employed as an efficient adsorbent for the removal of textile dyes from effluents.     

Study on the efficiency of ethylene vinyl acetate–fly ash composites for the uptake of phenols from synthetic waste water

In this study, ethylene vinyl acetate–fly ash (EVA‐FA) composites were prepared by the melt mixing technique using a rheomixer for the purpose of removing 2,4,6‐trichlorophenol (TCP) and p‐nitrophenol (PNP) from water. The fly ash was characterized by X‐ray fluorescence spectroscopy, scanning electron microscopy (SEM) and X‐ray diffraction (XRD); the composites were characterized using SEM and XRD. Brunauer, Emmett, and Teller (BET) measurements revealed a surface area (S_BET) of 0.07110 m²/g for the fly ash. The adsorption of TCP and PNP were monitored by UV–Vis spectrophotometer. The maximum adsorption of PNP was obtained at pH 5 after a contact period of 12 h, whereas that of the TCP was obtained at pH 4 after a period of 10 h has elapsed. The equilibrium adsorption data were evaluated using Langmuir and Freundlich adsorption isotherm models. The Langmuir adsorption model gave the better correlation coefficients for the equilibrium adsorption data. The kinetics data followed the pseudo‐second‐order model for both TCP and PNP. The theoretical maximum adsorption capacity (q_max) of the adsorbent used in the study was found to be 3.424 mg/g and 2.544 mg/g for TCP and PNP, respectively. The desorption of the phenols from the composites was performed using 0.2M NaOH. About 82.6% and 76.3% of TCP and PNP were recovered, respectively. The study showed that the pH of the solution and contact time play a significant role in the adsorption process. Furthermore, we have demonstrated that EVA‐FA composites have the potential to adsorb phenols from acidic water solutions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Simultaneous adsorptive removal of methylene blue and copper ions from aqueous solution by ferrocene‐modified cation exchange resin

Resin was modified with ferrocene (Fc) to enhance removal of Methylene Blue (MB) and Cu²⁺ from simulated wastewater. The FTIR, N₂‐BET, and X‐ray fluorescence analysis confirmed that Fc was successfully grafted onto the surface of resin. The adsorption capacity of Fc modified cation exchange resin (FMCER) was calculated to be 392.16 mg/g Cu²⁺ and 10.01 mg/g MB. Both processes were spontaneous and exothermic, best described by Langmuir equation. Pseudo‐first‐order kinetic model satisfied the adsorption of MB, while the intraparticle‐diffusion model fitted the kinetics of Cu²⁺ adsorption best. The result revealed a multilayer adsorption of Cu²⁺ on FMCER, and the kinetics maybe controlled by intraparticle diffusion, film diffusion, and competition force. The adsorption of MB and Cu²⁺ on FMCER were physicosorptive, with activation energies of 2.09 and 1.27 kJ/mol. pH 2–7 and 4–5 are optimum for the removal of MB and Cu²⁺, and pH 4 is optimal for the simultaneous removal of MB and Cu²⁺. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41029.     

NaOH改性花生壳对亚甲基蓝染料吸附性能的研究

花生壳用5%的NaOH溶液改性作吸附剂处理亚甲基蓝染料废水,考察pH值、吸附剂投加量、染料浓度和温度及吸附时间对染料吸附性能的影响。结果表明,吸附最佳的工艺条件为:温度25℃,吸附剂投加量0.3 g,亚甲基蓝的初始浓度3.5 g/mL,反应时间135 min,pH值7。此时改性花生壳对亚甲基蓝的吸附率达99.57%。     

Adsorption of methylene blue from aqueous solutions by synthetic montmorillonites of different compositions

The sorption capacity of synthetic montmorillonites of the composition Na_2x (Al_2(1–x),Mg_2x )Si₄O₁₀(OH)₂ · nH₂O (where 0 < x < 1) in relation to the methylene blue dye has been investigated. The obtained results from the data for natural samples of montmorillonite (K10) and activated carbon have been compared. The effect of the montmorillonite composition and the medium acidity on the degree of dye adsorption has been studied. The chemical composition of montmorillonite, which is optimal for solving tasks in the field of ecology and medicine, has been determined. The character of the interaction of montmorillonites with the adsorbed substance from the point of view of the physical-chemical sorption models has also been studied.     

Preparation of polyaniline montmorillonite clay composites for the removal of diethyl hexyl phthalate from aqueous solutions

The work presents the synthesis of polyaniline functionalized montmorillonite (PANI/MMT) clay composites and evaluation of their performance as an adsorbent for the mitigation of toxic diethyl hexyl phthalate (DEHP) from water. The formation of composite was confirmed by different analytical techniques such as FTIR, zeta potential analysis, XRD, SEM, and AFM. The adsorption capacity of PANI/MMT was superior to MMT. DEHP followed partition mechanism on PANI/MMT whereas MMT favored surface adsorption mechanism. The performance of PANI/MMT for DEHP removal was unaffected by the change in pH of solution, change in salinity, and hardness contents in aqueous system and consecutive adsorption desorption cycles compared to MMT. Furthermore, both PANI/MMT and MMT exhibited greater adsorption capacities as compared to the previously published work and showed satisfactory performance in real water samples.     

Removal of arsenic from aqueous solutions by an adsorption process with titania–silica binary oxide nanoparticle loaded polyacrylonitrile polymer

A new and simple method was developed to produce gelatin nanoparticles of ～ 30–40 nm for use as carriers for drug release applications. The nanoparticles were uniform in size and well dispersed. An anticancer drug, 5‐fluorouracil, was encapsulated with an efficiency as high as 85%. The nanoparticles showed sustained release of 5‐fluorouracil, and release rates varied with amount of crosslinking in the nanoparticles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Postconsumer high‐density polyethylene/agave fiber foamed composites coated with chitosan for the removal of heavy metals

Composites of postconsumer high‐density polyethylene with agave fiber were prepared by single‐screw extrusion with azodicarbonamide as a foaming agent to increase the surface area; the composite pellets were coated with chitosan afterward. A chemical pretreatment was applied to the pellets to enhance the chitosan gel compatibility. The adsorption capacities of the composites coated with chitosan were evaluated for Cd(II) and Cu(II) removal from aqueous solutions. The coated composites were characterized by scanning electron microscopy, attenuated total reflectance infrared spectroscopy, and X‐ray photoelectron spectroscopy. Atomic absorption spectroscopy was used to measure metal uptake in batch adsorption studies. The results of this study demonstrated the composites' ability to immobilize chitosan on their surfaces and their capacity to adsorb metal ions. The equilibrium isotherms for Cd(II) and Cu(II) adsorption on the chitosan‐coated composites were described by the Langmuir model. This material represents an attractive low‐cost recycled material for adsorbing metal ions from polluted waters. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

分子印迹聚合物微球对亚甲基蓝的去除特性研究

以亚甲基蓝为模板分子,丙烯酰胺为功能单体,乙二醇二甲基丙烯酸酯（EGDMA）为交联剂,偶氮二异丁腈（AIBN）为引发剂．采用沉淀聚合法制备了亚甲基蓝分子印迹聚合物微球（MIP）。用扫描电镜表征了MIP的形貌,结果显示制备的MIP的粒径为1～3μm,粒径较为均匀。考察了MIP对亚甲基蓝的吸附性能,结果表明其吸附动力学过程可以用假二级吸附速率方程来描述,MIP对亚甲基蓝的最大吸附量为27．1mg／g,吸附效果较好,可以用于染料废水中亚甲基蓝的分离富集。     

ANN modeling in Pb(II) removal from water by clay‐polymer composites fabricated via the melt‐blending

This work presents two new related aspects in heavy‐metal adsorption. The first aspect is the use of Cloisite^® C20A‐polycaprolactone (C20A‐PCL) composite with the aid of dry Na2SO4 in Pb(II) extraction from water. The composite was fabricated by means of the melt‐blending method at a filler loading rate of 3% (w/w). This material was able to remove 87% of Pb(II) from water despite the fact that the polymer is a thermoplastic and the C20A is hydrophobic. The second aspect is the modeling of the adsorption data obtained using polymer‐clay composites synthesized via the melt‐blending method by artificial neural networks. A network with 10 neurons and using TRAINLM, and employing tansig function in the input layer and purelin in the output layer was found to be optimal. The network was used to predict the adsorption efficiency of Pb(II) by several clay‐polymer composites and the correlation was satisfactory. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3894–3901, 2013