Adsorption Kinetics of Methylene Blue from Aqueous Solutions onto Palygorskite

The adsorption kinetics of methylene blue from aqueous solutions on purified palygorskite was investigated. The kinetics data related to the adsorption of methylene blue from aqueous solutions are in good agreement with the pseudo-second order equation in ranges of initial concentration of 120-210 mg/L, oscillation speed of 100-200 r/min and temperature of 298-328K. The experimental results show that methylene blue is only adsorbed onto the external surface of purified palygorskite, and the apparent adsorption activation energy is 13.92 kJ/mol. The relatively low apparent adsorption activation energy suggests that the adsorption of methylene blue involves in not only a chemical, but also a physical adsorption process, and it is controlled by the combination of chemical adsorption and fiquid-film diffusion.

Kinetics and Thermodynamics of Adsorption Methylene Blue onto Tea Waste/CuFe₂O₄Composite

Tea waste/CuFe2O4 (TW/C) composite was prepared by co-precipitation method. The TW and TW/C samples are characterized by FTIR, XRD, SEM and N2 physical adsorption. The results showed that specific surface area of 350 and 570 m2·g?1 for TW and TW/C, respectively. The average pore size of TW/C is ca. 100 nm. Adsorption of methylen blue onto TW/C composite has been studied. Measurements are performed at various contact time, pH and adsorbent dosage. The adsorption kinetics of methylen blue (MB) could be described by the pseudo-second order kinetic model. The adsorption isotherms are described by means of Langmuir and Freundlich isotherms. It was found that the Freundlich model fit better than the Langmuir model. The thermodynamic constants of the adsorption were calculated to predict the nature of adsorption. The values of thermodynamic parameters indicate that a spontaneous and endothermic process was occurred.

Solution Blowing of Palygorskite-Based Nanofibers for Methylene Blue Adsorption

Palygorskite(PG)adsorbent with superior adsorption property and ion-exchange ability is highly desired in the field of dye removal.However,it generates high amounts of precipitation due to the granular form,resulting in secondary pollution after adsorption.Herein,the novel high porosity PG-based nanofibers that are easy for operating and retrieving have been fabricated using effective solution blowing and subsequent calcination.The obtained highly efficient adsorption nanofibers exhibit large specific surface area about 170.50 m^(2)/g with average diameter from 243 nm to 365 nm.Based on the abovementioned nanofibrous structure and negatively charged PG,the solution blowing of PG-based nanofibers(SBPNs)showed high adsorption capacity for methylene blue(MB)(112.36 mg/g).In addition,the adsorption of SBPNs is well described by the Langmuir isotherm model.This work provides new SBPNs forming process for the fields of dye removal,which may achieve the production of PG adsorbents at the industrial level.

Enhanced adsorption of Methylene Blue from aqueous solution by chitosan-g-poly(acrylic acid)/vermiculite hydrogel composites

A series of chitosan-g-poly （acrylic acid）/vermiculite hydrogel composites were synthesized and used as adsorbents for the investigation of the effect of process parameters such as vermiculite content, pH of dye solution, contact time, initial concentration of dye solution, temperature, ionic strength and concentration of surfactant sodium dodecyl sulfate on the removal of Methylene Blue （MB） from aqueous solution. The results showed that the adsorption capacity for dye increased with increasing pH, contact time and initial dye concentration, but decreased with increasing temperature, ionic strength and sodium dodecyl sulfate concentration in the present of the surfactant. The adsorption kinetics of MB onto the hydrogel composite followed pseudo second-order kinetics and the adsorption equilibrium data obeyed Langmuir isotherm. By introducing 10 wt.% vermiculite into chitosan-g-poly （acrylic acid） polymeric network, the obtaining hydrogel composite showed the highest adsorption capacity for MB, and then could be regarded as a potential adsorbent for cationic dye removal in a wastewater treatment process.

Equilibrium Isotherms and Kinetic Studies of Removal of Methylene Blue Dye by Adsorption onto Miswak Leaves as a Natural Adsorbent

In this research miswak leaves, agriculture wastes, available in large quantity in Saudi Arabia, was used as low-cost adsorbent for removing methylene blue (MB) dye. Equilibrium behavior of miswak leaves was investigated by performing batch adsorption experiments. The effects of [MB] 0, pH, contact time and adsorbent dose were evaluated. An alkaline pH (10.6) was favorable to the adsorption of MB dye. Adsorption isotherm models, Langmuir, Freundlich and Temkin were used to simulate the equilibrium data. Langmuir equation was found to have the highest value of R2 compared with other models. Furthermore, it was found that miswak leaves have a high adsorptive capacity towards MB dye (200 mg/g) and show favorable adsorption of MB dye with separation factor (RL < 1). In addition, pseudo-first- order, pseudo-second order and intra-particle diffusion were used to study the kinetics of MB adsorption onto miswak leaves. Adsorption process undergoes pseudo-second order kinetic as proved by the high value of R2 and the low value of sum of squared error (SSE percentage). Results indicated that intra-particle diffusion is not the limiting step, and the adsorption process is spontaneous as indicated by the negative value of the .

Removal of Methylene Blue, Rhodamine B and Ammonium Ion from Aqueous Solution by Adsorption onto Sintering Porous Materials Prepared from Coconut Husk Waste

The present work was done in order to develop and find out suitable conversion methods for coconut husk wastes into value-added products. It is well-known that coconuts husk waste is hydrophobic therefore ethanol with different doses was used as a surfactant to enhance the removal efficiency. Treated samples at different adsorbent amounts, sintering temperatures & sintering time, stirring time, pH, and solution temperatures for color removal of Methylene Blue (MB) & Rhodamine B (RhB) and ammonium concentration were evaluated by using UV-Visible Spectroscopy. At 300°C, results showed complete removal for MB and more than 75% for RhB, whereas removal of ammonium ion reached around 52% when sintering product from husk waste was used. Further investigation was carried out for ammonium ion to understand the desorption kinetic behaviors and isotherm models. Kinetics indicated that desorption of ammonium ion followed pseudo-first order equation. Adsorption thermodynamic parameters such as ΔG, ΔH, and ΔS followed Van’t Hoff plot for adsorption and found to be negative which indicated that the adsorption process for ammonium onto coconut husk was physical, spontaneous and exothermic.

Preparation of Kenaf Biochar and Its Adsorption Properties for Methylene Blue

The toxic dyestuff's from printing and dyeing wastewater have caused serious damages to the ecological environ-ment,thus exploring effective methods to remove them having become a key topic.Here,a series of biochar sam-ples were synthesized form kenaf to adsorb methylene blue(MB),which was acted as the dye representative for the test of adsorption capacity due to the presence of abundant double bond and aroma tic heterocyclic ring.By tuning the raw materials and pyrolysis temperature,a super adsorption capacity about 164.21 mg·g^(-1) was obtained over the biochar that pyrolyzed at 700℃ with the kenaf fiber as raw material Through the physical adsorption,elemental analysis,FTIR spectra and NH_(3)-TPD,it was found the high surface area and pore volume of biochar played a key role in the adsorption of MB,and the acidic sites would also assist the adsorption process.Besides,the adsorption kinetic model was ftted and calculated,implying the MB physically adsorbed on the bio-char rapidly and then occurred chemical adsorption on the acidic sites.In addition,through KBC700 recycling experiments,it was found that kenaf biochar had a good binding force to MB,which effectively avoided secondary pollution.This work provides important insights for the adsorption mechanism of MB by biochar,also offers some guidance for the further synthesis of biochar from various biomass.

Kinetic Modeling of Methylene Blue and Crystal Violet Dyes Adsorption on Alginate-Fixed Water Hyacinth in Single and Binary Systems

Removal of Methylene Blue (MB) and Crystal Violet (CV) dyes from monocomponent and binary aqueous solutions by water hyacinth-E. Crassipes roots fixed on alginate (a low-cost adsorbent) has been investigated. The extent of adsorption was evaluated as a function of solution pH, initial dye concentration, and bead biomass loading. Kinetic sorption data were analysed by widely used models: pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. The results showed that pseudo-second-order model better described the biosorption experimental data than the pseudo-first-order kinetic model for both dyes, whilst the Elovich model fitted the biosorption experimental data at lower dye concentrations. The intraparticle diffusion model indicated that sorption of CV and MB was characterized by rapid surface adsorption coupled with slow film diffusion process at higher initial dye concentration and at all initial bead biomass loading. The range of mean free energy values confirmed physical adsorption as the mechanism for dye removal from solution.

Valorization of Mango Peels as Low-Cost Biosorbent in Methylene Blue Adsorption:Kinetic and Equilibrium Study

Mango peels,which constitute a significant proportion of urban waste,have been modified with phosphoric acid for use as a biosorbent in the removal of methylene blue from wastewater.The characterization of the obtained biosorbent showed that cellulose is the primary constituent followed by lignin and hemicellulose.The high water content and the low value of ash content indicate that the studied biosorbent is a porous material containing a low proportion of inorganic,inert,amorphous and unusable part for biosorbent production.The zero charge point(pHpzc)assessment showed that the overall surface charge of the biosorbent is negative and therefore plays a key role in the adsorption process.The adsorption of methylene blue by mango peels biosorbent is a two-step process:a rapid first step in which over 90%methylene blue is removed in less than 10 min followed by a slowdown of the adsorption rate when approaching the adsorption equilibrium.Among pseudo-first,pseudo-second order and intraparticle diffusion kinetics models studies,pseudo-second order was the best applicable to describe methylene blue adsorption,suggesting a two-step mechanism:the transfer of methylene blue molecules from the solution to the mango peels biosorbent surface,followed by the interaction between adsorbates and surface.The equilibrium adsorption data were analyzed by Langmuir,Freundlich and Temkin isotherms models.Among them,Langmuir was the best model to describe adsorption,indicating the existence of homogeneous distribution of adsorption sites on mango peels biosorbent surface and a mono-layer adsorption of methylene blue molecules.The low value of Temkin’s constant B relative to the interaction energy between methylene blue molecules and the surface of the biosorbent shows that the adsorption involved is a physisorption process.

Mesoporous V-doped TiO_2 Nanoparticles as New Adsorbents for the Removal of Methylene Blue from Color Textile Wastewater

V-doped TiO2 nanoparticles（NPs） as dye adsorbents are synthesized by the co-precipitation method and characterized by X-ray powder diffraction, transmission electron microscope, N2 adsorption at 77 K, and X-ray photoelectron spectroscopy. The adsorption of methylene blue（MB） on the V-doped TiO2 NPs is studied in detail by varying the calcination temperature and V doping amount of the adsorbent, adsorbate concentration, adsorbent dosage, agitation rate, reaction temperature, and p H. The comparison of dye adsorption on V-doped TiO2 and parent TiO2 demonstrates that the adsorptive activity of TiO2 can be improved by V doping. The enhanced adsorptive performance can be attributed to the tremendous changes in texture, structure, and surface morphology of adsorbent. The adsorption kinetic analysis shows that the adsorption follows the pseudo-second order kinetics. The apparent activation energy for adsorption is calculated by Arrhenius formula to be 37.6 k J·mol-1, indicating that the adsorption is controlled by both of the diffusion and interfacial adsorption steps. The adsorption data are analyzed using Langmuir and Freundlich isotherms and the results indicate that the Langmuir model provides better correlation of the experimental data. The results conclusively show that the adsorption of MB is a spontaneous behavior and endothermic reaction with the ΔH value of 17.60 k J·mol-1.

Mechanism of Methylene Blue adsorption on hybrid laponite-multi-walled carbon nanotube particles

The kinetics of adsorption and parameters of equilibrium adsorption of Methylene Blue（MB）on hybrid laponite-multi-walled carbon nanotube（NT）particles in aqueous suspensions were determined.The laponite platelets were used in order to facilitate disaggregation of NTs in aqueous suspensions and enhance the adsorption capacity of hybrid particles for MB.Experiments were performed at room temperature（298 K）,and the laponite/NT ratio（Xl）was varied in the range of 0–0.5.For elucidation of the mechanism of MB adsorption on hybrid particles,the electrical conductivity of the system as well as the electrokinetic potential of laponite-NT hybrid particles were measured.Three different stages in the kinetics of adsorption of MB on the surface of NTs or hybrid laponite-NT particles were discovered to be a fast initial stage Ⅰ（adsorption time t=0–10 min）,a slower intermediate stage Ⅱ（up to t=120 min）and a long-lasting final stage Ⅲ（up to t=24 hr）.The presence of these stages was explained accounting for different types of interactions between MB and adsorbent particles,as well as for the changes in the structure of aggregates of NT particles and the long-range processes of restructuring of laponite platelets on the surface of NTs.The analysis of experimental data on specific surface area versus the value of Xl evidenced in favor of the model with linear contacts between rigid laponite platelets and NTs.It was also concluded that electrostatic interactions control the first stage of adsorption at low MB concentrations.

Methylene Blue Removal from Aqueous Solution by Adsorption on Archidendron jiringa Seed Shells

A study of batch and column adsorption using A. jiringa seed shell as a natural adsorbent to remove methylene blue from aqueous solution was carried out. This study aimed to determine the effectiveness of A. jiringa seed shell in removing methylene blue as well as to determine the isotherm and adsorption kinetics of methylene blue by A. jiringa seed shells. Parameters in the batch study showed optimum pH for adsorption was at pH 7 with the optimum contact time of 60 minutes whereas the adsorbent dose obtained was 12 g/l. The percentage removal of methylene blue increased with elevated temperature while the ionic strength reduced the adsorption capacity in the dye uptake. Langmuir isotherm was suitable for this study rather than Freundlich model due to the higher regression value: R2 = 0.9999. The most suitable kinetic model for this study was the pseudo second order, compared to pseudo first order, Elovich and intra particle with the value of regression: R2 = 0.9158. This column adsorption study used several different flow rates: 15 mL/min, 18 mL/min, 21 mL/min, 24 mL/min and 27 mL/min for 75 minutes long. The breakthrough time was lesser: 10 minutes in higher flow rates (24 mL/min and 27 mL/min), which indicated the shorter time for the adsorbent to be saturated. Thomas and Yoon & Nelson’s models were proven to be more suitable compared to Bohart-Adams model for the fixed bed adsorption study.

Adsorption of Methylene Blue by NaOH-modified Dead Leaves of Plane Trees

NaOH-modified dead leaves of plane trees were used as bioadsorbent to remove methylene blue (MB) from aqueous solution. Variable influencing factors, including contact time, temperature, initial MB concentration and pH were studied through single-factor experiments. The results showed that the initial concentration 100 mg/L, bioadsorbent of 2.5 g/L, pH of 7, room temperature were the best adsorption conditions. The NaOH-modified bioadsorbent had a high adsorption capacity for MB, and its saturated extent of adsorption was 203.28 mg/g, which was higher than the un-modified dead leaves (145.62 mg/g) and some other bioadsorbents. Finally, adsorption kinetics and isotherms were discussed, suggesting that the Langmuir isotherm model and Pseudo-second order kinetics were fitted well with the adsorption process.

Activated carbon coated palygorskite as adsorbent by activation and its adsorption for methylene blue

An activation process for developing the surface and porous structure of palygorskite/carbon（PG/C） nanocomposite using ZnC l2 as activating agent was investigated. The obtained activated PG/C was characterized by X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, field-emission scanning electron microscopy（SEM）, and Brunauer-Emmett-Teller analysis（BET） techniques. The effects of activation conditions were examined,including activation temperature and impregnation ratio. With increased temperature and impregnation ratio, the collapse of the palygorskite crystal structure was found to accelerate and the carbon coated on the surface underwent further carbonization. XRD and SEM data confirmed that the palygorskite structure was destroyed and the carbon structure was developed during activation. The presence of the characteristic absorption peaks of C_C and C-H vibrations in the FTIR spectra suggested the occurrence of aromatization. The BET surface area improved by more than 11-fold（1201 m2/g for activated PG/C vs. 106 m2/g for PG/C） after activation, and the material appeared to be mainly microporous. The maximum adsorption capacity of methylene blue onto the activated PG/C reached 351 mg/g. The activated PG/C demonstrated better compressive strength than activated carbon without palygorskite clay.

Removal of Methylene Blue from Water Using Hydroxyapatite Submitted to Microwave Irradiation

This study investigated the power of hydroxyapatite adsorbent prepared by a combined precipitation-microwave method, for removing a cationic dye methylene blue in aqueous media. The used adsorbent was characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR). The adsorption tests were conducted in batch mode. The effect of temperature, the pH of the solution and the mass of the adsorbent on the adsorption were determined. It is found that the adsorption was pH and temperature dependent. The kinetic study showed that the second-order model gives a better description of the kinetics of the adsorption reaction than the first-order model. Analysis of adsorption isotherms using different classical models showed that adsorption may be governed by the isotherms of Langmuir. The thermodynamic parameters were determined from the values of the maximum adsorption capacity and equilibrium constants.

Study on the chemisorption kinetics of Methylene Blue using SERS technique

SERS technique wae used to study the chemiesorption kinetics of Methylene Blue (MB) on the HNO3-etched silver surface. The adsorption kinetic parameters were deduced from different vibrational modes at a low concentration of 3.5 × 10?6 mol/L, and it showed that MB adsorbed uniformly (monolayerly) on silver surface. However, the adsorptive behavior turned anomalous at relatively higher concentrations and a possible explanation was suggested. In addition, the influence of Cl? ions on the adsorption states of MB was investigated, and it was shown that MB molecules, adsorbed on the silver surface, tended to transform the “lying-down” state to the “end - on” 4 state after CI? ions were added.

Effect of Co(Ⅱ) dopant on the removal of Methylene Blue by a dense copper terephthalate

In this research, for the first time, a series of Co(Ⅱ) doped copper terephthalate(Co X-Cu BDC,where X is doping percentage) were successfully synthesized via solvothermal method and were tested for dye removal application. The physical properties of Co X-CuBDC were studied by several techniques including X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), energy-dispersive spectroscopy(EDS), thermogravimetric analysis(TGA)and Brunauer–Emmett–Teller(BET) surface area analysis. The incorporation of Co(Ⅱ) dopant leads to isomorphic substitution of Cu(II) in the CuBDC framework with the maximum doping percentage of 22. Doping and parent MOFs which are non-porous were used for removal of Methylene Blue(MB) from aqueous solution. Adsorption capacity of Co22-CuBDC and CuBDC are 52 and 58 mg/g, respectively, both of which are higher than the adsorption capacity recorded from several high porosity MOFs. Adsorption kinetic studies indicate that adsorption process follows pseudo-second order model while the adsorption mechanism is dominated by electrostatic attraction. Overall, even though these materials show non-porous characteristic,it can be used effectively in wastewater treatment application.

橄榄果渣活性炭对水中亚甲基蓝吸附性能的研究

以橄榄果渣(OP)为原料,KOH为活化剂,在550℃电阻炉中高温煅烧制备橄榄果渣活性炭(OP-AC),并探究其对水中亚甲基蓝(MB)的吸附性能。OP-AC制备优选参数为20%KOH和OP炭粉的比例(浸渍比)为2.5∶1(mL∶g),浸渍时间4 h,活化时间20 min。优化条件下制备的OPAC在投加量为0.6 g,溶液pH值为13,振荡时间为15 min,MB初始质量浓度为10 mg/L条件下,对MB的去除率可达99.3%。通过扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)仪和孔径分析仪对OP-AC进行表征,分析结果表明:样品表面存在多种含氧官能团,OP-AC的BET比表面积为278.8324 m^(2)/g,平均孔径为1.8891 nm,总孔容为0.1317 cm^(3)/g,微孔占比为79.42%。OP-AC对水中MB的吸附符合准二级动力学模型(R^(2)>0.99),以化学吸附为主;吸附等温线符合Langmuir模型(R^(2)>0.93),属于单分子层吸附。经过3次循环使用后,OP-AC对MB的去除率仍高达83.1%;6次循环使用后,去除率为68.6%。

活性炭基硅镁复合吸附材料制备及其表征

以粉状活性炭(PAC)为原料,富含硅镁的坡缕石(PGS)为黏结剂,通过挤压成型的方法制备活性炭基硅镁复合吸附材料(PAC/PGS),考察不同的PAC和PGS质量比(炭料比)、焙烧温度和焙烧时间对PAC/PGS性能的影响,确定最佳成型条件。当炭料比50∶50,焙烧温度300℃,焙烧时间60 min,PAC/PGS整体性能最好,耐磨强度可达90%以上。PAC/PGS的亚甲基蓝吸附值为221.2 mg/g、碘吸附值为718.1 mg/g、四氯化碳吸附率为72%、比表面积为927 m^(2)/g、总孔容为0.7657 cm^(3)/g、平均孔径为3.21 nm、得率为96.2%,具备较好吸附性能与孔隙结构。通过热重(TG)分析、X射线衍射(XRD)、比表面积分析等技术对复合吸附材料结构进行表征,分析结果表明:PGS在300℃温度下能够保证孔道结构的完整,提高PAC/PGS的结构性能;PAC与PGS的成型过程主要属于物理结合,PAC分布在PGS棒状晶体间形成更为丰富的不规则孔隙,PAC/PGS的孔隙主要分布0.6~0.9 nm、1.1~30 nm,中孔约占80%。

电絮凝/活性炭吸附法去除工业废水中亚甲基蓝的实验研究

亚甲基蓝的分子结构稳定,具有热稳定性和光稳定性等特点,采用简单的单一工艺净化亚甲基蓝废水一般效果不佳,通过电絮凝/活性炭吸附耦合工艺对亚甲基蓝模拟废水的处理效果进行了探讨,并对比了此耦合工艺与单一电絮凝工艺和活性炭吸附工艺在同一条件下去除亚甲基蓝的效果。结果表明:电絮凝/活性炭吸附耦合工艺在同一条件下去除亚甲基蓝的能力均强于单一电絮凝工艺和活性炭工艺,且当处理时间为160 min、椰壳活性炭投加量为10 g·L^(-1)、极板间距为1.5 cm、电流密度为6 mA·cm^(-2)、溶液初始质量浓度为50 mg·L^(-1)时,对模拟废水的处理效果最佳,亚甲基蓝的去除率可以达到84.84%。并且通过实验发现该复合体系的动力学特性符合一级动力学模型。