Simulation of methylene blue adsorption by salts-treated beech sawdust in batch and fixed-bed systems

Batch and column kinetics of methylene blue adsorption on calcium chloride, zinc chloride, magnesium chloride and sodium chloride treated beech sawdust were simulated, using untreated beech sawdust as control, in order to explore its potential use as a low-cost adsorbent for wastewater dye removal. The adsorption capacity, estimated according to Freundlich's model, the Langmuir constant K(L) and the adsorption capacity coefficient values, determined using the Bohart and Adams' bed depth service model indicate that salts treatment enhanced the adsorption properties of the original material. Since sawdust is an industrial waste/byproduct and the salts used can be recovered as spent liquids from various chemical operations, this process of adsorbent upgrading/modification might be considered to take place within an 'Industrial Ecology' framework.     

Biosorption of methylene blue from aqueous solution by rice husk in a fixed-bed column

In this study, the ability of rice husk to adsorb methylene blue (MB) from aqueous solution was investigated in a fixed-bed column. The effects of important parameters, such as the value of initial pH, existed salt, the flow rate, the influent concentration of MB and bed depth, were studied. The Thomas model was applied to adsorption of MB at different flow rate, influent concentration and bed depth to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design using non-linear regression. The bed-depth/service time analysis (BDST) model was also applied at different bed depth to predict the breakthrough curves. The two models were found suitable for describing the biosorption process of the dynamic behavior of the rice husk column. All the results suggested that rice husk as adsorbent to removal MB from solution be efficient, and the rate of biosorption process be rapid. When the flow rate was 8.2ml min(-1) and the influent concentration of MB was 50mgl(-1), the equilibrium adsorption biomass reached 4.41mgg(-1) according to Thomas model.     

Comparison of linear and non-linear method in estimating the sorption isotherm parameters for safranin onto activated carbon

Comparison analysis of linear least square method and non-linear method for estimating the isotherm parameters was made using the experimental equilibrium data of safranin onto activated carbon at two different solution temperatures 305 and 313 K. Equilibrium data were fitted to Freundlich, Langmuir and Redlich-Peterson isotherm equations. All the three isotherm equations showed a better fit to the experimental equilibrium data. The results showed that non-linear method could be a better way to obtain the isotherm parameters. Redlich-Peterson isotherm is a special case of Langmuir isotherm when the Redlich-Peterson isotherm constant g was unity.     

Kinetics and mechanism of removal of methylene blue by adsorption onto perlite

The kinetics and mechanism of methylene blue adsorption on perlite have been studied. The effects of various experimental parameters, such as initial dye concentration, temperature and pH on the adsorption rate were investigated. Adsorption measurements show that the process is very fast and physical in nature. The extent of the dye removal increased with increase in the initial concentration of the dye and the initial pH and temperature of solution. Adsorption data were modelled using the first and second-order kinetic equations, mass transfer and intra-particle diffusion models. It was shown that the second-order kinetic equation could best describe the sorption kinetics. The diffusion coefficient, D, was found to increase when the initial dye concentration, pH and temperature were raised. Thermodynamic activation parameters, such as DeltaG*, DeltaS* and DeltaH*, were calculated.     

The adsorption kinetics of the cationic dye, methylene blue, onto clay

In this study, adsorption kinetics of a cationic dye, methylene blue, onto clay from aqueous solution with respect to the initial dye concentration, temperature, pH, mixing rate and sorbent dosage were investigated. In order to understand the adsorption mechanism in detail, zeta potentials and the conductivities of clay suspensions at various pH (1-11) and cation exchange capacity (CEC) were measured. Porosity and BET surface area of clay studied were determined. The results showed that the adsorption has been reached to equilibrium in 1 h. It was found that the amount adsorbed of methylene blue increases with decreasing temperature and also with increasing both sorbent dosage and increasing initial dye concentration. Adsorption capacity decreases with increasing pH, except for the natural pH (5.6) of clay suspensions. The adsorption kinetics of methylene blue has been studied in terms of pseudo-first-order, pseudo-second-order sorption and intraparticle diffusion processes thus comparing chemical sorption and diffusion sorption processes. It was found that the pseudo-second-order mechanism is predominant and the overall rate of the dye adsorption process appears to be controlled by the more than one-step.     

Comparative analysis of linear and non-linear method of estimating the sorption isotherm parameters for malachite green onto activated carbon

The experimental equilibrium data of malachite green onto activated carbon were fitted to the Freundlich, Langmuir and Redlich-Peterson isotherms by linear and non-linear method. A comparison between linear and non-linear of estimating the isotherm parameters was discussed. The four different linearized form of Langmuir isotherm were also discussed. The results confirmed that the non-linear method as a better way to obtain isotherm parameters. The best fitting isotherm was Langmuir and Redlich-Peterson isotherm. Redlich-Peterson is a special case of Langmuir when the Redlich-Peterson isotherm constant g was unity.     

Linear and non-linear regression analysis for the sorption kinetics of methylene blue onto activated carbon

Batch kinetic experiments were carried out for the sorption of methylene blue onto activated carbon. The experimental kinetics were fitted to the pseudo first-order and pseudo second-order kinetics by linear and a non-linear method. The five different types of Ho pseudo second-order expression have been discussed. A comparison of linear least-squares method and a trial and error non-linear method of estimating the pseudo second-order rate kinetic parameters were examined. The sorption process was found to follow a both pseudo first-order kinetic and pseudo second-order kinetic model. Present investigation showed that it is inappropriate to use a type 1 and type pseudo second-order expressions as proposed by Ho and Blanachard et al. respectively for predicting the kinetic rate constants and the initial sorption rate for the studied system. Three correct possible alternate linear expressions (type 2 to type 4) to better predict the initial sorption rate and kinetic rate constants for the studied system (methylene blue/activated carbon) was proposed. Linear method was found to check only the hypothesis instead of verifying the kinetic model. Non-linear regression method was found to be the more appropriate method to determine the rate kinetic parameters.     

Adsorption of methylene blue onto hazelnut shell: Kinetics, mechanism and activation parameters

The adsorption kinetics of methylene blue (MB) on the hazelnut shell with respect to the initial dye concentration, pH, ionic strength, particle size and temperature were investigated. The rate and the transport/kinetic processes of MB adsorption were described by applying the first-order Lagergren, the pseudo-second-order, mass transfer coefficient and the intraparticle diffusion models. Kinetic studies showed that the kinetic data were well described by the pseudo-second-order kinetic model. Significant increases in initial adsorption rate were observed with the increase in temperature followed by pH and initial MB concentration. The intraparticle diffusion was found to be the rate-limiting step in the adsorption process. Adsorption activation energy was calculated to be 45.6kJmol(-1). The values of activation parameters such as free energy (DeltaG(*)), enthalpy (DeltaH(*)) and entropy (DeltaS(*)) were also determined as 83.4kJmol(-1), 42.9kJmol(-1) and -133.5Jmol(-1)K(-1), respectively.     

NaP1 zeolite synthesized via effective extraction of Si and Al from red mud for methylene blue adsorption

NaP1 zeolite, using red mud (RM) as raw material, was successfully prepared via alkali fusion and hydrothermal method. NaP1 zeolite, which was a mesoporous material, had specific surface area and pore diameter of 79.3 m²·g⁻¹ and 7.26 nm, respectively. NaP1 zeolite had excellent adsorption properties. Under the optimum adsorption conditions, methylene blue (MB) was adsorbed through NaP1 zeolite, the adsorption capacity was 48.7 mg·g⁻¹ and the removal efficiency was 97.1%. The adsorbent was regenerated with sodium chloride as eluent. The adsorption capacity of the adsorbent regenerated three times still was satisfactory 34.53 mg·g⁻¹, which showed the excellent stability performance from NaP1 zeolite. The adsorption conformed to the pseudo second order kinetic and Freundlich isotherm model. Moreover, MB molecules were adsorbed by diffusion on the outer surface, diffusion on the inner surface, and adsorption on the inner surface of NaP1 zeolite. And, during the external diffusion, electrostatic attraction and hydrogen bonding created. Al and Si were extracted from RM to prepare NaP1 zeolite with excellent adsorption properties. This result provides an important example for the development of the potential value of RM.     

涂铁多孔陶瓷吸附去除亚甲基蓝的热动力学

研究了涂铁多孔陶瓷(IOCPC)在20～40℃下对亚甲基蓝(MB)静态吸附的热动力学性质.用液相沉积、多次涂层法对赤泥质多孔陶瓷表面改性制备吸附剂,并通过小试摇床实验考察了IOCPC在不同条件下吸附MB的效果.结果表明:IOCPC的比表面积为4.987m2/g,比改性前增大3.28倍,平均孔径为11.36nm.IOCPC对MB的吸附等温线呈S型,Freundlich等温吸附方程和准二级动力学方程较好地描述了IOCPC对MB的吸附等温线及吸附动力学实验结果,相关系数分别＞0.89和0.97,平衡吸附容量随温度的升高而增加.由标准吉布斯自由能变(莫獹＜0 )、标准反应焓变(莫獺0＞0)和吸附活化能(Ea=16.145kJ/mol＞4.184kJ/mol)的值可判断,IOCPC对MB的吸附是自发的、吸热的化学吸附反应.     

Isotherms and thermodynamics by linear and non-linear regression analysis for the sorption of methylene blue onto activated carbon: comparison of various error functions

A comparison of linear and non-linear regression method in selecting the optimum isotherm was made to the experimental equilibrium data of methylene blue sorption by activated carbon. The r2 was used to select the best fit linear theoretical isotherm. In the case of non-linear regression method, six error functions, namely coefficient of determination (r2), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), average relative error (ARE), sum of the errors squared (ERRSQ) and sum of the absolute errors (EABS) were used to predict the parameters involved in the two and three parameter isotherms and also to predict the optimum isotherm. For two parameter isotherm, MPSD was found to be the best error function in minimizing the error distribution between the experimental equilibrium data and predicted isotherms. In the case of three parameter isotherm, r2 was found to be the best error function to minimize the error distribution structure between experimental equilibrium data and theoretical isotherms. The present study showed that the size of the error function alone is not a deciding factor to choose the optimum isotherm. In addition to the size of error function, the theory behind the predicted isotherm should be verified with the help of experimental data while selecting the optimum isotherm. A coefficient of non-determination, K2 was explained and was found to be very useful in identifying the best error function while selecting the optimum isotherm.     

Equilibrium data, isotherm parameters and process design for partial and complete isotherm of methylene blue onto activated carbon

Equilibrium data for the adsorption of methylene blue onto activated carbon was reported. The equilibrium data were splitted to different data sets to have an idea on the partial and complete isotherm. The equilibrium data were analyzed using Freundlich, Langmuir and Redlich-Peterson isotherm. The influence of partial isotherm and complete isotherm on the equilibrium parameters in isotherm expression were estimated. Equilibrium data covering the complete isotherm is the best way to obtain the parameters in isotherm expressions. Present investigation showed that for successful batch sorber design, equilibrium data with partial isotherm is not sufficient, instead equilibrium data that covers complete isotherm is required. Redlich-Peterson and Langmuir isotherm well represent the adsorption of methylene blue onto activated carbon. Redlich-Peterson isotherm is a special case of Langmuir when the constant 'g' equals unity.     

沙柳基磁性多孔炭的制备及其吸附亚甲基蓝性能研究

采用水热法原位改性沙柳生物炭制备磁性多孔炭复合材料,利用SEM、XRD、FT-IR、XPS和BET分别对多孔炭的形貌、结构表征,并研究磁性多孔炭吸附去除废水中亚甲基蓝性能.系列表征分析结果表明磁性复合材料表面疏松多孔,比表面积为63.01 m2/g,含有-COOH、-OH等丰富的官能团.在亚甲基蓝初始质量浓度为50 m...     

非共价修饰碳纳米管吸附水中亚甲基蓝研究

利用两亲聚合物聚乙烯吡咯烷酮(PVP)对碳纳米管(CNTs)进行非共价修饰,考察修饰后CNTs对水中污染物亚甲基蓝的吸附.研究体系pH、离子强度、PVP加入量等各种因素对修饰后CNTs吸附亚甲基蓝的影响.结果表明,在pH=8时,PVP浓度为12mg/L时修饰后CNTs对亚甲基蓝的吸附效果最好.离子强度对吸附容量影响很小...     

Preparation of TiN-WN composite particles for selective adsorption of methylene blue dyes in water

This study synthesizes TiN-WN composite nanoparticles with a broad Ti molar ratio, i.e., f_Ti ranging from 0.18 to 0.94, by a facile urea-assisted nitridation route at 800 °C in flowing nitrogen atmosphere. The particles comprise mainly mixtures of TiN and WN nanocrystallites when f_Ti ≤ 0.80. The composites show a selective adsorption against methylene blue (MB) dyes in water; to which, the adsorption under dark situations reaches as much as 90% within 90 min duration when using an initial MB concentration of 10^?5 M. In comparison, the composites show virtually negligible adsorption to methyl orange dye. This selective adsorption stems partly from the electrostatic interaction since surface of the composite particles bears a negative net charge for the cationic MB molecules. In addition, the composite particles also render a moderate photocatalytic degradation to the MB molecules under visible light illuminations.     

Relation between some two- and three-parameter isotherm models for the sorption of methylene blue onto lemon peel

Equilibrium uptake of methylne blue onto lemon peel was fitted to the 2 two-parameter isotherm models namely Freundlich and Langmuir and 3 six-parameter isotherm models namely Redlich-Peterson, Toth, Radke-Prausnitz, Fritz-Schluender, Vieth-Sladek and Sips isotherms by non-linear method. A comparison between two-parameter and three-parameter isotherms was reported. The best fitting isotherm was the Sips isotherm followed by Langmuir isotherm and Redlich-Peterson isotherm equation. Redlich-Peterson isotherm is a special case of Langmuir isotherm when the Redlich-Peterson isotherm constant g was unity. Radke-Prausnitz, Toth, Vieth-Sladek isotherm were the same when the Toth isotherm constant, n(T) and the Radke-Prausnitz isotherm, m(RP) are equal to unity and when the Vieth-Sladek isotherm constant, K(VS) equals zero. The sorption capacity of lemon peel for methylene blue uptake was found to be 29 mg/g.     

纤维素-海藻酸钠-海泡石多孔微球的制备及其对亚甲基蓝吸附性能

以微晶纤维素(Microcrystalline cellulose,MCC)和海藻酸钠(Sodium alginate,SA)为网络框架,海泡石(Sepiolite,SEP)为功能单元,采用悬浮液滴法构建纤维素-海藻酸钠-海泡石(MCC-SA-SEP)双网络多孔复合微球。通过SEM和TG对复合微球结构和热稳定性能进行表征,并研究该微球对亚甲基蓝(Methylene blue,MB)水溶液的吸附性能。结果表明,MCC-SA-SEP复合微球呈现三维网络多孔结构,且随着SEP含量的增加热稳定性逐渐提高。吸附结果显示MCC-SA-SEP符合准二级动力学模型和Langmuir等温线,对MB的饱和吸附容量高达333.3 mg/g。经过五次再生循环后,对MB吸附能力仍能维持85.4%,表明该多孔复合微球可以作为一种高效可再生的有机-无机复合吸附剂用于染料废水处理。      

Immobilization of Trichoderma viride for enhanced methylene blue biosorption: Batch and column studies

An efficient dye biosorbent was developed by entrapping a fungus mold, Trichoderma viride, within loofa sponge (LS) matirx. Immobilization enhanced the sorption of dye by 30% at equilibrium as compared with T. viride free biomass (TVFB). The maximum dye biosorption capacity of T. viride immobilized onto loofa sponge (TVILS) and TVFB was found to be 201.52 and 155.06 mg g⁻¹ biomass, respectively. The kinetics of dye removal by TVILS was rapid, with 84.3% sorption within the first 30 min and equilibrium after 90 min, whereas sorption by TVFB was slower as 61.4% dye was removed in first 30 min and equilibrium was achieved in 120 min. Biosorption kinetics and equilibria followed the pseudo-second-order and Langmuir adsorption models. FTIR spectroscopy of T. viride biomass showed that amine, hydroxyl, carbonyl and amide bonds were involved in the sorption of dye. Dye desorption from dye-laden TVILS with 0.1 M HCl was 99%. Regenerated TVILS was reusable without any appreciable decrease in its biosorption capacity during five repeated cycles. The dye removing capacity of TVILS in a continuous-flow column bioreactor was better than in batch-scale procedures. The study shows that TVILS has the potential of application as an efficient biosorbent for the removal of methylene blue from aqueous solutions.     

In situ green synthesis of Cu nanoparticles supported on natural Natrolite zeolite for the reduction of 4‐nitrophenol,congo red and methylene blue

This study demonstrates a clean, non‐toxic and environment friendly synthetic strategy for the preparation of the Natrolite zeolite/Cu nanoparticles (NPs) using Natrolite zeolite as a natural support and Anthemis xylopoda flowers aqueous extract as a reducing and stabilising agent for the synthesis of Cu NPs. Cu NPs with 20 nm diameter were immobilised homogeneously on the surface of Natrolite zeolite. The synthesised Natrolite zeolite/Cu NPs was used as an environmentally benign catalyst for the reduction of 4‐nitrophenol, congo red and methylene blue in aqueous media at an ambient temperature. It has been found that the catalyst can be reused several times without any decrease in activity.Inspec keywords: copper, zeolites, nanoparticles, nanofabrication, dyesOther keywords: copper nanoparticles, natural Natrolite zeolite, 4‐nitrophenol, congo red, methylene blue, Anthemis xylopoda flowers aqueous extract