Removal of Reactive Red 198 from aqueous solution by combined method multi-walled carbon nanotubes and zero-valent iron:Equilibrium,kinetics, and thermodynamic

Dyes often include toxic,carcinogenic compounds and are harmful to humans' health.Therefore,removal of dyes from textile industry wastewater is essential.The present study aimed to evaluate the efficiency of the combination of zero valent iron(ZVI) powder and multi-walled carbon nanotubes(MWCNTs) in the removal of Reactive Red 198(RR198) dye from aqueous solution.This applied research was performed in a batch system in the laboratory scale.This study investigated the effect of various factors influencing dye removal,including contact time,p H,adsorbent dose,iron powder dose,initial dye concentration,and temperature.The equilibrium adsorption data were analyzed using three common adsorption models:Langmuir,Freundlich and Temkin.Besides,kinetic and thermodynamic parameters were used to establish the adsorption mechanism.The results showed,in pH =3,contact time = 100 min,ZVI dose = 5000 mg·L~(-1),and MWCNTs dose = 600 mg·L~(-1)in 100 mg·L~(-1)dye concentration,the adsorption efficiency increased to 99.16%.Also,adsorption kinetics was best described by the pseudo-second-order model.Equilibrium data fitted well with the Freundlich isotherm(R2= 0.99).The negative values of ΔG0and the positive value of ΔH0(91.76) indicate that the RR198 adsorption process is spontaneous and endothermic.According to the results,the combination of MWCNTs and ZVI was highly efficient in the removal of azo dyes.     

Removal of diazo and triphenylmethane dyes from aqueous solutions through an adsorption process

Direct Red 31, Acid Black 1 and Acid Green 16 belonging to diazo and triphenylmethane classification of dye chemicals are widely used during the manufacture of leather. The spent dyestuffs in wastewater escape biological treatment owing to their poor biodegradability. An adsorption procedure was used in this study for the removal of dyes from aqueous solution using Rice Bran‐based Activated Carbon (RBAC). The molecular weight of the dye chemicals, the mass of RBAC and the diameter of RBAC particle had positive effects on the rate of adsorption. Initial concentration of dye chemicals, pH of the dye solution and temperature of adsorption showed a negative impact on adsorption. The enthalpies of adsorption for Direct Red 31, Acid Black 1 and Acid Green 16 were −32.1,−23.4 and −21.7 KJ mol⁻¹ respectively, indicating the adsorption was an exothermic physical process. The entropies of adsorption for Direct Red 31, Acid Black 1 and Acid Green 16 were −96.94,−59.92 and −26.96 J K⁻¹ mol ⁻¹ respectively, suggesting that RBAC favours the adsorption process. © 1999 Society of Chemical Industry     

Study of the kinetics of the adsorption by activated carbons of 2,4,5-trichlorophenoxyacetic acid from aqueous solution

The kinetics of the adsorption of 2,4,5-trichlorophenoxyacetic acid by activated carbons from an aqueous solution has been studied at several temperatures (10°C to 50°C). The activated carbons used were Merck (No. 2514) and one prepared from almond shells (C-A-14). The adsorption process seems to be of the order two and the desorption of the order one. The thermodynamic functions for the formation of the activated complex have also been calculated.     

Removal of manganese from water by electrocoagulation: Adsorption,kinetics and thermodynamic studies

The present study provides an electrocoagulation process for the removal of manganese (Mn) from water using magnesium as anode and galvanised iron as cathode. The various operating parameters like effect of initial pH, current density, electrode configuration, inter‐electrode distance, coexisting ions and temperature on the removal efficiency of Mn were studied. The results showed that the maximum removal efficiency of 97.2% at a pH of 7.0 was achieved at a current density 0.05 A/dm² with an energy consumption of 1.151 kWhr/m³. Thermodynamic parameters, including the Gibbs free energy, enthalpy and entropy, indicated that the Mn adsorption of water on magnesium hydroxides was feasible, spontaneous and endothermic. The experimental data were fitted with several adsorption isotherm models to describe the electrocoagulation process. The adsorption of Mn preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. In addition, the adsorption kinetic studies showed that the electrocoagulation process was best described using the second‐order kinetic model at the various current densities. © 2012 Canadian Society for Chemical Engineering     

Removal of textile dye from aqueous solution by electrochemical method

The use of adsorption and electrochemical treatment technologies for wastewater treatment has significantly increased in recent years. In the present study, carbon prepared from biomass waste can be used as electrode material in the electrochemical process is shown. Given that the electrode material is quite expensive, low-cost manufacturing is gaining more and more importance. Electroadsorption of textile dye (Burdem Orange II) by using activated carbon prepared from waste material, which is cherry stones, was investigated with the variation in the parameters of pH, initial dye concentration, solution flow rate, applied potential, and supporting electrolyte. The removal efficiency of textile dye up to 98% were achieved by electrochemical method.     

Removal of Rhodamine B from aqueous solutions and wastewater by walnut shells: kinetics,equilibrium and thermodynamics studies

An adsorption study of Rhodamine B (RB) dye from aqueous solutions was carried out using walnut shells pretreated by different methods. In addition to the effects of the pretreatment, the effects of various parameters like pH, adsorbent dose, contact time, initial dye concentration and temperature on the adsorption of RB was studied. The adsorption process was highly pH dependent and a maximum adsorption was achieved at pH 3.0. The best fit for the rates of dye adsorption was a pseudo-second-order kinetic model with good correlation coefficients (R²>0.99). Langmuir isotherms were used to determine that the maximum loading capacity of the different walnut shells and the RB capacities ranged from 1.451–2.292 mg·g^-1. The dye adsorption was also evaluated thermodynamically. Positive standard enthalpy (?H°) values were obtained indicating that the RB adsorption process is endothermic as well as ?G° and ?S° values showed that adsorption process is spontaneous with an increased randomness at the solid-liquid interface. Desorption studies were carried out to explore the feasibility of regenerating the used walnut shells and it was found that 97.71%–99.17% of the retained RB was recovered with 0.1 mol?L^-1 NaOH solution. The walnut shells were also successfully used to remove RB from industrial effluents.     

Lead recovery from aqueous environment by using porous carbon of citrus fruits waste: equilibrium,kinetics and thermodynamic studies

ABSTRACT

The mixture of citrus fruits (orange, grapefruit, mandarin, and lemon) wastes was utilized to obtain high surface area activated carbon (AC) by H₃PO₄ activation. The production conditions were optimized and the optimum conditions were determined. The optimal-activated carbon (CFWAC) was characterized by various physicochemical techniques. CFWAC was also used as a sorbent for Pb (II) ions from water. Batch experiments were performed to explore the adsorption capacity and mechanism. The Langmuir isotherm and pseudo-second-order kinetic model showed good fitness to the experimental data. The maximum Pb (II) adsorption capacity of CFWAC was found to be 163.93 mg/g.     

Removal of Neutral Red from aqueous solution by using modified hectorite

The object of this work was to study the modified hectorite as effective adsorbent for Neutral Red (NR) from aqueous solution. The adsorbent capacity of modified hectorite was discussed. The effects of surfactant content, adsorbent content, pH and adsorption temperature on the sorption of NR on modified hectorite were studied. Experimental results showed that the equilibrium adsorption data fitted well with Langmuir isotherm and the adsorption capacity was 393.70 mg/g for the modified cetylpyridinium bromide hectorite (CPB-Hect). Kinetic studies showed that the dynamical data fitted well with the pseudo-second-order kinetic model. For thermodynamic studies, parameters such as the Gibbs free energy (ΔG⁰), the enthalpy (ΔH⁰) and the entropy (ΔS⁰) indicated that the adsorption process was spontaneous and endothermic in nature.     

Kinetics and equilibrium studies of removal of an azo dye from aqueous solution by adsorption onto scallop

In the present work removal of an azo dye (Reactive Black 5) was investigated from aqueous solution by adsorption onto scallop as a low-cost and widely available adsorbent. The effect of various operational parameters, such as contact time, pH, initial dye concentration and adsorbent dosage on the removal efficiency of dye was studied. Removal efficiency declined with the increase in solution pH and initial dye concentration but with the decrease in adsorbent dosage. Experimental equilibrium and kinetics data were fitted by Langmuir and Freundlich isotherms and pseudo-first-order and pseudo-second-order kinetic models, respectively.     

Adsorption of butanol from aqueous solution onto a new type of macroporous adsorption resin: Studies of adsorption isotherms and kinetics simulation

BACKGROUND: Owing to the rapid depletion of petroleum fuel, the production of bio‐butanol has attracted much attention. However, low butanol productivity severely limits its potential industrial application. It is important to establish an approach for recovering low‐concentration butanol from fermentation broth. Experiments were conducted using batch adsorption mode under different conditions of initial butanol concentration and temperature. Batch adsorption data were fitted to Langmuir and Freundlich isotherms and the macropore diffusion, pseudo‐first‐ and second‐order models for kinetic study. RESULTS: The maximum adsorption capacity of butanol onto KA‐I resin increase with increasing temperature, ranged from 139.836 to 304.397 mg g^?1. The equilibrium adsorption data were well fitted by the Langmuir isotherm. The adsorption kinetics was more accurately represented by the macropore diffusion model, which also clearly predicted the intraparticle distribution of the concentration. The effective pore diffusivity (D_p) was dependent upon temperature, but independent of initial butanol concentration, and was 0.251 × 10^?10, 0.73 × 10^?10, 1.32 × 10^?10 and 4.31 × 10^?10 m² s^?1 at 283.13, 293.13, 303.13 and 310.13 K, respectively. CONCLUSION: This work demonstrates that KA‐I resin is an efficient adsorbent for the removal of butanol from aqueous solutions and available for practical applications for future in situ product recovery of butanol from ABE fermentation broth. Copyright © 2012 Society of Chemical Industry     

花生壳制活性炭及其脱六价铬研究

本文研究了用花生壳制备活性炭和用此活性炭去除水溶液中的Cr（Ⅵ）。采用化学活化法,即用H2SO4、H3PO4、ZnCl2、KOH活化花生壳中的炭。同时研究了这些活化剂的浓度和用量、热解时间和温度对活性炭性能的影响。采用亚甲基蓝吸附实验评价活性炭的性能。结果表明H3PO4和ZnCl2是良好的活化剂,KOH和H2SO4效果较差。溶液的pH值对活性炭吸附Cr（Ⅵ）的能力有很大影响。活性炭的吸附能力随着pH值的降低而升高,同时在不同的pH值下,炭的吸附速率也不同。pH值越低,Cr（Ⅵ）被吸附的越快。等温实验结果表明,在pH值等于2时,用H3PO4和ZnCl2活化的活性炭对Cr（Ⅵ）的吸附能力分别达到125．0和83．3mg·g^-1。花生壳活性炭吸附Cr（Ⅵ）的机理比较复杂,与溶液的pH值有关。在pH值等于2时,等温吸附可以用Langmuir模型模拟;在pH值等于2～7时,可以用Freundlich模型模拟。     

Removal of Congo Red dye from aqueous solution using Amberlite IRA-400 in batch and fixed bed reactors

Removal of Congo Red (CR) azo dye by adsorption process using Amberlite IRA-400 resin was evaluated in both batch and fixed bed system. From the batch adsorption results, maximum loading efficiency (99.99%) of CR dye was obtained at the conditions pH 4.5, temp. 303?K, contact time 180?min., Amberlite IRA-400 dose 0.5?g. The isotherm study ascertained on favorability of adsorption process as the value of separation factor (K_L?=?0.88) and Freundlich constant (1/n?=?0.96?R²?=?0.99) than Freundlich model (R²?=?0.97). The kinetic data studied at three different CR dye concentration (50, 75, 100?mg) and results were fitted with both pseudo-first-order and second-order model equations. The values of R² obtained are of 0.95 and 0.99 for former and later one, respectively, ensuring on best fitting of pseudo-second-order kinetics and also suggesting about the chemisorptions type of adsorption. The bed depth service model was applied for competitive analysis of the CR dye adsorption in column variables indicating mass transfer from aqueous solution to Amberlite IRA-400 phase. Fourier transform infrared analysis of CR-loaded resin Amberlite IRA-400 showed a band shifted from 1057 to 1130?cm^?1 confirming CR adsorption with Amberlite IRA-400. Scanning electron microscope analysis of resin before and after adsorption was well evident from the phase patterns. Selective separation of CR dye from waste effluent of a textile industry bearing CR dye along with other trace heavy metal was achieved.     

Adsorption of cadmium and zinc from aqueous solution on natural and activated bentonite

The adsorption of cadmium and zinc ions on natural bentonite heat-treated at 110°C or at 200°C and on bentonite acid-treated with H₂SO₄ (concentrations: 0·5 mol dm^?3 and 2·5 mol dm^?3), from aqueous solution at 30°C has been studied. The adsorption isotherms corresponding to cadmium and zinc may be classified respectively as H and L types of the Giles classification which suggests the samples have respectively a high and a medium affinity for cadmium and zinc ions. The experimental data points have been fitted to the Langmuir equation in order to calcualte the adsorption capacities (X_m) and the apparent equilibrium constants (K_a) of the samples; X_m and K_a values range respectively for 4·11 mg g^?1 and 1·90 dm³ g^?1 for the sample acid-treated with 2·5 mol dm^?3 H₂SO₄ [(B)-A(2·5)] up to 16·50 mg g^?1 and 30·67 dm³ g^?1 for the natural sample heat-treated at 200°C [B-N-200], for the adsorption process of cadmium, and from 2·39 mg g^?1 and 0·07 dm³ g^?1, also for B-A(2·5), up to 4·54 mg g^?1 and 0·45 dm³ g^?1 [B-N-200], for the adsorption process of zinc. X_m and K_a values for the heat-treated natural samples were higher than those corresponding to the acid-treated ones. The removal efficiency (R) has also been calculated for every sample; R values ranging respectively from 65·9% and 8·2% [B-A(2·5)] up to 100% and 19·9% [B-N-200], for adsorption of cadmium and zinc.     

Removal of strontium from aqueous solutions by adsorption onto activated carbon: kinetic and thermodynamic studies

This work reports the adsorption of strontium from aqueous solutions onto activated carbon. Various factors such as pH, initial concentration of strontium, particle size and temperature were considered. The optimum conditions obtained were: pH value = 4.0, contact time = 8 h, initial concentration of Sr(II) = 100 mg/l, particle size = 270 μm and temperature of 293.15 K. The adsorption of strontium(II) on activated carbon follows pseudo-first order kinetics and the energy of activation E_a calculated using the Arrehenius equation was found to be 3.042 kJ/mol.The adsorption isotherms could be fitted by the Langmuir model with the maximum adsorption capacity Q_o being 5.07×10^–4 mol/g at 293.15 K. A dimensionless separation factor R_L was used to judge the favourable adsorption. The values of the mass transfer coefficient β_L (cm/s) at different temperatures indicated that the velocity of mass transfer of Sr(II) ions onto activated carbon was slow. The intraparticle diffusion mechanism is of great importance in determining the overall rate of removal and the negative entropy of activation ΔS^# value 145.13 J/mol K, reflects that no significant change occurs in the internal structure of activated carbon during adsorption of strontium(II). The Gibbs free energy ΔG°_ads values range from –36.61 kJ/mol to –41.75 kJ/mol at 293.15–333.15 K, which show the physical adsorption properties of activated carbon and indicate the feasibility of the process.     

Removal of metal ions from aqueous solution by activated carbons obtained from different raw materials

The adsorption of Pb²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ from aqueous solution at 293 K by activated carbons obtained from different raw materials was studied. These carbons were prepared by water vapour pyrolysis of the raw materials—apricot stones, coconut shells and lignite coal. The influence of the solution pH on the adsorption processes has been studied. The presence of other metal ions in the solution decreases the adsorption of each of the ions. The selective adsorption of the metal ions is observed but the ones preferentially adsorbed do not completely prevent the adsorption of other ions. The chemical nature of the carbon surface and metal ions have great significance for the adsorption process.     

Adsorption of cationic dye on N,O-carboxymethyl-chitosan from aqueous solutions: equilibrium, kinetics, and adsorption mechanism

In order to improve the adsorption capacity of chitosan (CTS) for methylene blue (MB) cationic dye, a series of N,O-carboxymethyl-chitosans (N,O-CMCTS) were prepared under heterogeneous conditions by controlling the reaction time. The adsorption of MB from aqueous solution onto N,O-CMCTS was studied. The effects of degree of substitution (DS) of N,O-CMCTS, initial pH of the dye solution and adsorption temperature were investigated in detail. The results showed that the adsorption capacities of N,O-CMCTS increased with the increase of DS and N,O-CMCTS with DS of 0.72 exhibited the highest adsorption capacity (349 mg/g). The adsorption kinetics of N,O-CMCTS was found to follow the pseudo-second-order model. The adsorption equilibrium of N,O-CMCTS fitted very well with the Langmuir isotherm model, showing maximum monolayer adsorption capacity of 351 mg/g. The adsorption mechanism of N,O-CMCTS was also discussed by means of FTIR spectra and XPS. The results revealed that the –OH, –NH₂, and –COOH groups of N,O-CMCTS were involved in the adsorption process. The desorption studies showed that N,O-CMCTS could be regenerated and used for the adsorption of MB repeatedly.     

A novel agricultural waste based adsorbent for the removal of Pb(II) from aqueous solution: Kinetics,equilibrium and thermodynamic studies

Fig sawdust was used as a precursor for the production of activated carbon by chemical activation with H₃PO₄. The developed Fig sawdust activated carbon (FSAC) was used as a biosorbent for the removal of Pb(II) from aqueous solution. Highest adsorption of Pb(II) (95.8%) was found at pH 4. Equilibrium data fitted very well with the Langmuir isotherm model. Maximum adsorption capacity was determined 80.645 mg g⁻¹ at pH 4. Kinetic studies demonstrated that the adsorption followed a pseudo second order kinetics model. The negative value of ΔG° confirmed the feasibility and spontaneity of FSAC for Pb(II) adsorption.     

Kinetic,equilibrium and thermodynamic studies on removal of Cr(VI) by activated carbon prepared from Ricinus communis seed shell

A study on the removal of hexavalent chromium ions from aqueous solution by using activated carbon prepared from Ricinus communis has been done. In this process, it was carbonised and activated by treating with concentrated sulphuric acid followed by heating for 5 h at 500°C. Batch adsorption experiments are also carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature. The experimental data are fitted well to the Freundlich adsorption isotherm. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° are calculated, which indicated that the adsorption is spontaneous and endothermic in nature. Adsorbent used in this study is characterised by FT‐IR and SEM before and after the adsorption of Cr(VI). © 2011 Canadian Society for Chemical Engineering     

Removal Of methylene blue dye from simulated wastewater by alginic acid fiber as adsorbent: Equilibrium,kinetic, and thermodynamic studies

Alginic acid fiber was used as a novel adsorbent to remove methylene blue from aqueous solution, and adsorption mechanisms were investigated. System variables, including contact time, pH, temperature, and initial concentration were examined to investigate the effect on adsorption in batch experiments. The results showed that equilibrium reached in less than 20 min and pH significantly influenced the equilibrium value. Langmuir, Freundlich, and Temkin isotherm models were employed to analyse the isotherm behaviours. It was found the isotherm behaviours conform to Freundlich and Temkin models well, indicating a chemisorption process. Pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion models were employed to investigate kinetic behaviours. The kinetic behaviour is best described by pseudo‐second‐order model. Thermodynamic parameters indicate that the process is spontaneous and exothermic.     

Removal of copper ions from aqueous solution by adsorption using LABORATORIES-modified bentonite (organo-bentonite)

Equilibrium, kinetic and thermodynamic aspects of the adsorption of copper ions from an aqueous solution using linear alkylbenzene sulfonate (LABORATORIES) modified bentonite (organo-bentonite) are reported. Modification of bentonite was performed via microwave heating with a concentration of LABORATORIES surfactant equivalent to 1.5 times that of the cation exchange capacity (CEC) of the raw bentonite. Experimental parameters affecting the adsorption process such as pH, contact time and temperature were studied. Several adsorption equations (e.g., Langmuir, Freundlich, Sips and Toth) with temperature dependency were used to correlate the equilibrium data. These models were evaluated based on the theoretical justifications of each isotherm parameter. The Sips model had the best fit for the adsorption of copper ions onto organo-bentonite. For the kinetic data, the pseudo-second order model was superior to the pseudo-first order model. Thermodynamically, the adsorption of copper ions occurs via chemisorption and the process is endothermic (ΔH⁰>0), irreversible (ΔS⁰>0) and nonspontaneous (ΔG⁰>0).