Dye removal from wastewater using activated carbon developed from sawdust: adsorption equilibrium and kinetics

Mahogany sawdust was used to develop an effective carbon adsorbent. This adsorbent was employed for the removal of direct dyes from spent textile dyeing wastewater. The experimental data were analysed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The equilibrium adsorption capacity of the sawdust carbon was determined with the Langmuir equation as well as the pseudo-second-order rate equation and found to be >300 mg dye per gram of the adsorbent. The most ideal pH for adsorption of direct dyes onto sawdust carbon was found to be 3 and below. The results indicate that the Mahogany sawdust carbon could be employed as a low cost alternative to commercial activated carbon in the removal of dyes from wastewater.     

Removal of direct blue-106 dye from aqueous solution using new activated carbons developed from pomegranate peel: adsorption equilibrium and kinetics

The use of cheap, high efficiency and ecofriendly adsorbent has been studied as an alternative source of activated carbon for the removal of dyes from wastewater. This study investigates the use of activated carbons prepared from pomegranate peel for the removal of direct blue dye from aqueous solution. A series of experiments were conducted in a batch system to assess the effect of the system variables, i.e. initial pH, temperature, initial dye concentration adsorbent dosage and contact time. The results showed that the adsorption of direct blue dye was maximal at pH 2, as the amount of adsorbent increased, the percentage of dye removal increased accordingly but it decreased with the increase in initial dye concentration and solution temperature. The adsorption kinetics was found to follow pseudo-second-order rate kinetic model, with a good correlation (R(2)>0.99) and intra-particle diffusion as one of the rate determining steps. Langmuir, Freundlich, Temkin, Dubinin-RadushKevich (D-R) and Harkins-Jura isotherms were used to analyze the equilibrium data at different temperatures. In addition, various thermodynamic parameters, such as standard Gibbs free energy (DeltaG degrees ), standard enthalpy (DeltaH degrees ), standard entropy (DeltaS degrees ), and the activation energy (E(a)) have been calculated. The adsorption process of direct blue dye onto different activated carbons prepared from pomegranate peel was found to be spontaneous and exothermic process. The findings of this investigation suggest that the physical sorption plays a role in controlling the sorption rate.     

Effective removal of methylene blue from aqueous solution using a new magnetic iron oxide nanosorbent prepared by combustion synthesis

A magnetic iron oxide nanopowder (MnP) prepared by a new combustion technique was characterized and tested as adsorbent for methylene blue (MB) removal from aqueous solution. The effects of pH, adsorbent dose, initial dye concentration, contact time, and temperature on the amount of MB adsorbed were studied. The adsorption kinetics were described by a pseudo-second-order model, and the equilibrium experimental data were well fitted to the Langmuir isotherm, yielding a maximum adsorption capacity of 25.54 mg g^?1. The adsorption mechanism is governed by electrostatic forces and is highly dependent on the pH. The MnP adsorbent demonstrated excellent stability, showing good removal efficiency even after eight cycles of reuse, suggesting its potential large-scale application for the removal and recovery of MB from wastewater.     

Sequestration of nickel from aqueous solution onto activated carbon prepared from Parthenium hysterophorus L

In the present study, nickel removal efficiency of sulphuric acid-treated Parthenium carbon (SWC) from simulated wastewater has been investigated. Batch mode adsorption experiments have been conducted by varying pH, nickel concentration, adsorbent dose and contact time. Ni(II) removal was pH-dependent and found to be maximum at pH 5.0. The maximum removal of Ni(II) was achieved within 4h after the start of every experiment. The equilibrium adsorption data were fitted to Freundlich and Langmuir adsorption isotherm models to evaluate the model parameters. Both models represented the experimental data satisfactorily. The monolayer adsorption capacities of SWC as obtained from Langmuir isotherm was found to be 17.24 mg/g. The Lagergren first-order model was less applicable than pseudo-second-order reaction model. The adsorbent was also characterized including infrared spectroscopy and scanning electron microscopy. The FT-IR study indicated the presence of OH, CH, CO and CO groups in the adsorbent.     

Removal of rhodamine B from aqueous solution by adsorption onto sodium montmorillonite

The adsorption of rhodamine B dye was carried out using sodium montmorillonite clay. The effect of parameters such as pH, adsorbent dosage and initial dye concentration was studied. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best fit the equilibrium isotherm data. Langmuir adsorption capacity was found to be 42.19 mg/g. Kinetic data followed pseudo-second-order kinetics. Maximum color removal was observed at pH 7.0. The ΔG° value was found to be negative, the adsorption process was feasible. The results indicate that sodium montmorillonite clay can be used for the removal of basic dyes from aqueous solutions.     

Removal of Acid Violet 17 from aqueous solutions by adsorption onto activated carbon prepared from sunflower seed hull

The adsorption of Acid Violet 17 (AV17) was carried out using various activated carbons prepared from sunflower seed hull (SSH), an agricultural solid waste by-product. The effect of parameters such as agitation time, initial dye concentration, adsorbent dosage, pH and temperature were studied. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best report the equilibrium isotherm data. Langmuir adsorption capacity was found to be 116.27 mg/g. Kinetic data followed pseudo-second-order kinetics. Maximum colour removal was observed at pH 2.0. It was observed that the rate of adsorption improves with increasing temperature and the process is endothermic. The adsorbent surface was analysed with a scanning electron microscope. The results indicate that activated sunflower seed hull could be an attractive option for colour removal from dilute industrial effluents.     

Silica particles settling characteristics and removal performances of oxide chemical mechanical polishing wastewater treated by electrocoagulation technology

This study aimed at investigating the feasibility of using jackfruit peel (JFP), a solid waste, abundantly available in Malaysia, for the adsorption of methylene blue, a cationic dye. Batch adsorption studies were conducted to evaluate the effects of contact time, initial concentration (35-400mg/L), pH (2-11), and adsorbent dose (0.05-1.20g) on the removal of dye at temperature of 30 degrees C. The experimental data were analyzed by the four different types of linearized Langmuir isotherm, the Freundlich isotherm and the Temkin isotherm. The experimental data fitted well with the type 2 Langmuir model with a maximum adsorption capacity of 285.713mg/g. Pseudo-first and pseudo-second-order kinetics models were tested with the experimental data, and pseudo-second-order kinetics was the best for the adsorption of MB by JFP with coefficients of correlation R(2)> or =0.9967 for all initial MB concentrations studied. The results demonstrated that the JFP is very effective for the adsorption of methylene blue (MB) from aqueous solutions.     

Cross-linked quaternary chitosan as an adsorbent for the removal of the reactive dye from aqueous solutions

Adsorption of reactive orange 16 by quaternary chitosan salt (QCS) was used as a model to demonstrate the removal of reactive dyes from textile effluents. The polymer was characterized by infrared (IR), energy dispersive X-ray spectrometry (EDXS) analyses and amount of quaternary ammonium groups. The adsorption experiments were conducted at different pH values and initial dye concentrations. Adsorption was shown to be independent of solution pH. Three kinetic adsorption models were tested: pseudo-first-order, pseudo-second-order and intraparticle diffusion. The experimental data best fitted the pseudo-second-order model, which provided a constant velocity, k₂, of 9.18 × 10⁻⁴ g mg⁻¹ min⁻¹ for a 500 mg L⁻¹ solution and a value of k₂, of 2.70 × 10⁻⁵ g mg⁻¹ min⁻¹ for a 1000 mg L⁻¹ solution. The adsorption rate was dependent on dye concentration at the surface of the adsorbent for each time period and on the amount of dye adsorbed. The Langmuir isotherm model provided the best fit to the equilibrium data in the concentration range investigated and from the isotherm linear equation, the maximum adsorption capacity determined was 1060 mg of reactive dye per gram of adsorbent, corresponding to 75% occupation of the adsorption sites. The results obtained demonstrate that the adsorbent material could be utilized to remove dyes from textile effluents independent of the pH of the aqueous medium.     

A novel agricultural waste adsorbent for the removal of cationic dye from aqueous solutions

In this paper, pineapple stem (PS) waste, an agricultural waste available in large quantity in Malaysia, was utilized as low-cost adsorbent to remove basic dye (methylene blue, MB) from aqueous solution by adsorption. Batch mode experiments were conducted at 30 degrees C to study the effects of initial concentration of methylene blue, contact time and pH on dye adsorption. Equilibrium adsorption isotherms and kinetic were investigated. The experimental data were analyzed by the Langmuir and Freundlich models and the isotherm data fitted well to the Langmuir isotherm with monolayer adsorption capacity of 119.05mg/g. The kinetic data obtained at different concentrations were analyzed using a pseudo-first-order and pseudo-second-order equation and intraparticle diffusion equation. The experimental data fitted very well the pseudo-second-order kinetic model. The PS was found to be very effective adsorbent for MB adsorption.     

Removal of Basic Red 46 dye from aqueous solution by adsorption onto Moroccan clay

In this study, Moroccan crude clay of Safi, which was characterized by X-ray diffraction, is used as adsorbent for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the Basic Red 46 (BR46) in aqueous solutions at various dye concentrations, adsorbent masses and pH values. The results showed that the adsorption capacity of the dye increased by initial dye concentration and pH values. Two kinetic models (the pseudo-first-order and the pseudo-second-order) were used to calculate the adsorption rate constants. The adsorption kinetics of the basic dye followed pseudo-second-order model. The experimental data isotherms were analyzed using the Langmuir, Freundlich and Dubinin–Radushkevish equations. The monolayer adsorption capacity for BR46 dye is 54 mg/g of crude clay. Nearly 20 min of contact time was found to be sufficient for the dye adsorption to reach equilibrium. Thermodynamical parameters were also evaluated for the dye–adsorbent system and revealed that the adsorption process is exothermic in nature.     

Adsorptive removal of cationic (BY2) dye from aqueous solutions onto Turkish clay: Isotherm,kinetic, and thermodynamic analysis

ABSTRACT

The removal of Basic Yellow 2 (BY2), a cationic dye, from aqueous solution by using montmorillonite as adsorbent was studied in batch experiments. The effect of pH, agitation speed, adsorbent dosage, initial dye concentration ionic strength, and temperature on the removal of BY2 was also investigated. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms were applied to fit the adsorption data of BY2 dye. Equilibrium data were well described by the typical Langmuir adsorption isotherm. The maximum monolayer adsorption capacity was calculated as 434.196 mg g^?1 from the Langmuir isotherm model. The adsorption data was fitted to both the pseudo-first-order, pseudo-second-order, Elovich, and intraparticle kinetic models, and the calculated values of the amount adsorbed at equilibrium (q_e) by pseudo-second-order equations were found to be in good agreement with the experimental values. The thermodynamic factors were also evaluated. The entropy change (ΔS*) was negative, suggesting that the adsorption process decreases in entropy and enthalpy change (ΔH*) was positive which indicates endothermic nature. The positive ΔG* value confirms the un-spontaneity of the process. In addition, a semiempirical model was calculated from kinetic data.     

Environmental risk index: a tool to assess the safety of dams for leachate

Bagasse-based ion adsorbent was prepared by chemically modifying bagasse with acrylonitrile and hydroxylamine with the aim to enhance the ability of removal heavy metal ions from wastewater. The purified modified materials were characterized by Fourier transform infrared (FT-IR). Batch experiments of Cu(II) ions (Cu(2+)) adsorption on the bagasse adsorbent were performed. Effects of the adsorbent dosage, initial pH of the solution, temperature of the Cu(2+) solution, and initial Cu(2+) concentration on the adsorption of Cu(2+) were studied, respectively. Langmuir and Freundlich models were applied to describe the adsorption isotherm of Cu(2+) by bagasse adsorbent. The results indicated that Langmuir model fitted the adsorption equilibrium data better than the Freundlich isotherm model. Two kinetic models, including pseudo-first-order and pseudo-second-order, were also used to analyze the Cu(2+) adsorption process, and the results showed that the pseudo-second-order with correlation coefficients greater than 0.999 was more suitable than pseudo-first-order.     

Removal of hazardous dye congored from waste material

The present paper is aimed to investigate and develop cheap adsorption methods for color removal from wastewater using waste material sawdust as adsorbent. Sawdust, a biosorbent, was successfully utilized in removing a water soluble azo dye, congored from wastewater. The paper incorporates effect of pH, temperature, amount of adsorbent, contact time, concentration of adsorbate, particle size on adsorption. Specific rate constants of the processes were calculated by kinetic measurements and a first order adsorption kinetics was observed in each case. Langmuir and Freundlich adsorption isotherm models were then applied to calculate thermodynamics parameters as well as to suggest the plausible mechanism of the ongoing adsorption processes. In order to observe the quality of wastewater COD measurements were also carried out before and after the treatments. A significant decrease in the COD values was observed, which clearly indicates that adsorption method offer good potential to remove congored from wastewater.     

Removal of Reactofix golden yellow 3 RFN from aqueous solution using wheat husk--An agricultural waste

The wheat husk, an agricultural by-product, has been activated and used as an adsorbent for the adsorption of Reactofix golden yellow 3 RFN from aqueous solution. In this work, adsorption of Reactofix golden yellow 3 RFN on wheat husk and charcoal has been studied by using batch studies. The equibrium adsorption level was determined to be a function of the solution pH, adsorbent dosage, dye concentration and contact time. The equilibrium adsorption capacities of wheat husk and charcoal for dye removal were obtained using Freundlich and Langmuir isotherms. Thermodynamic parameters such as the free energies, enthalpies and entropies of adsorption were also evaluated. Adsorption process is considered suitable for removing color, COD from wastewater.     

Functionalization of powdered walnut shell with orthophosphoric acid for Congo red dye removal

This study investigates the adsorption of Congo red dye on walnut shell powder based activated carbon in batch process (WNAA). Walnut shell powder was carbonized by treating with phosphoric acid (H₃PO₄), and the adsorbent was characterized using Fourier Transform-Infrared spectrophotometer (FT-IR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), and pH point of zero charge (pH_pzc), respectively. Operational parameters such as contact time, initial dye concentration, and pH were investigated using batch-adsorption techniques. The adsorption uptake was found to increase with increase in initial dye concentration and contact time. The optimum CR dye uptake was observed at pH 3.12 corresponding to 94.53% removal. Pseudo-first-order, pseudo-second-order, Elovich, and Intraparticle diffusion kinetic models were used to test the adsorption data. The pseudo-second order exhibited the best fit out of the four kinetic models used. Equilibrium data were fitted to the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. Langmuir model fitted the adsorption data most with maximum monolayer coverage of 40?mg/g. Thermodynamic parameters such as Gibbs free energy, enthalpy, entropy, and the activation energy were determined. It was found that Congo red dye adsorption was spontaneous and endothermic. 0.02M Hydrochloric acid was used to regenerate the adsorbent prepared, and the regenerated adsorbent was used for dye adsorption. Congo red dye adsorption capacity ranged from 90% to 93% at three consecutive times. This study has shown that walnut shell is a good adsorbent in the treatment of Congo red dye from aqueous solutions.     

Synthesis and characterization maleate-alumoxane nanoparticles for removal of reactive yellow 84 dye from aqueous solution

Maleate-alumoxane nanoparticles (Mal-A) were synthesized from boehmite and applied for adsorption of an azo dye (Reactive Yellow 84) from aqueous solution. Its adsorption capacity was compared with three types of carboxylate alumoxane nanoparticles synthesized from boehmite including salicylate alumoxane (Sal-A), para-aminobenzoate alumoxane (Pab-A) and fumarate alumoxane (Fum-A). The characterizations of prepared materials were analyzed using FTIR, SEM, X-ray diffraction and BET measurements. Among utilized alumoxanes at natural pH, the adsorption capacity of Mal-A was 45, 67, 116 and 215% higher than that of Fum-A, Boehmite, Pab-A, Sal-A nanoparticles, respectively. Response surface methodology (RSM) using Box-Behnken design of experiment was employed to investigate the influence of pH, initial concentration of dye and adsorbent dosage on dye removal efficiency of Mal-A. Box-cox transformation was chosen to improve model adequately and a good prediction (R²: 0.998) was achieved. Under optimum condition, i.e., pH: 4.3, dye concentration: 151.5 mg/L and adsorbent dosage: 1.2 g/L, the adsorption capacity and dye removal efficiency were obtained 130.6 mg/g and 99.2%, respectively. The kinetics and equilibrium data were perfectly represented with linear pseudo-second-order and linear Langmuir isotherm models, respectively.     

Scavenging behaviour of meranti sawdust in the removal of methylene blue from aqueous solution

Meranti (Philippine mahogany) sawdust, an inexpensive material, showed strong scavenging behaviour through adsorption for the removal of methylene blue (MB) from aqueous solution. Batch studies were performed to evaluate and optimize the effects of various parameters such as contact time, pH, initial dye concentrations and adsorbent dosage. Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The experimental data fitted well with the Langmuir adsorption isotherm, indicating thereby the mono layer adsorption of the dye. The monolayer sorption capacity of meranti sawdust for MB was found to be 120.48, 117.64, 149.25 and 158.73 mg/g at 30, 40, 50 and 60 °C, respectively. Thermodynamic calculations showed that the MB adsorption process is endothermic and spontaneous in nature. Kinetic studies showed that the adsorption followed a pseudo-second-order kinetic model. The results indicated that the meranti sawdust could be an alternative material in place of more costly adsorbents used for dye removal.     

Removal of Neutral Red from aqueous solution by adsorption on spent cottonseed hull substrate

Cottonseed hull, a low-cost widely available agricultural waste in China, after used as substrate for the white rot fungus Pleurotus ostreatus cultivation, was tested for the removal of Neutral Red (NR), a cationic dye, from aqueous solution. A batch adsorption study was carried out with varied solution pH, adsorbent dosage, reaction time and initial NR concentration. The results show that the kinetics of dye removal by the spent cottonseed hull substrate (SCHS) is prompt in the first 5 min and the adsorption equilibrium can be attained after 240 min. The biosorption kinetics and equilibrium follow typical pseudo-second-order and Langmuir adsorption models. Thermodynamic parameters of ΔG°, ΔH° and ΔS° show that the adsorption is a spontaneous and endothermic process. Fourier transform infrared (FTIR) spectroscopy was used for the characterization of possible dye-biosorbent interaction. This study provides a facile method to produce low-cost biosorbent for the purification of dye contaminated water.     

Poly(methylmethacrylate) grafted chitosan: An efficient adsorbent for anionic azo dyes

Present study reports on peroxydisulfate/ascorbic acid initiated synthesis of Chitosan-graft-poly(methylmethacrylate) (Ch-g-PMMA) and its characterization by FTIR, XRD and (13)C NMR. The copolymer remained water insoluble even under highly acidic conditions and was evaluated to be an efficient adsorbent for the three anionic azo dyes (Procion Yellow MX, Remazol Brilliant Violet and Reactive Blue H5G) over a wide pH range of 4-10 being most at pH 7. The adsorbent was also found efficient in decolorizing the textile industry wastewater and was much more efficient than the parent chitosan. Equilibrium sorption experiments were carried out at different pH and initial dye concentration values. The experimental equilibrium data for each adsorbent-dye system were successfully fitted to the Langmuir and Freundlich sorption isotherms. Based on Langmuir model Q(max) for yellow, violet and blue dyes was 250, 357 and 178, respectively. Thermodynamic parameters of the adsorption processes such as DeltaG degrees , DeltaH degrees , and DeltaS degrees were calculated. The negative values of free energy reflected the spontaneous nature of adsorption. The adsorption kinetic data of all the three dyes could be well represented by pseudo-second-order model with the correlation coefficients (R(2)) being 0.9922, 0.9997 and 0.9862, for direct yellow, reactive violet and blue dye, respectively with rate constants 0.91 x 10(-4), 1.82 x 10(-4) and 1.05 x 10(-4) g mg(-1)min(-1), respectively. At pH 7, parent chitosan also showed pseudo-second-order kinetics. The temperature dependence of dye uptake and the pseudo-second-order kinetics of the adsorption indicated that chemisorption is the rate-limiting step that controls the process.