Scavenging Rhodamine B dye using moringa oleifera seed pod

Moringa oliferia seed pod was modified using orthophosphoric acid (H₃PO₄) and used as adsorbent for sequestering Rhodamine B (Rh-B) dye from aqueous solution. The acid-modified adsorbent (MOSPAC) was characterized using Scanning Electron microscopy (SEM), Fourier Transform Infra Red (FTIR), Energy Dispersive X-ray (EDX), pH point of zero charge (pH_pzc) and Boehm Titration (BT) techniques, respectively. Operational parameters such as contact time, initial dye concentration, adsorbent dosage, pH and solution temperature were studied in batch process. Optimum dye adsorption was observed at pH 3.01. Equilibrium adsorption data was tested data using four different isotherm models: Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. Langmuir isotherm model fitted most with maximum monolayer adsorption capacity of 1250 mg g^–1. Pseudo-second-order kinetic model provided the best correlation for the experimental data. Thermodynamic study showed that the process is endothermic, spontaneous and feasible. MOSPAC is an effective adsorbent for the removal of RhB dye from aqueous solutions.     

Removal of Astrazon Yellow 7GL from aqueous solutions by adsorption onto wheat bran

Adsorption kinetic and equilibrium of a basic dye (Astrazon Yellow 7GL) from aqueous solutions at various initial dye concentration (50-300 mg/l), pH (4-10), adsorbent dosage (2-8 g/l), particle size (354-846 microm) and temperature (30-50 degrees C) on wheat bran were studied in a batch mode operation. The result showed that the amount adsorbed of the dye increased with increasing initial dye concentration and contact time, whereas particle size and pH had no significant affect on the amount of dye adsorbed by the adsorbent. A comparison of kinetic models on the overall adsorption rate showed that dye/adsorbent system was best described by the pseudo second-order rate model. The removal rate was also dependent on both external mass transfer and intra-particle diffusion. The low value of the intraparticle diffusivity, 10(-11) cm2/s, indicated the significant influence of intraparticle diffusion on the kinetic control. The adsorption capacity (Q0) calculated from the Langmuir isotherm was 69.06 mg/g for at pH 5.6, 303 K for the particle size of 354 microm. The experimental data yielded excellent fits with Langmuir and Tempkin isotherm equations. Different thermodynamic parameters showed that the reaction was spontaneous and endothermic in nature.     

A sustainable process for adsorptive removal of methylene blue onto a food grade mucilage: kinetics,thermodynamics, and equilibrium evaluation

Abstract

Adsorption of dyes onto natural materials like polysaccharides is considered a green chemistry approach for remediation of wastewater. In this work, the polysaccharide isolated from the corm of Colocasia esculenta (L.) Schott or taro tuber (CEM) was utilized for removing methylene blue (MB) from aqueous solution by batch adsorption method. The CEM adsorbent was characterized by FTIR spectroscopy, Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM). The solution pH and adsorbent dose have been found to have a significant positive correlation with the adsorptive removal efficiency of CEM for MB dye. The removal efficiency of CEM was found to be 72.35% under the optimum conditions; 20?mg/L initial concentration of dye, 120?mg of adsorbent dose, solution pH 8.5, 311.2?K temperature and 80?min contact time. The adsorption of MB onto CEM followed best the Freundlich isotherm and pseudo-second-order kinetics. The adsorption was thermodynamically favorable and was endothermic in nature. The desorption/adsorption data justifiably indicated the reuse capability of CEM adsorbent for MB adsorption. Hence, CEM may be regarded as an eco-friendly and cost-effective natural adsorbent for MB dye removal from aqueous solution.     

Cationized starch-based material as a new ion-exchanger adsorbent for the removal of C.I. Acid Blue 25 from aqueous solutions

This article describes the use of a cationized starch-based material as new ion-exchanger adsorbent for the removal of C.I. Acid Blue 25 (AB 25) from aqueous solutions. Batch adsorption studies concerning the effects of contact time, pH and temperature are presented and discussed. Adsorption experimental data showed that: (i) the process was uniform and rapid: adsorption of dye reached equilibrium in 50 min in the wide pH range of dye solutions; (ii) adsorption kinetics followed the pseudo-second order model; (iii) the Langmuir model yielded a much better fit than the Freundlich model for the dye concentration range under study; (iv) this adsorbent exhibited interesting adsorption capacities: on the basis of the Langmuir analysis, the maximum adsorption capacity was determined to be 322 mg of dye per gram of material at 25 degrees C; (v) the adsorption capacity decreased with increasing temperature; and (vi) the negative value of free energy change indicated the spontaneous nature of adsorption.     

Experimental and kinetic studies on methylene blue adsorption by coir pith carbon

Varying the parameters such as agitation time, dye concentration, adsorbent dose, pH and temperature carried out the potential feasibility of thermally activated coir pith carbon prepared from coconut husk for removal of methylene blue. Greater percentage of dye was removed with decrease in the initial concentration of dye and increase in amount of adsorbent used. Kinetic study showed that the adsorption of dye on coir pith carbon was a gradual process. Lagergren first-order, second-order, intra particle diffusion model and Bangham were used to fit the experimental data. Equilibrium isotherms were analysed by Langmuir, Freundlich, Dubnin-Radushkevich, and Tempkin isotherm. The adsorption capacity was found to be 5.87 mg/g by Langmuir isotherm for the particle size 250-500 microm. The equilibrium time was found to be 30 and 60 min for 10 and 20 mg/L and 100 min for 30, 40 mg/L dye concentrations, respectively. A maximum removal of 97% was obtained at natural pH 6.9 for an adsorbent dose of 100 mg/50 mL and 100% removal was obtained for an adsorbent dose of 600 mg/50 mL of 10 mg/L dye concentration. The pH effect and desorption studies suggest that chemisorption might be the major mode of the adsorption process. The change in entropy (DeltaS0) and heat of adsorption (DeltaH0) of coir pith carbon was estimated as 117.20 J/mol/K and 30.88 kJ/mol, respectively. The high negative value of change in Gibbs free energy indicates the feasible and spontaneous adsorption of methylene blue on coir pith carbon.     

Blast Furnace Slag of a Ferrosilicon Firm in Aswan Governorate,Upper Egypt,as an Adsorbent for the Removal of Merocyanine Dye from Its Aqueous Solution

The adsorption potential of the blast furnace slag of a ferrosilicon firm in Aswan Governorate, Egypt, to decolorize aqueous solutions of 3‐methyl‐1‐phenylpyrazol‐5‐one 4[2] merocyanine dye ( 1 ) was investigated at room temperature. The influence of the solution pH, the quantity of adsorbent, the initial concentration of 1 , and the applied contact time were studied with the batch technique. The maximum percentage of removal of 1 was observed at pH 4. The adsorption data were better fitted by the Freundlich than by the Langmuir adsorption isotherm model, confirming the formation of monolayers of 1 on the adsorbent surface. Kinetic rate constants and the transient behavior at different initial concentrations of 1 were determined with both the Lagergren pseudo‐first‐order and the Ho and McKay pseudo‐second‐order kinetic models. The calculated kinetic parameters revealed that the adsorption of 1 on blast furnace slag followed a second‐order chemisorption process.     

Adsorption of Methylene Blue Dye on Pure and Carbonized Water Weeds

The influence of process variables in batch adsorption has been used to assess the removal of methylene blue dye from aqueous solution using pure and carbonized biomasses of water hyacinth and water spinach. Dried leaves of the water weeds were carbonized at temperature up to 750°C. The optimum removal of dye was achieved at pH 10, 30°C, and 55 min at a dye concentration of 10 mg/L. In an attempt to describe the adsorption process, the equilibrium isotherm for each adsorbent was determined using Langmuir and Freundlich adsorption isotherm models. Maximum adsorption capacities based on the Langmuir model for pure and carbonized water hyacinth were (mg/g) 7.05 and 2.07, respectively, whereas those of pure and carbonized water spinach were 1.25 and 5.32, respectively. It was observed that the equilibrium data were well fit by both the Freundlich and Langmuir isotherms as R ² > .97. This study demonstrates that the two waterweeds are effective, environmentally friendly, and inexpensive biomaterials for the removal of color from industrial effluents.     

Biosorption of an Azo Dye by <Emphasis Type="Italic">Aspergillus niger</Emphasis> and <Emphasis Type="Italic">Trichoderma</Emphasis> sp. Fungal Biomasses

Biosorption is an eco-friendly and cost-effective method for treating the dye house effluents. Aspergillus niger and Trichoderma sp. were cultivated in bulk and biomasses used as biosorbents for the biosorption of an azo dye Orange G. Batch biosorption studies were performed for the removal of Orange G from aqueous solutions by varying the parameters like initial aqueous phase pH, biomass dosage, and initial dye concentration. It was found that the maximum biosorption was occurred at pH 2. Experimental data were analyzed by model equations such as Langmuir and Freundlich isotherms, and it was found that both the isotherm models best fitted the adsorption data. The monolayer saturation capacity was 0.48 mg/g for Aspergillus niger and 0.45 mg/g for Trichoderma sp. biomasses. The biosorption kinetic data were tested with pseudo first-order and pseudo second-order rate equations, and it was found that the pseudo second-order model fitted the data well for both the biomasses. The rate constant for the pseudo second-order model was found to be 10–0.8 (g/mg min⁻¹) for Aspergillus niger and 8–0.4 (g/mg min⁻¹) for Trichoderma sp. by varying the initial dye concentrations from 5 to 25 mg/l. It was found that the biomass obtained from Aspergillus niger was a better biosorbent for the biosorption of Orange G dye when compared to Trichoderma sp.     

Adsorption kinetics of a basic dye from aqueous solutions onto apricot stone activated carbon

The preparation of activated carbon from apricot stone with H₂SO₄ activation and its ability to remove a basic dye, astrazon yellow 7GL, from aqueous solutions were reported in this study. The adsorbent was characterized by FTIR, BET and SEM, respectively. The effects of various experimental parameters, such as initial dye concentration, pH, adsorbent dosage and temperature were investigated in a batch-adsorption technique. The optimum conditions for removal of the basic dye were found to be pH 10, 6 g/l of adsorbent dosage and equilibrium time of 35 min, respectively. A comparison of three kinetic models, the pseudo first-order, second-order and diffusion controlled kinetic models, on the basic dye-adsorbent system showed that the removal rate was heavily dependent on diffusion controlled kinetic models. The adsorption isotherm data were fitted well to Langmuir and Freundlich isotherms. The adsorption capacity was calculated as 221.23 mg/g at 50 °C. Thermodynamics parameters were also evaluated. The values of enthalpy and entropy were 49.87 kJ/mol and 31.93 J/mol K, respectively, indicating that this process was spontaneous and endothermic. The experimental studies were indicated that ASC had the potential to act as an alternative adsorbent to remove the basic dye from aqueous solutions.     

Adsorption of lead(II) from aqueous solution onto Hydrilla verticillata

The adsorption of Pb(II) onto Hydrilla verticillata was examined in aqueous solution with parameters of pH, adsorbent dosage, contact time and temperature. The linear Langmuir and Freundlich models were applied to describe equilibrium isotherms, and both models fitted well. The monolayer adsorption capacity of Pb(II) was found as 104.2 mg/g at pH 4 and 25°C. Dubinin–Radushkevich (D–R) isotherm model was also applied to the equilibrium data. The mean free energy of adsorption (15.81 kJ/mol) indicated that the adsorption of Pb(II) onto H. verticillata may be carried out via chemical ion-exchange mechanism. Thermodynamic parameters, free energy (ΔG ⁰), enthalpy (ΔH ⁰) and entropy (ΔS ⁰) of adsorption were also calculated. These parameters showed that the adsorption of Pb(II) onto H. verticillata was a feasible, spontaneous and exothermic process in nature. The influence of Cd²⁺, Cu²⁺ and Ni²⁺ on adsorption of Pb²⁺ onto H. verticillata was studied, too. In the investigated range of operating conditions, it was found that the existence of Cd ²⁺, Cu ²⁺ and Ni ²⁺ had no impact on the adsorption of Pb²⁺.     

Chemical modification of chitosan by tetraethylenepentamine and adsorption study for anionic dye removal

To utilize the contribution of introduced amino groups to the adsorption of an anionic dye (eosin Y), a batch adsorption system was applied to study the adsorption of eosin Y from aqueous solution by tetraethylenepentamine (TEPA) modified chitosan (TEPA–CS). Experiments were carried out as a function of particle size, initial pH, agitation rate, adsorbent dosage, agitation period, temperature and initial concentration of eosin Y. The Langmuir and Freundlich models were used to fit the adsorption isotherms. From the values of correlation coefficients (R²), it was observed that the experimental data fit very well to the Langmuir model, giving a maximum sorption capacity of 292.4 mg/g at 298 K. Kinetic studies showed that the kinetic data were well described by the pseudo-second-order kinetic model. The thermodynamic study revealed negative value of enthalpy change (ΔH°) and free energy change (ΔG°), indicating spontaneous and endothermic nature of the adsorption of eosin Y on to TEPA–CS.     

Microwave treated Salvadora oleoides as an eco-friendly biosorbent for the removal of toxic methyl violet dye from aqueous solution—A green approach

In the present study, microwave treated Salvadora oleoides (MW-SO) has been investigated as a potential biosorbent for the removal of toxic methyl violet dye. A batch adsorption method was experimented for biosorptive removal of toxic methyl violet dye from the aqueous solution. The effect of various operating variables, viz., adsorbent dosage, pH, contact time and temperature on the removal of the dye was studied and it was found that nearly 99% removal of the dye was possible under optimum conditions. Kinetic study revealed that a pseudo-second-order mechanism was predominant and the overall process of the dye adsorption involved more than one step. Hence, in order to investigate the rate determining step, intra-particle diffusion model was applied. Adsorption equilibrium study was made by analyzing Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) adsorption isotherm models and the biosorption data was found to be best represented by the Langmuir model. The biosorption efficiency of MW-SO was also compared with unmodified material, Salvadora oleoides (SO). It was found that the sorption capacity (q_max) increased from 58.5 mg/g to 219.7 mg/g on MW treatment. Determination of thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) confirmed the spontaneous, endothermic and feasible nature of the adsorption process. The preparation of MW-SO did not require any additional chemical treatment and a high percentage removal of methyl violet dye was obtained in much lesser time. Thus, it is in agreement with the principles of green chemistry. The results of the present research work suggest that MW-SO can be used as an environmentally friendly and economical alternative biosorbent for the removal of methyl violet dye from aqueous solutions.     

Equilibrium and a two-stage batch adsorber design for reactive or disperse dye removal to minimize adsorbent amount

The adsorption of a reactive dye (Reactive Yellow K-4G) and a disperse dye (Disperse yellow brown S-2RFL) onto polyepicholorohydrin-dimethylamine (EPIDMA) cationic polymer modified bentonite (EPIDMA-bentonite) in batch adsorber was studied, respectively. Two equilibrium models, the Langmuir and Freundlich models were selected to follow the adsorption process. It was shown that the equilibrium experimental data for reactive dye adsorption could be well described by the Freundlich model, but for disperse dye the Langmuir model could be better. Based on the well correlated adsorption isotherm, an adsorption process design model was developed for the design of a two-stage batch adsorber to predict the minimum amount of adsorbent to achieve a specified percentage of dye removal at a given volume of wastewater effluents. The adsorption process design analysis indicated that compared with the single-stage batch adsorption, the two-stage process could significantly save adsorbent to meet the higher demands of dye removal efficiency.     

Biosorption of Lead from Industrial Wastewater Using Chrysophyllum albidum Seed Shell

The shell of the seed of Chrysophyllum albidum carbon was used to adsorb lead (Pb) from aqueous solution, the sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration, and particle size on adsorption were also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The first-order rate equation by Lagergren was tested on the kinetic data and the adsorption process followed first-order rate kinetics. Isotherm data were analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms; the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 72.1 mg Pb (II) g^{- 1} at initial pH of 5.0 at 30°C for the particle size of 1.00 to 1.25 mm with the use of 2.0 g/100 ml adsorbent mass. The structural features of the adsorbent were characterized by Fourier transform infrared (FTIR) spectrometry; the presence of hydroxyl, carbonyl, amide, and phosphate groups confirms the potential mechanism adsorption of the adsorbent. This readily available adsorbent is efficient in the uptake of Pb (II) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater.     

Use of Phanerochaete chrysosporium biomass for the removal of textile dyes from a synthetic effluent

Summary The use of Phanerochaete chrysosporium biomass for the removal of Reactofix Golden Yellow from aqueous solution and eight textile dyes (four azo and four anthraquinone) from a synthetic effluent (0.6 g/l) at different pH, temperature and biomass concentrations was studied. Adsorption was maximum at pH 2.0 and 40 °C using 2.45 g mycelial biomass. The rate constant of adsorption was 1.95×10⁻¹/min for Reactofix Golden Yellow and 1.64×10⁻¹/min for synthetic effluent. In both cases, the equilibrium data fitted well in the Langmuir but not the Freundlich model of adsorption, and the adsorption was biphasic. Adsorption decreased the COD of Reactofix Golden Yellow and synthetic effluent by 54 and 57%, respectively. Desorption (80–84%) of dyes from P. chrysosporium mycelial surface occurred as the pH increased from 2 to 10.     

Utilization of modified silk cotton hull waste as an adsorbent for the removal of textile dye (reactive blue MR) from aqueous solution

Carbon prepared from silk cotton hull was used to remove a textile dye (reactive blue MR) from aqueous solution by an adsorption technique under varying conditions of agitation time, dye concentration, adsorbent dose and pH. Adsorption depended on solution pH, dye concentration, carbon concentration and contact time. Equilibrium was attained with in 60 min. Adsorption followed both Langmuir and Freundlich isotherm models. The adsorption capacity was found to be 12.9 mg/g at an initial pH of 2+/-0.2 for the particle size of 125-250 microm at room temperature (30+/-2 degrees C).     

Sorption of Acid Blue 9 Using Hydrilla verticillata Biomass—Optimization,Equilibrium, and Kinetics Studies

In the present study, the parameters, temperature, adsorbent dose, contact time, adsorbent size, and agitation speed were optimized for Acid Blue 9 removal from aqueous medium by Hydrilla verticillata biomass using response surface methodology (RSM). The optimum conditions for maximum removal of Acid Blue 9 from an aqueous solution of 100 mg/L were as follows: temperature 30.63°C, adsorbent dose 2.88 g/L, contact time 180 min, adsorbent size 120 mesh (0.124 mm), and agitation speed 237.39 rpm. At these optimized conditions, batch adsorption experiments were conducted to study the effect of pH and initial dye concentration for the removal of Acid Blue 9 dye. The optimum initial pH and initial dye concentration values for Acid Blue 9 removal were found to be 3.0 and 100 mg/L, respectively. Kinetic and equilibrium studies were carried out for the experimental results. From the kinetic studies it was found that pseudo-second-order kinetics suits the system well. From the equilibrium studies, the Freundlich isotherm fits the data well.