Model fuel desulfurization and denitrogenation using copper and cerium modified mesoporous material (MSU-S) through adsorption process

The application of MSU-S, CeO₂-MSU-S, and Cu₂O-MSU-S in desulfurization and denitrogenation of model fuel containing benzothiophene (BT), dibenzothiophene (DBT), quinoline and carbazole were studied in batch and continuous process. The copper-modified MSU-S showed the highest capacity to adsorb sulfur and nitrogen compounds compared to other adsorbents. The adsorption selectivity of all adsorbents for nitrogen was slightly higher than for sulfur, indicating the selective adsorption of nitrogen over sulfur. The Langmuir model represented better equilibrium data fitting than Freundlich model for carbazole, DBT, and BT adsorption on MSU-S, CeO₂-MSU-S, and Cu₂O-MSU-S. It was found that quinoline adsorption data on MSU-S, CeO₂-MSU-S, and Cu₂O-MSU-S can be presented by Freundlich model very well. The kinetics of adsorption followed the pseudo-second-order model for all species over each adsorbent. According to the breakthrough curve order, the adsorptive selectivity for the adsorbates increased in the order of DBT < BT < carbazole < quinoline for MSU-S and CeO₂-MSU-S, and BT < DBT < carbazole < quinoline for Cu₂O-MSU-S.     

Determination of kinetic and equilibrium parameters of the batch adsorption of Ni(II) from aqueous solutions by Na-mordenite

The potential to remove nickel(II) ions from aqueous solutions using Na-mordenite, a common zeolite mineral, was thoroughly investigated. The effects of relevant parameters solution pH, adsorbent dose, ionic strength, and temperature on nickel(II) adsorption capacity were examined. The sorption data followed the Langmuir, Freundlich, Langmuir-Freundlich and Dubinin-Radushkevich (D-R) isotherms. The maximum sorption capacity was found to be 5.324 mg/g at pH 6, initial concentration of 40 mg/L and temperature of 20 degrees C. Thermodynamic parameters, viz. changes in standard free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) have also been evaluated and the results show that the sorption process was spontaneous and endothermic in nature. Dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion were calculated. The activation energy (E(a)) was found to be 12.465 kJ/mol in the present study, indicating a chemical sorption process involving weak interactions between sorbent and sorbate. The sorption capacity increased with the increase of solution pH and the decrease of ionic strength and adsorbent dose. The nickel(II) ions sorption by the Na-mordenite is not completely attributable to ion exchange. Compared to the other adsorbents, the nickel(II) ions show a lower affinity towards the clay mineral adsorbents.     

Adsorption removal of cadmium and copper from aqueous solution by areca: a food waste

Areca waste (AW) has been investigated as metal biosorbent for cadmium and copper from aqueous solution for its availability as food waste and also for its cellulosic matrix rich of potential metal binding active sites. The effect of various parameters on adsorption process such as contact time, solution pH, amount of AW and initial concentration of metal ions was studied at room temperature to optimize the conditions for maximum adsorption. Maximum metal sorption was found to occur at pH 5.6. Adsorption process revealed that the initial uptake was rapid and equilibrium was established about in 1h for cadmium and copper. The equilibrium sorption data for single metal systems at pH 5.6 were described by the Langmuir, Freundlich and D-R isotherm models. The adsorption isotherm studies clearly indicated that the adsorptive behaviour of metal ions on AW not only the Langmuir assumptions but also the Freundlich and the D-R assumptions. The highest value of Langmuir maximum uptake, (b), was found for cadmium (1.12 mg/g) and copper (2.84 mg/g). Similar Freundlich empirical constants, K, were obtained for cadmium (1.086) and copper (1.119). Ion-exchange and surface adsorption might be involved in the adsorption process of cadmium and copper. Desorption studies revealed that cadmium and copper can be easily removed from AW by altering the pH values of the solution using HNO(3), indicating that AW are a promising adsorbent for wastewater treatment.     

Removal of phenol and 4-chlorophenol by surfactant-modified natural zeolite

In this study the adsorption characteristics of phenol and 4-chlorophenol by surfactant-modified zeolite was investigated. Batch studies were performed to evaluate the effects of various experimental parameters such as contact time, adsorbent dose, initial concentration, and temperature on the removal of phenol and 4-chlorophenol. The sorption kinetics was tested for intraparticle diffusion, Elovich, and pseudo-second order reaction and rate constants of kinetic models were calculated. Equilibrium isotherms for the adsorption of phenol were analyzed by Freundlich, Langmuir, and Tempkin isotherm models. Freundlich isotherm was found to best represent the data for phenol and 4-chlorophenol adsorption.     

Solid-state conversion of fly ash to effective adsorbents for Cu removal from wastewater

Solid-state conversion of fly ash to an amorphous aluminosilicate adsorbent (geopolymer) has been investigated under different conditions and the synthesised material has been tested for Cu2+ removal from aqueous solution. It has been found that higher reaction temperature and Na:FA ratio will make the adsorbents achieving higher removal efficiency. The adsorbent loading and Cu2+ initial concentration will also affect the removal efficiency while the adsorption capacity exhibits similarly at 30-40 degrees C. The adsorption capacity of the synthesised adsorbent shows much higher value than fly ash and natural zeolite. The capacity is 0.1, 3.5 and 92 mg/g, for fly ash, natural zeolite, and FA derived adsorbent, respectively. The kinetic studies indicate that the adsorption can be fitted by the second-order kinetic model. Langmuir and Freundlich isotherms also can fit to the adsorption isotherm.     

The effect of some operating variables on the adsorption of lead and cadmium ions on kaolinite clay

Modification of kaolinite clay mineral with orthophosphate (p-modified sample) enhanced adsorption of Pb and Cd ions from aqueous solutions of the metal ions. Increasing pH of solutions of metal ions, increasing adsorbent dose and increasing concentration of metal ion, increased the adsorption of metal ions. Adsorption of both metal ions simultaneously on both unmodified and p-modified samples indicates that adsorption of one metal ion is suppressed to some degree by the other. The presence of electrolyte and their increasing concentration reduced the adsorption capacities of both unmodified and p-modified samples for the metal ions. Ca-electrolytes had more negative effect on the adsorption capacities of the adsorbents than Na-electrolytes. Ca-electrolytes reduced adsorption capacities of the adsorbents for Pb and Cd ions. From Langmuir plots it was observed that these electrolytes increased the binding energy constant of the metal ions unto the adsorbents especially on the p-modified samples. The rate of adsorption of Pb and Cd ions on p-modified adsorbent were increased and equilibrium of metal ion solution were more quickly reached (8min for Pb ions and 12min for Cd ions) with p-modified adsorbent as against 20min for adsorption of both metal ions on unmodified adsorbent when 200mg/L of metal ion solutions were used during the kinetic studies. When adsorption data were fitted against Langmuir, Freundlich, Toth and Langmuir-Freundlich isotherms, satisfactory fits were found with the Freundlich isotherm. However, at low concentration of metal ions, data also showed satisfactory fits to Langmuir isotherm.     

Sorption of lead from aqueous solution by chemically modified carbon adsorbents

An indigenously prepared, steam activated and chemically modified carbon from husk and pods of Moringa oleifera (M. oleifera), an agricultural waste, was comparatively examined as an adsorbent for the removal of lead from aqueous solutions. Studies were conducted as a function of contact time, initial metal concentration, dose of adsorbent, agitation speed, particle size and pH. Maximum uptake capacities were found to be, 98.89, 96.58, 91.8, 88.63, 79.43% for cetyltrimethyl ammonium bromide (CTAB), phosphoric, sulfuric, hydrochloric acid treated and untreated carbon adsorbents, respectively. Bangham, pseudo-first- and second-order, intra-particle diffusion equations were implemented to express the sorption mechanism by utilized adsorbents. Adsorption rate of lead ions was found to be considerably faster for chemically modified adsorbents than unmodified. The results of adsorption were fitted to both the Langmuir and Freundlich models. Satisfactory agreement between the metal uptake capacities by the adsorbents at different time intervals was expressed by the correlation coefficient (R(2)). The Langmuir model represented the sorption process better than the Freundlich one, with R(2) values ranging from 0.994 to 0.998.     

Adsorptive desulfurization by zinc-impregnated activated carbon: characterization,kinetics, isotherms,and thermodynamic modeling

Sulfur oxides emission because of burning of liquid fuels has become a global environmental challenge. Refineries need to meet ever-stringent liquid fuel standards by using newer desulfurization methods. Present paper reports the results of the studies on adsorptive removal of sulfur compounds from model fuel by zinc-impregnated granular activated carbon (GAC). Zn-loaded adsorbent (Zn-GAC) prepared by wet impregnation method was characterized for its textural, morphological, and structural characteristics by different techniques like liquid nitrogen adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The adsorbent was further used for the removal of dibenzothiophene (DBT), a sulfur compound, from iso-octane. Equilibrium adsorption was obtained in 6 h. The equilibrium adsorption data were well represented by the Redlich–Peterson isotherm. Thermodynamic parameters were calculated by applying the van’t Hoff and Clausius–Clapeyron equations. Values of change in enthalpy and entropy were found to be 4.89 kJ/mol and 30 J/mol K, respectively. Isosteric heat of adsorption was correlated with surface coverage and heterogeneous nature of the Zn-GAC.     

Enhanced desorption and biodegradation of phenanthrene in soil-water systems with the presence of anionic-nonionic mixed surfactants

The present work investigates the adsorptive interactions of Cs ions with natural magnetite and synthesized iron ferrite in aqueous medium. The applied adsorbents were characterized by FTIR and DTA/TGA analyses. Batch adsorption studies were performed to evaluate the influences of various experimental parameters like initial pH, contact time and initial concentration on the removal of Cs. The adsorption is strongly dependent on pH of the medium where the removal efficiency increases as the pH turns to alkaline range. The process was very fast initially and maximum adsorption was attained within 60 min of contact. The adsorption process follows a pseudo-second order kinetics with rate constant amounted to 76.83 x 10(4) and 18.75 x 10(4)g mg(-1)h(-1) with ferrite and magnetite. The presence of interfering cations seriously decreases the extent of Cs adsorption. The equilibrium data of Cs adsorption on both adsorbents were analyzed using the Freundlich, Langmuir, Temkin, Dubinin-Radushkevich and Redlich-Peterson isotherm models. The different isotherms constants were determined from the linearzed form of their equations and used to characterize Cs distribution on adsorbent surfaces and provide adopted information about the affinity of the adsorbents towards Cs ions. The values of Langmuir separation factor indicate a favorable Cs adsorption. The apparent free energies from the Dubinin-Radushkevich are 32.29 and 27.51 kJ mol(-1) for Cs adsorption onto iron ferrite and magnetite, respectively.     

Evaluation of commercial adsorbents and their application for desulfurization of model fuel

The removal of dibenzothiophene from model fuel was carried out by adsorption on commercially available adsorbents including an activated carbon, aluminum oxide, 13X and Y zeolite. Activated carbon was SOLCARB^TM C3 which was grinded from its original particle size 1.0–2.0 mm to the 0.40–0.80 mm, while aluminum oxide Selexsorb CDX, 13X zeolite MSE 13X and Y zeolite HSZ-320NAA were used in their as delivered particle size ranges of 2.7–3.0, 1.6, and 300–600 nm, respectively. Adsorption experiments were carried out in batch mode at 24.5 ± 0.7°C using model fuel comprising cyclo-hexane, n-heptane, n-octane and dibenzothiophene in the concentration range of 0.48–42.91 mg/g. The experimental data was used to compare applied adsorbents and to carry out equilibrium characterization and kinetic analysis of the adsorption process. The evaluation of the tested adsorbents showed that the best adsorptive performance was achieved by the Y zeolite. The analysis of the adsorption equilibrium data and the kinetic analysis showed that of the applied models the best fits to the experimental data were achieved by the Sips and Ritchie models, respectively.     

Removal of organic pollutants from produced water by batch adsorption treatment

This paper studied the adsorption of chemical oxygen demand (COD), oil and turbidity of the produced water (PW) which accompanies the production and reconnaissance of oil after treating utilizing powdered activated carbon (PAC), clinoptilolite natural zeolite (CNZ) and synthetic zeolite type X (XSZ). Moreover, the paper deals with the comparison of pollutant removal over different adsorbents. Adsorption was executed in a batch adsorption system. The effects of adsorbent dosage, time, pH, oil concentration and temperature were studied in order to find the best operating conditions. The adsorption isotherm models of Langmuir, Freundlich and Temkin were investigated. Using pseudo-first-order and pseudo-second-order kinetic models, the kinetics of oil sorption and the shift in COD content on PAC and CNZ were investigated. At a PAC adsorbent dose of 0.25 g/100 mL, maximum oil removal efficiencies (99.57, 95.87 and 99.84 percent), COD and total petroleum hydrocarbon (TPH) were identified. Moreover, when zeolite X was used at a concentration of 0.25 g/100 mL, the highest turbidity removal efficiency (99.97%) was achieved. It is not dissimilar to what you would get with PAC (99.65 percent). In comparison with zeolites, the findings showed that adsorption over PAC is the most powerful method for removing organic contaminants from PW. In addition, recycling of the consumed adsorbents was carried out in this study to see whether the adsorbents could be reused. Chemical and thermal treatment will effectively regenerate and reuse powdered activated carbon and zeolites that have been eaten.

Graphic abstract

     

Study of the behaviour of thorium adsorption on PAN/zeolite composite adsorbent

The adsorption behaviour of thorium from aqueous solutions by a composite adsorbent has been investigated by a batch technique. The thorium adsorption on composite adsorbent was studied as a function of initial concentration, pH, shaking time and temperature. The sorption of thorium at the determined optimum conditions follows Langmuir, Freundlich and D-R type isotherms. Langmuir constants Q=0.04 mmol g(-1) and b=64.94 L mol(-1) and of D-R parameter Xm = 0.04, beta=0.79 and of sorption energy E=0.80 and Freundlich constants 1/n=3.12 and cm = 0.012 mmol g(-1) were evaluated. Thermodynamic parameters such as DeltaH and DeltaS were found to be 37.32 kJ mol(-1) and 206.17 J mol(-1)K(-1), respectively.     

Adsorptive removal of methylene blue by tea waste

The potentiality of tea waste for the adsorptive removal of methylene blue, a cationic dye, from aqueous solution was studied. Batch kinetics and isotherm studies were carried out under varying experimental conditions of contact time, initial methylene blue concentration, adsorbent dosage and pH. The nature of the possible adsorbent and methylene blue interactions was examined by the FTIR technique. The pH(pzc) of the adsorbent was estimated by titration method and a value of 4.3+/-0.2 was obtained. An adsorption-desorption study was carried out resulting the mechanism of adsorption was reversible and ion-exchange. Adsorption equilibrium of tea waste reached within 5h for methylene blue concentrations of 20-50mg/L. The sorption was analyzed using pseudo-first-order and pseudo-second order kinetic models and the sorption kinetics was found to follow a pseudo-second order kinetic model. The extent of the dye removal increased with increasing initial dye concentration. The equilibrium data in aqueous solutions were well represented by the Langmuir isotherm model. The adsorption capacity of methylene blue onto tea waste was found to be as high as 85.16mg/g, which is several folds higher than the adsorption capacity of a number of recently studied in the literature potential adsorbents. Tea waste appears as a very prospective adsorbent for the removal of methylene blue from aqueous solution.     

Adsorption isotherms and kinetics for dibenzothiophene on activated carbon and carbon nanotube doped with nickel oxide nanoparticles

Activated carbon (AC) and multiwall carbon nanotubes (CNT) doped with 1, 5 and 10% Ni in the form of nickel oxide nanoparticles were prepared using the wetness impregnation method. These percentages were denoted by the endings NI1, NI5 and NI10 in the notations ACNI1, ACNI5, ACNI10 and CNTNI1, CNTNI5, CNTNIL10, respectively. The physicochemical properties for these adsorbents were characterized using N ₂ adsorption–desorption surface area analyzer, thermal gravimetric analysis (TGA), scanning electron microscopy, energy-dispersive X-ray spectroscopy, field-emission transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectrometre. Adsorption isotherms were obtained and desulphurization kinetics were carried out on solutions of dibenzothiophene (DBT) and thiophene in a model fuel. The efficiencies of DBT and thiophene removal were reported. The adsorption isotherms fitted the Langmuir and Freundlich models. The highest adsorption capacity for DBT was 74± 5 mg g^?1 on ACNI5; the maximum adsorption capacities of the other adsorbents followed the trend ACNI1 > ACNI10 > AC > CNTNI5 > CNTNI1 > CNTNI10 > CNT. The adsorption rates for DBT and thiophene followed pseudo-second-order kinetics. The selective removal by these adsorbents of DBT relative to thiophene and naphthalene was evaluated. The adsorbents’ reusability and the effect of the percentage of aromatic compounds on their adsorption capacity were also reported.     

活性炭负载Fe(Ⅲ)氧化物去除水中的磷酸根

利用活性炭负载铁氧化物制备了复合吸附剂,并用于水中磷酸根的去除.采用BET,SEM及XRD等手段对复合吸附剂的物理化学特性进行了表征,用静态吸附实验方法比较研究了复合吸附剂和活性炭从水溶液中吸附磷酸根的性质.结果表明:复合吸附剂具有快的吸附速度和高的吸附容量,其吸附磷酸根的性质受溶液pH值、铁含量及阴离子浓度的影响.在pH=3.0时,复合吸附剂对磷酸根的吸附容量为98.39 mg/g,而活性炭为78.90 mg/g.相比之下,Freundlich模型比Langmuir模型能更好地描述复合吸附剂和活性炭对磷酸根的吸附过程;而Lagergren二级方程却能很好地描述复合吸附剂对磷酸根的吸附动力学.水合氧化铁/活性炭复合吸附剂吸附磷酸根为吸热过程.     

Studies on the removal of Pb(II) from wastewater by activated carbon developed from Tamarind wood activated with sulphuric acid

The low-cost activated carbon were prepared from Tamarind wood material by chemical activation with sulphuric acid for the adsorption of Pb(II) from dilute aqueous solution. The activated carbon developed shows substantial capacity to adsorb Pb(II) from dilute aqueous solutions. The parameters studied include physical and chemical properties of adsorbent, pH, adsorbent dose, contact time and initial concentrations. The kinetic data were best fitted to the Lagergren pseudo-first-order and pseudo-second order models. The isotherm equilibrium data were well fitted by the Langmuir and Freundlich models. The maximum removal of lead(II) was obtained 97.95% (experimental) and 134.22 mg/g (from Langmuir isotherm model) at initial concentration 40 mg/l, adsorbent dose 3g/l and pH 6.5. This high uptake showed Tamarind wood activated carbon as among the best adsorbents for Pb(II).     

Sorption of copper(II) ion from aqueous solution by Tectona grandis l.f. (teak leaves powder)

Studies on a batch sorption system using Tectona grandis l.f. as adsorbent was investigated to remove copper(II) from aqueous solutions. The adsorption experiments were performed under various conditions such as different initial concentrations, pH, adsorbent dosage and adsorbent particle size. The data showed that 0.1 g of Tectona grandis l.f. was found to remove 71.66% of 20 mg/L copper(II) from 30 mL aqueous solution in 180 min. The experimental equilibrium data were adjusted by the adsorption isotherms from Langmuir and Freundlich models and their equilibrium parameters were determined. The best-adjusted model to the experimental equilibrium data for Tectona grandis l.f. was the Langmuir model. Using the Langmuir model equation, the monolayer sorption capacity of Tectona grandis l.f. was evaluated and found to be 95.40 mg/g. The optimum pH value was found to be 5.5. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. The dynamic data fitted the pseudo-second-order kinetic model.     

Synthesis of pure NaA zeolites from coal fly ashes for ammonium removal from aqueous solutions

The pure NaA zeolites used as adsorbents for ammonium removal were successfully synthesized from coal fly ash by means of alkaline fusion followed by hydrothermal treatment. The experiment samples were characterized in terms of X-ray diffraction, X-ray fluorescence, Scanning electron microscopy, Fourier transform infrared spectroscopy, and Automated specific surface area and pore size analyzer. The results showed that the NaOH solution’s concentration, reaction temperature, and reaction time had significant effects on the species of the zeolite phases. Well-ordered cubic NaA zeolite with Brunauer–Emmett–Teller specific surface areas of 41.6 m²/g was prepared in 3 M NaOH solution at 353 K for 3 h. The adsorption behavior of NH₄ ⁺ from aqueous solution onto NaA zeolites was investigated at different initial concentrations, pH values, and contact times. The adsorbent equilibrium could be reached within 60 min, and the maximum removal efficiency of NH₄ ⁺ was achieved at pH 7.0. The Langmuir and Freundlich adsorption models were also applied to describe the equilibrium isotherms. The obtained results show that the experimental data have a better (R ² = 0.99) fit to Freundlich model and the adsorption of NH₄ ⁺ ions using synthesized NaA zeolite is favorable.     

Removal of boron from aqueous solution by using neutralized red mud

The adsorptive removal of boron from aqueous solution by using the neutralized red mud was studied in batch equilibration technique. The effects of pH, adsorbent dosage, initial boron concentration and contact time on the adsorption were investigated. The experiments demonstrated that boron removal was of a little fluctuation in pH range of 2-7 and it takes 20 min to attain equilibrium. The adsorption data was analyzed using the Langmuir and the Freundlich isotherm models and it was found that the Freundlich isotherm model represented the measured sorption data well.     

Sorption of indigo carmine by a Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge

Indigo carmine removal from aqueous solution has been evaluated using Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge treated with HCl (CM). The adsorbents were characterized by scanning electron microscopy, BET surface area and X-ray diffraction. Sorption kinetics and isotherms were determined and the adsorption behaviors analyzed. Kinetic pseudo-second order and Langmuir–Freundlich models were successfully applied to the experimental results obtained with the Fe-zeolitic material, while kinetic first order and Langmuir–Freundlich models were applied to the results from the carbonaceous materials. This indicates mechanisms of chemisorption and physic sorption, respectively, on the heterogeneous materials. The results indicate that the carbonaceous material from the pyrolysis of sewage sludge (sorption capacity 92.83 mg/g) is a better adsorbent of indigo carmine than the zeolitic material (sorption capacity 32.83 mg/g).