The Selective Removal off Nitrogenous-Type Compounds from Fuels by Using Zeolites

Abstract

Several zeolites were tested for the selective removal of nitrogenous compounds from an organic solution. A model compound study showed that the extent of sorption from a complex mixture is a function of the nature of the nitrogenous compounds. A correlation between the extent of sorption and the size of a compound suggests that diffusion is the controlling parameter. A capacity of 10 wt% was obtained for the model compound study. The zeolites were also tested for the removal of nitrogenous compounds from a coker naphtha and from a hydroprocessed naphtha. The low capacities relative to the model compound study of ?1 wt% and ?3 wt% obtained for the coker and the hydroprocessed naphthas, respectively, suggest the sorption of nonnitrogenous compounds.     

Physico‐Chemical Processes for Landfill Leachate Treatment: Experiments and Mathematical Models

Abstract

In this study, the adsorption of synthetic landfill leachate onto four kinds of activated carbon has been investigated. From the equilibrium and kinetics experiments, it was observed that coal based PAC presented the highest organic pollutants removal efficiency (54%), followed by coal based GAC (50%), wood based GAC (33%) and wood based PAC (14%). The adsorption equilibrium of PAC and GAC was successfully predicted by Henry‐Freundlich adsorption model whilst LDFA+Dual isotherm Kinetics model could describe well the batch adsorption kinetics. The flocculation and flocculation–adsorption experiments were also conducted. The results indicated that flocculation did not perform well on organics removal because of the dominance of low molecular weight organic compounds in synthetic landfill leachate. Consequently, flocculation as pretreatment to adsorption and a combination of flocculation–adsorption could not improve much the organic removal efficiency for the single adsorption process.     

Amine-modified silica surface applied as adsorbent in the phenol adsorption assisted by ultrasound

Abstract

Phenolic compounds are toxic pollutants that are harmful to the human body and aquatic environments, with carcinogenic potential and frequently found in industrial effluents at high levels. Adsorption processes are often employed for the removal of these compounds. Mesoporous materials based on modified silica with amine have been used as adsorbents and can be considered promising for this job due to its high selectivity and better adsorption capacity when compared to materials without any modifications. In addition, adsorption studies can be performed using ultrasound as a mixing mechanism, improving mass transfer through cavitation and acoustic current. In this context, the goal of this study is to modify the surface of mesoporous silica with 3-aminopropyltriethoxysilane (APTES) and to evaluate its efficiency in the adsorption of phenol in an ultrasonic bath. In the phenol adsorption experiments, the Si-APTES showed higher adsorption capacity (12?mg g^?1) than the SiO₂ (2?mg g^?1). The kinetic models of pseudo second-order have shown to be good fits to the experimental data. The adsorption equilibrium data of the phenol on the materials studied were best described in the Langmuir isotherm.     

Metal Adsorption by Activated Carbon: Effect of Complexing Ligands,Competing Adsorbates,Ionic Strength,and Background Electrolyte

Abstract

Cadmium and nickel adsorption isotherms were performed using three activated carbons in ligand-free systems and in the presence of EDTA, succinic acid, PO₄ (Ni only), NH₄BF₄ (Cd only), competing metals (Ni and Cd), and differing ionic strengths and background electrolytes. Generally, all carbons removed metals from the ligand-free systems. Four scenarios were forwarded which described metal adsorption in the presence of various organic and inorganic compounds. The effect of organic and inorganic ligands on metal removal was dependent on the carbon, metal, and ligand type and concentration. The presence of a second heavy metal did not affect removal of the primary metal ion. Increasing ionic strength decreased metal removal for all carbons and metals investigated while the type of background electrolyte had no effect on metal removal.     

Effective adsorption of ciprofloxacin hydrochloride from aqueous solutions using metal-organic framework

ABSTRACT

Metal organic frameworks (MOFs) have become material of special attention due to their high porosity and large surface area. Adsorptive removal of ciprofloxacin hydrochloride using MOFs from aqueous waste and real wastewater has been studied in this work. The MOF-5 synthesized showed higher adsorption capacity as compared to activated charcoal. The adsorption satisfies the pseudo-second-order kinetic model and adsorption isotherm is very well explained by the Freundlich and the Sips isotherm. The adsorption mechanism may be explained by the electrostatic interactions of the pharmaceutical compounds and the MOF-5 surface. Finally, it can be concluded that MOF-5 has shown a great potential for their application in wastewater treatment technology development.     

Adsorption of Cr(VI) on Cross‐Linked Chitosan Beads

Abstract

A possibility of Cr(VI) removal by the adsorption method is discussed in the paper. An adsorbent were hydrogel chitosan beads are produced by the phase inversion method (by changing pH). The possibility of removing Cr(VI) ions by both pure chitosan hydrogel and its chelate compounds (chitosan cross‐linked with Cu(II) and Ag(I) ions) was investigated. The adsorption proceeded from the solutions of potassium dichromate and ammonium dichromate (NH₄)₂Cr₂O₇ and K₂Cr₂O₇. The process rates and adsorption isotherms were determined and described by relevant equations. The process rate was described by the pseudo‐ and second‐order equations, and adsorption equilibria by the Langmuir equations. A slight advantageous change in adsorption properties of chitosan beads was revealed after cross‐linking (for chromium concentration up to 10 g/dm³). A maximum adsorption was 1.1 g_Cr/g chitosan. Results of the studies show that chitosan hydrogel proves useful in the removal of Cr(VI) ions, additionally, cross‐linking with Cu(II) and Ag(I) ions has an advantageous effect in the case of low‐concentrated solutions.     

Adsorptive removal of alizarin dye from wastewater using maghemite nanoadsorbents

ABSTRACT

This is an investigation of the adsorptive removal of anthraquinone dyes, resembled by Alizarin, by utilizing maghemite iron oxide (γ-Fe₂O₃) nanoparticles in aqueous media. The adsorption process was affected by several parameters such as solution pH, adsorbent amount, contact time, and temperature. After optimizing the parameters affecting the adsorption, the process was successful in removing Alizarin dye with an efficiency exceeding 95%. Best adsorption results were achieved at a pH of 11 and contact time of 60 min. The adsorption was shown to follow the Langmuir model suggesting a monolayer and homogeneous coverage. The maximum adsorption capacity (q_m ) was found to be 23.2 mg/g at pH = 11. A thermodynamic study showed that the adsorption process is exothermic and spontaneous at room temperature. The Gibbs free energy of adsorption (-6.79 kJ/mol) obtained in this study suggests a physisorption process. This finding has facilitated the regeneration of the Fe₂O₃ nanocatalyst. Both NaOH and HNO₃ at dilute levels were tested for the regeneration of the nanocatalyst. Regeneration with HNO₃ was successful up to four successive removal cycles with an efficiency >80%. Photodegradation experiments utilizing a UV light were also successful in maximizing the adsorption removal efficiency. A sorption mechanism based on the results obtained in this work is also proposed.     

Adsorption Equilibrium Parameters of Trace Impurities

Abstract

Atmospheric air contains various trace impurities which include oxides of nitrogen, carbon, sulphur, and light hydrocarbons. Prior to cryogenic distillation of air to produce oxygen, nitrogen, and argon, these trace impurities have to be removed since many of these compounds constitute a safety hazard in the plant. In this study, adsorption has been considered for their removal and adsorption behavior of ethylene, acetylene, nitrous oxide, acetonitrile, methyl tert-butyl ether, methyl sulfoxide, dimethyl sulfoxide, and methanol have been studied in the Henry's Law low concentration region with several different adsorbents. Adsorption equilibrium parameters have been determined with samples of Alcan pure alumina, Alcan alumina/13X composites Actiguard 600/650PC, CABSORB Chabazite, Ceca13X, and Clinoptilolite by using the concentration pulse chromatographic technique. Heat of adsorption values and van't Hoff plots have been presented.     

Removal of Nitrate from Water by Adsorption onto Zinc Chloride Treated Activated Carbon

Abstract

Adsorption study with untreated and zinc chloride (ZnCl₂) treated coconut granular activated carbon (GAC) for nitrate removal from water has been carried out. Untreated coconut GAC was treated with ZnCl₂ and carbonized. The optimal conditions were selected by studying the influence of process variables such as chemical ratio and activation temperature. Experimental results reveal that chemical weight ratio of 200% and temperature of 500°C was found to be optimum for the maximum removal of nitrate from water. Both untreated and ZnCl₂ treated coconut GACs were characterized by scanning electron microscopy (SEM), Brunauer Emmett Teller (BET) N₂‐gas adsorption, surface area and Energy Dispersive X‐Ray (EDX) analysis. The comparison between untreated and ZnCl₂ treated GAC indicates that treatment with ZnCl₂ has significantly improved the adsorption efficacy of untreated GAC. The adsorption capacity of untreated and ZnCl₂ treated coconut GACs were found 1.7 and 10.2 mg/g, respectively. The adsorption of nitrate on ZnCl₂ treated coconut GAC was studied as a function of contact time, initial concentration of nitrate anion, temperature, and pH by batch mode adsorption experiments. The kinetic study reveals that equilibrium was achieved within one hour. The adsorption data conform best fit to the Langmuir isotherm. Kinetic study results reveal that present adsorption system followed a pseudo‐second‐order kinetics with pore‐diffusion‐controlled. Results of the present study recommend that the adsorption process using ZnCl₂ treated coconut GAC might be a promising innovative technology in future for nitrates removal from drinking water.     

Enhanced Removal of As(V) from Water with Iron-Coated Spent Catalyst

Abstract

The effectiveness of pretreating a spent catalyst with an iron-salt solution to improve its As(V) removal capacity was studied. Various factors, such as types and concentrations of iron salt, pH. and initial As(V) concentration were investigated for their effects on the improvement of As(V) removal capacity. A significant increase in As(V) removal capacity can be achieved by iron-coated spent catalyst. Adsorption density of As(V) decreased with increasing pH. Langmuir adsorption isotherm was utilized to describe the adsorption reaction. Results from IR analysis and zeta potential measurement indicate that As(Y) is specifically adsorbed onto iron-coated spent catalyst. This study shows that spent catalyst can be converted to a useful adsorbent for As(V) removal.     

Removal of Chlorophenols from Aqueous Solution by Anion-Exchange Resins

Abstract

The effects of pH value and chloride ion concentration on the removal of chlorophenols from aqueous solutions by Purolite A-510 resin [macroreticular polystyrene-divinylbenzene resin with R(CH₃)₂(C₂H₄OH)N⁺ group] are discussed by the species distributions of chlorophenols. Those chlorophenols include phenol, 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. The investigations showed that the chlorophenols could be removed effectively at alkaline conditions where the ion-exchange reaction was dominant. Also, the removal of chlorophenols increased with the number of chlorine atoms on the chlorophenols. The removal of chlorophenols via the ion-exchange reaction was hindered by the presence of chloride ions. The effect of chloride ions, however, was diminished in acidic solutions where the adsorption reaction was dominant. The proposed equilibrium model, which considers both adsorption and ion-exchange reactions, adequately describes the sorption behavior of chlorophenols. The partition constants of the protonated chlorophenols can be estimated from the octanol/water partition coefficients of the phenolic compounds.     

Removal of Phenolic Pollutants from Water Utilizing Mangifera indica (Mango) Seed Waste and Cement Fixation

Abstract

A process for the removal of two chlorophenols (2-chlorophenol and 2,4-dichlorophenol) from water using surface modified mango seed waste by adsorption process followed by cement fixation of the phenols-laden adsorbent is investigated. The two main objectives of this study were to develop efficient adsorbent utilizing mango seed waste by physiochemical activation and to an environmentally-friendly disposal of phenols-laden adsorbent into cement by a fixation process. The results of the present study reveal that the modified mango seed adsorbent showed an efficient adsorption potential for chlorophenols removal from water. The maximum adsorption potential of modified mango seed adsorbent for 2-chlorophenol and 2,4-dichlorophenol was 40.6 and 72.3 mg g^?1, respectively at 25°C. Adsorption kinetic data of chlorophenols adsorption on mango seed adsorbent could be described more favorably by a pseudo-second-order kinetic model. After the adsorption studies, the phenol-laden adsorbent was immobilized in cement for its ultimate disposal. Leachates from the fixed phenols-laden adsorbent exhibit phenols concentrations lower than the drinking water standards. Results from this study suggest the potential utility of agricultural wastes as one of the most promising activated carbon precursors for phenols removal from water and wastewater and the safe disposal of phenol-laden adsorbent into cement by fixation process.     

Adsorptive Removal of 2-Nitrophenol and 2-Chlorophenol by Cross-Linked Algae from Aqueous Solutions

Abstract

The use of the cross-linked marine seaweeds Lessonia nigrescens Bory and Macrocystis integrifolia Bory to remove 2-nitrophenol and 2-chlorophenol from aqueous solutions at room temperature was investigated. The effect of the initial pH, adsorbent dose, and initial concentration of the pollutant were evaluated in batch experiments. The mathematical adsorption models of Langmuir and Freundlich show a mixed adsorptive mechanism of both phenolic compounds by the algae. The calculated parameters demonstrate a high adsorbent to pollutant affinity ratio, indicating the potential effectiveness of these marine seaweeds in the removal of these phenolic compounds from diluted aqueous solutions.     

Low-Temperature Thermal Treatment of Contaminated Soils: Simple Mathematical Models

Abstract

Mathematical models for low-temperature thermal treatment of contaminated soils for the removal of semivolatile organic compounds (SVOCs) by batch and continuous flow units are described. In one set of models the SVOC is assumed to obey a linear adsorption isotherm on the soil; in the second set the SVOC is assumed to be present as nonaqueous phase liquid (NAPL) blobs dispersed within the porous soil. The soil is represented by porous spheres of specified radius through which the escaping SVOC must diffuse. Results of calculations with both models for continuous flow units are presented, and the dependence of the results on the model parameters is discussed.     

Modeling of Adsorptive Filtration of a Leather Dye in a Fixed Bed Column

Abstract

Activated carbons offer an efficient option for the removal of organic and inorganic contaminants from water. However, due to its high costs and difficulty in the regeneration, other low cost adsorbents have been used. In this work, the adsorption capacity of an adsorbent carbon with high iron oxides concentration was compared with that of a commercial activated carbon in the removal of a leather dye from an aqueous solution. The adsorbents were characterized using SEM/EDAX analysis and BET surface area. The capacity of adsorption of the adsorbents was evaluated through the static method at 25°C. The results showed that the color removal was due to the adsorption and precipitation of the dye on the surface of the solids. The adsorption equilibrium was described according to the linear model for the adsorbent carbon and the equilibrium constant was 0.02 L g^?1. The equilibrium of adsorption on activated carbon exhibited a behavior typical of the Langmuir isotherm and the monolayer coverage was 24.33 mg g^?1. A mathematical model was proposed to describe the dynamics of the color removal using a fixed bed considering that the color removal is due to the adsorption and the precipitation of the dye on the adsorbent.     

Biosorption of hexavalent chromium from aqueous solutions using raw coconut fiber as a natural adsorbent

Abstract

This work aims to evaluate the Cr(VI) removal efficiency and adsorption capacity of the raw coconut fiber from synthetic aqueous solutions through the operational parameters as well as to represent the mechanisms of removal by kinetic and isotherm models. The experimental study was conducted in batch system and the optimum conditions for the adsorption of this metal by the biomass were according to: pH 2, contact time of 270?min, and 10?g/L of adsorbent dosage concentration. The removal efficiency obtained for Cr(VI) solutions was 99.2% at concentrations of 25–50?mg/L. For the highest concentrations, the removal decreased from 96.3% to 74.4%, when Cr(VI) solutions ranged from 100?mg/L to 250?mg/L, respectively. The adsorption kinetics was applied and showed a good agreement for pseudo-second-order and Elovich models, which point out a chemisorption. For the adsorption capacity at equilibrium conditions, the best fit was for the Redlich–Peterson isotherm indicating favorable adsorption and monolayer coverage.     

Characterization of graphene oxide supported porous silica for effectively enhancing adsorption of dyes

ABSTRACT

This paper reported the synthesis of graphene oxide (GO)/mesoporous SBA-15 nanocomposite with excellent adsorption properties. The samples were characterized by XRD, FESEM, TEM, FTIR, Raman spectrometer, and surface area analyzer. The adsorption study implied that incorporating GO into SBA-15 frameworks displayed much higher adsorption capacity levels than did pure SBA-15. The composite displayed uniform pore size (6.50 nm), large pore volume (1.035 cm³/g), and high surface area (891 m²/g). The adsorption capacity of samples decreased with increasing sample dosage and adsorption temperature, and increasing initial concentration of dye. The maximum adsorption capacity of the composite for methylene blue was found to be 242 mg/g. The removal efficiency reached 100%. The proposed method was simple and suitable for mass production.     

Development of Green Energy Waste Activated Carbon for Removal of Trivalent Chromium: Equilibrium and Kinetic Modeling

The present work reports on the potential of using a modified activated carbon as an eco-friendly adsorbent (second stage waste), obtained from a bio-diesel waste production plant, for the removal of Cr(III) ions from aqueous solutions. Chemical activation of the green energy waste (GEW), using sulfuric acid as a dehydrating agent, was adapted in this study The effects of pH, contact time, dosage, and initial concentration were evaluated and optimized in a batch processing mode. The modified activated carbon was fully characterized to observe morphological changes using SEM, XRD, and FT-IR techniques. SEM images however, showed significant changes in the carbon morphology before and after the adsorption of Cr(III) ions. The adsorption results indicated that the equilibrium data were in accordance with the Langmuir isotherm, yielding a maximum monolayer adsorption capacity of 171.0 mg g ? 1 at 29° C. Moreover, the kinetic studies indicated that the adsorption process followed a pseudo-second-order model. Assessment of our results revealed that GEW-AC was considered as a prospective adsorbent which could be used as a cost-effective substitute for marketable activated carbons for the removal of Cr(III) ions from wastewater systems.     

Removal of Anionic Dyes from Water using Citrus limonum (Lemon) Peel: Equilibrium Studies and Kinetic Modeling

Abstract

The present study was undertaken to evaluate the adsorption potential of Citrus limonum (lemon) peel as an adsorbent for the removal of two anionic dyes, Methyl orange (MO) and Congo red (CR) from aqueous solutions. The adsorption was studied as a function of contact time, initial concentration, and temperature by batch method. The adsorption capacities of lemon peel adsorbent for dyes were found 50.3 and 34.5 mg/g for MO and CR, respectively. The equilibrium adsorption data was well described by the Langmuir model. Three simplified kinetic models viz. pseudo-first-order, pseudo-second-order, and Weber and Morris intraparticle diffusion model were tested to describe the adsorption process. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients for each kinetic model were determined. It was found that the present system of dyes adsorption on lemon peel adsorbent could be described more favorably by the pseudo-first-order kinetic model. The results of the present study reveal that lemon peel adsorbent can be fruitfully utilized as an inexpensive adsorbent for dyes removal from effluents.     

PURIFICATION OF HYDROCHLORIC ACID BY ISOOCTANE EXTRACTION

ABSTRACT

Removal of organic compounds from hydrocloric acid can be performed by a solvent extraction process followed by a solvent regeneration step by adsorption with sepiolite. The extraction study includes the analysis of the influence of the operating conditions, the determination of the solute distribution coefficient for isooctane and the effect of temperature on the extraction. The adsorption isotherms were calculated to check the technical viability of the method. The obtained efficiency of extraction is close to 90 wt%, whereas that of the solvent regeneration recovery is over 67 wt%