Arsenic adsorption using copper (II) oxide nanoparticles

Arsenic poisoning is a major problem in today's life. To reduce its concentration in drinking water, different metal based compounds were explored as arsenic adsorbents. In the present study, copper (II) oxide nanoparticles were prepared by thermal refluxing technique and used as an adsorbent for arsenic removal from water. Characterization of the adsorbent using TEM, BET, XRD and FTIR implied that the prepared adsorbent was in nano size and had excellent adsorption behavior with surface area of 52.11 m²/g. Systematic adsorption experiments were carried out with different process parameters such as contact time, adsorbent mass, pH, temperature and stirring speed and found that copper (II) oxide had very good efficiency towards arsenic adsorption. Thermodynamic parameters and adsorption kinetics were studied in detailed to know the nature and mechanism of adsorption. Results showed that the adsorption process followed pseudo second order kinetic and endothermic behavior. Adsorption equilibrium was studied with Langmuir and Freundlich isotherm models. The adsorption process followed Langmuir isotherm with an adsorption capacity of 1086.2 μg/g. A regeneration study was proposed in order to reuse the adsorbent for better economy of the process. Finally, a process design calculation is reported to know the amount of adsorbent required for efficient removal of arsenic from aqueous medium.     

Silica nanoparticles modified with a Schiff base ligand: An efficient adsorbent for Th(IV), U(VI) and Eu(III) ions

Modification of SiO₂ nanoparticles by salicylaldiminepropyl results in efficient adsorbents for removal of Th⁴⁺, UO ₂ ²⁺ and Eu³⁺ ions from aqueous solutions. The effect of parameters influencing the adsorption efficiency such as aqueous phase pH, contact time, initial metal ions concentration, adsorbent dosage and temperature dependency of the process was verified and discussed. Under optimal conditions (pH 5.5, adsorbent dosage 0.05 g, contact time 30 min. and 25 °C), thorium and uranyl ions (initial concentration 20 mg/l) were quantitatively removed from 20 ml of sample solution. Under such conditions 85% of europium ions was removed. Comparison of the adsorption efficiency of the studied modified nano-particles with those unmodified ones shows a shift for uptake of the metal ions vs. pH curves towards lower pH values by applying the modified adsorbents. In addition, a significant improvement of europium ions adsorption was observed by using the modified nanoparticles. Kinetics of the process was studied by considering a pseudo second-order model. This model predicts chemisorption for the adsorption mechanism. Freundlich, Langmuir and Temkin models were suitable for describing the equilibrium data of Th⁴⁺, UO₂ ²⁺ and Eu³⁺ adsorption process, respectively. Thermodynamic investigation reveals the adsorption process of the studied ions is entropy driven.     

Unravel the potential of zinc oxide nanoparticle-carbonized sawdust matrix for removal of lead(Ⅱ) ions from aqueous solution

Zinc oxide nanoparticles(ZnOnp) are molecular nanoparticles synthesized by a chemical precipitation method from zinc nitrate tetrahydrate and sodium hydroxide.Carbonized sawdust(CSD) was prepared from sawdust obtained from a local wood mill.The matrix of both provides a better material as an adsorbent.The present study applied the functionality of ZnOnp,CSD,and ZnOnp-CSD matrix as adsorbent materials for the removal of Pb(Ⅱ) ions from aqueous solution.The method of batch process was employed to investigate the potential of the adsorbents.The influence of pH,contact time,initial concentration of adsorbate,the dosage of adsorbents,and the temperature of adsorbate-adsorbent mixture on the adsorption capacity were revealed.The adsorption isotherm studies indicate that both Freundlich and Langmuir isotherms were suitable to express the experimental data obtained with theoretical maximum adsorption capacities(q_m) of 70.42,87.72,and 92.59 mg·g~(-1) for the adsorption of Pb(Ⅱ) ions onto ZnOnp,CSD,and ZnOnp-CSD matrix,respectively.The separation factors(R_L) calculated showed that the use of the adsorbents for the removal of Pb(Ⅱ) ions is a feasible process with R_L 1.The thermodynamic parameters obtained revealed that the processes are endothermic,feasible,and spontaneous in nature at 25-50℃.Evaluation of the kinetic model elected that the processes agreed better with pseudo-second order where the values of rate constant(k_2) obtained for the adsorption of Pb(Ⅱ) ions onto ZnOnp,CSD,and ZnOnp-CSD matrix are 0.00149,0.00188,and 0.00315 g·mg~(-1)·min~(-1),respectively.The reusability potential examined for four cycles indicated that the adsorbents have better potential and economic value of reuse and the ZnOnp-CSD matrix indicates improved adsorbent material to remove Pb(Ⅱ) ions from aqueous solution.     

Experimental design and batch experiments for optimization of Cr(VI) removal from aqueous solutions by hydrous cerium oxide nanoparticles

Hydrous cerium oxide (HCO) was synthesized by intercalation of solutions of cerium(III) nitrate and sodium hydroxide and evaluated as an adsorbent for the removal of hexavalent chromium from aqueous solutions. Simple batch experiments and a 2⁵ factorial experimental design were employed to screen the variables affecting Cr(VI) removal efficiency. The effects of the process variables; solution pH, initial Cr(VI) concentration, temperature, adsorbent dose and ionic strength were examined. Using the experimental results, a linear mathematical model representing the influence of the different variables and their interactions was obtained. Analysis of variance (ANOVA) demonstrated that Cr(VI) adsorption significantly increases with decreased solution pH, initial concentration and amount of adsorbent used (dose), but slightly decreased with an increase in temperature and ionic strength. The optimization study indicates 99% as the maximum removal at pH 2, 20 °C, 1.923 mM of metal concentration and a sorbent dose of 4 g/dm³. At these optimal conditions, Langmuir, Freundlich and Redlich–Peterson isotherm models were obtained. The maximum adsorption capacity of Cr(VI) adsorbed by HCO was 0.828 mmol/g, calculated by the Langmuir isotherm model. Desorption of chromium indicated that the HCO adsorbent can be regenerated using NaOH solution 0.1 M (up to 85%). The adsorption interactions between the surface sites of HCO and the Cr(VI) ions were found to be a combined effect of both anion exchange and surface complexation with the formation of an inner-sphere complex.     

Application of graphene-based adsorbents in the treatment of dye-contaminated wastewater; kinetic and isotherm studies

The adsorption of methylene blue (MB) on graphene-based adsorbents was tested through the batch experimental method. Two types of graphene-based adsorbents as graphene oxide (GO) and reduced graphene oxide (RGO) were compared to investigate the best adsorbent for MB removal. So that optimizing the MB removal for the selected type of graphene-based adsorbent, the diverse experimental factors, as pH (2–10), contact time (0–1440 min), adsorbent dosage (0.5–2 g/L), and initial MB concentration (25–400 mg/L) were analyzed. The conclusions indicated that the MB removal rised with an increase in the initial concentration of the MB and so rises in the amount of adsorbent used and initial pH. Maximum dye removal was calculated as 99.11% at optimal conditions after 240 min. Adsorption data were compiled by the Langmuir isotherm (R²: 0.999) and pseudo-second-order kinetic models (R²: 0.999). The Langmuir isotherm model accepted that the homogeneous surface of the GO adsorbent covering with a single layer. And the adsorption energy was calculated as 9.38 kJ mol⁻¹ according to the D-R model indicating the chemical adsorption occurred. The results show that GO could be utilized for the treatment of dye-contaminated aqueous solutions effectively.     

Synthesis and adsorption performance of fly ash/steel slag-based geopolymer for removal of Cu (II) and methylene blue

In order to realize the value-added resource utilization of solid waste, geopolymer particle adsorbents were prepared at low temperatures using silica-aluminum-rich fly ash and steel slag powders as raw materials. In order to investigate the mechanism of their adsorption of dyes and heavy metal ions from wastewater, the effects of steel slag/fly ash ratio, adsorbent dosage, initial concentration of methylene blue (MB) and Cu²⁺ solution, adsorption time and temperature on the adsorption performance of the fly ash/steel slag-based geopolymer adsorbents were investigated, systematically. Results presented that the adsorption capacities of MB and Cu²⁺ were 33.30 and 24.15 mg/g, and the removal efficiencies were 99.90% and 96.59% with the dosages of 3 and 4 g/L geopolymer adsorbents (steel slag/fly ash ratio of 20 wt.%), respectively. The adsorption processes of MB and Cu²⁺ on the adsorbents were in accordance with the proposed pseudo-second-order and Langmuir isotherm models, which mainly included physical and chemical adsorption mechanisms. The adsorption was a spontaneous endothermic process. The fly ash/steel slag-based geopolymer had good removal ability for dyes and heavy metal ions, and it could maintain good adsorption performance after three cycles of regeneration. It had potential application in wastewater treatment.     

Relationship between the highest occupied molecular orbital (HOMO) electron density of adsorption sites on carbon and the Freundlich exponent

This paper discusses the relationship between the electron density for various groups of phenolic compounds and their adsorption capacity on activated carbon. Chloro- and nitrophenols were used as test adsorbates, and as-received or HNO₃-modified granular activated carbon (GAC) samples were used as adsorbents. The isotherms for these systems were determined by the batch bottle technique. The highest occupied molecular orbital (HOMO) electron density at the adsorption site was estimated using the CAChE program, and a relationship between the Freundlich exponent 1/n and the HOMO density of the adsorbent was found by combining the experimental and computational results for the modified GAC. The Freundlich equation is described as: n_ads=k(C)^1/n, where n_ads, k, C, 1/n are the weight of adsorbate per weight of adsorbent (g g⁻¹), the Freundlich coefficient, the concentration of adsorbate in bulk solution (g l⁻¹), and the Freundlich exponent, respectively. The value of the Freundlich exponent 1/n for the systems investigated decreased linearly with an increase in ‘adsorbent’ HOMO density. The HOMO electron density of both the adsorbate and the adsorbent were the major factors determining the value of the Freundlich exponent, 1/n, for phenolic adsorbate-carbonaceous adsorbent systems.     

Removal of high-level Fe from aqueous solution using natural inorganic materials: Bentonite (NB) and quartz (NQ)

Decontamination of high-level Fe³⁺ ions from a model aqueous solution using natural inorganic Quartz (NQ) and Bentonite (NB) has been studied. The adsorption equilibrium studies are performed with a constant initial Fe³⁺ ion concentrations (namely 100, 200, 300 and 400 mg.L^-1) and varying adsorbent weight. The adsorption percentages of Fe³⁺ ions increase sharply by increasing adsorbent doses, in which the adsorption percentage of Fe³⁺ using NB (approx. 60%) is found higher than in case of NQ (approx. 40%) in whole adsorption dosages. The maximum adsorption percentages of Fe³⁺ using both adsorbents are achieved within the first 60 minuets, and then desorption process is taken place. As the initial concentration of ions increases the percentage removal using NB decreases, while the adsorption using NQ is less affected by the initial concentration; it is found 40% in whole different initial concentration (50 - 400 mg.L^-1). The best temperature for the maximum adsorption is found 30 - 40°C for both adsorbents. The obtained experimental data has well described by Freundlich isotherm model into both NQ and NB. The Freundlich constant K_f for the adsorption of Fe³⁺ using NB is greater than using of NQ for the initial concentration 400 mg.L^-1. The negative value of ?G° confirms the feasibility of the process and the spontaneous nature of adsorption with a high preference for metal ions to adsorb onto NB (ΔG° = -13.9) more easily than NQ (ΔG° = -13.4).     

Adsorption of Pb(II) from aqueous solution to Ni-doped bamboo charcoal

Bamboo charcoal (BC) obtained by pyrolysis of Makino bamboo in the absence of oxygen was used as support for the preparation of Ni-doped adsorbent (Ni-BC). The low-cost composite was characterized and used as an adsorbent for Pb(II) removal from water. The results showed that both BET surface area and total pore volume of Ni-BC increased. The adsorption of Pb(II) strongly depended on solution pH, temperature and ionic strength. The adsorption isotherms followed Langmuir isotherm model well, and the maximum adsorption capacities of Pb(II) at 298 K were 25.0 and 142.7 mg/g for BC and Ni-BC, respectively. The adsorption processes were well fitted by pseudo-second-order kinetic model. Thermodynamic parameters showed that the adsorptions of Pb(II) onto both adsorbents were feasible, spontaneous, and exothermic under the studied conditions. The spent Ni-BC could be readily regenerated for reuse.     

Comparison of removal of bromothymol blue from aqueous solution by multiwalled carbon nanotube and Zn(OH)2 nanoparticles loaded on activated carbon: A thermodynamic study

In this research Zn(OH)₂ nanoparticles loaded on activated carbon (Zn(OH)₂-NPs-AC) as novel adsorbent and raw multiwalled carbon nanotube (MWCNT) were applied for efficient removal of bromothymol blue (BTB). Both adsorbent has been characterized with different techniques such and SEM, XRD and UV–vis spectrometry. Their size was less than 100 nm. In the removal process the variables are pH, temperature, concentration of BTB, amount of adsorbent and contact time that their influence on removal of BTB was optimized using one at a time approach in batch procedure. Adsorptions of BTB on bath adsorbent depend highly on pH. Following the investigation of temperature effect, the thermodynamic parameters including change in entropy, enthalpy and free Gibbs energy were calculated. For both adsorbents, positive value of enthalpy and negative value of ΔG⁰ show routine feasibility of adsorption using energy. At optimum value of variables, the removal processes onto both adsorbent have high adsorption capacity for best fitting model Langmuir, i.e. for Zn(OH)2-NP-AC and 150 mg/g for PAC. The adsorption rates were well explained with pseudo second order and interparticle diffusion model. It is expected that there could an increase in the number of reactive sites due to their expected high volume, pore size and high surface area.     

Application of ZnO and TiO<Subscript>2</Subscript> nanoparticles coated onto montmorillonite in the presence of H<Subscript>2</Subscript>O<Subscript>2</Subscript> for efficient removal of cephalexin from aqueous solutions

This study considers the feasibility of uptake of cephalexin, an emerging contaminant, from aqueous solutions by using green local montmorillonite (GLM), montmorillonite coated with ZnO (ZnO/GLM) and montmorillonite coated with TiO₂ (TiO₂/GLM) in the presence of H₂O₂. Batch adsorption experiments were carried out as a function of pH, initial concentration of the cephalexin, adsorbent dosage, contact time, and temperature. Finally, the adsorbents were characterized by XRD, SEM and FTIR analyses. XRD patterns showed dramatic changes in the adsorbents after loading with the nanoparticles, confirming successful placing of the nanoparticles onto GLM. The GLM mineral surface after nanoparticle loading appears to be fully exposed and more porous with irregular shapes in particles diameters of 1-50 microns. FTIR analyses also confirmed dramatic changes in surface functional groups after modification with these nanoparticles. The results showed that the removal efficiency of cephalexin was better at lower pH values. Totally, the removal efficiency increased with increase in adsorbent dosage and contact time and decreased with concentration and temperature increase. The thermodynamics values of ΔG ^o and ΔH ^o revealed that the adsorption process was spontaneous and exothermic. In isotherm study, the maximum adsorption capacities (qm) were obtained to be 7.82, 17.09 and 49.26 mg/g for GLM, ZnO/GLM and TiO₂/GLM, respectively. Temkin constant (B _T ) showed that adsorption of cephalexin from solution was exothermic for all three adsorbents.     

Superparamagnetic polyvinylpyrrolidone/chitosan/Fe3O4 electrospun nanofibers as effective U(VI) adsorbents

Magnetoactive electrospun fibrous membranes consisting of polyvinylpyrrolidone (PVP), chitosan (CS) and pre-fabricated, double-layer oleic acid-coated magnetite nanoparticles (OA.OA.Fe₃O₄) were fabricated and evaluated as new adsorbent materials for the removal and recovery of uranium (U(VI)) from aqueous solutions. The adsorption has been investigated by batch-type experiments and the solid material has been characterized by X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy/energy dispersive X-ray analysis (TEM/EDX) and vibration sample magnetometry (VSM) measurements prior and after uranium adsorption. The experimental adsorption data were found to be well fitted with the Langmuir isotherm and the pseudo-second order kinetic model. The results indicate that PVP/CS/OA.OA.Fe₃O₄ fibrous adsorbents exhibit good adsorption properties towards U(VI) in aqueous solutions, achieving a q_max value of 0.77 mol kg⁻¹ (183.3 mg g⁻¹) at pH 6.0. The experiments regarding the regeneration and reuse of the magnetoactive adsorbents were carried out using Na₂CO₃, at pH ~11. After four cycles, the percentage relative adsorption remained stable (~100%) whereas the desorption percentage decreased from 31.9% to 21.0%. Generally, the presented results demonstrate that the incorporation of the Fe₃O₄ NPs has a positive effect on the adsorption efficiency of U(VI) from aquatic environments.     

Removal of aqueous toxic Hg(II) by functionalized mesoporous silica materials

BACKGROUND: Hg(II) is one of the most toxic metals and has received particular attention in environmental pollution. Hg(II) pollution is common in water sources, so rapid and efficient methods must be developed for its removal from water samples. Mesoporous silica (MS) is an ideal adsorbent due to its high surface area and biocompatibility. The efficiency and selectivity of MS adsorbents can be improved by surface modification. RESULTS: A new sorbent for trace Hg(II) removal was developed by grafting 1‐(3‐carboxyphenyl)‐2‐thiourea (CPTU) onto SBA‐15 mesoporous silica. The optimum pH range for Hg(II) adsorption was 3‐7 and the maximum static adsorption capacity was 64.5 mg g^?1. An enrichment factor of 150 was obtained with a relative standard deviation < 1.5% (n = 8). Common coexisting ions did not interfere with the adsorption of Hg(II) under optimal conditions. Quantitative recovery was achieved by stripping with a mixed solution of 1 mol L^?1 HCl and 5% CS(NH₂)₂. Efficient adsorption capacity of the recycled material could still be maintained at a level of 95% at the 7th cycle. CONCLUSION: 1‐(3‐carboxyphenyl)‐2‐thiourea functionalized SBA‐15 mesoporous silica was synthesized and applied for Hg(II) removal from water samples with high efficiency and selectivity. Copyright © 2012 Society of Chemical Industry     

O‐carboxymethyl chitosan entrapped by silica: preparation and adsorption behaviour toward neodymium (III) ions

BACKGROUND: The recovery of neodymium from dilute solutions has become important because of its wide application in industry. This work reports the preparation of novel carboxymethyl chitosan adsorbents entrapped by silica (SiO₂/CMCH) and their application for adsorption of neodymium(III) ions from aqueous solution. RESULTS: The effect of the CMCH content, equilibrium pH (pH_e), contact time, initial concentrations of Nd(III) and temperature on the adsorption was investigated. The amount of Nd(III) adsorption increases with increasing pH_e, which can be explained by the pH‐titration curve of CMCH. Temperature has a positive effect on Nd(III) adsorption, and the amount adsorbed is 53.04 mg g^?1 dry adsorbent or 434.75 mg g^?1 CMCH at 328 K. Adsorption kinetics and isotherm can be described by the pseudo‐second‐order model and Langmuir equation. Both complexation and ion exchange mechanisms are believed to play an important role in Nd(III) adsorption, and possible coordination between CMCH and Nd(III) is speculated. Complete desorption can be reached when the concentration of HCl is more than 0.1 mol L^?1. CONCLUSION: A novel method was developed to prepare SiO₂/CMCH adsorbents through a one‐step sol‐gel strategy. The prepared adsorbents were biocompatible and non‐toxic with a good adsorption ability for Nd(III), and could be used for adsorptive recovery of Nd(III) from aqueous solutions. © 2012 Society of Chemical Industry     

Equilibrium and Kinetic Studies of Ni (II) Adsorption using Pineapple and Bamboo Stem Based Adsorbents

This work addresses the preparation and characterization of inexpensive adsorbents for the removal of Ni (II) from aqueous solutions. Activated carbon based adsorbents have been prepared from plant based biomass resources, namely Pineapple stem ( Ananas Comosus ) and Bamboo Stem ( Bambuseae ). Adopting phosphoric acid and heat treatment techniques, it has been observed that the bamboo stem activated charcoal (BSAC) and pineapple stem (PS) adsorbents had a BET surface area of 116 and 11.47 m ² /g, respectively. FTIR analysis indicated that various surface functional groups (such as C ≡ N stretching, stretching vibration of C = O, –CH₃ wagging and C–O stretching vibration) contribute towards Ni (II) adsorption. Batch mode adsorption experiments were conducted for these adsorbents in the range of 50–300 mg/L Ni (II) solution concentration, 2–10 pH, 15–300 min. contact time, and 0.02–0.1 g/50 mL dosage. The BSAC adsorbent has been characterized with a metal uptake and %removal of 121.72 mg/g and 92.47, respectively, which corresponds to 45% higher metal uptake than corresponding bamboo based adsorbents presented in the literature. Further experimentation with BSAC enabled to achieve activated charcoal with surface area values similar to that of the commercial activated carbon adsorbent. The bamboo adsorbent has also been evaluated to perform similar to the commercial activated carbon for the removal and recovery of Pd (II) from synthetic electroless plating solutions. Also, a conceptual cost analysis indicated and affirmed towards the potential of the BSAC adsorbents for waste water treatment applications.     

Eudragit E100/poly(ethylene oxide) electrospun fibers for DNA removal from aqueous solution

The development of new strategies for production of low-cost deoxyribonucleic acid (DNA) adsorbents based on electrospun fibers of block copolymers [Eudragit E-100/poly(ethylene oxide) (PEO)] is a promising way for fast retrieval of free of degradation double-stranded DNA chains from aqueous solution. The adsorption takes place through electrostatic interaction between DNA and oppositely charged electrospun fibers that provide high surface area for DNA adsorption. The adsorption capacity observed for electrospun fibers of Eudragit E100/PEO (considering as target molecules the salmon sperm DNA) was in order of 44.31 mg g⁻¹, following the Langmuir model in a typical adsorption at solid/liquid interface (pseudo-second-order model), that characterizes the electrospun fibers as promising templates for removal of biologic components and further use in molecular biology techniques, as DNA amplification by polymerase chain reaction. The reuse and integrity of membranes after long period of adsorption were tested, confirming the potential of material as adsorbent. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47479.     

Nickel(Ⅱ) removal from water using silica-based hybrid adsorbents:Fabrication and adsorption kinetics

A series of novel silica-based hybrid adsorbents were prepared by the crosslinking reaction of N-[3-(trimethoxysilyl)propyl] ethylene diamine(TMSPEDA) with epichlorohydrin(ECH) via a sol–gel process.Fourier transform infrared(FTIR) spectra confirmed that the reaction occurred.TGA curves showed that the thermal stability of these hybrid adsorbents reached as high as 180 °C.As a typical example,the adsorption performance of nickel(II) ions onto an adsorbent(the volume ratio of TMSPEDA and ECH was 4:1) was explored.It was found that the adsorption of nickel(II) ions onto this adsorbent followed the Lagergren pseudo-second-order kinetic model.The investigation of the adsorption mechanism demonstrated that nickel(II) adsorption was chiefly controlled by diffusion–chemisorption,suggesting that more diffusion processes were involved in the adsorption of nickel(II) ions onto this type of adsorbents.Desorption experiment indicates that these hybrid adsorbents can be regenerated.These findings reveal that this type of silica-based hybrid adsorbent is promising in the separation and recovery of nickel(II) ions from Ni-containing wastewater or contaminated water.     

Removal of methylene blue from coloured effluents by adsorption onto SBA‐15

Adsorption has been proven to be the most efficient method for quickly lowering the concentration of dissolved dyes in an effluent. In this regard, activated carbon is the most widely used adsorbent for removal of dyes from aqueous solution. However, the high cost of production and regeneration make it uneconomical. Therefore, inorganic adsorbents (e.g. zeolites) with high surface areas have been used as alternatives to carbon adsorbents. Microporous zeolites ZSM‐5, NH₄‐Beta, MCM‐22 and mesoporous materials MCM‐41 have been investigated for the removal of dyes from aqueous solutions and they show effective adsorption performance. SBA‐15 possesses a larger pore size and pore wall thickness than MCM‐41. As a result, SBA‐15 has greater potential for the adsorption of methylene blue with larger molecule size and higher hydrothermal stability than the M41S family. SBA‐15 is an excellent adsorbent for methylene blue (MB), exhibiting 280 mg g^?1 adsorption capacity and about 100% fading rate for MB. The adsorptive process is so fast that adsorption equilibrium is achieved in 5 min. In addition, SBA‐15 can be effectively recovered by calcination and reused 10 times without significant loss in removal of MB from aqueous solution. The efficient adsorption of MB molecules onto SBA‐15 was ascribed to MB adsorbed into the pore channels of SBA‐15, which was confirmed by nitrogen physisorption analysis of the adsorbent before and after adsorption. The long reuse life of the adsorbent suggests a high potential for application in industry. Copyright © 2010 Society of Chemical Industry     

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.     

Removal of As(V) Using an Iron-Impregnated Ion Exchange Bead

The ability of an iron-impregnated ion exchange bead (PWX5) to remove As(V) from ground water was investigated. The effects of particle size, solution pH, As(V) concentration, competition, adsorbent concentration, temperature, iron content, and iron accessibility on removal kinetics and/or equilibrium were determined. PWX5's performance was compared to other iron-based adsorbents, primarily Bayoxide® E-33 (E-33), a granular ferric oxide, for arsenic removal performance. All of the factors cited impacted either the amount of As(V) adsorbed or the rate of adsorption. Stirred batch reactor data showed the rate of adsorption increased as particle size decreased and bottle point isotherm data showed As(V) adsorption maximum capacity increased with higher initial adsorbate concentration. The presence of phosphate and silicate reduced the amount of As(V) adsorbed as did a pH > 7.0. PWX5 is durable, rather homogeneous in size and effective at removing As(V). It is a viable alternative to E-33 which has a wider size distribution and wears more easily.