A nanoporous adsorbent for removal of furfural from aqueous solutions

The adsorption of furfural by a surfactant-containing nanoporous material is investigated in the present study. We used cetyltrimethylammonium bromide (CTAB) as the cationic surfactant for synthesis of MCM-48. Batch adsorption studies demonstrate that the surfactant-containing MCM-48 has a significant capacity for adsorption of furfural from aqueous solution. The parameters investigated in this study included pH, contact time, agitation speed and initial furfural concentration. The adsorption process of furfural is tested with Langmuir and Freundlich isotherm models. Application of the Langmuir isotherm to the systems yielded maximum adsorption capacity of 196.1 mg/g.     

Wollastonite as adsorbent for removal of Fe(II) from water

Wollastonite was used as an adsorbent for the removal of Fe(II) at different experimental conditions. The extent of removal is favourable at low concentration and low temperature. Maximum adsorption was noted at pH 4.0. The batch adsorption kinetics has been described by a first order rate expression, and the surface mass transfer coefficients and diffusion coefficients have been calculated at different temperatures. The intraparticle transport of Fe(II) within the pores of wollastonite is found to be the rate limiting step. The applicability of the Langmuir isotherm for the present system has been tested at different temperatures. Thermodynamic parameters indicate the exothermic nature of Fe(II) adsorption on wollastonite. The variation of adsorption with pH has been explained on the basis of interaction of iron species with negatively charged constituents of adsorbent.     

Novel method for removal of NO x and SO2 by sustainable electrochemical process using Ag(I)/Ag(II) redox mediator

The objective of this work was to develop a process for removal of industrial waste gases like NO, NO₂ and SO₂ by electrochemically generated Ag(I)/Ag(II) redox mediator system in aqueous nitric acid medium. 100% removal efficiencies were achieved in these studies for removal of NO _x and SO₂ with Ag(II) ions in room temperature and atmospheric pressure. This Ag(I)/Ag(II) redox mediator system can be regenerated continuously during the scrubbing process.     

Water purification of removal aqueous copper (II) by as-grown and modified multi-walled carbon nanotubes

This study compares aqueous copper (II) adsorbed onto as-grown and modified carbon nanotubes (CNTs), using H₂SO₄ and H₂SO₄/KMnO₄ processes. H₂SO₄ and H₂SO₄/KMnO₄ modifications reduced pH_iep and Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that some functional groups were formed on modified CNTs. The adsorption capacity of copper (II) onto modified CNTs was greater than that of as-grown CNTs, especially at pH 6. The results demonstrate that the modified processes increased the adsorption capacity because the functional groups were generated on the modified surfaces of the CNTs. Additionally, the adsorption capacity of copper (II) onto as-grown and modified CNTs both increased with temperature, and the results indicated that the Langmuir isotherm fitted the experimental data well. Simulation results indicated that the ΔH⁰ values of as-grown, H₂SO₄-modified CNTs and H₂SO₄/KMnO₄-modified CNTs were 4.83, 14.37 and 29.92 kJ/mol, respectively. Based on ΔH⁰, the adsorption of Cu²⁺ onto H₂SO₄/KMnO₄-modified CNTs is suggested to proceed simultaneously by physisorption and chemisorption but that onto as-grown and H₂SO₄-modified CNTs may proceed only by physisorption.     

Synthesis of Chelating Resin PETU and Its Adsorption to Ag(I)

A novel chelating resin (PETU) with thiourea groups in its main chain was synthesized by the reaction of O,O'-butane-1,4-diyl dicarbonisothiocyanatidate and triethylene tetraamine. The adsorption of Ag(I) on PETU was investigated by batch tests. The results showed that adsorption data fitted Boyd's diffusion equation of liquid film and the adsorption was controlled by liquid film diffusion. Under the temperatures between 15～60 ℃, the adsorption capacity decreased with the increase of temperature, and increased with the increase of initial concentration of Ag(I). The experimental data fitted Langmuir and Freundlich equations, and the correlation coefficients for Langmuir equation were between 0.9965～0.9998, and those for Freundlich equation were between 0.8211～0.9810, and increased with the adsorption temperature. △H, △G and △S calculated by thermodynamic formulae were all negative, which meant that the adsorption process was exothermic and spontaneous, and the entropy decreased during the process. XPS results showed that N, S and O atoms were the electron donors to coordinate with Ag.     

A modified cellulose adsorbent for the removal of nickel(II) from aqueous solutions

A series of adsorption studies was carried out on a glycidyl methacrylate‐ modified cellulose material functionalised with imidazole (Cellulose‐g‐GMA‐Imidazole) to assess its capacity in the removal of Ni(II) ions from aqueous solution. The study sought to establish the effect of a number of parameters on the removal of Ni(II) from solution by the Cellulose‐g‐GMA‐Imidazole. In particular, the influence of initial metal concentration, contact time, solution temperature and pH were assessed. The studies indicated a Ni(II) uptake on the Cellulose‐g‐GMA‐Imidazole sorbent of approximately 48 mg g^?1 of nickel from aqueous solution. The adsorption process fitted the Langmuir model of adsorption and the binding process was mildly endothermic. The kinetics of the adsorption process indicated that nickel uptake occurred within 400 min and that pseudo‐second order kinetics best describe the overall adsorption process. Nickel(II) adsorption, recovery and re‐adsorption studies indicated that at highly acidic pH values the adsorbent material becomes unstable, but in the range pH 3–6, the adsorbent is stable and shows limited but significant Ni(II) recovery and re‐adsorption capability. Copyright © 2006 Society of Chemical Industry     

Mineral waste from coal mining for removal of astrazon red dye from aqueous solutions

The use of mineral waste from coal mining (MWCM) as an adsorbent for the removal of astrazon red dye (AR) from aqueous solution was studied in detail. Batch adsorption experiments were carried out under varied conditions, such as different initial concentrations of AR, contact time, pH, temperature and calcination of the adsorbent. Investigations revealed that the maximum colour removal was observed for unbuffered solutions. MWCM calcinated at 400 °C (MWCM400) was more efficient for dye removal than samples calcinated at other temperatures. The adsorption isotherm of AR on MWCM400 was determined and correlated with the Langmuir and Freundlich models; the results indicated a better fit for the Langmuir model at all the temperatures studied. Kinetic data were fitted with both pseudo-first-order and pseudo-second-order kinetic models, and the data were found to follow the latter model more adequately. Calculated thermodynamic and kinetic parameters indicate a predominantly physisorption mechanism for the adsorption of AR onto MWCM400. The amount of AR adsorbed by MWCM400 per unit area was found to be two or three times greater than that by several comparable adsorbents.     

Kaolinite, montmorillonite, and their modified derivatives as adsorbents for removal of Cu(II) from aqueous solution

Adsorption of metals by clay minerals is a complex process controlled by a number of environmental variables. The present work investigates the removal of Cu(II) ions from an aqueous solution by kaolinite, montmorillonite, and their poly(oxo zirconium) and tetrabutylammonium derivatives. The entry of ZrO and TBA into the layers of both kaolinite and montmorillonite was confirmed by XRD measurement. The specific surface areas of kaolinite, ZrO-kaolinite, TBA-kaolinite, montmorillonite, ZrO-montmorillonite, TBA-montmorillonite were 3.8, 13.4, 14.0, 19.8, 35.8 and 42.2 m²/g, respectively. The cation exchange capacity (CEC) was measured as 11.3, 10.2, 3.9, 153.0, 73.2 and 47.6 meq/100 g for kaolinite, ZrO-kaolinite, TBA-kaolinite, montmorillonite, ZrO-montmorillonite, TBA-montmorillonite, respectively. Adsorption increased with pH till Cu(II) ions became insoluble in alkaline medium. The kinetics of the interactions suggests that the interactions could be best represented by a mechanism based on second order kinetics (k₂ = 7.7 × 10⁻² to 15.4 × 10⁻² g mg⁻¹ min⁻¹). The adsorption followed Langmuir isotherm model with monolayer adsorption capacity of 3.0–28.8 mg g⁻¹. The process was endothermic with ΔH in the range 29.2–50.7 kJ mol⁻¹ accompanied by increase in entropy and decrease in Gibbs energy. The results have shown that kaolinite, montmorillonite and their poly(oxo zirconium) and tetrabutyl-ammonium derivatives could be used as adsorbents for separation of Cu(II) from aqueous solution.     

Synthesis of 2-mercaptobenzothiazole and 2-mercaptobenzimidazole derivatives condensed with carbohydrates as a potential antimicrobial agents

The thiazole and imidazole nucleus, as well as carbohydrates are important classes of compounds found in many natural and synthetic products with a wide range of biological activities. Due to the importance of these classes of compounds as antimicrobial agents, the present article reports the synthesis of a new series of nine compounds based on the coupling of 2-mercaptobenzothiazole and 2-mercaptobenzimidazole with different carbohydrates.     

Efficient removal of cationic dyes from aqueous solutions using a modified poly(ethylene terephthalate) fibers adsorbent

ABSTRACT

A novel adsorbent was synthesized through functionalization of glycidyl methacrylate-g-poly(ethylene terephthalate) (GMA-g-PET) fibers with iminodiacetic acid (IDA) to give IDA-GMA-g-PET fibers. This adsorbent was then exploited for the removal of Malachite Green (MG) and Rhodamine B (RB) dyes. MG has shown faster adsorption kinetics and equilibrium was attained in 15 mins. and 90 mins. for MG and RB, respectively. IDA-GMA-g-PET fibers showed 100% removal efficiency for MG and RB dyes from the solutions having initial concentrations of 300 mg L^?1and 200 mg L^?1, respectively. Desorption conditions of dyes and reusability of the fibers were also investigated.     

Polymer‐grafted banana (Musa paradisiaca) stalk as an adsorbent for the removal of lead(II) and cadmium(II) ions from aqueous solutions: kinetic and equilibrium studies

This study examined the effectiveness of a new adsorbent prepared from banana (Musa paradisiaca) stalk, one of the abundantly available lignocellulosic agrowastes, in removing Pb(II) and Cd(II) ions from aqueous solutions. The adsorbent (PGBS‐COOH) having a carboxylate functional group at its chain end was synthesized by graft copolymerization of acrylamide on to banana stalk, followed by functionalization. Batch adsorption experiments were carried out as a function of solution pH, ionic strength, contact time, metal concentration, adsorbent dose and temperature. A pH range of 5.5–8.0 was found to be effective for the maximum removal for both Pb(II) and Cd(II). Metal uptake was found to decrease with increase in ionic strength due to the expansion of the diffuse double layer and, more importantly, the formation of some chloro complexes (since NaCl was used in the adjustment of ionic strength), which do not appear to be adsorbed to the same extent as cations [M²⁺ and M(OH)⁺]. The kinetic studies showed that an equilibrium time of 3 h was needed for the adsorption of Pb(II) and Cd(II) on PGBS‐COOH and adsorption processes followed a pseudo‐second‐order equation. The Langmuir isotherm model fitted the experimental equilibrium data well. The maximum sorption capacity for Pb(II) and Cd(II) ions was 185.34 and 65.88 mg g^?1, respectively, at 30 °C. The thermodynamic parameters such as changes in free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were derived to predict the nature of adsorption. The isosteric heat of adsorption was found to be independent of surface coverage. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC‐50, for comparison. Synthetic wastewater samples were treated with the adsorbent to demonstrate its efficiency in removing Pb(II) and Cd(II) ions from industrial wastewaters. Acid regeneration was tried for several cycles with a view to recovering the sorbed metal ions and also restoring the sorbent to its original state. Copyright © 2005 Society of Chemical Industry     

Electrophoretically deposited halloysite nanotubes coating as the adsorbent for the removal of methylene blue from aqueous solution

Halloysite nanotubes (HNTs) coatings were prepared by electrophoretic deposition (EPD) from different alcoholic suspensions using polyethyleneimine (PEI) as the dispersant. The results of conductivity, zeta potential, FTIR and thermal analysis showed that PEI is protonated in alcoholic suspensions and then adsorbed on the surface of HNTs enhancing their zeta potential and so colloidal stability. Optimum concentration of PEI decreased with molecular size of alcohol due to the more adsorption of PEI on HNTs. Kinetics of EPD was the fastest from the suspensions with the highest zeta potential. HNTs coatings exhibited high resistance against cracking during their drying due to the self-reinforcement provided by long HNTs and the presence of PEI in their composition which acts as the binder. The coating (6cm²) deposited from ethanolic suspension with 0.5?g/l of PEI (optimum suspension) removed 36% of MB from its aqueous solution (concentration: 5?mg/l and volume: 30?ml) within 2?h.     

Preparation and characterization of iron(III) complex of an amino‐functionalized polyacrylamide‐grafted lignocellulosics and its application as adsorbent for chromium(VI) removal from aqueous media

The growth and decay processes of optically induced birefringence in two novel azobenzene compounds [one was a hyperbranched poly(aryl ether) containing azobenzene groups, and the other was a hydrogen‐bonded complex] were studied. The temperature dependence of the birefringence signal was investigated. The curves for the buildup and decay of birefringence fit well to biexponential functions. The dependence of the fitting parameters on the temperature is also discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Retention properties of efficient adsorbent to silver(I)

The binding capability of crosslinked poly(acrylic acid‐co‐2‐acrylamide‐2‐methyl‐1‐propane sulfonic acid) for silver(I) ions by the batch equilibrium method is investigated. The effects of the pH, temperature, time of contact, and resin–metal ion molar ratio on the retention ability are studied. The retention for silver(I) increases from 21.7% at pH 1 to 94.6% at pH 5. The adsorption capacity at pH 5 is 1.18 meq/g dry resin. The maximum load capacity at the optimum pH is determined. In order to recover the resin, elution runs in acid and basic media are carried out. The best eluent is 4M HNO₃ (84.9%). Moreover, retention–elution cycles are performed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1501–1506, 2002     

A chelating cellulose adsorbent for the removal of Cu(II) from aqueous solutions

Regenerated cellulose wood pulp was grafted with the vinyl monomer glycidyl methacrylate (GMA) using ceric ammonium nitrate as initiator and was further fuctionalised with imidazole to produce a novel adsorbent material, cellulose‐g‐GMA‐imidazole. All cellulose, grafted cellulose and functionalized cellulose grafts were physically and chemically characterized using a number of analytical techniques, including elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, and scanning electron microscopy. The cellulose‐g‐GMA material was found to contain 1.75 mmol g^?1 epoxy groups. These epoxy groups permitted introduction of metal binding functionality to produce the cellulose‐g‐GMA‐imidazole final product. Following characterization, a series of adsorption studies were carried out on the cellulose‐g‐GMA‐imidazole to assess its capacity in the removal of Cu²⁺ ions from solution. Cellulose‐g‐GMA‐imidazole sorbent showed an uptake of ～70 mg g^?1 of copper from aqueous solution. The adsorption process is best described by the Langmuir model of adsorption, and the thermodynamics of the process suggest that the binding process is mildly exothermic. The kinetics of the adsorption process indicated that copper uptake occurred within 30 min and that pseudo‐second‐order kinetics best describe the overall process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 2006     

Application of poly 3‐methylthiophene for removal of silver ion from aqueous solutions

This article deals with application of poly (3‐methyl thiophene) synthesized chemically on the surface of wood sawdust (termed as P3MTh/SD) and then was used for removal of silver ions (Ag⁺) from aqueous solution. The polymer was synthesized directly on the surface of sawdust, which has previously soaked in monomer solution using ferric chloride as chemical oxidant. The sorption experiments were performed on both batch and column systems under simple open circuit conditions. The effects of some important parameters such as pH, initial concentration, sorbent dosage, and exposure time on uptake of silver ion were investigated. The treatment of the data was also carried out using both Freundlich and Langmuir adsorption isotherms. To find out the possibility of the regeneration and reuse of the exhausted adsorbent, desorption studies were also performed. It was found that sawdust modified with polythiophene is an efficient system for uptake or recovery of the silver ions from aqueous solutions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cobalt(III) EDTA complex removal from aqueous alkaline borate solutions by nanofiltration

At the PWR Paks diluted low-level radioactive waste water (LLW) contains the long-lived ⁶⁰Co isotope in EDTA complex form, which has no simple separation procedure. In this research nanofiltration(NF) was studied for selective removal of the cobalt(III) EDTA complex from a drain waste water model solution, which contains mainly sodium borate at an alkaline pH. A suitable NF membrane was chosen to separate the cobalt complex from the borate solution. The NF experiments were performed at constant temperature (25°C) and pressure range 1-10 bar. The cobalt complex and the borate ion rejection (R) as well as the permeate flux of the membrane was investigated as a function of pH. The rejection of the cobalt(III) EDTA complex ion and especially the borate were strongly pH dependent. The rejection of the complex ion and the borate was increased at alkaline pH (at pH 8, R = 73%; at pH 11.5, R = 96% for the cobalt complex; at pH 8, R = 7%; at pH 11.5, R = 59% for borate). NF seems to be a suitable separation method for the removal of the Co(III) EDTA complex from nuclear power plant waste streams. The removal of the cobalt complex ion from an alkaline borate solution by NF is possible in two ways: at slightly alkaline pH by a two-step separation, or at a more alkaline pH (pH > 9.5) by a one-step separation.     

Production of hydroxyapatite-based adsorbent for the removal of cobalt ions from the aqueous solution

The aim of the current study was to recover and separate cobalt ions from multielement solution, using hydroxyapatite (HAp) and magnetic nanocomposite of HAp/Fe₃O₄ as adsorbents. Cobalt ion adsorption process was conducted batchwise within the temperature 25˗55°C, exposure duration 5˗120 min by applying a dose of 0.25–5 g/L as the adsorbent at pH 2 to 9.  Adsorbent characterization was performed using advanced spectroscopic techniques such as Fourier Transform Infrared Spectroscopy, Scanning electron microscopy, and Energy-dispersive X-ray spectroscopy. The maximum ionic adsorption efficiency using HAp was 90.48% against 94.72% in the case of the magnetic nanocomposite of HAp, under optimal conditions. Various isotherm models were used to evaluate the adsorption capacity and equilibrium coefficients for adsorption of the cobalt ions by the prepared adsorbents. The isotherm models data showed that the adsorption process is desirable by the adsorbents and by adding nanoparticles of Fe₃O₄ the adsorption capacity improves.     

Application of magnetic polyaniline nanocomposite for separation of uranyl ions from aqueous solutions

Polyaniline (PANI) was synthesized chemically, and then modified with magnetic iron oxide nanoparticles (Fe₃O₄ NPs). PANI and PANI-Fe₃O₄ NPs were used for removal of uranyl ions (UO₂²⁺) from aqueous solutions using a batch system. The synthesized adsorbents were characterized using FT-IR, SEM, BET and XRD techniques. From isotherm investigation, the maximum adsorption capacities (q_m) were 150.0 and 108.0 mg g^?1 for PANI and PANI-Fe₃O₄NPs, respectively. The kinetics and equilibrium adsorptions were well-described by the pseudo-second-order kinetic and Langmuir model, respectively. Thermodynamic studies depicted that the adsorption of uranyl ions by PANI is a spontaneous exothermic process and in the case of PANI-Fe₃O₄ NPs, adsorption process is endothermic; therefore, the spontaneity is controlled by entropy.