Hybrid Properties of Alginate‐PEI Adsorbent for Chromium (VI) Removal from Aqueous Solutions

Abstract

An adsorbent consisting of polyethyleneimine (PEI) immobilized in calcium alginate gel beads was synthesized and evaluated for Cr⁶⁺ removal. An evaluation of the synthesis process showed the importance of the PEI molecular weight on the immobilization efficiency. Polyethyleneimine of 70,000 Da molecular weight displayed the highest immobilization percentage at 52%. Batch kinetics and equilibrium tests showed that alginate‐PEI (APEI) resin displayed considerable affinity for negatively charged Cr⁶⁺ complexes at low pH conditions ranging from pH 1.5‐pH 3. The results also indicated the reduction of Cr⁶⁺ to less toxic Cr³⁺ species by the APEI adsorbent. The column adsorption experiments showed the ability of APEI resin to treat a 10 mg/L Cr⁶⁺ solution with pH influent adjustment from pH 1.5 to pH 3 to concentrations that satisfy effluent standards for Cr⁶⁺ (<0.1 mg/L) and total Cr (<0.5 mg/L). Finally, comparisons with a highly aminated commercial resin Chitopearl CS‐03 highlighted the unique ability of the hybrid APEI beads with its amine and carboxylic groups for the adsorption of Cr⁶⁺ as well as the retention of generated Cr³⁺ ions.     

Synthesis of magnetic citric‐acid‐functionalized graphene oxide and its application in the removal of methylene blue from contaminated water

A magnetic nanocomposite of citric‐acid‐functionalized graphene oxide was prepared by an easy method. First, citric acid (CA) was covalently attached to acyl‐chloride‐functionalized graphene oxide (GO). Then, Fe₃O₄ magnetic nanoparticles (MNPs) were chemically deposited onto the resulting adsorbent. CA, as a good stabilizer for MNPs, was covalently attached to the GO; thus MNPs were adsorbed much more strongly to this framework and subsequent leaching decreased and less agglomeration occurred. The attachment of CA onto GO and the formation of the hybrid were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction spectrometry and transmission electron microscopy. The specific saturation magnetization of the magnetic CA‐grafted GO (GO‐CA‐Fe₃O₄) was 57.8 emu g^?1 and the average size of the nanoparticles was found to be 25 nm by transmission electron microscopy. The magnetic nanocomposite was employed as an adsorbent of methylene blue from contaminated water. The adsorption tests demonstrated that it took only 30 min to attain equilibrium. The adsorption capacity in the concentration range studied was 112 mg g^?1. The GO‐CA‐Fe₃O₄ nanocomposite was easily manipulated in an external magnetic field which eases the separation and leads to the removal of dyes. Thus the prepared nanocomposite has great potential in removing organic dyes. © 2014 Society of Chemical Industry     

Novel magnetic nanoparticles for the hydrolysis of starch with Bacillus licheniformis α‐amylase

Novel magnetic nanoparticles with an average size of 350–400 nm with N‐methacryloyl‐(L )‐phenylalanine (MAPA) as a hydrophobic monomer were prepared by the surfactant‐free emulsion polymerization of 2‐hydroxyethyl methacrylate, MAPA, and magnetite in an aqueous dispersion medium. MAPA was synthesized from methacryloyl chloride and L ‐phenylalanine methyl ester. The specific surface area of the nonporous magnetic nanoparticles was found to be 580 m²/g. Magnetic poly[2‐hydroxyethyl methacrylate–N‐methacryloyl‐(L )‐phenylalanine] nanoparticles were characterized by Fourier transform infrared spectroscopy, electron spin resonance, atomic force microscopy, and transmission electron microscopy. Elemental analysis of MAPA for nitrogen was estimated as 4.3 × 10^?3 mmol/g of nanoparticles. Then, magnetic nano‐poly[2‐hydroxyethyl methacrylate–N‐methacryloyl‐(L )‐phenylalanine] nanoparticles were used in the adsorption of Bacillus licheniformis α‐amylase in a batch system. With an optimized adsorption protocol, a very high loading of 705 mg of enzyme/g nanoparticles was obtained. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The inverse of enzyme affinity for free amylase (181.82 mg/mL) was higher than that for immobilized enzyme (81.97 mg/mL). Storage stability was found to increase with adsorption. It was observed that the enzyme could be repeatedly adsorbed and desorbed without a significant loss in the adsorption amount or enzyme activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Magnetic and K+-cross-linked kappa-carrageenan nanocomposite beads and adsorption of crystal violet

Biopolymer-based magnetic beads, composed of kappa-carrageenan (κ-Car) and Fe₃O₄ nanoparticles, were synthesized. The magnetic beads were prepared through in situ precipitation of Fe²⁺/Fe³⁺ ions in the presence of carrageenan and subsequently treating with K⁺ solution. The structure of magnetic kappa-carrageenan beads (mκ-Carb) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer, and thermal gravimetric analysis techniques. According to SEM micrographs, an undulant and coarse structure with cubic-shaped sections was obtained when the magnetic nanoparticles were incorporated in composition of beads. The TEM image confirmed the formation of magnetic nanoparticles with an average size of 3–7 nm. The synthesized beads were examined as adsorbent to remove crystal violet dye from aqueous solutions. It was found that due to coarse surface, the rate of dye adsorption on magnetic beads can be improved slightly. The experimental adsorption kinetics was analyzed according to pseudo-first-order and pseudo-second-order kinetic models and the adsorption kinetics followed well the pseudo-second-order model. Isotherm adsorption data of dye on beads were modeled according to Langmuir and Freundlich isotherm models. The results revealed that the experimental data have the best fit to Langmuir isotherm model, and maximum adsorption capacity of beads for dye obtained was 84.7 mg/g. The influence of pH on the variation of adsorption capacity of beads for crystal violet was not considerable. The thermodynamic parameters indicated that the adsorption of CV dye on beads is spontaneous.     

Removal of heavy metal ions from aqueous solutions by radiation‐induced chitosan/(acrylamidoglycolic acid‐co‐acrylic acid) magnetic nanopolymer

An effective method was developed to isolate toxic heavy metal ions from the aqueous solution by the magnetic nanopolymers. The magnetic sorbent was prepared with radiation‐induced crosslinking polymerization of chitosan (CS), 2‐acrylamido‐glycolic acid (AMGA), and acrylic acid (AAc), which stabilized by magnetite (Fe₃O₄) as nanoparticles. The formation of magnetic nanoparticles (MNPs) into the hydrogel networks was confirmed by Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, and Scanning electron microscopy, which revealed the formation of MNPs throughout the hydrogel networks. The swelling behavior of the hydrogels and magnetic ones was evaluated at different pH values. The adsorption activity for heavy metals such as Cu²⁺ and Co²⁺ by nonmagnetic and magnetic hydrogels, Fe₃O₄/CS/(AMGA‐co‐AAc), in terms of adsorption amount was studied. It was revealed that hydrogel networks with magnetic properties can effectively be used in the removal of heavy metal ions pollutants and provide advantageous over conventional ones. POLYM. ENG. SCI., 55:1441–1449, 2015. © 2015 Society of Plastics Engineers     

Preparation of thiourea functionalized polyvinyl alcohol‐coated magnetic nanoparticles and their application in Pb2+ ions adsorption

We have prepared a novel kind of magnetic nanoparticle with high adsorption capacity and good selectivity for Pb²⁺ ions by modifying the magnetic nanoparticles with polyvinyl alcohol (PVA) and thiourea. The resultant magnetic nanoparticles were used to adsorb Pb²⁺ ions from aqueous solution. The influence of the solution pH, the adsorption time, the adsorption temperature, coexisting ions, and the initial concentration of Pb²⁺ ions on the adsorption of Pb²⁺ ions were investigated. The results indicated that Pb²⁺ ions adsorption was an endothermic reaction, and adsorption equilibrium was achieved within 30 min. The optimal pH for the adsorption of Pb²⁺ ions was pH 5.5, and the maximum adsorption capacity of Pb²⁺ ions was found to be 220 mg/g. Moreover, the coexisting cations such as Ca²⁺, Co²⁺, and Ni²⁺ had little effect on adsorption of Pb²⁺ ions. The regeneration studies showed that thiourea functionalized PVA‐coated magnetic nanoparticles could be reused for the adsorption of Pb²⁺ ions from aqueous solutions over five cycles without remarkable change in the adsorption capacity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40777.     

Magnetic nanoparticles embedded in pectin‐based hydrogel for the sustained release of diclofenac sodium

A supermagnetic polysaccharide‐based nanocomposite gel has been developed as a potential drug delivery system. The gel was made via graft copolymerization of 2‐acrylamido‐2‐methylpropanesulfonic acid on pectin using ammonium peroxodisulfate as an initiator and N,N‐methylenebisacrylamide as a crosslinker under microwave irradiation. The magnetic nanoparticles (MNPs) were incorporated within the gel network via an in situ method of diffusion of Fe²⁺/Fe³⁺ followed by reduction with ammonia solution. The graft copolymer gel and its nanocomposite were characterized using attenuated total reflection Fourier transform infrared spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, field‐emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and transmission electron microscopy. The magnetic properties of the nanocomposite were measured using a vibrating sample magnetometer and mechanical properties using a tensile compressive tester. The gel was evaluated for adsorption and release of the drug diclofenac sodium. The presence of MNPs is observed to enhance significantly the mechanical properties, swelling capacity, drug loading and release ability of the graft polymer gel. The increased porosity of the gel network and higher surface area of MNPs allowed for 20% higher adsorption of diclofenac sodium molecules compared to the parent nonmagnetic gel. About 95% of the loaded drug was released from the MNP‐containing gel. The drug release pattern followed first‐order kinetic model and the Higuchi square root model, indicating swelling‐controlled diffusion to be the mode of drug release. © 2018 Society of Chemical Industry     

A simple sulfuric acid pretreatment method to improve the adsorption of Cr(VI) by chitosan

An optimum pH of 5.0 for the adsorption of Cr⁶⁺ by chitosan was determined by using a stirred‐batch reactor method at constant pH. When a column containing chitosan was used to bind Cr⁶⁺ in a situation where pH could not be held constant because of pH changes caused by the chitosan itself, significant binding occurred only at solution pH 1 and 2. When chitosan was pretreated with sulfuric acid in a range of 7–70 mol % sulfuric acid : moles glucosamine residue, maximum binding occurred at pH 6.0. Under these conditions, a column containing 0.500 g acid‐treated chitosan (35% mole ratio) reduced the concentration of Cr⁶⁺ in 713 bed volumes of 25 ppm Cr⁶⁺ solution to ≤5 ppm in the effluent. A similar column of pretreated chitosan reduced Cr⁶⁺ concentration in 1042 bed volumes of industrial chromium plating rinse water initially containing 18 ppm Cr⁶⁺ to ≤5 ppm. Capacity experiment results indicated 60 mg chromium bound per gram of treated chitosan at pH 6.0. Commercial resin IRA‐67 was also investigated as a Cr⁶⁺ binding agent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2808–2814, 2004     

Silica‐based iminodiacetic acid functionalized adsorbent for Ni hydrometallurgical extraction of nickeliferous laterite

A novel silica‐based iminodiacetic acid functionalized adsorbent was fabricated and then used to nickel hydrometallurgical extraction for low‐grade nickeliferous laterites. The surface morphology of the adsorbent was characterized by scanning electron microscopy. The adsorption experiment indicated a maximum nickel load capacity of about 0.45 mmol/g. Analysis of adsorption thermodynamic and kinetics revealed a spontaneous adsorption process driven by entropy increase, and limited by film diffusion. Semi‐industrial scale column experiments revealed that the Ni²⁺ in the acidic leach liquor of low‐grade nickeliferous laterites may be efficiently extracted by the iminodiacetic acid functionalized adsorbent, if the Fe³⁺ ions existing in the acidic leach liquor were previously reduced to be Fe²⁺ by sodium sulfite. This environmentally safe adsorbent may supplant the traditional solvent extraction process for low‐grade nickeliferous laterites. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Role of Ni2+ substituent on the structural,optical and magnetic properties of chromium oxide (Cr2-xNixO3) nanoparticles

Pristine chromium oxide (Cr₂O₃) and nickel ions (Ni²⁺) substituted Cr₂O₃ nanoparticles were synthesized using a simple co-precipitation technique. The main objective of this work is to investigate Ni²⁺ substituent's role at different concentrations on the structural, morphological, optical, and magnetic properties of Cr₂O₃ nanoparticles. Structural analyses based on X-ray diffraction (XRD), Raman and Fourier transform infra-red (FTIR) data confirmed the successful incorporation of Ni²⁺ into Cr₂O₃ nanoparticles up to x = 0.05 of Ni²⁺ content, without affecting the rhombohedral crystal structure of Cr₂O₃ nanoparticles. Rietveld refinement results showed the variation in lattice parameters and cell volumes alongwith the substitution of Ni²⁺ into Cr₂O₃ nanoparticles. Raman and FTIR spectra also depicted a considerable shift in the characteristic vibration modes of Cr₂O₃ nanoparticles due to strain-induced by Ni²⁺ substitution. Beyond x = 0.05, the structural transformation took place from rhombohedral to cubic crystal structure. Subsequently, new peaks (apart from Cr₂O₃ phase modes) have been observed at x = 0.1 of Ni²⁺ content due to the formation of secondary phase i.e., nickel chromate (NiCr₂O₄). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) illustrated the changes in the morphology of Cr₂O₃ nanoparticles with Ni²⁺ substitution. UV–Vis analysis revealed a narrowing of optical band energy (E_g) of Ni²⁺ substituted Cr₂O₃ nanoparticles from 3 to 1.85 eV as Ni²⁺ content varies from x = 0 to 0.2, respectively. Afterward, there is an increase in optical band gap energy (E_g) when Ni²⁺ content increased from x = 0.3 to 0.5, as NiCr₂O₄ started dominating the Cr₂O₃ phase. Single-phase Ni²⁺ substituted Cr₂O₃ nanoparticles exhibited a superparamagnetic behavior, whereas the multi-phase compound ascribed to both superparamagnetic and paramagnetic. These changes in optical and magnetic properties can lead to novel strategies to render applications in the field of optoelectronics and optomagnetic devices.     

Fabrication of zirconium-pillared montmorillonite porous ceramic as adsorbents for Cr3+ removal and recycling

A novel zirconium-pillared montmorillonite (Zr-Mt) porous ceramic (P-ZMt) for Cr³⁺ removal was developed by gelcasting. P-ZMt was characterized by XRD, SEM, XPS, TEM, BET. The influence of pH value, contact time, temperature and initial concentration on the adsorption efficiency was investigated. The results revealed that the P-ZMt has a high removal efficiency of Cr³⁺ over a broad range of pH value. The pseudo-second-order kinetic model fitted our acquired Cr³⁺ adsorption data best, in comparison with the pseudo-first-order kinetic model. The Langmuir model was applied to fit the adsorption process better than that of the Freundlich model. The thermodynamic parameters (∆H, ∆G and ∆S) were also determined, which revealed that the Cr³⁺ adsorption process was spontaneous in nature. The present developed P-ZMt could be recovered and reused for more than 6 times. The novel developed P-ZMt is an inexpensive, effective and long-life-cycle adsorbent for Cr³⁺ removal from water solution.     

Ultrabroadband mid-infrared emission from Cr2+-doped infrared transparent chalcogenide glass ceramics embedded with thermally grown ZnS nanorods

We report, for the first time to our knowledge, an ultrabroadband mid-infrared (MIR) emission in the range of 1800–2800 nm at room temperature from a Cr²⁺-doped chalcogenide glass ceramic embedded with pure hexagonal (wurtzite) β-ZnS nanorods and study the emission-dependent properties on the doping concentration of Cr²⁺. A new family of chalcogenide glasses based on (100 − x) Ge_1.5As₂S_6.5 – x ZnSe (in mol.%) was prepared by melt-quenching method. The Cr²⁺: β-ZnS nanorods of ˜150 nm in diameter and ˜1 μm in length were grown in the Cr²⁺-doped glass after thermal annealing. The compositional variations of glass structures and optical properties were studied. The crystalline phase, morphology of the thermally grown nanorods, and the microscopic elemental distributions were characterized using advanced nanoscale transmission electron microscopy analyses.     

Thermally and magnetically dual‐responsive mesoporous silica nanospheres: preparation,characterization, and properties for the controlled release of sophoridine

Novel thermally and magnetically dual‐responsive mesoporous silica nanoparticles [magnetic mesoporous silica nanospheres (M‐MSNs)–poly(N‐isopropyl acrylamide) (PNIPAAm)] were developed with magnetic iron oxide (Fe₃O₄) nanoparticles as the core, mesoporous silica nanoparticles as the sandwiched layer, and thermally responsive polymers (PNIPAAm) as the outer shell. M‐MSN–PNIPAAm was initially used to control the release of sophoridine. The characteristics of M‐MSN–PNIPAAm were investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetry, N₂ adsorption–desorption isotherms, and vibrating specimen magnetometry analyses. The results indicate that the Fe₃O₄ nanoparticles were incorporated into the M‐MSNs, and PNIPAAm was grafted onto the surface of the M‐MSNs via precipitation polymerization. The obtained M‐MSN–PNIPAAm possessed superparamagnetic characteristics with a high surface area (292.44 m²/g), large pore volume (0.246 mL/g), and large mesoporous pore size (2.18 nm). Sophoridine was used as a drug model to investigate the loading and release properties at different temperatures. The results demonstrate that the PNIPAAm layers on the surface of M‐MSN–PNIPAAm effectively regulated the uptake and release of sophoridine. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40477.     

Self‐assembly of alginate/polyethyleneimine multilayer onto magnetic microspheres as an effective adsorbent for removal of anionic dyes

A novel magnetic adsorbent alginate/polyethyleneimine (ALG/PEI)_n/MN was developed for removal of anionic dyes from aqueous solution in this study. (ALG/PEI)_n/MN was prepared by depositing ALG/PEI multi‐layers onto amine‐modified Fe₃O₄ microspheres through layer‐by‐layer method. The morphologies and structures of the adsorbent were characterized by scanning electron microscopy, X‐ray diffractometer, and Fourier transform infrared spectrometer, respectively, and its performance in adsorption of anionic dye (acid orange 10, AO10) under varied experimental conditions were also investigated. The results revealed that the uptake capacity of AO10 by (ALG/PEI)_n/MN increased with the number of coated (ALG/PEI) bilayer on the adsorbents, and the maximum adsorption capacity for AO10 by (ALG/PEI)₄MN was 246.3 mg g^?1 at 25 °C. The adsorption process was exothermic and well described by the pseudo‐second order kinetic model and the Langmuir isothermal model. Moreover, (ALG/PEI)₄/MN showed good reusability and excellent magnetic separability. All the results demonstrate that (ALG/PEI)₄/MN is a potential recyclable adsorbent for removal of anionic dyes from wastewater. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45876.     

In situ preparation of magnetic Fe3O4.Cu2O.Fe3O4/cryogel nanocomposite powder via a reduction–coprecipitation method as adsorbent for methylene blue water pollutant

Magnetic nanocomposites have attracted great attention as adsorbents for the removal of water pollutants, which respond to an external magnet that is used to remove both pollutants and composite nanomaterial traces from water. They are environmentally friendly and effective adsorbents for water treatment. In this respect, a simple in situ preparation method was used to prepare cryogel powder composite based on Fe₃O₄.Cu₂O.Fe₃O₄ nanomaterials. The ionic cryogel based on 2‐acrylamido‐2‐methylpropane sulfonate sodium salt and styrene sulfonate sodium salt was prepared by crosslinking polymerization at low temperature. The new magnetic nanoparticles based on Fe₃O₄.Cu₂O.Fe₃O₄ were successfully prepared inside the cryogel networks by a simple reduction–coprecipitation method based on reaction of Fe³⁺ with sodium sulfite and Cu²⁺ in the presence of hydroxylamine and ammonia solution. The thermal stability, accurate Fe₃O₄.Cu₂O.Fe₃O₄ content, magnetic properties, crystal lattice structure, particle sizes and morphology of the prepared cryogel composite were evaluated. The optimum conditions such as pH, contact time, adsorbate concentrations, adsorption equilibrium and adsorption kinetics were investigated to determine the efficiency of the prepared composite as an adsorbent to remove toxic methylene blue (MB) pollutant from aqueous solution. The data for MB adsorption confirmed the high ability of the prepared composite to remove more than 4.696 mmol L^?1 of MB from water during 6 min. The regeneration and reuse experiments showed excellent data for the synthesized new dye as an effective adsorbent for water treatment. © 2018 Society of Chemical Industry     

NIR-I/III afterglow induced by energy transfers between Er and Cr codoped in ZGGO nanoparticles for potential bioimaging

Herein, Cr³⁺ and Er³⁺ codoped zinc gallogermanate (ZGGO) nanoparticles with average size of ~60 nm was synthesized via a hydrothermal path. It was found that near infrared (NIR)-III (~1540 nm) afterglow was realized in ZGGO:Cr³⁺,Er³⁺ nanoparticles based on the successive energy transfer (ET) from Cr³⁺ to Er³⁺ after the stoppage of low-dose (60 mSv) X-ray irradiation. Meanwhile, the upconverted afterglow at 696 nm was produced via the ET from Er³⁺ to Cr³⁺ under different NIR light (808, 980, and 1532 nm) irradiations. Our results demonstrated that an X-ray pre-irradiation and a subsequent 980-nm light re-excitation might be a good strategy for realizing potential bioimaging. In particular, local-tissue NIR-I afterglow imaging using Cr³⁺ and Er³⁺ codoped ZGGO nanoparticles can be easily acquired by one-step 980-nm laser radiation. Furthermore, NIR-I/III afterglow mechanisms of ZGGO:Cr³⁺,Er³⁺ nanoparticles after stopping X-ray or different NIR lights (808, 980, and 1532 nm) irradiations were given.     

Cr(III)‐containing Fe3O4/mercaptopropanoic acid‐poly(2‐hydroxyethyl acrylate) nanocomposite: Highly active magnetic catalyst for direct hydroxylation of benzene

In this study, polymer‐grafted magnetic nanoparticles containing chromium(III) ions incorporated onto Fe₃O₄/mercaptopropanoic acid‐poly(2‐hydroxyethyl acrylate) was prepared via a simple and in situ method. The obtained magnetic nanocomposite exhibited high catalytic activity and excellent selectivity in direct hydroxylation of benzene in the presence of hydrogen peroxide under solvent‐free condition. The magnetic catalyst could be also separated by an external magnet and reused seven times without any significant loss of activity/selectivity. Due to the Lewis acidity of the Fe³⁺ groups in the structure of magnetic nanoparticles, the high efficiency of this catalyst is possibly due to the synergetic effect of Cr³⁺ and Fe³⁺ groups in the structure of magnetic nanocomposite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40383.     

Removal of Lead Ions from Aqueous Solutions by Different Types of Industrial Waste Materials: Equilibrium and Kinetic Studies

Abstract

A comparative study of the adsorbents prepared from several industrial wastes for the removal of Pb²⁺ has been carried out. Fertilizer industry waste viz. carbon slurry and steel plant wastes viz. blast furnace (B.F.) slag, dust, and sludge were investigated as low‐cost adsorbents after proper treatment in the present study. The adsorption of Pb²⁺ on different adsorbents has been found in the order: B.F. sludge>B.F. dust>B.F. slag>carbonaceous adsorbent. The least adsorption of Pb²⁺ on carbonaceous adsorbent even having high porosity and consequently greater surface area as compared to other three adsorbents, indicates that surface area and porosity are not important factors for Pb²⁺ removal from aqueous solutions. The adsorption of Pb²⁺ has been studied as a function of contact time, concentration, and temperature. The adsorption has been found to be exothermic, and the data conform to the Langmuir equation. The kinetic results reveal that the present adsorption system follows Lagergren's first order rate equation. Since all three waste products from the steel industry show higher potential to remove lead from water, therefore, it is suggested that these metallurgical wastes can be fruitfully employed as low‐cost adsorbents for effluent treatment containing toxic metal ions.     

Removal of Cd2+ ions from aqueous solution using cassava starch–based superabsorbent polymers

A comprehensive feasibility study on the adsorption of Cd²⁺ ions by cassava starch–based superabsorbent polymers (CST‐SAPs) as the biosorbent was investigated as a function of adsorbent dosage, pH, initial concentration, contact time, and temperature. An orthogonal experiment and range analysis were applied to optimize the adsorption conditions. Adsorbent dosage and initial concentration were the most sensitive variables for adsorption capacity. The maximum adsorption value of Cd²⁺ ions was determined as 347.46 mg/g at pH 6.0, initial concentration of 200 mg/L, and contact temperature and time of 323 K and 6 h, respectively, with 0.1 g adsorbent dosage. The equilibrium data were well described by a Langmuir model, and the adsorption process was well fitted by pseudo‐second‐order kinetics. The Fourier transform infrared spectroscopy (FTIR) data confirmed that acrylic acid and acrylic amide grafted onto the cassava starch. The X‐ray diffraction and FTIR results for the Cd²⁺‐absorbed CST‐SAP (CST‐SAP‐Cd²⁺) samples showed that the CST‐SAP could effectively adsorb Cd²⁺ ions and that the characteristic groups were translocated by chelation. The scanning electron microscopy results for the CST‐SAP revealed that the surface of the polymer was rough, and the layered structure that was full of folds caused an enhanced specific surface; such conditions were beneficial to Cd²⁺ ion adsorption. It was concluded that the CST‐SAP was an excellent adsorbent for Cd²⁺ ion removal from aqueous solution. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44758.     

Fabrication and Characterization of Glass‐Ceramic Fiber‐Containing Cr3 + ‐Doped ZnAl2O4 Nanocrystals

Glass‐ceramic fibers containing Cr³⁺‐doped ZnAl₂O₄ nanocrystals were fabricated by the melt‐in‐tube method and successive heat treatment. The obtained fibers were characterized by electro‐probe micro‐analyzer, X‐ray diffraction, Raman spectrum and high‐resolution transmission electron microscopy. In our process, fibers were precursor at the drawing temperature where the fiber core glass was melted while the clad was softened. No obvious element interdiffusion between the core and the clad section or crystallization was observed in precursor fiber. After heat treatment, ZnAl₂O₄ nanocrystals with diameters ranging from 1.0 to 6.3 nm were precipitated in the fiber core. In comparison to precursor fiber, the glass‐ceramic fiber exhibits broadband emission from Cr³⁺ when excited at 532 nm, making Cr³⁺‐doped glass‐ceramic fiber a promising material for broadband tunable fiber laser. Furthermore, the melt‐in‐tube method demonstrated here may open a new gate toward the fabrication of novel glass‐ceramic fibers.