Adsorption of Pb2+ and Cd2+ onto a Novel Activated Carbon‐Chitosan Complex

A novel activated carbon‐chitosan complex adsorbent (ACCA) was prepared via the crosslinking of glutaraldehyde and activated carbon‐(NH₂‐protected) chitosan complex under microwave irradiation. The surface morphology of this adsorbent was characterized. The adsorption of ACCA for Pb²⁺ and Cd²⁺ was investigated. The results demonstrate that ACCA has higher adsorption capacity than chitosan. The adsorption follows pseudo first‐order kinetics. The isotherm adsorption equilibria are better described by Freundlich and Dubinin‐Radushkevich isotherms than by the Langmuir isotherm. The adsorbent can be recycled. These results have important implications for the design of low‐cost and effective adsorbents in the removal of heavy metal ions from wastewaters.     

Effects of Acylation and Crosslinking on the Material Properties and Cadmium Ion Adsorption Capacity of Porous Chitosan Beads

Abstract

Chitosan is a novel glucosamine biopolymer derived from the shells of marine organisms. This biopolymer is very attractive for heavy metal ion separations from wastewater because it is selective for toxic transition metal ions over less toxic alkali or alkane earth metal ions. Highly porous, 3-mm chitosan beads were prepared by an aqueous phase-inversion technique for casting gel beads followed by freeze drying. In the attempt to simultaneously improve material properties and adsorption capacity, chitosan was chemically modified by 1) homogeneous acylation of amine groups with nonanoyl chloride before bead casting, and 2) heterogeneous crosslinking of linear chitosan chains with the bifunctional reagent glutaric dialdehyde (GA) after bead casting but before freeze drying. The random addition of C₈ hydrocarbon side chains to about 7% of the amine groups on uncrosslinked chitosan beads via N-acylation improved the saturation adsorption capacity from 169 to 216 mg Cd²⁺/g-bead at saturation (pH 6.5, 25°C) but only slightly reduced solubility in acid solution. Crosslinking of the N-acylated chitosan beads with 0.125 to 2.5 wt% GA in the crosslinking bath increased the internal surface area from 40 to 224 m²/g and rendered the beads insoluble in 1 M acetic acid (pH 2.36). However, crosslinking of the N-acylated chitosan beads reduced the saturation adsorption capacity to 136 mg Cd²⁺/g-bead at 0.75 wt% GA and 86 mg Cd²⁺/g-bead at 2.5 wt% GA. Crosslinking also significantly reduced the compression strength. There was no clear relationship between internal surface area and adsorption capacity, suggesting that the adsorbed cadmium was not uniformly loaded into the bead.     

Novel type of alginate gel‐based adsorbents for heavy metal removal

Various alginate gel‐based adsorbents were investigated for the removal of heavy metals: alginate beads, alginate capsules, and alginate gel‐coated adsorbent. Of these, alginate capsules showed the greatest Pb²⁺ uptake capacity of 1560 mg g^?1 of dry sodium alginate, and the alginate gel‐coated adsorbent, prepared simply by forming a thin alginate film on an inert matrix, achieved rapid adsorption equilibrium within 10 min. Adsorbed metals were readily removed from the alginate gel‐based adsorbents using eluents such as HNO₃ and could be reused for up to 10 adsorption–desorption cycles without marked loss of metal uptake capacity. Alginate gel‐coated adsorbents could be prepared in a dried state and have great application potential for the removal of heavy metals from contaminated water. Copyright © 2004 Society of Chemical Industry     

Metal recovery using immobilized cell suspension from a brewery

Lead, copper, and cadmium were adsorbed onto calcium alginate beads containing the cell suspension discarded from a brewery. In the cell suspension, there were many cells under lysis. The cell-suspension immobilized beads were prepared by adding 0.6% (w/v) sodium alginate into the cell suspension from the brewery and then making the cell suspension fall dropwise into the swirling 1% (w/v) calcium alginate solution. The dry weight of insoluble solid in the cell suspension was 96 g dry weight/l and the dry density of the bead containing cell suspension was 140 g dry weight/l of the bead. The specific metal uptake of the cell-suspension immobilized bead was 23.7 mg Pb²⁺, 14.3 mg Cu²⁺, and 13.4 mg Cd²⁺/g bead dry weight, respectively. The cell-suspension immobilized beads retained the initial metal-uptake capacity after 20 repeated batches of adsorption and desorption, but the fraction of metal desorbed from the beads by 1 M HCl solution was only 70% of the adsorbed metal. The beads, which had been contained for 14 successive days in the 0.5% (w/v) CaCl₂ solution at 4 °C just after 20 cycles of adsorption/desorption, retained the initial metal-uptake capacity after 30 repeated cycles, and more than 90% of the copper and cadmium adsorbed on the beads was desorbed by the 1 M HCl solution.     

Adsorption of lanthanum by magnetic alginate‐chitosan gel beads

BACKGROUND: The risk of environmental pollution is aggravated by the increasing application of considerable amounts of rare earth elements in advanced materials. This paper reports the preparation of novel magnetic alginate–chitosan gel beads and their application for adsorption of lanthanum ions from aqueous solution. RESULTS: Stable magnetic alginate–chitosan gel beads with average diameter 0.85 ± 0.05 mm were prepared by loading iron oxide nanoparticles onto a combined alginate and chitosan absorbent. The performance of the prepared beads for the adsorption of lanthanum ions from aqueous solution was tested. It was found that various parameters, such as aqueous pH, contact time, metal ion concentration, ion strength and temperature, have an effect on the adsorption. Adsorption equilibrium was reached in 10 h and the maximum uptake capacity was 97.1 mg g^?1. From the analysis of pH, FTIR and XPS data, it is proposed that lanthanum adsorption proceeds through mechanisms of cation exchange, electrostatic interaction and surface complexation, with the oxygen atoms the main binding sites. In addition, lanthanum ions could be selectively separated from coexisting base metal ions such as Pb (II), Cd (II), Co (II), Ni (II) and Cu (II) in the aqueous solution. CONCLUSION: The prepared magnetic alginate–chitosan gel beads exhibit high uptake capacity and selectivity for lanthanum sorption, and thus can be used for adsorptive recovery of lanthanum from aqueous solutions. Copyright © 2010 Society of Chemical Industry     

A low-cost and environment friendly chitosan/aluminum hydroxide bead adsorbent for fluoride removal from aqueous solutions

A novel low-cost adsorbent named chitosan/Al(OH)₃·(CS/Al(OH)₃) bead was successfully prepared by employing AlCl₃·6H₂O aqueous solution as the solvent for CS. The CS/Al(OH)₃ beads were used for fluoride removal from water. The beads were synthesized using the chitosan and aluminum chloride with the mass ratio of 2:1 as the precursor and in situ generation of aluminum hydroxide sorbents in sodium hydroxide solution. Then, the beads were washed with distilled water to neutral and freeze dried. The sorbents were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), Fourier transform infrared spectrometry (FTIR), and X-ray diffractometry (XRD), respectively. Batch adsorption experiments were conducted to evaluate the parameters that affected the defluoridation capacity. The influencing parameters including pH, co-existing ions in water and initial temperature of the adsorption process were studied. The influence of temperature confirmed that the adsorption was spontaneous and endothermic. The adsorption isotherm of fluoride followed Langmuir isotherm model and the sorption kinetics was more suitable for pseudo-second-order kinetic model. The defluoridation capacity of chitosan/Al(OH)₃ calculated using Langmuir model was 23.06 mg/g (293 K, pH 4). The experimental results showed that the CS/Al(OH)₃ bead adsorbent is promising for the fluoride adsorption.     

Adsorption equilibrium of copper ion and phenol by powdered activated carbon, alginate bead and alginate-activated carbon bead

The adsorption equilibrium characteristics for single and binary components of copper ion and phenol onto powdered activated carbon, alginate bead and alginate-activated carbon (AAC) bead were studied. Adsorption equilibrium data of phenol and copper ion onto the adsorbents could be represented by Langmuir equation. The adsorption capacity of Cu²⁺ onto different adsorbents was in the following order: alginate bead > AAC bead > powdered activated carbon (PAC). On the other hand, that of phenol was: PAC > AAC bead > alginate bead. Multi-component equilibrium data were correlated by three different models. Among them the ideal adsorbed solution theory (IAST) gave the best fit to our data. And the adsorption amount of Cu²⁺ onto AAC bead was greater than that of phenol in the binary components.     

Alanine containing porous beads for mercury removal from artificial solutions

N‐methacryloyl‐(L )‐alanine (MALA) was synthesized by using methacryloyl chloride and alanine as a metal‐complexing ligand or comonomer. Spherical beads with an average diameter of 150–200 μm were obtained by suspension polymerization of MALA and 2‐hydroxyethyl methacrylate (HEMA) conducted in an aqueous dispersion medium. Poly(HEMA–MALA) beads were characterized by SEM, swelling studies, surface area measurement, and elemental analysis. Poly(HEMA–MALA) beads have a specific surface area of 68.5 m²/g. Poly(HEMA–MALA) beads with a swelling ratio of 63%, and containing 247 μmol MALA/g were used in the removal of Hg²⁺ from aqueous solutions. Adsorption equilibrium was achieved in about 60 min. The adsorption of Hg²⁺ ions onto PHEMA beads was negligible (0.3 mg/g). The MALA incorporation into the polymer structure significantly increased the mercury adsorption capacity (168 mg/g). Adsorption capacity of MALA containing beads increased significantly with pH. The adsorption of Hg²⁺ ions increased with increasing pH and reached a plateau value at around pH 5.0. Competitive heavy metal adsorption from aqueous solutions containing Cd²⁺, Cu²⁺, Pb²⁺, and Hg²⁺ was also investigated. The adsorption capacities are 44.5 mg/g for Hg²⁺, 6.4 mg/g for Cd²⁺, 2.9 mg/g for Pb²⁺, and 2.0 mg/g for Cu²⁺ ions. These results may be considered as an indication of higher specificity of the poly(HEMA–MALA) beads for the Hg²⁺ comparing to other ions. Consecutive adsorption and elution operations showed the feasibility of repeated use for poly(HEMA–MALA) chelating beads. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1222–1228, 2006     

Preparation and adsorption properties of metal ions of crosslinked chitosan azacrown ethers

The novel azacrown ether chitosan derivatives (CCAE‐I, CCAE‐II) were prepared by reaction between crosslinked chitosan with epoxy‐activated azacrown ethers. Their structures were confirmed by elemental FTIR spectra analysis and X‐ray diffraction analysis. The adsorption and selectivity properties of the crosslinked chitosan azacrown ethers for Pb²⁺, Cu²⁺, Cr³⁺, Cd²⁺, and Hg²⁺ were also investigated. The experimental results showed that they have high adsorption capacity for Cu²⁺, Cd²⁺, and Hg²⁺. The adsorption capacity of CCAE‐II is higher than CCAE‐I for Cd²⁺ and Hg²⁺. The selectivity properties of CCAE are better than chitosan and crosslinked chitosan. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3053–3058, 1999     

Microwave preparation and adsorption properties of EDTA‐modified cross‐linked chitosan

A novel chitosan‐based adsorbent (CCTE) was synthesized by the reaction between epichlorohydrin O‐cross‐linked chitosan and EDTA dianhydride under microwave irradiation (MW). The chemical structure of this new polymer was characterized by infrared spectra analysis, thermogravimetric analysis, and X‐ray diffraction analysis. The results were in agreement with the expectations. The static adsorption properties of the polymer for Pb²⁺, Cu²⁺, Cd²⁺, Ni²⁺, and Co²⁺ were investigated. Experimental results demonstrated that the CCTE had higher adsorption capacity for the same metal ion than the parent chitosan and cross‐linked chitosan. In particular, the adsorption capacities for Pb²⁺ and Cd²⁺ were 1.28 mmol/g and 1.29 mmol/g, respectively, in contrast to only 0.372 mmol/g for Pb²⁺ and 0.503 mmol/g for Cd²⁺ on chitosan. Kinetic experiments indicated that the adsorption of CCTE for the above metal ions achieved the equilibrium within 4 h. The desorption efficiencies of the metal ions on CCTE were over 93%. Therefore, CCTE is an effective adsorbent for the removal and recovery of heavy metal ions from industrial waste solutions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterization of the structure and diffusion behavior of calcium alginate gel beads

A simple and novel method using gel shrinkage to indirectly characterize the structure of calcium alginate gel (CAG) beads during the calcium alginate gelation process was presented in this study. The effect of preparation process parameters (gelling cations, bead diameter, and alginate M _w and concentration) on the structure of the CAG bead formation process was thoroughly investigated. It was found that (a) the concentration of the Na⁺ and Ca²⁺ ion in gel bath was found to be the determining factor in the gel structure formation process by regulating the dissociation of alginate and the complexation of the calcium; (b) Na⁺ acts as a competitor with calcium and a screen in the electrostatic repulsion; (c) the effect of beads size below 700 μm on the structure of CAG beads can be neglected; and (d) the sodium alginate concentration has no significant effect on the gel formation process. Furthermore, the diffusion of bovine serum albumin (BSA) was controlled by the density of CAG bead. Consequently, a faster diffusion rate of BSA within the looser structure of beads can be observed. These results are keys to understanding the behavior and performance of beads in their utilization medium. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48923.     

Novel composite biopolymers of sodium alginate/natural rubber/coconut waste for adsorption of Pb(II) ions

A novel composite adsorbent in the form of beads for removal of Pb²⁺ from wastewater was prepared by blending a sodium alginate (NaAlg) solution, natural rubber (NR) latex, and coconut waste (cofiber). After being crosslinked by calcium chloride, the beads were highly stable, flexible, and easily used in the environment. The optimum composition of the beads with an average size of 1.1–1.2 mm was 4% NaAlg:NR latex (60% dry rubber content):cofiber at 50:1:0.72 and a 2%w/w CaCl₂ solution used for cross linking. The physico‐chemical properties of the beads were examined by the swelling ratio measurement, ATR‐FTIR, and SEM. The effects of the amount of cofiber, NR, and initial Pb²⁺ ions, the pH of the medium, the bead content, and the contact time, on the adsorption of Pb²⁺ were investigated. NR improved the water resistance and, hence, the stability of the beads. The cofiber increased the porosity and contact area and, hence, the efficiency of the composite beads to adsorb the Pb²⁺ up to 99.6%. The prepared beads are promising material to use for the effective and economical removal of Pb²⁺ from water. POLYM. COMPOS., 35:1013–1021, 2014. © 2013 Society of Plastics Engineers     

Importance of activated carbon's oxygen surface functional groups on elemental mercury adsorption

The effect of varying physical and chemical properties of activated carbons on adsorption of elemental mercury (Hg⁰) was studied by treating two activated carbons to modify their surface functional groups and pore structures. Heat treatment (1200 K) in nitrogen (N₂), air oxidation (693 K), and nitric acid (6N HNO₃) treatment of two activated carbons (BPL, WPL) were conducted to vary their surface oxygen functional groups. Adsorption experiments of Hg⁰ by the activated carbons were conducted using a fixed-bed reactor at a temperature of 398 K and under N₂ atmosphere. The pore structures of the samples were characterized by N₂ and carbon dioxide (CO₂) adsorption. Temperature-programmed desorption (TPD) and base-acid titration experiments were conducted to determine the chemical characteristics of the carbon samples. Characterization of the physical and chemical properties of activated carbons in relation to their Hg⁰ adsorption capacity provides important mechanistic information on Hg⁰ adsorption. Results suggest that oxygen surface complexes, possibly lactone and carbonyl groups, are the active sites for Hg⁰ capture. The carbons that have a lower carbon monoxide (CO)/CO₂ ratio and a low phenol group concentration tend to have a higher Hg⁰ adsorption capacity, suggesting that phenol groups may inhibit Hg⁰ adsorption. The high Hg⁰ adsorption capacity of a carbon sample is also found to be associated with a low ratio of the phenol/carbonyl groups. A possible Hg⁰ adsorption mechanism, which is likely to involve an electron transfer process during Hg⁰ adsorption in which the carbon surfaces may act as an electrode for Hg⁰ oxidation, is also discussed.     

Synthesis and heavy metal ion adsorptivity of macroreticular chelating resins containing phosphono and carboxylic acid groups

Macroreticular copolymer beads were prepared by suspension polymerization of 4-vinylbenzyl chloride (VBC), divinylbenzene (DVB) and monomers with carboxylic ester groups like dibutyl maleate (DBM), dibutyl fumarate (DBF) and dibutyl itaconate (DBI) in the presence of toluene as diluent. The copolymer beads were phosphorylated at the chloromethylated phenyl rings with triethyl phosphite and hydrolyzed by an aqueous sodium hydroxide solution; the hydrolysis on the bead surface converted carboxylic ester/phosphonate groups into carboxylic acid/phosphono groups, respectively. The investigations on the metal ion chelation characteristics of the H-form copolymer beads revealed that they have good adsorptivity toward heavy metal ions like Pb²⁺, Cd²⁺ and Cu²⁺, and poor adsorptivity toward ions like Hg²⁺ and UO₂²⁺. The adsorptivity caused by the three carboxylic ester monomer derivatives was in the order DBM > DBI > DBF. Especially, the Na-form copolymer beads neutralized by alkali treatment were very available for the adsorption of all the metal ions under investigation.     

Preparation and adsorption behavior of macrocyclic tetra‐amine derivatives of chitosan

The new macrocyclic polyamine derivatives of chitosan were synthesized by reacting epoxy‐activated macrocyclic tetra‐amine with the C6 hydroxyl or C2 amino group in chitosan. The obtained copolymers (CTS‐OM, CTS‐NM) contain amino functional groups, the secondary amines, and more polar hydroxyl groups in its skeleton. Elemental analysis, infrared spectra, and solid‐state ¹³C‐NMR analysis confirmed their structures. The adsorption behavior of the macrocyclic polyamine grafted chitosan for Ag⁺, Pb²⁺, Hg²⁺, and Cr³⁺ was investigated. The experimental results showed that the two novel derivatives of chitosan have high adsorption capacity and good selectivity for some metal ions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 407–412, 2005     

Preparation and adsorption behavior for metal ions of cyclic polyamine derivative of chitosan

The new macrocyclic polyamine derivatives of chitosan were synthesized by reacting epoxy‐activated macrocyclic tetra‐amine with C6 hydroxyl or C2 amino group in chitosan. The obtained copolymers contain amino functional groups in its skeleton and secondary amines, and more polar hydroxyl groups. Elemental analysis, infrared spectra, and solid‐state ¹³C NMR analysis confirmed their structures. The adsorption behavior of the macrocyclic polyamine grafted chitosan for Ag⁺, Pb²⁺, Hg²⁺, and Cr³⁺ were investigated. The experimental results showed that the two novel derivatives of chitosan have high adsorption capacity and good selectivity for some metal ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3018–3023, 2006     

Preparation of a surface molecular‐imprinted adsorbent for Ni2+ based on Penicillium chrysogenum

A new chitosan molecular‐imprinted adsorbent was prepared from the mycelium of waste biomass. The results showed that an adsorbent using Penicillium chrysogenum mycelium as the core material was better than one derived from peanut coat. The adsorption capacity of the surface‐imprinted adsorbent for Ni²⁺ was enhanced by increasing the chitosan concentration in the imprinting process. Epichlorohydrin was better than glutaraldehyde as a cross‐linking agent; the optimal imprinted Ni²⁺ concentration for preparing the surface‐imprinted adsorbent was 2 mg (Ni²⁺) g^?1 of mycelium. The adsorption capacity of the surface‐imprinted adsorbent was 42 mg g^?1 (at 200 mg dm^?3 initial metal ions concentration) and twice that of the mycelium adsorbent. The surface‐imprinted adsorbent can be reused for up to 15 cycles without loss of adsorption capacity. Copyright © 2005 Society of Chemical Industry     

Interaction of heavy metal ions with an ion exchange resin obtained from a natural polyelectrolyte

An ion exchange resin was synthesized by using a natural polyelectrolyte, sodium alginate, and barium ion as a cross-linker reagent. Resin was characterized by TGA and SEM. Equilibrium and kinetic experiments of Pb²⁺, Hg²⁺, Ni²⁺, Co²⁺, Fe²⁺, and Fe³⁺ ions uptake by barium alginate beads were carried out in batch-type experiments under different values of pH. The removal efficiency increases with increasing pH. The uptake of metal ions occurs rapidly in the first hour. Maximum retention capacity was also determined being Fe(II) > Fe(III) > Co(II) > Ni(II) > Pb(II) > Hg(II) in mmol/g dry beads basis. Elution from the loaded resins at maximum capacity was studied by using HCl and HNO₃ as eluents at different concentrations.     

Grafting of tea waste with polyacrylic acid and its potential applications

The indigenous materials such as tea waste were exploited as antimicrobial adsorbent for removing heavy metal ions. It was well known that tea waste was characterized with biodegradability and environmental-friendly product. Grafting copolymerization of acrylic acid onto tea waste was carried out using gamma radiation. The effects of solvent, dose and feeding concentration of acrylic acid have been investigated to achieve the optimum conditions. Grating (%) ranged from 30 to 70 for DMSO and H₂O, respectively. The grafted tea waste was characterized by Fourier transform infrared (FTIR) spectroscopy, swelling study, scanning electron microscopy (SEM) and energy dispersive spectrometry X-rays (EDS). The grafted samples were used in waste water treatment to remove heavy metal ions (Cr³⁺, Pb²⁺ and Hg²⁺). The highest adsorption capacity was 35 and 200 mg/g of Hg⁺² ions for ungrafted and grafted samples, respectively. The results showed that the selectivity among these metal ions is different onto tea waste-graft-polyacrylic acid. The grafted tea waste samples, which complexed with Cr³⁺, Pb²⁺ and Hg²⁺ ions, were found to have antimicrobial features. Therefore, they could be used as adsorbent in removing heavy metal ions with antimicrobial features as well.

     

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.