Adsorption of humic acid onto pillared bentonite

Pillared bentonite, a clean and cost-effective adsorbent with high specific areas of 111.3 m²/g and high basalspacing of 1.98 nm, was prepared for the removal of humic acid from water. It is effective for the removal of humic acid with a high adsorption capacity of 537 mg/g, and adsorption is favored under acid conditions. Adsorption is dependent on ionic strength and dissolved NaCl enhanced adsorption. Over 97% removal was observed under natural pH conditions from humic acid solutions containing 10 mg/L Ca²⁺ or Mg²⁺, which suggests that pillared bentonite can be an effective adsorbent for the removal of humic acid for drinking water purification. Pillared bentonite can be regenerated with NaOH, and the regeneration efficiency reaches 83% and 85% when the concentration of NaOH reaches 0.025 and 0.05 mol/L. The mechanism for adsorption of humic acid to pillared bentonite is discussed.     

Adsorption mechanism of humic and fulvic acid onto Mg/Al layered double hydroxides

The adsorption of humic and fulvic acids onto nitrate, chloride and carbonate intercalated layered double hydroxides with Mg/Al ratios ranging from 85/15 to 60/40 was studied by adsorption isotherms at different ionic strengths and the characterization of the preferentially adsorbed humic substance size fractions. The adsorption of humic and fulvic acids onto LDHs occurred by ion exchange with both the intercalated and surface anions of the LDH and ligand exchange reactions with surface groups. The contribution of both mechanisms to the total HA and FA adsorption was estimated. Lower molecular weight humic and fulvic acids were preferentially adsorbed because these fractions can more easily enter the mesoporous LDHs and contain more carboxylic groups, which are known to be involved in ligand exchange reactions with e.g. surface Al-OH groups. Intercalation of the entire HA or FA molecules in-between the LDH sheets is unlikely to occur.     

Adsorption of indomethacin onto chemically modified chitosan beads

Macroporous chitosan beads used for the immobilization of an anti-inflammatory drug were prepared by the wet phase-inversion method. There are two stages of phase-inversion observed from the cast of chitosan droplet in tripolyphosphate (TPP) aqueous solution. The first stage of phase-inversion is dominated by liquid-liquid demixing and the morphology of the freeze-dried chitosan bead shows a bundle-like porous structure. The following stage of phase-inversion is attributed to the solid-liquid demixing and the morphology of the freeze-dried chitosan bead changes to an interconnected porous structure comprising particulates around the pores. The pore size and porosity of the bead can be varied by altering synthesis conditions, such as initial polymer concentration, and the pH value and concentration of the casting agent (TPP aqueous solution). Quaternary ammonium, and aliphatic and aromatic acyl groups were introduced into the porous chitosan beads to interact with an anti-inflammatory drug, indomethacin, through the electrostatic interaction and hydrophobic interaction. The results indicated that chemical modification of the porous chitosan beads have obvious effect on the adsorption of indomethacin.     

Adsorption of dyestuffs onto chitin. External mass transfer processes

The effect of several variables on the adsorption rate of four dyestuffs onto chitin was studied. A model is proposed enabling the film mass transfer coefficients to be determined. The coefficients were independent of initial dye concentration, chitin mass, chitin particle size, and temperature; a slight dependence with agitation was obtained. The film mass transfer coefficients at 400 rpm were 2.8×10^?3, 2.9×10^?3, 3.9×10^?3, and 0.9×10^?3 cm/s for Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 85, respectively.     

Adsorption characteristics of tannic acid onto the novel protonated palygorskite/chitosan resin microspheres

Novel protonated palygorskite/chitosan resin microspheres (p‐PCRM) were prepared and applied as adsorbents for the removal of tannic acid (TA) from aqueous solution. The effects of palygorskite (PAL) content, the initial pH value of the TA solution, and contact time and temperature on adsorption capacity of the microspheres were investigated. The adsorption process was found to be pH dependant with an optimum activity at pH 8.0. In comparison with protonated chitosan microspheres (224 mg g^?1), the p‐PCRM with 20 wt % PAL content exhibited higher adsorption capacity (455 mg g^?1) for TA at the same adsorption conditions. This may be attributed to the hydrogen bonding between adsorbents and adsorbates, and the porous structure formed by the introduction of PAL, which were confirmed by Fourier transform infrared and the pore parameters analysis. The study of adsorption kinetics and isotherms showed that the sorption processes were better fitted by pseudo‐second‐order equation and the Langmuir equation, respectively. Furthermore, the desorption study implied that the p‐PCRM were recyclable when 0.1M HCl was used as eluents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Graft copolymerization of itaconic acid onto chitin and its properties

Modification of chitin by grafting with itaconic acid (IA) was carried out using potassium persulfate as redox initiator. In complimentary experiments, grafting was performed using γ‐radiation. Grafting was confirmed by FTIR spectroscopy. The effect of monomer concentration, initiator concentration and copolymerization temperature on the percentage of grafting were studied. The effect of radiation dose was also investigated. Values for percentages of grafting of up to 300 % were reached. It was observed that the percentage of grafting increased with increasing monomer concentration and showed a tendency to level off at IA concentration of 0.1 mol l^?1. The percentage of grafting increased with temperature up to 60 °C and then decreased. The solubility of the grafted chitin was studied in organic and inorganic solvents. The complexation of the grafted chitin with some cations, namely copper, nickel, cobalt, zinc and lead, was also investigated. The metal uptake was measured by UV spectroscopy. Thermogravimetric analysis of the grafted chitin was also studied. Copyright © 2004 Society of Chemical Industry     

Adsorption of aluminium from wastewater by chitin and chitosan produced from silkworm chrysalides

Chitin, extracted from silkworm chrysalides, was employed for the production of a high‐purity and porous chitosan, as observed by scanning electron microscopy. Chitin and the chitosan produced from it were also analysed using ¹³C NMR spectroscopy to show the efficiency of deacetylation. The extracted chitin was investigated as an adsorbent material for aluminium removal from textile wastewater, by the column chromatographic method. After the treatment, the residual aluminium was lower than the limitation criterion of 0.2 mg L^?1. The isotherms of adsorption on chitin and chitosan surfaces were investigated and the best fits were observed using the Freundlich isotherm. At pH 5.0, the maximum adsorption capacity was 21.3 mg of aluminium per gram of chitosan over 70 h of experiments. Copyright © 2006 Society of Chemical Industry     

Graft-copolymerization of methylacrylic acid onto hydroxypropyl chitosan

Summary In order to study the graft modification of chitosan derivatives, hydroxypropyl chitosan (HPCTS) was prepared and characterized by FTIR, ¹H NMR, and elemental analysis Methylacrylic acid (MAA) was grafted onto HPCTS in an aqueous solution using ammonium persuffate (APS) as an initiator. Evidence of grafting was obtained by comparison of FTIR spectra of HPCTS and the grafted copolymer as well as solubility characteristics of the products. Variations of grafting percentage and grafting efficiency with reaction time, temperature, concentraton of initiator and monomer had been investigated. Received: 25 Febuary 2002/Revised version: 7 July 2002/Accepted: 12 July 2002     

Adsorption of reactive yellow 145 onto chitosan coated magnetite nanoparticles

Removal of dyes from the industrial discharge water is an important issue for safety of the environment. In this study, magnetic (magnetite, Fe₃O₄) nanoparticles were coated with chitosan (CS) and the efficiency of these chitosan coated magnetic nanoparticles (Fe₃O₄‐CS) for the adsorption of a reactive textile dye (Reactive Yellow 145, RY145) was examined first time in literature. TEM, XRD, and EPR results revealed that the thickness of the coat was about 2–5 nm, no phase change in the spinel structure of magnetic particles existed after coating, and particles had paramagnetic property, respectively. Adsorption of RY145 on Fe₃O₄‐CS nanoparticles occurs according to Langmuir model in the temperature range 25°C–45°C with a maximum adsorption capacity of 47.62 mg g^?1 at 25°C, in aqueous media. Thermodynamic parameters demonstrated that the adsorption process was endothermic and spontaneous, and the maximum desorption of the dye was 80% over a single adsorption/desorption cycle. In this study, the high efficiency of the CS coated magnetic nanoparticles in the adsorption and removal of reactive dyes from water was shown on model RY145. This type of nanoparticles can be good candidates in industrial applications for the decolorization of waste waters. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

甲壳素及壳聚糖的应用

介绍了甲壳素及壳聚糖的性质,概述了近年来甲壳素及壳聚糖在生物工程、化工环保、生物医学、食品工业等领域的应用进展。     

Adsorption behavior of cesium and strontium onto chitosan impregnated with ionic liquid

We briefly studied the adsorption behavior of chitosan impregnated with an ionic liquid (1-ethyl-3-methyl imidazolium chloride) in solutions with Cs⁺ and Sr²⁺ ions. The impregnation of chitosan was realized by ultrasonication method. The impregnated chitosan was analyzed by FTIR, SEM, and EDX in order to show that the chitosan was impregnated with the studied IL. The adsorptive properties of ionic liquid-impregnated chitosan for the removal of Cs⁺ and Sr²⁺ ions from aqueous solutions were studied in a batch adsorption system. The adsorption kinetic was found to follow a pseudo-second-order kinetic model. The experimental data showed good fit to the Langmuir isotherm. The adsorption properties of the chitosan impregnated with the studied ionic liquid were determined in binary, tertiary, and quaternary systems. The adsorption capacity of the IL impregnated chitosan is not significant influenced in the binary systems. The adsorption capacity of the IL impregnated chitosan decreases with the increase of the number of the cation present in solutions. It was observed that the studied adsorbent has a higher affinity for Cs⁺ ions than for Sr²⁺ ions.     

The sorption of acid dye onto chitosan nanoparticles

The behavior of chitosan nanoparticles as an adsorbent to remove Acid Green 27 (AG27), an acid dye, from an aqueous solution has been investigated with nanochitosan (particle size = 180 nm; degree of deacetylation = 74%). The dye concentration at equilibrium (Q_e, mg/g) was calculated using the weight of the nanoparticles in the mixed solution (Q_es) and the weight of chitosan in the nanoparticles (Q_ep). The experimental isotherm data were analyzed using the Langmuir equation for each chitosan sample; the Langmuir monolayer adsorption capacity (Q₀) was calculated with Q_es and Q_ep and the results were 1051.8 mg/g and 2103.6 mg/g, respectively, which were significantly higher than that of the micron-sized chitosan.     

Adsorption equilibria of reactive dye onto highly polyaminated porous chitosan beads

The adsorption of vinyl sulfone type reactive black 5 (RB 5) in aqueous solution onto chitosan beads and cross-linked chitosan beads with glutaraldehyde has been investigated in terms of initial pH and temperature of the solution. The adsorption equilibrium data were correlated with three adsorption models, such as Langmuir, Freundlich and Sips isotherms. Among them, the Freundlich isotherm best fit the data over the entire pH and temperature range of the solution. The adsorption capacity of RB 5 onto chitosan beads and cross-linked chitosan beads increased with decreasing initial pH and with increasing temperature. Equilibrium amount of RB 5 on chitosan beads was greater than that of cross-linked chitosan beads at the same initial pH values. Thermodynamic studies have also been carried out and values of standard free energy (°Gℴ), enthalpy (°Hℴ) and entropy (°Sℴ) were calculated.     

聚乙二胺改性壳聚糖微球吸附汞和铀

利用反相悬浮分散法制备壳聚糖微球,经聚乙二胺改性以提高氨基含量,考察了它对Hg2+和UO2+2的吸附性能.结果表明,吸附剂氨基含量6.52 mmol/g,粒径很小(＜10 μm),因此可快速吸附金属离子.pH＜3时可选择性分离Hg2+和UO2+2,对Hg2+和UO2+2的饱和吸附容量qm为2.20、1.41 mmol/g.动力学数据采用Lagergrent拟合,吸附速率常数kad(min-1)分别为Hg2+ 0.088,UO2+2 0.056.UO2+2和Hg2+可用1 mol/L H2SO4脱附,UO2+2还可用2 mol/L HCl脱附,脱附率＞90%.     

Adsorption characteristics of Reactive Black 5 onto chitosan beads cross-linked with epichlorohydrin

In this study, epichlorohydrin cross-linked chitosan beads were used for the removal of Reactive Black 5 (RB 5) from aqueous solution. The adsorption of RB 5 onto the cross-linked chitosan beads was strongly pH dependent. The adsorption capacity of RB 5 onto the cross-linked chitosan beads increased with increasing temperature, indicating the endothermic nature of the adsorption process. The thermodynamic parameters, namely the Gibbs free energy, enthalpy and entropy of the RB 5 adsorption process were calculated. The kinetic parameters were measured in a batch adsorber to analyze the rate of adsorption of RB 5 onto the cross-linked chitosan beads.     

Adsorption of Th(IV) onto Al-pillared rectorite: Effect of pH, ionic strength, temperature, soil humic acid and fulvic acid

The adsorption of Th(IV) onto Al-pillared rectorite as a function of rectorite concentration, Th concentration, pH, ionic strength, temperature, soil humic acid (HA) and fulvic acid (FA) was studied by using batch technique under ambient condition. The results indicated that the adsorption of Th(IV) onto Al-pillared rectorite strongly depended on pH and ionic strength, and the adsorption of Th(IV) increased with increasing Al-pillared rectorite concentration. The presence of HA/FA enhanced Th(IV) adsorption at low pH and reduced Th(IV) adsorption at high pH. The adsorption of Th(IV) decreased with increasing temperature, indicating that the adsorption process of Th(IV) onto Al-pillared rectorite was exothermic. The experimental data of Th(IV) adsorption were analyzed with the Freundlich and Langmuir models, showing that the Freundlich model fitted the adsorption data better than the Langmuir model. The adsorption of Th(IV) on Al-pillared rectorite may be dominated by surface complexation and cation exchange also contributed partly to Th(IV) adsorption.     

Chitin and chitosan nanofibers: electrospinning of chitin and deacetylation of chitin nanofibers

An electrospinning method was used to fabricate chitin nanofibous matrix for wound dressings. Chitin was depolymerized by gamma irradiation to improve its solubility. The electrospinning of chitin was performed with 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a spinning solvent. Morphology of as-spun and deacetylated chitin (chitosan) nanofibers was investigated by scanning electron microscopy. Although as-spun chitin nanofibers had the broad fiber diameter distribution, most of the fiber diameters are less than 100 nm. From the image analysis, they had an average diameter of 110 nm and their diameters ranged from 40 to 640 nm. For deacetylation, as-spun chitin nanofibous matrix was chemically treated with a 40% aqueous NaOH solution at 60 or 100 °C. With the deacetylation for 150 min at 100 °C or for 1day at 60 °C, chitin matrix was transformed into chitosan matrix with degree of deacetylation (DD) ∼85% without dimensional change (shrinkage). This structural transformation from chitin to chitosan was confirmed by FT-IR and WAXD.     

Adsorption of an acid dye onto coal fly ash

In this study, we found the raw coal fly ash (CFA) that had not been subjected to any pretreatment process had superior adsorbing ability for the anionic dye Acid Red 1 (AR1) than did two modified coal fly ashes (CFA-600 and CFA-NaOH). The adsorption capacities followed the order CFA > CFA-600 > CFA-NaOH, and they each increased upon increasing the temperature (60 °C > 45 °C > 30 °C). The adsorptions of AR1 onto CFA, CFA-600, and CFA-NaOH all followed pseudo-second-order kinetics. The isotherms for the adsorption of AR1 onto the raw and modified coal fly ashes fit the Langmuir isotherm quite well; the adsorption capacities of CFA, CFA-600, and CFA-NaOH for AR1 were 92.59–103.09, 32.79–52.63, and 12.66–25.12 mg g^?1, respectively. According to the positive values of ΔH° and ΔS°, these adsorptions were endothermic processes. The ARE and EABS error function methods provided the best parameters for the Langmuir isotherms and pseudo-second-order equations, respectively, in the AR1–CFA adsorption system.     

Adsorption of glucosinolates to metal oxides, clay minerals and humic acid

Glucosinolates are thioglucosides produced by plants belonging to the Capparales order. Glucosinolates can upon hydrolysis be transformed into a variety of bioactive compounds with a potential to serve as naturally produced pesticides. This paper presents results on the adsorption of prop-2-enyl and benzyl glucosinolate to two metal oxides (amorphous aluminium hydroxide and goethite), two clay minerals (kaolinite and montmorillonite) and to humic acid at different initial concentrations and at pH 4 and 8. The results show that the glucosinolates are weakly adsorbed to the variable-charge minerals with K_d ranging from 0.00 to 1.85 L kg^− 1 and that adsorption was higher at pH 4 than 8 indicating that adsorption takes place by electrostatic interactions between the negatively charged glucosinolates and positive sites on the minerals. On the humic acid higher K_d values were observed for prop-2-enyl glucosinolate (7.22 and 12.3 L kg^− 1), indicating that hydrophobic interactions may take place between the glucosinolate and humic acid. On the montmorillonite anion exclusion was observed as an effect of the negatively charged glucosinolates being repelled from the negatively charged montmorillonite surface. Thus glucosinolates will be very mobile in the soil environment with the potential of leaching to ground and surface waters where the toxic hydrolysis products may be formed.