Optimization of polyacrylonitrile-cysteine resin synthesis and its selective removal of Cu(Ⅱ) in aqueous solutions

Polyacrylonitrile beads(PAN) cysteine(CS) was synthesized from polyacrylonitrile beads(PAN) and cysteine(CS).The content of the functional group and the percentage conversion of the functional group of PAN-CS prepared under the optimum condition using response surface methodology(RSM) for the first attempt were 3.22 mmol/g and 35.78%.The structure was characterized by ET-IR and elemental analysis.The adsorption properties of the resin for Cu(Ⅱ) were investigated by batch and column experiments.Batch adsorption results suggested that PAN-CS had higher adsorption capability for Cu(Ⅱ)than other metal ions and maximum saturated adsorption capacity was 184.7 mg/g.The resin and its metal complexes were studied by FT-IR.Furthermore,the resin can be eluted easily using 1 mol/L HC1.PAN-CS can provide a potential application for selective removal of copper from waste solution.     

Fabrication of carboxymethyl chitosan–hemicellulose resin for adsorptive removal of heavy metals from wastewater

Carboxymethyl chitosan–hemicellulose resin(CMCH) was synthesized by thermal cross-linking process and characterized by FTIR, TGA, and SEM. Subsequently, the adsorption properties of CMCH toward Ni(Ⅱ),Cd(Ⅱ), Cu(Ⅱ), Hg(Ⅱ), Mn(Ⅶ) and Cr(Ⅵ) were evaluated. Various factors affecting the uptake behavior such as pH, temperature, contact time and the initial concentration of the metal ions were investigated.The results showed that all adsorption processes fit the pseudo-second-order model and Langmuir isotherm equation. Significantly, the regeneration experiments showed CMCH can be used as a potentially recyclable and effective adsorbent for the removal and recovery of metal ions from wastewater.     

Preparation of a novel chelating resin for the removal of Ni2+ from water

A new chelating resin DVB-MA-HDA modified with hydroxamic acid groups was prepared for the fast removal of Ni2＋ from water. SEM, BET, elemental analysis, FT-IR spectroscopy and XPS were used to characterize this new adsorbent. Batch adsorption experiment indicated that the equilibrium adsorption capacity of DVB-MA-HD for Ni2＋ was more than 130mg/g, and the adsorption isotherm can be well fitted by the Langmuir model. The adsorption kinetic curve indicates that more than 60% of the adsorption amount of Ni2＋ at equilibrium occurred within the initial 20 rain. 0.1 mol/L EDTA solution could desorb Ni2＋ from DVB-MA-HDA effectively.     

Synthesis of Polyacrylaminothiourea Chelating Fiber and Properties of Concentration and Separation of Trace Noble Metal Ions from Samples

A novel polyacrylaminothiourea chelating fiber was synthesized simply and rapidly from nitrilon (an acrylonitrile-based synthetic fiber), which was applied to preconcentrate and separate of trace amount of Au(Ⅲ）,Pt(Ⅳ）,Pd(Ⅳ） and Ir (Ⅳ） ions from solution of samples.The analyzed ions can be quantitatively concentrated by the fiber up to a flow rate of 20.0mL/min at pH2, and can also be desorbed with 15 mL of 4mol/L HCl 3% thiourea from the fiber column with recoveries of 96.5%-100%.The chelating fiber can be reused for ten times,the recoveries of these ions are still over 92%,and hundred to thousand times of excess of Fe(Ⅲ）,Al（Ⅲ）,Ca(Ⅱ），Mg（Ⅱ）,Ni(Ⅱ）,Mn（Ⅱ),Cu(Ⅱ），Zn(Ⅱ），and Cd(Ⅱ） cause no interference on the determination of the analyzed ions by inductively-coupled plasma atomic emission spectrometry (ICP-AES).The static saturation adsorption capacities of the fiber for the analytes are in the range of 1.15-2.80mmol/g.The relative standard deviations for the determination of 20.0ng/mL each of Au(Ⅲ）,Pt(Ⅳ）,Pd(Ⅳ）and Ir(Ⅳ） are in the range of 0.7%-3.0%.The recoveries for test from standard additions to real solution samples are between 96% and 100%.The concentration of each ion in powder sample detected by the method is in good agreement with the certified value.     

An Ion-imprinted Silica Gel Polymer Prepared by Surface Imprinting Technique Combined with Aqueous Solution Polymerization for Selective Adsorption of Ni(Ⅱ) from Aqueous Solution

A novel Ni(Ⅱ) ion-imprinted silica gel polymer was prepared via the surface imprinting technique combined with aqueous solution polymerization by using 2-acrylamido-2-methyl-1-propanesulfonic acid(AMPS) as a functional monomer for the selective separation of Ni(Ⅱ) from aqueous solution. The sorbent showed good chemical and thermal stability. Kinetics studies indicated that the equilibrium adsorption was achieved within 10 min and the adsorption kinetics fitted well with the pseudo-second-order kinetic model. The maximum adsorption capacity of the ion-imprinted polymer towards Ni(Ⅱ) at the optimal p H of 7.0 was 66.22 mg·g~(-1). The relative selectivity coefficients of the sorbent were 9.23, 15.71, 14.72 and 20.15 for Ni(Ⅱ)/Co(Ⅱ), Ni(Ⅱ)/Cu(Ⅱ), Ni(Ⅱ)/Zn(Ⅱ) and Ni(Ⅱ)/Pb(Ⅱ), respectively. The adsorption isotherm fitted well with Langmuir isotherm model. The thermodynamic results indicated that the adsorption of Ni(Ⅱ) was a spontaneous and endothermic process. The sorbent showed good reusability evidenced by six cycles of adsorption/desorption experiments. The precision of this method is satisfactory. Thus, the prepared sorbent can be considered as a promising sorbent for selective separation of Ni(Ⅱ) in real water samples.     

A novel fluorescent epoxy resin for organophosphate pesticide detection

In this work,a novel bisbenzimidazolylpyridine-functionalized fluorescent epoxy resin was synthesized for organophosphate pesticide detection.The epoxy resin was characterized by Fourier-transform infrared spectroscopy(FT-IR),proton nuclear magnetic resonance spectroscopy(~1H NMR),gel permeation chromatography(CPC),differential scanning calorimetry(DSC) and fluorescence spectroscopy.After loading with Eu(Ⅲ) ions,the epoxy resin showed a strong fluorescence emission.The fluorescence emission was observed to be instantaneously quenched when exposed to trace amount of diethyl chlorophosphate in solution.The Stern-Volmer quenching constants K_(sv) for quenching at617 nm was determined to be 0.377 × 10~3 L/mol.This sensitive emission-quenching function and easy processing nature of the polymeric support enable the resin to be a promising chemosensor candidate for the detection of organophosphates.     

Two-dimensional correlation analysis of continuous online in situ ATR-FTIR on the adsorption of butyl xanthate at the surface of α-PbO

The adsorption behavior of butyl xanthate on the surface of lead oxide was investigated using continuous online in situ attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy technique and two dimensional(2D) correlation analysis.The adsorbed layer studied was prepared by coating α-PbO particles onto the surfaces of the ZnSe crystal.The appearance of spectral peaks at 1203 cm~(-1),1033 cm~(-1) and their red shift indicated the formation and aggregation of xanthate at the surface of α-PbO.According to 1R intensity changes after rinsing with deionized water and a NaOH solution,the adsorption was proved to be a chemisorption type.The competition between xanthate and OH for the surfaces leads to desorption of xanthate at higher pH.The technique of 2D correlation ATR-FTIR spectroscopy was used to evaluate the changing order of spectral intensities in the adsorption process,and the results indicated that xanthate micelles were formed at the surfaces.The adsorption kinetics of butyl xanthate was found to be a pseudo-second-order reaction model and the adsorption capacity of butyl xanthate at α-PbO was as high as 281 mg g~(-1) after 150 min.     

Synthesis of the water-compatible p-acetaminophen resin and its adsorption performances for vanillin in aqueous solution

A novel p-acetaminophen resin(named as GQ-1) was synthesized with chloromethylated polystyrene and p-acetaminophen.It can be used without any wetting process.The objective of this work was to study the adsorption performances for vanillin onto GQ-1 with two kinds of the hydrogen bond site of acetamino group and hydroxyl group.The results showed that the adsorption property of vanillin onto GQ-1 was superior to XAD-4,H103,NDA150,and NDA88.The adsorption capacity of vanillin onto GQ-1 is not greatly discrepant until the solution pH is higher than 5.31.The saturated adsorption quantity of vanillin was up to 141.32 mg/mL(wet resin) according to the dynamic adsorption and desorption experiments at 293 K.The resin could be regenerated by 7 BV ethanol.     

Removal of Cd（ Ⅱ ） from Aqueous Solutions by Natural Freshwater Surface Coatings

Natural freshwater surface coatings (biofilms and associated minerals), which were developed in the Nanhu Lake, Changchun, P. R. China, were used as an efficient biosorbent for the removal of Cd(Ⅱ) from aqueous solutions. The batch experiments were carried out to determine the adsorption properties of Cd(Ⅱ) onto the natural surface coatings. The classical Langmuir adsorption isotherm was applied to estimating the equilibrium coefficients of Cd(Ⅱ) adsorbed on the surface coatings. The results show that the maximum adsorption capacity of the surface coatings is 434. 78μmol Cd/m^2 (being equal to 0. 17mmol Cd/g of surface coatings or 10. 38mmol Cd/g Fe) and the Cd(Ⅱ) remnoval from solution media by the natural surface coatings was shown to be strongly affected by solution pH and ion strength. The resulted information also indicates that the maximum Cd removal efficiency(CRE) was determined to be approximately 90% at initial Cd mass concentration of 0. 1mg/L (the concentration limit of Cd (Ⅱ) in wastewaters for discharge in aquatic media in Chinese legislation), and the kinetic adsorption of Cd (Ⅱ) onto the surface coatings is fast with around 70% of the total adsorption-taking place in 150min in solution under the controlied laboratory conditions (mineral salts solution with defined speciation, ionic strength 0. 05mol/L, and 25℃). With the advantage of high Cd adsorption capacity, the natural surface coatings appear to be a potentially effective biosorbent for the removal and recovery of Cd(Ⅱ) from polluted water.     

Removal of Cd(Ⅱ) from Aqueous Solutions by Natural Freshwater Surface Coatings

Natural freshwater surface coatings(biofilms and associated minerals), which were developed in the Nanhu Lake, Changchun, P. R. China, were used as an efficient biosorbent for the removal of Cd(Ⅱ) from aqueous solutions. The batch experiments were carried out to determine the adsorption properties of Cd(Ⅱ) onto the natural surface coatings. The classical Langmuir adsorption isotherm was applied to estimating the equilibrium coefficients of Cd(Ⅱ) adsorbed on the surface coatings. The results show that the maximum adsorption capacity of the surface coatings is 434.78 μmol Cd/m2(being equal to 0.17 mmol Cd/g of surface coatings or 10.38 mmol Cd/g Fe) and the Cd(Ⅱ) removal from solution media by the natural surface coatings was shown to be strongly affected by solution pH and ion strength. The resulted information also indicates that the maximum Cd removal efficiency(CRE) was determined to be approximately 90% at initial Cd mass concentration of 0.1 mg/L(the concentration limit of Cd (Ⅱ) in wastewaters for discharge in aquatic media in Chinese legislation), and the kinetic adsorption of Cd(Ⅱ) onto the surface coatings is fast with around 70% of the total adsorption-taking place in 150 min in solution under the controlled laboratory conditions (mineral salts solution with defined speciation, ionic strength 0.05 mol/L, and 25 ℃). With the advantage of high Cd adsorption capacity, the natural surface coatings appear to be a potentially effective biosorbent for the removal and recovery of Cd (Ⅱ) from polluted water.     

Adsorption behavior of uranium on polyvinyl alcohol-g-amidoxime: Physicochemical properties, kinetic and thermodynamic aspects

Amidoxime-based adsorbents are widely studied as the main adsorbent in the recovery of uranium from seawater.However,the adsorption rate and loading capacity of such adsorbents should be further improved due to the economic viability consideration.In this paper,polyvinyl alcohol functionalized with amidoxime(PVA-g-AO)has been prepared as a new adsorbent for uranium(Ⅵ)adsorption from aqueous solution.The physicochemical properties of PVA-g-AO were investigated using infrared spectroscopy(IR),scanning electron microscope(SEM),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).Results showed that the ligand monomers were successfully grafted onto the matrixes.The XRD and XPS analysis showed that uranium was adsorbed in metal ionic form rather than in crystal form.Uranyl(U(Ⅵ))adsorption properties onto PVA-g-AO were evaluated.The adsorption of U(Ⅵ)by PVA-g-AO was fast,with an equilibrium time of less than 50 min.Additionally the maximum adsorption capacity reached 42.84 mg/g at pH 4.0.     

Controlled drug release studies of atenolol using differently sulfonated acryloxyacetophenone and methyl methacrylate copolymer resins as drug carriers

2-Acryloxyacetophenone(AAP) was prepared and subjected to suspension polymerization with methyl methacrylate(MMA) using azobisisobutyronitrile(AIBN) as free radical initiator.The differently sulfonated AAP-MMA cross-linked copolymer cationic exchange resins were prepared by sulfonation with concentrated sulphuric acid at 70 °C.Several characteristics of the prepared resins were evaluated,i.e.FTIR,the ion-exchange capacity(IEC),thermo gravimetric analysis(TGA),particle size distribution and microscopic morphology.The resin characteristics were altered with degree of sulfonation,providing that differently sulfonated resins could be prepared.The behavior of atenolol(ATL) loading and in vitro release in the USP stimulated gastric and intestinal fluids of the obtained resins were evaluated.The drug loaded in the resin increased with increasing degree of sulfonation and hence the drug binding site in resin employed.The drug release was lower from the resins with higher content of sulfonic group due to the increase in the diffusive path depth.The drug release was a little lower in stimulated gastric fluid(SGF) than in stimulated intestinal fluids(SIF).The basic groups,ionized to a little greater extent in SGF and preferred binding with the resin rather than releasing.Hence,the differently sulfonated resins could be utilized as novel carriers for drug delivery.     

Synthesis and Characterization of Pr（DPM）3 Served as Precursor for MOCVD

Praseodymium β-diketone chelate, Pr(DPM)3 [DPM=2,2,6,6-tetramethyl-3,5-heptanedionato], was successfully synthesized from the inorganic salt praseodymium chloride and HDPM(2,2,6,6-tetramethyl-3,5-heptane-dione) in an ethanol/aqueous solution followed distillation at low pressure and recrystallization from toluene. The physical and thermal properties of the chelate, including volatility, stability, and thermal decomposition, were investigated by elemental analyses, 1H NMR spectroscopy, XRD, TG/DTG/DTA analysis, infrared spectroscopy, and mass spectroscopy. The chelate with high purity prepared by thes of this study also shows sufficient volatility and stability in inert gases, which could be used as the precursor for metal-organic chemical vapor deposition(MOCVD).     

Highly Efficient Co-removal of Heavy Metals in Wastewater from Chemical Oxygen Demand Testing Instrument by Cysteine-functionalized Magnetic Nanoparticles

Wastewater discharged from chemical oxygen demand（COD） testing instrument was generally difficult to treat due to its high content of heavy metals and very low pH. In this study, a kind of cysteine-functionalized magnetic nanoparticles（MNPs-Cys） was synthesized and used to treat the wastewater. The synthesized MNPs-Cys as the adsorbent for heavy metal removal from aqueous solutions were systematically investigated. The adsorption dynamic process fit the Langmuir isotherms well with a maximum adsorption capacity of 76.92 mg/g for Cu（Ⅱ）. The adsorbent could be easily regenerated by 0.1 mol/L HNO3, which exhibited a high adsorption performance within 10 cycles. This adsorbent, combined with a developed pretreatment approach, could make Cr（Ⅲ）, Hg（Ⅱ） and Ag（Ⅰ） in the wastewater discharged from COD testing instrument effectively removed and the removal efficiency is more than 99%. This work gave a new insight into the design and synthesis of high-performance materials for treating wastewater with heavy metals.     

Kinetics and Thermodynamics of the Adsorption of Copper(Ⅱ) onto a New Fe-Si Adsorbent

A new kind of Fe-Si adsorbent was synthesized by iron oxide and diatomite after calcining and hydrothermal process. The influences of the initial Cu2+ concentration, p H and adsorption time on the Cu2+ removal efficiency were discussed. Three adsorption empirical kinetics equations and two thermodynamics equations were used to simulate the adsorption process. The microstructures of newly developed copper removal materials and properties of copper removal are characterized in details by SEM and EDS. Adsorption mechanism of the adsorbent was discussed. The suitable p H value for Cu2+ removal is 5.0 to 6.0 and the adsorption capacity increases with increasing the initial Cu2+ concentration. The adsorption kinetics of the adsorbent could be better described by pseudo second order kinetic model, whereas the adsorption isotherms highly conform to the Freundlich equation. The main crystalline phase of the adsorbent is Fe(Si O3) which can build porous structures conducive to the Cu2+ adsorption.     

Crosslinked chitosan nanofiber mats fabricated by one-step electrospinning and ion-imprinting methods for metal ions adsorption

The Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats were fabricated by one-step electrospinning and ion-imprinting methods and their application as adsorbents for metal ions was also investigated.The resulting chitosan nanofiber mats were characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and thermal gravimetric analysis(TGA).The Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats were used as adsorbents for the removal of Pb(Ⅱ)ions from aqueous or acid solutions.The effects of p H values,contact time,content of crosslinker(glutaraldehyde)on Pb(Ⅱ)ions adsorption were studied.The results indicated that the Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats had the highest adsorption capacity of 110.0 mg/g at p H 7.The kinetic study demonstrated that the adsorption of Pb(Ⅱ)ions followed the pseudo-second-order model.The equilibrium isotherm data showed that the Langmuir model was the most suitable for predicting the adsorption isotherm of the studied system.The Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats had good adsorption selectivity,which illustrates the equilibrium adsorption capacity in the order of Pb(Ⅱ)Cu(Ⅱ)Zn(Ⅱ)Cd(Ⅱ)Ni(Ⅱ).The Pb(Ⅱ)ion-imprinting electrospun crosslinked chitosan nanofiber mats were stable and had good reuse ability.     

STUDIES ON GRAFT COPOLYMERIZATION OF DL—LACTIDE ON CORN STARCH AND BIODEGRADABILITY OF THE COPOLYMERS

The starch/D,L-lactide graft copolymers were synthesized by reacting D,L-lactide with corn starch in N,N-dimethylacetamide(DMAM)in the presence of triethylamine(NEt3)and anhydrous lithium chloride.The effect of reaction time and the molar ratio of D,L-lactide to glucose structural unit of starch on monomer conversion(C%),graft(G%)and graft efficiency(GE%)were studied,The C%,G%and GE% could approach 37.3% 179.7%and 68.0%,respectively when the molar ratio of D,L-lactide to glucose structuralunit of starch is 10:1 and the graft copolymerization was carried out at 80-85℃ for 4hr under nitrogen atmosphere.The Fourier transforms infra-red (FTIR) spectroscopy.differential scanning calorimetry(DSC)and X_ray diffraction (XRD) spectroscopy were used in order to characterize the graft copolymers.FTIR spectra show that absorption band at 1740cm^-1 confirmed the formation of ester bond,indicating the starch /D,L-lactide graft copolymers were produced,the DSC characteristic results show the melting temperature of the graft copolymer were elevated slightly as the molar ratio of D,L-lactide to glucose structural units of starch increased and the X-ray diffraction spectra show the synthesized graft copolymers were amorphous.The degradability of graft copolymer was tested with the aid of acid,alkali and microbe such as bacillus subtilis and staphylococcus aureus.The results of water rsistance show the graft copolymer produced can be used as a component of impermeable coating for cardboard.     

Solid-phase extraction of Zn(II), Cu(II), Ni(II) and Pb(II) on poly(vinyl chloride) modified with 3-ferrocenyl-3-hydroxydithioacrylic acid, and their subsequent determination by electrothermal atomic absorption spectrometry

A new chelating resin based on poly(vinyl chloride) functionalized with 3-ferrocenyl-3-hydroxydithioacrylic acid has been synthesized and characterized. The resin was used as a packing material in an off-line mini-column solid-phase extraction system for preconcentration of Zn, Ni, Cu and Pb in water samples prior to their determination using electrothermal atomic absorption spectrometry. Analytical parameters such as pH, flow rate and sample breakthrough volume were optimized. The breakthrough volume for 0.2 μg of analyte using 0.1 g of adsorbent was 60–100 mL, permitting enrichment factors of at least 60. The proposed procedure, validated using a riverine water reference material (SLRS-3), was applied to environmental water samples. The potential for use of the chelating resin to separate interfering ions such as Na, K, Mg and Ca is also explored. Correspondence: Jackson K. Kiptoo, Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya     

Study on the Structures and Properties of Copper Removal Adsorbent Prepared from Sinter-free Pulverized Oyster Shell Materials

A hollow tubular copper removal adsorbent was prepared with oyster shell and cement as the main raw materials. The effects of different formulas, different initial copper concentrations and different pH values of samples on the copper removal efficiency were investigated to determine the optimal conditions for copper removal. The content of copper in the wastewater is determined by Atomic Absorption Spectrophotometer. The microstructure and elemental composition of the samples were characterized by scanning electron microscopy(SEM) and EDS. As a result, the formula with the content of cement to be 8 wt% and the oyster shell powder of 92 wt% is optimal. Under the condition of 30 ℃, when the pH value was 9.0, the Cu2+ adsorption capacity of the sample could reach 0.59 mg/g at 48 h. SEM analysis revealed that there are abundant pores in the sample, which is beneficial for Cu2+ absorption on the adsorbent.     

Preparation of magnetic anion exchange resin and their adsorption kinetic behavior of reactive blue

Magnetic anion exchange resin(MD-1) was prepared from quaternization of magnetic copolymeric resin(glycidyl methacrylate -eo-divinylbenzene).For comparison,magnetic resin MD-0 without quaternization and non-magnetic resin(D-1) were also synthesized for the adsorption process.It was found that the adsorption was mainly contributed to the chemical interaction between quaternary ammonium groups and reactive blue RXHC.Due to the smaller size,MD-1 had faster adsorption and desorption kinetics than D-1.Coupled with the advantage of easy separation,the magnetic anion exchange resin was considered to be superior to common anion exchange resin in removal of reactive dye.