Baojiao Gao

Efficient removal of heavy metal ions from aqueous solution using salicylic acid type chelate adsorbent

In this study, 5-aminosalicylic acid was successfully grafted onto the poly(glycidyl methacrylate) (PGMA) macromolecular chains of PGMA/SiO(2) to obtain a novel adsorbent designated as ASA-PGMA/SiO(2). The adsorption properties of ASA-PGMA/SiO(2) for heavy metal ions were studied through batch and column methods. The experimental results showed that ASA-PGMA/SiO(2) possesses strong chelating adsorption ability for heavy metal ions, and its adsorption capacity for Cu(2+), Cd(2+), Zn(2+), and Pb(2+) reaches 0.42, 0.40, 0.35, and 0.31 mmol g(-1), respectively. In addition, pH has a great influence on the adsorption capacity in the studied pH range. The adsorption isotherm data greatly obey the Langmuir and Freundlich model. The desorption of metal ions from ASA-PGMA/SiO(2) is effective using 0.1 mol l(-1) of hydrochloric acid solution as eluent. Consecutive adsorption-desorption experiments showed that ASA-PGMA/SiO(2) could be reused almost without any loss in the adsorption capacity.

Adsorption property and mechanism of composite adsorbent PMAA/SiO2 for aniline

In this paper, functional monomer methacrylic acid (MAA) was grafted onto the surface of silica gel particles using 3-methacryloxypropyl trimethoxysilane (MPS) as intermedia, and grafting particles PMAA/SiO(2) were prepared. The adsorption properties and mechanism of PMAA/SiO(2) towards aniline were researched through batch and column adsorption methods. The experimental results showed that PMAA/SiO(2) possesses strong adsorption ability for aniline with interaction of hydrogen bond. The saturated adsorption amount could reach up to 140 mg g(-1). The empirical Langmuir isotherm was found to agree well with the equilibrium adsorption data. pH and temperature were found to have great influence on the adsorption amount. Finally, PMAA/SiO(2) was observed to possess excellent reusability properties as well.

Adsorption of 2,4,6-trinitrotoluene on a novel adsorption material PEI/SiO2.

In this paper, functional macromolecule polyethyleneimine (PEI) was grafted onto the surface of silica gel particles in order to produce the novel adsorption material, PEI/SiO2. Then this novel materials adsorption properties for TNT were investigated through static methods, and the experimental results showed that PEI/SiO2 possessed strong adsorption ability for TNT. In fact, the saturated adsorption amount could reach 14.47 mg g(-1). The empirical Freundlich isotherm was also found to describe well the equilibrium adsorption data. In addition, the pH and temperature were found to have great influence on the adsorption amount. Finally, PEI/SiO2 was observed to possess excellent reusability properties as well.

Adsorption and recognition characteristics of surface molecularly imprinted polymethacrylic acid/silica toward genistein.

In this paper, on the basis of surface-initiated graft polymerization, a new surface molecular imprinting technique is established by molecular design. And molecularly imprinted polymer MIP-PMAA/SiO2 is successfully prepared with genistein as template. The adsorption and recognition characteristics of MIP-PMAA/SiO2 for genistein are studied in depth by using static method, dynamic method and competitive adsorption experiment. The experimental results show that MIP-PMAA/SiO2 possesses very strong adsorption affinity and specific recognition for genistein. The saturated adsorption capacity could reach to 0.36mmolg(-1). The selectivity coefficients relative to quercetin and rutin are 5.4 and 11.8, respectively. Besides, MIP-PMAA/SiO2 is regenerated easily and exhibits excellent reusability.

Selective Epoxidation of Cyclohexene Catalyzed by New Bidentate Schiff Base Dioxomolybdenum(VI) Complex Immobilized on Crosslinked Polystyrene Microspheres

A new immobilized bidentate Schiff base dioxomolybdenum(VI) complex was prepared with chloromethlated crosslinked polystyrene (CMCPS) microspheres as starting carrier via two stepwise polymer reactions with p-hydroxybenzaldehyde and glycine as reagents, respectively, as well as a coordination reaction with MoO2(acac)2, and the immobilized dioxomolybdenum(VI) complex abbreviated to CPS-[MoO2(ALGL)2] (ALGL refers to the bidentate Schiff base ligand, which comes form aldehyde [AL] group and glycine [GL]) was used in the epoxidation reaction of cyclohexene with tert-butyl hydroperoxide (TBHP) as oxidant. In the epoxidation reaction of cyclohexene, this heterogeneous dioxomolybdenum(VI) complex catalyst has high catalytic activity and excellent catalytic selectivity.

Adsorption properties of polyvinyl-alcohol-grafted particles toward genistein driven by hydrogen-bond interaction.

The adsorption properties of polyvinyl alcohol (PVA)-grafted silica gel particles PVA/SiO2 toward genistein are researched in this paper. The effects of the main factors on the adsorption properties are investigated, the adsorption mechanism is explored in depth, and the adsorption thermodynamics is researched. The experimental results show that the conventional hydrogen bond is formed between the hydroxyl groups with high density on the surfaces of PVA/SiO2 and the phenolic hydroxyl groups in genistein, while π-type hydrogen bond is formed between the hydroxyl groups of PVA/SiO2 and the conjugated aromatic rings. It is the two types of hydrogen bond that make the functional composite particles PVA/SiO2 produce very strong physical adsorption toward genistein. The competitive adsorption of the solvent can have severe negative impact on the adsorption capacity of genistein. Increasing temperature will weaken the hydrogen-bond interaction between PVA/SiO2 particles and genistein. The existence of electrolytes in the protic solvent will affect the adsorption negatively. The adsorption process of PVA/SiO2 particles toward genistein is exothermic and driven by enthalpy. The adsorption isotherm data matches the Langmuir model.

Preparation of heparin-functionalized microspheres and study on their adsorption characteristic for basic protein lysozyme

In suspension polymerization system, poly(glycidyl methacrylate) (PGMA) microspheres are firstly prepared. Then, ring opening reaction takes place when heparin is bonded on PGMA microspheres to obtain functional PGMA-heparin microspheres. The chemical structure and physicochemical characters of PGMA-heparin microspheres are fully characterized with infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and zeta potential determination. The adsorption properties of PGMA-heparin for lysozyme are mainly investigated. The effects of the main factors on the adsorption properties are explored, furthermore the adsorption mechanism is analyzed in depth, and the adsorption thermodynamics is also researched. The experimental results show that the strong electrostatic interaction is formed between high density of negative charge coming from the carboxyl groups or sulfonic acid groups of heparin and the positive charge of basic protein lysozyme. The adsorption of PGMA-heparin for lysozyme is dependent on the pH value of the medium, and the saturated adsorption amount of PGMA-heparin for lysozyme possesses a maximum at pH 8, which reaches up to 654 mg/g. The adsorption of PGMA-heparin for lysozyme is an exothermic process which is driven by entropy, and the adsorption amount decreases with increasing the temperature.

Preparation and Characterization of Metronidazole-Surface Imprinted Microspheres MIP-PSSS/CPVA for Colon-Specific Drug Delivery System

In this paper, the use of molecular surface imprinted polymers (MIPs) in designing colon-specific drug delivery systems was investigated. MIPs were prepared on crosslinked polyvinyl alcohol microspheres (CPVA) with sodium 4-styrene sulfonate (SSS) as functional monomer, Metronidazole (MTZ) as template and N,N’-Methylene bisacrylamide (MBA) as crosslinking agent by utilizing cerium salt-hydroxyl group redox initiation system, obtaining MTZ molecular surface imprinted microspheres MIP-PSSS/CPVA. The MIP-PSSS/CPVA microspheres were further characterized by scanning electron microscope and batch binding method. Because there is strong electrostatic interactions between MTZ and monomer SSS, the MTZ molecular surface imprinting is quite successful, and the imprinted microspheres MIP-PSSS/CPVA possess high recognition selectivity and excellent combining affinity. The experimental results show that at pH 1, the MIP-PSSS/CPVA microspheres exhibit very strong binding ability for MTZ, and the binding capacity reaches up to 115 mg/g. The in vitro release of the MTZ-loaded MIP-PSSS/CPVA is highly pH-dependent and time-delayed. The release behavior shows that the drugs do not release in simulated gastric fluid (pH = 1), the drug release is small while in the simulated small intestinal fluid (pH = 6.8), an abrupt release will be firstly produced and then drug release is sustained and slowed in the simulated colon fluid (pH = 7.4), displaying excellent colon-specific drug delivery behavior.

Removal of Fe(II) from Ce(III) and Pr(III) rare earth solution using surface imprinted polymer

Abstract Rare earth solution is a very important strategic resource. But, impurities, such as Fe2+, have great influence on the optical properties of rare earth material. In this study, a novel Fe2+-ionic imprinted polyamine functionalized silica gel adsorbent was prepared by a surface imprinting technique for selective adsorption of Fe2+ from rare earth solution. The adsorption and recognition properties of IIP-PEI/SiO2 for Fe2+ were studied in detail. The experimental results showed that the IIP-PEI/SiO2 possessed strong adsorption affinity, specific recognition ability and excellent selectivity for Fe2+. The adsorption isotherm data greatly obey the Langmuir model, and the adsorption was typical monolayer. The adsorption capacity could reach up to 0.334 mmol g−1, and relative selectivity coefficients relative to Pr3+ and Ce3+ are 23.25 and 18.42, respectively. Besides, the IIP-PEI/SiO2 was regenerated easily using diluted hydrochloric acid solution, as eluent and IIP-PEI/SiO2 possess better reusability.

Preparation of Iminoacetic Acid-type Composite Chelating Material IAA-PEI/SiO2 and Preliminary Studies on Chelating Adsorption Property towards Heavy Metal Ions

Polyamine polyethyleneimine (PEI) was first grafted on the surfaces of micro-sized silica gel particles in the manner of the coupling graft (the manner of “grafting to”), forming the grafting particles PEI/SiO2. Subsequently, via a polymer reaction, the nucleophilic substitution reaction between the primary and secondary amino groups of the grafted PEI macromolecule and chloroactic acid (CAA), iminoacetic acid groups were bonded onto the grafted PEI chains, and an iminoacetic acid (IAA)-type composite chelating material, IAA-PEI/SiO2, was formed. In this work, the preparation process of IAA-PEI/SiO2 particles was mainly researched, and the effects of the main factors on the polymer reaction, i.e., the nucleophilic substitution reaction, were examined emphatically. The adsorption behavior of IAA-PEI/SiO2 particles towards several kinds of heavy metal ions was preliminarily evaluated. The experiments results show that it is feasible to introduce IAA groups onto PEI/SiO2 particles via the substitution reaction between CAA and the amino groups of the grafted PEI. The reaction rate is affected greatly by the feed ratio of the amino group of PEI to CAA, so the substitution reaction between CAA and the amino groups of the grafted PEI is a bimolecular nucleophilic substitution reaction (SN2). The reaction temperature and the used amount of acid-acceptor NaHCO3 affect the bonding rate of IAA groups greatly. The fitting temperature was 60°C, and 1:1 of the molar ratio of NaHCO3 to CAA was an appropriate amount of acid-acceptor NaHCO3. Under the above optimal reaction conditions and with 3:1 molar ratio of amino group of PEI to CAA, 72% of the IAA group bonding rate (it is based on the hydrogen atoms in the primary and secondary amino groups of the grafted PEI) in 8 h can be reached. The composite chelating material IAA-PEI/SiO2 possesses a strong chelating adsorption ability for heavy metal ions because of the increase of the ligands and formation of stable five-membered chelate rings.