ABSTRACT
An effective palladium nanocatalyst (Fe3O4@SiO2-FPBA-DTPA-Pd) was proposed and prepared, which was immobilized on magnetic silica with ethylenediamine pentaacetic acid and formylphenylboronic acid as biligands. A series of characterizations showed that Fe3O4@SiO2-FPBA-DTPA-Pd was 5-15 nm and contained 1.44 mmol/g Pd2+/Pd0. It was stable below 232.7 °C, and its saturation magnetization value was 21.17 emu/g which was easily recycled by a magnet. Its catalytic ability was evaluated through 7 Suzuki reactions and 15 Heck reactions. Results showed that the yields of 14 reactions catalyzed by Fe3O4@SiO2-FPBA-DTPA-Pd were more than 90%, while were better than those of the other two immobilized Pd catalysts on a single diethyltriamine pentaacetic acid (DTPA) group or boronic acid group. Moreover, Fe3O4@SiO2-FPBA-DTPA-Pd showed good reusability in both Suzuki and Heck reactions. In two model Suzuki and Heck reactions, after seven cycles, its yields were still above 95% without significant loss, which exceeded those of many reported catalysts; therefore, it has great potential in future large-scale industrial production.
ABSTRACT
A water-soluble negative sulfonic propyl ether ß-CD polymer (SPE-ß-CDP) to be used as chiral selector in capillary electrophoresis (CE) was polymerized. The sulfonic substitution degree of each ß-CD in SPE-ß-CDP was statistically homogenized. The only one negative peak in electrophoretogram with indirect ultraviolate method proved its uniformity of electrophoretic behavior. There were 7.12 sulfonic substitution in ß-CD unit and 164 µmole ß-CD units in each gram of SPE-ß-CDP, which corresponded a molecular weight of 7000 or more. Compared with monomer, SPE-ß-CDP was lower effect on electrical current of CE, indicating a high concentration of SPE-ß-CDP could be added. Its separation ability was verified by 12 chiral drugs. SPE-ß-CDP also showed advantages of good water solubility, easy preparation and recovery to reduce the overall cost. However, five of 12 chiral drugs were hardly to be fully separated which was normal for any kind of chiral selector. A newly adjustable gravity mediated capillary electrophoresis (AGM-CE) technology was proposed and combined with SPE-ß-CDP to enhance the chiral separation efficiencies of propranolol, salbutamol, omeprazole, ofloxacin and phenoxybenzamine which were markedly improved to 3.02, 1.17, 7.63, 4.14, and 2.81, respectively. Furthermore, its gradient mode (AGMg-CE) was also used to improve resolution through utilizing the zero mobility point, at which the effective apparent mobility of one racemate was zero. Resolutions of five chiral drugs were significantly improved, especially resolution of carvedilol changed from 0.43 to 1.0. These indicated SPE-ß-CDP as chiral selector, AGM-CE and AGMg-CE as new CE technologies had a great potential in chiral separation.
Subject(s)
Electrophoresis, Capillary , Ethers , Stereoisomerism , Electrophoresis, Capillary/methods , Water , Hydrogen-Ion ConcentrationABSTRACT
Cr(vi) is a great threat to the ecological environment and human health, so it is urgent to remove Cr(vi) from the environment. In this study, a novel silica gel adsorbent SiO2-CHO-APBA containing phenylboronic acids and aldehyde groups was prepared, evaluated and applied for removing Cr(vi) from water and soil samples. The adsorption conditions including pH, adsorbent dosage, initial concentration of Cr(vi), temperature and time were optimized. Its ability in removing Cr(vi) was investigated and compared with three other common adsorbents, SiO2-NH2, SiO2-SH and SiO2-EDTA. Data showed SiO2-CHO-APBA had the highest adsorption capacity of 58.14 mg g-1 at pH 2 and could reach adsorption equilibrium in about 3 h. When 50 mg SiO2-CHO-APBA was added in 20 mL of 50 mg L-1 Cr(vi) solution, more than 97% of Cr(vi) was removed. A mechanism study revealed that a cooperative interaction of both the aldehyde and boronic acid groups is attributed to Cr(vi) removal. The reducing function was gradually weakened with the consumption of the aldehyde group, which was oxidized to a carboxyl group by Cr(vi). This SiO2-CHO-APBA adsorbent was successfully used for the removal of Cr(vi) from soil samples with satisfactory results which indicates a good potential in agriculture and other fields.
ABSTRACT
A novel boronic acid and carboxyl-modified glucose molecularly imprinted polymer were prepared through suspension polymerization, which is based on 1.0 mmol glucose as a template, 1.2 mmol methacrylamidophenylboronic acid, and 6.8 mmol methacrylic acids as monomers, 19 mmol ethyleneglycol dimethacrylate, and 1 mmol methylene-bis-acrylamide as crosslinkers. The prepared glucose-molecularly imprinted polymer had a particle size of 25-70 µm, and was thermally stable below 215°C, with a specific surface area of 174.82 m2/ g and average pore size of 9.48 nm. The best selectivity between glucose and fructose was 2.71 and the maximum adsorption capacity of glucose- molecularly imprinted polymer was up to 236.32 mg/ g which was consistent with the Langmuir adsorption model. The similar adsorption abilities in six successive runs and the good desorption rate (99.4%) verified glucose-molecularly imprinted polymer could be reused. It was successfully used for extracting glucose from cellulose hydrolysis. The adsorption amount of glucose was 2.61 mg/mL and selectivity between glucose and xylose reached 4.12. A newly established chromatography (glucose-molecularly imprinted polymer) mediated hollow fiber membrane method in time separated pure glucose from cellulose hydrolysates on a large scale, and purified glucose solution with a concentration of 3.84 mg/mL was obtained, which offered a feasible way for the industrial production of glucose from cellulose hydrolysates.
