Use of Poly(methyl methacrylate-co-methacrylic acid) Membranes in the Ultrafiltration of Aqueous Fe3+ Solutions by Complexing with Poly(vinyl pyrrolidone) and Dextran

Abstract

In this study water soluble complexible polymers, poly(vinyl pyrrolidone) (PVP) and dextran, were used for the ultrafiltration (UF) of aqueous Fe⁺³ solutions by using poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MA) membranes. Effects of polymer concentration and pH on the volume collected in the filtration of Fe⁺³ solutions and percent retentions (R%) were examined. It was determined that increase in polymer concentration decreased the permeability of PMMA-co-MA membrane and pH increased the retention of Fe³⁺ solutions. R% for Fe³⁺ solutions were obtained as 62% and 48% with PVP and dextran respectively at pH 3.0, for a filtration period of 80 minutes and retention for Fe³⁺ solution without using any complex forming polymer was found as 14%. Membranes were characterized by AFM analysis and contact angle measurements.     

Performance of C18 Derivatized Silica Gels: A Structure-Performance Study

Abstract

Significant performance differences in the separation of desamido-insulin from insulin and of amitriptyline from imipramine have been found for five, macroscopically similar, preparative C18 silica materials. Structure-performance relations have been used to understand this difference. Physical measurements on the unpacked silica gels as well as chromatographic measurements have been carried out. The latter measurements comprise: hydrophobicity, metal impurity, steric selectivity and silanol activity. The performance difference could not be explained by the difference in hydrophobicity, steric selectivity or metal impurity between the materials. Instead a correlation between the silanol ion exchange activity and the selectivity could be found. The highest performance was found under conditions where the silanol groups have a moderate activity. For the separations considered in this work, the silanol groups have a beneficial effect.     

Preparation of the Sulfonamide Containing Block Copolymer as Polymeric Sorbent for Removal of Mercury from Aqueous Solutions

A new sulfonamide containing polymeric sorbent for the removal of mercury ions from waste waters was prepared starting from poly(glycidyl methacrylate)-b-poly(ethylene glycol)-b-poly(glycidyl methacrylate) (PGMA- b -PEG- b -PGMA) triblock copolymer prepared by using the ATRP method. Epoxy groups on the block copolymer were functionalized with amino groups. Ammonia-functionalized PGMA- b -PEG- b -PGMA was treated with excess of benzenesulfonyl chloride to obtain a sulfonamide-based polymeric sorbent. The sulfonamide containing the polymeric sorbent with a 3.5 mmol · g^?1 total nitrogen content is able to selectively sorb mercury from aqueous solutions. The mercury sorption capacity of the resin is around 3.12 mmol g^?1 under non-buffered conditions. Experiments performed in identical conditions with several metal ions revealed that Cd(II), Pb(II), Zn(II), Fe(III), and Fe(II) also were extractable in quantities (0–0.45 mmol/g). The sorbed mercury can be eluted by repeated treatment with 4 M HNO₃ without hydrolysis of the sulfonamide groups.     

Preparation of Chelating Resins Containing a Pair of Neighboring Carboxylic Acid Groups and the Adsorption Characteristics for Heavy Metal Ions

Abstract

For the functional enhancement of chelating resins containing carboxylic acids, copolymer beads were prepared by suspension polymerization of styrene (St), methyl methacrylate (MMA), and divinylbenzene (DVB) in the presence of toluene as diluent. The phenyl rings of the beads were directly chloromethylated, and the carboxylic ester groups of the beads were converted into hydroxymethyl groups by reduction followed by chlorination to give chloromethyl groups, respectively. The chelating resins containing a pair of neighboring carboxylic acid groups (NCAGs) were obtained by the alkylation of chloromethyl groups in copolymer beads with diethyl malonate in the presence of sodium hydride followed by hydrolysis using aqueous alkali solution. Accordingly, the structural effects of the resins on the adsorption of heavy metal ions were investigated. Poly(St‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Pb²⁺, Cd²⁺, and Cu²⁺, whereas poly(MMA‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Cu²⁺, Cd²⁺, and Co²⁺. On the other hand, poly(St‐co‐MMA‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Pb²⁺, Cd²⁺, Hg²⁺, Co²⁺, and Cu²⁺: a synergistic effect on the adsorption of heavy metal ions like Pb²⁺, Cd²⁺, Hg²⁺, and Co²⁺ was observed. The adsorption ability of poly(St‐co‐MMA‐co‐DVB)‐based chelating resin among three kinds of chelating resins was relatively good.     

Ion‐selective Imprinted Superporous Monolith for Cadmium Removal from Human Plasma

Abstract

Molecular recognition based separation systems have received much attention because of their high selectivity for target molecules. Molecular imprinting has been recognized as a promising technique for the development of affinity adsorbents. Molecularly imprinted polymers (MIP) are easy to prepare, stable, inexpensive, and capable of molecular recognition. Cadmium is a carcinogenic and mutagenic element. The limit value of cadmium in blood should be no higher than 50 pg/L when exposure to cadmium is unavoidable in industry. There is no specific treatment available for acute or chronic metal poisoning. Besides supportive therapy and hemodialysis, metal poisoning is often treated with commercially available chelating agents including EDTA and dimercaprol. However, there is histopathological evidence for increased toxicity in animals when these agents are utilized. The aim of this study is to prepare superporous ion‐imprinted polymer monolith which can be used for the selective removal of Cd²⁺ ions from Cd²⁺‐overdosed human plasma. N‐methacryloly‐(L)‐cysteinemethylester (MAC) was chosen as the complexing monomer. In the first step, MAC synthesized by using methacryloyl chloride and cysteine. Cd²⁺ was complexed with MAC monomer and the Cd²⁺‐imprinted poly(HEMA‐MAC) monoliths were synthesized by bulk polymerization. After that, Cd²⁺ ions were removed by 0.1 M thiourea and 0.1 M HNO₃ solutions, respectively. Cd²⁺‐imprinted poly(HEMA‐MAC) monoliths had a specific surface area of 226.8 m²/g and the swelling ratio was determined to be 76%. According to the elemental analysis results, monoliths contain approximately 58.3 µmol/g of MAC. The maximum adsorption capacity for Cd²⁺ ions was 26.6 µmol/g of the dry weight of monolith. The adsorption capacity decreased significantly from 23.25 µmol/g to 3.08 µmol/g polymer with the increase of the flow‐rate from 1 mL/min to 4 mL/min. The Cd²⁺‐imprinted poly(HEMA‐MAC) monolith could be used many times without decreasing their adsorption capacities significantly.     

Purging Metal Impurities from Nuclear Fuel using Centrifuge Cascades with Additional Feed Component

Abstract

Nuclear fuel can be purged, that is metal impurities can be extracted from the uranium hexafluoride, by feeding an additional component, a kind of Freon, C₆F₁₂, which is chemically stable with respect to uranium hexafluoride, into the centrifuge purge cascade. The metal impurities are then continuously withdrawn from the purge cascade as a result of the additional feed. Centrifuges can not be easily used for the purge process without the Freon because the amount of metal impurities in the nuclear fuel is usually very small, thus the flow of impurities withdrawn from the product end of the purge cascade needs to be periodically closed down to minimize the loss of uranium hexafluoride. This results in the accumulation of light impurities such as air and HF in stages near the product end of the purge cascade. These light impurities inside the centrifuges may reduce the working effectiveness of the centrifuges or even put them out of service. The additional Freon eliminates this problem, because the light gas can be extracted from the cascade as soon as it reaches the product end of the cascade. Numerical calculations using a typical metal impurity CrO₂F₂ illustrate the effect of the additional Freon feed in the purge process.     

Synthesis and Metal‐ion Binding Properties of New N2S4O2‐ and N2S5O2‐Donor Macrocycles

Abstract

Synthetic procedures for new mixed‐donor macrocycle compounds were reported. The macrocyclic compounds were used in solvent extraction metal picrates such as Ag⁺, Hg²⁺, Cd²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Mn²⁺, Pb²⁺, and Co²⁺. The metal picrate extractions were investigated at 25±0.1°C with the aid of UV‐visible spectrometry. It was found that 6,7,9,10,12,13,23,24‐octahydro‐19H,26Hdibenzo[h,t](1,4,7,13,16,22,10,19) dioxatetrathiadiazasiclotetracosine‐20,27(21H,28H)‐dione showed selectivity towards Ag⁺, Hg²⁺, and Cd²⁺ among the other metals. The extraction constants (Log K_ex) and complex compositions were determined for the Ag⁺ and Hg²⁺ complexes for this compound and 9,10,12,13,23,24,26,27,29,30‐decahydro‐5H,15H‐dibenzo‐[h,w][1,4,7,13,16,19,25‐,10,22] dioxapentathiadiazacycloheptacosine‐6,16(7H,17H)‐dione.     

反应硼化烧结法制备陶瓷-金属高硬覆层材料

硼化物是一种优良的耐磨材料,但由于其较差的烧结性能和极大的脆性限制了这种材料的应用,反应硼化烧结法很好地解决了这一问题。本文介绍了反应硼化烧结法的条件,反应硼化烧结法典型的烧结过程以及陶瓷-金属高硬覆层材料的制备过程。指出由于高硬覆层材料具有优良的性能,因而对于反应硼化烧结法制备陶瓷-金属高硬覆层材料的研究具有重要的理论和实践意义。     

金属络合型聚丙烯腈抗菌消臭纤维的结构与性能

利用含多官能团聚丙烯腈纤维和不同金属离子反应 ,制备了一种金属络合型聚丙烯腈抗菌消臭纤维 ,并测定了其抗菌消臭性能。结果表明 :该纤维不仅含有多种含氮、含氧、杂环等官能团 ,且形成金属络合物 ,对不同菌类具备优异的杀菌活性 ,并具有抗菌谱广 ,作用时间持久和效率高等特点。     

粉煤灰处理含重金属废水试验研究

本文比较了粉煤灰及酸活化粉煤灰处理重金属离子的性能 ,着重探讨了酸活化粉煤灰去除工业电镀废水中重金属离子铬、铅、铜、镉的适宜条件 ,经处理后的废水可达到排放标准。同时提出了一套成功的粉煤灰活化工艺 ,具有较好的社会效益和经济效益。