Papers by Keyword: Complexation

Abstract: Weak water resistance is a big obstacle for clay materials to overcome in modern construction industry. Compared to the hydraulic stabilized additives, bio-additives have a lower carbon footprint and have been used in many vernacular construction techniques to immobilize clay. In this work, the traditional recipes of tannin and iron have been revisited, in particular, the question of pH and iron solubility has been explored. Oak tannin and FeCl₃ were chosen and their influence on the properties of clay materials in terms of rheological properties, compressive strength, and water resistance were characterized in the lab. Based on the results, tannin can reduce the yield stress of paste while with the addition of FeCl₃, the yield stress of tannin dispersed pastes increased to a value similar to the reference sample but lower than the value contain only FeCl₃. The increase was attributed to the complex reaction between tannin and Fe³⁺. The iron-tannin complexes can also increase the samples’ strength and water resistance. Although the complexes did not change the hydrophilic properties of the samples’ surface, they prevent the ingression of water. These results are very promising as they allow the production of a fluid earth material that is water-resistant. This opens a wide range of application potentials and can help to mainstream earth materials in construction.

Abstract: New complex compounds of polyacrylate and polymethacrylate guanidine and composites based on them with Fe (II) ions were studied by the spectrophotometric method. The optimal conditions for complexation were studied. Thus, it was revealed that metal-complex polymers are formed at λ = 500 nm for PAG and λ = 510 nm for PMAG. The formation of complexes at pH = 6-7 was also proved.

Abstract: Gallium (Ga) is a critical element for the electronic industry, however, its long-term supply is not assured. Thus, the recovery of Ga from industrial wastewaters is important. Selective sorption is a recommended technology for the recovery of Ga from industrial wastewaters, however, selective sorbents are elusive. Desferrioxamine B (DFOB), a hydroxomate siderophore that is known to be highly selective towards Fe³⁺, is tested for its ability to complex Ga. This study demonstrated that DFOB forms 1:1 complex with Ga and the maximum Q_e-Ga is 124.4 mg of Ga complexed per g of DFOB. Further, the complexation mechanism of Ga³⁺ and Fe³⁺ with DFOB is similar, as indicated by NMR, suggesting that the selectivity of DFOB towards Fe³⁺ will be extended to Ga³⁺ as well. Thus, DFOB seems to be a suitable candidate for the sorption of Ga from industrial wastewaters.

Abstract: Acid-base properties and selectivity of absorption such ions as REE (Eu^3+, Gd³⁺, Nd³⁺, Yb³⁺) from solutions with various ionic force by the fibrous ampholytes PAN-FOSPAN and PAN-IDUC are investigated. PAN-FOSPAN shows the greatest selectivity to ions of REE. This fact can be used for division and the subsequent definition of ions. PAN-IDUC as a high selective fibrous sorbent after alkaline treatment is perspective one for absorption of the REE sum.

Abstract: The complexation abilities of 5,11,17,23,29,35-hexacarboxy-37,38,39,40,41,42- hexa-methoxy-hydroxamic calix[6]arene extraction of metal ions (Cu2+, Ni2+, Na+, Fe3+, Cd3+, Mn2+, Pb2+) were studied. And the complexation ration of Cu2+ and Pb2+ were obtained by Job's method. The selective removal of Cu2+ (Pb2+) coexisting with alkali metals ions (Na+, K+) and alkaline earth metal ions (Ca2+, Mg2+), heavy metal ions (Zn2+, Mn2+, Pb2+(Cu2+), Ni2+) and anions (CO32-, C2O42-, SO42-, NO3-) were studied separately . The results revealed that the percent of Cu2+(Pb2+) removal in the presence of alkali metals ions and alkaline earth metal ions was over 83.8% (90%) and in the presence of anions was over 90.1% (81.3%) while the percent of Cu2+(Pb2+) removal in the presence of heavy metal ions was lower than 70.6% (70.0%), and the minimum percent of Cu2+(Pb2+) removal in the presence of heavy metal ions was 32.7% (61.2%).

Abstract: The calix [6] arene and 5,11,17,23,29,35-butyl-25,26,27,28,29,30-diethyl phosphates calix [6] arene (EtPO6) were synthesized and their complexation with different metal ions were investigated. The calix [6] arene and EtPO6 were characterized by IR spectrum. The complexation between the host (calix [6] arene and EtPO6) and the guest (metal ions) were investigated by UV-VIS spectrum and extraction experiments. The results show that the complexation of metal ions by calix [6] aren ranked as Na⁺ > Cu²⁺ > Pb²⁺ > UO₂²⁺ > Fe³⁺ > Cr³⁺ > Ni²⁺, and the complexation of metal ions by EtPO6 ranked as UO₂²⁺ > Cu²⁺ > Fe³⁺ > Pb²⁺ > Na⁺ > Cr³⁺ > Ni²⁺. Compared with calix [6] aren, the extraction capacity of UO₂²⁺, Cu²⁺, Fe³⁺, Pb²⁺, Cr³⁺ and Ni²⁺ ions by EtPO6 increased by 37.6%, 10.2%, 10.6%, 9.6%, 2.2%, 4.4%, respectively, while that of Na⁺ ion decreased by 22.3%.

Abstract: Sorption behaviors of propranolol (PRO) on montmorillonite and kaolinite in the presence of fulvic acid (FA) and humic acid (HA) were investigated. Complexation of propranolol with FA/HA also have been studied using the fluorescence quenching method. PRO could be complexed by FA and HA strongly in the 5-9 pH range. PRO sorption was found to be higher on montmorillonite than on kaolinite. In the presence of FA/HA, the sorption of PRO on montmorillonite and kaolinite was inhibited and enhanced respectively. The mechanism is due to the free PRO and complexed PRO has different affinity to montmorillonite and kaolinite surfaces.

Abstract: Calix[6]arene carbon chain alkyl sulfoxide derivative have been successfully synthesized. IR spectra confirmed the introduction of sulfoxide group on calix[6]arene. UV spectra indicated that calix[6]arene sulfoxide derivative has a high complexation of uranium. The coordination ratio between the calix[6]arene sulfoxide derivative with uranium is 3:2, which was determined by Job’s method. Extraction experiments showed that the extraction efficiency of uranium is able to achieve 73.8%, which suggested the potential application of calix[6]arene sulfoxide derivative as an excellent uranium extraction agent.

Abstract: Polymer enhanced ultrafiltration was used to remove Cr(III) from aqueous solution by using complexing agent, copolymer of maleic acid and acrylic acid (PMA-100), and polyvinyl butyral (PVB) ultrafiltration membrane. Effects of mass ratio of polymer/metal (P/M), pH, added salt and citric acid on the rejection of Cr(III) were investigated. Results show that the rejection of Cr(III) can be 97.2% for 10.0 mg/L aqueous solution at P/M 6.0 and pH 5.0, and the a complete removal occurs when pH is not smaller than 6.0, but the membrane will be fouled due to the formation of hydroxide precipitation at pH 6.0. The addition of the citric acid leads to a significant decrease of rejection while the added salt (up to 0.1M) has little effect on the rejection of Cr(III).

Abstract: In this work, the solution of PA6/GdCl3 with different complex ratios were prepared, using gadolinium trichloride (GdCl3) as complexing agent, formic acid and hydrochloric acid as solvent. The fibers were then prepared by dry spinning method and characterized with scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy and Instron tensile testing. The results indicated that fibers with good morphology and mechanical properties could be obtained when mole ratio (MR) was 0.04 and PA6 concentration was 22wt%. Moreover, we found that spinning pressure had significant influence on the properties of fibers.