Surface functionalized mesoporous silicates, MCM-41s, having 3-(2-pyridylmethylideneimino)propyl group (PI-MCM-41) or 3-(2-quinolylmethylideneimino)propyl group (QI-MCM-41) were prepared via Schiff ...base reaction, and the adsorption behavior of metal ions onto the modified MCM-41s was investigated. The function groups on the modified MCM-41 surface were confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and elemental analysis. The metal ions examined, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+, were quantitatively adsorbed on the PI-MCM-41 and QI-MCM-41, except for Mn2+. In the complexation with these metal ions, it was suggested that imine-N and heterocyclic-N atoms act as donor atoms. In addition, it was considered that the hydrophobicity derived from the organo-functional groups modified on MCM-41 contributed to improving the adsorption ability.
No primary scandium (Sc) ore exists on the earth and therefore securing a stable supply of Sc is required. The authors reported previously that a hexane solution containing 0.1 mol dm-3 of ...O,O-bis(2-ethylhexyl) hydrogen thiophosphate (MSP-8®) could extract Sc(III) quantitatively from an aqueous solution containing 1.0 mol dm-3 of zirconyl (ZrO(II)) and 0.10 mol dm-3 of tripotassium citrate as a masking reagent. The present study was carried out in order to establish the liquid-liquid extraction separation of Sc from a simulated waste water produced in the zirconium (Zr) refinery by using MSP-8 as the extractant.
Oxidized di(2-ethylhexyl)dithiophoshate (Phoslex DT-8) in n-hexane is shown to extract Sc(III) greater than 97% in the pH range of 1.01–4.46, while ZrO(II) is not extracted under the same conditions. ...Phoslex DT-8 was oxidized by blowing air in it, and the percent extraction of Sc(III) increased along with the duration of air-oxidation. The present extraction system can be used to separate Sc(III) from ZrO(II), Ti(III), Y(III) and Al(III) in a single batchwise extraction.
► Sc(III) can be extracted with oxidized Phoslex DT-8 in n-hexane. ► Sc(III) can be stripped from Phoslex DT-8 in n-hexane using 3 M-HCl. ► Single stage separation of Sc from ZrO, Ti, Y and Al has been shown.
—In this study mesoporous silicates MCM-41 and SBA-15 were investigated for their potential as metal ion-selective adsorbents. The greatest advantage of these materials is their large surface area, ...uniform pore size and controlled surface chemistry, and hence their potential for adsorption processes. The studies of the adsorption of transition metal ions onto MCM-41 examined the comparative adsorption behavior of Zn(II) and Cu(II), using acetylacetone (Hacac) as a chelating agent. The results showed that the MCM-41/Hacac system has potential as an ion-selective adsorbent material. However, due to the relatively small pore size and potential instability of MCM-41 when immersed in water for long time periods, a second mesoporous silicate, SBA-15, has been investigated. The SBA-15 was coated with octadecyltrichlorosilane (C18), and then loaded with a chelating agent (Cyanex 272) and assessed for its potential as an adsorbent material. The surface-modified SBA-15 has been found to have high metal ion selectivity and extractability, and hence good potential as an alternative to established solvent extraction systems.
We have developed a simple analog-to-digital converter (ADC) by using free software such as computer-aided design (CAD) software for an electronic circuit, a filter circuit simulator, an ...integrated-developing environment (IDE) for programming a controller, and that for a PC to acquire and display the data. The ADC can record a temporal signal produced by chromatography and flow-injection analysis. It has two voltage measurement ranges: ±2.048 V and ±1.024 V, respectively, with 14-bit resolution and a four samples s−1 sampling rate. The voltage resolution is 0.25 mV and 0.125 mV per one ADC reading for ±2.048 V and ±1.024 V, respectively. Its dimensions were 100 × 70 × 30 mm, and mass was 110 g. We have evaluated its performance, including the linearity and the difference between the two devices. For ±1.024 V range, the calibration curve for one ADC and another was D = 7954V - 5 and D = 7946V + 30, respectively, where D is an ADC reading, and V is an input voltage. For another range, it was D = 3972V - 3 and D = 3968V + 15, respectively. Their slopes and intercept agreed with each other, and had good linearity, R2 > 0.9999. We have then successfully applied it to the sequential injection analysis (SIA) of chromium(VI) using diphenylcarbazide as a coloring reagent. The circuit diagram and programs developed in this paper are available on our website.
Structural control of Schiff base ligands for selective extraction of copper(II) was investigated by changing pendant arms and the distance between two imine-N donor atoms in ligands. Di-Schiff base ...ligands, N,N′-bis(2-quinolylmethylidene)-1,2- diiminoethane (BQIE), N,N′-bis(2-pyridylmethylidene)-1,3-diimino-2,2-dimethylpropane (BPMP) and N,N′-bis(2- quinolylmethylidene)-1,3-diimino-2,2-dimethylpropane (BQMP), were used as complexation reagents for ion-pair extraction of divalent transition metal cations into nitrobenzene with picrate anion. The pendant arms affected the lipophilicity of ligand to nitrobenzene, due to their polarity. The distance between two imine-N atoms, on the contrary, was a factor of controlling the extraction selectivity. BQMP has both 2-quinolyl pendant arms and trimethylene backbone structure; use of BQMP as a complexation reagent led to the selective extraction of Cu2+ in the system.
This investigation examines metal ion adsorption on mesoporous silicate, MCM-41, synthesized from sodium silicate solution and cethyltrimethylammonium bromide (CTAB). MCM-41 has potential as an ...adsorbent material, with a regular hexagonal pore structure, large specific surface area, and large pore volume. The MCM-41 synthesized for this investigation is characterized using powder X-ray diffraction and nitrogen adsorption and desorption isotherms data. The adsorption behavior for cadmium(II) and lead(II) onto MCM-41 was studied by contacting the mesoporous silicate with an aqueous solution of metal salts and acetylacetone. Both Cd
2+
and Pb
2+
were found to quantitatively adsorb onto MCM-41. The results of this study suggest that MCM-41 may have applications in the recovery of toxic metals from waste waters.
During the accident at the Fukushima Dai-ichi Nuclear Power Plant at March 2011, radioactive cesium (137Cs), which has a long half-life of about 30 years, was released into the environment around the ...plant. Therefore, methods for the recovery and fixation of 137Cs are required. The CHA-type zeolite, chabazite, has high Cs+ selectivity; Cs+ ions have a diameter of approximately 0.36 nm and can thus enter into and be adsorbed by chabazite, which contains pores with diameters of 0.38 nm. However, some Cs+ ions in the large pores may be released by cation exchange in solutions with a high cation concentration. The ANA-type zeolite (ANA) has pores with 0.28 nm diameters, which are smaller than the diameter of Cs+ ions. ANA is synthesized by an alkaline hydrothermal treatment of natural zeolites such as clinoptilolite, mordenite, and chabazite. This hydrothermal modification may be useful for the fixation of Cs+. In the present study, the modification of chabazite exchanged with Cs+ to produce ANA by hydrothermal treatment was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX), and the solution stability of Cs+ in the ANA was also evaluated using inductively coupled plasma-mass spectrometry (ICP-MS). Modification of chabazite exchanged with Cs+ to produce single-phase ANA was confirmed in a 1.0 mol/L NaOH solution held at 200 °C for 3 to 144 h. The intensity of XRD peaks corresponding to (211) and (220) planes decreased with increasing Cs+ concentration. SEM observations showed that the ANA crystals had a trapezohedral shape and a size of about 5 µm. EDX analysis of ANA crystals confirmed the presence of Cs+. The amount of Cs+ eluted from ANA in a 0.6 mol/L NaCl solution was less than 1.7%.
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