Noriaki Seko

Enhanced trace phosphate removal from water by zirconium(IV) loaded fibrous adsorbent

This study was investigated for the trace phosphate removal at high feed flow rate by ligand exchange fibrous adsorbent. The zirconium(IV) loaded bifunctional fibers containing both phosphonate and sulfonate were used as a highly selective ligand exchange adsorbent for trace phosphate removal from water. The precursory fiber of the bifunctional fibers was co-grafted by polymerization of chloromethylstyrene and styrene onto polyethylene coated polypropylene fiber and then bifunctional fibers were prepared by Arbusov reaction followed by phosphorylation and sulfonation. Phosphate adsorption experimental work was carried out in column approach. Phosphate adsorption increased with decreasing the pH of feed solutions. An increase in the feeds flow rate brings a decrease in both breakthrough capacity and total adsorption. The effect of competing anions on phosphate adsorption systems was investigated. The experimental findings reveal that the phosphate adsorption was not affected in the presence of competing anions such as chloride and sulfate despite the enhancement of the breakthrough points and total adsorption. Due to high selectivity to phosphate species, low concentration level of phosphate (0.22 mg/L) was removed at high feed flow rate of 450 h(-1) in space velocity. The adsorbed phosphate on the Zr(IV) loaded fibrous column was quantitatively eluted with 0.1 M NaOH solution and then the column was regenerated by 0.5M H2SO4 for the next adsorption operation. During many adsorption-elution-regeneration cycles, no measurable Zr(IV) was found in the column effluents. Therefore, the Zr(IV) loaded bifunctional fibrous adsorbent is to be an effective means to treat wastewater to prevent eutrophication in the receiving water bodies for long time without any deterioration.

Aquaculture of Uranium in Seawater by a Fabric-Adsorbent Submerged System

Abstract The total amount of uranium dissolved in seawater at a uniform concentration of 3 mg U/m3 in the world’s oceans is 4.5 billion tons. An adsorption method using polymeric adsorbents capable of specifically recovering uranium from seawater is reported to be economically feasible. A uranium-specific nonwoven fabric was used as the adsorbent packed in an adsorption cage 16 m2 in cross-sectional area and 16 cm in height. We submerged three adsorption cages in the Pacific Ocean at a depth of 20 m at 7 km offshore of Japan. The three adsorption cages consisted of stacks of 52 000 sheets of the uranium-specific non-woven fabric with a total mass of 350 kg. The total amount of uranium recovered by the nonwoven fabric was >1 kg in terms of yellow cake during a total submersion time of 240 days in the ocean.

Preparation of hydrophilic amidoxime fibers by cografting acrylonitrile and methacrylic acid from an optimized monomer composition

Abstract To improve the adsorption rate of uranium from seawater, hydrophilic amidoxime (AO) fibers were prepared by cografting of methacrylic acid (MAA) with acrylonitrile (AN) onto polypropylene fibers and subsequent conversion of the produced cyano group to an amidoxime group by reaction with hydroxylamine. An optimum amidoximation time of 0.75 h was selected at a weight ratio of AN to MAA (x/y) of 80/20. By varying x/y in the monomer mixture, cografted polymers were prepared. The value of x/y governed the AO group density and water content of the resultant fibrous adsorbents. As x/y increased, the AO group density of the fiber increased and its water content decreased. The AO/MAA adsorbent, based on the PP fibers prepared by cografting at an x/y of 60/40 and subsequent amidoximation, exhibited the highest uranium adsorption rate in the flow-through mode.

A weak-base fibrous anion exchanger effective for rapid phosphate removal from water.

This work investigated that weak-base anion exchange fibers named FVA-c and FVA-f were selectively and rapidly taken up phosphate from water. The chemical structure of both FVA-c and FVA-f was the same; i.e., poly(vinylamine) chains grafted onto polyethylene coated polypropylene fibers. Batch study using FVA-c clarified that this preferred phosphate to chloride, nitrate and sulfate in neutral pH region and an equilibrium capacity of FVA-c for phosphate was from 2.45 to 6.87 mmol/g. Column study using FVA-f made it clear that breakthrough capacities of FVA-f were not strongly affected by flow rates from 150 to 2000 h(-1) as well as phosphate feed concentration from 0.072 to 1.6mM. Under these conditions, breakthrough capacities were from 0.84 to 1.43 mmol/g indicating high kinetic performances. Trace concentration of phosphate was also removed from feeds containing 0.021 and 0.035 mM of phosphate at high feed flow rate of 2500 h(-1), breakthrough capacities were 0.676 and 0.741 mmol/g, respectively. The column study also clarified that chloride and sulfate did not strongly interfere with phosphate uptake even in their presence of equimolar and fivefold molar levels. Adsorbed phosphate on FVA-f was quantitatively eluted with 1M HCl acid and regenerated into hydrochloride form simultaneously for next phosphate adsorption operation. Therefore, FVA-f is able to use long time even under rigorous chemical treatment of multiple regeneration/reuse cycles without any noticeable deterioration.

Fine Fibrous Amidoxime Adsorbent Synthesized by Grafting and Uranium Adsorption–Elution Cyclic Test with Seawater

Abstract Fibrous amidoxime adsorbents were prepared by radiation‐induced co‐grafting of acrylonitrile (AN) and methacrylic acid (MAA) and subsequent amidoximation. Adsorption of uranium in seawater was evaluated by pumping seawater into the adsorbent column. The best monomer ratio of AN and MAA was 7:3 for continual usage of uranium adsorption. Though hydrochloric acid is an effective eluting agent for the metals adsorbed on the adsorbent, amidoxime groups were simultaneously damaged after five cycles of adsorption–desorption. This deterioration was reduced by an alkaline treatment of the adsorbents after each elution. Furthermore, various organic acids were examined as elution agents. It was found that the 80% of adsorption activity was still maintained after five cycles of adsorption–desorption when tartaric acid was used for eluting agent.

Adsorption Efficiency of a New Adsorbent Towards Uranium and Vanadium Ions at Low Concentrations

Abstract A new type of fibrous adsorbent with excess amidoxime groups was synthesized by radiation-induced graft polymerization. Glycidyl methacrylate (GMA) was first radiation‐grafted on polyethylene‐coated polypropylene nonwoven fabrics and chemically modified with 3,3′-iminodipropionitrile [NH (–CH2–CH2–CN)2] (IDPN), which was further reacted with hydroxylamine to obtain graft chains containing two amidoxime groups per graft repeating units. The adsorption properties of this new adsorbent for uranium (U), vanadium (V), lead (Pb), copper (Cu), and cobalt (Co) ions at low concentrations (3.3–1000 ppb) were investigated by a batch process. The adsorbent showed enhanced adsorption capacity for uranium and vanadium ions. In adsorption studies from a mixture of metal ions in aqueous solutions, the adsorbent showed selectivity for metal ions in the following order: V > U ≫ Cu ≥ Pb ≫ Co. The selectivity of the adsorbent was assessed by determining the distribution coefficient D, of the metal ions studied. The U and V ions were shown to be up to six times more selectively adsorbed onto the new adsorbent than the other metal ions.

Removal of boron by boron-selective adsorbent prepared using radiation induced grafting technique

Abstract Boron-selective adsorbent was synthesized by grafting the glycidyl methacrylate onto polyethylene (PE) non-woven fiber using electron beam ionizing radiation. Subsequently, the grafted PE with 180% degree of grafting was chemically modified using n-methyl-d-glucamine (NMDG). The density of NMDG of the synthesized adsorbent was 2.2 mmol/g. Batch mode adsorption’s test showed that pH ranging from 4 to 8 had highest adsorption capacity and the adsorption capacity of the grafted adsorbent was 14.5 mg-B/g-adsorbent. Column mode adsorption test showed a marginal reduction of total breakthrough capacity from 13.8 to 12.7 mg-B/g-adsorbent, for feeding speed of space velocity (SV) 15 and SV 400, respectively. This indicated that the synthesized adsorbent had exhibited high performances of boron adsorption and desorption process. High performances of the prepared adsorbent could contribute from few factors such as fine size of the adsorbent, large surface area, and homogeneous pore size. Desorption of boro...

A Novel Avenue to Gold Nanostructured Microtubes Using Functionalized Fiber as the Ligand, the Reductant, and the Template

Gold nanostructured microtubes (AuNMTs) are prepared using a tertiary amine group-functionalized polyethylene (PE)-coated polypropylene (PP) nonwoven fabric as a ligand, a reductant, and a template, which takes advantage of the different radiation effects of PE and PP. The Au(III) ions are absorbed and reduced only in the PE layer to form the aggregation of gold nanoparticles; thus, AuNMTs are obtained after the calcination.

Surface treatment of poly(tetrafluoroethylene) and perfluoroethylene- propylene by radiation grafting

Poly(tetrafluoroethylene) (PTFE) and perfluoroethylene-propylene (PFEP) have many desirable properties for application to electronic devices, such as low dielectric constant and loss tangent. However, the weak adhesion of the polymer to various metals, associated with the chemical inertness of the fluorine resin surface, fails to satisfy many of the industry requirements. Surface treatment of PTFE and PFEP by radiation-induced graft polymerization was carried out to improve the adhesion. Peel adhesion strengths of 10.3 and 14.5 N/cm were attained for PTFE/Cu and PFEP/Cu, respectively by the treatment. In addition, the dielectric function of grafted PTFE and grafted PFEP remained almost unchanged after the graft polymerization.

New Advanced Fabrication Technique for Millimeter-Wave Planar Components based on Fluororesin Substrates using Graft Polymerization

As the importance of advanced millimeter-wave diagnostics increases, a reliable and accurate fabrication technique for high-performance devices and relevant components is essential. We describe a new improved fabrication technique for millimeter-wave planar components, such as antennas using low-loss fluororesin substrates. A fragile adhesion between the copper foil and fluororesin substrate and the accuracy of the device pattern using conventional fabrication techniques have been prime suspects in the failure of the devices. In order to solve these problems, surface treatment of fluororesin films and a fabrication method using electro-fine-forming (EF2) are proposed. The peel adhesion strength between the metal and fluororesin films and the value of the dielectric constant of the fluororesin films before and after grafting are reported. A prototype antenna using conventional fluororesin substrates and grafted-poly(tetrafluoroethylene) (PTFE) films produced using the EF2 fabrication technique are also introduced.