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Parajuli, D.; Hirota, Koichi; Seko, Noriaki; Oto, Keisuke*
Proceedings of 12th International Conference on Environmental Science and Technology (CEST 2011), p.B835 - B842, 2011/09
Cotton consisting of nearly 100% cellulose is one of the widely available natural polymers with versatile applications. In order to know the possibility of using cellulosic materials for the development of functional adsorbents by radiation induced vinyl graft modification method, cotton was studied as a representative natural material. In the present study, cotton was pre-irradiated with electron beam and glycidyl methacrylate (GMA) was grafted onto it. Various parameters like irradiation dose, solvent system, monomer concentration, grafting time, etc were studied to achieve the optimum graft yield. Once GMA containing reactive epoxy group was grafted onto the cotton matrix, various functional groups possessing different selectivity behavior for different metals were introduced by simple chemical reaction. The newly developed functional-cotton derivatives were studied for their ion exchange performances and selectivity patterns mainly for palladium in HCl and HCl-HNO
systems.
Hirota, Koichi; Parajuli, D.; Seko, Noriaki
Proceedings of 12th International Conference on Radiation Curing in Asia (RadTech Asia 2011) (Internet), p.136 - 137, 2011/06
Conventional methods for the recovery of precious metals are solvent extraction, chemical precipitation, and use of ion exchange resins. However these methods are facing to significant disadvantages like high capital costs, large chemical and energy requirements, and generation of toxic sludge or other waste products creating additional burden. Development of biomass based sorbents is a better, probably the best, option with lower capital cost and higher efficiency. Although the biomass-sorbents are better than the existing methods, the methods of preparing sorbents from them usually use several kinds of chemicals. In the present work, biomass has been modified with functional groups after electron beam irradiation and its performance for the recovery of precious metals has been studied. The obtained results are compared with that of chemically modified derivative.
Parajuli, D.; Hirota, Koichi; Seko, Noriaki
Journal of Radioanalytical and Nuclear Chemistry, 288(1), p.53 - 58, 2011/04
Times Cited Count：20 Percentile：80.12(Chemistry, Analytical)Parajuli, D.; Hirota, Koichi; Inoue, Katsutoshi*
Industrial & Engineering Chemistry Research, 48(23), p.10163 - 10168, 2009/11
Times Cited Count：27 Percentile：62.11(Engineering, Chemical)A quaternary amine type sorbent has been prepared by the immobilization of trimethylamine group onto the crosslinked lignophenol matrix. The sorption behavior for a number of metal ions was studied in hydrochloric acid medium. From the batch test of individual metal ion as well as the mixture solution containing equal molar concentration of various metal ions, the sorbent was found to hold selectivity for Au(III), Pd(II), and Pt(IV) ions only with negligible sorption for other metal ions like Cu(II), Co(II), Fe(III), Ni(II), and Zn(II). The sorption kinetics was studied at 303, 323, and 338 K and elucidated the order of sorption of Au(III), Pd(II), and Pt(IV) and from the values of rate constants at different temperatures, the energy of activation has been evaluated. The sorption isotherm study revealed the Langmuir type sorption and from the Langmuir charts the maximum loading capacity of Au(III), Pd(II), and Pt(IV) has been evaluated.
Parajuli, D.; Hirota, Koichi
Journal of Colloid and Interface Science, 338(2), p.371 - 375, 2009/10
Times Cited Count：17 Percentile：38.70(Chemistry, Physical)Parajuli, D.; Khunathai, K.*; Adhikari, C. R.*; Inoue, Katsutoshi*; Oto, Keisuke*; Kawakita, Hidetaka*; Funaoka, Masamitsu*; Hirota, Koichi
Minerals Engineering, 22(13), p.1173 - 1178, 2009/10
Times Cited Count：49 Percentile：89.01(Engineering, Chemical)Parajuli, D.; Hirota, Koichi
ChemSusChem, 2(10), p.965 - 967, 2009/09
Times Cited Count：2 Percentile：13.02(Chemistry, Multidisciplinary)Hirota, Koichi; Parajuli, D.; Seko, Noriaki
no journal, ,
Lignin in Japanese cedar wood powder was extracted in the form of lignophenol and was modified with ethylenediamine and trimethylamine groups using Electron-beam technology. The functionalized lignophenol adsorbents were then studied for the recovery of precious metals: Au, Pt, and Pd from urban mine. From the batch test of mixture solution containing equal molar concentration of various metal ions, the sorbent was found to hold selectivity for Au(III), Pd(II), and Pt(IV) ions only with negligible sorption for other metal ions like Cu(II), Co(II), Fe(III), Ni(II), and Zn(II). The biomass sorbent is expected to be an excellent material for recovering the precious metal from urban mine.
Parajuli, D.; Hirota, Koichi; Seko, Noriaki
no journal, ,
Hirota, Koichi; Parajuli, D.; Seko, Noriaki
no journal, ,
High level radioactive waste contains precious metals like Pd, Rh, and Ru. Biomass sorbents were synthesized using Japanese cedar wood and tested its adsorption performance. The results showed that the sorbents functionalize with thioamide group exhibit high adsorption ability for Pd(II) under 
-ray irradiation.
Hirota, Koichi; Parajuli, D.; Seko, Noriaki
no journal, ,
The adsorbent (CWP-TU) was prepared by heating a 1:2 mixture of cedar wood powder (CWP) and thiourea using a microwave. Because the high level waste is contained basically in nitric acid, the adsorption test was performed in 3 M nitric acid and found that Pd(II) adsorption is preferred. The Pd(II) only selectivity was revealed by taking simulated HLW solution containing 15 different metals in same molar ratio as in the real fission waste. The feasibility of recovering Pd(II) using CWP-TU from highly radioactive HLW solution was tested by irradiating the mixture of adsorbent and simulated HLW solution by rays for 50 h with total dose of 500 kGy. The results show that, unlike on commercial synthetic extractants, there is no direct effect of radiation on the Pd(II) binding ability of the sorbent.
Parajuli, D.; Hirota, Koichi; Seko, Noriaki
no journal, ,
High level radioactive liquid waste (HLW) generated during the nuclear fuel processing is rich in valuable metals like Pd(II), Rh, Ru, etc. However, due to the stability and selectivity problems of commonly used extractants in highly acidic and radioactive condition of HLW, successful separation of useful metals is yet to realize. Expecting the potential application of Japanese Cedar Wood powder (CWP), which contains high amount of radiation-resistant lignin, we developed a sorbent containing thiamide group by dry modification of CWP with thiourea using microwave heating method. The new sorbent is found to be highly effective for the separation of Pd from simulated HLW solution. Most important result is the stability of the material with respect to the Pd loading capacity upon exposure to as high as 2000 kGy rays (10 kGy per hour). This result verifies the strong prospective of using natural material especially in extreme conditions like HLW.
Parajuli, D.; Hirota, Koichi
no journal, ,
Cotton consisting of nearly 100% cellulose is one of the widely available natural polymers with versatile applications. In order to know the possibility of using cellulosic materials for the development of functional adsorbents by radiation induced vinyl graft modification method, cotton was studied as a representative biomass. In the present study, cotton was pre-irradiated with electron beam and glycidyl methacrylate (GMA) was grafted onto it. Various parameters like irradiation dose, monomer concentration, grafting temperature, time, etc were studied to achieve the optimum graft yield. Once GMA containing reactive epoxy group was grafted onto the cotton matrix, various functional groups possessing different selectivity behavior for different metals were introduced by simple chemical reaction. The newly developed functional-cotton derivatives were studied for their ion exchange performances and selectivity patterns mainly for the precious metals in HCl and HNO systems.
Parajuli, D.; Hirota, Koichi
no journal, ,
Parajuli, D.; Hirota, Koichi; Seko, Noriaki
no journal, ,
Wood derived lignin was modified with ethylenediamine after electron beam irradiation and its performance for the recovery of precious metals was compared to that modified by chemicals. The results showed that the sorbents obtained by the irradiation had higher sorption ability for precious metals. Electron beam has an advantage for creating high performance biomass absorbents for precious metals such as Au, Pt, and Pd.
Hirota, Koichi; Parajuli, D.; Seko, Noriaki
no journal, ,
Wood derived lignin has been modified with ethylenediamine (EN-CLP) after electron beam irradiation and its performance for the recovery of precious metals has been studied and the results are compared with that of chemically modified derivative. The maximum adsorption capacities of both the adsorbents for Au(III), Pd(II), and Pt(IV) were evaluated as: EN-CLP(EB) 3.1, 2.3, 0.85 mol/kg, and EN-CLP (Chem) 2.4, 1.4, 0.42 mol/kg, respectively. The EN-CLP synthesized by an electron beam has higher capacity for the recovery of the precious metals.
Parajuli, D.; Hirota, Koichi; Seko, Noriaki
no journal, ,
Quaternary amine type derivative of lignophenol (TMA-CLP) has been prepared by electron beam irradiation followed by chemical treatment with trimethylamine. The adsorbent was tested for its adsorption behavior for a number of metal ions and found to exhibit selectivity for Au(III), Pd(II), and Pt(IV) in 0.5 to 5.0 M hydrochloric acid medium. From the adsorption isotherm study, the maximum loading capacity of TMA-CLP for Au(III), Pd(II), and Pt(IV) was evaluated as 4.3, 0.74, and 1.3 mol/kg of the dry adsorbent, respectively.
Parajuli, D.; Hirota, Koichi
no journal, ,
Hirota, Koichi; Parajuli, D.
no journal, ,
Radiation induced vinyl graft modification of natural polymer, cotton was performed by pre-irradiated with electron beam followed by mixing with glycidyl methacrylate (GMA). Cotton-graft-GMA was then modified to ethylenediamines to the epoxy ring of GMA, by simple chemical modification. Newly developed Amine-cotton derivatives were then studied for their ion exchange performances and selectivity patterns for various metals in HCl systems.
Parajuli, D.; Hirota, Koichi
no journal, ,
