Publications by authors named "Keisuke Nakakubo"

We previously reported that monoalkyl dithiocarbamate-modified cellulose (DMC) exhibited excellent adsorption performance for arsenite (As), cadmium (Cd), lead (Pb), gold (Au), silver (Ag), platinum (Pt), and palladium (Pd). However, its adsorption capability for As decreased by 96.4% after two weeks of storage at 40 °C under an air atmosphere.

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Numerous reports have described dithiocarbamate (DTC)-modified cellulose sorbents that can selectively separate metal ions from water. We have previously synthesized a novel sorbent modified with DTC containing N-heterocycles in the backbone for the selective removal of hazardous metal ions. The sorbent was found to partially dissolve and aggregate in solution, reducing its sorption capacity.

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The reclamation of geogenic As-contaminated excavated soils as construction additives can reduce the post-disposal impact on the ecosystem and space. Although retaining soil characteristics while reducing contaminant load is a challenging task, washing remediation with biodegradable surfactants or chelators is a promising alternative to non-biodegradable counterparts. In this study, newly synthesized biodegradable surfactants (SDG: sodium N-dodecanoyl-glycinate, SDBA: sodium N-dodecanoyl-β-alaninate, SDGBH: sodium N-dodecanoyl-α,γ-glutamyl-bis-hydroxyprolinate, SDT: sodium N-dodecanoyl-taurinate, and DCPC: N-dodecyl-3-carbamoyl-pyridinium-chloride) and biodegradable chelators (EDDS: ethylenediamine N,N'-disuccinic acid, GLDA: L-glutamate-N, N'-diacetic acid, and HIDS: 3-hydroxy-2,2'-imino disuccinic acid) are evaluated for the remediation of As-contaminated soil.

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Speciation of selenium (Se) is typically carried out using a sophisticated technique such as ICP-MS after preconcentration using an adsorbent; however, the separation and preconcentration of inorganic Se has not been realized in the solutions containing high concentrations of SO. A dithiocarbamate-modified cellulose (DMC) was used in this study for the selective extraction and preconcentration of inorganic Se in wastewater, with a portable liquid electrode plasma-optical emission spectrometry (LEP-OES) being employed for quantification. DMC was found to selectively and quantitatively adsorb selenite (Se) over a wide range of pH (1.

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Economic and ecological issues motivate the recovery of precious metals (PMs: Ag, Au, Pd, and Pt) from secondary sources. From the viewpoint of eco-friendliness and cost-effectiveness, biomass-based resins are superior to synthetic polymer-based resins for PM recovery. Herein, a detailed comparative study of bio-sorbent dithiocarbamate-modified cellulose (DMC) and synthetic polymer-based commercial resins (Q-10R, Lewatit MonoPlus TP 214, Diaion WA30, and Dowex 1X8) for PM recovery from waste resources was conducted.

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Recovery of precious metals (PMs: Au and Pt) from waste resources is of high importance due to the environmental concern and imbalance in the supply-demand ratio. A new approach has been explored for the recovery of PM using earlier developed bio-adsorbent, dithiocarbamate-modified cellulose (DMC). The adsorbent exhibits excellent adsorption efficiency (~99%) over a wide range of pH (< 1-6) and high selectivity towards Au and Pt extraction from acidic solutions ([H]: ≥ 0.

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A series of cellulose derivatives bearing dialkyl dithiocarbamate (DTC) groups were synthesized. Their ability of sorption of arsenite (As(iii)) and heavy metals and their storage stability in the solid state were investigated. Among them, DTC-modified cellulose derived from l-proline showed the highest sorption capacity for As(iii) and heavy metals to selectively remove them from aqueous media.

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We synthesized three new dithiocarbamate (DTC)-modified cellulose biomaterials (DMC-1, DMC-2, and DMC-4) to investigate their adsorption capabilities as mitigators of arsenite (As) in aqueous media. The main novelty of the adsorbents was that, among two inorganic species of arsenic, arsenite and arsenate (As), DMCs were highly selective to As in the pH range 2-7. The surface areas of the adsorbents were unified by supporting the DMCs on silica gel (designated SSDMC-1, SSDMC-2, and SSDMC-4, respectively) to investigate the effect of the length of the alkyl chains connecting cellulose and DTC groups on As adsorption.

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