Article

Selective recovery of precious metals by persimmon waste chemically modified with dimethylamine. Bioresour Technol

Department of Applied Chemistry, Saga University, 1-Honjo, Saga 840-8502, Japan.
Bioresource Technology (Impact Factor: 4.49). 05/2009; 100(18):4083-9. DOI: 10.1016/j.biortech.2009.03.014
Source: PubMed

ABSTRACT

Persimmon waste was chemically modified with dimethylamine (DMA) to obtain a tertiary-amine-type gel, named DMA persimmon waste gel (DMA-PW). It was found to be effective for the adsorption of Au(III), Pd(II), and Pt(IV) in hydrochloric acid medium. In contrast, base metals such as Cu(II), Zn(II), Fe(III), and Ni(II) were not practically adsorbed. The formation of ion pairs of the metal chloro complex anions with the protonated adsorption gels was proposed as the main adsorption process. The gel exhibited selectivity only for precious metals with a remarkably high capacity for Au(III), i.e., 5.63 mol/kg dry gel and comparable capacities, i.e., 0.42 and 0.28 mol/kg for Pd(II) and Pt(IV), respectively. According to the kinetic and electrochemical studies, the adsorption rate of Au(III) was greatly enhanced by the chemical modification. Also, its excellent adsorption characteristics for the precious metals were confirmed by adsorption and elution tests using a column packed with the DMA-PW gel.

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Available from: Katsutoshi Inoue, May 29, 2014
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    • "The maximum adsorption capacities of these precious metals on these modified gels as well as the DMA-PW gel evaluated according to the Langmuir's equation are listed inTable 3 together with those on other adsorbents for comparison.Table 3. The maximum adsorption capacities of gold(III), platinum(IV) and palladium(II) on various adsorbents. Persimmon extract tannin (PT) powder 5.89 - - 0.1 [33] Crosslinked persimmon tannin (CPT) 7.7 - - 0.1 [33] Crosslinked persimmon waste (CPW) 4.95 - - 0.1 [35,36] Dimethylamine modified persimmon waste (DMA-PW) 5.63 0.28 0.42 0.1 [35,36] Quaternary ammonium modified persimmon tannin (QAPT) 4.16 0.52 0.84 0.1 [37] Tetraethylenepentamine-modified persimmon tannin (TEPA-PT) 5.93 1.48 1.76 0.1 [38] Glycidyltrimethyl ammonium chloride modified persimmon tannin (GTA-PT) 3.30 1.00 1.67 0.1 [39] Aminoguanidine modified persimmon tannin (AG-PT) 8.90 1.00 2.00 0.1 [40] Bisthiourea modified persimmon tannin (BTU-PT) 5.22 0.70 1.72 0.1 [41] Quaternary ammonium modified microalgal residue 1.33 2.95 0.1 [43] Crosslinked microalgal residue 3.25 0.15 0.25 0.1 [44] Crosslinked chitosan 1.6 2.1 0.01 [1] Collagen fiber immobilized bayberry tannin 0.495 0.80 pH = 5.6 [45] Lysine modified cross-linked chitosan 0.35 0.66 1.03 pH = 1 for Pt; pH = 2 for Pd, and Au [46] Glycine modified cross-linked chitosan 0.86 0.62 1.13 pH = 2 [47] PEI-modified corynebacterium glutamicum 1.66 0.1 [48] Ethylenediamine modified chitosan nanoparticle 0.87 1.30 pH = 2 [49] Thiourea-modified chitosan microsphere 0.66 1.06 pH = 2 [50] Duolite GT-73 0.58 0.26 pH = 2 [51] Polyallylamine modified Escherichia coli biomass 2.50 pH = 3 [52] Dimethylamine modified waste paper 4.60 0.90 2.10 1 [42] Among these modified persimmon tannin gels, the high adsorption capacities of TEPA-PT, GTA-PT, AG-PT and BTU-PT not only for gold(III) but also for platinum(IV) and palladium(II) are noteworthy though the concentration range of hydrochloric acid effective for the high adsorption is limited. Also for these modified persimmon tannin gels, the exceptionally high adsorption capacities for gold(III) are attributable to the combination of adsorption and reduction into metallic gold particles by the aid of polyphenolic groups of persimmon tannin, which was confirmed by the observations using optical microscope and XRD. "
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