Kanjana Khunathai

Adsorptive Recovery of Palladium(II) and Platinum(IV) on the Chemically Modified-Microalgal Residue

A biomass waste of microalgae was chemically modified by immobilizing the functional group of polyethyleneimine to prepare a new type of adsorbent. The adsorption test revealed that this adsorbent exhibited remarkably high selectivity for Pd(II) and Pt(IV) over base metal ions in HCl solution. From the adsorption isotherm, its maximum adsorption capacity for Pd(II) and Pt(IV) was evaluated as 2.0 and 0.8 mmol/g, respectively. This adsorbent also exhibited high affinity and selectivity for Pd(II) and Pt(IV) even in the presence of high concentrations of base metals in actual leach liquor. Present address for Kanjana Khunathai, Research Laboratories, DENSO CORPORATION, 500-1 Minamiyama, Komenoki, Nisshin, Aichi 470-0111, Japan

Adsorption Behavior of Quaternary Amine Types of Lignophenol Compounds for Some Precious Metals

Two kinds of quaternary amine type lignophenol derivatives were prepared and tested for the adsorption behavior of Au(III), Pd(II), Pt(IV), Cu(II), Fe(III), and Zn(II) in hydrochloric acid medium. Both the derivatives were found to exhibit excellent selectivity for precious metals with negligible adsorption for other metal ions. The adsorption isotherm study established the Langmuir type adsorption model, and from the respective adsorption isotherms, the maximum loading capacities for Au(III), Pd(II), and Pt(IV) were evaluated. Ionic interaction between the positive moiety of quaternary amine functional groups and the anionic chloride complexes formed by the precious metal ions in acidic chloride media was concluded as the main adsorption mechanism.

Dithiooxamide-Immobilized Microalgal Residue for the Selective Recovery of Pd(II) and Pt(IV)

Microalgal residue was chemically modified by immobilizing a functional group of dithiooxamide to prepare a novel type of adsorbent. This adsorbent exhibited high adsorption affinity and selectivity for Pd(II) and Pt(IV) whereas the adsorption of coexisting base metal ions was negligible. From the adsorption isotherms, this adsorbent was found to exhibit remarkably high adsorption capacity. The thermodynamic parameters indicated that the adsorption is governed by an endothermic reaction. The effective separation of Pd(II) and Pt(IV) from Cu(II) was confirmed also by a dynamic adsorption test. The effectiveness of elution of adsorbed Pd(II) and Pt(IV) was 85% and 96%, respectively.

Effective recovery of some precious metals by using alternative quaternary amine types of anion-exchangers prepared from biofuel-extracted microalgal residues

Trimethylamine- and triethylamine-immobilized adsorption gels were prepared from the oil-extracted microalgal residues. The FT/IR spectra and elemental analysis confirmed the immobilization of quaternary amine functional groups on the microalgal residue. Their adsorption behaviors for various metal ions in a hydrochloric acid solution were studied. Both adsorbents exhibited high selectivity for Pd(II) and Pt(IV) while showing no significant affinity for base metal ions. From the adsorption isotherms, the adsorption capacities for Pd(II) and Pt(IV) in 0.1 M HCl was found to be 2.95 and 1.33 mmol g−1 for trimethylamine, and 2.57 and 1.54 mmol g−1 for triethylamine type gels, respectively. These adsorbents are promising for the selective separation and recovery of Pd(II) and Pt(IV) and directly provide the sustainable means for the material development and benign environment.

Recovery of Silver Using Adsorption Gels Prepared from Microalgal Residue Immobilized with Functional Groups Containing Sulfur or Nitrogen

Although biodiesel oil extracted from microalgae attracts much attention as one of the most promising green energies, its high production cost is a big problem, impeding its extensive use. In order to lower the production cost, the effective use of microalgal residue after extracting biofuel was investigated as a feed material of functional materials. In the present work, a new adsorbent for silver(I) was prepared by immobilizing functional groups of polyethylene-polyamine or dithiooxamide, which exhibita high affinity for soft Lewis acids such as silver(I) ions. Their adsorption behaviors for silver(I) were investigated from aqueous nitrate and acidothiourea media. The effects of the concentrations of nitrate and thiourea, as well as of sulfuric acid, were qualitatively interpreted. From the study of adsorption isotherms on these gels, they were found to exhibita higher adsorption capacity than the majority of those reported to date.