Sri Sudiono

Mechanism of the Removal of AuCl-4 Ions from Aqueous Solution by Means of Peat Soil Humin

Peat soil humin, obtained after the removal of fulvic and humic acid fractions according to the recommended procedure of the International Humic Substances Society (IHSS), has the ability to remove AuCl−4 ions from aqueous solution. The removal was greatest at medium acidity, which was equivalent to pH 2.0, and it was governed by two different processes, i.e. attachment onto un-ionized –COOH groups through hydrogen bonding and reduction to Au metal by the action of the –OH group. Purification of humin through repeated immersion and shaking in a mixed solution consisting of 0.1 M HCl and 0.05 M HF led to the abrupt increase in the –COOH contents from 386 mmol/kg to 2510 mmol/kg, while the content of total –OH functional groups remained relatively constant at values slightly higher than 3000 mmol/kg. The increase in –COOH content improved the removal of AuCl−4 ions from 23 mg/g to 27 mg/g, but it was unfortunately accompanied by a diminished reduction ability to Au metal. Hence, the role of the –COOH functional group in removing AuCl−4 ions through hydrogen bonding was more significant for the purified humin, while that of the –OH group in removing AuCl−4 ions through reduction to Au metal was better for the crude (unpurified) humin.

PREPARATION, CHARACTERIZATIONS AND MODIFICATION OF Ni-Pd/NATURAL ZEOLITE CATALYSTS

Preparation, and modification of Ni-Pd/natural zeolite as well as their characterizations had been carried out. The aim of this research for the fututure is to prepare the best characters catalyst for the conversion of waste plastics fraction to gasoline fraction (C5-C12 hydrocarbons). The preparation of catalysts was performed by reacting a natural zeolite with the precursor of Ni(NO3)2. 9H2O and PdCl2 in an ammonia solution (25%). The modifications were performed by varying the rasio of Ni/Pd loaded to the zeolite, whereas the Pd was previously loaded and total metal content was 1 wt.% based on the zeolite. The characterization of catalysts included determination of acidity gravimetrically by adsorption of ammonia or pyridine vapour base method, metal content by Atomic Adsorption Spectrophotometer (AAS) and X-ray Fluoresence (XRF) and crystallinity by X-ray Diffraction (XRD). The treatment of catalysts using Etilene Diamine Tetra Acetic acid (EDTA) was performed to study the metal distribution on the outer or inner surface of the zeolite. The characterization results showed that the loading of metals to the zeolite increased its acidity and decreased its spesific surface area, however, did not defect its crystallnity. The metals loaded on the zeolite were distributed inside the pore and at outer surface of the zeolite. For all catalyst samples, the acidities determined using ammonia were higher than those of pyridine, and the acidities determined before the EDTA treatment was lower than those after the treatment. Metal contents of the zeolite before the EDTA treatment were higher than those after the treatment. The EDTA treatment enhanced the crystallinity of the sampel. The relationship between the metal rasio towards the acidity of the catalyst samples were in variation. Catalyst samples produced in this research have good characters, thus promisingly can be used for conversion process of waste plastics to gasoline fraction.