Adsorptive Recovery of Au(III) from Aqueous Solution Using Modified Bagasse Biosorbent

Abstract

The recovery of Au(III) from aqueous chloride solutions onto modified bagasse biosorbent was investigated.The parameters for biosorbent preparation as well as gold recovery were studied in detail.It was found that 99.8 % of sugarcane bagasse could be modified as biosorbent having better physical properties for adsorption.The solution pH, sorbent dosage, initial Au(III) concentration and temperature were the studied variables that affect the efficiency of gold recovery as well as adsorption behavior.The efficiency of 99% for Au(III) recovery was obtained under the following conditions: 25 mg sorbent, 25 mL of 25-500 mg/L Au(III), pH 2, 150 rpm, 4 h and 25 o C. The 99% of gold recovery still obtained in only 1 h or less with the increasing of dosage or temperature.The gold adsorption in this study was best fitted with Langmuir isotherm model and the maximum capacity for gold loading was determined to be 1497.5 mg/g or 7.6 mmol/g.The adsorption kinetics was also evaluated in terms of the pseudo first-order and pseudo second-order kinetic models.The high activation energy of 45.8 kJ/mol was estimated which represents a chemisorption process.The adsorption mechanism in this study is clarified to be the oxidation of hydroxyl to carbonyl in biosorbent and reduction of trivalent gold ions to metallic gold simultaneously on biosorbent surface.The results from ORP measurement, FT-IR and EDS spectra including SEM images were the supported evidence for this adsorption mechanism.The modified bagasse biosorbent therefore has potential in gold recovery process.