Isotherm and Thermodynamics Adsorption of Au(III) Ion by Mangosteen Rind (<i>Garcinia mangostana </i>L.)

Abstract

The mangosteen rind has O‒H, C=C aromatics, and ethers functional groups, its performance for Au adsorption become an interesting research to both environment and economic purpose. In this study, waste mangosteen rind as eco-friendly adsorbent had been used for Au(III) adsorption. Initiate by maceration for pre-treatment of biosorbent, the mangosteen rind’s perfomance was revealed. Crystalline structure of mangosteen rind was analyzed by X-ray diffraction, while after interaction with Au(III) ions gave three characteristic peaks indicated Au(III) reduction into Au(0). The adsorption followed isotherm Langmuir model and afforded spontaneous reaction that evidenced by enhancement of ∆G° by increasing of temperature (–1.7 at 30 °C to –8.4 at 60 °C). The value of ∆H° and ∆S° were 71.1 kJ mol–1 and 238.5 J mol–1 K–1, respectively.

Study of Mangosteen Peel (<i>Garcinia mangostana</i> L.) Waste Capability to Recover Au(III) and Ag(I) in Aqueous Solution

“…This proves that Au(III) ions were adsorbed and reduced to Au(0) metals on the surface of MPW. MPW has an irregular surface structure that was proven from stereomicroscope characterization on the previous research [24]. The presence of Au was not visible clearly due to the small amount of Au.…”

“…Both dried mangosteen peel and MPW had two main functional groups at 3400 cm -1 and 1600 cm -1 , which correspond to the O-H and C=C aromatic stretching vibrations, respectively [24][25]. The absorption peak at 1280 cm -1 , associated with C-O stretching vibration [24], appeared to be deteriorated from fresh mangosteen peel after being treated. The extraction process removes organic and water-soluble compounds in fresh mangosteen peel.…”

“…The adsorbent preparation was begun by soxhlet extraction and followed by the maceration method under room temperature condition. The preparation method was a modification from our previous research [24]. Soxhlet extraction was performed by using methanol with a mass-to-volume ratio of 1 to 10.…”