Mercaptan's Removal from Aqueous Solution using Modified Graphite-Based Adsorbent through Batch-Wise Adsorption-Regeneration

The removal of mercaptans (ethane thiol and 1-methyl, 1-propane thiol) from aqueous solution through adsorption using proprietary, partially porous, and electrically conducting graphite-based adsorbent (called Nyex 2000) was investigated. Nyex 2000 adsorbent was prepared through successive chemical, thermal, and physical treatments of Nyex 1000 adsorbent (previously developed graphite intercalation compound [GIC]-based adsorbent material) with the aim of improved adsorption capacity. The characterization of Nyex 2000 was carried out including laser size analyzer, Boehm surface titration, X-ray (energy dispersive spectroscopy [EDS]) surface elemental analysis, X-ray diffraction (XRD) analysis, N-2 adsorption, and zeta potential measurements. The adsorption of both thiols on Nyex 2000 was found to be a rapid process (more than 80% of equilibrium capacity achieved within 5 min). Nyex 2000 showed an adsorption capacity of 6 and 9mg g(-1) for the removal of ethane thiol and 1-methyl, 1-propane thiol, respectively. After adsorption, Nyex 2000 was successfully electrochemically regenerated in a batch electrochemical cell. The regeneration efficiency was found to be consistent at around 100% for five adsorption-regeneration cycles. The electrochemical parameters were as: treatment time of 40 min at a current density of 12 mA cm(-2) for a total charge passed of 240 C g(-1) at the average cell voltage of 3.5 V. The electrical energy of 120 J was found to be required for electrochemical oxidation of each mg of adsorbed mercaptan on the surface of Nyex 2000.