The application of activated coke (AC) in scavenging heavy metals in wastewater has attracted great interest due to its high specific surface area and low cost. In this study, a simple method via esterification with mercapto-acetic acid was developed for the functionalization of activated coke to remove mercury from solution. Results showed that thiol groups were successfully anchored onto the surface of AC. The adsorption equilibrium time was found to be shortened dramatically from 8 h using AC to 15 min using thiol-functionalized AC (SH-AC). The maximum Langmuir adsorption capacity on SH-AC was 694.9 mg g(-1), more than twice as much as that on AC. Additionally SH-AC proved its ability to operate over a wider pH range and in the coexistence of other anion species. Higher selectivity was also observed for Hg over multiple metal ions. Zeta potentials, FTIR, and XPS were applied to confirm that the improvement in mercury adsorption was closely related to the anchored thiol groups. The adsorbent also showed high reusability due to its high adsorption capacity after several adsorption-desorption cycles. It can therefore reasonably promise the potential for a more selective and effective but less expensive adsorbent for the treatment of mercury effluent. (C) 2013 Elsevier B.V. All rights reserved.