Synthesis and Zn(II) modification of hierarchical porous carbon materials from petroleum pitch for effective adsorption of organic dyes.

The discovery of efficient carbonaceous adsorbents for the removal of organic dyes is a meaningful subject. In this study, hierarchical porous carbon materials (HPCMs) were synthesized from petroleum pitch through template strategy coupled with in-situ chemical activation, and the optimal HPCM was further modified by Zn(II) to get modified HPCM (MHPCM). Their properties and structures were characterized, and their adsorption performances for two typical dyes, methylene blue (MB) and direct black 38 (DB 38), were examined. The as-prepared HPCMs and MHPCM exhibit high specific surface area with hierarchical pore structure, abundant oxygen-containing group, and distinct layered structure. As an adsorbent for dye removals, the MHPCM shows excellent performance with its Langmuir saturated adsorption capacity being 1585.7 and 438.6 mg/g for MB and DB 38, respectively. This is mainly due to the large surface area and hierarchical pore structure of HPCMs, as well as the modification effect of Zn(II). This work provides an efficient strategy for the synthesis of carbonaceous adsorbents used in the adsorptive removal of different molecular size dyes, as well as a new approach for the valuable use of low-cost petroleum pitch.