Factors controlling adsorption of recalcitrant organic contaminant from bio-treated coking wastewater using lignite activated coke and coal tar-derived activated carbon

BACKGROUNDLow-cost coal-based carbonaceous material has attracted special attention for removal of organics from industrial wastewaters. In this study, coal tar-derived activated carbon (AC1) and lignite activated coke (AC2) were employed to identify the fundamental factors that facilitate the selection of suitable adsorbents for removing recalcitrant organic contaminant (ROC) from bio-treated coking wastewater (BTCW). RESULTSResults show that AC2 exhibited superior ROC adsorption efficiency (57.9%), which was apparently higher than that of AC1 (45.2%), in spite of its lower specific surface area (238.05 m(2) g(-1)) and pore volume (0.21 cm(3) g(-1)). FTIR and XPS characterization indicated that AC2 possessed a distinctive configuration of functional groups, of which the basic oxygenic groups (60%) provided more hydrophobic adsorption sites for ROC. 3D-EEM spectra suggested more aromatics and fluorescent materials were removed by AC2 compared with AC1. GC-MS further confirmed that AC2 had stronger affinity with the ROC in BTCW, especially for PAHs and heterocyclic compounds. CONCLUSIONSurface chemistry is vital to the adsorption of ROC from coking wastewater, of which basic oxygenic functional groups have specific interactions with PAHs and heterocyclic compounds. The mechanism that best explains ROC adsorption is - dispersion between carbon materials and the pollutants, as well as the hydrogen-bonding interactions. This study provides an encouraging and practical guide to ROC adsorption from BTCW in future operations. (c) 2017 Society of Chemical Industry