High efficiency removal of ibuprofen in water using activated carbon derived from Radix Angelica Dahurica residue

The exploitation and utilization of Traditional Chinese medicine have annually produced 30 million tons of waste residues including Radix Angelica Dahurica residue (RAR), which raised environmental concerns. Meantime, the non-steroidal anti-inflammatory drug of ibuprofen (IBP) is an emerging contaminant in the aquatic environment, annually producing up to 9000 tons in China. After extracting the active substance, RAR is prepared as activated carbon (AC) for the purification of IBP wastewater. Two kinds AC modified without (RAR-AC) and with phosphoric acid (M-RAR-AC) were characterized by FT-IR, TG, BET and SEM. The phosphoric acid activation contributed to the high BET surface area (564.9914 m(2) g(-1)) and large total pore volume (0.4894 cm(3) g(-1)). M-RAR-AC showed 7.7 folds (15 min) and 2.7 folds (30 min) higher extent of IBP removal compared to commercial activated carbon (C-AC). The enhancement of IBP removal with M-RAR-AC was investigated further by varying initial pollutant concentration, absorbent dosage, temperature, pH and rotating speed. Especially, temperature nearly has no effect on IBP removal by M-RAR-AC. Isotherm and kinetic studies suggested IBP was adsorbed on the heterogeneous surface in multilayer form and chemisorption played the dominant role in IBP removal. IBP removal of 93.3 +/- 0.1% and 64.2 +/- 2.8% was achieved for first and fifth cycle, respectively. The IBP removal on M-RAR-AC may be accomplished by a variety of interactions such as electrostatic attraction, pore-filling, hydrogen bonding, and pi-pi interaction. These findings provide new insights into the utilization of RAR for preparing AC and highlight the potential applications for treating industrial wastewater.