N-doped activated carbon from used dyeing wastewater adsorbent as a metal-free catalyst for acetylene hydrochlorination

Dyeing wastewater led to the water pollution and mercury contamination originated from polyvinyl chloride (PVC) production are both environmental problems derived with industrial development. In this work, the coconut activated carbon (CAC) was used to adsorb neutral red (NR), a representative dye in dyeing wastewater. Then, the spent CAC was calcined to be N-doped metal-free catalyst to realize the resource recovery. The metalfree catalyst showed a superior catalytic performance in acetylene hydrochlorination which is the important reaction for PVC production industry. The optimal 3NR/4CAC catalyst exhibited preferable catalytic activity with C2H2 conversion of 97.9% and competitive stability in the 200 h lifetime test. A series of experimental characterizations combined with ReaxFF molecular dynamics simulations as well as density functional theory (DFT) calculations have been carried out to reveal the structural and electronic properties of the N-doped CAC catalysts, the nitrogen doping process as well as the catalytic mechanism of different N species for the acetylene hydrochlorination. This work provides a novel way for the reutilization of the waste adsorbent produced from dyeing wastewater treatment to support the sustainable development of PVC industry.