Preparation of nitrogen-doped porous carbon by urea–formaldehyde resin for the construction of membrane adsorption reactor to remove refractory pollutant

Considering the highly toxic by-products generation and environmental friendliness, the adsorption process is a suitable solution as the end of pipe treatment for refractory organics in coking wastewater. Nitrogen-doped micro-mesoporous carbon prepared by carbonization and KOH activation of urea-formaldehyde resin (UFCA) realized effective adsorption of quinoline, phenol and pyridine in coking wastewater. Among them, UFCA-900 has large specific surface area (SBET=1469.94 m2·g-1) and excellent adsorption properties: the adsorption removal rate of quinoline reached 98.40% about 16 min, and the maximum adsorption capacity of quinoline was 721.90 mg·g-1 at 318 K, the adsorption capacity of phenol and pyridine at 298 K were 341.59 mg·g-1 and 225.08 mg·g-1, respectively. The adsorption kinetics of UFCA-900 obeyed the pseudo-second-order model, and the adsorption process was endothermic. The membrane adsorption reactor demonstrated efficient adsorption, well separation, and negligibly irreversible membrane fouling. The adsorption mechanism included electrostatic interactions, π-π interactions and hydrogen bonds. Regeneration test proved that the removal rate of the chemically regenerated UFCA-900 was similar to the fresh adsorbent after six cycles. Taken together, a simple strategy for in-situ nitrogen-doped porous carbon has been developed and the resultant composite UFCA-900 has promising application prospect in coking wastewater treatment.