Surface characterization of mesoporous biomass activated carbon modified by thermal chemical vapor deposition and adsorptive mechanism of nitrate ions in aqueous solution

Abstract

The mesoporous activated carbon derived from moso biomass was selected to be modified to efficiently and rapidly remove aqueous phase nitrate ions. The bamboo was activated by H3PO4 and pyrolyzed at 500℃, marked as BAP6. Via various steps including thermal chemical vapor deposition (CVD), 7 types of surface modified biochar were obtained. Surface characterization of all the samples was investigated by Brunauer-Emmett-Teller method, elemental analyzer, and X-ray photoelectron spectroscopy. The quaternary nitrogen (N–Q) as strong adsorptive sites was deposited successfully on the surface of BAP6 (Davg = 6.8 nm, SBET = 1024 m2/g) by CVD doping nitrogen on it. The optimal modified mesoporous activated carbon BAP-8AN20-9.5HT30-8ST30 (Davg = 4.4 nm, SBET = 995 m2/g) owned nitrate adsorption capacity of 0.46 mmol/g in nitrate concentration of 200 mg/L at solution pH 3 and surface adsorption rate of 0.47 μmol/m2. The adsorption principle was also discussed. Adsorption kinetics were examined and analyzed by the pseudo-first-order and pseudo-second-order model. All powdery samples BAP6-8AN20-9.5HT30-8ST30 and reference samples KF-8ST10-8AN20-9.5HT30-8ST30 and HP555 were fitted by second-order model well (R2 = 0.995, 0.999 and 0.999). The results showed that BAP-8AN20-9.5HT30-8ST30 was the most rapid adsorbent to arrive at equilibrium, which took only 8 min with a Qe of 0.43 mmol/g.