Evaluation and mechanism of ammonia nitrogen removal using sediments from a malodorous river

Abstract

Malodorous rivers are among the major environmental problems of cities in developing countries. In addition to the unpleasant smell, the sediments of such rivers can act as a sink for pollutants. The excessive amount of ammonia nitrogen (NH3−N) in rivers is the main factor that causes the malodour. Therefore, a suitable method is necessary for sediment disposition and NH3−N removal in malodorous rivers. The sediment in a malodorous river (PS) in Beijing, China was selected and modified via calcination (PS-D), Na+ doping (PS-Na) and calcination–Na+ doping (PS-DNa). The NH3−N removal efficiency using the four sediment materials was evaluated, and results indicated that the NH3−N removal efficiency using the modified sediment materials could reach over 60%. PS-DNa achieved the highest NH3−N removal efficiency (90.04%). The kinetics study showed that the pseudo-second-order model could effectively describe the sorption kinetics and that the exterior activated site had the main function of P sorption. The results of the sorption isotherms indicated that the maximum sorption capacities of PS-Na, PS-D and PS-DNa were 0.343, 0.831 and 1.113 mg g−1, respectively, and a high temperature was favourable to sorption. The calculated thermodynamic parameters suggested that sorption was a feasible or spontaneous (ΔG < 0), entropy-driven (ΔS > 0), and endothermic (ΔH > 0) reaction.

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“…The sorption isotherms were fitted by the Langmuir and Freundlich models, and the equations of the isotherm parameters are ( Sundaram et al, 2008 ; Chen et al, 2018 ): …”

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“…Ammonia-nitrogen is a toxic groundwater pollutant, and its impact is widespread, as its excessive quantity causes malodor in river water that can lead to eutrophication, weakening of the self-depuration capability of water and threats to public health. Heavily polluted waters contain an ammonia-nitrogen level of >15 mg/L, and a minor pollution level is considered to be 8-15 mg/L [205,206]). The photogenerated electrons from the TiO 2 conduction band can transfer to the g-C 3 N 4 valence band by the Z-scheme mechanism.…”

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