Efficient Nitrate Reduction in a Fluidized Electrochemical Reactor Promoted by Pd–Sn/AC Particles

Abstract

Pd-Sn modified activated carbon (Pd-Sn/AC) was prepared by impregnation of Pd and Sn salts onto AC followed by heat treatment. Based on scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analysis, Pd-Sn alloy was highly dispersed on the surface of AC with a atomic ratio of about 4.21. A double electrolysis cell was established and separated via a proton-exchange membrane. In the cathodic cell compartment, the as-prepared Pd-Sn/AC was used as particle electrodes where electrolytic reduction of nitrate was performed. A batch mode study showed that at an applied current of 30 mA with 7.5 g/L catalyst, over 90 % of the nitrate could be reduced in 80 min when the nitrate initial concentration was 24.6 mg/L. The electro-catalytic process of nitrate reduction could be satisfactorily described with a first-order kinetics model. With increasing applied current, the nitrate removal rate increased; whereas, the NH 4 ? concentration increased as well. The inhibition effect of coexisting anions and cations on nitrate reduction followed this order:

State-of-the-art and perspectives of the catalytic and electrocatalytic reduction of aqueous nitrates

“…The improvement of the electroreduction performance using DCC compared to SCC has been demonstrated by Ding et al [124] with different cathodic materials (GF, Cu 90 Ni 10 , and Ti); graphite achieved the best nitrate removal performance (70%). These results are consistent with the observations published by Szpyrkowicz et al [120] with the A novel reactor configuration in which catalyst particles are introduced into the cathodic chamber of a dual compartment cell was recently proposed to combine the advantages of catalytic and electrocatalytic reduction of nitrate [132,133]. As shown in Figure 13, the protons generated in the anode migrate to the cathodic chamber through the proton exchange membrane that acts as a reducing agent.…”

“…For this reason, the electroreduction of nitrates in water seems to be a more realistic alternative for the treatment of wastewater. particles [133]…”

“…The enhancement in the performance of the process is due to the presence of the coupled catalytic reduction of nitrate with the appropriate amount of in situ generated hydrogen by electrolysis as a reducing agent. In the study reported by Lan et al [133], in which Pd-Sn/AC particles were introduced in a DCC with DSA electrodes, 90% of the nitrates were converted to nitrogen gas when the initial concentration was 24.6 mg NO 3 -/l.…”

Restoring the Nitrogen Cycle by Electrochemical Reduction of Nitrate: Progress and Prospects

“…Moreover, hydrogenation catalysts can serve as fluidized particles and result in a perfect combination of electrochemical and catalytic processes, in which hydrogen produced from a water reduction reaction can be employed as a reductant for the catalytic nitrate removal. [163,169] In the reactor set up mentioned above, a high voltage (≈600 V) was applied to drive nitrate removal. [167,168,170] To reduce the operational cost, one effective strategy is to construct an electrolytic cell with a close gap between the key components.…”

“…Moreover, hydrogenation catalysts can serve as fluidized particles and result in a perfect combination of electrochemical and catalytic processes, in which hydrogen produced from a water reduction reaction can be employed as a reductant for the catalytic nitrate removal. [ 163,169 ]…”